makarova nesmejanov-organic compounds of mercury

Series: Methods of Elemento-Organic

Chemistry

General Editors

A. N. NESMEYANOV and K. A. KOCHESHKOV

VOLUME 4

c m

1967 NORTH-HOLLAND PUBLISHING COMPANY - AMSTERDAM

The Organic Compounds of

Mercury

L. G. M A K A R O V A and A. N. NESMEYANOV Karpov Institute of Physical Chemistry,

Moscow

Translated from the Russian by

SCRIPTA TECHNICA, LTD

a ® :



Library of Congress Catalog Card Number: 67-29769

Originally published as

METODY ELEMENTO-ORGANICHESKOY KHIMII (RTUT')

Nauka Press, Moscow, 1965

No part of this book may be reproduced in any form by print, photoprint,

microfilm or any other means without written permission from the publisher

Printed in The Netherlands

PUBLISHER'S ACKNOWLEDGEMENT

We feel indebted towards Pro fessor A. N. Nesmeyanov and Professor K. A. Kocheshkov, the Editors-in-Chief of this series of books on the Methods of Elemento-Organic Chemistry, who, together with their co-authors, have been so kindly prepared to update and, where necessary, rev ise the original Russian texts for this English edition.

Foreword

This book appears as one of a series of monographs entitled 'Methods of Elemento-Organic Chemistry' under the joint editor-ship of A. N. Nesmeyanov and K. A. Kocheshkov. The series as a whole will be devoted to methods of synthesis, transformation, and the synthetic uses of elemento-organic compounds. Other mono-graphs in this series, by S. T. Iof feand A. N. Nesmeyanov (Mg, Be, Ca, Sr, Ba), A. N. Nesmeyanov andR. A. Sokolik (B, Al, Ga, In, T l ) and N. I. Sheverdina and K. A. Kocheshkov (Zn, Cd) were published between 1963 and 1964. This volume, devoted to the organic com-pounds of mercury, is based on the monograph 'Synthetic Methods in the Field of Organometallic Compounds of Mercury' by L. G. Makarova and A. N. Nesmeyanov, which was published in 1945. In the following twenty years the chemistry of organometallic com-pounds developed very rapidly, which meant that an enormous vol-ume of data had to be sorted, and that the size of the book had to be more than doubled, preserving at the same time its highly con-densed treatment of the subject. The book makes exhaustive re fer -ences to the literature dealing with methods of synthesis involving the organic compounds of mercury up till 1 January 1964 and in-cludes the more important work carried out in 1964 and early 1965.

In compiling this volume, material has been drawn from the following monographs: F. C. Whitmore, Organic compounds of mercury, Chemical Catalogue

Company, New York (1921). J. Chatt, Chem. Rev., 48, 7 (1951). H. Zeiss, Organometallic chemistry, Rheinhold, New York (1960). E. G. Rochow,D. T. HurdandR. N. Lewis, The chemistry of organo-

metallic compounds, John Wiley, New York (1957). E. Krause and A. Grosse, Die chemie der Metalloorganischen

Verbindugen, Bontraeger, Berlin (1937). Newton Friend, A textbook of inorganic chemistry, Vol XI; A. E.

Goddard and D. Goddard, Organometallic compounds, Griffen, London, p. 1 (1928).

J. Schmidt, Organometallverbindungen, Th. II, Wissenschaftliche Verlaggesellschaft, Stuttgart (1934).

Traite de chimie organique (under the Editorship of V. Grignard,

vi i i FOREWORD

G. Dupont and E. Locquin), Masson et Cie., Paris (1937). J. Houben and V. Weil, Die Methoden der organischen Chemie,

Vol. IV, Verlag G. Thieme, Leipzig (W. Schlenk, Organometal-verbindungen) (1924).

E. Abderhalden, Handbuch der biologischen Arbeitsmethoden, Abt. I, Teil 2, 2 Halfte, Heft 4 (E. Klarmann-Bloomfield, Darstellung metallorganischer Verbindungen), Urban and Schwarzenburg, Berlin and Vienna (1929).

R. Garzuly, Organometalle, Sammlung chemischer und Chemische-technischer Vortrage, F. Enke, Stuttgart (1927).

G. E. Coates, Organometallic compounds, Methuen, London (1956). G. E„ Coates, Organometallic compounds, Methuen, London (Second

edition, 1960); Metal-organic compounds, 131stNational Meeting, American Chemical Society, Advances in Chemistry Series, Vol. 23, Washington (1959).

Contents

Foreword v

Introduction 1

Chapter 1 Reactions of Metallic Mercuryand Mercury Salts with RHal 11

Chapter 2 Synthesis of Organomercury Compounds with Grignard Reagents and Organolithium Deriva-tives 16

a) Preparation of Organomercury Halides 19 b) Preparation of Diorganomercury Compounds 24 c) Preparation of Organomercury Compounds by Using Or-

ganolithiums 32

Chapter 3 Preparation of Organomercury Compounds from the Organic Compounds of the Remaining Light Metals 40

a) Formation of the Organomercury Compounds from the Or-ganic Derivatives of Sodium and Silver 40

b) Preparation of Organomercury Compounds from the Or-ganic Derivatives of Zinc 41

c) Preparation of Organomercury Compounds from the Or-ganic Derivatives of Aluminum 42

Chapter 4 Synthesis of Organomercury Compounds with the Aid of Sodium, Lithium, Potassium and Cad-mium Amalgams 45

Chapter 5 Introduction of Mercury in Place of a Hydrogen Atom (Mercuration) 57

a) Mercuration of Aliphatic and Alicyclic Structures 60 b) Mercuration of Aromatic Hydrocarbons 71 c) Mercuration of Aromatic Hydroxy Compounds 81

ix

X CONTENTS

d) Mercuration of Thiophenol Derivatives 93 e) Mercuration of Aromatic Amines 94 f) Mercuration of Aromatic Ketones 104 g) Mercuration of the Aromatic Carboxylic, Sulfonic and Ar -

sonic Acids and Their Derivatives 105 h) Mercuration of Heterocyclic Compounds 109 i) Mercuration of Metallocenes 120

Chapter 6 Addition of Mercury Salts to Unsaturated Com-pounds and Cyclopropane Derivatives 142

a) Introduction 142 b) Addition of Mercuric Salts to Double Bonds 160 c) Addition of Mercuric Salts to Carbon Monoxide 202 d) Addition of Mercuric Salts to Triple Bonds 203 e) Addition of Mercuric Salts to Cyclopropane Derivatives 211

Chapter 7 Synthesis of Organomercury Compounds by the Diazo Method 228

a) Preparation of Arylmercury Halides 230 b) Preparation of Diarylmercuries 235 c) Synthesis of Organomercury Derivatives with the Aid of

Aliphatic Diazo Compounds 238 d) Synthesis of Organomercury Compounds by the Action of

Arylhydrazines on Mercuric Salts 239 e) Synthesis of Organomercury Compounds with the Aid of

Hydrazones 240

Chapter 8 Synthesis of Organomercury Derivatives via Halogenonium Compounds 246

Chapter 9 Synthesis of Organomercury Compounds by the Substitution of Mercury for Acid Groups, Heavy Metals and Some Metalloids in Organic Com-pounds 249

a) Substitution of Mercury for the Boric Acid Group and for Boron in Other Organoboron Compounds 249

b) Substitution of Mercury for the SO2H Group 254 c) Substitution of Mercury for the Iodoxy Group 257 d) Substitution of Mercury for the Carboxyl Group 259 e) Substitution of Mercury for HeavyMetals and Some Metal-

loids 264

Chapter 10 Synthesis of Organomercury Compounds by the Action of Free Radicals (from Peroxides and Other Sources) on the Mercury Salts of Carbox-ylic and Other Acids and on Metallic Mercury 276

CONTENTS xi

a) Decomposition of Peroxides in the Presence of Mercury Salts 277

b) Decomposition of Mercury Salts Initiated by Radicals Generated by Irradiation with Ultra-violet 280

c) Decompositions of Mercury Salts Initiated by Radicals formed by Other Sources 281

d) Decompositions of Peroxides in the Presence of Metallic Mercury 281

Chapter 11 Preparation of Organomercury Compounds by Electrolysis 285

Chapter 12 Methods of Synthesis of Fully Substituted Orga-nomercury Compounds RHgR 289

a) Synthesis of RHgR' through Organomagnesiums 289 b) Synthesis of RHgR' by Decarboxylation of RCOOHgR' 292 c) Synthesis of RHgAr' by the Arylation of RHgOH with Aro-

matic Compounds of Tin, Antimony(III) and Boron 292 d) Synthesis of RHgR' by the Action of Diazomethane on

RHgCl 294 e) Synthesis of RHgR' with the Aid of Dihalogenocarbenes 295 f) Synthesis of RHgR' by "Cosymmetrization" of RHgXand

R'HgX 296 g) Synthesis of RHgR' by the Action of RHgX (and R2Hg) on

Compounds Containing Mobile Hydrogen 296 h) Synthesis of RHgR' by Rearrangement of Radicals in Or-

ganomercury Compounds 298

Chapter 13 Symmetrization of Organomercury Compounds and the Reverse Reaction 302

a) Symmetrizations of Organomercury Compounds 308 b) Reaction Reverse to Symmetrization 328

Chapter 14 Reactions of Organomereury Compounds 337

a) The Action of Oxygen 337 b) The Action of Acids 338 c) The Action of Alkalis 348 d) The Action of Hydrogen Sulfide and Alkali Metal Sulfides 349 e) The Action of Certain Oxidizing Agents, in Particular

Mercuric Salts 350 f) The Action of Metal Carbonyls 351 g) The Action of Halogens 351 h) Reactions with Halides and Other Salts of Elements and

Also with their Alkyl (Aryl) Halides and Hydrides 359 i) Reactions of Organomercury Compounds with Organic

Halides 375

xii CONTENTS

j ) The Action of Reducing Agents on Organomercury Com-pounds, in Particular the Reaction with Metals 381

k) Reactions with Nitrogen Oxides 401 1) Reactions with Ketones 402 m) Reactions of Organomercury Compounds with the Grig-

nard Reagents and with the Organometallic Derivatives of Lithium, Sodium, Zinc, Aluminum and Other Metals 402

n) Isotope Exchange of Organomercury Compounds with Ra-diomercury and Compounds Containing Radiomercury 405

o) Pyrolysis of Organomercury Compounds 409 p) Photochemical Reactions of Organomercury Compounds 411 q) Cis-trans Transformationsof Unsaturated Organomercury

Compounds 416 r) Anion Exchange in Organomereury Salts 417

Chapter 15 Changes in the Organic Moietyin Organomercury Compounds 456

Chapter 16 Synthesis and Reactions of Compounds in which the Mercury is not Joined to the Organic Residue through Carbon 463

a) Compounds with an O-Hg Bond 464 b) Compounds with an S-Hg Bond 468 c) Compounds with an Se-Hg Bond 481 d) Compounds with a Ge-Hg Bond 482 e) Compounds with Si-Hg and Ge-Hg Bonds 483 f) Compounds with an N-Hg Bond 484 g) Compounds with a P-Hg Bond 492

Chapter 17 Analysis of Organomercury Compounds 506

a) Qualitative Determination of Mercury in Organomercury Compounds 506

b) Quantitative Analysis of Organomercury Compounds 506

Author Index 516

Subject Index 519

Introduction

The organic derivatives of mercury are among the most stable true organometallic compounds of the transition metals, i.e. com-pounds in which the metal is bonded directly to the carbon, second only to the compounds of arsenic and, possibly, pentavalent anti-mony. Although the stability of various organomercury derivatives fluctuates over a wide range, they are particularly noted for their inertness to oxygen and oxidizing agents, water, and, to a certain degree, to weak acids. Moreover, they do not react with most o r -ganic compounds containing oxygen and are fairly inert to alkyl halides. These properties are in sharp contrast to the organo-metallic compounds of sodium, lithium, magnesium, zinc, aluminum, and so on. The use of organomercury compounds as synthetic agents is therefore limited and does not compare, for example, with the use of Grignard reagents or organolithiums. The organometallic com-pounds of mercury enter into two very important types of reaction.

(1) Exchanges with halides of metals and non-metals, resulting in a wide range of organometallic andorgano-elemental compounds. For example, this method was used to obtain, for the f irst time, aryldichloroarsines and diarylchloroarsines, and aryldichloro-and dialkylchlorophosphines. This method has proved to be one of the simplest ways of synthesizing iodonium salts, etc.

(2) Replacement of the mercury in organomercury compounds under the action of free metals, resulting in organometallic com-pounds of the latter. This method was found to be useful in the synthesis of organometallic compounds of certain metals (sodium, aluminum, etc.) and is used to this day.

The field of application of the organometallic compounds of mercury is thus organometallic synthesis. Whereas reaction (2) above is specific to the organomercury compounds, in reaction (1) organomagnesium compounds are often preferred on account of their remarkable reactivity; the advantages are as follows.

(a) Organomagnesium compounds frequently react with halides with respect to which the organomercury compounds are inert.

(b) In view of the ease of their preparation and non-toxicity, the organometallic compounds of magnesium are convenient and safe to handle. However, Grignard reagents cannot always be substituted

References see p. 121 1

2 ORGANOMERCURY COMPOUNDS

for organomercury compounds, since (i) they may reduce the halides, for example, ICI3 or C6H5IC^, SbCl5; (ii) the ether required as a solvent for the Grignard reagent often complexes with the resulting organometallic compounds; (ii i ) the use of an organomercury com-pound allows the use of a much wider range of radicals, whereas Grignard reagents are limited to alkyl, some alkenyl, aralkyl and aryl radicals, and, less frequently, heterocyclic radicals which do not contain functional groups, with the exception of the few that are stable to the action of magnesium or organomagnesiumcompounds.

A reaction similar to (ii) above is the transfer of radicals f rom the mercury atom to reducing agents such as SnCl2 or Gel2; this also leads to the synthesis of organometallic compounds but is probably still a long way f rom being satisfactorily developed.

The above-mentioned passivity and poor reactivity of the organic compounds of mercury are the reason for the enormous variety of these compounds. Mercury combines with a wide range of organic molecules and is compatible with almost all functional groups enter-ing into the structure of the radicals connected with it. Although there are only three basic types of organomercury compounds, the fully symmetric F^Hg, the non-symmetric RHgR' and the mixed (organomercury salts) RHgX (with reference to the existence of mercurous organic compounds, see Chapter 11), great variety is obtained owing to the great diversity of the radicals. The residue R may be saturated or unsaturated, alicyclic, aromatic, or hetero-cyclic, and, as indicated above, it may contain almost any atomic group. In the initial organic molecule RH, one or more hydrogen atoms linked with carbon may be replaced by mercury; in the l imit-ing case of complete mercuration, the products are the mercarbides.

The same stability of the organometallic compounds of mercury is the reason for their ease of formation and for the variety of methods available for introducing mercury into organic molecules, which in turn allows one to arr ive at almost any combination in the resulting organomercury derivative.

The methods of synthesizing organomercury compounds are listed below.

(1) The method having the widest application is mercuration, i.e. substitution of hydrogen by mercury under the action of mercuric salts:

RH + HgXa —> RHgX + HX

In the aliphatic ser ies, this method is applicable mainly for com-pounds containing an active hydrogen, whereas in the aromatic and heterocyclic ser ies its f ield of application is virtually unlimited. A disadvantage of this method is the simultaneous formation of a mix-ture of isomers and the frequent contamination of the product by mercurated compounds (Chapter 5).

(2) Interaction between organometallic compounds of magnesium

INTRODUCTION 3

(and lithium) and mercuric halides. By this means are obtained, with good yields, such products as fully substituted aliphatic, aromatic, and some heterocyclic compounds of mercury:

2RMgX + HgX2 RHgR + 2MgX,

2RLi + H g X 2 - R 2 H g + 2 L i X

as well as organomercury salts

RMgX + HgX2 - RHgX -4- MgX2

R L i + H g X 2 - R H g X + LiX

This is the most convenient laboratory method for the preparation of aliphatic organomercuries with simple radicals such as methyl homologs (Chapter 2).

(3) Synthesis via the organic compounds of other light metals, such as the already-established method of synthesis through the organic derivatives of zinc and the apparently promising method of synthesis through organoaluminums (Chapter 3).

(4) Introduction of mercury in place of acid residues in carboxylic, arylboronic, and sulfinic acids, and also the replacement of IO2 in iodine compounds and of atoms of heavy metals in their organic com-pounds. These reactions result in individual organomercury com-pounds RHgX (and R2Hgintheeaseofthe carboxylic and arylboronic acids) of the aromatic series, and in the case of carboxylic, boric and sulfinic acids both of the aromatic and aliphatic series. The ranges of application of these methods will be described in Chapter 9.

(5) A new method of synthesis, generally of the aliphatic but also some alicyclic and aromatic compounds of mercury, is the peroxide-initiated decomposition of mercuric salts of carboxylic acids

(RCOO)2Hg + (R1COO)2 R'HgOOCR + CO2

This method is applicable for the synthesis of organomercury com-pounds that do not contain substituents capable of reacting with the peroxides or of inhibiting chain reactions (Chapter 10).

(6) The diazo method of synthesizing aromatic organomercury compounds

ArN2X • HgX2 + 2Cu -> ArHgX + N2 + 2CuX

2ArN2X -HgX 2 4- 6Cu + 6riNH3 - Ar2Hg + 2N2 + 6CuX -nNH3 + Hg

has proved to be the most suitable and universal method for aromatic Ar2Hg and ArHgX. The method has none of the limitations inherent in Methods 2, 3, 5 and 8, and partly 4 (Chapter 7).

(7) Synthesis of organomercuries through iodonium compounds. This is analogous to the diazo method but has no practical signifi-cance (Chapter 8).

References see p. 6


(8) Action of sodium amalgams on organic halides (and dialkyl sulfates):

2RX + Na2Hg - » R2Hg + 2NaX

This is the oldest of the methods still used (through rarely) for obtaining fully-substituted mercury compounds, and has a fairly wide applicability both in aliphatic and in aromatic series. The method is limited to compounds that do not contain substituents capable of reacting with sodium amalgams (Chapter 4).

(9) Addition of mercury salts to double and triple bonds, widely applicable among olefins, acetylenes and all kinds of their deriva-tives. This procedure leads to the unusual and interesting field of adducts, quasicomplexes, which cannot be obtained in any other way; organomercury salts /3-substituted by Hal, OH, OR, and so on (Chapter 6):

R1R11C = CR 1 1 1 R i v + H g X 2 + R O H R 1 R 1 1 C ( O R ) - C ( H g X ) R 1 1 1 R l v + HX

HC=CH + HgCl2 ClHC=CHHgCl

(10) Opening of three-membered rings with mercury salts, r e -sulting in y-substituted organomercury salts (Chapter 6).

(11) Interaction of alkyl halides with metallic mercury

RX + H g - * RHgX

(where X = I and in some cases also Br). This method was used in the preparation of perfluoroalkyl compounds of mercury and esters of a-bromomercuricarboxylic acids (Chapter 1).

(12) Electrolytic preparation of fully substituted organomer-curies: Route (a)

2RR'C0 + Hg + 6H (RR1CH)2Hg + 2H20

Route (b)

NaMe111Ri + Hg R2Hg

Route (a) gives compounds R2Hg with secondary radicals and Route (b) allows synthesis of the simpler lower saturated organomercury compounds (Chapter 2). Both of these methods have a limited ap-plication.

The transition from compounds of the type RHgX to compounds R2Hg is performed by the method of symmetrization (see Chap-ter 13); the reverse transformation can be accomplished (Chapter 13) by interaction of the R2Hg with mercuric salts in accordance with

R2Hg + HgX2 2RHgX

INTRODUCTION 5

Of the various methods of synthesis of organomercury compounds, Methods 1, 2 and 9, and to some extent 4, are used to prepare com-pounds RHgR' (see Chapter 12).

Chapter 15 provides a brief review of the methods of preparation and of certain reactions of compounds in which the mercury is joined to the organic residue not through carbon but through a heteroatom Z: RZHgX Or(R7^1Zn )2Hg,where Z = O.S.Se.N, Ge and Si. A brief review of products of the replacement of hydrogen by mercury in dialkyl phosphonates is also provided.

Since organomercury derivatives are fully stable to air and mois-ture and are in most cases solid substances that can be readily crys-tallized from organic solvents (more rarely distillablfe liquids), they are isolated, purified and identified by the usual methods of organic chemistry.

Very many (though far from all) organomercuries are highly toxic. In this respect, danger arises only with the volatile compounds such as dimethylmercury and its homologs, diallylmercury and alkyl-mercury salts. Every precaution must be taken during work with these compounds, carrying out all operations in well-ventilated fume cupboards, ensuring full degassing of all apparatus and de-stroying residues with solutions of bromine or chlorine in CCI4 or CHCl3, or with aqua regia. Work with the aromatic or heterocyclic compounds, or with aliphatic derivatives containing functional groups in the organic radical, is less hazardous, but here too one should bear in mind the volatility of compounds such as diphenylmercury at higher temperatures. Care must always be taken to avoid spray-ing or spilling. Certain organomercury derivatives, such as ClCH2

HgC 1, CH3O2CHgX, ClCH=CHHgCl and diphenylmercury, irritate the skin and give rise to burns.

Many studies have been made of the physical properties of the simpler organomercuries, but these do not fall within the scope of this book and the reader is referred to the original literature.

Below is given a list of references dealing with refractometry and densities [1-9], ultra-violet absorption spectra [10-25], in-fra-red spectra [19a, 23, 25-42], Raman spectroscopy [29-49], microwave spectroscopy [41, 50-52], EPR [53-55], NMR [25, 42, 56-62], mass-spectra [63-68], X-ray analysis [69-87b], magneto-chemical investigations [88-92], measurements of dielectric con-stants and dipole moments [5, 32, 89-108], electrical conductivity [109-114], polarography (see Chapter 17), determinations of the parachor [115, 116], vapor pressures of the lower alkyl compounds [3, 101, 117-121], electron diffraction studies of molecular struc-ture [122, 123], measurements of heats of combustion, heats of formation, heat capacities and free energies [3, 22, 116, 121, 124-136] and the latent heats of sublimation [117, 137].

In addition, investigations of some physical properties of organo-mercury compounds are in many instances quoted with the corres-ponding organomercury in the original literature.

References see p. 6


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chem. Phys., 30, 1422 (1959). 62. H. S. Gutowsky and G. E. Pake, ibid., 18, 162 (1950). 63. B. G. Gowenlock, R. M. Haynes and J. R. Mayer, Trans.

Faraday Soc., 58, 1905 (1962). 64. V. H. Dibeler and F. L . Mohler, J. Res. natn. Bur. Stand.,

47, 337 (1951). 65. V. H. Dibeler, ibid., 49, 235 (1952). 66. C. K. Ingold and F. P. Lossing, J. chem. Physoj 21, 368, 1135

(1953). 67. B. C. Hobrock and R. W. Kiser, J. phys. Chem. Ithaca, 66,

155 (1962). 68. S. S. Dubov, F. N. Chelobov andR. N. Sterlin, Zh. Vses. khim.

Obshch., 7, 585 (1962). 69. G. Giacomello, Int. Congr. pure appl. Chem., 2, 99 (1947);

Chem. Abstr., 45, 5019 (1951). 70. E. R. Howells1D. C.Phillips and D.Rogers, Acta Crystallogr.,

3, 310 (1950). 71. A. I. Kitaigorodskii, Izv. Akad.NaukSSSR1Otdel.khim. Nauk.,

259 (1947). 72. A. I. Kitaigorodskii and D. Grdenic, ibid., 262 (1948). 73. D. Grdenic and A. I. Kitaigorodskii, Zh. f iz. Khim., 23, 1161

(1949). 74. A. I. Kitaigorodskii and Yu. T . Struchkov, Izv. Akad. Nauk

SSSR, Ser. Fiz., 15, 147 (1951). 75. A. I. Kitaigorodskii, Dokl. Akad. Nauk SSSR, 93, 675 (1953). 76. J. Maly and L . Kuca, Chemicke' Listy, 47, 1575 (1953). 77. H. J. Emeleus, Proc. chem. Soc., 231 (1958). 78. W. L. Baun, Analyt. Chem., 33, 308 (1959). 79. D. Grdenic, Ark. Kemi, 22, 14 (1950). 80. D. Grdenic, Acta Crystallogr., 5, 367 (1952). 81. D. Grdenic, Ber. dt„ chem. Ges., 92, 231, (1959). 82. G. F. Wright and A. G. Brook, ActaCrystallogr., 4, 50 (1951). 83. M. J. Abercrombie, V. A. Rodgman, K .R . Bharucha and G. F.

Wright, Can. J. Chem., 37, 1328 (1959). 84. J. Trotter, ibid., 40, 1218 (1962). 85. C. H. Carlisle and R. A. Palmer, Acta Crystallogr., 15, 129

(1962). 86. B. Ziolkowska, Roczn. Chem., 36, 1341 (1962). 87. H. W. Ehrlich, J. chem. Soc., 509 (1962). 87a. V. I. Pakhomov, Kristallografiya, 5, 800 (1960); 7,456 (1962). 87b. V. I. Pakhomov, Zh. strukt. Khim., 4, 594 (1963); 5, 917 (1964). 88. E. O. Fischer and V. Piesberger, Z. Naturf., B, 11, 758 (1956). 89. I. Matsunaga, Bull. chem. Soc. Japan, 30, 227 (1957); Chem.

Abstr., 51, 17,283 (1957).

INTRODUCTION 9

90. I. Kadomtzeff, Bull. Soc. chim. Fr., D, 394 (1949). 91. I. Kadomtzeff, C.r. hebd. Seanc. Acad. Sci., Paris, 230, 443

(1950). 92. I. Kadomtzeff, ibid., 228, 681 (1949). 93. W. C. Horning, F. Lautenschlaeger and G. F. Wright, Can. J.

Chem., 41, 1441 (1963). 94. B. Matthews, Chem. ZentBl., 1, 224 (1906). 95. E. Bergmann and W. Schutz, Z. phys. Chem., B, 19, 401

(1932). 96. G. C. Hampson, Trans. R. Soc., 30, 877 (1934). 97. M. Kesler, Croat, chem. Acta, 34, 123 (1962). 98. W. J. Curran and H. H. Wenzke, J. Am. chem. Soc., 57, 2162

(1935). 99. I. E. Coop and L . E. Sutton, J. chem. Soc., 1269 (1938). 100. C. P. Smyth, J. org. Chem., 6, 421 (1941). 101. F. G. Ratman, Zh. prikl. Khim., Leningr., 9,591 (1936). 102. B. C. Curran, J. Am. chem. Soc., 64, 830 (1942). 103. L . Malatesta, Re. 1st. lomb. Sci. Lett., 78, 1 (1944-1945);

Chem. Abstr., 42, 3630 (1948). 104. F.Hein, A. Schleede and H. Kallmeyer, Z. anorg. Chem., 311,

260 (1961). 105. R. S. Armstrong, C. G. Le Fevre and R. J. W. Le Fevre, J.

chem. Soc., 371 (1957). 106. J. Sipos, H. Sawatzky andG. F.Wright, J. Am. chem. Soc., 77,

2759 (1955). 107. B. C. Curran, ibid., 63, 1470 (1941). 108. M. Kesler, Referat. Zh., Khim., 20B220 (1964). 109. J. B. Johns, W. D. Peterson and R .M. Hixon, J. phys. Chem.,

Ithaca, 34, 2218 (1930). 110. J. B. Johns and R. M. Hixon, ibid., 34, 2226 (1930). 111. W. V. Evans and R. Pearson, J. Am. chem. Soc., 64, 2865

(1942). 112. W. Strohmeier, Z. Elektrochem., 60, 396 (1956). 113. G. Jander and K. Brodersen, Z. anorg. Chem., 265, 117 (1951). 114. J .L . Maynard andH. C.Howard, J. chem. Soc., 123, 960(1923). 115. R. Sugden, ibid., 316 (1929). 116. T . W. Gibling, ibid., 380, 383 (1944). 117. H. W. Thompson and I. W. Linnett, Trans. Faraday Soc., 32,

681 (1936). 118. G. F. Phillips, B. E. DixonandR.G. Lidzey, J. Sci. Fd Agric,

10, 604 (1959); Chem. Abstr., 54, 7044 (1960). 119. T . Charnley and H. A. Skinner, J. chem. Soc., 1921 (1951). 120. L . H. Long and J. Cattanach, J. inorg. nucl. Chem., 20, 340

(1961). 121. C. T . Mortimer, H. O. Pritchard and H. A. Skinner, Trans.

Faraday Soc., 48, 220 (1952). 122. L . O. Brockway and H. O. Jenkins, J. Am. chem. Soc., 58,

2036 (1936).


123. P. W. Allen and L . E. Sutton, Acta Crystallogr., 3, 46 (1950). 124. M. Berthelot, C. r . hebd. Seanc. Acad. Sci., Paris, 129, 918

(1899). 125. R. H. Smith and D. H. Andrews, J. Am. chem. Soc., 53, 3661

(1931). 126. D. M. Fairbrother and H. A. Skinner, Trans. Faraday Soc.,

52, 956 (1956). 127. C. I. C her nick, H. A. Skinner and I. Wasso, ibid., 52, 1088

(1956). 128. W. F. Lautsch, Chem. Tech., Berl., 10, 419 (1958). 129. A. S. Carson, E. M. Carson and B. R. Wilmshurst, Nature,

Lond., 170, 320 (1952). 130. S. J. W. Price and A. F. Trotman-Dickenson, Trans. Faraday

Soc., 53, 939 (1957). 131. H. A. Skinner, Reel. Trav. chim. Pays-Bas Belg., 73, 991

(1954). 132. K. Hartley, H. 0 . PritchardandH. A.Skinner, Trans. Faraday

Soc., 46, 1019 (1950). 133. K. Hartley, H. O. Pritchard and H. A. Skinner, ibid., 47, 254

(1951). 134. L . H. Long and G. W. Norrish, Trans. R. Soc., A, 241, 587

(1949). 135. K. Hartley, H. O. PritchardandH. A. Skinner, Trans. Faraday

Soc., 48, 220 (1955). 136. K. Stevenson, Discuss. Faraday Soc., 10, 35 (1951). 137. A. S. Carson, D. R. Stranks and B. R. Wilmshurst, Proc. R.

Soc, A, 244, 72 (1958).

CHAPTER 1

Reactions of Metallic Mercury and Mercury Salts with RHal

On reacting methyl iodide with metallic mercury in the presence of sunlight, Frankland (in 1853) [1] obtained methylmercury iodide, and the generalized form of this method, in which halogenated hydrocarbons were reacted with metallic mercury, was used to prepare the f irst organomercury compounds in accordance with the following

RX + H g R H g X

However, this method has not achieved preparative importance, since alkyl chlorides generally do not react, the bromides react only with difficulty and the reaction usually does not proceed readily even with alkyl iodides, though they are still the most suitable halides in this respect.

This reaction has been carried out with methyl iodide [1, 2], ethyl iodide [3-5], propyl iodide [2] and others. Thus, the reaction proceeds readily with allyl iodide, even in the absence of light [6, 7]. Propargyl iodide [8] also reacts and methylene iodide gives two products: ICH2HgI [2, 9, 37] and IHgCH2HgI [9, 37]; the yields can be improved by using finely divided mercury and ultra-violet light [9a]. Sakurai has carried out the reaction with iodoform [9], The substituted acetylene C6H5C = CI has been mercurated at IOO0C [10]. The mixed halides CCl3I [11], CHCl2I [1] and 3-iodo-l , 1-di-chloroprop-l-ene [11] react with metallic mercury in the presence of ultra-violet light, or when heated to 70-80°C and stirred energet-ically. Further iodides capable of undergoing this reaction include the allylic iodides of the type CXY = CHal-CH2I (where X and Y = H or Cl, and Hal = Cl or Br [12]) 3-iodo-l,l-dichloro-2-methylpropene [11, 13] and ethyl iodoacetate [14].

Aromatic iodides form derivatives of the type ArHgI when mixed with metallic mercury and continuously exposed to light. The yields are very low [14-16], but can be increased somewhat by using a brush stirrer to remove the deposit from the walls of the vessel [14]. The yields are exemplified by 3% of C6H5HgI [14-16] and 6-8% of OL-C10H7HgI [14, 16].



Maynard [17] has shown that the reaction between mercury and methyl iodide is catalysed by Hg2Ijformedunder the action of direct sunlight.

Synthesis of allylmercury iodide [ 6 l . A yellow crystall ine mass forms rapidly when a mixture of allyl iodide and metallic mercury is shaken. The product can be extracted f rom this mass with hot alcohol or ether. When the solution is cooled, al lylmercury iodide r e -crystal l izes in the form of shiny white flakes; m.p. 135°C.

Perfluoroalkylmercuries were f irst prepared by this method by Emeleus and Haszeldine [18-22]. Thereact ionproceedsunderthe action of prolonged exposure to sunlight or a mercury lamp, or on prolonged heating in a sealed tube at high temperatures (CF3I at 260-290°C for 12 hours [19]; C2F5I at 120°C for 5-6 days with exposure to light; n-C3F7I at 220 0C for 24 hours [22]). Trifluoromethylmercury iodide is obtained in a good yield when the reaction is carried out in a solvent (perfluoromethylcyclohexane) and the reaction mixture is both heated and exposed to light [19].

Preparation of trifluoromethylmercury iodide [ 10]. A solution of 7.5 gof CF3I in 4 ml of perfluoromethylcyclohexane is heated with 10 ml of Hg in a sealed tube at I lO0C for 36 hours, with shaking and irradiation with a mercury lamp. The product crystal l izes out on cooling. The solvent is removed and the product extracted with ether. Yie ld: 7.5 g (80% on the reacted 4.7 g of CF 3 I ) ; white crystals subliming at 80°C, m.p. 112.5°C [18],

l , l , l -Tr i f luoroprop-3-ylmercury iodide is formed in the reaction of a polymer formed from CF3Iandethylenewith an excess of ethy-lene in the presence of mercury [23], Examplesof the indirect fo r -mation of compounds of the type R'Hgl are given by the reactions of R r aAsI3-^ [24] and C6H5SbI2 [25] with R'I and mercury. Dimethyl-mercury may be formed when methyl bromide is subjected to photo-lysis in the presence of mercury [26].

Trichloromethylmercury bromide is obtained in a maximum yield of 41% when trichlorobromomethane is reacted with metallic mer-cury in the presence of azobisisobutyronitrile and the reaction mixture subjected to irradiation, energetic stirring and heating at 70-80°C for 3 hours [11].

Bromo-derivatives in which the C-Br bond is activated by con-jugation with a multiple bond as in

I I I I I N = C - C - B r , > C = C — C — B r or O = C - C - B r

I I I

can react with metallic mercury under mild conditions to give de-rivatives of the type RHgBr [15,17, 27], Thus, bromobenzyl cyanide reacts with Hg at room temperature, in an ethereal solution or without a solvent [27],

The reactions of metallic mercury with ethyl a-bromophenyl-acetate [14, 28], Z-menthyl a-bromophenylacetate and cinnamyl bromide [14] proceed at room temperature without any irradiation,

REACTIONS OF MERCURY AND ITS SALTS WITH RHaI 13

the yields of the corresponding RHgBr being 73, 31 and 82%, respec-tively. When the esters XCgH4CHBrCO2C2H5 are shaken with Hg for 4 hours, the corresponding XC6H4CH(HgBr)CO2C2H5 derivatives are obtained ( X = p-F, p-Br, p-1, O-CH3, P-(CH3 )3C1 m-CH3 [29], o -B r , P-NO2 , P-C2H5, p-iso-C3H ? , p-CH3 [29a]; see also [30]). Cinnamyl bromide reacts with Hg so vigorously, that it must be diluted with ethanol to avoid polymerization and charring. Allyl bromide reacts with metallic mercury even in the dark, though only slowly. On irradiation with ultra-violet light, however, the reaction proceeds more rapidly; in fact, it becomes so vigorous that energetic agitation, preferably with a brush st irrer , must be applied to prevent the formation of organomercury polymers. Under these conditions, several alkyl bromides do not form organomercury compounds with metallic mercury. With ethyl bromomalonate and a-bromophenyl-acetaldehyde, the reaction leads to the corresponding organo-mercury polymers [14, 16].

Preparation of cinnamylmercury bromide [ l 4 ] . Cinnamyl bromide(19.7 g, 0.1 mo l e ) i s mixed with an equal volume of 96% ethanol and 100.3 g of metal l ic mercury (0.5 g-atom) . The reaction mixture is shaken v igorously f o r 15 minutes and then gently warmed and reduced in volume. The unreacted mercury is decanted and ethanol added to the residue until a paste is f o rmed. The paste is f i l t e red and treated with hot benzene. The benzene solution is reduced in volume by evaporation until the f i r s t crysta ls appear. T h e crys ta l -l ization takes 2-3 hours, a f ter which the cinnamylmercury bromide crysta ls are f i l t e red at the pump and washed with cold petroleum naphtha. Y ie ld : 32.7 g (82%). A f t e r r ec rys ta l -l ization f r o m benzene, the melt ing-point is 340-345°C (on rapid heating).

On reacting with metallic mercury, the mixed allyl halides CH2=CClCCl2Br, CCl2=CHCH2Br, and CH2=CBrCCl3 all lead to the same product, namely CCl2=CClCH2HgBr [13] (the reaction with the f i rs t two halides takes 2-3 days in the presence of diffuse light, or 3-4 hours when exposed to ultra-violet light; the third allyl halide reacts only in the presence of ultra-violet light).

Diphenylmercury is formed when bromobenzene is reacted with mercuric chloride in the presence of metallic sodium [31]:

2C6H5Br + HgCl2 + 4Na - » (C8H5)2Hg + 2NaCl + 2NaBr

By reacting metallic Hg with a mixture of bromostyrene and HgCl2, Das Gupta [32] obtained, after distillation, styrylmercury bromide and a substance melting at 1520C which was later [33] shown to be a mixture of styrylmercury bromide (m.p. 2020C) and distyryl-mercury (m.p. 137°C). The high-melting and sparingly soluble residue also formed in this reaction is also a mixture [33],

Some alkyl iodides react with mercurous salts to form alkyl-mercury iodides [34]. Thus, when an excess of methyl iodide is boiled for 18 hours with mercurous sulfate, methylmercury iodide is obtained in a yield of 80%. With ethyl iodide, the yield is only 10-15%; butyl iodide does not react at all (nor does iodobenzene). Methyl iodide heated to 40-800C with mercurous acetate or ben-zoate gives the corresponding methylmercury salt in a yield of 25

References see p. 14


and 50%. Alkylmercury salts are obtained when mercuric benzoate is reacted at 40-80 0C with an excess of RI in the presence of mer-curous salts (R = CH3, C2H5, n-C4Hg, C6H5) [34],

Synthesis of methy lmercury iodide [34 ] , Mercurous sulfate (0.025 mole ) is heated for 18 hours in 50 ml of methyl iodide at the boiling temperature of the latter. The methyl-mercury iodide (0.020 mole) isolated from the reaction mixture melts at 143°C; yield: 80% on the sulfate.

The decomposition of bis-(triethylgermyl)mercury in bromo-benzene under the influence of ultra-violet irradiation leads to diphenylmercury and triethylbromogermane [35],

Substituted acetylenes containing iodine react with mercuric iodide or cyanide to give directly organomercury compounds in which both valences of mercury are satisfied by organic residues:

2RC=CI + HgX2 (RC=C)2Hg + 2XI

This reaction is unique in the preparation of organomercury com-pounds in that it does not proceed with other types of halogenated hydrocarbons.

Bibliography

1. E. Frankland, Justus Liebig's Annln Chem., 85, 365 (1853). 2. U.S. Pat. 2,914,451 (1959); Chem. Abstr. 54, 5467 (1960). 3. A. Strecker, Justus Liebig's Annln Chem., 92, 75 (1854). 4. G. Buckton, ibid 108, 103 (1858). 5. J. Jose and C. Espinoza, Revta qufm.-farm., 4, 2 (1947);

Chem. Abstr., 42, 2924 (1948). 6. N. N. Zinin, Justus Liebig's Annln Chem., 96, 363 (1855). 7. E. Linnemann, ibid., 140, 180 (1866). 8. L. Henry, Ber. dt. chem. Ges., 17, 1132 (1884). 9. I. Sakurai, J. chem. Soc., 37, 658 (1880); 39, 485 (1881); 41, 9a. H. E. Simmons and R. D. Smith, J. Am. chem. Soc., 81,

4256 (1959). 10. I. U. Nef, Justus Liebig's Annln Chem., 308, 299 (1898). 11. A. N. Nesmeyanov, R. Kh. Freidlina and F. K. Velichko, Izv.

Akad. Nauk. SSSR, Otdel. khim. Nauk, 40 (1958), Dokl. Akad. Nauk. SSSR, 114, 557 (1957).

12. R. Kh. Freidlina and F. K. Velichko, Izv. Akad. Nauk. SSSR, Otdel. khim. Nauk, 55 (1961).

13. R. Kh. Freidlina and F. K. Velichko, ibid., 1225 (1959). 14. A. N. Nesmeyanov and O. A. Reutov, ibid., 655 (1953). 15. G. A. Razuvaev and M. A. Shubenko, Zh. obshch. Khim., 21,

1974 (1951). 16. O. A. Reutov and M. A. Besprozvannyi, Dokl. Akad. Nauk.

SSSR, 80, 765 (1951).

REACTIONS OF MERCURY AND ITS SALTS WITH RHaI 15

17. I. L. Maynard, J. Am. chem. Soc., 54, 2108 (1932). 18. A. A. Banks, H. J. Emeleus, R. N. Haszeldine and V. Kerrigan,

J. chem. Soc. 2188 (1948). 19. H. J. Emeleus and R. N. Haszeldine, ibid., 2948 (1949). 20. H. J. Emeleus, Bull. Soc. chim. Fr. , 909 (1953); Fortschr.

chem. Forsch., 2, 609 (1953). 21. R. N. Haszeldine, Angew. Chem., 66, 693 (1954). 22. H. J. Emeleus and J. J. Lagowski, J. chem. Soc., 1497 (1959). 23. R. N. Haszeldine, ibid., 2856 (1949) 24. M. M. Baig and W. R. Cullen, Can. J. Chem., 39, 420 (1961). 25. M. M. Baig and W. R. Cullen, ibid., 40, 161 (1962). 26. C. F. Boynton, jun., and H. A. Taylor, J. chem. Phys., 22,

1929 (1954). 27. A. E. Kretov and V. A. Abromov, Zh. obshch. Khim., 7, 1572

(1937). 28. A. N. Nesmeyanov, 0. A. Reutov and S. S. Poddubnaya, Izv.

Akad. Nauk. SSSR, Otdel. khim. Nauk, 649 (1953). 29. I. P. Beletskaya, O. A. Reutov and G. A. Artamkina, Zh.

obshch. Khim., 32, 241 (1962). 29a. I. P. Beletskaya, G. A. Artamkina, E. A, Shevlyagina and

O. A. Reutov, ibid., 34, 321 (1964). 30. O. A. Reutov, I. P. Beletskaya and G. A. Artamkina, Zh.

obshch. Khim., 30, 3220 (1960). 31. A. Michaelis and A. Reese, Ber., dt. chem. Ges., 15, 2876

(1882) . 32. H. N. Das Gupta, J. Indian chem. Soc., 14, 400 (1937). 33. A. N. Nesmeyanov and T. A. Kudryavtseva, Uch. zap. MGU,

151, 57 (1951). 34. V. N. Latyaeva, A. V. Malysheva and G. A. Razuvaev, Zh.

Vses. khim. obshch., 7, 594 (1962). 35. N. S. Vyazankin, G. A. Razuvaev and E. N. Gladyshev, Dokl.

Akad. Nauk SSSR, 151 1326 (1963). 36. T. H. Vaughn, J. chem. Soc., 55, 3453 (1933). 37. E. P. Blanchard, D. C. Blomstrom and H. E. Simmons, J.

organometall. Chem., 3, 97 (1965).

CHAPTER 2

Synthesis of Organomercury Compounds with Grignard Reagents and Organolithium Derivatives

The reaction between Grignard reagents and mercury salts re-presents the most widely used method in the synthesis of organo-mercury salts of the type of RHgX (where R is an alkyl, cycloalkyl or an arylalkyl residue) and in the synthesis of symmetric diorgano-mercury compounds of the type R2Hg. It should be added, however, that, when compounds of this second type are to be prepared in larger amounts, the reaction between alkyl halides and sodium amalgam offers a more convenient route in those cases in which the method is applicable. Although the Grignard method can also be applied to the synthesis of the simplest aromatic derivatives of mercury, the diazo-method, and in some cases directmercuration, provide a more suitable preparation of these compounds.

Pfe i f fer [1] was the f irst to use Grignard reagents for the syn-thesis of organometallic compounds including organomercuries, further important work having been carried out by Hilpert and Griittner [2], Marvel and Gould [3], GilmanandBrown [4] and Slotta and Jacobi [5].

The interaction between mercury halides and organomagnesium halides involves the following reactions:

HgX2 + RMgX RHgX + MgX2

RHgX + RMgX R2Hg + MgX2

R2Hg + HgX2 - » 2RHgX

Moreover, when the halogen in HgX2 isdi f ferentfrom that in RMgX, the interaction also involves halogen exchange.

Mercuric chloride is used the most often, since it is the most readily available and the most readily ether-soluble mercury salt. When HgCl2 is used in the solid state and the reaction mixture is not stirred sufficiently vigorously, solid lumps are frequently formed and these hinder the course of the reaction. It is therefore best to place the solidHgCl2in the thimble of an extractor connected to the reaction vessel. Ether is then made to percolate through it

16

SYNTHESES WITH GRIGNARDS AND ORGANOLITHIUMS 17

and carry the dissolved HgCl2 down into the Grignard reagent. Mercuric bromide is somewhat less soluble in ether, but it does not form lumps, since it is a much finer powder than HgCl2 (see, for example, the synthesis of C 6H^H 2HgCl later inth ischapter ) . Although it has a low solubility, mercuric iodide can be and is used for the preparation of organomercury iodides.

As regards the various organic halides, any of them capable of forming Grignard reagents can be used. However, in the f irst stage of the synthesis, i.e. in the preparation of the organomercury halide, the Grignard reagent and the mercury halide must contain the same halogen, otherwise the reaction may lead to a mixture that is very difficult to separate. Thus, the basically equimolecular mixture of n-C4H9HgBr and n-C4H9HgCl formed in the reaction between HgCl2

and U-C4H9MgBr cannot be separated [3], The melting-temperature of this mixture is very close to the melting-points of the two halides. An analogous mixture is obtained when mercuric chloride is reacted with n-C3H7MgBr Oriso-C3H7MgBr1OrwithalkylmagnesiumiOdides.

According to Hinkel and Angel [6], the reaction between CH3MgI and HgCl2 leads to the formation of the adduct 2CH3HgI.CH3HgCl. However, since the reaction between HgCl2 and RMgClaccording to Marvel and Gould, does not proceed very smoothly, Slotta regards the corresponding bromides to be the best reactants for the pre-paration of organomercury salts, the resulting bromides being con-veniently used to obtain organomercury chlorides and iodides through the hydroxides (see Chapter 14). Unlike mercuric iodide, mercuric bromide is soluble in hot water, which permits easy separation of the reaction product. However, mercuric iodide can also be removed easily by cautious dissolution of the reaction mixture in a cold aque-ous solution of KI, in which organomercury iodides are insoluble.

In a method put forward by Rumpf [7], alkylmagnesium bromides are reacted with mercuric chloride, and pure alkylmercury bromide or chloride is obtained from the resulting mixture of the two via the alkylmercury ethoxide: the mixture is treated with an ethanolic solution of sodium ethoxide and the filtrate is precipitated with aqueous HCl or HBr according to the required alkylmercury halide.

Reagents containing different halogens can, of course, also be used if the aim is to prepare diorganomercuries. The second stage of synthesis is hampered by the fact that the poor ether-solubility of the organomercury halide slows down the reaction. In order to obtain the dialkylmercury in a good yield, it therefore is necessary to use mechanical stirring, prolonged heating and a large excess (30-70%) of the Grignard reagent [3], The resulting yields (45-65%) can be further increased to (70-80%) by increasing the reaction temperature [4, 8], When all the HgCl2 has been introduced from the extractor into the reaction flask, the extractor is replaced by an upright condenser and the ether is distilled off by gentle heating on a water-bath accompanied by continuous stirring. Thistechnique reduces the reaction time and eliminates the need for an excess of



the Grignard reagent. When the intermediate salt RHgX has a par-ticularly low ether-solubility, the reaction is promoted by adding benzene.

Diorganomercury compounds are also suitably prepared by the action of a Grignard reagent on an organomercury halide. The com-pounds thus obtained include didodecylmercury, ditetradecylmercu-ry, dihexadecylmercury, dioctadecylmercury [9], dibenzylmercury [10, 11], di-/3-phenylethylmercury [12], di-/3-methyl-/3-phenylpro-pylmercury [13], di-p-s-butylphenylmercury [10], diphenylmercury [14] and di-y-phenylpropylmercury [10].

Owing to their low thermal stability, the dialkylmercuries in which the metal is linkedtotertiarycarbonatoms must be prepared at room temperature, and they are obtained in appreciably lower yields than the analogous alkyl or aryl derivatives in which the mercury is linked to primary carbon atoms. The same applies to mercury compounds with secondary radicals which are also rela-tively unstable, although to a smaller extent. Much less work has been done on the secondary and the tertiary derivatives than on the primary ones.

The Grignard reagent must always be freed from the magnesium residues by decantation or, better, by filtration.

Organomercury compounds can be synthesized with organomag-nesium compounds in tetrahydrofuran. It has been shown with di-n-propylmercury, dicyclopropylmercury [15] and divinylmercury [15, 16] that the replacement of ether as a medium by tetrahydro-furan reduces the reaction time and considerably increases the yield. However, the solvent must in each case suit the product and, on account of the greater ease of separation, low-boiling compounds, e.g. dimethylmercury with a boiling-point of 92°C, are more con-venient to prepare in ether. The reaction can also be carried out in a mixture of ether and tetrahydrofuran.

Organomercuries can be synthesized from organomagnesium compounds in xylene [17] or in heptane [18] in the absence of ether, and the yields are not lower than those obtained in an ethereal medium.

Although only mercuric halides are used in practice as starting materials in the Grignard synthesis, certain compounds in which the mercury is linked to carbon interact with Grignard reagents in the following manner when their R-Hg bond is sufficiently labile:

RHgX + R'MgBr-* R'HgX + RMgBr

Such reactions include the interaction between a-naphthylmercury bromide and ethylmagnesium bromide giving diethylmercury [2]; between allylphenylmercury and phenylmagnesium bromide [19]:

CH3=CHCH2HgC6H5 + C6H5MgBr C6H5MgCH2CH=CH2 + C6H5HgBr

between halogenomercuriacetophenone and ethylmagnesium bromide


(or phenylmagnesium bromide) [20]:

C 8 H 6 C O C H 2 H g X + R M g X C 6 H 5 C O C H 2 M g X + R H g X

and finally the interaction between o-hydroxyphenylmercury bro-mide and ethylmagnesium bromide [20]:

H O C 6 H 4 H g B r + 2C 2 H 5 MgBr B r M g O C 6 H 4 M g B r + C 2 H 6 + C 2 H 5 H g B r

However, di-(bromoethynyl)mercury reacts with phenylmagne-sium bromide to form bromoethynylmagnesium bromide and di-phenylmercury [21]:

( B r C = C ) 2 H g + 2C 6 H 5 MgBr 2 B r C = C M g B r + ( C 6 H 5 ) 2 H g

Just as for the purely inorganic mercury salts, many products of the addition of mercury salts to the olefins, their derivatives, or acetylenes react with Grignard reagents in the following manner [22, 23]:

C 2 H 5 O C 2 H 1 H g B r + 2C 2 H 5 MgBr 2C 2 H 4 + C 2 H 6 + C 2 H 5 H g B r + Mg 2 OBr 2

C l C H = C H H g C l + C 2 H 5 M g B r C 2 H 2 + C 2 H 5 H g C l + M g C l B r

C 6 H 5 C H - C H 2 H g X + C 2 H 5 M g X C 6 H 5 C H = C H 2 + C 2 H 5 H g X + C H 3 O M g X

I O C H 3

The radical exchange between R2Hg and RMgX and between R2Hg and RLi will be discussed in Chapter 14.

a) Preparation of Organomercury Halides

Synthesis of methylmercury bromide [5 ] . M e t h y l m a g n e s i u m b r o m i d e i s p r e p a r e d f r o m 12 g of magnesium in 300 ml of absolute ether and 48 g of methyl bromide. The solution is heated f o r 30 minutes on a water bath to complete the react ion and f i l t e red through glass wool. Finely crysta l l ine mercur ic bromide (200 g ) is added with gentle shaking and the reaction mixture brought to the boil f o r another hour. A f t e r the mixture has been cooled, 20 ml of water a re added, the ether disti l led off, and decomposit ion completed by adding an excess of water. The resulting thick pasty substance is f i l t e red at the pump and twice boiled with 1% HCl. Y ie ld : 139 g (94%). It is recrys ta l l i zed f r o m ethanol, incurring a 10% loss (character ist ic of the recrysta l l i zat ion of all these halides); m.p, 172°C (see also [24]).

Synthesis of methylmercury iodide [ 3 ] . The Grignard reagent is prepared f rom 2.4 g of magnesium and 15 g of methyl iodide in 50 ml of ether. It is f i l t e red through glass wool and placed in a f lask fitted with a re f lux condenser, a dropping funnel and a s t i r r e r with a mercury seal. T o this are added, with st irr ing, 30 g of HgCl2 in 150 ml of ether, the rate of the addition being such as to maintain the ether in a gently boil ing state. The reaction mixture is then brought to the boi l f o r a further hour, cooled, a little water added and the ether disti l led of f . An excess of water (200 ml ) is added to the residue, together with 5 to 10 ml of conc. HCl, to remove the unreacted mercur i c chloride and the magnesium salt. Methy lmercury iodide is f i l t e red at the pump and recrys ta l l i z ed f r o m ethanol. Y ie ld : 29-30 g (85-88%); m.p. 142-143°C.

Hinkel and Angel [6] believe, however, that this operation leads to the molecular compound 2CH3HgLCH3HgCl and that puremethyl-



mercury iodide is obtained when mercuric chloride is replaced as a starting material by an equivalent amount of mercuric iodide.

Synthesis of ethylmercury bromide [ s ] . The Grignard reagent prepared from 12 g of magnesium and 55 g of ethyl bromide in 200 ml of ether is heated for 30 minutes and filtered through glass wool. To this is added HgBr2 (200 g), at such a rate that the ether is gently boiling throughout the addition. The rest of the synthesis is carried out as with methylmercury bromide. Yield: 140 g (90%). After recrystallization from ethanol the melting-point is 198°C (198.5°C [25]).

The effects of the solvent and of the halogen in the mercuric halide on the yield of C2H5HgI in the reaction of ethylmagnesium iodide with mercuric halides, and in the synthesis of ethylmercury bromide from ethylmagnesium bromide, have been described. These ethylmercury salts can be obtained in good yields by carrying out the reaction in xylene.

Synthesis of n-propylmercury bromide [ s ] . n-Propylmagnesiumbromide (preparedfrom 12 g of magnesium and 62 g of propyl bromide in 100 ml of ether) is reacted with 200 g of mercuric bromide as described for the preparation of methylmercury bromide. The only difference is the separation of the mixture into layers on the addition of 100 g of the mercuric salt. Yield: 140 g (86%). After recrystallization from ethanol, the melting-point is 140°C.

The same method was also used [5] for the synthesis of the bro-mides of n-butylmercury (m.p. 1360C), n-pentylmercury (m.p. 127°C), n-hexylmercury (m.p. 127.5°C), n-heptylmercury (m.p. 118.5°C) and n-cetylmercury (m.p. 101.5°C). For the middle mem-bers of the series, the yields are approximately 50%, whereas for the cetyl derivative it is 90%.

The reaction between isopropylmagnesium bromide and mercuric chloride leads to a double salt between isopropylmercury bromide and HgCl [26].

Synthesis of s-buty lmercury bromide [27] . The Grignard reagent (preparedfrom 100 g of s-butyl bromide and magnesium in 300 ml of ether) is added to finely powdered mer-curic bromide (300 g ) suspended in 250 ml of ether, the rate of addition being such as to keep the ether boiling. The mixture thickens appreciably and is stirred energetically for 2 hours after the mixing. It is then decomposed with cold 0.5% aqueous sulfuric acid, the ethereal layer separated and the ether distilled off under vacuum. The resulting residue is twice recrystallized from ethanol. Yield: 97 g (JQff0)', m.p. 39°C.

Synthesis of t-butyl bromide [28]. An excess of mercuric bromide is added to an ethereal solution of t-butylmagnesium bromide in the cold. An hour later, the mixture is decomposed with water and the ethereal layer separated and dried over calcium chloride. The ether is then evaporated off. When the product is heated, even in solution, it decom-poses and mercurous bromide separates out. It cannot be recrystallized and melts at 106°C (with decomposition). (Synthesis of t-butylmercury chloride has also been de-scribed [19].)

Synthesis of neopentylmercury chloride [29] . The Grignard reagent prepared from 105 g (1 mole) of neopentyl chloride and 24 g (1 g-atom) of magnesium in 350 ml of dry ether (yield: 90%) is added to 270 g (32 g in excess) of crushed HgCl2 suspended in 1 liter of dry ether, the rate of addition being such as to ensure continuous gentle boiling


of the ether. The reaction mixture is then boiled f o r 3 hours with st i r r ing, the ether dist i l led off and the residue mixed with 1 l i ter of water. The product is crysta l l i zed f r o m 2 l i ters of 95% ethanol. Y i e ld : 239 g (90%); m.p. 117-118°C (see also [30, 31, 42]).

The reaction between trimethylsilylmethylmagnesium chloride and mercuric chloride leads to trimethylsilylmethylmercury chlo-ride in a yield of 80% [25, 32], whereas the reaction between 1 mole of l-(trimethylsilyl)ethylmagnesium chloride and 2 moles of HgCl2 in ether results in l-(chloromercuri)ethyltrimethylsilane CH3CH(HgCl) Si(CH3)3 in a yield of 40%; m.p. 97°C[33]. Speier [34] has described the synthesis of 5-hydroxypentylmercury chloride from trimethyl-silylhydroxypentylmagnesium chloride and HcC I2 involving hydroly-sis of the Si-O bond with dil. HCl. n-Octylmercury chloride has been prepared from the corresponding organomagnesium compound in a non-ethereal medium [18].

Synthesis of n-octylmercury chloride [ l 8 l . n-Octyl iodide (26.7 g, 0.11 mo l e ) in 50 ml of heptane is added, with st irr ing in a current of nitrogen, to 3 g (0.12 mo le ) of magnesium f i l ings, with gentle boiling of the solvent. The reaction mixture is heated f o r 2 hours and then cooled with ice . Mercur i c chlor ide (20 g, 0 .074mole ) is then added in smal l portions with st irr ing and the mixture heated f o r l1^ hours. The react ion mixture is f i l t e red and the solid on the f i l t e r washed a f ew t imes with 30-ml portions of boil ing heptane. White crysta ls separate out f r om the f i l t ra te on cooling. The solution is treated with KOH and methanol and then with a saturated solution of KCl. Y ie ld : 21 g (81%); m.p. 115°C.

Synthesis of 2,2,3,3-tetramethyl-Z -butylmercury chloride [35] . Magnesium (6.3 g ) is heated with a crysta l of iodine until the latter has disappeared. Ethyl bromide (2.2 m l ) is then added, together with 80 ml of ether, and the solution heated to boil ing. Chlorohexa-methylethane (33.4 g, 0.225 mo l e ) in 150 ml of ether is then added over a per iod of 8 hours. Boil ing is then continued f o r 19 hours. The yie ld of the organomagnesium compound amounts to 70%. The resulting Gr ignard reagent is slowly s t i r red into a solution of 70 g of HgCl 2 in 250 ml of absolute ether and the mixture re f luxed f o r 4 hours. The ether is dist i l led off, 300 ml of water and 10 ml of hydrochloric acid a re added and the reaction mixture heated on a water bath. The organomercury compound is f i l t e red at the pump, washed with water and recrys ta l l i zed f i r s t f r o m aqueous ethanol, then f r o m methanol and f inal ly f r o m petroleum ether. Y ie ld : 35%; f inal m.p. 170-171°C.

Synthesis of n-dodecylmercury hydroxide [ 3 6 ] . T h e G r i g n a r d r e a g e n t i s p r e p a r e d , in a 300-ml f lask, f r o m 2.5 g of magnesium and 24.9 g (0.1 mo l e ) of n-dodecyl bromide (b.p. 140-142°C/11 mm Hg ) in 150 ml of ether. An equivalent amount of dry mercur i c chloride is then added in small portions and the mixture boiled f o r 3 hours. The boil ing is inter-rupted twice and the substance cooled and st i r red with a g lass spatula. Th i s is fo l lowed by the addition of 75 ml of water, disti l lation of the ether, cooling and f i l ter ing at the pump. The product (38 g ) is dr ied in a i r . The crude product is then placed in 160 ml of a 50:50 mixture of benzene and ethanol and 100 ml of a 40% solution of KOH in methanol, and the solution is heated on a water bath f o r 10 minutes. Cooling of the f i l t rate leads to separation of the hydroxide, which is then recrys ta l l i z ed f r o m pyridine (m.p. 80°C; the melt ing-point of the chlor ide is 115°C). According to Meals [9], the chlor ide melts at 114-114.5°C; the melting-point of the bromide is 108°C. Y ie ld : 69% on the lauryl bromide [36] (see also [37]).

The same method was used to prepare the hydroxides, chlorides and bromides of n-tetradecylmercury, n-hexadecylmercury and n-octadecylmercury [36] (see also [9]).



Synthesis of benzylmercury chloride [ 2 ] , Finely crushed dry mercuric chloride (46.7 g, 1.1 moles ) is added in 2-g portions to a solution of 23.8 g of benzylmagnesium chloride in 100 ml of ether, with energetic and constant shaking or stirring. If the reaction is left unattended even for a few seconds, the mass adheres so tenaciously to the bottom of the flask that it is almost impossible to detach it. Speeding the reaction by heating is not recommended, since this gives r ise to lumps. When all the HgCl2 has been added, the flask is again shaken or st irred for some time and the reaction mixture then set aside for 24 hours. This is followed by refluxing for 2 hours, addition of ice and sulfuric acid and heating with 1% HCl to temperatures not exceeding 80°C to remove the excess HgCl 2 (the crude product has a low melting-point). The crude product is recrystal l ized from a 1:1 mixture of xylene and ethanol; m.p. 104°C; yield of pure product: 43 g (84%) (see also [38-40]).

Several authors have described the synthesis of /3-phenylethyl-mercury bromide [10, 41] and chloride [42], the latter being ac-companied by the formation of the diorganomercury compound.

The action of vinylmagnesium bromide on mercuric chloride [43], bromide [12, 43] and iodide [43] (1 mole of RMgXto 1 mole of HgX2) in tetrahydrofuran leads to vinylmercury chloride (78%), bromide (64% [12] and 67% [43]) and iodide (83%) [43],

Synthesis of vinylmercury bromide [ l 2 ] . Magnesium (4.86 g, 0.2mole)and a crystal of iodine in 50 ml of absolute tetrahydrofuran are placed in a 1-l i ter three-necked flask fitted with a mechanical st i rrer with a mercury seal, a dropping funnel and a condenser (60 cm long) cooled with a mixture of acetone and solid CO2, the funnel being surrounded by a solid C O 2 cooling mantle. The condenser carries a drying tube f i l led with calcium chloride. Thef laskisheatedonawaterbath to 60-65°C and a solution of 25.5 g (0.23 mole) of dry vinyl bromide in 50 ml of absolute tetrahydrofuran is added dropwise with stirring. The reaction starts 20-30 minutes after the addition of 1-2 ml of the vinyl bromide solu-tion, and is accompaniedby the evolution of heat and a color change. As the vinyl bromide solution is added, the magnesium disappears and the reaction mixture assumes a brownish color. (If, after the end of the addition, some magnesium still remains unreacted, a further amount of a similar vinyl bromide solution is added dropwise, over 3-4 hours, until all the magnesium has disappeared.)

A solution of 68.4 g (0.189 mole) of dry mercuric bromide in 90 ml of absolute tetra-hydrofuran is then added dropwise to the resulting Grignard reagent (5-8°C), with vigor-ous stirring. This results in the formation of a voluminous white precipitate. The addition takes 1-1J4 hours. The product is then heated at 60-65° C for 2 hours and then decomposed with 100 ml of 3% HCl added dropwise over 10 minutes, whilst the substance is cooled with ice-water. The resulting solution is poured into 1 l iter of cold water and the precipitate f i l tered off, washed well with water, dried over calcium chloride for 12 hours and re-crystall ized f rom carbon tetrachloride. Yield: 36.8 g (64%); m.p. 169-1710C.

The reaction between butenylmagnesium bromide and HgBr2Ieads to trans-crotylmercury bromide [45].

Renaud [44] has described the use of ultrasonic waves in the pre-paration of propargylmercury halide from a mixture of propargyl bromide, magnesium and mercuric chloride.

Styrylmercury bromide can be obtained in a yield of 36% by the action of HgBr2 on styryl bromide in ether [46],

Synthesis of cyclohexylmercury bromide [47 ] . Very finely powdered mercuric bromide (45 g, 1.03 moles ) is added in small portions and with constant vigorous stirring to a solution of 23 g of cyclohexylmagnesium bromide in 100 ml of absolute ether. The dis-solution is accompanied by the liberation of an appreciable amount of heat. The Iayi s separate after some time, and when a further amount of HgBr 2 is added, it does nc solve. Flakes are gradually produced as the ether steadily boils off. The reaction mix-ture is boiled f o r 2 hours, decomposed with ice, acidified with HBr and all the ether


removed at 60° C in a current of a i r . A f t e r f i l trat ion and washing with cold absolute ethanol, the precipitate is heated in 500 ml of water f o r 30 minutes, with st irr ing, to r emove the unreacted HgBr 2 . The mixture is f i l t e red whilst hot, and the mater ia l washed care ful ly with water and ethanol and dried at 60°C. Y ie ld : 35 g (78%). Recrysta l l i zat ion f r o m benzene g ives white, shiny f lakes; m.p. 153°C.

Synthesis of cyolohexv lmercury chloride [ 47 ] , Th is compound is prepared f r o m 20 g of cyclohexylmagnesium chloride in 100 ml of ether and 48 g of mercur ic chlor ide, s imi lar to the synthesis of cyc lohexy lmercurybromide . Y ie ld : 30 g. Recrysta l l i zat ion f r o m ethanol or benzene g ives shiny white f lakes, m.p. 163-164°C.

With mercuric chloride or bromide, 4-methylcyclohexylmagnes-ium bromide gives a mixture of cis- and trans-4-methylcyclohexyl-mercury bromides in a yield of 65% [48]. This mixture can be separated into its two components since these isomers differ in their solubilities in benzene. The less soluble irans-isomer is re -crystallized from benzene, whereas the czs-isomer is obtained in the pure state by chromatographing the mother liquor on alumina.

The Grignard reaction with cW-bornyl chloride leads to the isomeric forms of 2-chloromercuricamphanes [49, 50]. From HgBr2 and nortricyclyl chloride (or a mixture of the latter and dehydronorbornyl chloride), we obtain nortricyclylmercury bro-mide via the Grignard reagent:

MgCl

+ H g Br * / \ / -HMgClBr

Synthesis of phenylmercury bromide [ 2 ] , Mercur i c bromide (72 g, 1.25 mo les ) is added in small port ions and with vigorous shaking to 28.7 g of phenylmagnesium bromide in 100 ml of ether and the mixture is wel l boiled f o r 4 hours. The ether (now containing no C 6 H 5 M g B r ) is then decanted and the residue boiled three t imes with 1% HCl to r emove the unreacted HgBr 2 . It is then thoroughly washed with hot water, ethanol and ether, and f inally dried at 100°C. Y i e ld of the crude product: 56 g (98%); a f ter recrysta l l i zat ion f r o m pyridine, it melts at 275cC (see also [17, 41, 51]).

Phenylmercury chloride has been prepared from phenylmagnes-ium chloride and mercuric chloride [17],

Synthesis of a-naphthylmercury bromide [ 2 ] , An excess of mercur i c bromide (43 g, 125% of the theoret ical amount) is added in small portions and with vigorous shaking to 22.3 g of a-naphthy lmagnesium bromide in 100 ml of ether. T h e m i x t u r e is boi led f o r 4 hours and cooled. The ether is decanted and the residue extracted three t imes with boiling 1% HBr to r emove the excess HgBr 2 l The residue is then washed wel l with ethanol and ether and rec rys ta l l i z ed f r om pyridine. Y ie ld o f thepure product: 30 g (75%); m.p. 202°C.

l,4-(Dibromomercuri)benzene is obtained in a yield of 38% when mercuric chloride, or better still, mercuric bromide [52], is r e -acted with a Grignard reagent prepared in situ from magnesium, p-dibromobenzene and ethyl bromide [52]. Owing to its lesser sol-ubility, l,4-(dibromomercuri)benzene can be easily separatedfrom the ethylmercury bromide and the p-bromophenylmercury bromide formed at the same time. Ethylmercury bromide is separated in turn from the remaining mixture by means of steam distillation.



Synthesis of l,4-(dibromomercuri)benzene [52]- Ethyl bromide (2 ml ) in 50 ml of ether is added slowly (over 30 minutes) to a stirred mixture of 2.40 g of magnesium in 50 ml of dry ether. T o this mixture is then added, over 75 minutes, a solution of 4.72 g (0.02 mole ) of p -dibromobenzene and 3.85 ml (altogether 0.06 mole) of ethyl bromide in 100 ml of ether. The reaction mixture is well boiled f o r 12 hours, after which another 1.2 ml of ethyl bromide are added. Al l the magnesium disappears after an hour, and introduction of 27.2 g (0.1 mole ) of mercuric chloride is started. The mercuric chloride is placed in the thimble of a Soxhlet extractor; its introduction into the reaction mixture requires 24 hours. The solid product is f i l tered off and washed well with water, boiling ethanol and boiling benzene. The resulting l,4-(dibromomercuri)benzene is obtained in a yield of 4.88 g (38%). The solvent is distilled from the fi ltrate and the remaining sub-stance purified by steam distillation. The distillate gives 11.9 g of ethylmercury bromide, whilst 1.96 g (23%) of p -bromophenylmercury are found in the distillation flask. After recrystall ization f rom benzene, the product isfoundtohave a melting-point of 234-236°C.

The use of mercury fulminate has made it possible to prepare compounds of the type ArHgCNO where Ar = C6H5 or Ci-C10H7 [126],

Organomercury salts prepared with Grignard reagents are listed brief ly below, together with the appropriate references:

RHgCl R = CH3 [25, 53], C2H5 [25, 53], n-C3H7 [25, 53], iso-C3H7 [54, 53], n-C4H9 [25, 53], iso-C4H9 [53], Ii-C5H11 [53], Iso-C5H11 [25, 53], (CH3)3C(CH2)2 [55], I-C10H7CH2 [56], 1-methylcyclohexyl [54], 3-dibenzofuryl [57].

RHgBr R = C H 3 [25], C2H5 [25, 58], n-C 3H 7 [25] , Iso-C3H7 [41], Iso-C4H9

[41], S-C4H9 [41], Iso-C5H11 [25], t-C H11 [28], Ji-CgH13 [25], n-C7H15

[25], (CH3)3CCH2CH2CH2 [59], n-CgH17 [25], S-C8H17 [28], n-C9H19

[41], C12H25 [41], C6H5CH2 [40, 41], C6H5CH2CH2 ^ l L c y c l o - C 6 H 1 1

[41], C6H5 [41], 0 -CH3C6H4 [2, 41], m -CH3C6H 4 [41], P-CH3CgH4

[2, 41, 60], BrHg(CH2)5HgBr [2, 26],

RHgBr.HgCl R = n-C3H7, iso-C3H7, H-C5H11, i so-C 5Hu , n-C6H13) C6H5CH2, cyclo-C6H11, "-CH3OC6H5, P-C2H5OC6H4 [26].

RHgI R = CH3 [25], C2H5 [25], C3H7 [25, 61], iso-C3H7 [61], n-C4H9 [25], iso-C4H9 [25], i so-C 5 H u [25], n-C 6Hn [61],

b) Preparation of Diorganomercury Compounds

Synthesis of D i o r g a n o m e r c u r i e s in Ether (and Tetrahydrofuran)

Synthesis of dimethylmerenry [ 3 ] , Dimethylmercury and other volatile diorganomer-cury compounds containing aliphatic groups are particularly toxic. In view of this, all work with them must be carried out in an efficient fume-cupboard and the apparatus used must be rinsed with chlorine water or bromine water. The Grignard reagent is prepared


f r om 180 g of methyl iodide and 30 g of magnesium in 500 ml of absolute ether, and is f i l t e red through glass wool and heated to boil ing. The f lask is f itted with a wide re f lux condenser, and 100 g of mercur i c chloride is added through this in smal l portions (5-10 g ) in the course o f45minutes. The reaction mixture is then boiled f o r 10 to 12 hours. A f t e r the solution has been cooled, 250 ml of water are slowly introduced through the condenser, the ethereal layer removed and the aqueous layer extracted with 100 ml of ether. The ethereal portions are combined and washed with 15-20 ml of water, dr ied over calcium chloride and careful ly dist i l led through an e f f i c ient column. When most of the ether has thus been removed, the residue is t rans fer red into a smal ler f lask and the disti l lation continued. T o increase the yield, all the ether col lected is redist i l led. Y ie ld : 51-56 g (61-66%); b.p. 89-92°C. The pure product boils at 92°C/740 mm; d ™ ' 1

2.9541; ^ d " ' 2 i.5327. See also the next section f o r the preparation of d imethylmercury [4, 8] with removal of the ether during the reaction. Drehman [62] has descr ibed the synthesis of d imethylmercury containing the isotope 2 0 8 Hg.

The compound [(CH3)3SiCH2]2Hg has been prepared [63] from (CH3)3SiCH2MgCl and HgCl2 in tetrahydrofuran, in a yield of 48.5%; b.p. 49-50°C/0.35 mm; ^ 5 1.4869.

The reaction between mercuric chloride and (CH3)2C6H5SiCH2MgCl in an ethereal medium, carried out by introducing the HgCl2 from a Soxhlet thimble and boiling the reaction mixture for 72 hours, has resulted in [(CH3)2C6H5SiCH2]2Hg in a yield of 71%.

Synthesis of diethylmercury [ 3 ] . The procedure is the same as descr ibed above, except f o r the use of a mechanical s t i r re r . The Grignard reagent is prepared f r om 125 g of ethyl bromide and 25 g of magnesium in 500 ml of ether, and is then mixed with 97 g of mercur i c chloride. Diethylmercury can be separated f r om the ether with-out any dif f iculty, but it is advisable to car ry out the disti l lat ion under reduced pressure, to avoid decomposition. The y ie ld of diethylmercury, boil ing at 97-98°C/125 mm. amounts to 55-59 g (60-63%). At atmospheric pressure, the substance boils at 159°C; d " ' 2 2.4237; n " - 2 1.5399. NOTE : this compound is toxic and an ef f ic ient fume-cupboard must be used.

The yield of diethylmercury depends on the time of heating on a water bath after the introduction of the mercuric chloride, being 50 and 70-85% (on HgCl2) after boiling for 10-14 and 20-48 hours, res-pectively [65]. [Reaction conditions: 550 g of ethyl bromide, 120 g of metallic magnesium, 2,000 ml of absolute ether and 395 g of HgCl2 (the latter is added gradually to the reaction mixture after the removal of the excess Mg); after boiling, the mixture is treated with 5-7% HCl, the ethereal solution is driedover calcium chloride and the diethylmercury is distilled under vacuum [65] (see also [4, 8, 65-67a], and [68] for the preparation of diethylmercury con-taining a radioactive mercury isotope).]

The reaction between mercurous chloride and the appropriate Grignard reagent also leads to diethylmercury, in accordance with the reaction:

2C2H5MgBr + Hg2CI2 (C2H5)2Hg + Hg + MgCl2 + MgBr2

Synthesis of di-n-propylmereury [ 3 ] , By using the technique described f o r the two p re -vious preparations, 98 g of H g C l 2 a re introduced into the Grignard reagent obtained f r om 21 g of magnesium and 108 g of propyl bromide in 500 ml of ether. The y ie ld of dipropyl-mercury boil ing at 82-84°C/19 mm is 47-53 g (45-51%) (at atmospheric pressure the boil ing-point is 189-191°C [41]); d 20 2.0208; nD20 1.5170 (see also [5, 9, 67]). NOTE : this compound is toxic and an e f f i c ient fume-cupboard must be used.



By carrying out the reaction in tetrahydrofuran, Reynolds et al. [15] obtained dipropylmercury in a yield of 75% but gave no further details (see also [6, 75a]).

Di-n-propylmercury is obtained together with n-propylmercury bromide WhenHgBr2 is reacted with an excess of n-propylmagnesium bromide [70]. When HgCl2 and n-propylmagnesium chloride are used, the yield is 65% [71].

Synthesis of di-isopropylmercury [ 3 ] , A Grignard reagent prepared f rom 24.5 g of magnesium and 130 g of isopropyl bromide is reacted with 80 g of HgCl2 under the con-ditions described above. The yield of the product boiling at 119-121°C amounts to 50-51 g (60%); d F 2.0024; n 1 . 5 2 6 3 (see also [67]). NOTE: this compound is toxic and an eff icient fume-cupboard must be used.

Di-isopropylmercury has been obtained in a yield of 87% [67a] from isopropylmagnesium chloride and mercuric chloride, the re-action being carried out in a mixture of ether and tetrahydrofuran.

Synthesis of di-n-butylmercury Cs]. Similar to the previous synthesis, 98 g of HgCl2 are reacted with Grignard reagent prepared from 21 g of magnesium and 134 g of n-butyl bromide. The product has to be distilled twice to f ree it from the butylmercury halides. Yield: 55-56 g (47%); boiling-range 120- 123°C/23 mm Hg; d™ 1.7779; nD20 1.5057. About 42 g of mixed butylmercury halides are recovered f rom the distillation flask. The yields obtained with the ether distilled off amount to 67% [4], 80% [8] and 92% [72] (see also [73]). NOTE: this compound is toxic and an efficient fume-cupboard must be used.

Synthesis of di-s-butylmercury [28] , The Grignard reagent obtained from 12 g of magnesium shavings and 75 g of s-butyl bromide in 500 ml of ether is reacted with 45 g of mercuric chloride. The reaction mixture is refluxed f o r 8 hours, then treated as above. Yield of di-s-butylmercury: 35 g (66%); b.p. 93-96°C/18 mm; d™ 1.763; nD20

1.511 (see also [10, 73]). NOTE: this compound is toxic and an efficient fume-cupboard must be used.

Di-s-butylmercury was obtained in a yield of 20% from the re-action between s-butylmagnesium chloride and HgCl2 indimethoxy-ethane in the presence of benzene [39].

Synthesis of di-t-butylmercury [28] , The Grignard reagent is prepared from 6 g of magnesium and 35 g of t-butyl bromide in 500 ml of ether. T o this is added mercuric bromide (20 g ) in small portions, the addition taking 45 minutes. The reaction is carr ied out, with constant stirring and water-cooling, in a two-necked flask fitted with a st irrer and a drying tube f i l led with calcium chloride (6-8 hours). Water is then added, the ethereal layer separated off, washed with water and dried over calcium chloride. The ether is then allowed to evaporate and the residue is subjected to vacuum distillation. The yield of di-t-butylmercury is 2 g (9%); b.p. 78-82°C at 5 mm. The product is con-taminated with a hydrocarbon;' rf 20 1.749; nD20 1.521. NOTE: this compound is toxic and an eff icient fume-cupboard must be used.

The same method has been used to prepare di-t-pentylmercury [28](yield: 21%, b.p. 80-84°C/5 mm; 1.649; Ti200 1.492) and di-s-octylmercury [28] (from 8 g of Mg, 70 g of s-octyl bromide and 21 g of HgCl2 in 500 ml of ether: yield: 52%; 1.338; n2D° 1.334).

The literature also contains descriptions of the preparation of di-n-pentylmercury [74] (reaction in the presence of decane), di-


dl -pentylmercury [74, 75], dineopentylmercury [31, 42] and di-n-hexylmercury [74] (reaction in the presence of dodecane). The compound (+J-(C3H7CH)CH3(CH2)2Hg and its racemic modification have been obtained from the correspondingGrignardreagent RMgCl and HgCl2 in tetrahydrofuran [75a].

Synthesis of di-n-heptylmercury [ 7 6 ] . The Grignard reagent is prepared f r om 36 g of magnesium and 270 g of n-heptyl bromide, in a y ie ld of 60%. Dry mercur i c chloride (108 g ) is then added to it and the reaction carr ied out with st irr ing and slight heating of the mixture f o r 4 days. Theproduct is then extracted in the usual manner [3], Di-n-heptyl-mercury dist i l ls over at U9-122°C at 0.005-0.01 mm and contains some heptylmercury halide. Y ie ld : 144 g (90%); nD21 1.4935; dQ° 1.474. NOTE : this compound is toxic and an e f f i c ient fume-cupboard must be used.

Di-(5-methylhexyl-2)-mercury has been obtainedfrom 5-methyl-hexyl-2-mercury bromide and 5-methylhexyl-2-magnesium bromide [77].

The literature also contains descriptions of the synthesis of di-n-octylmercury [71], di-n-nonylmercury, di-n-undecylmercury [78], didodecylmercury, ditetradecylmercury, dihexadecylmercury and dioctadecylmercury [9].

Synthesis of dibenzylmercury [ l l , The Grignard reagent is prepared f rom 3.8 g of magnesium and 20 g of benzyl chloride. T o this is added gradually mercur i c chloride (21.4 g), the addition being accompanied by energet ic st i rr ing. The reaction mixture is care fu l ly heated f o r a few hours, then decomposed with water. The ethereal layer is separated f rom the water and crude benzylmercury chloride. A f t e r remova l of the ether, the residue consists mainly of dibenzylmercury, which is then recrys ta l l i z ed f rom ethanol [79] or benzene [60], Y ie ld: 10 g; m.p. I l l 0 C (see also [79]). N O T E : this compound is toxic and an ef f ic ient fume-cupboard must be used.

A better result is obtained when benzylmercury chloride is used instead of HgCl2 [11], 3.8 g of Mg, 20 g of benzyl chloride and 35 g of benzylmercury chloride giving 40 g of dibenzylmercury [11]. Moreover, it is possible to treat, with a sufficient amount of the Grignard reagent only, the admixture of benzylmercury chloride formed at the same time. In this case, the procedure is as follows [80], Finely divided, dry mercuric chloride (35 g) is added, with stirring and cooling, to the Grignard reagent prepared from 40 g of benzyl chloride and 15 g of Mg powder in 500 ml of ether, after removal of excess Mg. The reaction mixture is heated for 5 hours with stirring, and the excess Grignard reagent decomposed with dilute acetic acid. It is then decanted (without washing) and con-centrated until the appearance of crystals, m.p. I l O - I l l 0 C . When the mother liquor of the resulting oily substance is concentrated, a product consisting of benzylmercury chloride is obtained, which is then treated with benzylmagnesium chloride in the manner des-cribed above.

Further preparations include that of dibenzylmercury [10], di-o-chlorobenzylmercury [40], di-/3-phenylethylmercury [10, 42], y-phenylpropylmercury [10], bis(di-/3-methyl-/3-phenylethyl)mercury from neophy!magnesium chloride andneophylmercury chloride [13].



Divinylmercury is obtained from vinylmagnesium bromide and mercuric chloride, the reaction beingcarried out in tetrahydrofuran and giving a yield of 60% [15], 80% [16] and 85% [43]. When mercuric bromide or iodide is UsedinsteadofHgCl2,the corresponding vinyl-mercury halide is also formed [16].

Synthesis of divinylmercury [43 ] , In order to obtain vinylmagnesium bromide under the conditions of the Grignard reaction, the condenser is cooled with solid CO2 and the reaction carried out in an atmosphere of nitrogen and in a medium of tetrahydrofuran to which a few drops of methyl iodide have been added. The tetrahydrofuran has been dis-tilled over lithium aluminum hydride. A solution of 0.77 mole of HgCl 2 in 250 ml of tetrahydrofuran is then added, with energetic stirring and cooling with ice-water, to to the resulting solution of 2 moles of vinylmagnesium bromide in 600 ml of tetrahydro-furan. The reaction mixture is then heated at 55°C for 12 hours, with stirring. After having been cooled to room temperature, the excess Grignard reagent is hydrolysed with about 250 ml of a saturated solution of ammonium chloride. The organic layer is decanted into a distillation flask, the aqueous layer washed with a few portions of ether and the washings combined with the tetrahydrofuran solution. The greater part of the solvent is removed by distillation at normal pressure, the rest by vacuum distillation (with paraffin oil added as a carr ier ) . Yield: 167 g; b.p. 59.5°C/20 mm. NOTE: this compound is toxic and an efficient fume-cupboard must be used.

The preparation of di(perfluorovinyl)mercury from perfluoro-vinylmagnesium iodide and mercuric chloride is carried out at -10 to -50C in ether [81]; b.p. 65-66°C/17 mm.

Dialkynylmercuries have been obtained from the reaction between mercuric chloride and alkynylmagnesium bromide (Iotsich's com-plex) [82]:

2RC = CMgBr + HgCl2 (RC = Q 2 Hg + 2MgClBr

Synthesis of di-/3-phenvIethynylmereury [82]. A solution of 6.0 g of HgCl2 in 25 ml of tetrahydrofuran is added over 5minutes to a warm solution of phenylethynylmagnesium bromide (prepared from 5.1 g of phenylacetylene) in 100 ml of tetrahydrofuran placed in a flask fitted with a reflux condenser. The reaction mixture is refluxed for 1 hour and then treated with an aqueous solution of ammonium chloride. Most of the solvent is distilled off under vacuum and the residue extracted with ether. The ethereal extract gives 6.38 g (84%) of di-/3-phenylethynylmercury in the form of white platelets, m.p. 123-124°C. The product is recrystal l ized from ethanol.

The same method has also been used to prepare di- (oct- l -ynyl )-mercury. The product is obtained in a yield of 69% and in the form of white platelets, m.p. 82-83 °C, low-boiling petroleum ether being used for the recrystallization.

Diallylmercury is obtained from allyl bromide and HgBr2, the reaction being carried out in ether-tetrahydrofuran mixture at room temperature [83].

Synthesis of diallylmercury [83 ] . Mercuric bromide (22 g, 0.061 mole ) in 35 ml of absolute tetrahydrofuran (5-7°C) is added dropwise to a solution of allylmagnesium bromide prepared from 29.4 g (0.242 mole ) of allyl bromide and 5.85 g (0.240 mole) of magnesium in 150 ml of absolute ether (preparation in a current of N 2 ) . A f ter the reac-tion mixture has been stirred for 1 hour at room temperature, 150 ml of a saturated solution of ammonium chloride are added at 5°C. The ethereal solution is dried, the solvent distilled off and the residue distilled under vacuum. The following fractions are


col lected: (1) b.p. 61 °C/3mm, weight 1.1 g; (2) b.p. 71-72.S°C/3 mm, weight 10.5 g; (3) b.p. 74-75°C/3 mm, weight 2.1 g. The total amount obtained of d ia l ly lmercury (b.p. 7 l -75°C/3 m m ) is 12.6 g (73%). The redist i l led product boils at 58-58.5°C/1.5 mm; n o 2 0 l .6309; d ™ 2.3180; MR 43.42.

Dibutenylmercury has been obtained in a yield of 60% from 1-butenyl-4-magnesium chloride and HgCl2 in tetrahydrofuran, the reaction being carried out at 50 0C [83a].

Dicyclopropylmercury has been prepared from cyclopropylmag-nesium bromide and HgCl2 in tetrahydrofuran (yield: 64%) [15].

Synthesis of dicyclopropylmercury [ l S ] , The reaction is carr ied out in an atmosphere of dry nitrogen, Tetrahydrofuran (dist i l led over sodium) and about 3 ml of cyclopropyl bromide are added to 4.6 g (0.19 mo le ) of magnesium in a three-necked 250-ml f lask f itted with a s t i r r e r , a condenser, a thermometer and a dropping funnel. The amount of tetrahydrofuran added is such as to cover the magnesium. The reaction is initiated by careful ly heating the mixture to boil ing in a few minutes. The last 0.19 ml of cyclopropyl bromide dissolved in 100 ml of tetrahydrofuran are added over a per iod of 1 hour at 15-20cC, cooling the reaction mixture with ice-water . T h e mixture is then heated to 50-60°C f o r 1 hour. T o this are then added, dropwise with st i rr ing, 20.6 g (80% of the theo-ret ical amount) of mercur i c chlor ide in 50 ml of tetrahydrofuran and the react ion mixture then gently heated overnight. The viscous residue is f i l t e red and the f i l t ra te extracted with ether, washed a few times with water and dried over magnesium sulfate. The solvent is then dist i l led off on a water bath. The resulting d icyc lopropy lmercury is col lected at 110-112°C/18 mm; yie ld: 13.7 g (64%). NOTE: this compound is toxic and an ef f ic ient fume-cupboard must be used.

Synthesis of dicyclohexylmercury [ 47 ] , Finely divided H g C l 2 (5.5 g, 16.7% of the theoretical amount) is added in smal l portions and with continuous energet ic st irr ing to a solution of 35 g of cyclohexylmagnesium bromide in 100 ml of absolute ether. The mixture is boi led f o r 30 minutes, decomposed with ice and dil. HCl and the ethereal layer dried with sodium sulfate and reduced to one-fourth of its volume by evaporation. As the remainder is cooled to below 0°C in a current of dry air, a small amount of crysta l l ine cyc lohexy lmercury bromide separates out. Th is is f i l t e red off f r om the oi ly substance. Crysta l l i zat ion in the latter is promoted by shaking it with three times its volume of ether. The crysta ls are f i l t e red off at the pump, washed with i ce -co ld water and dissolved in hot ethanol. Water heated to 60°C is then added dropwise to the f i l t e red solution until shaking no longer d isperses the turbidity. The solution is next cooled with a f r eez ing mixture, whilst being v igorously st i rred. The crysta l l ine crop separating out is f i l t e red off at the pump, washed with 50% ethanol and dried at 40°C over phosphorus pentoxide in a dark vacuum desiccator . Owing to appreciable losses during the pur i f i -cation, the y ie ld is only 3 g. Dicyc lohexy lmercury mel ts at 78-79°C to g i ve a trans-parent liquid, f r om which mercury separates out in a few seconds. When kept in a dark vacuum desiccator, the substance turns gray in 2 hours and becomes a black oily liquid in 24 hours. N O T E : this compound is toxic and an e f f ic ient fume-cupboard must be used.

The synthesis of diphenylmercury is described in the next section and in [1, 2, 10, 14, 52, 84-86].

The conditions which favor a good yield of diphenylmercury and other diorganomercuries include the use of an excess of Grignard reagent and the absence of metallic magnesium [52].

Di-m-fluorophenylmercury, di-w-chlorophenylmercury and di-p-chlorophenylmercury have been prepared from the appropriate halogenophenylmagnesium bromides and mercuric halides in a mix-ture of ether and tetrahydrofuran at elevated temperatures [83] (for the preparation of di-p -chlorophenylmercury, see also [88]).



Synthesis of di-m-fluorophenylmercury [83 ] . A solution of 7.47 g (0.0207 mole ) of HgBr 2 in 65 ml of tetrahydrofuran is added at O -S c CtoaGr i gna rd r eagen tp r epa r ed from 10.9 g (0.0623 mole) of m -fluorobromobenzene and 1.52 g (0.0623 mole ) of mag-nesium in 30 ml of absolute ether. After having been heated for 4}4 hours, the reaction mixture is decomposed with 100 ml of a saturated solution of ammonium chloride cooled to 5-10°C. The solvent is removed by distillation and the residue heated with 50 ml of ligroine (b.p. 100-125°C). Yield: 4.31 g (62.6%); m.p. 116-117°C. After two recrystal l iza-tions from ethanol, the compound melts at 117-119°C.

The residue that has not dissolved in ligroine gives 2.26 g (29%) of m-fluorophenyl-mercury bromide, m.p. 234-239°C. The compound obtained after being recrystal l ized twice from ethanol (yield: 1.28 g ) melts at 240°C.

The reaction of pentafluorophenylmagnesium bromide with HgCl2

leads to bis-pentafluorophenylmercury [87].

Synthesis of bis-pentafluorophenylmercury [87] , Pure dry mercuric chloride (6.8 g, 25 mmoles) is placed in the thimble of a Soxhlet extractor and extracted for 1 hour with 200 ml of boiling ether containing a small excess of pentafluorophenylmagnesium bromide (51 mmoles) which is obtained in the usual manner in the presence of iodine and by boiling for 5 hours. The ether is then removed under vacuum and the solid residue sublimed at 130°C/10 mm to give white bis-pentafluorophenylmercury in a yield of 9.8 g (73%). After being recrystal l ized from CCl 4 , the compound is found to melt at 142.3°C.

Use of the appropriate Grignard reagent leads to di-m-methoxy-phenylmercury contaminated with the corresponding salt RHgCl. The pure diorgano compound can be obtained by treating the crude product with sodium iodide in ethanol [89].

The literature also contains descriptions of the synthesis of (P-C6H5OC6H4)2Hg [90] and (p -CH2=CH.C6H4)2Hg [91, 92],

The action of p-bromostyrylmagnesium bromide on mercuric bromide in tetrahydrofuran leads to Hg(P-C6H4CH=CH2)7i where n = 2, 3 or 4 [93].

The compound (P-C6H5Hg)2C6H4 has been prepared [94] from P-(BrMg)2C6H4 and C6H5HgBr.

Wittig et al. [95] have prepared hexameric o-phenylenemercury f rom 6 -phenylenedimagnesium dibromide and mercuric chloride, in a yield of 88% (the Grignard reagent was prepared from pheny-lene-l,2-dilithium and magnesium bromide):


P r e p a r a t i o n of D i o r g a n o m e r c u r y C o m p o u n d s with

R e m o v a l of the Ether b y Distillation

The yield of the diorganomercury compounds can be increased by carrying out the synthesis in the following manner [8].

The Grignard reagent is decanted f rom the unreacted magnesium into a 2 - l i t e r three-necked f lask f i tted with a Soxhlet extractor connected with a ref lux condenser and with a s t i r r e r equipped with a mercury seal, Mercur i c chlor ide (0.5 mo l e ) is placed into the thimble, and the f lask is f i l l ed with 800 ml of ether, and brought to a gentle boil. A f t e r all the mercur i c chlor ide has been extracted f rom the thimble, the extractor is replaced by an upright condenser, and the f lask is gradually heated on a water bath, where its con-tents are kept boil ing f o r 1 hour. Stirr ing is continued throughout the extract ion and the subsequent heating. The bath is then cooled, the ether replaced in the f lask and the con-tents hydrolysed with water or a solution of ammonium chloride containing some ammonia. A f t e r the ethereal layer has been separated, the aqueous layer is twice extracted with 25-ml portions of ether. The ethereal extracts are combined, dried with 10 g of calcium chloride and dist i l led through a suitable column. A f t e r the ether distil lation, the highly volat i le n-butylmercury halide is readi ly and almost entirely removed by f r e e z ing out with i ce -water . F o r methylmercury and ethylmercury halides, this step is not necessary on account of their low volati l i ty.

The following diorganomercuries have thus been obtained, in the yields indicated, f rom 0.5 mole of HgCl2 and the alkyl halide in the amount shown below in parentheses: (CH3)2Hg - 70% (CH3I - 1.15); (C2H5)2Hg - 82% (C2H5I - 1.15); (n-C4H9)2Hg - 80% (n-C4H9Br - 1.15) [4, 8]; (2-CH3C4H8)2Hg - 80% (2-CH3C4HgCl - 1.16) [96]; [(CH3)(CgH5) CHCH2I2Hg - 70% [42].

Synthesis of diphenylmercury [ 1 4 ] . The method descr ibed above is used, with slight modif ications. Owing to the low ether-solubi l i ty of the phenyl der ivat ives of mercury , 300 ml of ether and 500 ml of benzene are added to the phenylmagnesium bromide be fo re the mercur i c chlor ide. Diphenylmercury is extracted f rom the react ion mixture with ch loro form and twice recrys ta l l i zed f r om the latter or f r om ethanol. The des i red product is obtained in the f o rm of f ine needles; m.p. 125°C; y ie ld: 70.6% ( f rom 1.15 moles of phenylmagnesium bromide and 0.5 mole of HgCl 2 ) ,

The yield of diphenylmercury can be increased to 81% by com-bining the same method with boiling of the reaction mixture for 3 days after the introduction of HgCl2 [97].

Diphenylmercury has been obtained in a yield of 85% by carrying out the Grignard synthesis in an atmosphere of nitrogen and sub-sequently replacing ether by xylene [98].

Synthesis of diphenylmercury [ 9 8 ] . Pure ether (100 m l ) and 136 g (0.5 mo le ) of mercur i c chlor ide are added (the latter in portions of 5-7 g ) over a per iod of 30 minutes with heating and thorough mixing and under an atmosphere of nitrogen, to the Grignard reagent obtained f r om 32 g (1.33 g -a t om) of magnesium shavings and 256 g (1.6 mo les ) of f resh ly prepared bromobenzene in 400 ml of absolute ether. The Grignard reagent is prepared in an atmosphere of nitrogen, and compressed nitrogen used to transfer it through a f i l t e r funnel into a f lask f i l l ed with nitrogen. A further 100-ml portion of ether is next added to the reaction vesse l and the mixture heated on a water bath f o r 2 hours, during which some of the ether is removed with nitrogen. A f t e r this, 300 ml of pure xylene a re added and the temperature raised to 75°C. Two hours later, a further 300 ml of pure xylene are added and the heating continued at 90°C f o r 4 hours. Through-out the whole reaction, the mixture is s t i r red vigorously so that no solid matter settles



at the bottom. The flask is then cooled and the contents fi ltered at the pump to separate the mixed solvent from the solid matter. The latter is exhaustively extracted with xylene and then rejected. The liquid phase is cooled and decomposed with dil. HCl and ice. The organic layer is separated, combined with the xylene solution used for the extraction and dried over calcium chloride. The xylene is distilled off under vacuum, leaving behind diphenylmercury in a yield of 150 g (85%); m.p. 121-125°C. After recrystallization from methanol, the compound melts at 125° C.

c) Preparation of Organomercury Compounds by Using Organolithiums

Organomercury compounds can also be prepared with the aid of organolithium compounds, under the same conditions as those de-scribed in connection with the use of organomagnesiumcompounds.

Synthesis of isopropenylmercury bromide [99], (a) Isopropenyl-Iithium is prepared from 2.2 g (0.32 mole) of metallic lithium in 275 ml of dry ether and 20 g (0.16 mole) of isopropenyl bromide in 50 ml of dry ether in an atmosphere of dry nitrogen in a three-necked flask, the reaction being carried out at 5-7°C until all the lithium has gone into solution (higher temperatures lead to lower yields of the product).

(b) Dry mercuric bromide (57 g, 0.158 mole) is added slowly (over 40-45 minutes) and with energetic stirring at 5-8°C to the ethereal solution of isopropenyl-lithium. The reaction mixture is stirred for 2 hours, decomposed by slow addition of 100 ml of a 4% solution of HBr, washed twice with HBr of the same concentration and then with water, and filtered. The resulting crude product weighs 30 g and melts at 164-166°C; after recrystallization from acetone, the melting-point rises to 167°C.

Synthesis of dibenzylmercury [ioo]. Mercuric chloride (1.2 g) is added to 100 ml of a 0. IN solution of benzyl-lithium in ether and the mixture shaken (it turns colorless within seconds). The product is isolated from the ethereal solution; yield: 0.97 g (51%); m.p. I l O - I l l 0 C .

In order to avoid isomerization, the temperature must be as low as 5-8°C (and sometimes even lower) in the preparation of isomeric alkenylmercuries from alkenyl-lithiums and mercuric halides. Thus, cis- and trans -propenyl-lithiums react with mercuric bromide in ether at 5-8°C [101-102] and in tetrahydrofuran at 6-8°C, to give propenylmercury bromide (yield: 80%) of the same configuration as the starting lithium derivative (see also [83a]). Di- cis -propenyl-mercury (yield: 85.5%) and di- trans -propenylmercury (yield: 88%) have been prepared [103] from HgCl2 and the corresponding RLi compounds, the reaction being carried out in tetrahydrofuran at a temperature not higher than 5°C.

Synthesis of di-cis-propenylmercury [103]. Mercuric chloride (7.84 g, 0.0288 mole) in 8 ml of tetrahydrofuran (3-5°C) is slowly added at 3-5°C to an ethereal solution of cis-propenyl-lithium prepared at 5 C from i. 146 g (0.1654 mole) of lithium in 90 ml of dry ether and 10 g (0.0826 mole) of cis-propenyl bromide in 10 ml of ether. The reaction mixture is stirred at room temperature for 2 hours and then decomposed with a saturated solution of ammonium chloride cooled to 0-3°C. It is then washed with cold water and dried over fused calcium chloride. All the solvent is removed by vacuum distillation at room temperature, leaving behind a colorless transparent liquid. Yield: 7 g (85.5%); b.p. 79-80 C/14 mm, nD20 1.5628.


The reaction between irans-propenyl-lithium and cis-propenyl-mercury bromide in ether leads to cis- trans -dipropenylmercury in a yield of 91% [103].

Isopropenylmercury halides have been obtained from the reaction between isopropenyl-lithium and HgBr2 (or HgCl2) in ether at. 5-8°C [99], When HgCl2 is used, not only isopropenylmercury chloride but also the bromide is obtained, owing to the presence of bromide ions in the isopropenyl-lithium solution (prepared f rom lithium and iso-propenyl bromide).

a-Styrylmercury bromide is synthesized [105] from a-styry l -lithium in a yield of 33%. Thepreparationof tu-distyrylmercury has also been described [46], . The reactions of cis-a-stilbenyl-lithium and trans-a-stilbenyl-

lithium with mercuric chloride in ether proceed with rigorous retention of the configuration, cis- cis -di -a-st i lbenylmercury and trans - trans -di-a-sti lbenylmercury being obtained in yields of 50 and 33%, respectively [106], The reaction is carried out in an at-mosphere of nitrogen, at temperatures between -40 and -35 and between -30 and -20 0C.

The reaction between 1,4-dilithiumtetraphenylbutadiene (obtained from diphenylacetylene) and mercuric chloride in ether (boiling for 30 minutes) leads to tetraphenylmercuricyclopentadiene, in a yield of 34% on the diphenylacetylene, and to the compound (C28H20)2Hg2 in a yield of 7% [107],

4-Chloromercuricamphane has been obtained from 4-camphyl-lithiumand HgCl2, the yield being 57% [104]. Dicyclopentenylmercury and dicyclohexenylmercury were obtained when the appropriate pre-parations were carried out in tetrahydrofuran [108].

Synthesis of di-l-cyclopentenylmercury [108 ] . A solution of 103 g (1 mo l e ) of f reshly disti l led 1-chlorocyclopentene in 100 ml of tetrahydrofuran is added dropwise, over 75 minutes, to 13.9 g (2 g -atoms) of lithium wi re in 500 ml of tetrahydrofuran (at -10°C ) . The unreacted lithium is removed and a solution of 68 g (0.25 mo le ) of mercur i c chloride in 150 ml of tetrahydrofuran at 0°C is added. The reaction mixture is s t i r red at room temperature f o r 3 hours and hydrolysed with water at 0°C. The aqueous solution is ex-tracted with diethyl ether, the organic phase combined and dried and the solvent then disti l led off . Recrystal l izat ion f rom ethanol leads to 71 g (85%) of d i - l - cyc lopenteny l -mercury ; m.p. 63.5-64.5°C.

The same method was used to prepare di-l-cyclohexenylmercurv, a colorless viscous liquid; b.p. 122-125°C/0.4 mm; df 1.832; 1.5918 [108].

Di-^-tolylmercury has been obtained from p-tolyl-lithium and HgCl2, the reaction being carried out under the same conditions as described in connection with dibenzylmercury [10, 109].

In the preparation of di-p-dimethylaminophenylmercury, the introduction of mercuric chloride into the reaction mixture was followed by the boiling of the latter for 1 hour (yield: 12%) [109],

A reaction mixture composed of equimolecular amounts of p -Iithiumdimethylaniline and mercuric chloride in ether gives



•p -dimethylaminophenylmercury chloride [110]. B is - (o - , m- and p-trifluoromethylphenyl)mercuries have been

obtained [111, 112] from the corresponding ArLi compounds and mercuric chloride (2:1) in ether. When the reactants are present in a molar ratio of 1:1, the product is ArHgCl [112].

Hexameric o-phenylenemercury has been prepared [95] from phenylene-l,2-dilithium and HgCl2 or metallic mercury in ether, the yield being 72% in the f irst case and 25% in the second (see also Chapter 4).

The use of the same technique and o, o'-dilithiumbiphenyl [113] leads to o-biphenylenemercury having the following tetrameric structure [114]:

Synthesis of tetrameric o-biphenylenemercury [ l l 3 ] , Biphenylenemercury separates out when the following two solutions are mixed together: (a) 1.9 g (0.007 mole ) of HgCl2

in 50 ml of absolute ether and (b) 0.0073 mole of o, o'-dilithiumbiphenyl in ether. After recrystall ization from nitrobenzene, the product is obtained in a yield of 97%; m.p. 335-336°C [110],

o -Biphenylylmercury chloride has been prepared by the reaction between <?-lithiumbiphenyl chloride and mercuric chloride [110].

Synthesis of obiphenylmercury chloride [110] , An ethereal solution (5 m l ) containing 0.9 mmole of sa l t - f ree o-Iithiumbiphenyl is added to a solution of 0.4 g (1.5 mmoles) of HgCl 2 in 20 ml of absolute ether. The ether is distilled off and the residue thoroughly washed with water and crystall ized from ligroine, giving white needles, m.p. 161-162.5°C.

The reaction between 3-biphenylyl-lithium and an equimolecular quantity of mercuric chloride in ether leads to 3-chloromercuri-biphenyl in a yield of 70% [115].

Indenylmercury bromide has been obtained in a small yield from indenyl-lithium and HgCl2 (in the presence of bromide ions) [116], the reaction being carried out in ether and in an atmosphere of nitrogen. Attempts at preparing di-indenylmercury anddifluorenyl-mercury from indenyl-lithium (fluorenyl-lithium) and HgCl2 under


the same conditions have ledonly to metallic mercury and di-indenyl (difluorenyl) [116].

3-Pyrenyl-lithium shaken with mercuric chloride for 12 hours in ether, gives di-3-pyrenylmercury in a yield of 80% [117]. 3,4-Ben-zodiphenylenemercury is obtained in a yield of 65.9% from HgCl2

and l-(2-lithiumphenyl)-2-lithiumnaphthalene [118]:

Bis-a,a -pyridylmercury has been obtained [119] in a small yield from 2-pyridyl-lithium and HgCl2 in ether at -20°C.

The product obtained from the reaction between benzylacetylene and lithium amide in liquid ammonia interacts with phenylmercury chloride to give C6H5HgC=C1CH2C6H5 [120].

The reactions between organolithiums and metallic mercury lead to organomercury compounds in very small yields. Thismethod has been tested in the preparation of di-n-butylmercury (incyclohexane) [121], dibenzylmercury (in ether, agitation for 15 hours) [100] and diphenylmercury (in ether, 94% hours) [122, 123].

The reaction between a 5% ethereal solution of 1,5-dilithiumpen-tane and excess mercury in an atmosphere of argon (stirred reaction mixture) results in cyclopentamethylenemercury (U-C5H11)2Hganda mixture of polymeric products [- (CH2 )5-Hg-]n , possibly having a cyclic structure [124]. When boiled in benzene for a long period, the latter can be converted into the dimer.

A similar method has been used for the preparation of organo-mercury compounds by the reaction of mercury with the &>,&/-dilithium derivatives of butane, hexane and decane [124],

Like the reactions between organomercuries and organomag-nesiums (see above), the organic radicals may be exchanged between organomercury and organolithium compounds:

R2Hg + 2R'Li 2RLi + RsHg

where, for example, R = p -ClC6H4 and R' = n-C4H9 [125],

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(1965).

CHAPTER 3

Preparation of Organomercury Compounds from the Organic Compounds of the

Remaining Light Metals

The organic compounds of metals belonging to groups I-III of the periodic system have also been suggested for the preparation of organomercury derivatives. Syntheses making use of the organic compounds of sodium and silver are nontypical and have been used only in two special cases. One of the oldest routes to the organo-mercury compounds, via the organic derivatives of zinc, is today almost wholly abandoned. Synthesis of the aliphatic organomercury compounds from organo-aluminums, so far tried only on a small number of examples (some Alk2Hg, Ar2Hg and AlkHgX), appears to hold some promise.

a) Formation of the Organomercury Compounds from the Organic Derivatives of

Sodium and Silver

Dicyclopentadienylmercury has been made by the reaction of cyclopentadienylsodium with HgCl2 [1].

Preparation of dicyclopentadienylmercury [ 1 ] . Sodium pieces (3.5 g) and 100 ml of tetrahydrofuran are treated with 13 ml of cyclopentadiene. At the end of the evolution of hydrogen, the solution is cooled to -30°C and treated with a solution of 13.5 g HgCla in 150 ml of tetrahydrofuran, followed by 1 ml of water at 0°C. The solvent is then driven off under vacuum, the residue extracted with ether and the ethereal extract washed with water and dried. Cooling to -78°C gives 3 g (yield: 20%) of the desired product. Crystall ization in this way from ether results in pale yellow crystals decomposing at 83-85°C (beginning at 60°C).

A polymer was obtained from the reaction of bi s-(sodio acetyl-enyl)benzene with mercuric chloride [ la] .

Treatment of the double salt Ag2C2.6AgNO3 with a solution of mercuric nitrate in nitric acid yielded the compound HgC2.3AgNO3

[ 2 , 3 ] .

40

PREPARATION FROM COMPOUNDS OF OTHER LIGHT METALS 41

b) Preparation of Organomercury Compounds from the Organic Derivatives of Zinc

The interaction of mercury and organomercury with fully sub-stituted organozincs can be expressed by the following reactions

No mixed organozinc derivatives RZnX have been used for the preparation of the organomercury compounds. Reaction (1) has been studied on the synthesis of diethyl- [4] and dimethylmercury [4, 5]. Diethylmercury has also been prepared, by Reaction (2), from allylmercury iodide and diethylzinc [6, 7]. Frankland ob-tained diethylmercury [8] from methylmercury iodide and diethyl-zinc according to Reaction (2), but an attempted synthesis of methylethylmercury from (CH3)2Zn and C2H5HgX gave a mixture of diethyl- and dimethylmercury [4], Thismethodisnow practically abandoned in favor of a synthesis viathemore convenient and more easily accessible organomagnesium derivatives.

However, Gaudemar [9] recently prepared a series of compounds RHgX (where X = C l or Br) with R = CH2=CH-CH2-, C6H5CH2-, C6H5C = C-CH2- and C6H5CH=C=CH-CH2- by using derivatives R2Zn and tetrahydrofuran. According to Gaudemar, for these R groups the corresponding Grignards RMgX are more difficult to obtain.

Synthesis of allylmercury chloride [ 9 ] , The reaction is carr ied out under nitrogen in a f lask f i tted with a 200-300-rpm s t i r r e r , a condenser, a nitrogen inlet, a thermometer , and a dropping funnel with the stem pulled out into a capi l lary . Al l tubes connecting the system with the external atmosphere are closed off by CaCl2 tubes.

The reagents a re 16.3 g (0.25 mo l e ) of zinc, obtained by machining a smal l p iece of e lectro lyt ic zinc on a lathe and mi l l ing the resulting 0.1-mm-thick shavings into f i l ings about 1 mm in length, 30 g (0 .25mole ) of al lyl bromide and 125 ml of tetrahydrofuran. The zinc is covered with a little solvent, a few grams of the al lyl bromide are added and the reaction is started by heating. At the end of boiling, the mixture is cooled in an ice-bath and, keeping the temperature at 10°C, the remaining al lyl bromide in tetrahydrofuran added drop by drop over a period of 2 hours. A c lear ye l l ow-green solution of dial ly lz inc is obtained. The quantity of zinc entering into the reaction does not exceed 0.5-0.8 g.

A solution of 15 g (0.055 mo le ) in 20 ml of tetrahydrofuran is added at room tempera-ture to 0.05 mo le of the above solution of dial lylz inc, the mixture s t i r red f o r 1 hour and then evaporated down and treated to a dropwise addition of 500 ml of 2% H2SO4. The tetrahydrofuran and the inorganic salts pass into solution and the organomercury com-pound is precipitated. The upper layer is decanted and the precipitate washed thoroughly with water, then rapidly with cold alcohol and f inal ly dr ied in vacuum. The weight of the crude mater ia l is 11.5 g; yie ld: 83%. This product is already reasonably pure (m.p. I l O 0 C ) and a f ter recrysta l l i zat ion f r om alcohol melts at I l l 0 C .

The same procedure was used to obtain allylmercury bromide (m.p. 1250C; yield: 69%), benzylmercury chloride (m.p. 110°C; yield: 83%) and bromide (m.p. 118°C; yield: 75%), phenyl-3-propyn-2-ylmercury chloride (m.p. 108°C; yield: 77%) and bromide (m.p. 114°C; yield: 68%) and phenyl-l-buta-l,2-dienylmercury chloride (m.p. 122°C; yield: 60%) and bromide (125°C; 53%).

R2Zn + HgX2 R2Hg + ZnX2

R2Zn + R'HgX R2Hg + R'ZnX

( 1 )

(2)



e) Preparation of Organomercury Compounds from the Organic Derivatives of Aluminum

The organic compounds of mercury can be obtained by the action of the organic compounds of aluminum on mercury salts and, in one known case, on metallic mercury itself. The reaction is carried out by heating in inert solvents (hydrocarbons, dichloroethane, ether).

Good yields of RHgCl (R = CH3 and C2Hjbutnot the higher alkyls) are obtained from mixed organoaluminum compounds such as RAlCl2

[10] or R2AlCl [10], or from their mixture [11-13] RAlCl2+R2AlCl and mercuric chloride. The reactions are carried out in benzene, hexane, or dichloroethane, with moderate heating or even at room temperature.

Ethylmercury chloride has been obtained in a 91% yield from mercuric chloride and C2H5AlCl2lNaCl (a side product from the preparation of the catalyst for the low-pressure polymerization of ethylene) in benzene, xylene and other nonpolar solvents [10, 13, 14]. The advantage of the above complex as the starting com-pound is that it is not inflammable, so that the reaction need not be carried out under an inert atmosphere.

Preparation of ethylmercury chloride [ lO] , HgCl2 (112.8 g, 0.42 mole ) and 180 ml of xylene are placed in a three-necked flask fitted with a st i rrer , a dropping funnel, a reflux condenser and a thermometer, under conditions excluding atmospheric humidity. A solution of 76.8 g (0.49 mole) of C 2 H 5 AlC l 2 .NaCl in 180 ml of dry xylene is then added, drop by drop, with vigorous stirring, maintaining the temperature at 45-50°C. At the end of this addition, the solution is st irred for 30 minutes and set aside for 12 hours at room temperature. With vigorous shaking and, if necessary, additions of ice to keep the tem-perature of the hydrolysis below 40°C, 300 ml of water are then poured in. The initial addition of water must be slow. The white precipitate of ethylmercury chloride is f i l -tered off, washed with water and a small volume of alcohol and dried; m.p. 192-193°C, yield: 100.5 g (91%).

Depending on the relative proportions of the reagents and the nature of the anion in the mercury salt, the trialkylaluminums and mercury salts give either Alk2Hg [15, 16] or AlkHgX [10, 13, 16]. To obtain the Alk2Hg, the Alk3Al must betaken in excess; mercuric acetate is better than a halide.

Organomercury derivatives containing alkyl groups higher than ethyl can be obtainedfrom Alk3 Al, conducting the reaction in hexane, ether [16], or benzene [10], with moderate heating or at room tem-perature. Thus, tri ethyl aluminum and HgBr2 (in hexane) gave a 58.6% yield of diethylmercury. Under the same conditions, a 79% yield of di-n-propylmercury was obtained from the ether complex of tri-n-propylaluminum and mercuric acetate. The reactions of the tripropylaluminum-ether complex, and of the tri-isobutyl-aluminum, with mercuric bromide in ether resulted in mixtures of R2Hg and RHgBr. Finally, isopropylmercury bromide has been made from the ether complex of tri-isopropylaluminum and mer-curic bromide [16],

PREPARATION FROM COMPOUNDS OF OTHER LIGHT METALS 43

Preparation of diethylmercury [16]. Triethylaluminum (11.4 g, 0.1 mole) in 50 ml of hexane are added, at 40-50°C, to a suspension of 27. I g (0.1 mole) of finely powdered HgCl2 "in 50 ml of hexane, under a current of nitrogen and with vigorous stirring. The mixture is stirred for a further 2 hours at 40°C and then decomposed with ice and NaHCC>3. The aqueous layer is extracted with ether anddried over CaCl2 . Evaporation of ether and hexane gives 15.0 g (yield: 58.5%) of diethylmercury; b.p. 95-96°C/90 mm; nn22 1 5400; d.20 1.4658.

4

The product of the interaction of triethylaluminum with ethylene gave with mercuric chloride in cyclohexane (1 hour at 80°C) a solid compound H(C2H4)n HgCl, where n = 4-5 [17].

Diphenylmercuryhasbeenobtained by shaking triphenylaluminum with metallic mercury in xylene for 20 hours [18]. The course of this reaction is independent of whether the operations are carried out in air or under nitrogen.

Preparation of dialkylmercury compounds by electrolysis of M(AlAlk3R) (M = K, Na) on a mercury anode has been described [19]. Diethylmercury was obtained in this way in a yield of 60%.

During the action of aluminum carbide on aqueous HgCl2, the latter becomes methylated [20], According to Hilpert and Dittmar [20], the reaction proceeds with an intermediate formation of mer-curic carbide. A 30% yield of methylmercury chloride was obtained when the reaction was carried out in 10% HCl with an excess of the mercuric chloride; dimethylmercury was formed in a solution in which a neutral reaction was maintained by careful additions of hydrochloric acid.

LiAl(C6H5)4 (without being separated from the mixture in which it is made) in ether reacts with mercuric chloride to give C H HgCl[23].

Preparation of methylmercury chloride [20], 15 g of aluminum carbide are added, in very small portions and with vigorous shaking, to a solution of 25 g of mercuric chloride in 130 g of 10% HCl. Considerable evolution of heat takes place and leaflets of methyl-mercury chloride are rapidly precipitated. The temperature is maintained at 90°C. The product is steam-distilled. The yield is 30%; m.p. 170°C (see also [21, 22]).

Bibliography

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la . V. V. Korshak, A. M. Sladkov and L. K. Luneva, Izv. Akad. Nauk SSSR, Otdel. khim. Nauk, 728 (1962).

2. Brit. Pat. 616,318 (1949); Chem. Abstr. 43, 5175 (1949). 3. U. S. Pat. 2,474,869 (1949); Chem. Abstr., 43, 7670 (1949). 4. G. B. Buckton, Justus Liebig's Annln Chem., 109, 219 (1959). 5. V. H. Dibeler, Analyt. Chem., 27, 1958 (1955). 6. H. Krassowsky, Ber. dt. chem. Ges., 3, 625 (1870). 7. A. Oppenheim, ibid., 4, 671 (1871). 8. E. Frankland, Justus Liebig's Annln Chem., 11, 57 (1859). 9. M. Gaudemar, Bull. Soc. chim. Fr . 974 (1962); C. r. hebd.

Se'anc. Acad. Sci., Paris, 254, 1100 (1962).


10. Z. Eckstein, W. Dahling, B. Hetnarski and S. Pasynkiewicz, Przem. chem., 39, 225 (1960).

11. U. S. Pat. 2,473,434 (1949); Chem. Abstr. 43, 7953 (1949). 12. German Pat. 954,878 (1956); Chem. Abstr. 53, 11226 (1959). 13. Z. Eckstein, W. Dahling, B. Hetnarski and S. Pasynkiewicz,

Bull. Acad. pol. Sci., Ser. Sci. chim., 161 (1960). 14. A. Swirska, J. Kotler-Brajtburg, W. Dahling and S. Pasynkie-

wicz, Przem. chem., 39, 371 (1960). 15. Brit. Pat. 820,146 (1959); Chem. Abstr., 54, 6550 (1960). Ger.

Pat. 1,048,581 (1959); Chem. Abstr., 54, 24,401 (1960). 16. L.I. Zakharkin and O. Yu. Okhlobystin, Dokl. Akad. Nauk SSSR,

116, 236 (1957); Izv. Akad. Nauk SSSR, Otdel. khim. Nauk, 1942 (1959) USSR Pat. 110,947 (1958); Chem. Abstr., 52, 18,217 (1958).

17. Brit. Pat. 763,826 (1956); Chem. Abstr. 52, 1203 (1958). 18. T. G. Brilkina, Uchen. Zap. gorkov. gos. Univ., 24, 165 (1953). 19. USSR Pat. 132,136 (1960); Referat. Zh., Khim., 9L98 (1962). 20. S. Hilpert and P. Dittmar, Ber. dt. chem. Ges., 46, 3738 (1913). 21. H. Gilman and R. G. Jones, J. org. Chem. 10, 505 (1945). 22. Ger. Pat. 554,513 (1931); Chem. ZentBl., II, 2229 (1932). 23. T. G. Traylor, Chemy Ind., 1223 (1959).

CHAPTER 4

Synthesis of Organomercury Compounds with the Aid of Sodium, Lithium,

Potassium and Cadmium Amalgams

Whereas metallic mercury reacts slowly with only a few halogen derivatives of the hydrocarbons, sodium amalgams enter readily into interactions with alkyl halides, even in the cold, and with aryl halides on heating, according to the reaction

2RX + Na2Hg -> R2Hg + 2NaX

This is one of the oldest methods of synthesizing organomercury derivatives, discovered by Frankland [1], and is still used because, in contrast to mercuration or syntheses involving replacement of acidic groups by mercury, it leads directly to fully substituted aliphatic, alicyclic, some aliphatic-aromatic and aromatic organo-mercury compounds. In general, this method has the same range of application as the synthesis of R2Hg via organomagnesium de-rivatives, but sometimes results in higher yields, and is more suitable for the production of these compounds on a large scale.

In the aliphatic series, this method has been used to obtain the mercury derivatives of hydrocarbons both with primary radicals (the series dimethylmercury to diamylmercury, dioctylmercury and the iso-compounds di-isobutylmercury and di-isoamylmercury) and with secondary ones (di-isopropylmercury [2]), in yields re-acting 80-85% (diethylmercury; the derivatives with secondary radicals are obtained in lower yields). Organomercury derivatives of /3-carboxylic acids (but not a -carboxylic), which cannot be pre-pared via a Grignard reagent, have also been made [3]. The method can be applied to the alicyclic series, where dicyclohexylmercury was prepared in this way from cyclohexylbromide. Unexpectedly, cyclohexyl iodide gives with sodium amalgam not dicyclohexylmer-cury but cyclohexylmercury iodide. Among the aliphatic-aromatic halides, dibenzylmercury cannot be prepared in this way; the inter-action of benzyl bromide with sodium amalgam results only in a Wurtz reaction, with the formation of dibenzyl. On the other hand, a very small yield of di-&>-styry!mercury has been thus obtained.



Cadmium amalgam (and, rather less frequently, copper and silver amalgams) are used in special cases, e.g. in the synthesis of the perfluoroalkyl mercury derivatives.

Applied to the aromatic series mainly in the work of Otto [4, 5] and Michaelis [6, 7], the amalgam synthesis has been used widely to obtain the organomercury derivatives of hydrocarbons, phenolic ethers and dialkylanilines.

Dihalogenated hydrocarbons (o -substituted aromatics with and without aliphatic side chains, 1,4-di-iodo- [8, 9] and 1,4-dibromo-butanes, 1,5-dibromopentane and 1,6-dibromohexane [10], but not their lower homologs in the aliphatic series) react with sodium amalgam to give heterocyclic compounds (with Hg as the hetero-atom), which are polymeric in the aromatic, and possibly in the aliphatic, series.

The reactions of organic halides with sodium amalgam are smooth and result in satisfactory yields of the organomercury only in the presence of catalysts such as ethyl or methyl acetates, or, in certain cases, ethyl chloroformate. On the example of di-isobutylmercury, Lewis and Chamberlin [11] showed that other carbonyl compounds also catalyze the above reactions, though to a smaller extent (for example, acetone, isovaleraldehyde or acetic anhydride).

According to Giral [12], the replacement of ethyl acetate by ethyl formate or acetone increases the yield of diethylmercury in its synthesis from ethyl iodide and sodium amalgam, but the use of methyl or ethyl formate, or of acetone, instead of methyl acetate, reduces the yield of dimethylmercury from methyl iodide and sodium amalgam.

The catalyst generally amounts to a fifth to a tenth of the volume of the organic halide, but in the reactions of ethyl bromide [13] and isobutyl iodide [11] it was demonstrated that the best yields of the dialkylmercury are obtained when the alkyl halide and ethyl acetate are in a molar ratio of 2:1. Alcohol in the ethyl acetate reduces the yield of R2Hg, whereas a small admixture of acetic acid has no effect.

The starting organic halides in this method are bromides or iodides. The chlorides do react, but the yields are very low. The sodium amalgam is generally used in a 100% excess over the theoretical amount. The reactions of the alkyl halides are carried out with dilute liquid amalgams; a more concentrated amalgam is needed for the diarylmercury derivatives. Alkyl halides react with sodium amalgam even in the cold (best on cooling to 0-5°C) and the aryl halides on heating to 140-150°C. Inmost cases the reaction requires several hours, though with isobutyl iodide [11] stirring for 45 minutes after the end of the amalgam addition did not increase the yield.

Vigorous shaking or stirring is necessary if good yields are to be obtained.

SYNTHESES WITH Na, Li, K AND Cd AMALGAMS 47

The synthesis may be summarized in the following general out-lines. The halide, mixed with the solvent (or without the latter) and with ethyl acetate, is shaken or stirred with an excess of sodium amalgam in the cold (R = Alk) or with heating (R = Ar) , in a round-bottom flask fitted with a reflux. After the end of the reaction (usually several hours), water is added to dissolve the sodium halide and the R2Hg is separated off (the diarylmercury compounds are recrystallized and the dialkyl compounds steam-distilled).

It has been shown [14] that the reaction can also be conducted without a preliminary preparation of the amalgam.

Synthesis of dimethylmercury [ 1 ] . Methyl iodide (10 parts by weight), methyl acetate (1 part ) [15] and 0.2% sodium amalgam [16] (1.2 g -a toms of Na per mole of CH3I ) are added in turn to a round-bottom f lask f itted with a ref lux container. The mixture is shaken and cooled with water. The reaction is completed when the temperature fa l ls of and when boil ing of a few drops of the c l ear liquid with nitric acid g ives only traces of iodine. If so much Nal precipitates that the mixture becomes too thick f o r proper contact with the amalgam, part of its most volat i le component should be dist i l led off on a water bath and left to react with f resh amalgam. At the end of the reaction, the contents of the f lask are mixed with water and disti l led on an oil bath (<160°C) . A f t e r separation of the aqueous layer , the dist i l late is shaken up with alcoholic KOH to remove methyl acetate, washed with water and dried by disti l lation; b.p. 92°C.

The yield of dimethylmercury from methyl iodide and 0.4% sodium amalgam is 60% [77], and that from methyl bromide and 0.5% amalgam (3^-5 hours at -3 to -5°C, with stirring) 50-70% [17].

In the preparation of dimethyl(diethyl)mercury, the alkyl halide can be replaced by dimethyl(diethyl) sulfate [18] (see, however, [12]). Only one of the methyl groups of dimethyl sulfate enters into the reaction.

Preparation of dimethylmercury from dimethyl sulfate and sodium amalgam L l 8 ] , Fresh ly prepared 0.5% sodium amalgam (2 kg, 1 g-atom N a ) are shaken in a thick-walled 1 - l i t e r vesse l with 55 g of oxygen- f ree dimethyl sulfate (1 mo le ) and 10 g of methyl acetate. Ve ry l i tt le shaking is needed at f i r s t because the reaction proceeds rapidly and exothermical ly (60-70°C). The mixture is shaken until complete sol idi f icat ion takes place. The vesse l is then careful ly opened (slight pressure ) , the salt d issolved by adding 200 ml of water and the contents slowly steam-dist i l led, cooling the r e c e i v e r with a mixture of water and ice. The yie ld of the crude product is 38 g (75%). The mater ia l is puri f ied as in the synthesis f r om CH 3 I (cf. [12]).

Preparation of diethylmercury from ethyl bromide and sodium amalgam [ I S ] . Sodium amalgam (0.5%), taken in a 20% excess , is placed in a f lask f itted with a powerful mecha-nical s t i r r e r . A mixture of ethyl bromide andethyl acetate (in a molar rat io of 1:0.5) is added with st irr ing, in three portions, over 1-2 hours. A f t e r the reaction mixture has been cooled with ice to O0C and st i r red f o r 5 -6 hours, diethylmercury is steam-dist i l led out of the reaction mixture. The aqueous layer is separated off and the required product dried over C a C l 2 and disti l led under vacuum. Y ie ld : 75-80%; b.p. 159°C; d i3 2 42346; n " 1.5599.

Dimethylformamide (0.01-0.05 mole) has been used to catalyze this reaction [19].

Unexpectedly, CCl3Br and 0.5% Na amalgam give CCl3HgBr [78]. The yield of diethylmercury from ethyl chloride and sodium

amalgam does not exceed 24% [13].



Preparation of diethylmercury from ethyl iodide and sodium amalgam [20]. Over a period of 24 hours, 2900 g of 1% sodium amalgam (1.25 g-atoms Na) is stirred with 156 g (1 mole) of ethyl iodide and IOml of ethyl acetate in 1 l i terofpetro leum ether. Water is then added to the liquid contents of the flask (black, owing to a colloidal pre-cipitate of mercury), the mixture stirred for 30 minutes to decompose the amalgam and the petroleum ether layer decanted off, washed, dried and distilled. Yield: 60-70%.

A 67% yield of diethylmercury was obtained from C2H5I and 0.2% sodium amalgam in the presence of ethyl acetate [21]. The yield of diethylmercury is increased if formyl acetate or acetone are used instead of the ethyl acetate in this reaction [12].

For the preparation of diethylmercury, see also [1,15, 16, 21a-24].

Preparation of di-n-propylmercury [17] . A mixture of 45 kg of 0.5% sodium amalgam, 936 g of n-propyl bromide and 250 g of ethyl acetate is charged into iron apparatus fitted with an anchor-propeller st irrer working at 400 rpm and stirred for 4 hours, cooling the vessel in ice-water. At the end of the reaction, dipropylmercury is steam-distilled, washed with water, dried over CaCl2 and distilled under vacuum; b.p. 89-91°C/ 15 mm, d2.0201; nD2° 1.5162; yield of pure product: 791 g (69%).

For the preparation of this compound, see also[2, 25, 26], Di-isopropylmercury was obtained in a yield of 8-10% [2] from

isopropyl bromide and 7% sodium amalgam (5-6 hours, in the pre-sence of ethyl acetate), and a mixture of di-n-butylmercury and n-butylmercury iodide [27] from n-butyl iodide and sodium amalgam (the latter's concentration and the reaction conditions were not re-ported).

A synthesis of di-n-butylmercury from n-butyl iodide and 0.4% sodium amalgam was carried out with a yield of 64% [22]. The de-pendence of the yields of dialkylmercury derivatives on the nature of the halogen in the alkyl halide and the amalgam concentration was studied on the example of the synthesis of di-n-butylmercury [17]. The best yields (up to 82%) wereobtained from n-butyl iodide, using the conditions described above for di-n-propylmercury, whereas the best yield from n-butyl bromide was 70% and from butyl chloride not more than 17%. Considerable Wurtz reaction occurs if the amalgam concentration exceeds 0.5% [17].

Preparation of di-isobutylmercury from isobutyl bromide [ l 7 ] . The halide (550 g), 21 kg of 0.5% sodium amalgam and 170 g of ethyl acetate are reacted under the conditions described above for di-n-propylmercury, continuing the st irr ingfor4 hours. Di-isobutyl-mercury is then steam-distilled out of the mixture, washed with water, dried with CaCl2 and distilled under vacuum; b.p. 108-109°C/25 mm; J420 1.7670; n D x 1.4969; yield: 393 g (63%). About 45 g of 2,5-dimethylhexane are also obtained in the distillation of di-isobutylmercury; b.p. 107-109°C/752 mm; ^420 0.6990; nD20 1.3995. (See also [11, 22, 28-33].)

Synthesis of di-isobutylmercury from isobutyl iodide [ 11]. Amixture of 31ml (0.294 mole) of the halide and 14.3 ml (0.147 mole) of ethyl acetate is placed in a 2-liter round-bottom flask fitted with a dropping funnel closed off by a CaCl2 tube, a thermometer, a reflux condenser and a stirrer. The mixture is copied with ice to O0C. Amalgam (0.25%), prepared from 0.591 mole (13.6 g) of Na and 27.2 moles (5440 g or 400 ml ) of Hg is then added, keeping the temperature below 15°C. When all the amalgam has been added (about 45 minutes), ether is added to the mixture, excess sodium decomposed with water and


the ethereal l ayer is separated off, dr ied with CaC l 2 and disti l led. Di- isobuty lmercury dist i l ls between 202 and 206°C, better in vacuum ( for the physical constants, see above) Y ie ld : 56.5%.

Di - n (?) - amylme rcu r y was obtained from n(?)-amyl chloride and 2% sodium amalgam [20].

Preparation of di-isoamylmercury [ 1 7 ] . The reaction is carr ied out, under the condi-tions described f o r d i -n-propy lmercury , with 450 g of isoamyl bromide, 17 kg of 0.5% sodium amalgam and 130 g of ethyl acetate. The reac tor is cooled with ice-water . The mixture is s t i r red f o r 4 hours, the product steam-dist i l led and the resulting oil dried and fractionated under vacuum. Y ie ld : 258 g (50%) of d i - i soamylmercury ; b.p. 122-125°C/ 16 mm; d 2 0 1.6381, nD 2 0 1.4981. About 100 g of 2,7-dimethyloctane are obtained; b p 60°C/15 mm; d2a 0.7782; nD20 1.4074.

For the preparation of this compound, see also [1, 22, 29]. Frankland and Duppa [1] failed to obtain an organomercury com-

pound from hexyl iodide and sodium amalgam. Di-n-octylmercury was made by the interaction of n-oetyl iodide

with a very dilute sodium amalgam [34], and a cyclic compound containing two atoms of mercury in the ring was obtained from 1,4-dibromobutane and sodium amalgam [10].

Preparation of 1,6-dimercuracyclodecane [ 1 0 ] . A mixture of 450 g (0.2 mo l e ) of 1% sodium amalgam, 15.3 g (0.07 mo l e ) of 1,4-dibromobutane, 3 ml of ethyl acetate and 25 ml of benzene is shaken f o r 36 hours at 70°C. The cooled mixture is shaken up with 25 ml of water, the benzene layer separated off and the residue washed with 25 ml of benzene. The combined benzene extracts are f r eed f r om the solvent by evaporation. The residual oil (10.79 g ) becomes semi-so l id on washing with cold ether, and was crysta l l i zed f r om a mixture of ether and benzene. M.p. 44-45.2°C.

A compound probably having an analogous structure was obtained from 1,4-di-iodobutane [8, 9],

Shaking of 1,4-di-iodotetraphenylbutadiene for 19 hours at room temperature with 0.73% sodium amalgam in toluene resulted in tetraphenylmercuricyclopentadiene (yield: 65%) and a compound (C28H20)2Hg [35].

1,5-Dibromopentane reacts with 1% sodium amalgam giving polymeric and cyclic compounds containing mercury in the ring [36] (see also [10]).

Mercuricycloheptane has been prepared by shaking 1,6-dibromo-hexane and 1% sodium amalgam for 1 day in a mixture of ethyl acetate and benzene [10].

Preparation of mercuri-bis-/3, /3'-propionic acid [ 3 ] . T o a solution of I O g o f e t h y l ,3-iodopropionate in twice its volume of ether (cooled with snow and salt) a re added 220 g of 0.5% sodium amalgam (1.1 g-atoms Na ) in small portions. Heating is avoided. The mix -ture is shaken f o r 2 hours to complete the reaction, wate^ added (to d issolve the NaI ) and then ether. The ethereal layer is separated off and f r eed f r om the solvent and the residual oil hydrolysed by vigorous shaking with 70 ml of IN NaOH to complete dissolution. This last operation requires 7-8 hours at 15-20°C. The solution is then cooled to 0°C and 16 ml of 5N H2SO4 added. The co lor less , slowly precipitating, crysta ls of the required product are f i l t e red off a f ter 1 hour in i ce -water and washed with a l i tt le cold water. The opti-mum yield is 2.1 g (27%). A f t e r recrysta l l i zat ion f r om 20 volumes of water (avoiding heating), the melt ing-point becomes 147-148°C.



An analogous procedure was used [37] to obtain methyl mercuri-bis-propionate, and hence the free acid itself (yield: 29%).

The method is inapplicable to the a-halogenated fatty acids [38]. Interaction of 1,2,3,4-tetrabromocyclobutane with a 50% excess of

0.5% Li amalgam in absolute ether (shaking for 15-20 hours) resulted in a bromine-free unstable mercury compound [39]. Na amalgam gives cyclohexylmercury iodide with cyclohexyl iodide [40] and the normal product, dicyclohexylmercury, with cyclohexyl bromide [41].

3,3-Mercuri-bis-menthane has been prepared in 35% yield (see .[42]) by shaking Z-menthyl bromide for 11 hours with 1% sodium amalgam.

The following aromatic organomercury compounds have been made by using more concentrated amalgams and heating the mix-tures: diphenyl [5, 6, 43-45] (also diphenylmercury labeled with 14C) [46], di- o-tolyl [5, 47], di- m-tolyl (2.7-3% amalgam atl80°C) [17], di-o -xylyl (chloroformate catalyst) [48], di-m-xylyl (2% amalgam, 12 hours at 140-150°C) [49], d i -?-xyly l (110°C, chloroformate catalyst) [50], dimesityl [7, 51], dipseudocumyl [7], di-p-propyl-phenyl (both in the presence of chloroformic ester and by the action of 1% sodium amalgam in xylene in the presence of ethyl acetate) [52], dicimyl [53, 54], dipentamethylphenyl (chloroformatecatalyst) [54], bis-m-diphenylenephenyl [7], di-a-naphthyl (4% sodium amal-gam, 18 hours at 140-150°C) [4,55-57] anddi-,S-naphthyl (4% amal-gam, 24 hours at 1400C) [55].

Synthesis of diphenylmercury [43 ] , A 900-g amount of 3% sodium amalgam, 180 g of bromobenzene, 200 ml of dry toluene (dry xylene) and 10 ml of ethyl acetate are placed in a 1- l i ter round-bottom flask fitted with a reflux condenser and refluxed, with frequent shaking, for 12 hours at 130°C (oil bath).

The mixture is transferred hot onto a fluted f i l ter paper, trying to leave the mercury in the flask. The diphenylmercury is extracted with 600 ml of boiling benzene, over about 10 hours, and the resulting benzene solution vacuum-evaporated on an oil bath whose temperature is raised at the end to I lO c C. The solid residue is washed with ice-cold 95% alcohol until it becomes colorless (four 50-ml portions are generally sufficient). Yield: 65-75 g (32-37%); m.p. 125°C.

Improved synthesis of diphenylmercury [58]. Amixture of 900 gof 3% sodium amalgam, 180 g of bromobenzene, 200 ml of toluene and 10 ml of ethyl acetate is boiled for 12 hours on an oil bath at 130°C and then transferred whilst still hot into a large separating funnel for maximum possible separation from mercury. Extraction is then carr ied out, over 10 hours, by the method described in [59], The solution containing diphenylmercury is eva-porated at 20 mm, raising the temperature at the end to I lO0C, and the residue washed with cold alcohol. Yield: 96 g (47%); m.p. 122-123°C.

Preparation of di-/3-naph thy lmercury [55 ] . 50 g of/3-bromonaphthalene, 40 g of xylene, 5 g of ethyl acetate and 300 g of 4% sodium amalgam are refluxed on an oil bath for 24 hours. Further additions of ethyl acetate are made during the f i rst 12 hours. After separation of the mercury the residue is freed from organic admixtures by boiling with alcohol (washed with water to remove NaBr ) and crystal l ized from pentanol; m.p. 238°C. Yield: 17 g.

/3-Chloronaphthalene also gives di-/3-naphthylmercury under these conditions, but in smaller yields [57].


Di-a -naphthylmercury has been obtained in the same way [55]; m.p. 249 0C.

On reaction with benzyl bromide and chloride, sodium amalgam gives only dibenzyl [5]. A very small yieldof d i - ( « - sty ryl) mercury was obtained from the interaction of co-bromostyrene with 7.5% so-dium amalgam at 140°C over 7 hours [60] (see, however, Chapter 1).

Treatment of 5-fluoro-6-bromo-l,2,4-trimethylbenzene with lithium amalgam in ether led to the formation of 43% of 1,2,4-tri-methylphenylenemercury (possibly, by analogy with o-phenylene-mercury, see below, as the hexamer) and other mercury-free products [61]. Under the same conditions, o -fluorobromobenzene gave hexameric o-phenylenemercury [61].

On heating for 5 hours with 2% sodium amalgam in petroleum ether in the presence of ethyl acetate, o-dibromobenzene gives a substance not melting up to 300°C, to which Vecchiotti [62] ascribed a structure of a heterocycle containing two Hg heteroatoms, but which Wittig showed [63] to be a hexamer of structure as that shown immediately above "Preparation of diorganomercury compounds with removal of the ether by distillation" in Chapter 2.

Synthesis of hexameric o-phenylenemercury [63 ] , Sodium amalgam is prepared in a Schlenk tube made f rom Jena glass, under nitrogen, f rom 200 g of mercury and 2 g (87 g-atoms) of sodium, and is treated with 7.1 g (30 m l ) of o-dibromobenzene in 40 ml of absolute ether. A f te r 3-4 days of shaking the upper layer is decanted off and the lower layer decomposed with cold and then hot water, separated from mercury and extracted with boiling dimethylformamide until the latter no longer yields crystals on cooling (roughly three 100-ml portions). The yield is 4.3 g (52% calculated on the o-d ibromo-benzene); the product decomposes at 326°C.

Determinations of the molecular weight and the crystal structure [64] showed the product to be hexameric (C6H4Hg)6 (cf. structure im-mediately above "Preparation of diorganomercury . . i n C h a p t e r 2). Theseparation of the reaction product was modified as follows [65].

After hydrolysis, the insoluble residue is dried and extracted with several portions of N-methylpyrrol idone (about 350 ml of the latter solvent are needed for the crude product obtained from 28.4 g of o-dibromobenzene, 7 go f Na and 680 g of Hg). The resulting turbid extracts are c lar i f ied by centrifuging (30 minutes at 300 rpm). Hexameric o-phenylene-mercury is precipitated as a white powder from the dark solution with half the latter 's volume of methanol and is crystal l ized from dimethylformamide or methyl iodide. Yie ld: 13.5 g (41%).

When the same reaction is carried out in a more polar medium (tetrahydrofuran or, better, diglyme) the main product is dimeric o-terphenylenemercury [66] (see diagram of structure overleaf) and hexameric o -phenylenemercury (cf. structure immediately above "Preparation of diorganomercury..." in Chapter 2). The amalgams of Li and K can also be used [66].

Preparat ionofdimeric O-terphenylenemercury [66]. o-Dibromobenzene (9.5 g) and an amalgam prepared from 4.6 g of sodium and 15 ml of mercury are shaken in 100 ml of absolute diglyme, under nitrogen, f o r 30 minutes, and then fo r a further 12 hours after



Structure of dimeric o-terphenylenemercury

the reaction has ceased. After addition of water and separation of the mercury in a separating funnel, ether is added and hexameric o -phenylenemercury f i l tered off. The latter is then boiled with a small amount of toluene. The combined toluene and ethereal solutions are evaporated down, to the point of crystall ization from the hot solution, and, by simultaneous addition of toluene and evaporation of diglyme, the latter is replaced by toluene (the volume of the toluene solution is about 30 ml). Brownish o-terphenylene-mercury crystal l izes out on cooling and is recrystal l ized from toluene with decolorizing charcoal; m.p. 292-293°C; yield: 40-42% calculated on the o -dibromobenzene.

OJ,G/ -Dibromo-o -xylene heated for 24 hours with 2% sodium amalgam (petroleum ether, ethyl acetate) gives an infusible com-pound for which the structure

has been proposed [67]. It is possible that it too is polymeric. . By treating p-dibromodiphenyl with sodium amalgam in xylene,

Michaelis [68] obtained a yellow insoluble substance for which he proposed the formula Hg(C6H4C6H4)Hg, but which is probably a polymer.

Alkoxy- and alkylaminomercury derivatives of the aromatic series are obtained by the same method and with the same durations of heating, but with more dilute amalgams than are used for the organo-mercury derivatives of the aromatic hydrocarbons.

Preparation of di-p-anisylmereury [69 ] , P -Bromoanisole (100 g), 80 g of xylene and 0.1 their volume of ethyl acetate are boiled for 24 hours at 140°C (oil bath) with 1.5% sodium amalgam containing sodium in a 100% excess over the theoretical amount. The flask is frequently shaken and a little ethyl acetate added every 8 hours. The product, which solidifies on cooling, is separated from mercury and extracted with benzene. The extract is evaporated down to a certain extent. The precipitating di-p-anisylmercury is washed with petroleum ether and recrystal l ized from benzene; m.p. 202°C; yield: about

A variation of this procedure, without preliminary preparation of the amalgam, has been described in [14].

Sodium (0.4 g-atom) and then 37 g (0.2 mole) of p-Cromoanisole dissolved in a mixture of 6 ml of ethyl acetate and 100 ml of xylene are added to 388 g of mercury and 30 g of xylene heated to 160°C in a three-necked flask. The whole mixture is boiled for 24 hours

40 g (50%).


at 160°C, then hydrolysed and dried. The solvent is then disti l led off and the residue crysta l l i zed f r om methanol; m.p. 202-204°C (yield not g iven) [14],

The same procedure was applied to the preparation of the d i -o -anisyl (m.p. 108°C), di-o-phenetyl (m.p. 83°C) and di-?-phenetyl (m.p. 135.5°C) derivatives [55],

Preparation of bis-p-dimethylaminophenylmercury [ 70 ] , p-Bromodimethylani l ine (100 g), 70 g of xylene and 0.1 their volume of ethyl acetate a re boiled f o r 24 hours with 1.5% sodium amalgam containing sodium in a 100% excess over the theoretical value. The pro-duct is extracted with benzene, evaporation of which subsequently results in c rys ta l l i za -tion of b is-p-dimethylaminophenylmercury; m.p. 169°C ( f rom benzene).

A similar procedure was used to obtain di(3-dimethylamino-4-methylphenyl)-mercury [71].

Bis-perfluoroalkylmercury derivatives have been prepared in this way from iodoperfluoroalkanes, using the amalgams not of the alkali metals but of Ag, Cu and Zn [72], and, best of all, the amalgams of Cd [72, 73], with which the reactions proceed at room temperature (Ag amalgam requires heating to 80 0C, Cu amalgam to 160-180°C and Zn amalgams react over 4 days at room temperature).

Preparation of bis-perfluoromethylmercury [ 7 2 ] . Tr i f luoromethy l iodide (3 g ) is con-densed into a Py r ex tube containing an amalgam prepared f r om 3 g of Cd and 20 ml of Hg. A f t e r the tube has been shaken f o r 24 hours at room temperature, the liquid phase disappears and the solid substance is extracted with ether. Evaporation of the latter g ives the required product, which is puri f ied by sublimation; m.p. 163°C; y ie ld : 35-40% as calculated on the reacted C F g I (50-60%).

The same procedure was used to prepare bis-perfluoroethyl-mercury (shaking C2F5I for 14 days at 30°C with Cd amalgam) in a yield of 60%.

Bis-trideuteromethylmercury was similarly obtained, in 75% yield, by heating CD3H with cadmium amalgam in a sealed tube (1 day at 160°C or 3 days at 125°C) [74].

The interaction of bromopentafluorobenzene with lithium amalgam gave bis-pentafluorophenylmercury [75],

Synthesis of bis-pentafluorophenylmercury [ 75 ] , Bromopentaf luorobenzene (5 g ) in 10 ml of ether is added to a s t i r red suspension of lithium amalgam (0.3 g of L i and 200 g of Hg) in 30 ml of ether at 0°C. Energet ic react ion takes place and the viscous amalgam becomes mobile. A f t e r 18 hours the mixture is treated with 50 ml of water and the ethereal l ayer separated, combined with the ether extracts (two 50-ml port ions) of the aqueous layer and dried ove r magnesium sulfate. Evaporation of the ether g ives a brown residue, which is steam-dist i l led and sublimed. White crystals , m.p. 117-118°C (2.75 g).

The melt ing-point of the substance r i ses to 136-137°C a f ter storage and is 138-139°C immediately a f ter recrysta l l i zat ion. The substance thus probably exists in several polymorphic f o rms .

Diphenylmercury has also been obtained by boiling bromobenzene with mercury in xylene in the presence of metallic lithium [76],



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(1873). 27. M. Tiffeneau, Bull. Sci.pharmac., 28, 65 (1921); Chem. ZentBl.,

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(1950). 74. E. E. Bevege, R. Renaud and L. C. Leitch, Can. J. Chem., 31

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Dokl. Akad. Nauk SSSR, 1 4, 557 (1957).

CHAPTER 5

Introduction of Mercury in Place of a Hydrogen Atom (Mercuration)

The most important method of synthesizing organomercury compounds is the direct replacement of an atom of hydrogen by HgX (where X is an anion) according to the reaction RH + HgX2 = RHgX + HX. This method, based on the work of Pesci, Hofmann and particularly Dimroth, is used for certain aliphatic derivatives and is generally applied in the aromatic and heterocyclic series.

Mercuration constitutes an electrophilic substitution reaction and consequently occurs at the site of the greatest electron density. In the aromatic series, this has been confirmed by a great volume of evidence, such as the easier susceptibility of the more nucleophilic aromatic rings to mercuration and the appearance of orientation effects obeying the usual orientation laws typical of electrophilic substitution.

If an aliphatic compound is to be mercurated, it must contain an activated hydrogen atom and be capable of forming a protonable carbanion. Compounds such as malonic and acetoacetic esters, acetylenic derivatives with a free C = CH group and cyclopentadiene can be mercurated with particular ease. In these cases the same Hg atom can in fact be substituted for two hydrogen atoms, which, generally speaking, is an exception. Thus, malonic ester with mer-curic oxide gives (C2H5OOC)2CH-Hg-CH(COOC2H5)2, and acetylenes RC 3 CH and organomercury hydroxides R'HgOH give RC = CHgR'; both these reactions take place at room temperature.

Rather vigorous conditions are required for the mercuration of alcohols, acids, ketones and aldehydes. The mercury enters, of course, in the a-position, but the situation is generally complicated by simultaneous functional changes (of the carbonyl group), examples of which will be described later in this chapter. It is clear that a homologous series of alkylmercury salts cannot be prepared by mercuration.

The possibilities of the methods are thus very limited in the ali-phatic series. In contrast, all aromatic compounds, including aro-matic heterocycles and their benzo-derivatives as well as ferrocene and certain other metallocenes, interact with various degrees of



ease with mereurating reagents, on heating and sometimes at room temperature, forming organomercury salts. An aromatic nucleus activated with respect to ordinary electrophilic substitutions such as nitration or sulfonation will also be active toward mercuration, i.e. rings containing NH2 and OH groups are aminated most readily; the aminated rings even in aqueous solutions at room temperature. Monohydroxylicphenolsare usually mercurated on heating, whereas resorcinol and phloroglucinol react so easily that only in the case of the former can one stop the process at the stage of the mono-mercurated product, and the mercuration proceeds in the cold, in aqueous solution.

Toluene reacts more readily than benzene and naphthalene more readily than toluene.

The mercurations of nitrobenzene and of other benzene derivatives containing m-directing groups proceed less readily than in the case of benzene itself: the reactions with mercuric acetate occur on heating to 150°C with a solvent. The superaromatic heterocyclics pyrole, furan, and thiophene are mercurated with particular ease, whereas pyridine requires more severe conditions. Mildconditions suffice for ferrocene and relatively mild conditions for the other metallocenes.

The entry of mercury into an aromatic compound obeys the usual orientation rules of electrophilic substitution. The anomalous orientations observed in the reactions of mercuric acetate with nitrobenzene, benzoic acid, benzophenone and toluene (predominant o - substitution in the former cases and considerable m-substitution in the last-mentioned case) are explained by the low degree of ion-ization of the mercury salt in these nonpolar media and by the high reaction temperatures (up to 150°C) at which the mereurating agent has a low selectivity. The reaction may in these cases have an ap-preciable homolytic character. In the mercurations of nitrobenzene and toluene with mercuric perchlorate in aqueous perchloric acid, when the mereurating agent is definitely a mercury ion in some hydrated form, the reaction proceeds under mild conditions and the isomeric distribution obeys the usual orientation rules of elec-trophilic substitution [1].

It should also be borne in mind that the mercuration may become reversible at high temperatures, and that an isomer can transform into a more stable one if the time of reaction is made very long (cf. under "Mercuration of the aromatic carboxylic, sulfonic and arsonic acids and their derivatives" later in this chapter).

Studies of mercurations of the alkylbenzenes showed that the reaction is of second order. The main disadvantage, which limits the usefulness of mercuration in the aromatic series, is the for -mation of a mixture of all possible isomeric monomercurated compounds and the simultaneous formation of polymercurated products. Such mixtures are sometimes difficult to separate.

In spite of this, direct mercuration of aromatics is the main

MERCURATION 59

method of synthesis in this series, owing to its simplicity and low cost. Its advantage over syntheses via organomagnesium and similar derivatives lies in the possibility of introducing mercury into molecules containing substituents which are not indifferent to the Grignards and other reagents. The advantage over methods of synthesis via sulfinic acids, arylboronic acids and similar com-pounds is that the starting materials need not be prepared f irst. If the corresponding amine is available, arylmercury salts without substituents or with simple substituents are best obtained (and in purer form) by the diazo method. If, however, it is considered that mercuration can be applied to very complex aromatic molecules, such as multiply-substituted benzenes, condensed aromatic hydro-carbons, polyphenylmethane derivatives, including dyes of this series and various other dyes, heterocyclics and alkaloids, it will become obvious that the direct mercuration method is universal.

The mereurating reagent may be mercuric oxide or some other salt: mercuric acetate (or an Hg salt of another carboxylic acid), sulfate, perchlorate, or nitrate. The most intensive reagents are the oxide and the acetate, since the liberated weak acetic acid does not decompose the resulting organomercury salt even at high tem-peratures. However, in high-temperature mercurations of aromatic compounds the acetate has a low selectivity and the product is a disordered mixture of isomers (see above). In these cases, mercu-ration with mercuric perchlorate at low temperatures results in normal orientation. Moreover, in the mercurations with mercuric acetate the rate can be very considerably accelerated by small additions of perchloric acid, allowing the reaction to be carried out at room temperature; the orientation is then more specific (cf. the mercuration of toluene).

Mercuric nitrate is used successfully for the mercuration of aliphatic ketones at the a-carbon, and for aromatic compounds, especially as a mixture with mercuric oxide and anhydrous calcium sulfate. The part played by the HgO and CaSO4 is clear from the following reactions:

RH + Hg(NO3)2 -> RHgNO 3 + HNO3

H g O + 2H NO3 ^ Hg(NO3)2 + H2O

CaSO4 + 2H2O CaSO4-2H20

Mercuric halides are among the least active mereurating agents and their application is limited. Understandably, mercuric chloride reacts more energetically in the presence of Na2CC^ or NaHC03. Mercuric cyanide is the weakest mereurating agent and its use is limited to a few acetylenes. Mercuracetamide and the mercury salt of trinitromethane are powerful mereurating agents, but the latter is not sufficiently universal.

Mercurations can be carried out in solution, particularly aqueous solutions, or by reacting the mereurating agent directly with the

Ref erences see p. 121


liquid or fused compound, at temperatures ranging from room temperature to 180-200°C. The reactions are continued till the mercury ion disappears, testing the reaction mixture with caustic soda for the absence of a yellow precipitate of mercuric oxide. The product either crystallizes out spontaneously from the reaction mixture and is then separated off and washed to remove the usual excess of the mercurated substance, or is salted out by NaCl or KBr in the form of the corresponding halide, always less soluble and higher-melting than, for example, the primary product of mercuration, the acetate. The product is then purified by recrys-tallization from various organic solvents; the polymercurated compounds generally do not dissolve, and the o-isomer is often appreciably more soluble than the p-isomer and remains in the mother liquor. The solvents used most frequently are, in order of increasing dissolving power, benzene, chloroform, alcohol, ethyl acetate, acetone, dimethylformamide and pyridine.

a)Mercuration of Aliphatic and Alicyclic Structures

The course of the mercurations in the aliphatic series differs in certain respects from the corresponding reactions involving aro-matic and heterocyclic compounds. The action of mercuric salts on aliphatics is often not limited to the replacement of one hydrogen by mercury, but leads to the formation of polymercurated products up to the fully mercurated compounds, the mercarbides.

It should be borne in mind that in those cases when polymercur-ated products were obtained (see later, under the mercurations of aldehydes, ketones, carboxylic acids, etc.) it was not always certain whether these substances were individual compounds, since poly-mercurated compounds are generally insoluble and difficult to purify. The structural formulae ascribed to these substances, often based only on elementary analyses, and involving C=Hg bonds and three- and four-membered rings containing mercury, do not correspond to reality. There is no doubt that they, and possibly other polymercurated compounds, are in fact polymeric.

In certain cases the mercurating reagent not only substitutes an Hg atom for a hydrogen but also changes the function in the substrate compound. On the other hand, the mercurations of the aliphatic compounds, like those of aromatics and heterocyclics, are in many cases not accompanied by side reactions and their rates depend only on the mobility of the substituted hydrogen. Thus, compounds with a particularly active hydrogen (the derivatives of malonic [2, 3], methylmalonic [4], methylene-bis-malonic [5, 6], allylmalonic [7], cyanoacetic [8, 9], cyanopropionic [8], nitroacetic [10-12], diazoacetic [13-15] and acetoacetic [3, 16-18] acids) mer-curate readily at the a-carbon on shaking in the cold with a solution of a mercuric salt. The mercurations of the f irst two of these acids

MERCURATION 61

are accompanied by the evolution of one molecule of CO2 (cf. Chapter 9). Polymercurated products are formed when malonic acid is heated with HgO in an alkaline medium [19]. Compoundsofthis type are also mercurated with HgCl2 in the presence of soda and glycerol (esters [20, 21], amides [20, 21], substituted amides [20] and anilides [21] of acetoacetic and malonic acids), with mercur-acetamide (methylmalonic ester [4], cyanacetamide and its N-alkyl and N-aryl derivatives [20]) and with the Hgsalt of trinitromethane [22] (malonic, nitroacetic, and acetoacetic esters and acetylacetone). Acetoacetic ester is also mercurated at the methylene group by the Hg salts of carboxylic acids other than acetic, giving dimercurated derivatives [18]; with HgO and heating, acetoacetic ester gives a compound in which there are three ester residues for every two mercury atoms [23] and products of a more complex structure [23a],

The mercurations of acetylenes without addition of the mercuric salt across the triple bond are carried out with an alkaline solution of mercuric iodide.

This method allows easy mercuration of acetylene [24] with the formation of (HCsC)2Hg, of monosubstituted acetylenes [25-27] with the formation of (RC sC)2Hg, of acetylenic ethers ROC2H4CsCH [26] and of various alkyl- [27] and arylacetylenes [24, 25, 27-29], It was also used to mercurate l-o- and p-methoxyphenoxyheptyl-1-ynes [30], l-butylthiobuten-3-yne-l [31a], phenylmercaptoacetylene [31], 1-tr idecyl- [32], p-tolylmercaptoacetylenes [33], 2-carbeth-oxy-2-methyl-l-ethynylcyclohexylcarbinol [34], trans -undec-7-en-1-yne [35], 1-phenylbutadiynyl [36],fullydeuteratedmethylacetylene [37], n-heptadec-l-yne [38], d e c - c i s - (and trans-)-3-ene-l-ynes [39], a-naphthylacetylene [40], bis-(naphthylethynyl)- and b i s - ( l -thienylethynyl)mercury, obtained also by the action of mercuric oxide in alcohol on the corresponding acetylenes in the presence of alkali (boiling for 5 hours) [41], cis - (and £mns-)-pent-2-en-4-ynes [42], 4-m-methoxyphenylbutyne-1 [43], 4,4-difluoro-2-buten-1-yne [44], nonadiyne-1,4 [45], ^-nitrophenylacetylene [46], <u-fluoroalkynes F (CH 2 )nC=CH ( n = 3-6) [47], 1,1,1-trifluoropropyne [48], pentafluorobutyne [48], mono- and diacetylenic alcohols [49], phenyldiacetylene [50], 3-bromo-2,4,6-trimethylphenylacetylene [25], p-dimethylaminophenylacetylene [51], monochloroacetylene [52], substituted phenylethynylcarbinols [53], butylacetylene [54], acetylenyldivinyl [55] and 1 - trans-2-bromovinyl-2-ethynylbenzene [56] (mercurated in the presence of n-butylamine; the kinetics of such a reaction have been studied).

The mercuration of halogenated ethylenes [57,58] is also conduc-ted with alkaline HgI2 or Hg(CN)2. In alkaline solution, Hg(CN)2

tends to split off hydrogen halide apart from being a mercurating agent, so that when used with polyhalogenated ethanes [57] the products are organomercury derivatives of halogenated olefins, e.g.

2CHBr2CHBr2 + Hg(CN)2 + 2KOH-+ (CBr2=CBr)2Hg + 2KBr + 2KCN + 4H20



Similarly, polyhalogenated olefins give the organomercury deriva-tives of halogenated acetylenes [57-60] (the latter do not exhibit quasicomplex properties [61]):

Cl Cl

2 / C = C ^ + Hg ( C N ) 2 + 4 K O H ^ (CCl=C)2 H g + 2KC1 + 2 K C N + 4 H 2 0

H H

According to FitzGibbon [58], among the dichloroethylenes only the cis-isomer reacts in this way; trans -dichloroethylene does not split off HCl and the product is (CHCl=CCl)2Hg. Trichloroethylene also does not split off HCl and gives bis-perchlorovinylmercury [62, 63]. Mercury difluoroacetylide has been obtained bypassing fluoroacetylene through an aqueous solution of mercuric nitrate [64].

Acetylene can also be mercurated by the action of organomer-cury hydroxides with the formation of RHgC sCHgR [64-66] and RHgC = CH [67].

On the basis of a study of the kinetics of reactions of mono sub-stituted acetylenes with RHgX and Me2HgX4 in the presence of a base - triethylamine (the reactions are of pseudo-first order owing to the excess of acetylene and the base), it has been proposed that the mechanism of these reactions involves a four-center transition state.

The compounds with less mobile hydrogen are mercurated under more vigorous conditions by the action of an excess of the mercury salt with heating. This results in the formation of polymercurated products. Thus, for example, sodium acetate on boiling with mercur-ic oxide in concentrated alkali gives a compound to which Hofmann [69] ascribed the formula Hg=C(HgOH)COONa. The product of the reaction of potassium chloroacetate with HgO [69] is a mixture and not a mercuration product [69a]. Boiling of mercuric acetate in acetic acid results in a compound C10H10O10Hg5 [70]. Mercurated acetic acid HgCH2CO2 can be obtained by heating mercuric acetate above its melting-point [71]. The mercurations of sodium acetate and sodium propionate by fusion with acetamide and HgO [72], and the reaction of mercuric acetate with methyl a-eleostearate [73], have been described.

The structure (CH3COOHg)2C-C=O

I I Hg+ O-

has been ascribed to the product of the mercuration of acetic an-hydride with mercuric acetate [74].

Heating of mercuramides, e.g. mercuracetamide, gives sub-stances of structure A [78]:

CO A CH 2 / ^ N H

Hg

MERCURATION 63

See also [75] for the mercuration of acetamide and Chapter 16 for the mercuration of acyl amides. The action of mercuric nitrate on pyruvic acid in the presence of acupric salt results in mercuration of all three methyl hydrogens [76], with the formation of

Hg o ( N c — C O - C O O H

Hs I n g HgNO3

The esters of aliphatic dicarboxylic sulfo-acids, such as the sulfosuccinic ester, have been mercurated [77] by the action of HgO at 4-5°C; the structures of the products were not reported.

Several hours of boiling of ethanol with mercuric oxide in the presence of NaOH yields the fully mercurated ethane - ethane-hydroxyhexamercarbide, which according to Hofmann [79] has the formula B :

HOHg HgOH \ /

B H g - C - C - H g x

0 < / \ >0 X H g H g /

Methanol does not give analogous compounds [79]. The same mercarbide has also been obtained by the action of HgO on propanol, allyl alcohol, butanol, pentanol, acetic acid, starch, cane sugar and cellulose [79]. It has been proposed that it is a polymer [80], and there are some indications that it is a derivative not of ethane, but of methane [81].

As a rule, aldehydes oxidize under the action of the usual mer-eurating agents [82]. The compound C2HOHg2ClO3 was obtained by the action of mercuric hypochlorite on acetaldehyde [83]. The re-action of acetaldehyde with HgO in an alkaline solution afforded a rapidly polymerizing compound (C4H8O5Hg3)a, [79, 84].

According to Hofmann [79], on prolonged boiling with HgO in aqueous-alcoholic alkali, acetaldehyde gives the trimercurated

/Hg acetaldehyde H0Hg(0<^ p)CCHO, then the corresponding acid

/ H g N H g X /Hg (Of ) )CC0 2H, and finally the mercarbide [HOHg(Or } )C - ] 2 .

Hg x H g x

The formation of ethanehydroxyhexamercarbide from ethanol follows the same pattern.

An amorphous compound C2H4O^Hg is formed [82] when an ace-taldehyde-containing aqueous solution of mercuric acetate is treated at O0C with caustic soda to an alkaline reaction. Acetaldehyde reacts with a solution of HgO in alkaline Na2S03 with the formation of an insoluble compound C2H2C^Hg2 [85]. C3HO4NHg2 is formed [16] when a solution of mercuric nitrate acidified with HNO3 is reacted with acetaldehyde.



A description is given in [86] of the formation of insoluble com-pounds during the action of a solution of mercuric sulfate acidified with H2SO4 on acetaldehyde and its higher homologs.

Monomercurated acetaldehyde was obtained by Nesmeyanov and Lutsenko by the addition of mercuric salts to vinyl ethers (cf. Chap-ter 6).

The action of HgO on acetone (in the presence of Ba(OH)2, in the cold) [84] and of mercuric acetate on acetone [87] and methyl ethyl ketone [87] (with heating), results in both mercuration and changes in the functions of these compounds. The product formed from mercuric oxide and acetone is said [84] to be

H H I I

H O H g - C - H g — C - H g O H I I

H 3 C - C - O - C - C H 3

I I OH OH

Other ketones which tend to enolize give similar compounds, which were, however, in most cases isolated as insoluble poly-mers [84, 88].

The structure CH2R CH2R I I

H O — C - O - C - O H

CH3OCOHgx I I /HgOCOCH3

NC C CH3OCOHg/ J

R R

has been ascribed [87] to the compound from acetone (R = H) or methyl ethyl ketone (R = CH3) and mercuric acetate.

Monomercurated acetone has been obtained indirectly via butyl isopropenyl ether (cf. Chapter 6). Thesamecompoundcan be easily made in good yields by using as themercurating agent a mixture of mercuric nitrate, mercuric oxide and calcium sulfate [88], This mixture also allowed the mercuration [89] of other aliphatic ketones in the a-position, and of acetophenone (in the methyl group). Both the a-positions in methyl ethyl ketone are attacked, giving two monomercurated compounds, and in methyl isopropyl ketone only the tertiary hydrogen is replaced by mercury, and not the primary. Pinaeolone gives the a-mercurated product, in a yield of 33%. The mercury salt of trinitromethane will also mercurate acetone (70 hours in ether, 50 hours in water) and cyclopentanone (5 days in water); the yields are quantitative in both cases [22], The product is a monomercurated compound.

For information about the insoluble compounds forming when acetone is reacted with mercuric nitrate in nitric acid [16], mer-curic sulfate in sulfuric acid [3, 86, 90, 91], mercuric cyanide in

xHgOCOCH 3

MERCURATION 65

an alkaline solution [92, 93], and those forming during the action of alkaline HgI2 on acetone and other ketones [94], the reader is referred to the original literature.

Saturated alicyclic hydrocarbons do not as a rule enter into mer-curation reactions, but cyclopentadiene can be mercurated in the methylene group under very mild conditions by alcoholic HgCl2

[95, 96]. The product contains two atoms of mercury and may be a polymer [96], A mixture of cyclopentadienylmercury chloride and dicyclopentadienylmercury is formed in the presence of sodium acetate [97]. According to [122a], mercuric chloride or acetate gives C5(HgX)6 in the presence of sodium acetate; in the latter's absence, the product is C5H5HgCl with mercuric chloride and C5H2(HgC2H3O2)4 with mercuric acetate.

A mixture of C5H5HgI and (C5H5)2Hg is formed in the reaction of cyclopentadiene with aqueous ^HgI 4 [98]; dicyclopentadienyl-mercury (m.p. 83-85°C) can be extracted from this mixture with tetrahydrofuran or petroleum ether [98a],

The interaction of 1-pyrrolidinocyclopentene with HgCl2 OrHgBr2

results in the formation of an immonium salt, accompanied by C-mercuration [98b]:

On the other hand, the enamines, not containing a sterically hindered nitrogen, undergo N-mercuration (cf. Chapter 16).

Mercuric acetate at high temperatures (200°C) and under pres-sure is necessary for the introduction of mercury into the deca-hydronaphthalene molecule [99],

An attempt at mereurating l,l-pentamethylenebicyclo-(0,l,4)-heptane has been described [100].

Let us now turn to the mercuration of the alicyclic-hydrocarbon derivatives, such as camphor [101]. In this case both the a-hydro-gens are replaced under the action of HgI2 in caustic soda or pot-assium ethoxide. The action of alkaline K2HgI4 on camphor at IOO0C resulted in a compound (C10H10O)3Hg4I2 [101], which on treatment with cold glacial acetic acid, dilution with water and salting out with an alkali metal halide gave the monomercurated camphor

The methyl ester of camphorcarboxylic acid has been mercurated


HgCl


[102] on heating with HgO at 160-180°C; the structure of the pro-ducts is unknown. Camphorcarboxylic acid itself has also been mer-curated, with mercuric acetate (conditions not given) [102], Other reported mercurations are those of cyclohexanol [99] (at 2000C and under pressure) and cholesterol (in position 6, by boiling with mercuric acetate in acetic acid) [103-105]:

Preparation of dimercurated derivatives of cycloheptatrien-l-ol-2-one by heating the latter with mercuric acetate to 150°C has been reported [106],

The mercuration of acetophenone also belongs in this section, because when this ketone is heated to 150°C with a mercury salt the replacement occurs in the aliphatic radical and not in the ring [7, 71, 107].

According to Patent literature [108], when alkyl aryl ketones and their derivatives are mercurated, the reaction occurs in the ali-phatic radicals at high temperatures and in the aromatic at low temperatures. This rule does not, of course, apply generally to other classes of compounds (cf., for example, the mercuration of nitrotoluenes with mercuric acetate later in this chapter).

p-Chloroacetophenone has been mercurated [108] by heating with mercuric acetate to 130 °C, but the point of entry of the mer-cury atom was not shown. p-Bromo-m-nitroacetone fused with mercuric acetate (135°C, VA, hours) gave two products (structure not shown) [109], and the iodo analog of the above ketone gave only one product under the same conditions [109].

According to Hantzsch [110, 111], the action of aqueous mercuric chloride on the sodium salts of several indandione derivatives affords C-Hg products (substitution in position 2), for example

HO HgCl

O O

C C

\ / ' C C

C-COOC2H5 + HgCla -»j 0 C-COOC2H5 + NaCl \

HgCl \

ONa O

MERCURATION 67

On being heated with mercuric acetate to 130 0C for 15-20 minutes, p-acetobenzoic acid forms [108]

COCHHgOCOCH3

( f OCO-

p -Acetophenylarsonic acid has been mercurated under the same conditions over 1 hour [108]; the structure of the product was not given.

The mercurations of p-acetophenylarsonic and -stibinic acids also will be dealt with in the section dealing with the mercuration of aromatic ketones, and the formation of mercury derivatives of nitrobenzyl and nitrobenzylidene by boiling nitrotoluenes with alkaline HgO in the section on the mercuration of aromatic hydro-carbons.

Mercuration of acetylene [ 27 ] , An alkaline solution of mercur i c iodide is f i r s t p re -pared by dissolv ing 66 g (0.486 g - eq t . ) of HgC l 2 in a solution of 163 g (0.61 g -eq t . ) of KI and 163 ml of water and adding 125 ml of 10% NaOH (0.31 g-eqt . ) . The solution of the required substituted acetylene (1 eqt. in 20 volumes of 95% alcohol ) is then added drop-wise, with st i rr ing, to a cooled and diluted alkaline solution of mercur ic iodide (2 eqt.). Immediate precipitat ion takes place. The mixtures are s t i r red f o r 2 -3 minutes and f i l t ered , washing the precipitate with 50% alcohol. The mixtures should not be set aside f o r too long be fo re the f i l trat ion, otherwise the precipi tates become gray as a result of a secondary react ion which is evidently accompanied by the l iberation of meta l l i c m e r -cury. The crude products are usually puri f ied by crysta l l i zat ion f rom alcohol or benzene; they may also be dissolved in a small amount of benzene or ether and precipi tated with petroleum ether [27],

Melting-points of (RC-C)2Hg: with R = C H , , 203-204°C; C2H5, 162-163°C [27]; n-C3H7, 118.8°C; n-C4H9, 96.4*C; t-C4Hg, 91-92°C [27]; n-C5Hn , 61°C [27]; n-C6H13, 80.7°C; n-C7H15, 68.5°C; n-C8H7, 84°C; n-C9H19, 79°C; C10H21, 85°C [27]; C6H5CH2, 106.5-107.5°C [27]; CeH5, 124.5-125 0C [27]; P-CH3C6H4, 199-202°C [27]; p-CH3OC6H4, 207-209 0C [27]; P-C2H5C6H4, 142-143°C; P-ClC6H4, 121-122°C; OT-ClC6H4, 138-139°C; o -ClC6H4, 212-213°C; p-BrCgH4, 256-257°C [112]; Cl, 185°C.

Preparation of R H g C 3 C H g R [ 6 5 ] . Pure acetylene is passed through a c l ear solution of 8 g of RHgX in 800 ml of 10% aqueous KOH (if R is a higher alkyl or aryl , it is better to use alcoholic potash because the corresponding RHgOH are sparingly soluble in water [65b, 65c]) placed in a c losed vesse l . Immediate turbidity appears and format ion of white precipitate takes place. The vesse l is occasionally shaken and the passage of acetylene continued until no further absorption of the gas is observed. The precipi tate is f i l t e red off, washed with water and 70% alcohol and recrys ta l l i z ed f rom a suitable solvent, such as acetone, benzene, pyridine, methanol, ethanol, or carbon tetrachloride.

Melting-points of RHgC=CHgR [65]: with R =CH3 , 232°C; C2H5, 195°C; n-C3H7, 151°C; C4H9, 125°C; C5H11, 91°C; C6H13,104-105°C;



iso-C3H7, I lO0C; S-C4H9, 105.5°C; Iso-C5H1I, 106°C; C7H15, 96°C; C8H17, 1080C; C9H18, 98°C; C10H21, I l l 0 C ; C6H5, 178-179°C; o -CH3C6H4, 205-206°C; P-CH3C6H4, 390-391°C.

Synthesis of mercury 2-o-(trans-2 -bromovinyl)phenylacetylide [56]. A solution of 1-trans-2-bromovinyl-2-ethynylbenzene (3.96 g) in n-butylamine ( IOmi ) is added to 3.8 g of mercuric acetate in 15 ml of the same solvent. Two minutes after the end of the evolution of heat, the mixture is poured into 50 ml of ice-cold 0.5N H2SO4 and the neutral part extracted with ethyl acetate. The acetylide (4.5 g, 78%) crystall izes out of benzene in colorless leaflets, m.p. 187-188°C.

The same method was used to obtain the mercury of phenylace-tylene, oct- l -yne, and 3-tetrahydropyranyloxyprop-l-yne, inyields of 98, 78 and 86%, respectively.

Preparation of bis-perchlorovinylmercury [63] . A 500-ml flask is charged with 500 g (0.2 mole) Hg(CN)2, 23 g (0.41 mole) of KOH and 200 ml of water. Trichloroethylene (80 g, 0.61 mole) is then added and the mixture placed on a mechanical shaker for 36 hours. The lower, oily layer is separated off and the excess trichloroethylene evapor-ated under vacuum, leaving 30 g of a white precipitate (m.p. 70-73°C). Recrystallization from pentane yields 28.9 g (86%) of the required product, m.p. 72-73°C.

Preparation of ethanoxyhexamercarbide [79] ,

HOHg HgOH

/Hg^C-Cf Hg. 0< / \ >0

x Hg H g /

Metallic sodium (10 g) is dissolved in 150 ml of ethanol, 40 g of finely powdered yellow mercuric oxide added and the mixture s immeredfor 16 hours on a water-bath in a long-necked round-bottom flask. The alcohol is distilled off and the residue washed with water. The resulting grayish-yellow material is freed from Hg and excess HgO by treat-ment with 8-10% HNOg. Inthisway a fairly pure nitrate of the base is obtained. To remove the small remaining amounts of brown tars, the material is heated for about 30 minutes with 10% NaOH on a water bath, washed and worked up with 10% HNO3 at 40°C. This procedure gives 34 g of pure white nitrate, from which the base is liberated, by boiling with pure caustic soda (obtained from metallic Na), in the form of reddish-lemon yellow powder darkening on exposure to light, with a high specific gravity.

According to its structure, it is a derivative not of ethane but methane [81],

Preparation of trimercuridiacetone dichloride (2,6-dimethyl-2,6-dihydroxy-3,5-di-chloromercuri-l-oxa-4-mercuricyclohexane) [84].

C I H g - C H - H g — C H - H g C l I I

HO(CH3)C - O - C(CH3)OH

Unpurified mercuric oxide obtained from 20 g of mercuric chloride is shaken with a solution of 6 ml of acetone in 100-150 ml of water, with gradual addition of aqueous barium hydroxide, until full dissolution takes place. Carbon dioxide is then passed in until no more precipitate appears. The excess CO2 is removed with a current of air. After filtration to remove barium carbonate, the clear solution is evaporated down on a water bath, leaving behind trimercuridiacetone hydrate in the form of a viscous syrup. Treatment with dil. HCl (avoiding its excess) gives the required product; m.p. I lO0C.

The corresponding bromide, m.p. 127°C, is obtained in the same way.

MERCURATION 69

Preparation of tetra-acetoxymercuridiacetone hydrate (3,3,3' ,3 -tetra-acetoxymercuri-2,2 '-dihydroxy-s-butyl ether) [87] .

H O ( C H 3 ) C — O — C ( C H 3 ) O H

I I (H 3COCOHg) 2CCH 3 H 3 CC(HgOCOCH 3 ) 2

Dry mercur i c acetate (25 g ) and 50 g of acetone (obtained f rom the bisul f i te compound) are heated under pressure at IOO0C f o r 2 hours, cooled, f i l t e red and evaporated on a water bath. The oi ly yel low residue is treated with 95% alcohol and f o rms a f laky p r e -cipitate. A f t e r recrysta i l i zat ion f rom alcohol, the melt ing-point is 157°C.

Preparation of phenacylmercury chloride [ 7 1 ] . T w o parts by weight of mercur i c acetate and 3 parts of acetophenone are heated on an oil bath to 150°C until no more mercur ic ion can be detected in the mixture. The solution is then f i l t e red hot and treated with an excess of an aqueous solution of NaCl. The precipitate is washed with ether to remove the excess of acetophenone and recrysta l l i zed f r om high-boil ing l igroine. Phena cy lmercury chlor ide is obtained in the f o rm of needles; m.p. 145-146°C.

Preparation of phenacylmercury bromide [107], A mixture of 40 g (0.12 mo l e ) of mercur i c acetate and 60 g (0.6 mo l e ) of acetophenone is rapidly heated, with st irr ing, on an oil bath to 150°C. Ye l low mercur i c oxide precipitates at f i rs t , which later red is -solves complete ly . The c l ear solution is heated further f o r a few minutes, until it be-comes cloudy and reaction with alkali shows the absence of an inorganic mercury salt. The reaction mixture is then f i l t e red hot and poured into a solution of 15 g of KBr in 100 ml of water . The product is an oi ly liquid, which sol id i f ies on being set aside. a -Bromomercuriacetophenone is f i l t e red off, washed with petroleum ether and r e c r y -stal l ized twice f r om alcohol; m.p. 158-159°C; y ie ld: 25 g (50%).

Preparation of ethyl diacetoxymercurimalonate [ 3 ] , Slightly moist mercur i c acetate (20 g ) are dissolved in 120 g of water and shaken with 7.5 ml of ethyl malonate. The liquid is f i l t e red , heated rapidly to 80° C and immediately cooled with water . The r e -sulting mass is f i l t e red off, washed with cold water and dr ied by aspiration. Y ie ld : 11 g. The same precipi tate appears slowly when an unheated solution is left to stand [3],

Preparation of the internal salt of dimercurimalonic acid [ 3 ] .

-0 \

t H g CO

\ r / +Hg CO

/ -0

A 40-ml port ion of a solution of mercur i c sulfate is added to a solution of 1.5 g of malonic acid in 8 ml of water, i.e. 3 g -atoms of mercury to 1 mole of malonic acid, slightly heated and f i l tered. The white, f inely crysta l l ine precipitate (6.5 g ) is washed with water and alcohol.

Preparation of the internal salt of hydroxymercuriacetic acid [ 2 ] .

t H g - C H 2

~ )C0

-O



Malonic acid (100 g ) and 120 g of caustic soda are dissolved in 300-400 ml of water, heated to boiling and treated with small portions of precipitated mercuric oxide (200 g, 1 mole). After 30 minutes all the mercuric oxide passes into solution and the internal salt is precipitated (after dilution of the liquid to about 1500 ml ) with 950 g of 15.9% H2SO4 (about 1.5 moles). T o ensure complete elimination of CO2, the mixture is heated for several hours on a water bath and washed f ree from sulfuric acid with warm water. The yield is almost quantitative. Thesubstancedoesnot melt and on heating in a capillary it blackens at about 200°C and decomposes around 250°C.

Preparation of the internal salt of hydroxymercuripropionic acid [ 4 ] . (1) Preparation of mercuracetamide. Yellow mercuric oxide (80 g ) is added to 60 g of molten acetamide. On slow heating to 180°C the oxide dissolves, giving a pale yellow melt, which is dis-solved in 400 ml of water and f i l tered. The f i l trate is evaporated to dryness on a water bath and the residue recrystal l ized from methanol. Yield: about 100 g (80%); m.p. about 159°C.

(2) Preparation of the internal salt

C H 3 - C H - C = O I I

Hg+ O-

A mixture of 5.8 g (1.25 moles) of methy! methylmalonate and a solution of 10 g of mer -curacetamide (1 mole ) in 50 ml of water is shaken up into an emulsion, treated with 3 ml of 20% soda solution and heated on a water bath. The ester dissolves and some white flaky precipitate appears if the starting methylmalonic ester contains the unsubstituted compound. The solution is set aside for 30 minutes and then f i ltered. The fi ltrate is cooled to -60 to -70°C and treated successively with 80 ml (2.5 moles ) of IN NaOH1

200 ml of water and 100 ml of IN H2SO4 . The resulting white flaky precipitate is f i l tered off, suspended in water, boiled till the evolution of CO2 comes to an end, f i l tered again, washed and dried in vacuum over sulfuric acid. Yield: 8 g (93%). The substance decom-poses without melting.

Mercuration of ketones with mercuric nitrate [89] , General procedure. The experi-ments are carried out in a 500-ml three-necked flask (fitted with a high-speed propeller st irrer , a thermometer and a dropping funnel), in an atmosphere of dry nitrogen. The reaction is carr ied out in the substance to be mercurated. Mercuric oxide and CaSO4

are generally added f i rst and the mercuric nitrate is introduced only after 5-10 minutes of energetic stirring (10,000 rpm). The temperature is raised over about an hour, and when the red color of HgOisnolonger visible the temperature is maintained for a further 30 minutes. The cooled mixture is f i l tered to remove inorganic salts. The mercurated product is soluble and is isolated either as the nitrate from vacuum-concentrated f i ltrate or, by gradual addition of Kl, as the iodide (an excess of KI should be avoided, as it may exert a symmetrizing action). The resulting mixture is st irred for 15-30 minutes and f i ltered. Evaporation of the fi ltrate yields the organomercury iodide, which is recrystal-lized from acetone, alcohol, pentane, benzene, or their mixtures.

Mercuration of acetone. A mixture of 396 g (6.83 moles) of acetone, 20 g (0.092 mole ) of HgO, 55 g (0.4 mole) of CaSO4 and 20 g (0.092 mole ) of mercuric nitrate reacts at 56°C. Addition of 25 g of KI results in 55 g of iodomercuriacetone, in the form of color-less plates, which are then recrystal l ized twice from acetone and twice from benzene. Yield: 78%; m.p. 98-100°C.

Mercuration of methyl isopropyl ketone. A 250-ml portion of the ketone, 17 g of HgO, 45 g of CaSO4 and 25 g of mercuric nitrate react at 51°C. Addition of 15 g of KI yields a mixture of an oil and a solid, which is treated with acetone, f i l tered and set aside at -72°C for 4 days. The yield of crystalline product after recrystall ization from a mixture of ben-zene and ligroine is 7 g; m.p. 72.7-75.5°C.

Preparation of mercuri-bis-diazoacetic ester [ 14]. Ethyl diazoacetate (2-g portions, 1 mole ) are weighed out into very small flasks, cooled in ice-water and treated with the

MERCURATION 71

calculated amount (0.5 mo l e ) of ye l low mercur i c oxide. The f i r s t small portions of the oxide dissolve completely in 30 minutes, with slight heating, and no evolution of gas takes place. The mass then thickens. A l i tt le ether is added when the substance begins to crysta l l i ze . Some nitrogen is evo lved towards the end of the reaction. The product is extracted with warm ether and f i l t e red off f r om unreacted mercur i c oxide and some metal l ic mercury . Rapid evaporation of the f i l t rate on a water bath and scratching with a glass rod g ives greenish yel low crysta ls (yield: about 70%); m.p. 104°C ( f rom ether, with decomposit ion). The corresponding methyl es ter [14] is obtained in the same way. It is less soluble in ether, and melts at 123°C (with decomposit ion).

Mercuration of cyclopentadiene [Q7]. A solution of 272 g of HgC l 2 in 1 l i t e r of metha-nol is added, drop by drop and with per iodic st irr ing, to an ice-co ld mixture of 250 g of sodium acetate dihydrate, 66 g of f resh ly disti l led monomer ic cyclopentadiene and 500 ml of methanol. A f t e r 1-2 days the precipitate is f i l t e red off and washed with methanol. The y ie ld is 270-280 g of a crude mater ia l (a mixture of cyclopentadienylmercury chloride and dicyclopentadienylmercury) , decomposing at about 95°C. Rapid extract ion with n-octane can be used to obtain a co lor l ess mater ia l enriched in the dicyclopentadienyl-mercury in comparison with the crude product (cf. [122a]).

b) Mercuration of Aromatic Hydrocarbons

Mercuration of the aromatic nucleus was discovered byDimroth. With aromatic hydrocarbons the reaction is fairly difficult and re-quires high temperatures and sometimes pressures. Benzene can be mercurated after several hours at I lO0C with mercuric acetate, or in the presence of ethanol or glacial acetic acid on a water bath; the product is predominantly the monosubstituted compound.

The yield of monomercuribenzene reaches 92% if the reaction is carried out with mercuric acetate and glacial acetic acid in an autoclave at IlO0C [113]. Detailed investigations of the effects of the reaction conditions (molar ratios of the components, time and temperature) on the yields of the monomercurated and dimercurated compounds showed [114] that the optimum conditions for the former product (yield: 92%) is a molar ratio of benzene to acetic acid to mercuric acetate equal to 30:30:1, and stirring for about 3 hours at I lO0C. Acetic acid containing up to 5 moles of water per mole of the mercury salt can be used.

Benzene is mercurated smoothly and in good yield (about 80%) by mercuric nitrate, in the presence of HgO and CaSO4 and in the absence of air. The reaction is carried out under CO2 to avoid secondary processes, nitration, explosions, etc. [115].

Monomercurated benzene, which is isolated in the form of C6H5HgNO^.C6H5HgOH [116] is an intermediate in the hydroxynitra-tion of benzene into picric acid by nitric acid in the presence of mercuric nitrate [116, 117]. Kinetic studies [118] of the mercuration of benzene with mercuric nitrate in nitric acid and with mercuric acetate in acetic acid revealed that the reaction is of over-all sec-ond order (first order with respect to the mercuric ion and to ben-zene) and is catalyzed by acids, being particularly accelerated by HClO4. This is in excellent agreement with the postulated ionic mechanism of mercuration under these conditions.



An electrophilic nature is ascribed to the mereurating agent in the mercuration of benzene with mercuric acetate and acetic acid in the presence of perchloric acid [119].

Some information concerning the mercuration of benzene under various conditions is given in Table 1 below (see [120] and [121-128]).

For the separation of mono- and dimercurated benzenes, see [146]. C6Dfe mercurates less readily than C6H6 [129],

The mercuration of benzene with the mercury salt of trinitro-methane occurs under relatively mild conditions (5 hours on a boiling-water bath) and gives a 58.5% yield of the monomercurated compound [147]. In aqueous solution, this reaction is strongly ac-celerated by neutral salts, particularly sodium perchlorate [148a]. This effect is due to the removal of water from the mercuric ion. The reaction is of second order (first order with respect to benzene and to the mercuric salt). A modification of Hammett's equation was applied in [148a] to the mercuration of benzene by mercuric perchlorate; p=-5.

When benzene is reacted with mercuric acetate, the main di-mercurated compound is the o-isomer; in the mercurations with mercuric perchlorate in HCl4 (any concentration of the latter) the m -isomer predominates, but the ^-isomer will be formed in a greater amount under conditions in which it is insoluble [148]. This shows that the mercuration with mercuric perchlorate in HClO4 is reversible. A mobile equilibrium is found to exist in the formation of all polymercurated products under these conditions [148]. Considerable primary isotopic effect of hydrogen is observed in the mercuration of benzene [129].

Toluene mercurates more readily than benzene, on boiling with mercuric acetate [149, 150], giving all three monomercurated isomers in the ratios o:m:p = 43:13:44 [150, 151], 41:21:37 [1] (ratios determined by converting tolylmercury bromides into radio-active bromotoluenes with 82Br), and 32:15.7:51.8 at 90°C (analysis of bromotoluenes by infra-red spectroscopy [152]). Cf. [201].

A 98% yield of monomercurated toluenes with the o:m:p ratios of 43:13:44 [151] was obtained by adding a hot solution of HgO in acetic acid drop by drop to boiling toluene over a period of 30 minutes and subsequent boiling for an hour. The ratios of the components (mer-curic oxide, acetic acid, and toluene) were, respectively, 1:9:15.

An orientation effect characteristic of electrophilic substitution in toluene is expressed more clearly when this hydrocarbon is mercurated with mercuric perchlorate in HClO 4 - o:m:p =19:7:74 (40% HClO4 at 250C) and 27:13:60 (20% HClO4 at 850C) (analysis of bromotoluenes after labeling with 82Br). A fa i r lyevenpercentage distribution of the isomers was obtained in the mercuration of toluene with mercuric acetate in the presence of perchloric acid [152, 153] (analysis of bromotoluenes by infra-red spectroscopy). The rates of the mercuration of toluene with mercuric perchlorate

Table 1. Mercuration of Benzene under Various Conditions

(Benzene/ Reaction Reaction Y ie ld of Y ie ld of Mercurating salt Medium mercurating temperature, time, monomercurated dimercurated Reference

salt) ratio 0 C hours product, % product, %

Mercuric acetate Glacial acetic acid 7.2 100 5 Not given [130] Mercuric oxide Glacial acetic acid 20.6 90-95 2 - 3 Not given . [131] Mercuric acetate Glacial acetic acid 15.9 100 2 73 [132] Mercuric acetate Glacied acetic acid 3.5 Water bath 9 92 _ [133] Mercuric oxide Glacial acetic acid 3 120 7 24 71 [134] Mercuric oxide Glacial acetic acid 13 120 2 78 17 [134] Mercuric oxide Acetic anhydride 9.7 120 7 80 15 [134] Mercuric oxide Acetic anhydride 13 120 7 72 23 [134] Mercuric acetate Glacial acetic

acid/ethanol 19.4 Boiled 55 80 — [135]

Mercuric acetate Nitrobenzene 9.2 130-135 3 80 [137] Mercuric acetate Dichlorobenzene 8.2 130-135 1 Not given - [ 125 a, 136] Mercuric oxide Glacial acetic

acid/methanol 1.5 70 10 25 - [138]

Mercuric oxide Glacial acetic acid 17.5 110 3 Not given — [139] Mercuric acetate Glacial acetic acid,

acetic anhydride, Cd and Cu nitrates

4 Boiled 6 - 7 80 [ l40 ]

Mercuric nitrate 20% acetic acid/urea 4 75-85 3 27 — [141] Mercuric nitrate Glacial acetic acid 10 75-85 1-1V4 80.5 - [141] Mercuric myristate - 1 120-130 2 - 3 95-100 - [142] P entachlorophenoxy- — Not given 130-135 3 Not given - [143]

mercuiy acetate [144] Mercuric acetate or HF1 BF31 or SbF3 Not given Low Short High - [144]

nitrate catalysts temperature duration [ l45 ] Mercuric monochloro — 500 80 12 21.9 - [ l45 ]

acetate


and with mercuric acetate in the presence of perchloric acid (and, to a lesser extent, in the presence of NaClO4) are considerably higher than the rate for mercuric acetate [152]. The mercurations of toluene and benzene under these conditions are of second order [152] (first order with respect to each hydrocarbon in the mercur-ation of the mixtures of toluene and benzene and with respect to the mercuric acetate [117, 118]).

With increasing time of mercuration of toluene under the above conditions, the isomeric mixture approaches the statistical distri-bution of 40% ortho, 40% meta and 20% para.

The mercuration of toluene with the mercuric salt of trinitro-methane (3 hours of boiling) gives a mixture of o - and p-mono-mercurated products in a total yield of 51.5% [147].

The isotopic effects in the mercuration of toluene, C6H5CI^, and C6H5CTs have been described in [154]. Themonomercuratedproduct was obtained by the action of mercuric acetate on toluene in the presence of H2Q> [122]. The dimercurated compound has been made by boiling toluene with mercuric acetate for 5 hours [155].

Mercuration of toluene with pentachlorophenoxymercury acetate (130-135°C, 3 hours) gave o- and p-tolylmercury pentachlorophen-oxides (the yields were not reported) [143].

Polymercurated products are obtained when an excess of mer-curic acetate in acetic acid is boiled for 12 hours with toluene (85-870C) or xylenes (IOO0C) [156, 157]. m-Xylene has been mer-curated [158] in position 4, in the cold, by mercuric acetate in glacial acetic acid in the presence of a little 70% HClO4. Replace-ment of a ring hydrogen by mercury occurs in mesitylene [159], pseudocumene [159], durene [159, 160], isodurene [159], 1,2,3,4-tetramethylbenzene [159], pentamethylbenzene [159] and p-cymene [161, 162] on prolonged boiling with mercuric acetate in alcoholic (polymethylbenzenes), acetate-alcoholic (j»-cymene [161] and durene [160]) or acetate (p-cymene [162]) solutions. Higher tem-peratures and longer reaction times lead to the formation of di-mercurated compounds. Below are given the relative rates of mercuration in a series of alkylbenzenes, calculated from partial rate factors [152] and agreeing with experimental values: benzene 1, toluene 5.0, o-xylene 16.0, m-xylene 34.5, ^-xylene 8.2, hemi-mellitol 68, pseudocumene 49, mesitylene 209, prehnitene 126, isodurene 257, durene 30.0, pentamethylbenzene 224, ethylbenzene 4.2, isopropylbenzene 3.9, t-butylbenzene 3.2.

Application of Hammett's equation to the mercurations of alkyl-benzenes shows, in particular, that these reactions depend on steric factors [163].

The mercuration of s-butylbenzene in the presence of hydrogen peroxide [126] has been described; the product is the monomer-curated compound.

Mercuration of t-butylbenzene [119] in glacial acetic acid (at 50, 70 and 90°C) gives about 70% of the p- and 30% of the ^- isomer;

MERCURATION 75

less than 1% of the o-product is formed. Under the same conditions, biphenyl gives 69-75% p-, 21-23% m- and 4-7.6% of the o-isomer [164].

In contrast to the earlier report [165], the boiling of fluorene with mercuric acetate gives, not the 4-substituted monomercurated product, but a di substituted compound [166]. The same product, and not a mixture of two products mercurated in positions 3 and 4 [165], was obtained [166] on fusing fluorene with mercuric acetate at 1450C. However, study of the partial rate factors in the mer-curation of fluorene which was carried out by reacting, at 25 0C, an excess of the hydrocarbon with mercuric acetate in acetic acid in the presence of benzene [164], showed that the main product was the 2-substituted monomercurated compound. Inalltheexperiments the products were identified by exchanging HgX for Br. The rate of the mercuration of fluorene was considerably higher than the rate of the mercuration of biphenyl under the same conditions, which may be explained by the former's planar structure due to the pres-ence of the methylene bridge [164].

Naphthalene is mercurated more readily than benzene and toluene; a - naphthylmercury acetate and an admixture of higher mercurated compounds, which was difficult to separate off, was obtained after 20 minutes of heating naphthalene with mercuric acetate to 120 0C [168].

High temperatures over 4-8 hours [169] (or longer [170]) and increased pressures are necessary for the mercurations of other condensed aromatic hydrocarbons (acenaphthene 115-120°C, an-thracene 130-140°C, phenathrene 120°C).

The mercuration of acenaphthene by heating at the above tem-perature for 15 hours with mercuric acetate and acetic acid in an autoclave gives a product substituted in position 5 in 28% yield [170]:

, + Hg(O2CCH3)2 A V 115-120° C

The mercuration of phenanthrene under the above conditions by mercuric acetate in acetic acid (in correction of earlier data [169]) gave three (1-, 3- and 9-) monomercurated products (total yield 25%) and two dimercurated products (total yield 25%) [170], The same compounds, and possibly some polymercurated products, were obtained during mercuration with mercuric acetate in nitro-benzene in the presence of HClO4 acting as the catalyst (40°C, 3 hours) [170]. The mercuration of phenanthrene in acetic acid with a solution of HgO in HClO4 (60°C for 6 hours or 30°C for 4 hours) yielded mono and dimercurated products. The reaction did not



proceed in the absence of acetic acid after 150 hours at room temperature [170].

When 5 moles of stilbene are heated for an hour at 130° C with 1 mole of mercuric acetate in glacial acetic acid, the salt does not add across the double bond but mercurates the ring, giving 2-, 3-and 4-substituted products and a little of the 4,4'-disubstituted compound [171]. For the addition of mercuric salts to the double bond in stilbene, see Chapter 6.

Polystyrene has been mercurated by boiling with mercuric acetate in acetic acid for IOhours [172]. Mercuratedpolystyrene containing one Hg atom per ring was obtained in practically 100% yield by heating nitrobenzene solutions of polystyrene and mercury di-isobutyrate for 20 hours on a water bath [173]. Polystyrenes have also been mercurated by heating to 130 0C for about 2 hours with mercuric acetate in acetic acid and also in the presence of HClO3. The mercury contents depend on the type of the polystyrene and on the conditions of the reaction [173a],

The heating of biphenylene and mercuric acetate in acetic acid on a water bath for 2 hours gives 2-acetoxymercuribiphenylene [174],

A dimercurated derivative of 3,4-benzopyrene was obtained by boiling the latter with an excess of mercuric acetate in acetic acid [175].

Of the monobenzenoid hydrocarbons, azulene [176] has been mer-curated; it proved to be more reactive than thiophene and furan and as reactive as pyrrole. Under the action of mercuric chloride in the presence of sodium acetate, azulene in alcoholic solution gives immediately at room temperature the dimercurated product C10H6Cl2Hg2. The positions of the Hg atoms in this compound have not actually been established, but mercury is evidently present in the five-membered ring. The compound is initially brown, but gradually becomes blue-gray.

The halogenated derivatives of hydrocarbons are mercurated by mercuric acetate under the same conditions as the parent com-pounds.

After boiling an equimolar mixture of f luorobenzene and mercuric acetate in glacial acetic acid for 12 hours only the o-mercurated product could be isolated, in a yield of 11% [177].

P-Fluorophenylmercury acetate was obtained after boiling for 2 hours [178], but the mercuration of an excess of fluorobenzene with mercuric acetate at 90°C gave 59.4% of p-, 6.9% of m- and 33.7% of the o-isomer (the bromofluorobenzenes obtained from the mer-curation products were separated by gas chromatography) [182], The yields of the o- and w-isomers fall off and that of the p-isomer increases as the temperature is lowered. Calculation of the partial rate factors shows a certain activation of the p-position by the fluorine atom, strong deactivation of the m-position and slight deactivation of the o-position [182],

When chlorobenzene is fused with mercuric laurate for 2 hours

MERCURATION 77

at 130-140°C, the yield of the monomercurated product reaches 95-100% [142]. The mercuration of an excess of chlorobenzene with mercuric acetate at 90°C gave 30% of the o-, 21.5% of the m- and 48% of the p-isomer [182]. The main product of the mer-curation of chlorobenzene by boiling with an equimolar amount of mercuric acetate for 2% hours at 140°C is the p-isomer [172, 179] (yield: 40% [179]) (see also [133, 180]). Outoftheproducts of the mercuration of bromobenzene under the same conditions it was found possible to isolate the p-isomer (yield: 25%); the o-and m-isomers were also obtained, but the yields are not reported [179]. When the reaction was carried out in a sealed tube at 120°C, the products contained the o- and p-dimercurated compounds [181]. Under the conditions described above for the mercuration of fluoro-benzene and chlorobenzene at 90°C, bromobenzene gives 28%of the o 26% of the Tn - and 46% of the ^-isomers [182].

All the positions in the ring are deactivated during the mercura-tion of chloro- and bromobenzenes, particularly the m- and o-posi-tions. The order of reactivity is F > H > Cl > Br for the ^-position and H > Cl = Br > F for the m -position. A clear lineardependence is observed between log (K/ Kfj) and the electrophilic substitution constant a+ in the mercuration of mono substituted benzenes (in-cluding the halogenobenzenes) [182]; in these cases the value of p for the mercuration is -4.0.

On being heated with mercuric acetate for 1% hours at 140 0C, iodobenzene gave only 4% of the ^-isomer [179]. The remaining products were not identified.

Boiling ?-dichlorobenzene with mercuric acetate without a solvent or in acetic acid gives a mixture of the monomercurated, all three dimercurated, and tr i- and tetramercurated products [183]. According to Petrovich [184] the monomercurated product is obtained in acetic acid solution at 125°C; unexpectedly, pro-longed heating yields (2,5-Cl2C6H3)2Hg. The monomercurated com-pound can be obtained under the last-mentioned conditions with an equimolar mixture of mercuric acetate and p-dichlorobenzene only when the reaction is not carried out to the end, or by prolonged boiling of a threefold excess of p-dichlorobenzene with mercuric acetate [183].

Trichlorobenzene gives the monomercurated product after boiling with HgCl2 and isopentanol for 5 hours [185],

p-Dibromobenzene was mercurated by heating with mercuric acetate to 120 0C for 4 hours in a sealed tube (the product was a dimercurated derivative substituted in positions 2 and 5) [181].

On being fused with mercuric acetate, /3-bromonaphthalene gives a-acetoxymercuri-/3-bromonaphthalene [186].

The mercurations of nitrated hydrocarbons are more difficult than the corresponding reactions with the parent compounds. Nitrobenzene is mercurated on being heated to 150°C with mer-curic acetate in the absence of solvent [169], The main product is



the o - isomer, together with some p-product and up to 40% of the Tn —derivative [1, 187-191]. As has been shown by Klapproth and Westheimer [1], this disorderly distribution of the isomers is found in the mercurations by mercuric acetate; on the other hand, in the mercuration of nitrobenzene with mercuric perchlorate in 60% HClO4 (8-10 days at room temperature) the products are 89% m- and 11% o-/p- and in 40% HClO4 (11 hours at 95°C) 63% m - and 37% o-/p- [1],

In their experiments on the mercuration of nitrobenzene with mercuric oxide in nitric acid over 7 hours at 99 °C and with mer-curic acetate for hours at 1550C, Ogata and Tsuchida [192, 192a] did not find any essential difference between the percentage dis-tributions of the isomers. The f irst of these mercurating agents gave 37% of the o-product 56.5% m- and 6.5% p- , and the second 27% 0 - , 67% m- and 5.5% p-.

Depending on the conditions, 0- and p-nitrotoluenes are mercur-ated either in the ring or in the side chain: boiling in alkaline solu-tion with HgO gives nitrobenzyl [193] and nitrobenzylidene [193, 195] derivatives, whereas heating to 140-1500C with mercuric acetate in the absence of solvent results in mercuration into the ring [194, 196, 197]. The mercury salt of trinitromethane does not mercurate nitro compounds, forming only, with some of them, complexes having the composition NO2C6HsHg [C(NO2)3J2 [198].

Mercuration of benzene [ l49, 109]. Heating of thiophene-free benzene for several hours with dry mercuric acetate at 110-120°C gives phenylmercury acetate (m.p. 149°C) and benzene-insoluble o -di(acetoxymercuri)benzene C 6 H 4 (HgO 2 CCH s ) 2 .

Preparation of phenylmercury acetate in the presence of ethanol [ 135 ] . Amix ture of 80 ml of benzene, 15 g of mercuric acetate and 20 ml of 95% ethanol are refluxed on a water bath and the yellow precipitate (which appears immediately) is dissolved by the addition of a few mil l i l i ters of glacial acetic acid. Another 20 ml of alcohol are added after 5 hours. About 1 g of mercurous acetate separates out after 55 hours and is f i l tered off. The fi ltrate is evaporated to dryness on a water bath and the residue re-crystall ized from 95% alcohol; m.p. 149°C; yield: 12.6 g (80%).

Mercuration of benzene in glacial acetic acid at IOO0C [ 130]. A solution of 50 g of mercurous acetate in 50 ml of glacial acetic acid in a thick-walled container, is mixed with 100 ml of thiophene-free benzene. The vessel is closed and heated for 5 hours on a boiling-water bath. After cooling, fi ltration of the insoluble material and washing with several portions of benzene, evaporation of the f i ltrate gives phenylmercury acetate. T o obtain the chloride, the f i l trate should be treated with alcoholic CaCl2 after evapora-tion of a large part of the benzene. The precipitate should be f i ltered off, washed with hot water and dried. Theresult ingphenylmercurychloridecanbe recrystal l ized from alcohol; m.p. 252°C. (The m.p. of carefully purified C6 H5HgCl is 271°C (cf. [200]).)

Preparation of trinitromethylphenylmercury [ 147]. (1) Preparat ionof themercurysal t of trinitromethane. An ethereal solution (1:1 by volume) of 20 g (0.13 mole ) of trinitro-methane is added in small portions, at room temperature, to 16 g (0.07 mole ) of freshly prepared mercuric oxide in 50 ml of ether (the mercury salt of trinitromethane can be obtained quantitatively in aqueous or alcoholic solutions). The temperature r ises to 30°C during this addition. The mixture is st irred for 15 minutes and the unreacted HgO f i l tered off. Evaporation of the f i l trate gives the required product in the form of a thick pale-yellow oil which crystal l izes in 5-6 hours. The crystals are separated off from the oil on

MERCURATION 79

a porous plate; yield: 26.5 g (80%). The material decomposes at 200-205°C. The com-pound is readily soluble in water, alcohol, chloroform, acetone, benzene, ether, ethyl acetate and acetic acid, but insoluble in petroleum ether, hexane and iso-octane.

(2) Preparation of trinitromethylphenylmercury. A 5-g portion of the mercury salt of trinitromethane is dissolved in 20 ml of benzene and 3 ml of ether (the latter is added to improve the dissolution), the traces (50-100 mg) of inorganic decomposition products of the Hg salt are f i l tered off and the f i l trate heated at 85-90°C fo r 5 hours. The hot solu-tion is then f i l tered and the trinitromethylphenylmercury crystals appearing f rom the cold f i l trate separated and washed with a few portions of water. A further 0.5-g portion of the product is obtained by evaporating the mother liquor to 5-10 ml at 250 mm. The total yield is 2.5 g (58.5%). Recrystall ization f rom C C I 4 gives 2 g of pure product m.p. 146°C.

Mercuration of toluene [ 14*)]. Mercuric acetate (1 part by weight) and toluene (5 parts) react rapidly with each other on boiling under reflux, with the formation of a c lear solu-tion. Some sparingly soluble material separates out on cooling. The f i l trate is then satur-ated with NaCl and the unreacted toluene distilled off with steam. The residue consists of a soft mass which solidif ies on cooling and which can be separated (with some dif f iculty) into two compounds by fractional crystall ization from benzene. The less soluble component (p-to ly lmercury chloride) is obtained in the form of beautiful crystals melting at 230-231°C, by recrystal l ization from chloroform or acetone.

Nevertheless, the above material contains admixtures of other isomers [201], The melting-point of pure p- to ly lmercury chloride is 232-233°C. The o - to l y lmercury chloride remaining in the benzene mother liquor cannot be fully separated f rom isomers by repeated crystall ization; m.p. 140-142°C instead of 145-146°C [149], According to Cof fey [150], mercuration of toluene (by boiling fo r 5-6 hours with mercuric acetate) yields also the m-isomer. The distribution is o:m:p = 43:13:44.

Preparation of 2,4-dimethylphenylmercury acetate C158 ] . Mercur ic acetate (32 g, 0.1 mole) and 3 ml of 70% HClO4 are added with stirring to a solution of 15 g (0.15 mole ) of m -xylene in 200 ml of glacial acetic acid and the solution stirred until the beginning of precipitation is observed. Themixture isthenpoured into twice its volume of water and the precipitate f i l tered off and crystal l ized from aqueous alcohol; m.p. 129-130.8°C.

The chloride melts at 155-156°C.

Mercuration of naphthalene [168], Mercuric acetate (30 g ) are added to 60 g of fused naphthalene and the mixture heated on an oil bath at 120 C, stirring and breaking up solidif ied material, until it becomes transparent (about 20 minutes). The excess of naph-thalene is disti l led out with steam and the residue dried and extracted with l igroine boiling at 100-120°C. The crystals of a -naphthylmercury acetate are purif ied by several recrystall izations f rom ligroine and alcohol; m.p. 154°C. Naphthalene mercurated in the a-posit ion is eas ier to isolate in the form of the chloride, and for this purpose the mix-ture is treated with a solution of sodium chloride before the steam-distil lation of naph-thalene. The residue is then dried, extracted with ether to remove any remnants of naphthalene and recrystal l ized f rom two volumes of pentanol. The boiling solution (slowly, on a water bath) is cooled to 80°C and the polymercurated compounds prec i -pitating out as a powder are rapidly f i l tered off. The residue coming out of solution on complete cooling of the f i l trate is extracted with cold chloroform and recrystal l ized from benzene; m.p. 189°C.

Preparation of 2-biphenylenylmercury acetate [ 174].

Biphenylene (0.3 g ) and 0.65 g of mercuric acetate in 10 ml of acetic acid are heated on a water bath fo r 2 hours, the resulting yellow solution diluted with water and the unreacted biphenylene (0.212 g ) rapidly distilled out with steam. The involatile sub-stances are col lected at 0°C and extracted in a Soxhlet extractor with warm benzene.



Yield: 0.187 g (79%). Crystall ization f rom benzene gives the required material in the fo rm of yellow powder; m.p. 176-177°C.

Mercuration of anthracene [ l 6 Q ] . Mercuric acetate ( IOg ) and 5 g of anthracene in 45 ml of acetic acid are heated in an autoclave to 130-140°C for 7-8 hours. A l l the anthracene dissolves within the f i rs t hour of heating, forming a dark red solution. The reaction mixture solidifies on cooling and is then heated with additional acetic acid on a water bath until most of it redissolves. The solution is f i l tered hot, the f i l trate evap-orated down to one-third of its volume and alcoholic CaCl2 immediately added. A white precipitate appears at once. This is washed successively with water, alcohol and ether and dried in a vacuum desiccator. The yield of grayish-yellow anthranylmercury chloride is 30%; m.p. 181-183°C. The substance is sparingly soluble in benzene and insoluble in most organic solvents.

Preparation of 2-acetoxymercuri-l,4-dichlorobenzene [183] , A mixture of 6.5 g (3 moles ) of mercuric acetate and 10 g (10 moles) of p-dichlorobenzene in 25 g of acetic acid is boiled for 5 hours, cooled and poured into water. The precipitated 2-acetoxy-mercuri-1,4-dichlorobenzene weighs 2.6 g and melts at 175°C after recrystallization from alcohol. The compound symmetrizes after more prolonged heating (about 11 hours) and, after boiling for 13 hours, the main product is bis-(2,5-dichlorophenyl)mercury.

Mercuration of nitrobenzene [ 168]. Mercuric acetate (1 part by weight) is heated on an oil bath to 150°C with nitrobenzene (5 parts) until complete dissolution takes place and no yellow precipitate of mercuric oxide is detected on testing with dilute caustic soda. A small amount of substance crystall izing in lustrous leaflets (0.6% on the weight of the mercuric acetate) appears on cooling and is removed by filtration. The f i ltrate is salted out with brine and the excess of nitrobenzene distilled out with steam. A semi-solid mass which solidifies on cooling, is left behind in the flask. This material is ground into powder and extracted with boiling ligroine (boiling-range 100-120°C); almost com-plete dissolution takes place. Cooling results in pale yellow needles of o-nitrophenyl-mercury chloride, which are further purified by recrystallization from glacial acetic acid. Very small yellowish leaflets; m.p. 181-182°C.

Mercuration of nitrobenzene with mercuric perchlorate [ l ] . Mercuric oxide (5.42 g ) and 10 ml of nitrobenzene are added to 250 ml of 60% perchloric acid in a 500-ml flask, the mixture set aside for several hours with occasional shaking and then allowed to react for 8-10 days at room temperature (23°C). It is then poured into twice its volume of ice-water and mixed nitrophenylmercury chlorides are salted out with aqueous NaCl. The precipitate is washed successively with water, 50% alcohol, ether and petroleum ether and then dried. Yield: 7.9-8.9 g; melting-range 215-221°C. The mixture, dissolved in chloroform, is then shaken for several hours with a solution of bromine in KBr and extracted with chloroform. The chloroform extracts are dried and the solvent evapor-ated off.

Determinations are of the percentage content of m-bromonitrobenzene and of the sum of o - and p -bromonitrobenzenes in the residue, basing the analysis on the fact that only the o - and p - i s omers form ammonium compounds with amines, are then carried out. For this purpose, an aliquot of the residue is heated f o r several hours with piperidine, the mixture poured into water and the aqueous layer washed with benzene. The bromide content of this aqueous layer (from the O- and p - i s omers ) is then determined by a Volhard titration. In this way, the sum of the O- and p- isomers is found to be 11%, the m- isomer accounting for the remaining 89%. See also [289],

Mercuration of o-nitrotoluene in alkaline solution. Preparation of 0-nitrobenzylmercury chloride and o-nitrobenzaldimercury oxide [193]. A mixture of 297 g (2 moles) of mer -curic oxide (obtained from HgCl 2 by precipitation with NaOH and well washed) and 2.5 l iters of water containing 44 g (2 moles ) of NaOH is heated to boiling on an oil bath in a flask fitted with a reflux condenser and an air-inlet tube. The latter serves merely to agitate the solution and may be replaced by a mechanical st irrer . o-Nitrotoluene (75 g, 1 mole ) is then added over 9 hours, in small portions, with a strong current of air bubbling through the solution. After a further I1A hours of boiling the mixture is cooled and the precipitate separated off f rom the yellowish-red solution. The product is yellow, with a

MERCURATION 81

gray ish-green tinge due to an admixture of metal l ic mercury . The weight of dry o -n i t ro-benzaldimercury oxide is 291 g (yield: 96%).

A total of 5.2 g of crude O-nitrobenzylmercury chlor ide is salted out of the mother liquor with an excess of hydrochloric acid. The mater ia l is purif ied by working up with alcoholic alkali in the cold, dilution with water and precipitation with HCl f rom the f i l -tered solution. The precipitated chloride is then dissolved in a large volume of warm dilute ammonia, f i l t e red with cooling, boiled and treated with HCl in the hot. This pro -cess is repeated severa l t imes, o -N i t robenzy lmercury chloride is obtained in the f o rm of co lor less bundles of needles; m.p. 145-146°C.

Baur et al. [202] described compounds having the general formula MHg2(SCN)glArH, where ArH is benzene, toluene, xylene, or naph-thalene.

c) Mercuration of Aromatic Hydroxy Compounds

Phenols form one of the most readily mercurated classes of compounds. The monohydroxylic phenols require heating (on a boiling-water bath) with an aqueous solution of mercuric acetate or mercuric oxide, not infrequently in the presence of alkali. When mercurated in this way, phenol itself gives two monomercurated products (o- and p-) and a 2,4-dimercurated compound [71, 149, 199, 203], No dimercurated compound is formed when phenol is fused with mercuric acetate without a solvent. On melting at IOO0C the main product is the p-isomer [204], whereas melting at 170°C yields the o-isomer [205], A second mercury atom can also be introduced into monomercurated phenols, in the presence of alkali and NaCN, by the action of mercuric chloride [206]. The monomer-curated o-compound is formed when an excess of molten phenol is poured into a boiling solution of mercuric oxide in acetic acid [155].

Trimercurated phenol 2,4,6-(CH3COOHg)3CgH2OH.3CH3COOH m.p. 116-120°C (34.5 g) was obtained after boiling, for 5 minutes, a mixture of 65 g of HgO, 10 g of phenol and 200 ml of glacial acetic acid [155], Compounds 2,4,6-(XHg)3C6H2OH, with X = NO3

or CN, were prepared in the same way [155], The rate of the mercuration of phenol with mercuric acetate

increases in the presence of HNO3, and particularly in the pres-ence of HClO4; on the other hand, the rate is reduced by additions of acetic acid [207]. In the presence of acids, the reaction is kin-etically of second order [207].

Mercurating agents other than mercuric oxide or mercuric acetate can also be used successfully, such as mercuracetamide, HgOH(CN) [208] (mercuration of p-cresol and m-xylenol) and mercuric chloride in the presence of NaHCO3 and glycerol. This mixture was used to mercurate phenol [209], a - and /S-naphthol, thymol, carvacrol and p-nitrophenol, with the formation of the corresponding monomercurated compounds. However, compounds containing an Hg-O linkage were formed in many other attempts to carry out mercurations with the above mixture.



The same conditions as for phenol, i.e. heating of aqueous or aqueous-alcoholic solution with HgO or mercuric acetate or fusion with a mercury salt with the absence of solvent, can be used to mercurate chlorophenols [182, 210, 211, 253], p-fluorophenol (even in the cold) [178] and nitrophenols [182, 210-215, 238], The effects of the solvent on the structures of the products are seen in the example of the mercuration of o-nitrophenol: whereas fusion withmercuric acetate gives 6-acetoxymercuri-2-nitrophenol, reaction in aqueous solution results mainly in 4-acetoxymercuri-2-nitrophenol [214]. The same conditions as for phenol itself can also be used for dinitrophenols [216] and phenol homologs (cresols [9, 71, 122, 181, 208, 210, 217-220, 223], xylenols [208], thymol [9, 71, 224, 225], carvacrol [225], p-t-butylphenol [226], isoamyl-phenol [226], o- and p-cyclohexylphenols [227], o- and p-benzyl-phenols [227] and naphthols).

Depending on the relative proportions of the reagents, a-naphthol gives a 2,4-dimercurated compound or a 4-monomercurated de-rivative [186, 228]; mercuration with HgCl2 in the presence of NaHCO3 and glycerol [229] gives only the monomercurated sub-stance. The action of mercuric acetate in acetic acid on /3-naphthol in the cold [230] results in an a-monomercurated product [228, 230, 231]. Mercuration with mercuric chloride in the presence of sodium bicarbonate and glycerol [229] gives a compound which contains the mercury in some other position. For the preparation of the above a-monomercurated compound from 2-hydroxy-l-naphthoic acid, see Chapter 9.

Monomercurated compounds have been obtained by standing cold aqueous-alcoholic solutions of mercuric acetate (0.5 mole) with the following alkylphenols ( lmo le ) : l , l ' -bis-(4 '-hydroxy-6-methyl-phenyl)cyclohexane, l,l '-bis-(4-hydroxyphenyl)cyclohexane, and 4-a, a, y, y-tetramethylbutylphenol [232], Derivatives of the last three [232] and of 2,2,5,5-tetra-(4'-hydroxyphenyl)hexane [232, 233] containing two mercury atoms in each phenolic ring were obtained by boiling aqueous-alcoholic solutions of these phenols with mer-curic acetate (taking 1 mole of mercuric acetate for every unoccu-pied o-position in the phenol).

Conditions analogous to those for phenol, or more vigorous ones, were used to mercurate halogenated alkylphenols [234-236], in particular chlorocresols [237], halogenoxylenols [208, 222],chloro-[239] and iodo- [240] thymols, halogenated arylphenols [241] (chloro-substituted o-hydroxybiphenyl by heating for 2 hours at 140°C [241]) and nitroalkylphenols [236] (nitrocresols [242-245], nitroso- and halogenonitrosothymols [239] and nitro- [186, 214, 246] and dinitro- [246] naphthols).

3-Nitro-4-hydroxybiphenyl boiled in an aqueous-alcoholic medium with mercuric acetate gives an almost quantitative yield of the monomercurated product [247].

For the action of fully substituted organomercury compounds and

MERCURATION 83

of organomercury salts on phenol and on substituted phenols, which according to the authors of the corresponding papers leads to mer-curation, see Chapter 12.

Mercuration of phenol in aqueous solution [l4*>, 1*)q], Mixing of concentrated aqueous solutions of phenol and mercur i c acetate at room temperature g ives r i s e to slow p rec i -pitation of a considerable amount of white crystal l ine needles O fHOC 6 H 3 (HgOCOCH 3 ) 2

(m.p. 216-217°C) collecting into spherical aggregates. The precipitation is very rapid when the above mixture is heated on a water bath. The mother liquor contains two other compounds, best isolated as the chlorides in the fol lowing manner. The hot solution is treated with NaCl and the resulting precipitate immediately f i l tered off . Th is mater ia l is mainly p-hydroxyphenylmercury chloride; the corresponding 0-compound is obtained f r om the mother l iquor in the f o rm of beautiful spear-shaped crysta ls . T h e p-compound can be puri f ied by repeated crys ta l l i za t ion f rom acetone (m.p. 224-225°C) and the o -cora-pound by crysta l l i zat ion f rom alcohol (m.p. 152.5°C).

Mercuration of phenol in the absence of solvent [204 ] . Mercur ic acetate (25 g ) is gradually added, with stirr ing, to 12 g of phenol fused by heating on a water bath. When the mercury salt d issolves, boiling water is added and the system le f t to boi l f o r a few more minutes. Addition of hot aqueous solution of 5 g of NaCl produces immediate p r e -cipitation of p-hydroxyphenylmercury chloride, which is f i l t e red off hot. A f t e r having been cooled, the f i l t rate yields crysta ls of tf-hydroxypheny lmercury chlor ide. The yie ld of the P - and 0 - i s o m e r s is, respect ive ly , 18 and 7 g .

When the above reaction was carried out atl70°C, the main pro-duct was the o-isomer (cf. [205]).

Dimercurated phenol has been made by fusing the phenol with mercuric acetate, isolating the product as the oxalate; the latter has also been prepared by boiling phenol, oxalic acid and HgO in water for 10 hours [248].

Preparation of the internal phenoxide of o-hydroxymercuriphenol [149 ] .

0-/

O-C6H4

\ H g +

This compound is obtained as a white precipitate when carbon dioxide is passed into an alkaline solution of 0-hydroxyphenylmercury chloride. It is sparingly soluble in most organic solvents.

Mercuration of p-cresol [71 ] . A solution of 10.8 g of p - c r e s o l in a small amount of alcohol is added to 21.6 g of HgO in 500 ml of water and 18 g of glacial acet ic acid and the mixture heated on a water bath. In the cold the reaction requires 2 days to proceed to completion (negative NaOH test f o r the mercur i c ion), whereas the corresponding time at 90°C is only 30 minutes. Only the dimercurated compound is fo rmed when the reaction is car r i ed out with heating on a water bath. Almost pure crystals of 3,5-di (acetoxy-m e r c u r i ) - p - c r e s o l (containing 1 molecule of water of crysta l l i zat ion) are separated off; they decompose around 200°C with the appearance of a red color . Hot mother liquor is worked up with aqueous sodium chlor ide and the resulting precipitate extracted with cold alcohol. The alcohol extract is concentrated and the 2 - ch l o r omer cu r i - p - c r e so l is p re -cipitated out with water and recrys ta l l i zed severa l t imes f r om benzene; m.p. 166cC.

Preparation of 2-hydroxy-l-naphthylmercury acetate [230]. HgO (20 g ) is dissolved in 520 ml of hot g lac ia l acetic acid. The solution is cooled, the small amount of insoluble lustrous leaf lets f i l t e red off and the f i l t ra te mixed with a solution of 13.2 g of /3 -naphthol



in acetic acid. A heavy, crystall ine precipitate of /3-hydroxynaphthylmercury acetate appears almost at once. The amount of this product increases after several hours, re -sulting in a quantitative yield. After a single recrystall ization from glacial acetic acid the compound melts at 185cC on rapid heating (with decomposition).

Mercuration of 3-naphthol with HgCl2 and NaHCOg in the presence of glycerol [229]. Preparation of 2-hydroxy-l-naphthylmercury chloride. A solution of 4.3 g of /3-naphthol in 50% alcohol is treated with 15 ml of glycerol and then with a solution of 8.1 g of mer -curic chloride in 50% alcohol till precipitation no longer takes place. An aqueous-alco-holic solution of 2.5 g of NaHCC>3 is then added, with energetic stirring, resulting in the appearance of a yellowish precipitate and in abundant evolution of CO 2 . A f t e r s e v e ra l hours the precipitate is f i l tered off and washed with very dilute HCl and with water; m.p. 180°C (from alcohol; with decomposition).

Mercuration of O-nitrophenol [213] , A solution of 22.3 g of mercuric acetate in 200 ml of water and 1 ml of glacial acetic acid is added dropwise to a warm solution of 10 g of o-nitrophenol in 200 ml of water and 10 ml of 40% NaOH. An orange precipitate appears at once. After 2 hours of stirring, the above material (which has now become yellow) is f i l tered off and washed carefully with water containing a little acetic acid. The crude pro-duct is dissolved as far as possible in 5% NaOH, f i l tered, reprecipitated with acetic acid, f i l tered again and washed successively with water, methanol and ether to remove the last traces of nitrophenol. Yield: 16.5 g. The material is a mixture of mono- and dimercurated compounds (mainly 4-acetoxymercuri- but also 6-acetoxymercuri-2-nitrophenol and 4,6-di(acetoxymercuri)-2-nitrophenol). Almost pure monomercurated compound can be separated from this mixture by fourfold recrystall izations from glacial acetic acid.

- Dissolution of the latter material in dilute alkali, f i l tering off of the insoluble residue and reprecipitation with hydrochloric acid yields a solid which is washed f r e e from inorganic halide with water and then extracted with several portions of boiling methanol. The insoluble residue is a mixture of mono- and dimercurated products. The methan-olic f i l trate yields clusters of cream-colored crystals of 4-chloromercuri-2-nitrophenol (m.p. 205° C [214]) and yellow-brown plates of 6-chloromercuri-2-nitrophenol (m.p. 185°C [214]).

Sodium 4-hydroxymercuri-2-nitrophenoxide (mercuriphene). This can be obtained [213] f rom either the chloride or the acetate, by dissolution in dilute NaOH1 fi ltration f rom any insoluble residue and concentration of the f i l trate under vacuum. A red precipitate appears on cooling. This is carefully washed with ice-cold water and recrystal l ized f rom hot water.

The mercuration is further facilitated by the presence of several hydroxyl groups in the molecule resorcinol [71, 249-256], saligenol [257] and phloroglucinol [249] are mercurated in aqueous solutions in the cold (saligenol also in alcoholic solution on heating). A mono-mercurated product is obtained only in the case of resorcinol; saligenol gives the dimercurated and phloroglucinol solely the trimercurated compound. Nitrosaligenol and p-hydroxyphenylcar-binol and its nitro derivative have been mercurated in the same way [257].

Mercuration of resorcinol [71 ] , A solution of 28.3 g ( I m o l e ) of finely ground mercuric acetate in 60 ml of water, prepared at room temperature, is gradually poured, with st ir-ring, into a solution of 29.7 g (3 moles) of resorcinol in 25 ml of water. The reaction is complete in 15 minutes (negative NaOH test for precipitation of mercuric oxide). P ro -longed standing should be avoided because it leads to the precipitation of a mixture of mercurated resorcinol acetates which are difficult to separate. The solution is rapidly f i l tered (from the precipitating f lakes) into a concentrated solution of sodium chloride; a mixture of chloromercuri- and bis- (chloromercuri )resorcinols separate out within a short time. This mixture is set aside for a certain time on ice and then f i l tered. The precipitate is washed with ice-water, dissolved in a large volume of ether, separated

MERCURATION 85

f r om traces of g ray residue, f r e ed f rom the ether by evaporation (at the end under vacuum) and dr ied in a vacuum desiccator at room temperature. The y ie ld is 16 g (the mother l iquor sti l l contains an appreciable proport ion of the mater ia l , but this is d i f f i -cult to extract in pure f o rm) . The precipitate is a mixture of mono- and dimercurated resorc ino ls and can be separated by working up with a large volume of boil ing chloro-f o rm in which the dimercurated compound is insoluble. Repeated recrysta l l i za t ion f rom chloro form y ie lds C H C I 3 - containing 4 -ch loromercur i resorc ino l , in the f o rm of p r i sms melt ing at 105° C. The compound can be f r eed f rom the ch loro form by storage in vacuum over paraf f in; the melt ing-point then r i s es to 123°C, and a deep red co lo r appears at 170°C. The ch loro form- inso luble residue is dissolved in a smal l amount of ether. Evap-oration of this ethereal solution y ie lds 2.5 g of 4 ,6-d i ( ch loromercur i ) resorc ino l , a powder darkening at about 200°C.

Trimercurated resorcinol has been made by the action of an ex-cess of alcoholic mercuric acetate [256], Underthe same conditions, the action of 1 or 2 moles of mercuric acetate on ethyl- and hexyl-resorcinols yields the corresponding mono- and dimercurated derivatives [256],

Monomercurated 5-methyl- and 4-chlororesorcinols are obtained [9] when equimolar proportions of the phenols and aqueous-alcoholic mercuric acetate are left to stand in the cold.

Mono- and polymercurated products of 0, 0'- and p, p'-di(hy-droxyphenyls) [258, 259] and of d i -o-cresol [259] have been made by heating the polynuclear phenols with aqueous or alcoholic mer-curic acetate at 40-50°C.

On the other hand, polyhydroxylic phenols with 0- or p-hydroxy groups (pyrocatechol [257, 260], hydroquinone, pyrogallol) are not mercurated but oxidized by mercuric salts.

Nitroresorcinol was mercurated in 2 hours by heating on a water bath with aqueous mercuric oxide [213]. The product was either the 4-monomercurated [213] or the 2,4-dimercurated [261] compound. The latter is also obtained during mercuration with mercuric ace-tate [261], According to [261], the yield is reduced at higher values of pH. 2,4-Dinitroresorcinol forms the 6-monomercurated com-pound on reaction with mercuric acetate, at room temperature, if the pH is adjusted to 2.5-3.5 [261]. AtpH 4.6-6.0, the latter product contains also mercury linked to oxygen [261]. Mercurations of the mononitro and dinitro derivatives of hydroquinone and pyrocatechol cannot, however, be carried out with mercuric oxide or acetate be-cause of the reducing character of these phenols [261],

Replacement of the hydrogen atom in the OH group by an alkyl or aryl radical reduces the rate of mercuration, so that phe-nolic ethers are not mercurated as easily as the free phenols: on heating for 2 hours with mercuric acetate in the absence of solvent (anisole [71, 262], nitroanisole [237], phenetole and /3-thoxynaphthalene [186]), or on heating for several hours in aque-ous suspension (anisole, phenetole, methyl p-cresyl ether [263, 264]), in alcoholic solution (the dimethyl ether of resorcinol [265], methyl ethers of thymol and carvacrol [225]), or in acetic acid solution (diphenyl ether and its monobromo- and monoiodo- deri-vatives [226]). The products in all these cases are predominantly



the monomercurated compounds; see, however, [225, 263], The 2,4-dimercurated product was obtained f rom anisole and

mercuric sulfate in an aqueous solution acidified with H2SO4 [267] (temperature not given). Mercuration with HgSO4 gives the mono -substituted product with amyl phenyl ether, and the poly substituted product with diphenyl ether [267],

a-Mercuration of /3 -methoxynaphthalene with mercuric nitrate takes place at room temperature, whereas the action of mercuric sulfate leads to the formation of unidentifiable substances [268].

Kinetic measurements of the rates of mercurations (with mer -curic acetate in glacial acetic acid at 25°C) of anisole (1.85), P-methyl- (0.931), p-methoxy- (0.634) and p-t-butyl- (1.66) ani-soles and diphenyl ether (0.267) showed that the reactions are of second order; the f igures in parentheses are the rate constants [269]. Monomercurated p-methoxyanisole was obtained at 65°C [221 ] .

On boiling for 2 hours with 2 moles of mercuric acetate in 3:1 alcohol-acetic acid solution, guaiacol gave the 4,6-dimercurated product [270]:

5-Nitroguaiacol has been mercurated by prolonged boiling with mercuric acetate in dilute acetic acid [271, 272], giving both mono-and dimercurated products. Aroxy-substituted fatty acids (aroxy-acetic and aroxypropionic) are mercurated into the aromatic ring after prolonged heating on a water bath with mercuric acetate in acetic acid [273-275] or alcohol-acetic acid [275a] solution, with alkaline solutions of mercuric oxide, or by fusion with mercuric acetate in the absence of solvent [273, 274]. In contrast, the allyl ethers of phenol and /S-naphthol are mercurated after only 2-3 minutes of boiling with mercuric acetate in acetic acid, and no addition of mercury to the allylic double bond takes place [276],

Anathole subjected to the action of aqueous mercuric acetate is mercurated appreciably in the benzene ring [277].

The action of mercuric acetate in aqueous solution on eugenol (12 hours at room temperature) results in a product which may be mercurated in the ring [278].

The mercuration of phenolic ethers is facilitated if a hydroxyl group is introduced into the alkyl group: ring-monomercurated monoaryl ethers of glycols have been obtained by cold 0.5M alco-holic solution of mercuric acetate [279]. The dimercurated der iv-atives are obtained after 2-3 hours of boiling of the reagents in equimolar proportions [279].

OH

HgOCOCH3

MERCURATION 87

Preparation of p-anisylmercury acetate [ 7 1 ] . Dry mercur i c acetate (1 mo le ) and an excess of anisole (8 mo l e s ) are heated ona water bath until withdrawn samples no longer g i ve a yel low precipitate with NaOH. On cooling, the solution yields crysta ls of the r e -quired product, which are r ec rys ta l l i z ed f r om diluted alcohol; m.p. 176.5°C. The mother l iquor contains the a - i s o m e r .

Repetitionof this reaction under Dimroth's conditions (heating for 48 hours) showed [262] that the products contained about 65% of the p-mercurated product, less than 1% of the o-isomer and some dimercurated compound. Kinetic studies of the mercuration of anisole with mercuric acetate in glacial acetic acid at 25°C [119, 269] (second-order reaction) revealed that the products were 86% of the p- and 14% of the o-isomer. The partial rate factors for mercuration into these positions in anisole have also been es-tablished [119].

An alcoholic solution of anisole and the mercury salt of trinitro-methane heated for 30 minutes on a water bath gave a total yield of 41% of a mixture of o- and p-monomercurated products [147]. For several derivatives of the aromatic alkoxy compounds, the mercurations with mercuric acetate are satisfactorily described by Hammett's equation with the electrophilic substitution constant a*; p = -4.10 [269].

Preparation of the al lyl ether of p-chloromercuriphenol [276 ] , An excess of al lyl phenyl ether (15 g ) is poured into a mixture of 9 ml of 80% acetic acid and 37 ml of water and an emulsion f o rmed by shaking. A paste containing 6.5 g (dry weight) of mercur i c oxide is then added and the whole mixture boiled and st i r red into a boil ing solution of sodium chloride in 50 ml of water . The whole mixture is then boiled f o r a further 2-3 minutes and set aside to cool. The initially separating oil c rys ta l l i zes a f ter 2 hours and is recrys ta l l i zed f r o m chloro form. Y ie ld : 23.5 g (57% calculated on the HgO); m.p. of the pure compound is 101-101.5°C.

If the given molecule contains other functional groups in addition to the hydroxyl, the course of mercuration is determined by the presence of the OH. The same conditions as those for phenol and its homologs can be used to mercurate other aromatic hydroxy-compounds, and the mercurations of hydroxy aldehydes, hy-droxyketones, hydroxycarboxylic acids, hydroxysulfonic acids, hydroxyarsonic acids and phthaleins and other triphenylmethane hydroxy derivatives will therefore be considered in this chapter.

Salicylaldehyde [280, 281] in aqueous or alcoholic solutions is mercurated in the cold or on warming with the formation of 3,5-diacetoxymercuri derivative. The same method was used to mer-curate m- and p-hydroxybenzaldehydes, 2,4-dihydroxybenzaldehyde and phloroglucinaldehyde, obtaining dimercurated products [282], 3-nitro- and 5-nitrosalicylaldehydes [280] and nitro-w-hydroxy-benzaldehydes with the formation of mono- and dimercurated pro-ducts [283] and monomethyl ethers of dihydroxybenz aldehydes, for example vanillin [282, 284, 285], which is also mercurated after 10 hours of heating with alkaline HgO [286], and isovanillin [282]. The introduction of one Hg atom into dimethyl and trimethyl ethers



of gallic aldehyde required 4 hours of boiling with a solution of mercuric acetate in alcohol [287]. The mercurations of dialkyl-(the alkyl groups were CH3 and C3H7) and monoalkyl- (the alkyl groups were t-C4H9 and iso-C5Hn) phenol aldehydes were carried out by fusion with mercuric acetate in the absence of solvent [226], Hydroxyaryl alkyl ketones, for example hydroxyphenyl methyl ke-tone [108, 288, 289], halogenohydroxyaryl alkyl ketones [109] and their semicarbazones [108] were mercurated on being heated in the absence of solvent with mercuric acetate (or with some other mer-eurating agent, such as mercuric cyanide or sulfate) to 70-90°C for a period of about 1% hours.

Preparation of 5-hydroxymercurivanillin [280] ,

A hot solution of 100 g of NaOH in 100 ml of water is added to a solution of 136 g of HgCl2 in 400 ml of hot water; 25 g of vanillin are then stirred in and the mixture boiled (still with st irr ing) for 10 hours, cooled and f i ltered. The precipitate is washed with water and the combined washings and the f i l trate acidified with 1:3 H2SO4 . The resulting dense white precipitate is f i l tered off, washed with water and dried in vacuum. Yield: 40 g. Recrystall ization of this material from water, methanol, acetone or dioxan gives colorless needles of 5-hydroxymercurivanillin; m.p. 235°C.

Mercurated salicylic acid is obtained by boiling salicylic acid in water with freshly precipitated mercuric oxide [71] or acetate [291], and when mercuric salicylate (especially in the crude state) is set aside at room temperature [291]; the last-mentioned reaction proceeds more rapidly at 100-120°C [71, 291, 292], and Paolini recommended for it a temperature of 170°C [293]. Accordingto Rupp [294] and Boedecker [295], the product is a mixture of 3- and 5-hydroxymercurisalicylic anhydrides.

Perfectly pure 3-hydroxymercurisalicylic acid is obtained when mercuric sulfate is allowed to react briefly with salicylic acid [294]; however, according to Ukai [296] this product is mercurated in position 5. Sowa [267] believes that when mercuric sulfate solution is gradually added to a boiling aqueous solution of salicylic acid, the substitution occurs in position 4 with respect to the carboxyl.

Salicylic esters are mercurated by mercuric acetate in the ab-sence of solvent [297]: methyl salicylate reacts on boiling [297], and in the case of ethyl salicylate the substitution is quantitative only at 180°C [297].

Reports have been published on the mercurations of salicylic acid and its derivatives [298-302], salicylsulfonic acid [303], the glycol ester of salicylic acid [304], acetylsalicylic acid [253, 278, 305-307], nitrosalicylic acid [309, 313], phenacylsalicylic acid [290]

CHO

MERCURATION 89

and methylenedisalicylic acid [258] (the monomercurated product). Other aromatic hydrocarboxylic acids can also be mercurated on

boiling with mercuric salts in water, alcohol, or acetic acid, or by heating their mercury salts in water: m-hydroxybenzoic [301, 308, 310], p-hydroxybenzoic [253, 237, 301, 311], cresotic [312], resor-cylic (the mercuration of /3-resorcylic acid with HgSO4 in aqueous solution gives mono- and dimercurated products [313]), 2-hydroxy-3-naphthoic [258, 314], l-hydroxy-2-naphthoic [258], 5-alkyl-2,4-dihydroxybenzoic [315] (the alkyl groups were C2H5, n-C3H7, n-C4H9

and n-C5Hu) and 5-n-butyl-2,6-dihydroxybenzoic acid [315], gallic acid with two or three methylatedhydroxyls[ 287] and also p-phenol-sulfonic acid [317] and the following naphtholsulfonic acids [228]: 2-hydroxynaphthyl-6-sulfonic, l-hydroxynaphthyl-4-sulfonic and 1-hydr oxy naphthy 1 - 5-sulfonic.

Hydroxy- [318-320] and amino- [320] hydroxyarylarsonic acids are mercurated under the same conditions. Mercurationsofamino-hydroxyarylarsonic acids have been described by Maschmann[321],

Mercuration of sa l i cy l i c acid [ 7 1 ] . An equimolar mixture of f r esh ly precipitated mercur i c oxide and sal icyl ic acid is heated in water, on a water bath, until a withdrawn sample d isso lves completely in alkali. The resulting substance is d issolved in soda solution and then again precipitated out by carbon dioxide. The resulting internal salt of o -hydroxymercur i sa l i cy l i c acid is in the f o rm of f ine white powder and decomposes on heating without melt ing.

The above substance is identical with the pharmaceutical Hydrargyrum Saiicylicum. According to later data [293, 294], it is a mixture of the anhydrides of 3- and 5-hydroxymercurisalicylic acids. For the separation of such a mixture, see [295, 322].

Preparation of methyl 3-chloromercurisalicylate [207 ] . Mercur i c acetate (15 g), 15 g of methyl sal icy late and 2.5 g of g lacial acetic acid are boiled f o r 40 minutes under ref lux until the NaOH test f o r the mercury ion is no longer positive. The acicular crysta ls separating f r om the cooled solution are set aside overnight and then careful ly f i l t e red off . The y ie ld of this mater ia l , methyl acetoxymercurisal icy late , is 9 g (52%). The compound is pur i f ied by dissolution in boiling ethyl acetate, evaporation and r ep re -cipitation with petroleum ether; m.p. 202°C (with slight pre l iminary sintering).

The remaining 48% of the mercurated product canbe eas i ly and completely salted out of the mother l iquor with an aqueous solution of NaCl in the f o rm of crysta l l ine methyl 3-ch loromercur isa l i cy la te . Y ie ld : 36.6%. Total y ie ld: approximately 90%. The compound is puri f ied by dissolution in ethyl acetate and reprecipitat ion with petroleum ether.

The mercurations of hydroxy compounds, e.g. salicylic and 2,3-hydroxynaphthoic acids, are accelerated in the presence of alkali [314].

Mercuration of 3-hydroxy-2-naphthoic acid in alkaline solution [314 ] . A 30-g (0.16 mo l e ) amount of the acid in 500 ml of water and 150 ml (0.9 mo le ) of 6N NaOH is heated to boil ing and a solution of 52 g (0.16 mo l e ) of mercur i c acetate in 300 m l of water and I O m l (0.15 mo l e ) of acetic acid gradually s t i r red in. Immediate precipitat ion of HgO takes place. The mixture is boi led f o r a few minutes (at the end with animal carbon),



f i l tered, treated with an excess of aqueous NaCl and acidified with dil. HCl. The prec i -pitate (a yellow infusible powder) is apparently the internal salt of 4-hydroxymercuri-3-hydroxy-2-naphthoic acid.

Exactly the same procedure has been used to mercurate salicylic acid [314]; yield: 15 g of hydroxymercurated product. Likewise, 100 g of phenol yielded 215 gof anhydrohydroxymercuriphenol [314]. However, an attempt to mercurate a-naphthol in alkaline solution resulted merely in its oxidation. Similarly, o -nitrophenol could not be mercurated in alkaline solution [314].

Coumarin and its derivatives are mercurated in the nucleus without any involvement of the double bond (an exception is 7-hy-droxy-4-methylcoumarin; see below) only in the presence of alkali, by the action of mercuric acetate [323-327], HgO (on boiling) [323-325], and mercuracetamide [323]. The XHg group enters into posi-tions 6 and 8. The product obtained from coumarin and mercuric acetate has the structure

When mercuric salts are added to coumarin derivatives in the absence of alkali, the reaction involves addition to the double bond as well as mercuration (cf. Chapter 6).

However, in contrast to this general pattern of behavior, 7-hy-droxy-4-methylcoumarin boiled with mercuric acetate in methanol does not add the mercury salt but merely becomes mercurated in position 8 [328].

Hydroxy azo compounds can be mercurated with mercuric acetate in aqueous, alcoholic, or dilute acetic acid solutions, after a more prolonged heating (up to 7 hours) than that necessary for the cor-responding hydroxy compounds [329-331],

On being boiled in alkaline solutions with aqueous HgCl2, benzo-aurin and phenyldihydroxydibenzopyran form mono- and dimer-curated compounds [332].

According to Whitmore and Leuck [333], the presence of alcohol in the reaction medium during mercurations by mercuric acetate favors combination of the forming acetic acid and promotes poly-mercuration. Thus, in the mercuration of aurin with mercuric acetate, depending on the reagent ratio and on the solvent, the product was a compound containing either one atom of mercury in the molecule (1 mole aurin, 1 mole mercuric acetate, ethyl acetate/acetic acid as the solvent), or two (1 mole aurin, 2 moles mercuric acetate, alcohol/acetic acid as the solvent), or three (1 mole aurin, 4 moles of mercuric acetate, alcoholic solution). The action of 6 moles of mercuric acetate in acetic acid on 1 mole

:o

HgOCOCH3

MERCURATION 91

of aurin gave compounds I and II (Ac = CH3CO2):

I O II O AcHg Il HgAc AeHg || HgAc

W W

AeHg Il HgAe AeHg Il HgAe \ I / \ I /

H O - ^ - C - ^ - O H A e H g O - / ~ A - C - ^ ^ > - O H g A e / \ _ \

AeHg HgAe AeHg HgAe

Aurintricarboxylic acid boiled with mercuric acetate in acetic acid gives a trimercurated compound [258], containing one HgX group per ring. Naphthochrome Green was mercurated in the same way [258].

Phenolphthalein [334-336] and its homologs such as cresol-phthalein [335, 337], thymolphthalein [335], 3,3-bis-(4'-hydroxy-3'-nitrophenyl)phthalide [338]. fluorescein [334-337, 339, 340], ethyl- [341], hexyl- [341] and other alkylfluoresceins [342] (monomercurated products), 4,5-dinitrofluoresceins [338], hydroxy-fluoresceins [337], derivatives of diphenol- and diresorcinolisatin [343, 344] and other hydroxy compounds belonging to the triphenyl-methane series are mercurated in the phenolic ring in alcoholic, aqueous and frequently alkaline solutions on boiling for several hours. In most cases the mercuration proceeds in the position ortho with respect to a hydroxyl group, and several Hg atoms can be introduced into the molecule [334]. The action of mercuric ace-tate in alcoholic or aqueous solution, or in suspension, on phenol-phthalein itself results in the introduction of 3 instead of 4 mercury atoms. Boiling with mercuric oxide in weakly alkaline solution gives only monomercurated phenolphthalein [334]. Halogenated phenol -phthaleins [345], 2,7-dihydroxyfluorane [276] and the di- and tri-bromo derivatives of 6-hydroxyfluorane [346] have been mercurated in the same manner.

Mercuration of phenolphthalein with mercuric acetate [334]. Asolut ionof 3 g of phenol-phthalein in 50 ml of alcohol is mixed with a f i l tered solution of 25 g (8 mo l e s ) of m e r -curic acetate in 50 ml of water and 50 ml of glacial acet ic acid. No mercurat ion occurs when this mixture is set aside overnight at room temperature and only a l itt le prec ip i -tation of mercurous acetate is observed. The latter is f i l t e red off and the f i l t rate is heated on a water bath. Rosettes of dense leaf let crysta ls appear after 2 hours. The m i x -ture is then heated f o r a further hour and set aside overnight. The crys ta l paste is f i l t e red off, washed f r e e f rom unreacted phenolphthalein with alcohol and then f rom ex -cess mercur i c acetate with water, and the crysta ls dr ied ( f i rs t in a i r f o r severa l days and then f o r 1 hour at 100°C). The resulting triacetoxymercuriphenolphthalein is insol-uble in organic solvents but d isso lves in aqueous NaOH to g ive a dark red solution.

Mercuration of phenolphthalein with HgO in alkaline solution [334 ] . A solution of 3 g of phenolphthalein in 25 ml of IN NaOH is made up to 150 ml with water and then boiled f o r 3 hours with 3 g of ye l low mercur i c oxide. The small amount of gray precipitate which


TOO 102 ORGANOMERCURY COMPOUNDS

forms as a result of this operation is separated off by sedimentation over a few days in a tall cylinder and its last traces removed by centrifugation. Monomercurated phenol-phthalein is precipitated from the f i l trate with CO2 as a reddish mass of cheese-like consistency. This is removed by centrifugation, dried on a water bath, washed with alcohol and dried at 110°C. The substance is infusible and insoluble in the usual solvents, but dissolves in glacial acetic acid to give a turbid solution. It does not crystal l ize.

Mercuration of fluorescein [334] . Fluorescein (3.3 g ) is dissolved in 200 ml of 0.12 N NaOH and the solution acidified with 5 ml of glacial acetic acid. A f i l t e r ed solution of 25 g (8 moles ) of mercuric acetate in 200 ml of water (slightly acidified with CH3COOH to avoid hydrolysis) is then added and the mixture boiled for 10 hours, keeping the total volume constant by additions of water. The product is freed from mercury by centri-fugation, washed and dried. During the washing some of the substance is lost, forming a fine suspension. Yield: about 10 g. The product is a mixture of tetrahydroxy- and tetra-acetoxymercurifluorescein, with a predominance of the former . The substance is in-soluble in the usual solvents and dissolves in alkalis.

Dibromofluorescein is mercurated by mercuric acetate [334, 336, 347-350] in CH3COOH or by mercuric oxide in alkaline (see however [334]) solution on heating [347, 348]. Thedegreeof mercuration and the product composition depend on the duration of heating and on the pH value [347, 348]. Eosin heated on a water bath with aqueous mercuric acetate gives the monomercurated derivative [351],

The conditions described for phenolphthalein fluorescein and their derivatives can also be used to mercurate other halogen derivatives of fluorescein [336, 352, 353], phenolsulfonephthalein [335, 354], the latter's alkyl derivatives [335], resorcinolsulfone-phthalein [355, 356], the latter's halogen derivatives, salicylsulfone-phthalein [357], resorcinolsuccineins [336], "sacchareins" [336], the halogen derivatives of resorcinolsaccharein [358, 359] and the compounds similar to the latter. The products contained one, two and sometimes more mercury atoms in the positions ortho to the hydroxyl groups.

Mercuration of dibromofluorescein [334] . Preparation of 4-hydroxymercuri-2,7-di-bromofluorescein.

2,7-Dibromofluorescein (40 g ) dissolved in a solution of 8 g of NaOH in 50 ml of water and diluted to 200 ml is stirred and treated with 12.5 ml of glacial acetic acid. A viscous precipitate appears on vigorous stirring. A solution of 22.5 g of HgO (the theoretical amount is only 21.7 g, but an excess is used to provide f o r the possible loss in the form of Hg2O which usually forms when commercial HgO is dissolved in CH3COOH) in acetic acid and 50 ml of water, diluted to 100 ml and fi ltered, is then added to the solution of the dye and the whole volume is diluted to approximately 500 ml. The mixture is boiled for 41^-6 hours, till the (NH4)2SO4 test for the mercuric ion is negative. The resulting dark

HgOH

Il O

MERCURATION 93

granular precipi tate is di f f icult to f i l t e r and is there fore removed by centri fugation f r om the acetic acid and sodium acetate and f inal ly dried at I l O c C . The y ie ld is a lmost quan-titative.

The compound is a red powder with c lear ly expressed e lectr ica l propert ies . It is in-soluble in the solvents but d isso lves in 2 equivalents of NaOH. The sodium salt of 4 -hydroxymercur i -2 ,7-d ibromof luoresce in is known commerc ia l l y as "mercurochrome" .

Aromatic alcohols are mercurated under more vigorous condi-tions than the phenols; for example, benzyl alcohol requires 6 hours of boiling with mercuric acetate in aqueous solution [360]; the same applies to phenylethanol [361], Both alcohols give two products monomercurated in positions 2 and 4, and <y-phenylpropanol under the same conditions also gives two mono substituted products, but mercurated in position 3 and 4 [361],

Mercuration of benzyl alcohol [360 ] , Mercur i c acetate (45 g ) and 15 g of the alcohol are boiled f o r 6 hours in 25 ml of water, the f i l t ra te added drop by drop to saturated aqueous NaCl and the resulting precipitate is f i l t e red off . Y ie ld : 46 g. A 10-g portion of this mater ia l is extracted with hot water and the solution cooled. The precipitate, recrys ta l l i zed f r o m water or sublimed, g ives 5.6 g of 2-ClHgC 6H4CH20H; needles, m.p. 120-120.5°C. Alcohol extraction of the mother l iquor or the residue yie lds 1.4 g of 4 -C lHgC e H 4 CH 2 OH; m.p. about 250°C.

The thiophenols themselves, possessing a free sulfhydryl group, form stable mercury thiophenoxides with mercuric salts (cf. Chapter 16).

Generally speaking, the introduction of mercury atoms into thio compounds is less easy and smooth than the mercuration of their oxygen analogs. Thus, methyl phenyl sulfide has been mercurated in a yield of approximately 40% by heating with mercuric acetate on a steam bath [362, 363] and by boiling with mercuric acetate in isoamyl acetate [364],

Diphenyl sulfide reacts with mercuric acetate in boiling isoamyl acetate (141-142°C) [364, 365],

Under the same conditions [364], and also on heating the com-ponents without a solvent to 170-180°C [366], diphenyl sulfone gives the monomercurated product.

Boiling of the alcoholic solutions of o, o'- and p, p' -dinitrodiphenyl disulfides with mercuric acetate results in the internal salt of the corresponding mercurated nitrothiophenols [367],

The dimercaptan dibenzyl ether

d) Mercuration of Thiophenol Derivatives

RS SR

CCH;

HC CH

Il S



(R = C6H5CH2) is mercurated under conditions similar to those used in the mercuration of thiophene, i.e. by the action of HgCI2 in the presence of sodium acetate in boiling alcoholic solution [368], giving a product dimercurated in positions a, a ' to the thione group. The monomercurated derivative of the corresponding dimethyl ether separates out in the cold under the action of methanolic mercuric chloride [368].

The mercurations of 4-hydroxy-, 2-methyl-4-hydroxy-, and4,4'-dihydroxydiphenyl sulfides occur smoothly after 30 minutes of heating in aqueous-alcoholic mercuric acetate [369], giving respec-tively mono- and dimercurated products. The f irst two compounds give monomercurated products, and the third one a dimercurated product. Alcoholic solutions of thiosalicylic acid give the mono-mercurated product after standing for 24 hours in the cold with a solution of an equimolar amount of HgO in dilute acetic acid [253],

On the other hand, the mercuration of S-methylsalicylic acid proceeds to completion only at 2300C and leads to the formation of unidentifiable products [365],

The mercuration of dithiosalicylic acid has been described [293],

Preparation of p-phenylmercaptophenylmercury acetate [365]. D ipheny l su l f i d e ( IOg ) and 20 g of mercuric acetate in 50 ml of isoamyl acetate are boiled for 5 hours after which time a withdrawn sample gives no black color with ammonium sulfide. The solution is f i l tered hot f rom the insoluble residue of mercurous salt (4 g ) and the f i l trate yields 2.5 g of mixed di- and trimercurated products on cooling. These too are f i l tered off and the f i l trate evaporated in vacuum. This results in the crystall ization of 2.5 g of mono-mercurated compound, the f i l trate f rom which gives, on treatment with petroleum ether, an oil (crystal l iz ing after working up with benzene) which, after precipitation with water f rom solution in glacial acetic acid, yields a further 1 g of crystals. The melting-point of P -CH 3 CO 2 HgC 6 H 4 SC 6 H 5 is 148°C (from ligroine).

P-Phenylmercaptophenylmercury chloride, m.p. 181°C, is obtained quantitatively by dissolving the acetate in methanol and precipitating it out with CaCl 2 .

Preparation of 0-chloromercuridiphenyl sulfone [.366]. Diphenyl sulfone (2.5 g ) is heated to 170 180° C with 3.7 g of mercur ic acetate and a few drops of acetic acid, until the mixture sets. Theresul t ingmass is bo i ledfor some minutes with concentrated aqueous NaCl. The weight of the precipitate is 4.2 g; m.p. 247-248°C ( from alcohol).

e) Mercuration of Aromatic Amines

Amines are mercurated even more readily than phenols. In the simpler cases the reaction is carried out in the cold, in aqueous or aqueous-alcoholic solutions; the usual mereurating agent is mercuric acetate. This method was used to mercurate aniline [9, 71, 169, 370-374] (the rate is decreased by additions of HNO3

and HCIO4 [207]), mono- and dialkylanilines (methyl [71, 147, 374-376] and ethyl [374, 376, 377]), benzylaniline [376, 378] (at 50°C) and diphenylamine [9, 379, 380] (by fusion of diphenylamine with HgCl2 and subsequent boiling for an hour in acetic acid, the authors obtained 2,2',4,4'-tetrachloromercuridiphenylamine [380]). The method used for aniline (reaction with mercuric acetate) was also

MERCURATION 95

applied to the halogenoanilines (seebelow), p-bromodimethylaniline [381], p- [190, 301, 382-386], o- [301, 370, 385-390] and m- [301, 385, 387] toluidines, N,N'-dimethyl-p-toluidine [382, 383] andN,N-di-p-tolylformamidine (boiling with alcoholic mercuric acetate); the probable structure of the product is

Other compounds that have been mercurated in this way are 2- and 4-aminobiphenyls [392], benzidine [393, 394] (in glacial acetic acid solution), tolidine [394], a-naphthylamine (this gave only the 2,4-diacetoxymercuri-l-naphthylamine [228, 374, 301]), /3-naphthyl-amine (the product was l-acetoxymercuri-2-naphthylamine [228,

[395]), /3 , /3 -dinaphthylamine (the product was bis-l-acetoxymer-curinaphthyl-2-amine on heating with mercuric acetate in acetic acid [186]), 2-aminofluorene (in position 3) [396], and w-amino-phenyltrimethylammonium acetate (the dimercurated derivative [371]). However, arylammonium salts not containing other sub-stituents in the ring are very difficult to mercurate. Thus phenyl-trimethylammonium acetate mercurates neither after 2 months in the cold, nor after boiling for 24 hours with aqueous mercuric acetate [397]. In contrast, phenyltrimethylammonium nitrate heated to 950C with a solution of mercuric oxide in dil. HNO3 gives, after only 20 hours, the ^-substituted product (isolated after replacement of the HgX by bromine [167, 192a]).

Other rnercurating agents can also be used to mercurate the aromatic amines under such mild conditions, such as mercuric lactate [398] (aniline, naphthylamine) and the mercury salt of trinitromethane [147] (aniline, dimethyl aniline).

Mercury enters the amine molecule in accordance with the gen-eral laws of substitution in amines. Thus, aniline itself gives a mixture of 0- and p-monomercurated products [71, 370] and, when the mercuric acetate is in excess, the 2,4-dimercurated product [371]; mercuric sulfate gives the trimercurated derivative [267].

The conditions used for the mercuration of amines have also been extended to mercurate into the aromatic nucleus carrying the amino nitrogen, various derivatives of 2-arylaminothiazoles (4-styryl-2-arylaminothiazoles [399], 2-arylamino-4-methylthiazoles [400, 401], 2-arylamino-4,5-dimethylthiazoles [401-403], 2-arylamino-

Hg I

CH3

301]), phenyl-/3-naphthylamine (the product was



4-methyl-5-ethylthiazoles [404], 2-arylamino-4-phenylthiazoles [401, 405, 406], 2-arylamino-4-bromophenylthiazoles [406], 2-aryl-amino-4-bromophenyl-5-bromothiazoles [406], 2-arylamino-4-tri-azolidone and its derivatives [407-409], 2-arylamino-4-methyl-5-carbethoxythiazoles [410], 2-arylamino-4-(2-thienyl)thiazoles [411] and 2-phenylamino-4,5,6,7-tetrahydrobenzothiazole [412]); mercurations into position 3 of the aromatic ring carrying the nitrogen have also been reported for 3-N-arylthiazolines (2-arylamino-3-phenyl-, 4,5-aryl- and -alkylthiazolines [413], 3 - o -[414], m- [415] and p- [416, 417] tolyl-2,4-thiazolindiones, 3 - o -tolyl-5-benzyliden-2,4-thiazolindiones [417], alkylated, arylated, and 4,5-substituted 2-(j»-tolylimino)-3-(p-tolyl)thiazolines [418], 3-aryl-2-aryliminothiazolid-4-ones [419] [both aromatic nuclei were mercurated], 3-phenylthiazolidin-2,4-dione [420] and 2 - ( p -fluorophenylamino-4-thiazolidone) [421]).

Arylureas [422] and arylthioureas [422,423] are also mercurated under the same conditions as the amines.

As a rule, acetylation of the amino group makes the mercuration more difficult. Thus, acetanilide [424, 425] and acetotoluidides [391, 393, 426] cannot be mercurated below IOO0C.

The second-order rate constant of the mercuration of acetanilide is 0.191 x IO5 liters/mol. sec [269] in glacial acetic acid at 25°C.

p-Acetaminophenylmercury acetate is obtained by boiling ace-tanilide in aqueous solution with mercuric acetate [424], Fusion of acetanilide at 115-140°C with an excess of mercuric acetate yields t r i - [427], tetra- [428] and pentamercurated [429-431] compounds. Under these conditions acetyl- a-naphthylamine gives a tetra-mercurated compound [429, 430, 432] at a temperature not higher than 150°C. The introduction of mercury into aminohydroxy com-pounds is, however, possible only if the amino group is acylated (or methylated); if the amino group is f ree, the compounds merely reduce the mercuric salts. Mono- and dimercurated derivatives of N-methylated and o-acetylated aminophenols [265], N-acetylated aminocresols [433] and aminoalkylphenols [434, 435] have been prepared by prolonged heating, or even in the cold, in aqueous-alcoholic or aqueous-acetic solutions with mercuric acetate. On being boiled with alcoholic mercuric acetate, wi-hydroxyphenyl-trimethylammonium acetate gives directly the symmetric R2Hg [265], Fusion of p-acetoanisidine (125°C, [436]) and of />-aceto-phenetidine (140°C [437]) with an excess of mercuric acetate gives the tr i- and tetramercurated products respectively. Brief boiling of an excess of p-anisidine with mercuric acetate yields

OCH; HgOCOCH3

NH:

MERCURATION 97

The presence of amino groups in the ring of the nitro derivatives of hydrocarbons, ketones, carboxylic acids, sulfonic acids, and arsonic acids facilitates the corresponding mercurations, allowing the latter to be conducted under milder conditions, often similar to the conditions usedfor the mercuration of the amines themselves.

Themercurationsof o-, m- and jo-nitranilines [301,438, 439] and of nitrotoluidines [440] are carried out by heating in alcoholic or aqueous-alcoholic solutions. The same way was used to mercurate 3-nitro-l-naphthylamines [441-443]. Other nitronaphthylamines are mercurated on boiling in acetic acid solutions. The mercuration of 6-nitro-l-naphthylamine has been described [263, 444]. For the mercuration of other mononitro-1- and -2-naphthylamines, see [442, 443].

P-Aminoacetophenone was mercurated after brief heating with mercuric acetate above IOO0C [9, 108]; the composition of the product is not shown. The mercuration of the corresponding semi-carbazone is reported in [108]. p-Bromo-m-aminoacetophenone was mercurated after heating for 2 hours on a water bath in an aqueous-methanolic solution of mercuric acetate [109].

Mercury can be introduced into the nucleus of anthranilic acid at IOO0C [445].

Brief moderate heating with alcoholic-acetic or aqueous-acetic solutions of mercuric acetate led to the mercurations of anthranilic [445] and p-aminobenzoic [304, 446] esters, and of the esters of mono- [304, 445] and di-N-alkyl- [445] anthranilic acids. The pro-ducts were mono- or dimercurated, depending on the relative pro-portions of the reagents. N-Hg compounds form, in the absence of acetic acid, in purely alcoholic solutions, which transform into the C-Hg compounds when acetic acid is added. Ethyl y-aminobenzoate has also been mercurated after several hours of standing with an acetic-acid solution of mercuric acetate and after heating to 130-160°C without a solvent [446]. The esters of the anilido fatty acids have been mercurated by the action of aqueous-alcoholic mercuric acetate in the cold [304, 447]. Thus, the ethyl ester of phenylglycine gave an 82% yield of the monomercurated product and ethyl a-anili~ dipropionate both the mono- and the dimercurated derivatives; on reaction with equimolar quantities of the reagents, the higher homologs (ethyl esters of a-anilidobutyric and isovaleric acids) give dimercurated products [447]. In these compounds, and in other derivatives of aminobenzoic acids, the mercury substitutes the ring hydrogen ortho to the amino group [304, 445-447] (cf. [448]),

According to [448], when p-aminobenzoic acid is mercurated by boiling in aqueous solution, the mercury enters into the position ortho to the carboxyl and not into the meta-position as is believed by Schoeller et al. [446] for ethyl p-aminobenzoate (the mercura-tion was carried out with mercuric acetate in a mixture of alcohol and acetic acid); however the position of the mercury had not been determined in either case.



Methyl acetylanthr anil ate has been mercurated on fusion with mercuric acetate at 120-130°C [445], giving the monomercurated compound, m-Acylaminobenzoic acids (RCO- = acetyl and benzoyl) are mercurated in position 6 in the absence of solvent with mer-curic oxide or acetate, or by heating their mercury salts to 150-175°C [449].

Metanilic [450], p-aminohydroxybenzenesulfonic [450], /3-naph-thylamino-6-sulfonic and a-naphthylamino-4-sulfonic [228] acids are mercurated on brief boiling with mercuric salts in aqueous solutions.

p-Aminobenzenesulf amide and mercuric acetate in dilute aqueous-acetic solution form a monomercurated derivative in the cold [451] and a mixture of mono- and dimercurated compounds on heating on a water-bath [452], Thelattermixtureisalsoobtained when aqueous or alcoholic p-aminobenzenesulfamide is boiled with a solution of HgO in acetic acid (or in several other organic acids [453], More prolonged heating is necessary for the formation of the dimercura-ted compounds.

3,5-Diacetylamino-4-hydroxyphenylarsonic and 3-acetylamino-4-hydroxyphenylarsonic acids are mercurated in the form of their sodium salts in cold aqueous solutions (the latter also on heating [321]). In the second of these acids, the mercury enters position 5.

Further information regarding the mercuration of amino- and aminohydroxyarylarsonic acids will be found in [318, 320].

According to Maschmann [321], the compounds obtained by Raiziss et al. [318] do not contain C-Hg bonds because they give a very rapid reaction for mercury with ammonium sulfide.

The mercurations of amines pass through an intermediate stage in which the mercury salt adds to the amino group:

H H \ /

NH2 H3COCONHgOCOCH3 HNHgOCOCH3 NH2 I 1 1 1

Q + Hg (OCOCH3)2-. Q . Q * Q

I I I HgOCOCH3

The labile intermediates, I and I I , have been isolated in the mercurations of aniline and its homologs [455], p-aminobenzoic acid [448, 456], o- and p-aminobenzoic esters [445, 446], amino-and acetaminohydroxycarboxylic and arsonic acids [456] andmono-and polymercurated anilines [454].

P-Nitrodi methyl (and diethyl) anilines are not mercurated [397] because, according to Kharasch [397], their base strength is too low for the formation of intermediate ammonium-type adducts, whereas the more strongly basic o- and m-nitromonomethylaniline,

MERCURATION 99

p-nitromonoethylaniline and also p-nitraniline form products in which a ring hydrogen is replaced by HgO2CCH3. It is, however, more probable that the failure of mercuration in the first-mentioned case is due to steric hindrance.

The difficulties encountered in the mercuration of the basic triphenylmethane dyes (reduction of the mercuric salt to metallic mercury and oxidation of the dye) can be avoided if the mercuration is carried out not on the dye itself but on its colorless derivatives which cannot transform into the dye under the action of acids (in-cluding the acids liberated in the mercuration process), for example on its cyanide.

The dimercurated derivatives of Malachite Green have obtained by boiling 4,4 -bis-dimethylaminotriphenylacetonitrile or the car-binol of the leuco-base of this dye with mercuric acetate in ethyl acetate and subsequent conversion of the resulting colorless mer-curated derivatives by the action of ultraviolet light (in the case of the nitrile) or acid (in the case of the carbinol) to the mercurated dye [457, 458].

For other data regarding the mercuration of Malachite Green see also [332, 333, 459, 460].

Parafuchsin gives a trimercurated compound [333] on prolonged boiling with an equimolar amount of mercuric acetate in aqueous solution. The mercurations of fuchsin base and other triphenyl-methane dyes are described in [332].

Azoxybenzene has been mercurated [462] by heating with mer-curic acetate in glacial acetic acid to 135-140°C, with the formation of two (o - and p-) monomercurated products. Monohalogenated azoxybenzenes have been mercurated at 140-1600C [463]. The CH3COOHg group entered the ring carrying the halogen atom:

< ^ ) > - N : N (O) - < Q > + Hg (O2CCH3)2 —-

\ Br

- C H 3 C O a H g - < ^ > - N : N (O)

\ Br

N-Benzylacetamide is mercurated under mild conditions (in aqueous solution), forming two monomercurated o- and p -products [361].

Mercuration of anil ine [169, 370] , Freshly disti l led aniline (18.6 g ) is added to 31.8 g of mercur ic acetate dissolved in 160 ml of water. Short pa le-ye l low pr isms appear after brief standing, whose amount gradually increases, consisting of pure p-aminophenyl-mercury acetate. Easi ly distinguishable soft spherical aggregates of the o-compound, consisting of f ine crysta l l i tes , precipitate out when the solution is set aside f o r a longer t ime. The structure of this product is unclear. Full separation of the two compounds can usually be achieved by letting the crystal l izat ion proceed f o r approximately 3 hours, f i l t er ing off the pr ismatic crysta ls , decanting the mother liquor f r om the appearing


TOO ORGANOMERCURY COMPOUNDS

crystals of the £>-compound (contaminated with some p - i s o m e r ) and only then collecting the o-der ivat ive. The yields of the pure p-compound (m.p. 166-167°C) and pure o - c o m -pound (m.p. 158-160°C) are, respectively, 40 and 3 g.

Another method of separating the O- and p- i somers is based on different solubilities of the chlorides. When the main mass of the prismatic crystals of p-aminophenylmercury acetate is separated out, a solution of NaCl is added to the mother liquor containing the o-compound and still an appreciable amount of the p-compound. A mixture of amorphous insoluble p-chlor ide and crystall ine 0-chloride precipitates, which is easily separated by crystallization from hot alcohol, in which o-aminophenylmercury chloride is readily soluble. The melting-point of p-chloromercurianil ine is 188°C.

Preparation of 2,4-diacetoxymercurianiline [372] . NaHCO3 (251 g, 2.99 moles) is st irred in, at room temperature, into 479 g (7.99 moles ) of glacial acetic acid. At the end of the ef fervescence, 3.2 l i ters of water are carefully added, avoiding the formation of foam. The pH of the resulting solution is 4.30. Mercur ic acetate (318.6 g, 1 mole ) is then added, as a result of which the pH falls to 4.25. Finally, 93 g (1 mole ) of aniline is added, with continuous stirring, and the mixture set aside in the dark f o r 48 hours for complete precipitation of the product. The precipitate is washed with several portions of hot water and dried in vacuum over caustic soda. The yield of the pure product is 285.3 g (93.5%); m.p. 209°C.

When the above pH values are not strictly adhered to, the yield is reduced and, at pH > 4.25, the substance becomes contaminated with p-acetoxymercurianiline; the latter can be removed by washing with chloroform. At pH < 4.25 the product contains soluble 2,4-diacetoxymercurianilinium acetate (see also [371]).

Preparation of p-dimethy laminopheny lmercury acetate [375] . Solutions of 60 g of mercuric acetate in 400 ml of 50% ethanol and of 50 g of dimethylaniline in 96% ethanol are poured together. The initially c lear mixture thickens after a few minutes into a mash of fine needles; m.p. 165°C (from ethanol).

Preparation of 2-amino-5-chlorophenylmercury acetate [387] . An alcoholic solution of 13 g of P-chloroaniline is added to 32 g of mercuric acetate in a mixture of 100 ml of water and 200 ml of alcohol in the presence of a little acetic acid. After 10 hours the solid material is f i l tered off and recrystal l ized from ethanol; m.p. 207°C (see also [301]).

Analogous conditions have been used to mercurate m- [301, 464, 465] and 0- [301, 466] chloroanilines, 2,2-dichloroaniline [467], V- [468], m- [469, 470] and 0- [388, 468] bromoanilines and V-[461], m- [465, 470] and 0- [461] iodoanilines.

If it is desired to introduce only one atom of mercury into m-halogenoanilines, which are particularly prone to form di- and trimercurated compounds, the halogenoaniline must be taken in excess.

Preparation of p-acetoxymercuri-m-nitraniline [438] , Solutions of 9.6 g of mercuric acetate in 40 ml of water and of 4.2 g of m-nitraniline in 60 ml of ethanol are combined and heated for 3 hours on a water bath. The solution is f i l tered hot and the precipitate again extracted with ethanol acidified with acetic acid. A dark red material (m.p. 225°C) remains, which proves to be o,p-diacetoxymercuri-m -nitraniline. The alcoholic extract is evaporated and the residue recrystal l ized from a mixture of alcohol and acetic acid, yielding yellow needles of p-acetoxymercur i -m -nitraniline (m.p. 183°C).

Preparation of 2,4-diacetoxymercuri-l-naphthylamine [228] , T o a solution of 4.2 g of a-naphthylamine in 20 ml of alcohol and 20 ml of glacial acetic acid is added 50 ml of boiling water. The resulting solution is combined with a hot solution of 10 g of mercuric acetate in 50 ml of water. A bright yellow precipitate appears f i rst , which immediately changes into white crystals. The latter are then f i l tered off; yield: 9.5 g. The crystals are dried in vacuum over H2SO4 .

MERCURATION 101

Preparation of 2-acetoxymercuri-3-nitro-l-naphthylamine [ 4 4 l ] . 3 -N i t ro - l -naphthy l -amine (7.6 g ) in 100 ml of alcohol is worked up with a solution of 12.8 g of mercur i c acetate in 50 ml of water acidi f ied with 2 ml of acetic acid and the mixture boiled f o r 1 hour. Cooling and dilution with water g ives 14 g of brown microscop ic needles of 2-acetoxy-mercur i -3-n i t ro - l -naphthy lamine ; m . p . about 200°C.

Preparation of 2,4-bis-acetoxymercuri-3-nitro-l-naphthylamine By boil ing f o r 3 hours a mixture of 3.8 g of 3-nitronaphthylamine, 60 ml of alcohol, 13.2 g of mercur i c acetate, 50 ml of water and 2 ml of acetic acid, 12.5 g of the product are obtained.

Preparation of 4-acetoxymercuri-6-nitro-l-naphthylamine [444 ] . A boil ing solution of

5 g of 6-ni tro- l -naphthylamine in 30 ml of acetic acid is added to 8.6 g of mercur i c acetate in 15 ml of acetic acid and the mixture boiled f o r 5 minutes. The melt ing-point of the resulting mater ia l is above 400°C.

Preparation of p-ace tam inopheny lmercury acetate [423 ] . An aqueous solution of 32 g

of mercur ic acetate is added in smal l portions to a boil ing solution of 13.5 g of acetanilide in 300 ml of water and the mixture kept boil ing until a withdrawn sample g ives a white precipitate with caustic soda. On cooling, the requiredproduct crysta l l i zes out in the f o rm of co lor less plates. These are r ec rys ta l l i z ed f rom ethanol; m.p. 218-220°C.

Preparation of 3-aeetoxymercuribenzidine [395 ] . A 1 - l i t e r vesse l f i t ted with a mecha-

nical s t i r r e r is charged with a solution of 31.8 g (0.1 mo l e ) of mercur i c acetate in 150 ml of glacial acetic acid, the s t i r r e r is switched on and a solution of 18.4 g (0.1 mo le ) of benzidine in 300 ml of g lacial acetic acid slowly added. Immediate precipitat ion takes place. The mixture is s t i r red f o r about 10 minutes at the end of this addition. The p re -cipitate is f i l t e red off, washed f i r s t with glacial acetic acid and then with ether, and f inal ly dried in air , in the dark. Y ie ld : 55 g ;m.p . 144-146° C (with decomposition). The substance is insoluble in water , alcohol, ether and benzene.

The same method was used to obtain [395] acetoxymercuri-0 -tolidine, m.p. 120°C (with decomposition).

Preparation of the ethyl ester of 2-acetoxymercuri phenyl g lyc ine [447 ] . A solution of

20 g of mercur i c acetate in 50 ml of water is s t i r red into a solution of 17.8 g (1 mo le ) of the ethyl es ter of phenylglycine in 50 ml of methanol. Turbidity appears, fo l lowed by the separation of a yel lowish oi l which red isso lves on further st irr ing (a small quantity of methanol can be added if necessary ) . A f t e r 10-15 minutes the mercur i c ion can no longer be detected in the mixture. Strong cooling (cooling mixture ) and scratching with a g lass rod results in the precipitation of a dense ye l lowish-white solid, whose amount increases on further standing. A f t e r 24 hours in the cooling mixture the precipitation is pract ical ly complete. The mater ia l is f i l t e red of f , washed f r e e f r om the l iberated acet ic acid with cold water and dr ied in vacuum ove r sulfuric acid. Y ie ld : 20 g (82%). On further standing, the mother l iquor y ie lds another small portion of the product, but of a lower degree of purity. A f t e r twofold crystal l izat ion f rom chloro form, careful removal of the solvent and drying at 60°C, the melt ing-point is 132°C (initial softening at 128°C).

An aqueous solution of 0.26 g of NaCl is added to 2 g of the acetate in 30 ml of alcohol and the mixture diluted with a large volume of water. The resulting chloride is c rys ta l -l ized f rom methanol; m.p. 152.5°C.

Mercuration of 2-arylamino-4-methyl-5-carbethoxythiazoles [410 ] ,

H g O C O C H 3



A mole of 2-arylamino-4-methyi-5-carbethoxythiazole in a mixture of alcohol and dilute acetic acid is treated with an aqueous solution of 1.3 moies of mercuric acetate acidified with acetic acid. A precipitate appears after some time. The reaction mixture is set aside overnight. The precipitate is f i l tered off and purified by repeated washing with hot water, alcohol and very dilute acetic acid.

Preparation of the internal salt of p-hydroxymercurianthranilic acid [445],

A strong current of steam is passed through a suspension of 10 g of anthranilic acid and 16 g of HgO in 100 ml of water. The reaction mass becomes colorless after 2-3 hours. The reaction is regarded as complete when a withdrawn sample dissolves in alkali. For its purification, the anhydride is dissolved in 1.25 moles of IN alkali, f i l tered if necessary, and precipitated with 1.25 moles of IN H2SO4. The yellow amorphous precipitate is f i l tered off, washed with water to remove all traces of sulfate and dried. Yield: 23.5 g (96%).

Preparation of methyl 3-acetoxymercuri-2-aminobenzoate [445]. Methyl anthranilate (9 g ) is added to a warm solution of 22.5 g of mercuric acetate (1 mole ) in 100 ml of methanol and 10 ml of glacial acetic acid. The mixture is heated to 50°C for 15 minutes and set aside overnight in an ice bath. On the following day the precipitate is f i l tered off and washed with a little methanol and ether. Yield: 22 g (90%). The residue from the mother liquor is obtained by diluting the latter with 3 volumes of water; the resulting yellow needles are recrystal l ized from water or alcohol. The substance melts with decomposi-tion at 180-182°C.

Preparation of ethyl m-acetoxymercuri-p-aminobenzoate [446], A mixture of 3 g of ethyl p-aminobenzoate and 6.3 g of mercui ic acetate is heated on a glycerol bath. Lique-faction occurs at 130°C and acetic acid is evolved. The melt solidifies at 160°C. After cooling, grinding down to a powder, and extraction with methanol, the alcoholic solution is evaporated down and diluted with hot water. Lustrous needles (2.3 g ) crystal l ize out on cooling.

The same reaction requires 24 hours when it is carried out in acetic acid, but the above quantities of the starting materials give a higher yield of the product (3.3 g). Both methods give a small amount of the dimercurated derivative, which remain as an insoluble residue after the extraction with methanol. Ethyl m-acetoxymercuri-p-aminobenzoate melts at 182°C, then solidif ies and melts again at 228°C.

Preparation of W-acetoxvmercurisulfanilamide [451], A solution of 17 g of sulfanil-amide in dil. HCl is treated with a solution of 40 g of mercuric acetate in 400 ml of water acidified with acetic acid. Immediate precipitation takes place. The mixture is well stirred and set aside overnight. The precipitate is f i l tered off and washed carefully, f i rst with hot water and then with very dilute acetic acid; m.p. > 350°C; yield: 85%.

According to [453], the melting-point of monoacetoxymercurisulfanilamide recrystal-l ized from dilute acetic acid is 245cC.

Preparation of 3-acetylamino-4-hydroxymercuriphenylarsonic acid [32 l ] .

NH2

Hg+

NHCOCHs

HgOH

MERCURATION 103

A suspension of 2.75 g of 3-acetylamino-4-hydroxyphenylarsonic acid in 30 ml of i ce-cold water is rapidly dissolved by adding 11 ml of 2N NaOH and treatment with an i ce -co ld solution of 2.2 g of mercur i c acetate in 20 ml of acetic acid and 20 ml of water. A f t e r the solution h a s b e e n s e t a s i d e i n t h e d a r k f o r 6-7 days, the ye l low-brown precipitate is washed with water and dried. The unreacted arsonic acid is removed by shaking with methanol. The yie ld is pract ica l ly quantitative. The substance does not change on heating to 300°C. A co lor l ess product is obtained by dissolving it in cold dil . NaOH, shaking with animal charcoal and precipitat ion with dil. HCl.

When the react ion is car r i ed out with heating on a water bath, the process is completed within 1 hour. The product is co lored.

Preparation of dimercurated 4,4-bis-dimethy iaminotriphenylacetonitrile [457 ] .

A solution of 7.1 g (0.02 mo l e ) of 4,4 '-dimethylaminotr iphenylacetonitr i le in 150 ml of ethyl acetate is treated with 3 ml of acetic acid and 12.8 g (0.04 mo l e ) of solid m e r -curic acetate. The mixture is gently ref luxed f o r 70 minutes until the mercur i c acetate d isso lves . A l itt le precipitation of mercurous acetate takes place. The react ion mixture is cooled to room temperature, the solid mater ia l f i l t e red off (1.56 g, mainly mercurous acetate) and the f i l t ra te was evaporated down to 30 ml under vacuum. Some more prec i -pitate appears and is again f i l t e red off (0.81 g) . The f i l t rate is diluted with 130 ml of methanol and at once treated with 30 ml of 4N KOH. The resulting pale cream precipitate which appears rapidly is set aside f o r 4 hours, then f i l t e red off and dr ied in a desiccator . The yie ld of this impure mater ia l is 8.55 g. F o r further purif ication, 4 g of the products are dissolved in 100 ml of methanol containing 1 ml of acetic acid, the solution f i l t e red and the f i l t rate treated with 16 ml of methanolic 2N KOH. A f t e r 24 hours, the precipitate is separated off, washed on the f i l t e r with small portions of methanol and water and dried in a desiccator . The substance darkens and decomposes on heating above 200°C.

Photochemical conversion of mercurated bis-dimethylaminotriphenylacetonitrile into mercurated Malachite Green. Methoxymercur ihydroxymercur i -b is -d imethy laminotr i -phenylacetonitr i le (2 g ) is d issolved in 100 ml of methanol containing 1% of acetic acid. The solution is placed in a quartz vesse l , cooled with running water to avoic boil ing of the alcohol and the contents illuminated by a quartz lamp. The initially co lo r l e ;s solution rapidly assumes a blue co lor which deepens on further illumination. On treatment with alkali, the mixture g ives a white precipitate consisting of a mixture of the starting nitr i le and hydroxymercuricyanomercuri-bis-dimethylaminotr iphenylcarbinol :

N(CH3 )2

HgOCOCH3

N(CH3 )2

H g O H

HgCN



f ) Mercuration of Aromatic Ketones

The aromatic ketones are mercurated under relatively vigorous conditions: on heating with mercuric acetate without a solvent to a temperature of at least 150 0C1 or on prolonged heating with mer-curic acetate in acetic acid.

Few purely aromatic ketones containing no functional groups other than the carbonyl have been mercurated. Benzophenone fused with mercuric acetate [71, .167, 471] or heated with the same salt in acetic acid for 6 hours at 980C [472] gives mainly the o-mercurated product. According to [71] and [471], a small quantity of a polymercurated compound is also formed. Ogata and Tsuchida [167, 192a] found that the mercurated product contains, apart from the o-isomer, in the f irst case 5% and in the second 15% of the m-isomer (the products were analysed by replacing the HgC02CH3 group with Br). Fluorenone [167, 192a] gives only the 1-mercurated product (identified in the form of 1-bromofluorenone)

both after boiling for 2% hours with mercuric acetate without a solvent or after 10 hours with the same salt in acetic acid.

A very small yield of symmetric 9-dihydrodianthraquinonyl-mercury [473] is obtained after a mixture of anthrone and mer-curic acetate is boiled for 6 hours. 9-Dihydroanthronylmercury sulfate is formed, also in a very small amount, when anthrone is heated for 2 hours at 50-70°C with mercuric sulfate in sulfuric acid monohydrate.

On fusion with an equimolar amount of mercuric acetate, ben-zanthrone gives the compound [472]

Xanthone and its nitro and amino derivatives have been mercur-ated under rather milder conditions [474] by boiling with mercuric oxide in alcoholic or acetic acid solution.

The mercuration of anthraquinone has been achieved by the action of a solution of HgO in polyphosphoric acid for several hours at 140-145°C [475] (cf. [167]), and by interaction with mercuric oxide or basic sulfate in dimethyl sulfate at 150°C (in the latter cases

O

HgOCOCH3

MERCURATION 105

the products were 1-monomercurated anthraquinone and a- and /3-anthraquinonesulfonic acids) [475].

During the mercuration of 1-anthraquinonesulfonic acid, an Hg atom first enters into the a-position of the unsulfonated ring and a second Hg atom is then substituted into the same ring, in the position para to the f irst [475]. The reaction is carried out with HgO in orthophosphoric acid (1 hour at 120-125 °C).

According to Dimroth [167, 168], acenaphthenequinone is not mercurated.

P-Acetophenylarsonic and p-acetophenylantimonic acids have been mercurated [108] in the aromatic ring by HgO in the absence of heat. The structures of the products were not given.

The iaercuration of acetophenone and its derivatives into the methyl group, and of indandione has already been mentioned, as also has that of aminoaryl alkyl ketones.

Preparation of Ochloromercuribenzophenone [ 7 1 ] . Dry mercur i c acetate is heated with 3 moles of benzophenone at 150°C until a reaction f o r mercur i c ion is negative. The warm mixture is poured into aqueous NaCl, cooled and shaken up with ether. Evaporation of the ether g ives unreacted benzophenone, the monomercurated product, and an admix-ture of the dimercurated der ivat ive. Benzophenone is washed out of this mixture with hot l igroine and the residue rec rys ta l l i z ed f rom alcohol; m.p. of o - ch lo romercur ibenzo -phenone, 167-168°C; yield: 40% on the mercur i c acetate (cf. [167]).

Preparation of 1 - ace toxymercuribenzan throne [472 ] , A f inely ground and st i r red equimolar mixture of mercur ic acetate and benzanthrone is heated in a wide tube on a paraf f in bath f o r 30 minutes at 171°C. The ye l lowish-brown mass obtained on cooling is heated to boiling in a mixture of alcohol and acetic acid and f i l t e red hot. The yel low substance which separates out on cooling is f i l t e red off and washed with alcohol (till the washings became co lo r l ess ) and then with ether. The mater ia l dried in vacuum over C a C l 2 melts with foaming at 141-142°C. Yie ld: about 60%.

g) Mercuration of the Aromatic Carboxylic, Sulfonic and Arsonic Acids and Their Derivatives

Mercury is difficult to introduce into aromatic rings containing m -directing groups such as -COOH or -SO3H. The aromatic car-boxylic acids are mercurated by fusion with mercuric acetate in the absence of solvent or by several hours of boiling with alkaline HgO or Hg(OOCCH3)2. Another widely used method of synthesis of mercurated carboxylic acids is heating of their mercury salts (the benzoate to 170°C [71]); a temperature of 130-1400C is suggested by Pesci [476],

Dimroth [71] and Pesci [477] believed that only the o-isomer is formed when mercuric benzoate is fused or when benzoic acid is heated with mercuric acetate, but this is opposed by infra-red spectroscopic studies [190] carried out on the bromobenzoic acids obtained by replacing HgX with Br in the products obtained by the mercuration of benzoic acid for 1Vi hours at 130 °C, which showed that all three isomers are in fact present, the o:m:p ratios being



57:25:18. There is no anomalous orientation (mercuration ortho to the carboxyl group) in this case, because the substitution occurs in the carboxylic acid salt, and the carboxylate group is o -p -directing, in contrast to the f ree -COOH.

According to Ogata and Tsuchida [192, 192a], 10 hours of boiling of mercuric acetate in acetic acid with an excess of benzoic acid results in the formation of a 4:1 mixture of w- and o-mercurated products (identified by replacing HgOAc by Br).

It is not impossible that an HgX group may migrate from one position in a benzene ring to another on prolonged boiling (see introduction to this chapter).

Benzoic acid has also been o -mercurated by mercuric sulfate [289]; the conditions were not reported.

The above methods have been used to mercurate o-toluic acid [478], alkyl- and alkoxy- [479] and halogeno- [478-480] carboxylic acids; for example, the internal anhydride of hydroxymercuri-o -chlorobenzoic acid has been made by heating mercury o-chloro-benzoate to 140-1450C [480]. p-Fluorobenzoic acid has been prepared by heating for 12 hours in glacial acetic acid [178], Nitrobenzoic acids are mercurated by fusion with HgO, by fusion of their salts, e.g. the ammonium salts, with mercuric acetate, or by heating their mercury salts to 200-2500C [316, 481, 482]. In the last-mentioned method, COO is replaced by Hg in the o-isomer [632], Of the carboxylic esters, methyl benzoate has been mercurated by 4-5 hours of boiling with mercuric acetate in the presence of a little acetic acid [168, 297]. Themercuryentered the o- and (according to [167, 192a]) the w-position.

In 1-naphthoic acid boiled with an alkaline solution of mercuric acetate for 44 hours, the mercury enters into positions 5 and 8 [483].

For the reaction between sodium phthalate and mercuric acetate, giving hydroxymercuribenzoic anhydride, see Chapter 9.

Boiling sodium tetraphthalate in aqueous solution with mercuric acetate for 240 hours, or fusion of diethyl terephthalate with the same mercury salt, are necessary for the introduction of mercury into the terephthalic nucleus [484].

Ring mercuration occurs when mercuribenzamide or mercuri-phthalimide are heated [77]. Only o-mercuration takes place when benzamideis boiledfor 6 hours with mercuric acetate in acetic acid solution or in the absence of any solvent (the product was identified as the o-bromobenzamide) [167, 192a].

Mercuric acetate gives rise to exclusive p-mercuration in phenyl-acetic acid (12 hours at 98°C in acetic acid solution) and in methyl phenylacetate (7 hours of boiling). The products of these reactions were identified in the form of p-bromobenzoic acid, obtained in the former case by replacement of the HgOCOCH3 group with Br and oxidation of the CH2COOH group, and in the latter case, after re-placement of HgOCOCH3 with Br, by hydrolysis and oxidation [167, 192a]. The product of the mercuration of benzonitrile with mercuric

MERCURATION 107

acetate (7 hours of boiling in glacial acetic acid) was the mercu-rated N-benzoyl-N-phenylurea, p -CH3COOHgCfiH4NHCONHCOCRH. [485].

Fusion of equal amounts of mercuric acetate andbenzenesulfonic acid to 1050C for 2 hours [190] gives a mixture of o-, m- and p-monomercurated products (24:61:15), as has been found from the infra-red spectra of the bromo-derivatives obtained by replacing the HgX groups in the mixed mercurated products with Br.

When p-toluenesulfonic acid is boiled for an hour with mercuric acetate in aqueous solution, or when its sodium salt is correspon-dingly boiled for several hours, the mercury enters into the position ortho to the methyl group [486],

Benzenesulfonic and halogenonitrobenzenesulfonic acids give under these conditions a mixture of amorphous unidentifiable sub-stances [486],

When mercuric perchlorate containing perchloric acid is reacted with the ion-exchanger Dowex 50 W-X8 (a sulfonated polystyrene) at 25, 60 and 80-85°C, the usual exchange of Hg2+ with H+ is ac-companied by irreversible absorption of mercuric ions; this may be due to nuclear mercuration [487]:

- C H - C H 2 - -CH-CH 2 -

SO3H+ SO3-

In the mercuration of 4-carboxyphenylarsonic acid [318] (under the conditions used for the mercuration of benzoic acid), the mer-cury enters into position meta to the carboxyl.

The mercurations of hydroxycarboxylic, hydroxy sulfonic, hy-droxyarsonic, aminocarboxylic, aminosulfonic, aminoarsonic p-acetobenzoic acid (in the methyl group), anthraquinonesulfonic, P-acetophenylarsonic and antimonic acids have already been mentioned in this chapter; the acids of the heterocyclic series are mentioned below.

Mercuration of benzoic acid [476 ] , Mercur i c acetate (32 g ) is fused with 20 g of benzoic acid by heating to 130-140°C (Dimroth [71] recommends temperatures of up to 170°C) until the NaOH reaction f o r mercur ic ion becomes negative. The me l t is cooled, ground up and heated f o r about 2 hours with 70 g of soda crystals . A f t e r cooling, the mixture is again f i l tered, a current of CO 2 is passed through the solution and the resulting precipitate treated with ammonium carbonate until full dissolution takes place. T h e ammonium salt of mercur ibenzo ic acid separates out f rom the pale ye l low solution; on treatment with acetic acid it f o rms the internal salt in the f o rm of an amorphous white powder. This salt can be obtained in crystal l ine f o rm by converting it f i r s t into the sodi-um salt and passing CO 2 through its solution. The product is predominantly the internal salt of o -hydroxymercur ibenzo ic acid [477], According to Ogata et al., this method of mercurat ion results also in the m - and p - i s o m e r s (see above).



Preparation of methyl o-chloromercuribenzoate [2Q7], Finely ground mercuric acetate (20 g ) is dissolved in 20 g of methyl benzoate and 3 g of glacial acetic acid by heating in a round-bottom flask. The mixture is gently refluxed for 3-4 hours to the disappearance of mercuric ions. On cooling, the solution is f i l tered from a small amount of mercurous acetate and metall ic mercury and the excess of acetic acid and methyl benzoate evapora-ted off f rom the f i l trate under vacuum. The residue consists of 19 g of a yellowish (after cooling) viscous oil. About 200 ml of acetone are then added. The amorphous product (5.6 g) is the methyl ester of diacetoxymercuribenzoic acid, which is insoluble in the usual sol-vents with the exception of acetic acid.

A monomercurated derivative is present in the acetone fi ltrate, which after evaporation of the solvent remains in the form of a pale-yellow non-crystalline mass. Yield: 13.3 g.

Conversion of this acetate into the chloride is accomplished by precipitating it from an aqueous-alcoholic solution with aqueous NaCl. The resulting 9.1 g of methyl o-chloro-mercuribenzoic acid are purified by dissolution in ethyl acetate and precipitation with petroleum ether; m.p. 162 C (with preliminary changes from 142°C). According to [448], the melting-point is 184.5°C (from dilute alcohol or ethyl acetate).

Mercuration of 1-naphthoic acid [483], Preparation of a mixture of 5-hydroxymercuri-1-naphthoic acid and 8-hydroxymercuri-l-naphthoic anhydride. A solution of 172 g (1 mole ) of 1-naphthoic acid in 210 ml of 5N NaOH and 2 l i ters of water is placed in a flask fitted with a dropping funnel, a s t i r rer with a mercury seal and a reflux condenser connec-ted to a trap containing a weighed amount of KOH to absorb the liberated CO2. The mixture is heated to boiling, with constant stirring, and a solution of 318 g (1 mole ) of mercuric acetate in 1.5 liters of water and 60 ml of acetic acid gradually added. A white grainy precipitate appears at once and gas is slowly evolved. The mixture is heated f o r 44 hours under a continuous current of C 0 2 - f r e e air. The amount of carbon dioxide absorbed by the KOH is equal to 4.98 g. The cream substance in the flask is treated with 280 ml of 5N NaOH; part of it dissolves and the remainder becomes dark owing to the presence of mercurous compounds. The weight of this insoluble residue is 80 g. The alkaline f i l trate is saturated with CO2 and the resulting precipitate f i l tered off and then dissolved again in alkali and precipitated with carbon dioxide; the weight of the precipitate is 240 g. I-Naphthoic acid (34 g ) is recovered f rom the f i ltrate by acidification with hydrochloric acid. The material precipitated by carbon dioxide is a mixture of 5- and 8-mercurated products, with a predominance of the f o rmer (the compounds are identified in the form of chloronaphthoic acids, obtained by replacing the mercury group by Cl).

Mercuration of terephthalic acid [484]. Preparation of the internal anhydride of 2-hy-droxymercuriterephthallc acid. A solution of 34 g (0.2 mole ) of terephthalic acid in a small excess of aqueous NaOH is mixed with a solution of 44.7 g (0.2 mole ) of HgO in a small excess of acetic acid and 10 ml of sodium acetate and the whole mixture refluxed for 240 hours. Af ter this time the mixture gives no reaction f o r inorganic mercury and full dissolution in the NaOH takes place. The mixture is cooled and the precipitate f i l tered off and dried; yield: 102 g. Terephthalic acid (10 g ) is recovered on acidification of the f i ltrate. The mercurated product is stirred for an hour with 1 l iter of concentrated am-monia and 500 ml of water and the insoluble material f i l tered off and worked up in the same way once again. The two extracts are acidified with acetic acid. The resulting white pre-cipitate is f i l tered off, transferred into a larger beaker, dissolved in a very small amount of insoluble substance, cooled and treated withC02. A mixture of monomercurated acid and a little dimercurated product crystal l izes out and is st irred for about an hour with 500 ml of sodium acetate saturated at 20°C and 1 liter of water. The monomercurated compound dissolves and the mixture is f i l tered. The f i l trate is acidified with 40 ml of glacial acetic acid and f i l tered. The precipitate is washed with water and alcohol and finally dried in vacuum over phosphorous pentoxide. The yield of pure 2-hydroxymercuriterephthalic anhydride amounts to 18 g. Additional portions of this material can be obtained f rom all residues and f rom the mother liquor.

Mercuration of diethyl terephthalate [484] , A mixture of 40 g (0.18 mole ) of diethyl terephthalate, 57.5 g (0.18 mole ) of mercuric acetate and 2 ml of glacial acetic acid is heated for 70 hours at 117°C (the boiling temperature of n-butanol), until all inorganic mercury is consumed. The viscous mass is steam-distil led for 24 hours, the residue worked up with aqueous ammonia, f i l tered and acidified. The mercurated terephthalic ester is purified as described in the previous preparation.

MERCURATION 109

Mercuration of p-toluenesu l fonic acid [486 ] , A 190-g (1.1 mo le ) portion of the acid is dissolved in 750 ml of water and 35 ml of acetic acid and the solution boi led and f i l tered. A s im i l a r solution of 320 g of mercur i c acetate is then prepared and the two solutions separately boiled and then combined and boi led f o r another hour. (A f t e r this t ime a withdrawn sample diluted with an equal volume of water should g ive a c l ear solu-tion with caustic soda.) The mixture is f i l t e red hot and the residue (81 g ) re jec ted . A f t e r being cooled the f i l t rate y ie lds 135 g of a crysta l l ine product, which is extracted with water in a Soxhlet extractor . The composit ion of the sol id a i r -dr i ed mater ia l c o r r e -sponds to the formula

CH 3 CH 3

SO 3 H-H 2 O SO-

ll) Mercuration of Heterocyclic Compounds

The ease of the replacement of hydrogen by mercury in hetero-cyclic compounds varies over a wide range. The superaromatic heterocycles such as furan, thiophene, selenophene and their de-rivatives having at least one free a-position are a-mercurated very readily by the action of HgCl2 and sodium acetate in the cold, in aqueous solution. This method has been used for furan [489], 2-iodofuran [489], sylvan [489, 490] and other 2-alkylfurans [491-493], /3-iodosylvan [489], furfuryl alcohol [490, 494, 495], 2-meth-oxyfuran [496, 497] and 2-methylmercaptofuran [497], 2-methyl-benzofuran [498], 4,5,6,7-tetrahydro-3,6-dimethyl- [499], 2-phenyl-[499, 500] and 2-ethyl- [500] benzofurans, 2,4-dialkyl- [498, 500], 2,3,4- and 2,3,5-trialkylfurans [498, 500], 2- a-acylalkylfurans [501], ethyl ester of pyromucic acid [494] (in alcoholic solution), methyl ester of 3-methyl-4-furancarboxylic acid [502] and furfural [503].

Furfural is also mercurated by boiling an aqueous solution of mercuric chloride [494]. The reaction with mercuric acetate in acetic acid at 140-150 0C [504] gave the a-monomercurated com-pound and another substance which had not been identified [503],

Several 2,5-dialkylfurans have been mercurated in the /3-position [500, 505] by the action of mercuric chloride and sodium acetate, but at room temperature these reactions proceed more slowly than a -mercurations [500] and are therefore as a rule carried out with heating [500, 505] or with prolonged standing.

The methyl ester of 5-bromo-2-furancarboxylic acid is mercura-ted in position 4 by fusion with mercuric acetate at 160°C [506].

2,5-Dimethylfuran smoothly yields the monomercurated product when it is reacted with ethanolic mercuric chloride at room tem-perature, in the presence of CH3COONa taken in a smaller than usual amount [500],

/3-Monomercurated furan not containing other substituents can be obtained only indirectly by heating mercuric acetate a-furoate



(see under "Substitution of mercury for the carboxyl group", Chapter 9). The action of an excess of mercuric acetate solution in the cold on furan and furfural diacetate gives, respectively, tetra-acetoxy-mercurifuran [507] and the trimercurated furfural diacetate de-rivative [508], obtained as the chloride:

Tetramercurated furan is obtained when aqueous solutions of equimolar proportions of 5-benzamidomethylfuran-2-carboxylic acid and HgCl2 [509] are boiled together for 1 hour (see also under "Substitution of . . . , " , Chapter 9).

Yields of 20-25% of a-monomercurated furan have also been obtained by means of an ethereal solution of the mercury salt of trinitromethane [147], Furan and sylvan are mercurated with mercuric cyanate in the presence of sodium acetate, by allowing the reagents to stand in the cold in aqueous-alcoholic solution [510]; the former compound gives a mixture of mono- and dimercurated products; the latter only the 5-monomercurated derivative [510].

Thiophene can be mercurated in the a-positionevenby the action of organomercury salts (see under "Synthesis of RHgR'with the aid of dihalogenocarbons", Chapter 12). The main product of the mer-curation with mercuric chloride in the presence of sodium acetate in cold aqueous solution, f irst used by Volhard [511], is a-chloro-mercurithiophene [511, 512]; this is accompanied by a small yield of the 2,5-dichloromercuri compound. Themercurationofthiophene with the same mixture but with boiling [513], or with mercuric acetate in the cold [514], gives the 2,5-disubstituted compound. According to Dimroth [149], during the separation of thiophene from benzene, cold mercuration with mercuric acetate (or mer-curic sulfate or nitrate, though the reaction is then slower) allows isolation of the heterocyclic in the form of dimercurated derivative to which Dimroth ascribed the structure

(cf. [514, 515]). The action of aqueous mercuric sulfate on thiophene, with shaking

in the cold, yields a trimercurated product [514] (see also [516]). The action of mercuric nitrate leads to analogous products but requires a longer time [149]. The action of mercuric cyanate in the presence of sodium acetate (cold aqueous-alcoholic solution) gives a mixture of mono- and dimercurated products [510].

ClHg HgCl

MERCURATION 111

More vigorous conditions must be used to mercurate thiophene in the /3-position. Tetra-acetoxymercurithiophene has been obtained by heating 4 moles of mercuric acetate with 1 mole of thiophene on a water bath (according to Paolini [517], this reaction proceeds in the cold) in acetic acid solution [518]. The same compound with a labeled sulfur atom has been obtained by the action of HgO in acetic acid on a-thiophenecarboxylic acid [519],

The action of mercuric chloride and mercuric acetate in the cold, in aqueous or aqueous-alcoholic solution, has been used to mer-curate many thiophene derivatives in the a-position; dimercurated compounds are easily formed if both the a-positions are unoccupied. For example, this method has been used in the case of 2-thiotolene [511, 512, 520-523], 3-thiotolene [511-513], 2-ethylthiophene [523-525], 3-ethylthiophene [521], 2-propylthiophene [523], 3-isopropyl-thiophene [511], 2-t-butylthiophene [525], 2-isoamylthiophene [523], 2-benzylthiophene [523], 2-phenylthiophene [512, 526], 3,4-thioxene [512, 527], 2,3-thioxene [523], 2,4-thioxene [523], 3-methyl-2-ethyl-thiophene [528], 2 -methyl - 3-ethylthiophene [528], 3,4-diethylthio-phene [529], 2,4-diphenylthiophene [530-532], 2,3-diphenylthiophene [533]; various monochloro- [534], monobromo- [512, 513,535-537], monoiodo- [512, 522, 538, 539], polychloro- [534],polybromo-[535, 536] and polyiodo- [522, 537, 538] substituted thiophenes and thio-phene homologs; 2-methoxythiophene [539], 2-methoxymethylthio-phene [540], 2-thienyl ethyl ether [524], 2-thienylmethylcarbinol [541], 2-thiophenecarbinol [542], 2-acetylaminothiophene [543] (the monosubstituted product; polymercurated ones by mercuric acetate [544]); 2,2'-dithienyl- [545], 2-terthienyl- [547], 5-methyl-[547] and 5-butyl- [546] -2,2'-dithienyls; 1-methyl-a-terthienyl [547], 2-thienyl methyl sulfide [254], 2-thienyl ethyl sulfide [524] and thiophene-2-carboxylic acid [201].

Isolated cases of the mercuration of thiophene derivatives by alcoholic HgCl2 in the absence of sodium acetate have been reported. See, for example, the mercuration of 2-acetylamino-4-bromothio-phene [544] and 2-acetylaminothiophene [544] (monosubstituted product).

The mercuration of polyvinylthiophene also occurs under ex-tremely mild conditions (cf. polystyrene mentioned in Chapter 5): a quantitative yield of a product containing an Hg atom in every unit of poly-a-vinylthiophene is obtained within 1-2 minutes when warm benzene solutions of the polymer and mercury di-isobutyrate are stirred together [173].

Certain thiophene derivatives with the two a-positions occupied can be mercurated by the action of mercuric chloride and sodium acetate, but a longer standing in aqueous-alcoholic or alcoholic solution, or boiling is now required (see, for example, the mer-curations of 2,5-diethylthiophene [548], 3-methyl-2,5-diethylthio-phene [548], 2-methoxy-5-methylthiophene [540], 5'-methyl- [525], 5'-ethyl- [549] and 2',3',1,2-cycloheptylthiophene, and 2-methyl-



and 2-propyl-4,5,6,7-tetrahydrobenzothiophene [550]). Contrary to [523], a, a'-diphenylthiophene is not mercurated either under the above conditions or on boiling with mercuric acetate in acetic acid [533].

a-Substituted thiophenes are best mercurated by mercuric acetate in alcoholic, acetic acid, or aqueous solutions, which favors the formation of polymercurated products, especially in the presence of electropositive substituents. Thus, for example, the reaction of 2,5-thioxene with mercuric acetate gives the di-mercurated derivative [513], and the corresponding reaction with HgCl2 and sodium acetate results in the monomercurated product [512].

Mercuric acetate has been used to mercurate the halogeno de-rivatives of thiophene [512, 534, 545] and also 2-methyl-5-ethyl-thiophene [551], 5,5'-dimethyl-4,4'-diethyl-2,2'-dithienyl [529] and nitrothiophenes [529, 552, 553].

Mercuric acetate in the cold has been used to mercurate 3-methylthionaphthene [554], 3-phenylthionaphthene [554], 5-methyl-3-phenylthionaphthene [554], 2-methyl-3-phenylthiophene [555, 556], 3-methyl-4-phenylthiophene [556], 2-methyl-4-ethylthiophene [557], 4-methyl-2-(l-hydroxycyclohexyl)thiophene [558], 1,4,4-trimethyl-4,5,6,7-tetrahydroisothianaphthene [559], thiophene-2-carboxylic acid [553], 2-acetylaminothiophene [544], o-(2-thienoyl)benzoic acid [560] and 2-alkylthiophenes [561]; on being heated on a water bath for an hour with mercuric acetate in 50% acetic acid, 2-ethyl-thiophene gave the monomercurated compound [561]. On being heated for 5 hours with mercuric acetate in aqueous acetic acid, 2,4-dichlorothiophene similarly gave the monomercurated com-pound [561a]. On the other hand, thionaphthene with mercuric acetate in cold alcoholic solution gives /3-thionaphthenylmercury acetate [562], and after heating, both with mercuric acetate and with mercuric chloride in the presence of sodium acetate, the product is the dimercurated compound [562]. According to other authors [563], however, heating of thionaphthene with mercuric acetate in alcoholic or acetic acid solution results in the mono-mercurated product. Thionaphthene can be separated from naph-thalene by mercuration carried out by boiling the starting material with methanolic mercuric acetate for 1 hour [564].

2,3-Diphenylthiophene forms a mixture of RHgOOCCH3 and R2Hg compounds [533] on being boiled for 3 hours with mercuric acetate in acetic acid.

The method of fusion with mercuric acetate is also used; for example, 5-benzothienone and iodo-substituted 5-benzothienones have been mercurated in this way [565], 5-Benzothienone boiled with HgCl2 and mercuric acetate in glacial acetic acid gives the 2-mercurated product, and on fusion with mercuric acetate a mixture of mono- and dimercurated compounds which can be con-verted into the dimercurated product by boiling with mercuric

MERCURATION 113

acetate in methylcellosolve [565]. The conditions used for the mercuration of thiophene (HgCl2/

sodium acetate) have also been applied to mercurate, in the a-position, selenophene [520, 566], 3-methylselenophene [567], 2,4-dimethylselenophene [567], 2,3,4-trimethylselenophene [568] and 2,4-diphenylselenophene [530, 531],

Melting-temperatures have been reported [520] for the mono-chloromercurated derivatives of selenophene, 2-methylselenophene and 2,5-dimethylselenophene, without giving a description of the method by which these compounds had been prepared.

As for thiophene, mercuration of selenophene with mercuric acetate in acetic acid or with an aqueous solution of mercuric basic sulfate yielded the dimercurated compound [514]; in the latter case, a double compound of the dimercurated product and mercuric sulfate.

Again, as for thiophene, the /3-mercuration of selenophene re-quires more vigorous conditions (see, for example, [520]).

Pyrrole mercurates extremely readily. Reaction with an excess of mercuric acetate in the cold gives rise to tetra-acetoxymercuri-pyrrole [507] (cf. the action of mercuric chloride which leads to the formation of N-Hg compounds; see Chapter 16.

The action of a cold aqueous-alcoholic solution of mercuric cyanate on pyrrole gives the dimercurated derivative [510],

The mercury compounds formed by the action of mercuric chloride on pyrrole and substituted pyrroles have been used to separate the cleavage products of hemin [569].

The following compounds have been mercurated in the pyrrole ring by mercuric acetate under mild conditions (in the cold, or by heating in aqueous or alcoholic solutions): N-phenylpyrrole [570] (with the formation of di- and tetramercurated compounds, depending on the relative amounts of the reagents), indole [571] (to give 2,3-diacetoxymercuri-indole), skatole [571], methylketole [571] (to give the monomercurated compounds) and other substituted (on the nitro-gen or the a-carbon) indoles [572], carbazole and tetracarbazole [573] (with the formation of R2Hg and trimercurated products with an excess of mercuric acetate) and N-ethylcarbazole [574],

The mercurations of diphenolisatin and diresorcinolisatin have already been described in the section dealing with phenols.

I-Phenylpyrazole heated for 15 minutes on a water bath with mercuric acetate in acetic acid forms 4-acetoxymercuri-l-phenyl-pyrazole [575]; 5,5'-dimethyl-1,T-diphenylpyrazolyl gives a 4,4'-bis-acetoxymercurated compound after heating for 30 minutes under the same conditions [576], and4,4'-bis-acetoxymercuri-l , l ' . 5,5'-tetraphenyl-3,3-bipyrazolyl is formed after boiling the reac-tion mixture for 5 hours [576].

Treatment of antipyrine and of other alkyl-substituted l -ary l -5-pyrazolones with alcoholic mercuric acetate at room temperature or at 60°C results in mercuration into position 4 of the pyrazolone ring and into the benzene ring, and in addition of HgX and OR across



the double bond [577], For example, the compound

HgOCOCHi

(CH3COOHg)2C6H3-N i

has been obtained from l-phenyl-2,3-dimethyl-5-pyrazolone [577]. If, however, the hydrogen atom in position 4 is substituted by

bromine, a methyl group, or by a dimethylamino group, then even prolonged boiling is insufficient for mercuration of the whole sys-tem; the compounds with Br and NH2 in position 4 can be mercu-rated only at 160°C. 3-Phenyl-5-pyrazolone and l-phenyl-3-methyl-5-chloropyrazole undergo only mercuration on being heated with methanolic mercuric acetate, and no addition of the Hg salt to the double bond takes place [577] (see also under "Addition of mercu-ric salts to heterocyclic compounds containing double bonds in the ring or side chain", Chapter 6).

Boiling of antipyrine in aqueous solution with ClHgNH2 or with mercuric acetate resulted in the formation of a compound containing one HgX residue in the molecule, to which Ragno [578] ascribed the structure of a 4-mercurated product. According to the same author, the compound containing two HgOCOCH3 residues, obtained by heating antipyrine with mercuric acetate for 15 minutes at 150°C, is mercurated once in the pyrazole ring (in position 4) and once in the benzene ring [578],

Pyrazole mercury derivatives with N-Hg [579] and O-Hg [580] linkages have been described; see also Chapter 16.

Thiazole is mercurated after several hours of boiling with an excess of mercuric acetate in aqueous acetic acid [581], forming a trimercurated compound. Monomercurated thiazole has been obtained from 2-aminothiazole by the diazo method (see Chapter 7).

Milder conditions have been found sufficient for the mercuration in position 5 of 2-amino- and 2-amino-4-methylthiazole [582] (action of aqueous mercuric acetate in the cold), 2-acetylaminothiazole [583] and 2-acetylamino-4-arylthiazoles [582] (brief heating on a water bath) and 2-acetylaminothiazole (in the cold) [582]. 2-Acetyl ami no-4-arylthiazoles have also been mercurated by brief boiling with mercuric chloride and sodium acetate in alcoholic or aqueous-alcoholic solutions [584, 585], On the basis of their low solubilities, it is suggested [582] that the products of the mercuration with mer-curic acetate contain N-Hg as well as C-Hg linkages.

2-Acetylamino-4-hexylthiazole heated for 30 minutes at 125 0C with sodium and mercury acetates in acetic acid gave 2-acetylamino-4-hexyl-5-thiazolylmercury acetate [586].

The mercurations of arylaminothiazoles into the aromatic nucleus

MERCURATION 115

have been described in the section dealing with the mercuration of amines.

3-Arylsydnones are mercurated in position 4 by mercuric acetate or HgC^ and sodium acetate in aqueous, aqueous-methanolic, or aqueous-acetone solutions, on boiling [587] or even in the cold [588], The products are mixtures of di-4^(3-arylsydnone)-mercury and the corresponding RHgX:

A r - N C - H g X I3 4 ^ ' + C O I 1 i-/

N o Depending on the temperature and the time of reaction, the mer-

curation of 3-pyridylsydnone with HgCl2 and sodium acetate in aqueous alcohol leads to a 4-monomercurated product, to the cor-responding R2Hg, or to a complex of 3-pyridylsydnone with mer-curic chloride [589], The conditions under which these products undergo mutual interconversions have been determined [589],

2-Phenyl-a,/3-naphthotriazole boiled with mercuric acetate in glacial acetic acid yields, after evaporation of the solvent and sub-sequent heating to 145 0C, the trimercurated derivative [590]. At-tempts at the mercuration of 2,6-dimethyl-4-pyrone with a boiling alcoholic solution of HgCl2 have been described [591].

The conditions of the mercuration of the superaromatic hetero-cycles (the action of a solution of mercuric chloride in the presence of potassium acetate in the cold) have been applied to A2-chromene, obtaining 2-chloromercuri- A2 -chromene [592].

A good yield of the monomercurated compound

X h S C I

has been obtained by boiling benzo-l,4-dithiacyclohexa-2,5-diene with mercuric chloride in alcohol [593], whereas the action of mercuric acetate gave more complex products from which no pure substance eould be isolated [593],

The mercuration of pyridine proceeds very much less readily than those of the other heterocyclics: 2% hours of heating with mercuric acetate in a sealed tube are necessary, at a temperature of 180 0C (155 0C according to [594]). According to Sachs and Eberhartinger [595], the products of this reaction and compounds mercurated with one or two Hg atoms in the /3-position; under the same conditions, McCleland and Wilson [596] obtained only the /3-chloromercuripyridine (after the addition of NaCl). A double compound of pyridine and HgCl2 was also formed [597].

Swaney et al. [594] recommend heating for 2% hours at 155 0C



in the presence of a little water (to prevent the formation of poly-mercurated products) for the mercuration of pyridine with mer -curic acetate; the yield of the /3-substituted monomercurated product is 49.5%.

It is interesting to note that the introduction of mercury into pyridine obeys the usual orientation rules of electrophilic sub-stitution, in contrast, for example, to the case of the mercuration of nitrobenzene with mercuric acetate.

3-Pyridylmercury chloride has been obtained by the diazo method [598]; its properties are described in [599]. 2-Chloromercuripyri-dine and 6-chloro-3-chloromercuripyridine have been obtained through the corresponding sulfinic acids [599],

a-Picol ine and mercuric acetate at 150°C give a compound monomercurated in position 5 (?); the yield is 61% [594],

a-Picol ine gives the /3-monomercurated product on heating for 6 hours with an aqueous solution of mercuric acetate to I lO0C in a sealed tube [600].

Pyridine oxide has been mercurated by heating with mercuric acetate in the presence of acetic acid for 2-3 hours at 100-130 °C. The product of this reaction was not the 4-mercurated compound [601] but a mixture of compounds mono- and dimercurated in position a [602, 603], If the a-monomercurated product alone is required, the ratio of the pyridine oxide to the mercuric acetate must be 6:1 [602]. The main product of the mercuration with HgSO4 in the presence of a large amount of sulfuric acid is the /3-substituted compound [603],

The mercuration of xanthone has already been mentioned in the section dealing with the mercuration of aromatic ketones.

The activation of the molecule by class I substituents is pro-nounced particularly sharply in the case of pyridine: 2-amino-[604-605] and 2-hydroxypyridines can be mercurated in cold aqueous or alcoholic solutions. The 2-aminopyridine gives a 3,5-dimereurated product [605]. 2-Acetylaminopyridine heated gently with methanolic mercuric acetate [605] or with HgO [606] gives directly the symmetric compound R2Hg fWhosestructureisprobably

2-Aminopyridine [594] and 2- [605, 607], 3- [607] and 4- [607] hydroxypyridines are also mercurated by boiling in water (the products obtained from the hydroxypyridines were, respectively, 3,5-diacetoxymercuri-2-hydroxypyridine, 2-acetoxymercuri-3-hy-droxypyridine and 3-acetoxymercuri-4-hydroxypyridine [607]). On the other hand, 4-aminopyridine is mercurated in positions 3 and 5 on heating for 28 hours at 140°C with HgO in acetic acid [608].

MERCURATION 117

Quinoline [609, 610], isoquinoline [609, 611] and the methyl-quinolines [609, 610, 612] also require fairly vigorous conditions (heating for several hours at 1500C with mercuric acetate). Quino-Iine gives two monomercurated compounds (in positions 3 and 8) and a dimercurated derivative. In isoquinoline, the mercury enters into the pyridine ring, in the position /3 to the nitrogen. However, in the case of quinoline, the presence not only of a hydroxy 1 group but even of -COOH or -SO3H allows the mercuration to be per-formed under milder conditions - in cold aqueous solution (8-hy-droxyquinoline [9, 613-615] and its bromo and dibromo derivatives [613]) or on boiling (2-hydroxyquinoline-8-carboxylic acid [615], 8-hydroxyquinoline-5-sulfonic acid [615], /3-phenylcinchoninic acid [615-617] and quinoline-8-sulfonic acid [615]).

Quinoline oxide [601] and the 6-methyl- and 4-bromo-quinoline oxides heated to 130-140°C for 1-4 hours take up mercuric acetate into the benzene ring in position 8. In 8-bromoquinoline oxide, sub-stitution occurs under these conditions in the pyridine nucleus [463],

The mercuration of 5-nitro-8-hydroxyquinoline with mercuric acetate at 90°C, at pH 3 and5.2, for 12 hours, leads to the isolation of a product in the form of a complex mercury phenoxide, mercu-rated in position 7 [309]. The mercuration of acridine has been described in a patent [618].

The sodium salt of 2,6-dihydroxy-4-aminodihydropyrimidino-acetic acid interacts readily with mercuric salts to give a carbon-mercurated product [619].

The mercurations of phenosafranine and its homologs are described in [620].

The mercuration of position 8 in the imidazole rings in purine bases (methylcaffeine, tetrachloromethylxanthine, methyltrichloro-caffeine) takes place with relative ease when the bases are boiled in aqueous solution with mercuric acetate [621].

Several hours of boiling of methylene blue with 5 moles of mer-curic acetate in an aqueous solution acidified with CH3COOH result in a very small yield of the monomercurated product; its structure has not been established [622]. The benzene derivative of the leuco base of methylene blue gives, after boiling for 20 minutes with 3 moles of mercuric acetate in an aqueous-alcoholic solution acidified with CH3COOH, a 52% yield of monomercurated product, in which the position of the mercury atom has not been determined [622],

Mercuration of thiophene [511, 512] , A mixture of 10 g of thiophene, 100 g of ethanol, 100 g of aqueous HgC l 2 saturated in the cold and 200 g of 33% aqueous sodium acetate is set aside f o r 4-5 days in a large f lask, with frequent shaking. The white crysta l l ine p r e -cipitate, consisting of a mixture of mono- and dimercurated compounds, is recrys ta l l i zed f rom alcohol (better f rom acetone [512]). a -Th i eny lmercury chloride c rys ta l l i z es our-m.p. 183°C.

The insoluble residue is the dimercurated compound, it decomposes, without melting, at about 275°C [514],

Under these conditions, 85 g of thiophene g ive a f ter 6 days 21T g of the mono- and 18 g of the dimercurated product [512],



Mercuration of furan [489], A solution of 1088 g of sodium acetate in 4 l iters of water and then 136 g of furan in 850 ml of alcohol are added to a solution of 540 g of mercuric chloride in 8 l i ters of water. Precipitation begins at once and is complete after 2 days. At the end of this time the solid material is f i l l e ted off, extracted with boiling alcohol and f i l tered hot. The residue is 2,5-dichlototnercurifuran (164 g). On cooling, the alco-holic f i ltrate yields 202 g (33.6%) of a-chloromercurifuran; m.p. 151°C (from alcohol).

Exactly the same conditions have been used to mercurate the homologs and derivatives of thiophene and furan as mentioned earl ier in this chapter.

The melting-point of 2-chloromercUri-5-methylfuran is 127°C [490] (134°C [489]), of 5-methyl-3-iodo-2-chloromercUrifuran 193.5°C [489], of 2-methyl-5-chloromercuri-thiophene 204°C [512] (in a bath preheated to 190eC, crystallized from alcohol), of 5-chloromercuri-2-chlorothiophene 213°C [514] and of 2-chloromercuriselenophene 201-202°C (with decomposition) [566],

Mercuration of sylvan with mercuric cyanate [510], (a) Preparation of mercuric cyanate [623]: 27.25 g of finely ground HgCl2 are dissolved in 600 ml of dry ether and 33 g of pure s i lver cyanate are added (the theoretical amount is 30.0 g). The mixture is shaken fo r 1 hour and set aside f o r a day. The solution does not contain chlorine. Extrac-tion of the residue (AgCl, AgOCN and Hg(OCN)s)With ether yields 27 g of pure Hg(OCN)2 . The preparation should be stored in a dry place, preferably under vacuum.

(b) Preparation of 5-methylfuryl-2-mercury cyanate: a solution of 24.9 g of mercuric cyanate in 440 ml of water Is mixed with a solution of 33 g of sodium acetate in 150 ml of water and 60.0 ml of sylvan added, A yellow precipitate appears after a short time. The reaction vessel is opened every day. No increase in pressure is observed on the fifth day. Af ter 8 days the precipitate is washed with water and dried in vacuum. The yield is 26.0 g (theoretical 28.3 g). The precipitate is extracted with 200 ml of ether (2.6 g of a grayish-brown substance remained undissolved) and the ethereal solution is evaporated down to 50 ml on a water bath; precipitation takes place in the form of platy crystals. After cooling itl a refr igerator, this precipitate is f i ltered off and dried in vacuum; yield: 21.3 g; m.p. 114 IlS i 5C.

Preparation of 2-methoxy-3,3-dichlOfOmerourithiophene [539], A solution of 0.1 ml of 2-methoxythiophene in 1.0 ml of ethanol is shaken for 20 hours with 8.5 g of a saturated aqueous solution of mercuric chloride ahd 1.7 g of 33% aqueous sodium acetate. The heavy white precipitate is f i l tered off, washed with water and dried. Weight 0.47 g. Two recrystallizations from a mixture of dimethylformamide and ethanol give 0.38 g (65%) of colorless needles; m.p. 268-270°C (with decomposition);

The mother liquor yields a substance which Cfystal l izes from ethanol in colorless needles (m.p. 139-141°C) and which could be 2-rtiethoxy-5-chloromercurithiophene.

Synthesis of 3,4-di(acetoxymercuri)-2-methyl-5-ethylthiophene [551 ] . Methyl-5-ethyl-thiophene (2 g, b.p. 158-159°C/761 mm) is added to a f i l tered solution of 5.1 g of mercuric acetate in 50 ml of 67% acetic acid. The mixture is shaken for 2 hours at 32-40°C. A crystalline precipitate begins. to appear after 10-15 minutes. Onthe fo l l ow ingday the precipitate is f i l tered off and washed f irst with 70% acetic acid and then with hot water and alcohol. Yield: 4.1 g (40%), Crystallization from glacial acetic acid gives 2 g of snow-white crystals, which are washed with the same solvent and then with alcohol. On being heated in a capillary at 9 degC/minute, the substance darkens at 244-245°C, melts with the appearance of brilliant black points at 249-250°C and remains unaltered on further heating to 280°C.

Preparation of tetra-ace to jymerCuri pyrrole [507]. Pyrro le (1 g ) is added to a solu-tion of 15 g of mercuric acetate in 60 ml of water, and the mixture, which evolves some heat, is shaken up f o r several minutes. A white crystalline precipitate of tetra-acetoxv-mercuripyrrole appears at once and its quantity increases on the addition of a littlp u-monia. The compound decomposes on heating, does not melt and is insoluble in the usual solvents.

MERCURATION 119

Preparation of 2,3-di ace toxymercuri pyrrole [571 ] .

HgOCOCH3

HgOCOCH3

A solution of 27.22 g of mercur i c acetate in 100 ml of water is treated with 5 g of indole and the mixture st i rred v igorously f o r 1 hour. The voluminous white precipitate is f i l t e red of f , washed with water to a negative reaction f o r the mercur i c ion in the wash-ings, then with ether, and f inally crysta l l i zed f rom glacia l acetic acid. White infusible powder.

Preparation of 4-chloromercuri-l-phenylpyrazole [575 ] . I -Pheny lpyrazo l e (8.64 g ) and 19.1 g of mercur i c acetate in 75 ml of acetic acid a re heated to 90°C f o r 15 minutes. Water (30 m l ) is then added and the solution set aside. 4 -Ace toxymercur i - 1-phenyl-pyrazo le precipitates out in the f o rm of co lor less needles; m.p. 191°C.

NaCl (0.33 g ) in 20 ml of 50% aqueous acetic acid is added at 90°C to 2.2 g of the above substance in 70 ml of 50% aqueous CH3COOH. The precipitating 4 - ch lo romercur i -1 -phenylpyrazole is recrys ta l l i zed f r om xylene; m.p. 226°C.

Preparation of triacetoxymercurithiazole [581 ] .

A solution of 0.85 g of thiazole, 9.6 g of mercur i c acetate and 1 ml of acet ic acid in 30 ml of water is ref luxed on a water bath. A white precipitate begins to appear af ter 1 hour and the reaction is complete in 12-15 hours. A f ter cooling, the precipitate is f i l t e red off, washed with water, alcohol and ether, and dr ied in air. Weight 8-8.2 g. Th is mater ia l is then washed twice with cold acetic acid and the residue recrys ta l l i z ed f r om this solvent. The substance darkens slightly around 280°C; it does not me l t at tempera-tures up to 300°C.

Mercuration of pyridine [593 ] , A mole of mercur i c acetate is dissolved in 8 moles of pyridine and treated with 8 mo les of water. The mixture is heated under pressure in a g lass or g lass- l ined vesse l f o r 2% hours at 155°C, the small amount of insoluble mater ial is f i l t e red off and the volati le substances evaporated off f r om the f i l t rate under vacuum. The residue is recrys ta l l i zed f r om benzene. 3 -Py r idy lmercury acetate is obtained in the f o rm of silky white needles; m.p. 178°C; yield: 49.2% (on the crude product). The com-pound is very soluble in water.

Mercuration of quinoline [610 ] , An excess of quinoline is heated f o r 5 hours at 150-160°C with mercur i c acetate. A precipitate of diacetoxymercuriquinol ine appears on cooling and is f i l t e red of f . On treatment with ether the f i l t rate g ives , a f ter prolonged standing, a further amount of an amorphous solid consisting of the same dimercurated compound; globular aggregates of 3-acetoxymercuriquinol ine separate out on the walls. A f t e r crysta l l i zat ion f rom water, the latter compound mel ts at 212°C [605], Evaporation of ether f rom the f i l t rate , addition of NaCl and steam-dist i l lat ion of the quinoline g ives amorphous 8-chloromercuriquinol ine.

Mercuration of purine bases [621 ] . T o 19 g of the purine dissolved in 1 l i ter of 5:100 aqueous acetic acid in a 1.51iterf lask, a solution of 30 g of mercur i c acetate in a mixture

H3COCOHg HgOCOCH3

HgOCOCH3



of 200 ml and 10 ml of acetic acid is added. The mixture is boiled for 2 days, f i l tered and slowly evaporated down to about 300 ml. 8-Acetoxymercuripurine crystal l izes out on cooling.

i ) Mercuration of Metallocenes

The super aromatic character of ferrocene is also shown in the fact that, in contrast to benzene, its mercuration proceeds smoothly under mild conditions: by the action of mercuric acetate, at room temperature, in a mixture of ether and alcohol. The reaction gives a mixture of mono- and dimercurated products (the latter contains one CH3COOHg group in each cyclopentadiene ring), which can be isolated in the form of the chlorides by the action of KCl in a total yield of 65% [624]. Ferrocenylmercury chloride is an orange-yellow crystalline substance, sparingly soluble in ether, benzene, methanol and ethanol; it crystallizes from xylene and butanol; m.p. 194-196°C, with decomposition. Dichloromercuriferrocene is a pale-yellow infusible powder, slightly soluble in boiling butanol, dichloroethane and xylene (a little better in hot dioxan, ethylene glycol and cyclohexanol). Dimercurated ferrocene forms even when the molar ratio of ferrocene to mercuric acetate is 2:1. The same products were obtained from the mercuration of ferrocene with mercuric acetate in acetic acid on boiling [625]. The separa-tion of mercurated ferrocenes in the form of acetates has been described [626],

By changing the relative proportions of the reagents, one can direct the reaction toward a predominant formation of the mono-or the dimercurated product [625]. When the molar ratio of ferrocene to mercuric acetate is 1:1 the products contain 64% of the di- and 19% of the mono-compound. When the above ratio is raised to 5:1, the percentage of the dimercurated product was reduced to 11 and that of the monomercurated compound was in-creased to 50. ^-Nitrophenylferrocene is mercurated less readily than ferrocene itself: the action of mercuric acetate under the conditions used for the mercuration of ferrocene (room tempera-ture, ethereal or benzene-alcoholic solution) results in a 15% yield of di(chloromercuri)-p-nitrophenylferrocene [627].

The mercuration of ruthenocene is carried out under the same conditions as that of ferrocene [628], The mercuration with mer-curic acetate in glacial acetic acid (boiling for 3 hours) has given 21-25% of the mono- and 71-79% of the dimercurated derivative.

Relatively mild conditions are also sufficient for the mercuration of cyclopentadienyl- and methylcyclopentadienylmanganese tricar-bonyls [629, 630]. These reactions are carried out with alcoholic mercuric acetate, and also mercuric acetate in the absence of sol-vent. If the starting substances are taken in a molar ratio 1:1 and the process is conducted in alcohol, the products include both the mono- and the dimercurated compounds; part of the starting cyclo-

MERCURATION 121

pentadienylmanganese tricarbonyl remains unreaeted. When the latter is in a large excess (20:1) and the reaction is carried out in the absence of solvent, only the monomercurated products are formed.

Reaction of cyclopentadienylmanganese tricarbonyl with mercuric acetate in ethanol [62*)]. A mixture of 6.12 g (0.03 mole ) of cyclopentadienylmanganese tricarbonyl, 9.56 g (0.03 mole ) of mercuric acetate and 20 ml of absolute ethanol is heated for an hour with stirring, at 70°C. Mercuric acetate passes completely into solution. A solution of 2 g of CaCl 2 in 20 ml of alcohol is then added to the reaction mixture at room tem-perature, the solvent evaporated off in vacuum and the residue extracted with acetone. The acetone solution is evaporated and the solid residue successively extracted with ether, benzene and acetone. The ether extract yields 1.2 g (19.6%) of the starting com-pound, the benzene extract 3.23 g (24.5%) of chloromercuripentadienylmanganese tr i-carbonyl (m.p. 135-136°C) and the acetone extract 2.8 g (13.9%) of di (chloromercuri )-cyclopentadienylmanganese tricarbonyl (a cream-colored infusible powder, soluble in acetone, insoluble in benzene, ethanol and chloroform).

Cyclopentadienylrhenium tricarbonyl has been analogously mer-curated with mercuric acetate in ethanol, with the formation of mono- and dimercurated products [631].

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II, 778 (1936). 226. T. A. Henry and T. M. Sharp, J. chem. Soc. 2432 (1926). 227. I. W. Haugh, C. E. Garland and H. H. Pray, J. Am. chem. Soo.,

53, 2697 (1931). 228. R. Brieger and W. Schulemann, J. prakt. Chem., Ser. 2, 89,

134 (1914). 229. P. Neogi and G. K. Mukherjee, J. Indian chem. Soc., 12, 211

(1935). 230. E. Bamberger, Ber. dt. chem. Ges., 31, 2626 (1898). 231. I. G. Kerkhof, Reel Trav. chim. Pay-Bas Belg., 51, 755 (1932). 232. J. B. Niederl and A. J. Shukis, J. Am. chem. Soc., 66, 844

(1944). 233. J. B. Niederl and R. H. Nagel, ibid., 63, 1235 (1941).

MERCURATION 129

234. U.S. Pat. 2,137,236 (1934); Chem. ZentBl., I, 5007 (1939). 235. U.S. Pat. 2,163,745 (1934); ibid., II, 3148 (1939). 236. U.S. Pat. 2,217,155 (1941). 237. M. C. Hart and H. P. Andersen, J. Am. chem. Soc., 57, 1059

(1935). 238. T. Ono, Referat. Zh., Khim., 66,175 (1957). 239. A. Wayne-Ruddy and J. Burt, J. Am. pharm. Ass., 28, 286

(1939); Chem. ZentBl., II, 1859 (1939). 240. E. Mameli, Gazz. chim. ital., 52, 18 (1922). 241. U,S. Pat, 2,240,025 (1941). 242. U.S. Pat. 1,928,436 (1931); Chem. ZentBl., I, 248(1934). 243. U.S. Pat. 1,630,072 (1923); ibid., II, 1080 (1927). 244. U.S. Pat. 1,953, 263 (1932); ibid., II, 2103 (1934). 245. U.S. Pat. 1,985,949 (1931); ibid., II, 1581 (1935). 246. T. Ono, J, pharm. Soc. Japan, 76, 722 (1956); Chem. Abstr.,

51, 324 (1957). 247. S. E, Harris and W. G. Christiansen, J. Am. pharm. Ass.,

22, 723 (1933). 248. I. Reichel and L . Rod, Referat. Zh., Khim., 5, 15,460 (1959). 249. A. Leys, J. Pharm. Chim., Paris, 6, 21, 358 (1905); Chem.

ZentBl,, I, 1531 (1905). 250. C. Lefevre and C. Desgrez, C. r . hebd. Seanc. Acad. Sci.,

Paris, 200, 762 (1935); Chem., ZentBl., I, 3784(1935). 251. Brit. Pat. 312,246 (1928). 252. Austr. Pat. 114,031 (1928). 253. S. S. Guha-Sircar and M. K. Rout, J. Indian chem. Soc., 29,

769 (1952). 254. H. Fukamauchi, J. pharm. Soc. Japan, 64, 305 (1944); Chem.

Abstr., 45, 8472 (1951). 255. H. Fukamauchi, J. pharm. Soc. Japan, 64, 310 (1944); Chem.

Abstr., 45, 2897 (1951). 256. R. B. Sandin, J. Am. chem. Soc., 51, 479 (1929). 257. M. C. Hart and A. D. Hirschfelder, J. Am. chem. Soc., 42,

2678 (1920). 258. M. Dominikiewicz1 Roczn. Chem., 12, 79 (1932). 259. N. Boon-Long, J. pharm. Ass. Siam, 4, 5 (1948); Chem.

Abstr,, 43, 5017 (1949). 260. Brit, Pat, 24,981. 261. T. Ono, J. pharm. Soc. Japan, 76, 726 (1956); Chem. Abstr.,

51, 270 (1957). 262. J. C, Sipos, H. Sawatzky andG. F.Wright, J. Am. chem. Soc.,

77, 2759 (1955). 263. O. Dimroth, Ber. dt. chem. Ges., 54, 1504 (1921). 264. W. Manchot, Justus Liebig's AnnlnChem., 421, 331 (1920). 265. M. S. Kharasch and L . Chalkley, J. Am. chem. Soc., 46, 1216

(1924). 266. W. D. Schroeder and R. Q. Brewster, ibid., 60, 751 (1938). 267. F. J. Sowa, U.S. Pat. 2,607,790 (1952).


268. J. W. Morton, Iowa St. Coll. J. Sci., 28, 367 (1954); Chem. Abstr., 49, 8162 (1955).

269. H. C. Brown and M. Dubeek, J. Am. chem. Soc., 82, 1939 (1960).

270. E. Mameli, Gazz. chim. ital., 52, 23 (1922). 271. U.S. Pat. 2,392,811 (1946). 272. N. L . Drake, H. C. Harris and C. B. Jaeger, J. Am. chem.

Soc., 70, 168 (1948). 273. S. S. Guha-Sircar and S. K. Datta, J. Indian chem. Soc., 27,

357 (1950). 274. S. K. Datta and G. Banergee, ibid., 30, 568 (1953). 275. K. C. Joshi and S. C. Bahel, ibid., 37, 365 (1960). 275a. K. C. Srivastava, Bull. chem. Soc. Japan, 37, 583 (1964). 276. A. N. Nesmeyanov and R. Kh. Shatskaya, Zh. obshch. Khim.,

5, 1268 (1935). 277. J. Chauveau, Bull. Soc. chim. Fr., 614 (1949). 278. R. Priester, Reel. Trav. chim. Pays-Bas Belg., 57, 811

(1938). 279. A. J. Shukis and R. C. Tallmann, J. Am. chem. Soc., 66,

1462 (1944). 280. F. C. Whitmore and E. Middleton, ibid., 45, 1330 (1923). 281. T. A. Henry and T. M. Sharp, J. chem. Soc., 121, 1055

(1922). 282. T. A. Henry and T. M. Sharp, ibid., 2279 (1930). 283. T. A. Henry and T. M. Sharp, ibid., 125, 1049 (1924). 284. V. Paolini, Gazz. chim. ital., 51, 188 (1921). 285. G. Rossi and M. Ragno, Annali Chim. appl., 29, 146 (1939);

Chem. ZentBl., II, 2771 (1939). 286. J. A. Pearl, J. Am. chem. Soc., 70, 2008 (1948). 287. T. M. Sharp, J. chem. Soc., 852 (1937). 288. German Pat. 463,517 (1923). 289. R. E. Dessy and J.-Y Kim, J. Am. chem. Soc., 82, 686

(I960). 290. German Pat. 486,494 (1922). 291. G. Buroni, Gazz. chim. ital., 32, 11, 307 (1902). 292. C. J. Lintner, Z. angew. Chem., 13, 708 (1900). 293. V. Paolini, Gazz. chim. ital., 65, 836 (1935). 294. E. Rupp and H. Gersch, Arch. Pharm., Berl., 265, 323 (1927);

Chem. ZentBl., II, 607 (1927). 295. F. Boedecker and O. Wunstorf, Arch. Pharm., Berl., 263,

430 (1925); Chem. ZentBl., I, 60 (1926). 296. T. Ukai, Y. Yamamato, S. Kanatomo and K. Matsushiro,

J. pharm. Soc. Japan, 75, 280 (1955); Chem. Abstr., 50, 1665 (1956).

297. W. Schoeller, W. Schrauth and R. Hueter, Ber. dt. chem. Ges., 53, 634 (1920).

298. P. Brenans and B. Rapilly, C. r. hebd. Seanc. Acad. Sci., Paris, 193, 55 (1931).

MERCURATION 131

299. R. Brieger, Chem. ZentBl., I, 753 (1912). 300. I. Gadamer, Arch. Pharm., Berl., 256, 263 (1919); Chem.

Abstr., 13, 1364 (1919). 301. S. S. Guha-Sircar and M. K. Rout, J. Indian chem. Soc., 29,

779 (1952). 302. German Pat. 255,030 (1911). 303. K. Ishihara, J. pharm. Soc. Japan,49,134,140 (1929); Chem.

ZentBl., I, 47, 48 (1930). 304. German Pat. 248,291 (1910). 305. O. Gerngross and H. Kersasp, Justus Liebig's Annln Chem.,

406, 248 (1914). 306. H. Buchtala, Hoppe-Seyler's Z. physiol. Chem., 83, 249

(1913). 307. H. Schmidt, Pharm. Ztg, Berl., 60, 724 (1916). 308. German Pat. 229,781 (1909). 309. T. Ono, J. pharm. Soc. Japan, 76, 729 (1956); Chem. Abstr.,

51, 270 (1957). 310. G. Engelmann, Chem. Abstr., 7, 2094 (1913). 311. H. Lajoux, ibid., 9, 2527 (1915). 312. A. Lespagnol and D. Bar, Bull. Soc. chim. Fr. , 5, 3, 1107

(1936). 313. H. Fukamauchi, J. pharm. Soc. Japan, 64, 309 (1944); Chem.

Abstr., 45, 8473 (1951). 314. A. L. Fox and F. C. Whitmore, J. Am. chem. Soc., 51,

2196 (1929). 315. S. C. Overbaught and R. B. Sandin, ibid., 57, 1658 (1935). 316. F, C. Whitmore and E. Middleton, ibid., 44, 1546 (1922). 317. E. Ruppe and A. Herrmann, Arch. Pharm. Berl., 254, 500

(1916); Chem. ZentBl., 1, 10 (1917). 318. G. W. Raiziss, I. A. Kolmer and J. L . Gavron, J. biol.

Chem., 40, 533 (1919). x

319. I. Stieglitz, M. S. Kharasch and M. E. Hanke, J. Am. chem. Soc., 43, 1185 (1921).

320. Brit. Pat. 12,472 (1908). 321. E. Maschmann, Ber. dt. chem. Ges., 59, 216 (1926). 322. German Pat. 394,363 (1920). 323. K. G. Naik and A. D. Patel, J. chem. Soc., 1043 (1934). 324. R. N. Sen and D. Chakravarti, J. Indian chem. Soc., 6, 847

(1929); Chem. ZentBl., I, 2244 (1930). 325. R. N. Sen and D. Chakravarti, J. Indian chem. Soc., 7, 247

(1930). 326. S. Z. Ahmad and R. D. Desai, Proc. Indian Acad. Sci., A, 5,

277 (1930); Chem. ZentBl., II, 229 (1937). 327. S. Z. Ahmad and R. D. Desai, Proc. Indian Acad. Sci., A, 6,

89 (1937); Chem. ZentBl., I, 4627 (1938). 328. P. S. Rao, V. D.N. Sastri and T. R. Seshadri, Chem. ZentBl.,

II, 638 (1939). 329. C. Smith and A. D. Mitchell, J. chem. Soc., 93, 847 (1908).


330. A. D. Mitchell and C. Smith, ibid., 95, 1430 (1909). 331. A. Proskouriakoff and G. W. Raiziss, J. Am. chem. Soc.,

47, 1374 (1925). 332. F. R. Greenbaum, Am. J. Pharm., 101, 34 (1929). 333. F. C. Whitmore and G. J. Leuck, J. Am. chem. Soc., 51,

2782 (1929). 334. E. C. White, ibid., 42, 55, 123 (1920). 335. U.S. Pat. 1,549,942 (1921). 336. German Pat. 308335 (1914). 337. H. L. Rohatgi, Referat. Zh., Khim., 4, 14,576 (1960). 338. T. Ono, J. pharm. Soc. Japan, 76, 733 (1956); Chem. Abstr.,

51, 313 (1957). 339. German Pat. 201,903 (1906). 340. H. L. Rohatgi, Indian J. appl. Chem., 21, 2, 102 (1958). 341. R. B. Sandin and J. W. Sutherland, J. Am. chem. Soc., 51,

1773 (1929). 342. A. Novelli, An. Farm. Bioquim., B. Aires, 4, 29 (1933);

Chem. ZentBl., I, 3691 (1935). 343. S. E. Harris and W. G. Christiansen, J. Am. pharm. Ass.,

23, 108 (1934); Chem. ZentBl., I, 3590 (1934). 344. U.S. Pat. 1,954,619 (1932). 345. U.S. Pat. 1,952,166 (1931). 346. H. L. Rohatgi and U. Sharma, Indian J. app. Chem., 22,

128 (1959). 347. Y. Nogase and T. Ono, J. pharm. Soc. Japan, 73, 1337 (1953);

Chem. Abstr., 49, 254 (1955). 348. Y. Nogase and T. Ono, J. pharm. Soc. Japan, 73, 1340 (1953);

Chem. Abstr., 49, 254 (1955). 349. L. C. Pan, Chem. ZentBl., II, 3745 (1937). 350. U.S. Pat. 1,692,237 (1927). 351. A. Candeli, Chem. Abstr., 44, 4635 (1950). 352. U.S. Pat. 1,860,003 (1925). 353. U.S. Pat. 1,786,172 (1927). 354. U.S. Pat. 1,863,241 (1928). 355. F. Dunning and L. H. Farmhold, J. Am. chem. Soc., 51,

804 (1929). 356. U.S. Pat. 1,863,268 (1929). 357. W. C. Harden, J. Am. Chem. Soc., 49, 3141 (1927). 358. U.S. Pat. 186,133 (1930). 359. U.S. Pat. 1,757,176 (1928). 360. T. Ukai, Y. Yamamoto and M. Yotsuzuka, Chem. Abstr.,

50, 5665 (1956). 361. T. Ukai, Y. Yamamoto, M. Yotsuzuka and F. Ichimura, J.

pharm. Soc. Japan, 76, 657 (1956); Chem. Abstr., 51,280 (1957).

362. G. Webb, Iowa St. Coll. J. Sci., 17,152 (1942); Chem. Abstr., 37, 3413 (1943).

363. H. Gilman and F. Webb, J. Am. chem. Soc., 71, 4062 (1949).

MERCURATION 133

364. A. M. Caccia-Bava and T. Vitali, Annali Chim., 40, 21 (1950). 365. G. Sachs and M. Ott, Ber. dt. chem. Ges., 59, 171 (1926). 366. T. Ukai, Y. Yamamoto, S. Hirano and M. Yotsuzuka, Pharm.

Bull., Tokyo, 3, 105 (1955); Chem. Abstr., 50, 10,033 (1956). 367. A. M. Caccia-Bava and T. Vitali, Annali Chim. appl. 38, 460

(1948). 368. F. Arndt andG. Traverso, Ber. dt. chem. Ges., 89, 124 (1956). 369. U.S. Pat. 1,984,174 (1933). 370. A. Piccinini and G. Ruspaggiari, Gazz. chim. ital., 22, 604

(1892); Chem. ZentBl., I, 564 (1893). 371. L. Vecchiotti, Gazz. chim. ital., 44, 35 (1914). 372. T. C. Bruice, J. Am. chem. Soc., 72, 1398 (1950). 373. W. R. Koehler and R. M. Dowben, Arch. Biochem. Biophys.,

93, 501 (1961). 374. S. S. Guha-Sircar and J. Mitra, J. Indian chem. Soc., 28,

80 (1951). 375. L. Pesci, Gazz. chim. ital., 23, 521 (1893); Ber. dt. chem.

Ges., 27, 128 (1894). 376. L. Pesci, Z. anorg. allg. chem., 15, 208 (1897). 377. A. Piccinini, Gazz. chim. ital., 23, 534 (1893). 378. L. Prussia, ibid., 27, 14 (1897). 379. L. Prussia, ibid., 28, 129 (1898). 380. M. S. Kharasch and I. Piccard, J. Am. chem. Soc., 42, 1860

(1920). 381. F. C. Whitmore, ibid., 41, 1841 (1919). 382. L. Pesci, Gazz. chim. ital., 28, 101 (1898). 383. L. Pesci, Z. anorg. allg. Chem., 17, 276 (1898). 384. F. Reitzenstein and G. Stamm, J. prakt. Chem., Ser. 2, 81,

159 (1910). 385. W. Schrauth, W. Schoeller and J. Rother, Ber. dt. chem. Ges.,

45, 2808 (1912). 386. L. Vecchiotti, Gazz. chim. ital., 51, 208 (1921). 387. L. Vecchiotti, ibid., 56, 155 (1926); 54, 41 (1924). 388. L. Vecchiotti and Copertini. ibid., 59, 525 (1929). 389. L. Vecchiotti and A. Ajuto, ibid., 65, 832 (1935) 390. W. A. Jacobs and M. Heidelberger, J. biol. Chem., 20, 513 391. W. Bradley and I. Wright, J. chem. Soc., 640 (1956). 392. F. Bell, ibid., 133, 2770 (1928). 393. A. Bernardi and M. Tartarini, Gazz. chim. ital., 57, 223

(1927). 394. E. McMahon and C. S. Marvel, J. Am. chem. Soc., 52, 2528

(1930). 395. G. Rossi and B. Cechetti, Gazz. chim. ital., 55, 869 (1925). 396. E. K. Weisburger, J. H. Weisburger and F. E. Ray, J. org.

Chem., 16, 1697 (1951). 397. M. S. Kharasch and I. M. Jacobsohn, J. Am. chem. Soc.,

43, 1894 (1921). 398. U.S. Pat. 2,536,750 (1951).


399. M. K. Rout, J. Indian chem. Soc., 33, 796 (1956). 400. H. K. Pujari and M. K. Rout, ibid,, 31, 257 (1954). 401. P. N. Bhargava and M. Nagabushanam, ibid., 36, 434 (1959). 402. N. K. Das, G. N. Mahapatra and M. K. Rout, ibid., 32, 55

(1955) 403. M. K. Rout, B. Padhi and N. K. Das, Nature, Lond., 174, 516

(1954). 404. G. N. Mahapatra and M. K. Rout, J. Indian chem. Soc., 31,

933 (1954). 405. G. N. Mahapatra and M. K. Rout, J. scient. ind. Res., B, 13,

378 (1954). 406. G. N. Mahapatra, J. Am. chem. Soc., 79, 988 (1957). 407. H. K. Pujari and M. K. Rout, J. scient. ind. Res., B, 14, 448


715 (1955). 409. M. K. Rout, ibid., 33, 690 (1956). 410. M. K. Rout and H. K. Pujari, J. Am. chem. Soc., 75, 4057


653 (1957). 412. G. N. Mahapatra and M. K. Rout, J. scient. ind. Res., B,

13, 407 (1954). 413. G. N. Mahapatra, J. Proc. Instn Chem. India, 31, 113 (1959). 414. P. N. Bhargava and R. P. Rao, J. Indian chem. Soc., 32,

463 (1955). 415. P. N. Bhargava, A. J. Pantuly and R. P. Rao, ibid., 34,

475 (1957). 416. P. N. Bhargava and M1 S. Sastry, J. scient. Res. Banaras

Hindu Univ., 6, 196 (1955); Chem. Abstr., 52, 11,821 (1958). 417. P. N. Bhargava, R. P. Rao and M. S. Sastri, J. Indian chem.

Soc., 33, 596 (1956). 418. B. B. Raul and G. N. Mahapatra, J. Indian chem. Soc., 38,

919 (1961). 419. R. P. Rao, Proc. Indian Acad. Sci., A, 29, 101 (1960). 420. R. P. Rao, J. Indian chem. Soc., 38, 787 (1961). 421. K. C. Joshi and S. C. Bahel, ibid., 39, 121 (1962). 422. S. S. Guha-Sircar and K. K. Patnaik, ibid., 27, 535 (1950). 423. G. N. Mahapatra, ibid., 33, 923 (1956). 424. L. Pesci, Z. anorg. allg. Chem., 15, 222 (1897); Gazz. chim.

ital., 24, 449 (1894); Chemikerzeitung, 23, 58 (1899). 425. A. Piccinini, Gazz. chim. ital., 24, 453 (1894). 426. G. Rossi and C. Bocchi, ibid., 55, 93 (1926). 427. G. Rossi, ibid., 52, 189 (1922). 428. M. Raffo and G. Rossi, ibid., 44, 109 (1914). 429. M. Raffo and G. Rossi, Chem. ZentBl., II, 2070 (1912). 430. M. Raffo and G. Rossi, Gazz. chim. ital., 42, 623 (1912). 431. A. Bernardi, ibid., 56, 337 (1926).

MERCURATION 135

432. G. Rossi and C. Bocchi, ibid., 56, 817 (1926). 433. A. Proskouriakoff and R. J. Titherington, J. Am. chem. Soc.,

52, 3978 (1930). 434. M. Ragno1Annali Chim. appl., 29, 414 (1939); Chem. ZentBl.,

I, 532 (1940). 435. M. Ragno, Annali. Chim. appl., 30, 72 (1940); Chem. ZentBl.,

I, 3247 (1940). 436. M. Ragno, Gazz. chim. ital., 70, 424 (1940). 437. M. Ragno, Annali Chim. appl., 29,148 (1939); Chem. ZentBl.,

II, 2771 (1939). 438. M. S. Kharasch, F. W. M. Lommen and I. M. Jacobsohn, J.

Am. chem. Soc., 44, 793 (1922). 439. U.S. Pat. 1,787,630 (1923). 440. D. Goddard, J. chem. Soc., 984 (1937). 441. H. H. Hodgson and D. E. Hathway, ibid., 123 (1945). 442. H. H. Hodgson and D. E. Hathway, J. Soc. Dyers Colour.,

61, 283 (1945). 443. H. H. Hodgson and D. E. Hathway, ibid., 62, 241 (1946). 444. H. H. Hodgson and H. S. Turner, J. chem. Soc., 391 (1943). 445. W. Schoeller and R. Hueter, Ber. dt. chem. Ges., 47, 1930

(1914). 446. W. Schoeller, W. Schrauth and E. Liese, ibid., 52, 1777 (1919). 447. W. Schoeller, W. Schrauth and P. Goldaeker, ibid., 44, 1301

(1911). 448. E. Cherbuliez and M. Mori, Helv. chim. Acta, 28, 17 (1945). 449. German Pat. 264,388 (1912). 450. German Pat. 281,009 (1913). 451. G. N. Mahapatra, J. Indian chem. Soc., 34, 901 (1957). 452. G. Rodighiero, Annali Chim. appl., 39, 621 (1949). 453. S. S. Guha-Sircar and I. Ali, J. Indian chem. Soc., 28, 83

(1951). 454. T. H. Wirth and N. Davidson, J. Am. chem. Soc., 86, 4318

(1964). 455. A. Albert and W. Schneider, Justus Liebig's Annln Chem.,

465, 257 (1928). 456. E. Maschmann, ibid., 450, 85 (1926). 457. L. Chalkley, J. Am. chem. Soc., 63, 981 (1941). 458. L. Chalkley, Science, N.Y., 91, 300 (1940); Chem. ZentBl.,

II, 46 (1940). 459. F. R. Greenbaum, Am. J. Pharm., 101, 34 (1929); Chem.

ZentBl., I, 1690 (1929). 460. U.S. Pat. 2,325,038 (1944). 461. L. Vecchiotti and A. Micchetti, Gazz. chim. ital., 56, 480

(1926). 462. T. Ukai and Y. Ito, J. pharm. Soc. Japan, 73, 821 (1953). 463. T. Ukai, Y. Yamamoto, Y. Ito, A. Yanagi and M. Yotsuzuka,

ibid., 75, 490 (1955); Chem. Abstr., 50, 5664 (1956). 464. L. Vecchiotti and N. Carani, Gazz. chim. ital., 56, 216 (1926).


465. L. Vecchiotti, ibid., 57, 485 (1927). 466. L . Vecchiotti and A. Micchetti, ibid., 55, 372 (1925). 467. L. Vecchiotti and N. Carani1 ibid., 56, 147 (1926). 468. L. Vecchiotti, ibid., 58, 231 (1928), 469. L. Vecchiotti, ibid., 58, 181 (1928). 470. L. Vecchiotti and G. Speranzini, ibid., 59, 363 (1929). 471. V. Grignard and A. Abelmann, Bull. Soc. chim. Fr t , 19, 18

(1916). 472. A. Bernardi, Gazz. chim. ital., 67, 380 (1927); Chem. ZentBl.,

II, 2833 (1937). 473. V. V. Kozlov, Zh. obshch. Khim., 18, 757 (1948). 474. S. Shanmuganathan, Chem. Abstr., 50, 7107 (1957). 475. I. S. Dokunikhin and L. A. Gaeva, Zh. vses. khim. Obshch.,

6, 112 (1961); 7, 236 (1962). 476. L. Pesci, Atti Accad. naz. Lincei Rc.,9,1, 225 (1900) Chem.

ZentBl., I, 1097 (1900). 477. L. Pesci, Atti Accad. naz. Lincei Rc., 10,1, 362 (1901); Chem.

ZentBl., II, 108 (1901). 478. German Pat. 234,914 (1910). 479. German Pat. 249,332 (1911). 480. German Pat. 229,574 (1900). 481. F. Blumental, Biochem. Z., 32, 59 (1911). 482. German Pat. 249,725 (1910), 483. F. C. Whitmore and A. L. Fox, J. Am. chem. Soc., 51, 3363

(1929). 484. F. C. Whitmore and L. L. Isenhour, ibid., 51, 2785 (1929). 485. Y. Ogata and M. Tsuchida, J. org. Chem., 21, 1324 (1956). 486. F. C. Whitmore and E. Ehrenfeld, J. Am. chem. Soc., 48,

789 (1926). 487. H. F. Walton and I. M. Martinez. J. phys. Chem., Ithaca, 63,

1318 (1959). 488. A. N. Nesmeyanov, Zh. ruask. fiz.-khim. Obshch., 61, 1393

(1929); Ber. dt. chem. Ges., 62, 1010 (1929). 489. H. GilmanandG. F.Wright, J.Am.chem.Soc.,55,3302(1933). 490. R. Paul, Bull. Soc. chim. Fr. , 2, 2233 (1935). 491. H. Norm ant, Annls Chim., 17, 335 (1942). 492. H. Gilman and N. O. Calloway, J. Am. chem. Soc., 55, 4197

(1933). 493. R. Paul, Bull. Soc. chim. Fr. , 2, 2227 (1935). 494. A. Baroni and G. B. Marini-Bettolo, Gazz. chim. ital., 70,

670 (1940). 495. W. J. Chute, W. M. Orchard and G. F. Wright, J. org. Chem.,

6, 157 (1941). 496. D. G. Manly and E. D. Amstutz, ibid., 21, 516 (1956). 497. S. A. Gillers and Z. Ya. Zelmen, Latv. PSR Zinat. Akad.

Vest., 11, 97 (1958). 498. T. Morel and P. E. Verkade, Reel Trav. chim. Pay-Bas

Belg. 70, 35 (1951).

MERCURATION 137

499. R. H. Eastman, J. Am. chem. Hoc., 72, 5313 (1950). 500. P. E. Verkade, T. Morel and H. G. Geritsen, Reel Trav. chim.

Pay-Bas Belg. 74, 763 (1955). 501. M. Fetizon and P. Baranger, C. r. hebd. Se'anc. Acad. Sci.,

Paris, 234, 2296 (1952). 502. H. Gilman and R. Burtner, J. Am. chem. Soc., 71, 1213

(1949). 503. T. Iri and S. Wakayama, Kagaku, Tokyo, 19, 231 (1949);

Chem. Abstr., 45, 4213 (1951). 504. T. Iri and S. Wakayama, Kagaku, Tokyo, 18, 328 (1948);

Chem. Abstr., 45, 4213 (1951). 505. C. D. Hurd and K. Wilkinson, J. Am. chem. Soc., 70, 739

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70 (1948). 557. F. Ya. Perveev and N. I. Kudryashova, ibid., 18, 976 (1953). 558. F. Ya. Perveev and T. N. Kuren'gina, ibid., 25, 1619 (1955). 559. S. F. Birch, T. V. Cullum, R. A. Dean and D. G. Redford,

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185 (1960).

MERCURATION 139

562. F. Challenger and S. A. Miller, J. chem. Soc., 1005 (1939). 563. A. Bezdrik, P. Friedlander and P. Koniger, ibid., 41, 232

(1908). 564. R. Weissgerber and 0. Kriiber, Ber. dt. chem. Ges., 53, 1557

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ZentBl., II, 3821 (1939). 567. Yu. K. Yur'ev, N. K. Sadovaya and M. A. Gal'bershtam, Zh.

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29, 1970 (1959). 569. G. Fisher and G. Ort, Khimiyapirrola[Chemistryof pyrrole]

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Chem. ZentBl., I, 2076 (1925). 571. Q. Mingoia, Gazz. chim. ital., 60, 509 (1930); Chem. ZentBl.,

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597. C. K. Kanvinde, R. S. Borkar, A. N. Kothare and V. V. Nad-karny, Chem. Abstr., 37, 2008 (1943).

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Chem. ZentBl., I, 3858 (1934).

MERCURATION 141

622. L . Chalkley, J. Am. chem. Soc., 47, 2055 (1925). 623. E. Soderback, Acta chem. scand., 11, 1622 (1957). 624. A. N. Nesmeyanov, E. G. Perevalova, R. V. Golovnya and

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900 (1957). 626. U.S. Pat. 2,835,686 (1958). 627. A. N. Nesmeyanov, E. G. Perevalova, R. V. Golovnya, N. A.

Simukova and 0 . V. Starovskii, Izv. Akad. Nauk SSSR, Otdel. khim., Nauk, 638 (1957).

628. M. D. Rausch, E 0. Fischer and H. Grubert, J. Am. chem. Soc., 82, 76 (1960).

629. A. N. Nesmeyanov, K. N. Anisimov and Z. P . Valueva, Izv. Akad, Nauk SSSR, Otdel. khim. Nauk, 1683 (1962).

630. E. O. Fischer and K. Pleszke, Ber. dt. chem. Ges., 91, 2719 (1958).

631. A. N. Nesmeyanov, N. E. Kolobova, K. N. Anisimov and L . I. Baryshnikova, 1135 (1964).

632. P. S. Mayuranathan, J. chem. Soc., 495 (1957).

CHAPTER 6

Addition of Mercury Salts to Unsaturated Compounds and Cyclopropane Derivatives

The addition of mercuric salts to olefins, acetylenes and their derivatives, ketenes and carbon monoxide occupies a special posi-tion among the methods of synthesizing organomercury compounds, as it allows the preparation only of substances which, so far, can rarely be made in any other way. The products are remarkable in that in their chemical properties they show clearly a duality resem-bling to some extent the dual reactivity of tautomeric compounds. In certain cases they behave as true organometallics formed by the addition of mercuric salts to the multiple bonds of unsaturated molecules, whereas in other cases (in reactions in which these adducts undergo substitution) they act like n -complexes between the mercury salts and the unsaturated compounds. Theseproperties had once given rise to a prolonged discussion concerning their structure (see below), in which some authors considered the com-pounds to be true organometallics, products of the addition of mercury salts to multiple bonds, whereas others regarded them as complex compounds (n-complexes in modern terminology).

Adducts of mercury salts to the olefins, discovered by Hofmann and Sand [1-7], are today known for a wide circle of compounds containing C=C bonds. The following types of compounds can be formed, depending on the solvent in which the addition takes place, and which always takes part in the reaction:

CH2 = CH2 + HgX2 + AlkOH -» AlkOCH2CH2HgX + HX [8, 9] (3)

a} Introduction

R e a c t i o n s o f t h e P r o d u c t s o f t h e A d d i t i o n o f M e r c u r i c S a l t s t o O l e f i n i c C o m p o u n d s

CH2 = CH2 + HgX2 + H2O — HOCH2CH2HgX + H X [ 1, 5, 7]

2CH2 = CH2 + HgX2 + H2O — O (CH2CH2HgX )2 [6] (1)

(2)

142

ADDITION REACTIONS OF MERCURY SALTS 143

CH2 = CHa + HgX2 + HOCOR -» RCOOHgCH2CH2OCOR + HX [10 — 15, 20] (4)

CH2 = CH2+ HgX2+R2NH-* R2NCH2CH2HgX+ HX [16-19] (5)

The preparation of products of the type ITCH(Z) -CHR' HgX, where Z = Ar [21-25] or the residue of acetoacetic ester [26, 26a] and R' and R " = H or Alk, and products of the type AlkSCR'H-CHR" HgX [27] is described below under "Addition of mercuric salts to double bonds".

All these compounds undoubtedly have the structure shown in the above equations, since they smoothly replace their mercury by hy-drogen on reduction with sodium amalgam or amalgamated aluminum in the presence of water, or under the action of an excess of hydra-zine hydrate [28, 29], Thus, alkanolmercury salts, (1) and (2), give the corresponding alcohols; for example, the productofthe addition to ethylene gives ethanol [7]:

HOCH2CH2HgX ^liIgHOCH2CH3

The product of the addition of StyreneC6H5CH(OH)CH2HgOCOCH3

gives phenylmethylcarbinol [30], the product of the addition to methylstyrene gives phenyldimethylcarbinol [30]:

C6H5C(CH3)OH-CH2HgOCOCH3 - C0H5 (CH3)2 COH

and the product of the addition to 3-methylcyclohexene gives 2-exo-methyl-endo-cyclohexanol [31].

Alkoxyalkylmercury salts (3) yield ethers on reaction with sodium amalgam [28]:

AlkOCH2CH2HgX !!!!HeAlkOC2H5

and the products of the addition of mercury salts in the medium of secondary amines (5) give tertiary amines. The action of iodine on products (1) yields iodohydrins, for example [5]:

HOCH2CH2HgX ^ HOCH2CH2I

This is a normal reaction of organomercury salts. Under certain conditions, the action of H2S on some of these compounds leads to replacement of the mercury by hydrogen [32] (although alkali metal sulfides give the sulfide (HOC2H4Hg)2S) [33],

The above structures of the addition products of mercury salts to alkenes are also indicated by reactions characteristic for the functional group - acylation [5, 28] of the alcoholic hydroxyl by acyl halides, e.g. hydroxyethylmercury iodide reacted with benzoyl chloride gives the benzoyl derivative C6H5COOCH2CH2HgI [5, 161], action of phenyl isocyanate, e.g. the formation of phenylurethane C6H5NHCO2CH2CH2HgBr by the action of phenyl isocyanate on

References see page 212


HOCH2CH2HgBr [34], or salt formation on the tertiary nitrogen of aminoalkylmercury salts [19]:

R2NCH2CH2HgCl + HCl - (R2HNCHaCHaHgCl)+Cl-

The alcoholic hydroxyl can also be oxidized to a ketone or an acid. Thus, the oxidation of 2-hydroxyethylmercury bromide by bromine and alkali results in bromomercuriacetic acid [1, 5]:

HOCH2CH2HgBr - BrHgCH2COOH

Permanganate oxidation of the addition products of mercury salts and olefins leads to monomercurated ketones [35]. The oxida-tion of 2-acetoxymercuricyclohexanol with hydrogen peroxide and a ferrous salt gives 2-acetoxymercuricyclohexanone [36]. Examples are also known of the removal of water from alkanolmercury salts, resulting in vinylmercury compounds [37]; thus:

(C6H5)2 COHCH2HgOCOCH3 (CH3C0) '° (C6H5)2 C=CHHgOCOCH3

Halogenomercuri groups XHg bonded to carbon behave in several reactions in the same way as in normal organomercury compounds [38] such as methylmercury chloride CH3HgCl; for example, the halogen can be replaced by an aryl group under the action of aro-matic organotin compounds and other organometallics [34]:

2HOCH2CH2HgBr + (C6H5)2 SnO + 4NaOH 2HOCH2CH2HgC6H5 + Na2SnO3

+ 2NaBr + 2Ha0

The action of diazomethane results in a somewhat similar re-placement of the halogen by the bromethyl radical [39]:

HOCHaCH2HgBr + CHaN2 HOCHaCH2HgCH2Br + N2

On the other hand, all the adducts of mercury salts to alkenes listed above easily eliminate the olefin at room temperature under the action of reagents which complex mercuric salts (KI [40], KCN [1], KCNS, etc.) or CH3I [1, 41]; for example:

ROC2H1HgCl + 4KI + H2O C2H1 + K2HgI1 + ROH + KOH + KCl

Alkanolmercury salts and their ethers are easily and quantita-tively decomposed by even dilute mineral acids, with the elimina-tion of an olefin:

ROC2H1HgX -f- HX —> ROH + C2H1 + HgX2

/S-Aminoalkylmercury salts form amine salts under the action of mineral acids, for example:

R2NC2H1HgX + HCl [R2NHC2H4HgX]+Cl-


Kinetics of the reactions of /3-hydroxy- and /3-alkoxyalkylmercury salts with acids are described in Chapter 14, and the mechanism of the action of the acids later in this chapter. The action on compounds of type (3), e.g. /3-halogenomercuriethyl methyl ether, of a compound with a more active multiple bond (keten) is also accompanied by evolution of ethylene [41].

This exceptional ease of the elimination of olefins from alkanol-mercury salts (and from the corresponding ethers), probably the clearest example of /3-elimination, had once led Manchot [42] to consider these compounds as complexes of the type C2H^Hg(OH)X, Q H4 .Hg(OAlk)X, etc. (n-complexes in modern terminology) and, as already stated at the beginning of this chapter, gave rise to a protracted discussion about their alkanol (or ether) [1-7, 33, 43-46] or complex (in general form R1R2C=CR3R^Hg(OR)X) [42, 47] struc-ture; tautomerism in the sense [48, 49]:

was also considered. The structure of the compounds under discussion has formed

the subject of a number of studies. Thus, Adams et al. [45, 46] obtained 1' -chloromercurimethyl-l,2-dihydrobenzofuran

by the addition of mercuric chloride to o-allylphenol. This adduct proved to be stable to hydrochloric acid, and, most significantly, to be capable of symmetrization under the action of sodium amal-gam. With iodine it gives l-iodomethyl-l,2-dihydrobenzofuran. Substances having analogous structure and similar properties are also obtained from allylresorcinols [50]:

The ability to undergo symmetrization cannot be reconciled with a complex structure for these substances. However, under the action of several other symmetrizing agents these compounds are cleaved to the starting allylphenols. The already mentioned aryla-tion of ethanolmercury bromide (and other similar compounds) by aromatic organotin derivatives, carried out by Nesmeyanov and Freidlina [34], led to asymmetric compounds of the type

CH2., ,OH CH2OH Il :Hg< 1

CH2-' x X CH2-HgX

OH

HO-C-C-HgC6H5



and not to diphenylmercury as demanded by a complex structure. Another reaction relevant in this context is the alkylation of ethanol-mercury bromide with diazomethane, which leads to an asymmetric compound; however the latter is unstable and decomposes above O0C with evolution of ethylene

HOCH2CH2HgCH2Br — C2H4 + HOHgCH2Br CH2O + Hg + HBr HBr + HOHgCH2Br - BrHgCH2Br + H2O

so that its structure can with equal validity be represented as a complex one [39].

Important indications of the "main valence" character of the products formed by adding mercury salts to unsaturated compounds (both to double and triple bonds; see also later in this chapter) have also been obtained by stereochemical investigations in this field.

Thus, Marvel et al. [43] demonstrated the formation of two diastereomers of the Z-menthyl ester of a-bromomercuri-/3 -phenyl-/?-methoxyhydracrylic acid during the addition of a mercu-ric salt to Z-menthyl cinnamate (an analogous product was obtained with a-bornyl cinnamate [44]). Theauthorsinterpretedthisas proof of the appearance of two new asymmetric carbons in accordance with the equation

C6H5CH = CHCOOCxoCis + HgX2 + CH3OH C6H5CH (OCH3) — C*H (HgX) COOCioHi,

and as a confirmation of Hofmann's formulae. It remained unclear why the remaining two diastereomers re-

quired by theory could not be found. Pfe i f fer [47] showed that a molecular structure of the type

COOCioHie \

C6H5CH = C* Hg(OCH3)X could explain the existence of only two diastereomers, but the ab-sence of the other two might also be due to difficulties of their isolation.

The work of Nesmeyanov and Borisov (see below) has provided the basis of the stereochemistry of products formed by the addition of mercuric salts to acetylenic compounds.

Analogous to the above, Wright showed in several investigations (largely on the examples of alicyclic alkenes) that the addition of mercuric salts to the double bond takes place stereospecifically; isomeric cis- and trans -olefins give different diastereomers not containing any admixtures of the second diastereomer (see, for example, [51]). Addition of a mercuric salt is not accompanied by cis - trans isomerization of the olefin, and "desoxymercuration" results in an olefin having the starting configuration. These data are also incompatible with the hypothesis of a complex nature for these substances.

Finally, it was found possible to obtain the substances considered


in this chapter by a method not involvingthe addition of a mercuric salt to a multiple bond. Thus, Nesmeyanov and Lutsenko synthesized l-chloromercuripropan-2-ol by the reduction of chloromercurialde-hyde, one of the f irst a-chloromercuri oxo-compounds prepared by them, with aluminum isopropoxide (further details of the work of these two authors on the preparation and behavior of the mercury derivatives of oxo-compounds will be given below).

NMR spectra of the addition products obtained by the addition of mercuric salts to ethylene in water and in methanol confirm that they are not ^--complexes, but normal compounds with cr-C-Hg bonds [52].

On the basis of all this experimental work, the organometallic character of such adducts in the spirit of Hofmann's formulae can today be regarded as established.

From their study of the distribution of cyclohexene between CCl4

and an aqueous solution of mercuric nitrate, Winstein, Lucas et al. [53] concluded that the addition of mercuric salts to alkenes passes through a preliminary stage involving the formation of complexes:

C6H10+Hg++^C6H10Hg++ (1)

C6Hi0 + Hg++ + H2O ~ C6Hi0Hg+ + OH + H+ (2)

According to the above authors, the structure of the hypothetical ion of reaction (1) can be represented by resonance formulae

CH CH+

C4H8 \

Hg++,

CH

/ C4H8

\ CH

/ Hg+,

CH\ C4H8/1 V + -

CH+ C4H8.

CH / I \ \ l /

CH Hg++

and the ion produced in reaction (2) has an analogous structure, with an OH group linked to the mercury. The authors did not dis-cuss the structure of the usual type of "Hofmann" product obtained by further transformation of these hypothetical forms.

A discussion of the electronic structures of these complexes will be found in [54].

The formation of similar mercury-olefin n-complexes of the C

type Il -*• Hg+X is today also accepted (see, for example, [55, 56]) C

as an intermediate stage in the addition of mercuric salts to double bonds (hydroxymercuration desoxymercuration reaction) on the basis of kinetic studies of both hydroxymercurations (see, for example, [57-59]) and in particular desoxymercurations under the influence of acids (see, for example, [60-65]); the additions of the mercuric salts are second-order reactions.

One possible schematic representation of the course followed



by the addition of a mercuric salt to a double bond via a stage involving a ^-complex is

^C = c ( + HgX2

v c Ii C

/ \

Hg+X + X- (a)

r\ / c Ii -C

HgX + ROH - ROC — C — HgX + X+ (b)

H+ + X - ^ H X (c)

Formation of analogous ^-complexes is also assumed in the re-actions of / 3 ~ a r y l a l k y l a c e t o a c e t a t e s and -alcohols, / 3 - d i a r y l a l k a n e s and ethyl a-(2-acetoethyl)acetoacetate in the interactions of aro-matic hydrocarbons [21-25] and acetoacetic ester [26], respectively, with olefins in the presence of mercuric salts, passing through an intermediate formation of /3-arylalkylmercury salts and l - (a-aceto-acetyl)ethyl-2-mercury esters.

According to a mechanism advocated mainly by Wright [27, 51, 66-72], who believed the concept of a "mercurinium ion" in the sense of Winstein, Lucas et al. or of a rr-complex to be insuffi-ciently conclusive, it is proposed that (especially in the case of reactions proceeding stereospecifically) the alkoxy-(ROHgX) and basic (HOHgX) mercury salts add to the olefins as molecules; for example:

HgX2 + ROH ROHgX + HX; ROHgX + R'CH = CHR' ~ ROCR'HCR'HHgX

This mechanism is also based on kinetic data, in particular on the fact that the addition is faster in alcohol than in water [66] (according to Wright, the reverse ratio of the rates should be observed if the addition were ionic). Arguments have, however, been advanced against this point of view [60-62, 64].

It is not impossible that the reactions of hydroxymercuration and alkoxymercuration proceed by various mechanisms, depending on the nature of the unsaturated compound and especially on the nature of substituents on one or both olefinic carbons [62],

The additions of OR- and HgX- groups to the double bond occur as a rule into positions trans with respect to each other, which also speaks in favor of an intermediate formation of a ^--complex [27, 51]. Sokolov and Reutov [73] demonstrated trans-addition to cyclohexene on the basis of calculations of the molecular rotations of cis- and trans-adducts. There are a few known cases of cis-addition (see [74, 75] in the bibliography).


R e a c t i o n s o f t h e P r o d u c t s o f t h e A d d i t i o n o f M e r c u r i c S a l t s t o T r i p l e B o n d s

Dual behavior of the adduets of mercury salts and acetylenic compounds appears even more distinctly, particularly for the simpler representatives of this group. Under the action of mercu-ric chloride in hydrochloric acid, alcohols [76-79], or water [79, 80], acetylene gives a product having the composition HC = CH.HgCl2

( I ) (Biginelli), to which Jenkins [77] ascribed the structure ClCH= CHHgCl (see below under "Addition of mercuric salts to triple bonds") on the basis of certain of its properties. This product undergoes symmetrization under the influence of ammonia (Chap-ter 13), forming a compound of composition (CH-CH)2HgCl2 ( I I ) , which according to its reactions could also have the structure (ClCH=CH)2Hg. The structures of these substances have been studied in detail by Nesmeyanov, Freidlina and Borisov. Both ( I ) and ( I I ) easily split out HgCl2 in the presence of reagents which combine it, such as thiosulfate, potassium cyanide, potassium iodide, hydrogen sulfide and triphenylphosphine (formation of the complex [(CeH5)3P]2HgCl2) [80], Botharealsoarylatedwithdiphenyl-dichloride, as is f ree HgCl2 itself, forming C6H5HgClin neutral and (C6Hs)2Hg in alkaline media (difference from the alkanolmercury salts [80]). Diazomethane also reacts with ( I ) as with free HgCl2, giving rise to ClCH2HgCl [39, 80].

Arylazocarboxylic salts and / 3 - c h l o r o v i n y l m e r c u r y chloride give the corresponding arylmercury chloride and ArCH=CHCl [81]. How-ever, alkali converts ClCH=CHHgCl into hydroxide, and the latter can be converted into a number of salts ClCH=CHHgX, where X = bromide, cyanide, acetate, or benzoate [82]. Moreover, iodine splits off iodochloroethylene from both compounds [80] and the action of HCl or HBr on ClCH=CHHgCl leads to the formation of vinyl chlo-ride [83]; this clearly indicates a chlorovinyl structure in these compounds.

By means of the reaction

(Cfs-ClCH=CH)3Sb + 3HgCl2 ->• 3 Cfs-ClCH=CHHgCl + SbCl3,

and then by isomerization of ^ans-ClCH=CHHgCl into the cis-iso-mer under the influence of peroxide [85], Nesmeyanov and Borisov [84] prepared the cis-isomer of / 3 - c h l o r o v i n y l m e r c u r y chloride (Biginelli 's substance) smoothly symmetrized by ammonia in ben-zene solution into liquid di-cis-(/3-chlorovinyl)mercury [86]. It was shown [86] that both Biginelli 's substance, ( I ) , and the product of its symmetrization, Jenkins' substance ( I I ) are trans - isomers. Freidlina and Nogina [87] then obtained cis-chlorovinylmercury chloride by direct combination of HgCl2 vapor with gaseous acety-lene. The kinetics of this reaction has been studied by Smirnov-Zamkov and by Shilov [88]. In their chemical behavior, these



substances resemble their imns-isomers, exhibiting a dual charac-ter: reactions of chlorovinyl organomercuries on the one hand and reactions of mercuric chloride-acetylene complexes on the other. However, the eliminations of acetylene are considerably slower f rom the cis- than from the trans-isomers.

These substances are quite stable and do not display any mutual interconversion of the stereoisomers, not only on storage either in individual state or in solution but also during symmetrization and the reverse reaction

(C1CH = CH)2Hg + HgCl2 - 2C1CH = CHHgCl

The tffwis-isomer of ClCH=CHHgCl passes into the cis-config-uration only under the influence of peroxides [85] just as trans-2-methoxycyclohexylmercury chloride converts into cis by the action of benzoyl peroxide [14]) or ultra-violet irradiation [89], (The transitions between geometric isomers of alkenylmercury compounds will be discussed in Chapter 14.) In further work, Nesmeyanov and Borisov studied the transfers of the /3-chloro-vinyl radical f rom the mercury atom to other metals, for example:

(C1CH = CH)2 Hg + SnCl2 (C1CH = CH)2 SnCl2 + Hg

2 (C1CH = CH)2 Hg + TlBr3 - (C1CH CH)2 TlBr + 2C1CH = CHHgBr

and the reverse transfers, such as

(C1CH = CH)2 SnBr2 + 2HgBr2 2C1CH =CHHgBr

Al l these transfers, studied separately in the trans- and c is-ser ies, have been rigorously demonstrated to take place without any change in the stereochemical configuration of the transferred radical (see Scheme 1).

These were the f i rst reactions on which Nesmeyanov and Borisov [90, 91] established the rule of retention of the configuration during electrophilic and homolytic substitutions at olefinic carbons. This rule has also been confirmed by the method of replacing the mer -cury atom with a radioactive isotope [92],

Transfers of alkenyl radicals by the same authors on the cis-and trans-adducts of mercuric salts to dimethylacetylene [93, 94] and diphenylacetylene [95], f irst prepared by them, also occur without any change in the stereochemical configuration.

The existence of stable cis - and (STWIS-/3-chlorovinyl compounds of mercury does not allow an explanation of the dual reactivity by tautomerism or by the presence of a labile equilibrium between the adducts and the products of their dissociation; a single struc-tural formula must be ascribed for each of these substances.

The more complicated polymercurated products obtained by the addition of mercuric salts to acetylene in aqueous media (see under "Addition of mercuric salts to triple bonds") can also split out acetylene, e.g. under the action of KCN, and also, in contrast

SCHEME 1


to the olefin derivatives, give the normal reaction of replacement of the mercury atom by hydrogen with acids, leading in the case of acetylene to acetaldehyde and in the case of allylene to acetone, as has been shown by Kucherov [96, 97]. Biltz and Mumm [98] ascribed to one of these compounds the formula (ClHg)3C-CHO. On the basis of the investigations carried out by Myddleton and Barrett [99-101] on the adducts of mercuric acetate and acetylenic acids, where the structure

-C=C-HgO 2 CCH 3 ,

OHgO2CCH3

had been demonstrated, the substance (ClHgbCCHO should probably have the structure (ClHg)2C = CH-OHgCl. In fact, the Myddleton-Barrett substances form monohalogeno-substituted oxo-compounds under the action of chlorine:

- C = C / + Cl2 C = c ( C - C H i \

O H g X H g X OH C 1 O Cl

whereas the structure

- C - C - H g X Il \ 0 HgX

would lead to the dihalogeno-ketone

I —C—C—Cl

Il \ O Cl

The action of FeCl3 gives the colored enolate

1 I C = C - H g X

OFeCl2

Chlorination of "tris(chloromercuri)acetaldehyde" leads to chloral [98], but this hardly demonstrates the structure. Anotherpossibility for these compounds is the molecular structure

—C IHHgO-HgX2

—C

advocated by Manchot [102], For the structure of another acetylene derivative, C2HO4NHg2 [103], see below under "Addition of mercu-ric compounds to triple bonds".

According to the kinetic data [88] obtained for the vapor-phase interaction of HgCl2 with acetylene (a third-order reaction), the


additions of mercuric salts to triple bonds take place via an inter-mediate formation of ^--complexes like additions of mercuric salts to the olefins.

R e a c t i o n s o f t h e P r o d u c t s o f t h e A d d i t i o n o f M e r c u r i c S a l t s t o C a r b o n M o n o x i d e

These products, f i rst obtained by Schoeller and Schrauth [104] by passing carbon monoxide at a slight pressure (2 Atm) into methanolic or ethanolic solutions of mercuric acetate, exhibit again properties which are intermediate between those of true organometallics and of complexes. The product has the structure CH3COOHgCOOCH3 or, in ethanol, CH3COOHgCOOC2H5, since it is reduced in good yield to the corresponding formic ester (by aluminum amalgam) and with halogens gives the halogenoformic ester (identified as the urethane). The acetate ion can be replaced by a halogen, giving, for example, ClHgCOOCH3. In the presence of triphenylphosphine, the latter substance symmetrizes into bis-carbomethoxyphenylmereury:

2C1 HgCOOCH3 + 2 (C9H5)3 P (CH3OOC)2 Hg + [(C6H5)3 P]2. HgCl2.

However, the products of the addition of carbon monoxide to mercu-ric salts easily eliminate C O on fusion or under the action of acids or other symmetrizing agents. It has therefore been suggested [105] that they are molecular compounds of carbon monoxide, analogous to complexes such as PtCl2.2CO, CUC1.C0.2H20 [106], and so on (see [107]).

Carbon monoxide can also add mercuric chloride in the medium of secondary amines [108]; in piperidine the product is

C5HioN—C—HgC!C5HicNH il O

The structure of the addition products of mercuric salts to carbon monoxide as true organometallic compounds XHgCOOCH3

has been confirmed by infra-red and proton resonance spectro-scopy [109]. The application of polarographic measurements to the establishment of the structure of products obtained from ethy-lene and carbon monoxide is described in [110].

S t r u c t u r e o f t h e P r o d u c t s o f t h e A d d i t i o n o f M e r c u r i c S a l t s t o O l e f i n s , A c e t y l e n e s a n d C a r b o n M o n o x i d e

As has been seen on the preceding pages, all organomercury compounds of this class (the products of the addition of mer -curic salts to ethylene, acetylene, their homologs and functional



derivatives and carbon monoxide) have the structures of true organo-metallic substances even if they imitate n -complexes in several reactions. In fact, this is only extremely easy /3-elimination. For this reason, Nesmeyanov [111] called these substances quasicom-plexes (see also [112-115]). This class of organomercuries lies in the middle of a series beginning with such organometallic com-pounds as lewisites C1CH=CHASC12 , (ClCH= CH)2ASC1 and (ClCH = CH)3AS and ending with the complex adducts of zinc salt and olefins, for example (CH3)2C=CH2.2ZnCl2.H20, described by Kondakov [116, 117] and double salts of the type PtCl2.C2H4, PtCl2.2CO, etc. [107] (^-complexes).

The dual reactivity of the products of the addition of mercury salts to olefins and acetylenes (easy elimination of the olefin and the acetylene and the approach of the metal and the anionic part of the adduct to an ionic state) has been ascribed by Nesmeyanov [118, 119] to the presence of a, a'-conjugatedbond systems in these molecules:

n c R O f " HO-CH2-CH2-HDCI ^ C = C C j

H ^ HgCl The reactivity of such systems would be characterized by the

typical occurrence of not only 1,2- but also 1,4-reactions, as a result of a transfer of the reaction center [118, 119]:

HgCl2 + CH3CH2OH 1 2 3 4 1 V

ClHg-CH2-CH2-OH+HCl< X 4

HgCl2 + CH2 = CH2 + H2O

HgCl2 + CH2 = CHCl

HgCl2+ CH =CH.

1 , 2

CIHg — CH = CH — Cl + HCI<

Since the breaking linkages are both a-bonds (a, a -conjugation), the occurrence of 1,4-reactions is simply an elimination of the starting olefin or acetylene. Raman spectra of the /3-chlorovinyl compounds of metals [120] have shown that they do not exhibit any triple-bond character, so that the quasicomplex properties are due not to a static but to a dynamic conjugation effect [118], The reason for the special properties of these compounds and of the products of the addition of mercuric salts to the olefins is the in-creased polarizability of the Hg-C (relative to the H-C) and Cl-C bonds, which are in positions 1,3, favorable for conjugation. Thus


the products obtained by the interaction of mercuric salts with cyclopropane compounds, discovered and studied by Levina et al. (see below under "Addition of mercuric salts to cyclopropane de-rivatives") , in which ClHg and OR are in the y-position, do not exhibit any quasicomplex properties.

The trans-isomers of the /3-chlorovinyl compounds of mercury (and also of other metals) exhibit appreciable quasicomplex char-acter, eliminating acetylene in the presence of reagents combining HgCl2 more rapidly than the cis - isomers. The C-Hg bond is in them more labile than in the cis-isomers. This is shown very well in the reactions of cis - trans -di-/3-chlorovinylmercury [121] and cis - trans-dipropenylmercury [122] with thallium chloride:

H Cl H Cl \ C / \ C /

2 Il Il +TlCl3 -C. C x

H

'Cl H \ N e / X

H ^Hg' .H / C \

TlCl + 2

H Cl W

H / C \

HgCl

in which the trans -chlorovinyl and trans -propenyl groups are ex-changed almost at once, while the cis -radicals remain bonded to the mercury. Moreover, the tfrans-isomers have a higher molecular refraction than the cis [123]. This is evidently due to the greater tendency towards conjugation in the trans -situated groups with parallel disposition of the axes of the a-clouds.

The dual reactivity of the products of the addition of mercury salts to carbon monoxide is also explained by the occurrence of a, cr-conjugation.

R e a c t i o n s a n d S t r u c t u r e o f a - M e r c u r a t e d C o m p o u n d s

P r o d u c t s o f t h e a d d i t i o n o f m e r c u r i c s a l t s t o v i n y l e t h e r s a n d v i n y l e s t e r s . Although the organomercury derivatives of the oxo-compounds (aldehydes and ketones), studied by Nesmeyanov, Lutsenko et al. [124] and obtained by the addition of mercury salts to vinyl ethers and vinyl acetates (and also by other routes described later in this Chapter)

/ -i- cr CH>=CHOR -I- HgAc2 + H2O -» AcHgCH2CH •> ClHgCH2CHO

\ - R O H OH

CH.,=CR'OR + HgAe3 + H2O AeHgCH2CR'OR + C'' , ClHgCH2C(O)R' I - R O H OH



do contain a highly labile C-Hg bond, they do not display quasi-complex properties. In the presence of reagents such as KCN or KI in aqueous solution, they yield acetaldehyde [125]:

ClHgCH2CHO + 4KI + H2O -» K2HgI4 + CH3CHO + HCl + KOH

However, a vinyl alkyl ether is evolved when mercuri-bis-acetaldehyde in alcohol is exposed to the action of a compound with a more reactive multiple bond - keten [41]; the ethyl ester of mercuri-bis-acetic acid is formed at the same time. These substances have the structure of mercurated aldehydes and ketones ClHgCH2CHO and ClHgCH2COR. On reduction with aluminum iso-propoxide the f irst gives the quasicomplex alcohol ClHgCH2CH2OH [124]; in the presence of ammonia chloromercuriacetone symmet-rizes to Hg(CH2COR)2 [126], The inherently improbable enolic structures ClHgCH=CHOH and ClHgCH2=O(CH)R are definitely ex-cluded, since the substances do not give reactions for active hydro-gen [125]. Enolate structures CH2=CHOHgCl andCH2=C(CH3)OHgCl, if only due to a tautomeric equilibrium such as

ClHgCH2COCH3 ^ CH2=C-CH3

I OHgCl

can also be ruled out, because mercuric oxide is not precipitated when the aqueous solutions of these compounds are treated with alkali and because chloromercuriacetone is stable to aqueous KMnO4 in the cold. At the same time, these substances contain very labile mercury. They are easily hydrolyzed by aqueous solutions of sodium hyposulfite, potassium iodide and similar compounds, which are able to complex the mercury (see above for the equation). Phenylmagnesium bromide and chloromercuri-acetaldehyde also give a quantitative yield of phenylmercury chloride [125]:

ClHgCH2CHO + C8H5MgCl - C6H5HgCl + CH2=CHOMgCl

However, under the action of acylating media, these compounds, known to be C-metallic, are acylated at the oxygen and in the presence of acetyl chloride (and benzoyl chloride) are converted [125, 127-130] into the corresponding enol acetates and enol benzoates CH 2 =CHOCOr and CH2=C(CH3)OCOR:

ClHgCH2CHO + RCOCl — CH2=CHOCOR + HgCl2

The acid chlorides of phosphoric [131], sulfonic [132] and other acids [131, 133] also acylate mercurated aldehydes and ketones at the oxygen, whereas the action of alkali metals or FeCl3 on mercurated aldehydes results in the vinyloxides of the corres-ponding metals [134].


As stated previously, the dual reactivity of chloromercuri-aldehydes and chloromercuriketones, typical of keto-enols, is due not to keto-enol tautomerism but to conjugation; in this case the conjugation is a, n, i.e. between a single and a double bond:

I 3 r\i C l H g - C - C = O

These compounds are also capable of 1,2-reactions, such as the action of bromide, which leads to bromo-substituted oxo-compounds [124],

ClHgCH2CHO + Br2 — BrCH2CHO + HgClBr

reactions of substances removing the mercury ion (see above), and reactions of alkylation by triphenylchloro- [127] and triphenyl-bromomethane [129]:

XHgCH2CHO + (C6H5)3CX (C6H5)3CCH2CHO + HgX2

On the other hand, the actionoftri (p-nitrophenyl) chloromethane [129] and especially acylations directed at the oxygen are a ref lec-tion of the 1,4-reactivity of these systems, due to a transfer of the reaction center as a result of conjugation:

I o I i C l H g - C - C = O + C l C - C H 3 * H g C l 2 4- C = C - O - C - C H 3

O

r n I n C l H g - C - C = O + C

— > • HgHa l 2 + C H 2 = C H O C ( C 6 H 4 N O 2 ) 3

P r o d u c t s o f t h e a d d i t i o n s t o k e t e n s . Foss, LutsenkoandIvanova [136] obtained esters of mercuri-bis-acetic acid by adding mer-curic oxide to keten in an alcoholic medium:

HgO + 3CH2=CO + 2R0H Hg (CH2COOR)2 + CH3COOH

and esters of monomercurated acetic acid [135] by the addition of mercuric acetate to a-alkoxyacrylonitriles:

CH 2 =C (OR) CN + Hg (OCOCH3)2 + H2O - CH3COOHgCH2COOR

Mercurated acetic acid and its esters were also obtained by these authors [41] by the action of keten on other quasicomplexes - /5-mercurated hydroxy-compounds and a-mercurated oxo-compounds [41] (this also resulted in a crossing from one type of quasicomplex compound to another). In their chemical properties, the esters of



monomercurated acetic acid are analogous to the quasicomplex compounds.

The esters of mercurated acetic acid contain two systems of conjugated bonds, mercury-carbon and carbon-oxygen, a , n (1,4) and a, a (1,4 ):

. f7\ 3p>4

— Hg —CH2 r x O 4

and their acylation proceeds in three directions:

4 O

1 2 3 /, -Hg-CH2-C^ 4, +R'COCl

OR

^ R'COCH2COOR OCOR'

1,4 / — • CH2=C/

° R

— • R'COO R + CH2=C=O

Consequently, the action of acetyl chloride on the isobutyl ester of mercuri-bis-acetic acid gave isobutyl acetoacetate (1,2-reaction) and isobutyl acetate (1,4'-reaction); the actions of acetyl chloride on the methyl ester of mercuri-bis-acetic acid and of isovaleryl chloride on the isobutyl ester of mercuri-bis-acetic acid gave, respectively, a-methoxyvinyl acetate and a-isobutoxyvinyl iso-valerate (1,4-reactions).

R e a c t i o n s a n d s t r u c t u r e o f p r o d u c t s o f t h e a d d i t i o n o f m e r c u r i c s a l t s t o a c e t y l e n i c a l c o h o l s , o x o - c o m p o u n d s a n d a c i d s . Nesmeya-nov and Kochetkov obtained products of the addition of mercuric chloride to acetylenic alcohols [138], an acetylenic Ketone [139], and to acetylenic acids and their esters [140], The resulting sub-stances exhibited the dual reactivity characteristic of quasicom-plexes.

In the product obtained by the addition of mercuric chloride to phenylethynyl methyl ketone, the Hg-C bond is conjugated with both C-Cl and C=O bonds:

i HgCi

3 CeH 5—C—C—C—CH3

e I 2 II VCl O

4 4

As in the chloromercurialdehydes and chloromercuriketones, the action of acylating agents is here directed at the oxygen [139]; the O-acylation occurs as a result of the conjugation between Hg-C and C=O bonds (reaction at 1,4 bonds of a conjugated system). At the same time, the tendency of HgCl2 toward elimination is in this compound strongly enhanced in comparison with /3-chlorovinyl


compounds, owing to the simultaneous conjugation of Hg-C with C-Cl and C=O: the compound eliminates HgCl2 not only in the presence of symmetrizing agents (KI, KCN, Na2SsO3), but also (as do the products of addition of mercuric chloride to acetylenic alcohols and acids) under the action of NaCl and even on recrystal-lization from ether [139]. Under the action of acids, the HgCl group is replaced by hydrogen; this is the usual reaction of organomer-cury compounds [139], The more pronounced quasicomplex char-acter in comparison with /3-chlorovinyl compounds of the addition products of mercuric chloride and acetylenic acids (elimination of HgCl2 not only under the influence of symmetrizing agents, in-cluding ammonia, but even under the influence of NaCl) is also explained by increased lability of the mercury atom due to the conjugation of Hg-C with C-Cl and C=O groups [140]:

The applicability of the synthesis of organomercuries by the addition of mercury salts to unsaturated compounds is fairly wide and unusual, because (with few exceptions, given later in this chapter) the substances obtained in this way cannot be prepared by any other method. The initial apparent limitations of the method (statements that mercuric salts do not add to conjugated double bonds [48], bonds conjugated with aromatic nuclei (propenyl groups) [42, 141-143], and certain trans -compounds [72, 144, 145]) have gradually disappeared. Thus, it has been found [146, 147] that butadiene [147, 148], 1,1-diphenylethylene [147], l-phenylbuta-1,3-diene [72], isoprene [147], piperylene [147] and dipropenyl [147] give the usual addition products in aqueous media, with better or worse yields; styrene and at least the a-substituted styrenes behave in the same way (see below for references).

Finally, catalysts (peroxides and BF3) have been found [149] which favor the addition of mercuric salts to certain trans -com-pounds (stilbene) which were earlier thought to be incapable of addition. On the other hand, the presence of substances forming weak complexes with mercuric salts, such as pyridine or nitriles, retards the addition of the mercuric salts to olefins [62, 149]. It must, however, be borne in mind that additions to substances con-taining the =CH2 group usually proceed more smoothly than those to substances containing =CHR or =CR'R" groups, that additions to cts-isomers are easier than those to ^ons-isomers [72, 144, 150] and that additions in alcoholic media are smoother than those in water. Thus, additions of mercuric salts to =CHR of =CR'R" com-pounds in water are occasionally accompanied by (sometimes pre-dominant) oxidation and formation of mercurous salt.

HgCI I r ^

R - C = C - C - O H



b) Addition of Mercuric Salts to Double Bonds

A d d i t i o n o f M e r c u r i c S a l t s t o A l k e n e s C y c l o a l k e n e s a n d T h e i r D e r i v a t i v e s

A d d i t i o n o f m e r c u r i c s a l t s t o o l e f i n s a n d t h e i r d e r i v a t i v e s . The well-dissociating mercuric salts (nitrate, sulfate, etc.) and salts of carboxylic acids, especially the acetate, add to ethylenic hydro-carbons by the Hofmann-Sand reaction [1]. In aqueous solution the adding groups are OH and HgX, where X is the anion of the starting mercuric salt. The addition follows Markovnikov's rule: like the hydrogen in the addition of hydrogen halide to olefins, the mercury atom becomes attached to the more hydrogenated, i.e. more nega-tive carbon (the addition of mercuric fluoride to polyfluoro-olefins constitutes an exception). The reaction yields alkanolmercury salts. In the case of ethylene, compounds XHgCH2CH2OCH2CH2HgX have been found in addition to the main product HOCH2CH2HgX, formed by condensation of the ethanolmercury salts. The structure of such products of addition to ethylene has been confirmed by proton resonance spectra [52], which also indicate that the alkanol-mercury salt (hydroxide) gradually transforms in alkaline solution into the product having the ethereal structure shown above.

In the additions of mercuric salts HgX2 to unsaturated hydro-carbons in alcohols ROH, carried out for the f irst time by Schoeller and Schrauth [8, 9], the groups adding to the double bond are RO and HgX. The direction of the addition obeys Markovnikov's rule. The addition itself is faster and easier than in water and is also easier in methanol than in ethanol. The only product of the reaction are the alkoxyalkylmercury salts ROCR'R"CR'" R " " HgX. Thus, ethylene and mercuric acetate in an alcoholic medium give raono-acetoxymercuriethyl ethyl ether CH3COOHgC2H4OC2H5 [104, 151]. The oxalate has been made in the same way [206],

The addition of mercuric acetate in acetic acid [11] has received much less attention: CH3COOCH2CH2HgOOCCH3 results from the bubbling of ethylene through a solution of mercuric acetate in glacial acetic acid. Mercuric salts of other carboxylic acids are also used (see below). The additions of mercury acylates (including mercuric acetates) are also conducted in inert solvents: dimethyl ether, ethylene glycol, dioxan, petroleum ether and so on.

Mercuric chloride can also be used for the addition to ethylenic bonds, but in this case a little alkali should be added, f irst at the beginning of the reaction and then gradually in the course of the process. This measure, however, is also generally adopted during the additions of other salts of mercury with strong acids; only mercuric acetate is added in the absence of alkali. This is because the accumulation of the strong acid as a result of reaction promotes the reverse process, whereas acetic acid in dilute solutions is in-different to the addition products. During the interaction with HgCl2


under the above conditions, olefins very frequently form a preci-pitate of a molecular compound having the composition (1 mole alkanolmercury chloride plus 1 mole HgCl2). Thus, ethylene gives HOCH2CH2HgCLHgCl2. To isolate the alkanolmercury salt, the precipitate is in such cases treated with aqueous (for example, 10%) NaOH. The mercuric chloride is then converted to HgO and the alkanolmercury salt (as the hydroxide) passes into the aqueous solution from which alkanolmercury halide is precipitated by acidification with acetic acid (instead of this, the alkali may be neutralized by passing in CO2) and simultaneous addition of an alkali metal chloride or bromide.

The more usual, and more convenient, starting salt is mercuric acetate. The reaction is carried out by adding a calculated amount of the gaseous or liquid olefin to the aqueous or alcoholic solution until a withdrawn sample no longer gives a yellow precipitate of mercuric oxide with NaOH. In general, the reaction is fairly fast. The alkanolmercury acetate either separates out directly in the form of crystals or liquid, or remains in the solution, because these acetates are often soluble in water (and even more so in alcohol). In the first case, the substance is conveniently isolated in the form of acetate; its recrystallization (from alcohols, benzene, ligroin, etc.) presents no difficulties. In the second and third cases, the substance is best converted into chlorine or bromide by careful addition of aqueous NaCl or KBr, with stirring, until no more pre-cipitate appears. An excess of the halide should be avoided, since it exerts a dissolving action.

The use of mixed salts CH3COOHgX (where X is an anion of a mineral acid) has been recommended [152] for the alkoxymercu-ration of alkenes, since HX does not then accumulate in the re-action mass.

The rate of the addition of mercuric salts to the olefins is greatest in the olefins having a terminal double bond, and rapidly becomes smaller as the double bond recedes from the end of the chain [12]. In the same way, branched olefins react faster than straight-chain ones, but of course in the series of open-chain olefins the branching only has this effect if it begins near the double bond; the products of the addition of mercuric salts to methylcyclohexenes with a methyl group more remote from the double bond, e.g. the product of the addition to 4-methylcyclo-hexene, form faster than the products of the corresponding addi-tions to 2- and 3-methylcyclohexenes [31].

Preparation of ethanolmercury hal ides [ 1 ] . Potassium hydroxide is added to a solution of mercur ic nitrate until a white basic salt is precipitated which does not redisso lve . Ethylene is passed in f o r a few minutes and the solution again becomes transparent. These operations are repeated until no more ethylene is absorbed.

The alkaline solution is then treated with a potassium halide (KC1, KBr , or KI), in an amount of 1 atom of hydrogen per atom of mercury , and the crystal l ine ethanolmercury salt is precipitated after a few hours with carbon dioxide. The product remaining in



solution can be obtained in pure form after evaporation and extraction with methanol. The compounds are recrystal l ized from methanol. HOCH2CH2HgCl, m.p. 155°C; HOCH2CH2

HgBr, m.p. 158°C (see also [153]). For other salts, see for example [236],

Preparation of a-acetoxymercuri-/3-methoxyethane [104, 154], Ethylene, f r ee of air, is passed into a solution of 20 g of mercuric acetate in 100 ml of methanol. The reaction is complete after 1 hour. A yellow oil remains after removal of the alcohol and acetic acid under vacuum, which solidifies after 24 hours in vacuum over sulfuric acid. Yield: 14 g (82%). The melting-point is 42°C after crystallization f rom petroleum ether. The halide salt is obtained by precipitating the acetate solution with potassium halide [104], The melting-point of the bromide is 58°C ( for the other salts, see [56, 155, 156]).

Preparation of the mercury derivatives of diethyl ether [ 1 ] . A neutral solution of mercuric sulfate is prepared by dissolving HgO in 30% H2S04 and by subsequently adding HgO till the beginning of a precipitation of the basic salt (which is f i l tered off ) . The solution is saturated with ethylene over 9 hours, the resulting precipitate f i l tered off washed and dissolved in 15% KOH, and the f i l tered solution treated with KCl and saturated with carbon dioxide. The chloride precipitates in the form of white crystals, m.p. 190°C. The bromide (m.p. 200°C), iodide (m.p. 161°C) [5] and other salts [56, 153, 155] are obtained in the same manner.

Addition of mercuric salts to ethylene occurs also in various hydroxyl-containing media [158],

The mercury salt of trinitromethane adds to ethylene in water and in nitromethane with the formation of l , l , l - tr ini tro-3-tr ini tro-methylpropylmercury [159]. The symmetrical compound, bistri-nitropropylmercury is also formed in the latter solvent, and it is the only product when the addition is carried out in ethanol. Trinitromethylmercury chloride also adds to ethylene (in water), with the formation of l , l , l -tr initropropylmercury-3 chloride [159], Tetranitrobutane adds to ethylene in methanol, giving the symmet-ric compound [CHsCtNO^CfyC fNC^CI^CH^Hg [159a].

Preparation of an aqueous solution of the mercury salt of trinitromethane [159] , Trinitromethane (200 g ) is added in portions of 10-15 ml to a vigorously st irred suspen-sion of 140 g of freshly prepared mercuric oxide in 1200 ml of water. The mercuric oxide gradually dissolves and a clear solution of the mercuric salt of trinitromethane is formed at the end of the reaction. The pH of this solution should not exceed 2.

Preparation of l,l,l-trinitro-3-(trinitromethylmercuri)propane [ l59 ] . A current of ethy-lene is passed at room temperature through an aqueous solution of the mercury salt of trinitromethane (10 g in 50 ml of water) placed in a cylinder. A precipitate of 1,1,1-tri-nitro-3-(trinitromethylmercuri)propane appears after 15-20 minutes. The ethylene is passed in for a total of 6 hours, the precipitate being f i l tered off after every 2 hours. The reaction mixture is then set aside for 12 hours, in the course of which some more product precipitates. Each portion of f i l tered precipitate is washed with 2-3 portions of water and dried in air. The total yield is 9.8 g (93%); m.p. 167°C (with decomposition) after slow crystallization from water.

Treatment of the product with 6N HCl at room temperature affords l , l , l - t r in i t r o -3 -chloromercuripropane. Yield: 90%; m.p. 142°C (from chloroform).

Preparation of his-(trinitropropyl)mercury [ l 5 9 ] . Ethylene is passed for 12 hours at room temperature into a solution of 10 g of the mercury salt of trinitromethane in 30 ml of ethanol. Crystals of bis-(tr initropropyl)mercury begin to appear after l - l ! 4 hours; at the end of the reaction they are f i l tered off and then washed with a little alcohol and several portions of water. Dilution of the f i ltrate with water gives a further amount of


bis- ( t r in i t ropropyl ) mercury . The total y ie ld is 9.4 g (84%). A f t e r two recrysta l l i zat ions f r o m chloro form, the melting-point is 155°C (with decomposition).

The same method has been used to obtain the symmetrical pro-duct from propylene, melting at 124-1250C (with decomposition). The compound was recrystallized from chloroform.

The additions of mercuric acetate to ethylene in polymethylene and polyethylene glycols and in monoethyl ethers of polyethylene glycols, are carried out at 70-90°C [160], If the ether is aromatic, the addition is carried out 5-10°C above its melting-point, some-times using the glycol ether as a solvent or conducting the reaction in a suspension of the glycol ether in benzene [160],

The addition of mercuric acetate to ethylene in acetic acid gives salts of /3-acetoxyethylmercury.

Preparation of /3-acetoxyethylmercury chloride [ 24 ] . Ethylene is passed at a rate of 3 l iters/hour, at room temperature, into a mixture of 80 g of mercur ic acetate and 80 g of acetic acid, until the alkali reaction f o r mercur ic ion becomes negative. The small amount of mercurous salts is f i l t e red off . The f i l t ra te is treated with 600 ml of cold water and 170 ml of 10% KCl. The resulting /3-acetoxyethylmercury chloride (42 g ) is f i l t e red off, dr ied and recrys ta l l i zed f rom l igroine; m.p. 64-65°C. The same method has been used [161] to prepare /3-acetoxyethylmercury iodide; m.p. 83-85°C.

The action of a solution of H2SO4 in glacial acetic acid on the adduct of mercuric acetate and ethylene gave the sulfate (CH3OCOCH2CH2Hg)2SO4 [162].

Mercuric chloride adds to ethylene in piperidine [16] and other amines (see below).

Preparation of N-(/3-chIoromercuriethyl)piperidine [ 16]. A suspension of 5 g OfHgCl2

in 50 ml of dry piperidine is saturated with ethylene under an excess of pressure of 35-40 cm Hg, with mechanical agitation, to the disappearance of the reaction f o r the mercur i c ion. A f t e r separation of the precipitated C 5 H 1 0 N H .HCI , the f i l t rate is evapora-ted under vacuum.

The residue is dr ied in a desiccator over H2S04 till the odor of piperidine can no longer be detected. A f t e r recrysta l l i zat ion f rom petroleum ether, the melting-point is 72-73°C. The substance el iminates ethylene with KI and KCN and is stable to acids.

The hydrochloride is obtained by saturating an ethereal solution of 0.2 g of C 5 H 1 0 N C H 2

CH 2 HgCl with a current of dry hydrogen chloride; m.p. 132°C.

Mercury polychlorophenoxides can be added to olefinic com-pounds; the reactions are carried out in an inert solvent (tetra-hydrofuran) sometimes under pressure [163],

With mercuric acetate and nitrate in water, propylene forms the corresponding propanolmercury salts, isolated as the halides (Cl1Br)XHgCH2CHOHCH3 and di(halogenomercuri-isopropyl) ether [XHgCH2(CH3)CH]20 as a side product [2, 7, 12, 157, 164-166], For the addition in alcohol, see for example [169],

The addition of the mercury salt of trinitromethane to propylene in water gives (O2N)3CCH(CH3)CH2HgCl(NO2)3, and in alcohol the corresponding symmetrical compound [159] (see below).

The additions of mercuric acetate to but-l-ene and but-2-ene



have been carried out in methanol [167].Trans- and (more readily) cis-but-2-enes add mercuric acetate both in alcoholic [168] and aqueous [150] solutions.

Under the same conditions,isobutylenegivesmethyl-2-propan-2-olmercury salts (CH3)2C(OH)CH2HgX. The existence of isobutenyl-mercury iodide, described by Hofmann and Sand [2], is doubtful. Additions of mercuric salts to amylene have been carried out in various hydroxylic solvents [158]. The addition of mercuric salt to pent-2-ene in methanol gives a mixture of vicinal methoxy-mercury chlorides [169]. The addition of mercuric acetate in water to 2,3,3-trimethylbut-l-ene has been carried out [170]:

(CH3)3CC(CH3) = CH2 + Hg (O2CCH3)2+ H2O - (CH3)3CC(CH3) OHCH2-HgO2CCH3

Mercuric salts in methanol have been added to 2- and 7-penta-decene, 1-nonadecene, undecene [342] and other olefins [12, 168],

Aqueous solution of mercuric acetate and trimethylsilylethylene give (CH3)3SiCH(HgOCOCH3)CH2OH [171].

Of the polyfluoroalkenes, trifluoroethylene and 1,1,1-trifluoro-propylene add mercuric salts under the usual conditions. The 1,1,1-trifluoropropylene gives an adduct with the mercury in position 2 [172]. The product of the addition of mercuric acetate to 1,1-difluoroethylene [172] in acetic acid by the reaction

CF2=CH2 + Hg (CH3CO2)2 - » CH jC/^CF jCHaHgOO^ 0 H ' ° .

0 CH3 " 2 H F

0 IL H1O

- (CH 3C-O-C-CH 2 -HgOCOCH 3 ) — CH3COOH + HOOCCH2HgOCOCH3 Il O

is mercurated acetic acid; in methanol, the product is the corres-ponding ester CH3OCOCH2HgOCOCH3 [172],

Whereas the action of mercuric chloride on olefins does not yield products in which the Cl and HgCl groups are added to the double bond, mercuric fluoride adds to the terminal double bond of poly-fluoro-olefins in a medium OfAsF3 [173] (at50°C, to CF2=CF2, CF2 = CHF, CH2=CF2 and CF2 =CFCl) or hydrogen fluoride [in an autoclave, at 85°C, IOO0C and sometimes at still higher temperatures, addition occurs to CF3CF=CF2 [174-176], CHF2CF2CF=CF2 [175], CF3CH=CF2

[176, 177], C1CF2CF2CF=CF2 [175], and to H(CF2)8CF=CF2 [175] and (CF3)2C=CF2] with the formation of symmetrical products R2Hg. The mercury atom goes not on the f irst but the second carbon. The general scheme of these reactions is

2R'R"C=CF2 + HgF2 (R-R-CCF3)2 Hg

Attempts to add HgF2 in a medium of hydrogen fluoride to a non-terminal double bond in such compounds as octafluorobut-2-ene and hexafluorocyclobutene were unsuccessful [175], The action of a


mixture of HgCl2 and HgF2 in the presence of hydrogen fluoride on perfluoropropylene gave (CF3)2CFHgCl [177].

Only traces of perfluoroethylmercury fluoride were obtained f rom the reaction between HgF2 and perfluoroethylene in the absence of solvent (autoclave, 4 hours at IOO0C); a 24% yield of CF3CClFHgF resulted f rom the reaction of HgF2 and CF2 =CClF under the same conditions (10 hours) [178].

The unsaturated hydrocarbons listed below easily form addition products with mercuric salts when aqueous or alcoholic solutions of the two compounds are set aside, in the cold or with slight heat-ing, for periods ranging from several hours to several days. The hydrocarbon component can also be dissolved in an organic solvent, for example ether, and added in this form to an aqueous or alcoholic solution of the mercuric salt.

Mercuric salts have been added to the following alicyclics con-taining a double bond: cyclopentene [179], dicyclopentene [7, 164], cyclohexene, 2-methyl-, 3-methyl- and 4-methylcyclohexenes [31, 185] (both the diastereomers and positional isomers were isolated in the case of the 4-methylcyclohexene; cis- and -conforma-tions were determined for the methylcyclohexylmercury bromides [188-190]), 3-phenylcyclohexene [191], methylenecyclohexane [169], santene [192], camphene [143, 193], isolaurolene [194, 195], carbo-menthene [196] and norbornene.

Many studies have been devoted to hydroxymercuration (and par-ticularly alkoxymercuration) of cyclohexene, in which the stereo-chemistry and the mechanism of the addition of mercuric salts to unsaturated compounds were investigated. Thus, studies have been carried out on the kinetics of methoxymercuration and on the sepa-ration of diastereoisomers [14, 61, 182-184] (in particular, results have been obtained which disproved the earl ier belief [14] that -OCH3, and HgX add trans with respect to one another [67, 73, 180, 182, 250]), on the kinetics and the mechanism of the additions of mercuric acetate in ethyl [70], n-propyl [70], isopropyl [13, 27] and other alcohols [17, 66, 70], and on the additions of mercuric I -lactate [14, 72], mercuric mandelate [51] in methanol, mercuric trifluoroacetate [13], mercuric nitrate [68], and of mercuric acetate in water [34, 66], ethanol [34, 72, 185], petroleum ether [66] and other solvents [29, 69, 72, 179, 183, 186, 187].

The product of the addition of mercuric acetate in water, meth-anol, or dioxan [28, 197] to norbornene, or of the addition of aqueous mercuric hydroxide perchlorate to the same hydrocarbon, is (after precipitation with sodium chloride) not the endo-3-alkoxy-ea;o-2-[28, 198] but the e»o-3-methoxy- (or hydroxy-) e®o-2-norcamphan-ylmercury chloride (I)



as has been proved [74] and confirmed by NMR [180]. This is one of the few known examples of cis-addition of OR and HgX to the double bond (see also beginning of this chapter). The action of the mercury salt of trinitromethane in water on norbornene affords not the product of the addition of X and HgX (X = (NO2)3C) but a hydroxymercurated compound, which also confirms a cis -config-uration of the addition product [198a].

The formation of cis -adducts in the hydroxymercuration of cyclic alkenes is favored by strain in the unsaturated molecule [74]. Thus, similarly to the case of norbornene, cis -hydroxymer-curation products have been obtained in the case of benzonorbornene (action of a mixture of HgO and mercuric acetate in water over 24 hours) :

+ Hg (O 2 CCH 3 ) , +H g O

and in the case of dicyclopentadiene (action of a mixture of HgO and HgCl2 in 50% aqueous acetone):

4- H g O + HgCi

In this case no addition occurs to the less strained five-membered ring. Bicyclo-(2,2,2)-octene (also less stressed than norbornene) gives on reaction with mercuric hydroxide tosylate in water a mixture of equal amounts of cis- and trans -adducts. The same products are obtained with mercuric acetate in aqueous acetone, whereas the strain-free cyclohexene yields only the product of trans -hydroxymercuration (see above). On the other hand, the action of mercuric acetate in acetic acid over a few minutes on bicyclo-(2,2,2)-octene results only in cis -addition of the elements of mercuric acetate to the double bond [198b],

In the case of dicyclopentadiene, additions have been carries at with mercuric acetate in water [181], alcohols [223] and in a 1:1


mixture of D2O and CD3OCD3. The product of the addition of mer -curic trifluoroacetate in methanol is unstable.

Below is given a list of aromatic hydrocarbons (and also some hydroaromatic hydrocarbons and halogenated derivatives of hydro-aromatic hydrocarbons), with a double bond in the side chain, for which additions of mercuric salts have been reported: styrene [7, 20, 30, 72, 141, 164, 167, 187, 199, 200], a-methylstyrene [30, 199], /3-methylstyrene [72], a-ethylstyrene [201], 2,6-dimethoxy-styrene [202], 1,1-diphenylethylene [37, 202], cas-stilbene [29, 72, 149, 204], trans-stilbene (only in the presence of catalysts such as BF3 [203], benzoyl peroxide and ascaridole [149, 203]), a-methyl-stilbene [29, 51, 69, 205], allylcyclopentane [147], allylbenzene [147, 206, 207], propenylbenzene [72, 200] (according to [72] only in alcohol, not in water), jo-isopropenylcumene [208], 2 -methy l - l -phenylprop-l-ene [69, 200, 209], 2- trans-allyldekalin [147] and dihydronaphthalene [164, 206].

According to [200], whereas in the methoxymercuration the HgX group enters only into the /5-position with respect to the phenyl in styrene and only into the a-position in 2-methyl-l-phenylpropene, the cis- and £rans-propenylbenzenes each give a mixture of the two positional isomers.

The addition of methanolic or ethanolic mercuric acetate to the endo - and exo -conformations of a chlorinated hexahydronaphthalene derivative occurs according to the scheme [210]:

+ Hg(O 2CCH 3 ) 2 + ROH

Cl

CH3CO2Hg.

In combination with an aromatic or alicyclic ring, the allyl group very often smoothly adds mercuric acetate while the propenyl group -CH=CH-CH3 is frequently incapable of adding mercuric salts and merely undergoes oxidation. However, this dif ference evidently re f e rs primari ly to aqueous (not alcoholic) solutions, since, for example, propenylbenzene, which does not enter into an addition reaction with mercuric acetate in water [147], does so readily in alcohol [72]. This different reactivity forms the basis of a method



of separating allyl and propenyl compounds in essential oils [211] and has also been applied to the determination of the structure of caryophyllenes [192].

Pinene (double bond in the ring) and nopinene (semicyclic double bond) behave differently with respect to mercuric acetate: while the former oxidizes (alcoholic mercuric acetate in the cold), the latter enters into addition and gives, after being set aside for 2 days with alcoholic mercuric acetate, an adduct according to the following scheme [212]:

(see also [213]). According to [11], the interactions of olefins and mercuric acetate

in glacial acetic acid afford compounds to which the authors gave the general formula

(where CnIl2n = ethylene, octene-2,3, duodecene-1,2, tetradecene-1,2, hexadecene-1,2). This method was used to obtain the compound C16H32-Hg(CH2ClCO2)2 by the interaction of hexadecene with a solu-tion of mercuric chloroacetate in chloroacetic acid[11]. Dissolution of mercuric palmitate and mercuric stearate in hexadecene gave Ci6H32-HgX2 (X=C18H35O2 or C16H33O2 [11]) compounds. All these compounds have the same structure RCOOCR R CR R HgOOCR.

Analogous products of the addition of X and HgX to double bonds, having the general formula XCnH27jHgX, were also made, for exam-ple, by the action of mercuric salts (acetate, propionate and also sulfate) on ethylenic hydrocarbons (ethylene, propylene, styrene) in the presence of anhydrous carboxylic acids [10], by the action of mercuric acetate on cyclohexene (in petroleum ether [66] and in t-butanol in the presence of boron trifluoride-diethyl ether [198b]) and on norbornene (in dioxan [28]), by the action of mercuric ace-tate, propionate and butyrate on styrene [20] (conditions not repor-ted [20]), by the action of the mercury salt of trinitromethane in

H 3 C - C - C H 3

OH

+

C " H ^ H g CH3CO" or C tI2 Hg (CH3CO2)2 CH3COO 2 2


water on ethylene, propylene, styrene, eyelopentene and cyclohexene (X = C(NO2)3) [159] and by the action of the mercury salt of 1,1,3,3-tetranitrobutane on ethylene (in water) [159a].

According to [215], the products of the addition of mercuric salts of dibasic acids to the double bond (in decene, cyclohexene and styrene) have a cyclic structure. For example, the compound

has been obtained from styrene and mercuric terephthalate after 5 minutes at 80-100°C; decene and cyclohexene required more prolonged heating.

Additions of the mercury salts of optically active carboxylic acids to olefins for the purpose of separating the isomers are described in [14, 15].

Mercuric salts have been added to olefins in the medium of amines: to ethylene in piperidine (as mentioned previously), mesidene [17] and pyridine [17], to allylamides in pyrrolidine [18], morpholine and 1-methylpiperidine [18] and to many aliphatic olefins, cyclohexene and styrene in methyl- and ethylanilines and even in aniline [12]. In contrast to the usual products of the addition of mercuric salts to the olefins in water and alcohols, the adducts obtained in amines are stable to acids and exhibit quasicomplex properties.

Products of the addition of mercuric salts to olefins containing an amino group in place of an alkoxy group have been obtained by the reactions of bis(ethoxyethylmercuri)acetylene and similar sub-stances with acid amides or imides [216] or benzenesulfonamides [217] on boiling in alcoholic solution. For example, substances of the structure (H2NCONHCH2CH2HgC)2, (CH3CONHC6H10HgC)2, etc., were made in this way. (The addition of mercury polychlorophen-oxides to ethylene has been mentioned previously in this chapter.) Apart from water, alcohols, acid anions and amines, aromatic hydrocarbons [21-25] and acetoacetic ester [26] proved to be suf-ficiently strong electron-donors to act as the second components in the addition of mercuric salts to alkenes. Such compounds, of the general formula ArCRiR2CR3R4HgX and CH3COCH(CR1R2CR3

R4HgX)COOC2H5, have been prepared [21-26] by the interaction of the mercuric salt-olefin adducts with aromatic compounds, e.g. anisole, in acetic acid in the presence of catalysts (oxo-acids) (olefins: ethylene [21], propylene, but-2-ene, cyclohexene, styrene [22]) and with acetoacetic ester (BF3lC2HsO catalyst) (olefins:ethy-lene [26, 26a], propylene, styrene [26]). In mostcases the resulting substances were not isolated but were decomposed in situ into /3-arylalkyl alcohols, acetates and a-(^-acetoalkyl)acetoacetates (see Chapter 14). ^-(p-MethoxyphenylJethylmercury iodide and acetate,



and ethyl a-(2-chloromercuriethyl)acetoacetate CH3COCH(CH2CH2

HgCl)COOC2H5 have been isolated.

Preparation of /3-(p-methoxypheny Dethy lmercury iodide [ 2 l ] . Thetransparentsolution of the product obtained from the addition of 64 g of mercuric acetate in 60 ml of CH3COOH to ethylene is st irred into a mixture of 100 g of anisole and 100 g of 98.6% H3PO4 at 22-23°C. After 1% hours, 400 ml of water are added and the resulting heavy oil mixed with a little water and 700 ml of 5% KI. A white precipitate forms (46 g) and is recrystal-l ized f ive times f rom alcohol; m.p. 146-148°C.

Preparation of a-(trans-"!)-2-methoxycyclopentylmercury chloride [ 179]. Asuspension of 89.4 g (0.28 mole ) of mercuric acetate in a solution of 20 ml (0.226 mole ) of cyclo-pentene in 400 ml of methanol is stirred at 25° C and becomes homogeneous after 2 minutes. The reaction comes to an end in 12 hours and the solution is then worked up with 78 ml (0.195 mole ) of 10% aqueous KI and f i l tered off f rom the yellow turbidity. The f i l trate is treated with an excess of 5% NaCl. The precipitate (yield: 64 g (88%); m.p. 76-77°C) recrystal l ized from 195 ml of ethanol has a melting-point of 83.3-83.7°C.

The corresponding bromide (m.p. 82-82.3°C) and iodide (m.p. 60.5-6l °C) are pre-pared in the same way.

Preparation of 2-acetorymercuricyclohexan-l-ol [34] , Cyclohexene (0.9 g), 3.5 g of mercuric acetate and 15 ml of water give, on mixing, a precipitate (after being set aside for 5 days) which is f i l tered off and recrystal l ized from ethyl acetate; yield: 100%; m.p. 112.2-113°C.

Preparation of l-acetoxy-2-acetoxymercuricyclohexane [66 ] , A suspension of 20 g (0.063 mole ) of mercuric acetate in 8 ml (0.08 mole ) of cyclohexene and 10 ml of petro-leum ether (b.p. 60-70°C) is st irred energetically for 7 hours at 35°C. The white precipi-tate which forms on the side of the flask is collected and washed with petroleum ether. The weight of the dry material is 23 g (yield: 91%); m.p. 86-89°C. The substance is un-stable and a strong odor of cyclohexane and acetic acid appears within 5 minutes.

In the presence of 0.003-0.006 mole of the boron trifluoride-diethyl ether complex, or nitric acid, the time of reaction is reduced to 1 hour, but the final properties of the products are unchanged. A slightly higher stability is found in l -acetoxy-2-chloro-mercuricyclohexane (m.p. 102-103°C after crystall ization from acetone), obtained by combining a methanolic solution of the acetate and aqueous NaCl, but it too decomposes slowly already at 25°C.

Preparation of 2-acetoxymercuri-3-hydroxytetrahydronaphthalene [ l 6 4 ] ,

CH2

Y ^ C H H g O 2 C C H 3

lVPvZ1CHOH CH2

An ethereal solution of 1,4-dihydronaphthalene is shaken for 24 hours with aqueous mercuric acetate. The resulting needle-like crystals are recrystal l ized from benzene or ligroine; m.p. 122°C.

Preparation of acetoxymercurimethylphenylcarbinol [30 ] • T o 3.27 g (0.31 mole ) of sty-rene are added a solution of IOg (0.031 mole) of mercuric acetate in 40 ml of water. After 24 hours the solution is f r ee from the mercuric ion (NaOH test) and the oily pro-duct is dissolved in the smallest possible volume of cold acetone and f i l tered. On being cooled with a mixture of salt and snow, the f i l trate gives a crystall ine precipitate; yield: 9 g (75%); m.p. 77-79°C after recrystall ization from benzene, (with decomposition).

The preparation of its salts with organic sulfur-containing compounds (mercaptides, xanthogenates, dialkylthiophosphates, etc. ) has been described [218],


The melting (decomposition) temperatures of some compounds CgH5CH(OR)CH2HgX where X are various anions and R is hydrogen, alkyl, or acyl are given in [20],

Preparation of chloromercurimethylbenzylearbinol [ 147 ] , A solution of 8 g of mercur i c acetate in 40 ml of water is added to 2.55 g (0.025 mo le ) of al lylbenzene (b.p. 155.5-156°C/738.5 mm; no201.5171). An oi ly organomercury product begins to precipi tate a f ter 1)^-2 hours. A f t e r a total reaction t ime of 12 hours the alkali test shows that the addition is complete. The separated oil, d issolved in hot water and treated with a solution of 1.8 g of KCl1 g ives 8.4 g (90%) of the required product in the f o rm of a white precipitate. R e -crystal l izat ion f r o m aqueous ethanol g ives silky needles, m.p. 75°C.

Preparation of 1,1, l-trifluoro-3-ethoxyprop-2-ylmereury nitrate [172], 1 ,1 ,1 -Tr i f luoro -propylene (1.5 l i t e rs ) is passed, at room temperature and with vigorous st irr ing, into a three-necked f lask containing 30 ml of ethanol and 17 g of Hg (NO 3 ) 2 .0 .5H 2 0. Al l the nitrate dissolves within an hour and the solution contains no mercury ion. A precipitate appears when the solution is set aside, which is f i l t e red off on the fol lowing day. The mother liquor is evaporated to dryness under vacuum. The total yield of 1,1,1-tr i f luoro-3-ethoxyprop-2-y lmercury nitrate is 85%. The substance is infusible. The corresponding chloride melts at 37-38°C ( from aqueous alcohol).

Preparation of bis-perfluoroisopropylmereury [175 ] , HgF 2 (240 g, 1.01 mole) , 70 g of anhydrous HF and 300 g (2 mo l es ) of hexafluoropropylene a re heated in a stainless steel bomb fo r 12 hours at 110°C. The bomb is then cooled and opened and the product trans-f e r r e d to a loosely stoppered polythene bottle to evaporate off the excess of hydrogen f luoride. The last traces of HF are removed by mixing the product with NaF powder; alternatively, the HF can be extracted with water and the product dried over P 2 O 5 . Disti l lation g ives 323 g (66%) of b is -per f luoro isopropy lmercury ; b.p. 115-116°C; m.p. 20-21°C; n D s 1.3244; d42S 2.5302. The mater ia l must be dr ied be fore the distillation, as otherwise it f o rms an azeotrope (b.p. 90°C) containing approximately 4.3% of water.

If the starting mercuric fluoride contains an admixture of chloride, perfluoroisopropylmercury chloride (b.p. 173-178°C) forms as a side product; this is obtained from bis-perfluoroiso-propylmercury by the action of thiophosgene.

Analogous conditions were used in order to obtain [175] bis-(3-H-l-trifluoromethylpentafluoropropyl)mercury (b.p. 172.3-173°C; yield: 73%; setting-point 0°C), bis-(3-chloro-l-trif luoromethyl-pentafluoropropyl)mercury (yield: 5%; b.p. 85-93°C/20 mm; m.p. -10°C) and bis-l,l-dichloro-2,2,2-trifluoroethylmercury (yield: 69%; m.p. 180-185°C). bis-Perfluoro-t-butylmercury was simil-arly made from HgF2 in anhydrous HF and a mixture of gases containing 17.3% of perfluoroisobutene, 76.4% of perfluorocyclo-butane and 6% of perfluoromethylcyclobutane, heated in a bomb for 12 hours at 200°C. Yield: 33%; m.p. 65-66°C [175].

Synthesis of bis-(l,2,2,2-tetrafluoroethyl)mercury [173 ] . HF 2 (23.9 g, 0.10 mole ) , 25 g (0.30 mo l e ) of tri f luoroethylene and 15 ml of AsF 3 are heated f o r 4 hours at 50°C in a closed stainless steel tube, with continuous shaking. A f t e r evaporation of AsF 3 under vacuum, the solid residue is sublimed at 80-90°C under atmospheric pressure. The sublimate weighs 26.6 g (66% on the H g F 2 ) and melts at 78-79°C.



Quantitative determination of double bonds in organic compounds, based on the addition reaction with mercuric salts, has been des-cribed [187, 219-224].

The formation (under pressure) of liquid complexes of propylene and 1- and 2-butenes with mercuric acetate and of propylene with mercuric acetate, is reported in [225]; these substances are not products of addition of the mercuric salts to the double bond.

A d d i t i o n o f m e r c u r i c s a l t s t o d i e n e s . Aliphatic hydrocarbons con-taining two double bonds in the molecule are also capable of adding mercuric acetate. Thus, biallyl reacted with aqueous mercuric acetate gives (after subsequent treatment with KCl solution) the cyclic compound [146] (see [226]):

CH2 CH2 I I

ClHgCH2CH CHCH2HgCl

x O 7

An analogous cyclic product has been obtained f rom diallyl and the mercury salt of trinitromethane [227],

In contrast to Sand's data [48], the conjugated hydrocarbons (buta-l,3-diene [147], isoprene, piperylene and bipropenyl [147]) also give adducts 2HgOHX with mercuric acetate, even in aqueous media. However, it must be noted that the hydrocarbons with terminal CH2 groups (diallyl [146], butadiene, isoprene) react faster and give much better yields of the product than dipropenyl, f o r example (in the latter case the yield of organomercuries is only 13% and an appreciable amount of a mercurous salt is formed). This observation must be correlated with the dif fering degrees of reactivity of allyl and propenyl groups bound to aromatic or ali-cycl ic systems with respect to the addition of mercuric salts (see above).

Buta-l,3-diene and methanolic or ethanolic mercuric acetate give the meso and racemic forms of 2,3-dialkoxy-l,4-diacetoxy-mercuributanes [148, 149, 167, 228].

According to the results of McNelly and Wright [71], butadiene does not give a product of 1,4-addition. The action of mercuric nitrate in aqueous ethylene glycol on buta-l,3-diene give (after KI treatment) 2,3-bis-(iodomercurimethyl)-l,4-dioxan; replacement of the HgX group in this compound by iodine allowed the separation of the corresponding cis- and trans-iodomethyl derivatives of dioxane [229].

Under the action of mercuric salts in various hydroxylic solvents, butadiene, isoprene and hexa-l,5-diene add HgX and OR to each double bond [167]. Methanolic mercuric acetate adds also to vinyl-cyclohex- l -ene [167],

In the case of l-phenylbuta-l,3-diene, both the product of addition to one of the double bonds (action of I M mercuric acetate) and the


product of addition to two double bonds (action of 2M HgX2 or of mercuric acetate on the monomercurated product [72]) have been isolated.

Synthesis of chloromercuri me thoxypheny lbutene [ 7 2 ] . Freshly dist i l led phenylbuta-diene (1.59 g, 0.012 mo le ) is added to a solution of 3.18 g (0.01 mo l e ) of mercur i c acetate in 25 ml of methanol. A f t e r 5 minutes a withdrawn sample g ives no precipi tate of m e r -curic oxide with 10% NaOH. Four hours later the mercurous salts are f i l t e red off and the f i l t rate subjected to a slow addition of 10% aqueous NaCl . The separating oil sol id i f ies rapidly and is f i l t e red off and washed successively with water and 2 portions of pe t ro -leum ether. The yie ld of product melt ing at 89°C is 3.35 g (85%). A f t e r recrysta l l i zat ion f r om 25 ml of ethanol the melt ing-point is 92° C.

Synthesis of diacetoxymercuridimethoxybutane L72]- Fhenylbutadiene (1.43 g, 0.011 mole ; b.p. 86°C/11 m m ) is added to a solution of 6.36 g (0.02 mo le ) of mercur i c acetate in 55 ml of methanol. No mercury ion can be detected in the system af ter 2 hours (test with 10% aqueous NaOH). A f t e r 12 hours 40 ml of methanol are dist i l led out and the residue is f i l t e red and cooled to 10°C. The yie ld of the crysta l l ine product is 7.62 g (35%); m.p. 142-145°C. Crystal l izat ion f r om a mixture of 25 ml of benzene and 35 ml of petro-leum ether (b.p. 60-70°C) increases the melting-point to 149°C with only small loss of the product.

Preparation of 2-methyl-l ,4-dichIoromercuri-2,3-dihydroxybutane [ 147 ] , Isoprene (1.7 g, 0.025 mo l e ) is treated with a solution of 15 g of mercur ic acetate in 80 ml of water. The addition is complete within a few minutes. Some of the hydrocarbon poly-mer i z e s on the walls of the vesse l ; 3 g of KCl in 40 ml of water are added to the addition product. A dir ty-white precipitate appears and a test with ammonia shows the presence of mercurous salts. The precipitate is worked up with 10% alkali and the f i l t rate treated with 10% acetic acid to a neutral reaction. 8.3 g (58%) of 2 -methy l - l , 4 -d i ch lo romercur i -2,3-dihydroxybutane precipitate out; m.p. 147-148°C af ter two recrysta l l i zat ions f r om ethyl acetate.

Preparation of 2,3-di(iodomercurimethyl)-l,4-dioxan [229].

IHgCH 2 CH CHCH 2 Hg I

\ / CH 2 —CH 2

A solution of 243 g (1.12 mo les ) of HgO in 300 ml (4.7 mo l es ) of conc. HNO3 (sp. g r . 1.42) and 150 ml of water are combined with 100 ml of water and 500 ml of f resh ly disti l led ethylene g lycol and the whole mixture maintained at 20°C. Buta-1,3-diene is then passed in at a rate of 2 bubbles/second f o r 3 hours (absence of mercur i c ion, test with NaOH). The mixture is cooled to -5 °C and the precipitate of 2 ,3-d i (n i t romercur i -methy l ) - l ,4-d ioxan f i l tered off and dissolved in 2 l i ters of 1% NaOH (slight l iberation of mercury ) . Addition of 133 g (0.801 mo l e ) of KI in 500 ml of water g ives 276 g (0.359 mo le ) of the required product, m.p. 196-198°C.

It has been shown that the products of the interaction of allene with mercuric chloride C 6 H 8 H g a n d of the interaction of mer-curic chloride with allylene have the same composition [97, 230]. Mercury salts do not add to l,2-dimethylcyclohexa-l,4-diene [231].

The addition of mercuric salts to bicycloheptadiene occurs by the mechanism of conjugated 1,5-addition with the formation of nortricyclene derivatives



[R =OCCH 3 in the addition of HgCl2 in glacial acetic acid [232], R = CH in the addition of HgCl2 in methanol (3 days at room tem-perature [233]), R = C2H5 in ethanol (as above, followed by boiling [233])]. However, according to patent [214], the addition of mercu-r ic chloride in warm ethanol (60°C) to bicyclo- (2, l , l ) -hepta-2,5-difene gives an 83% yield of 2-ethoxybicyclo-(2,2,1)-hept-3-enmer-cury chloride. Again according to [214], the same method can be used to obtain diethoxybicyclo-(2,2,l)-heptane-bis-mercury chlo-ride and dimethoxybicyclo-(2,2,l)-heptane-bis-mercury chloride.

Preparation of l-chloromercuri-5-methoxynortricyclene [233]. Bicyclo-(2,2,1)-hep ta-2,5-diene (12 g ) is added to a solution of 35 g of mercuric chloride in 300 ml of acetone-f ree methanol and the mixture covered and set aside for 3 days. The resulting voluminous precipitate is f i l tered off, washed with cold methanol and dried in a desiccator over P 2 O 5 ; yield: 14 g. Recrystallization from methanol gives 5.5 g of colorless acicular crystals, m.p. 121-121.5°C.

There are some indications that intermediate formation of the addition products of mercury salts may occur in the reaction of cyclo-octatetraene with mercuric salts [234].

A description has been given of isolations of olefins and diolefins f rom hydrocarbon mixtures on the basis of different rates of their addition reactions with mercuric salts [235].

The addition to cyclopentadiene has been mentioned above.

A d d i t i o n o f M e r c u r i c S a l t s t o H y d r o x y C o m p o u n d s C o n t a i n i n g a n E t h y l e n i c B o n d

A d d i t i o n t o h y d r o x y c o m p o u n d s a n d e t h e r s . The additions of mercuric salts to unsaturated alcohols and to aromatic hydroxy compounds and their derivatives containing an unsaturated side chain occur as readily as the additions to the olefinic hydrocarbons.

Allyl alcohol gives two types of products with mercuric salts: propylene glycol derivatives HOCH2CHOHCH2HgX and dipropylene oxide derivatives [3-6, 141, 145, 167, 236, 448, 449]

XHgCH2CH-CH2O I I

OCH2—CHCH2HgX The former compounds are obtained by the action of allyl alcohol

on a solution of mercuric nitrate with immediate neutralization of the acid formed with additions of alkali [4], The mercury deriva-tives of dipropylene oxide, on the other hand, are obtained f rom acid solutions of mercuric salts [236], They have a trans-structure and are polymeric in character [237].

The interactions of mercuric halides with allyl alcohol are re -ported in [3, 226, 236] and the mechanism of the formation of allene derivatives during the action of mercuric salts on allyl alcohol in [3, 236].


A propylene glycol derivative is also formed in the addition of the mercury salt of trinitromethane to allyl alcohol [238]; in the presence of an excess of the alcohol (in water), the product is the symmetric compound Hg[CH2CHC(N02)3CH20H]2.

Shaking of mercuric acetate with allyl alcohol leads to an addition reaction ending in the formation of acetoxymercuripropylene glycol monoacetate CH2(HgOCOCH3)CH(OCOCH3)CH2OH [169].

Preparation of bromomercuripropylene g lyco l [ 4 ] . Dilute aqueous KOH is added to a solution of 100 g of ye l low mercur i c oxide in 20% HNO3 until the precipitate of the basic salt no longer red isso lves . Al ly l alcohol is added drop by drop, with st i r r ing and with occasional cool ing of the reacting system with water, to ful l dissolution of the precipitate; this is fo l lowed by KOH, again to the appearance of an insoluble precipitate, which is once more redissolved with al lyl alcohol. These operations are repeated ti l l the p r e c i -pitate suddenly darkens and the liquid becomes alkaline. The solution is then treated with KBr (1 atom of bromine per atom of mercury ) and set aside f o r 24 hours. The required bromide is salted out by a stream of CO 2 ; m.p. 84-86°C, decomposition at I l O c C .

Preparation of dipropylene-oxide-dimercurv sulfate [236].

SO4

H g - C H 2 - C H - C H 2 - O I I O — C H 2 - C H - C H 2 - H g

A f i l tered solution of 75 g of HgO in a 1:1 mixture of 30 ml of water and 180 ml of dil. H2SO4 is s t i r red with 30 ml of a l ly l alcohol. The sulfate separating out af ter 2-4 hours is f i l t e red off, washed with cold water and dried. Y ie ld : 60 g. The same method can be used to prepare the nitrate, replacing the sulfuric acid by 40% HNO3. The halide salts are ob-tained by adding KCl to the nitrate and UsingCO 2 as the salting-out agent; the melt ing-point of the bromide is 251°C. These substances appear to be polymeric [237],

On reaction with the mercury salt of trinitromethane, but-l-en-4-ol forms a product of the addition of elements of this salt to the double bond; with an excess of the unsaturated compound (in alcohol), this product gives symmetric Hg[CH2CHC(NO2)SCH2OHj2[238].

Pent-l-en-5-ol [146], hex-l-en-5-ol [416], 1,1,5,5-tetramethyl-pent-l-enol [49] and 5-methylpent-l-en-5-ol [49] add both mercuric acetate and mercuric chloride in aqueous media. Pent-l-en-5-ol adds also the mercury salt of trinitromethane [238], giving rise to cyclic compounds such as

CH2—CH2

I I C H 2 = C H — C H 2 - C H 2 - C H 2 - O H + HgCl2 ClHgCH2CH CH2 + HCl

V Preparation of 2-chloromercurimethyltetrahydrofuran [ 146 ] . P e n t - l - e n - 5 - o l (4.3 g,

0.05 mole ; b.p. 136-138°C) is added to a solution of 16 g ot mercur ic acetate in 50 ml of water. The react ion proceeds ve ry rapidly and an oi ly organomercury product collects at the bottom, redissolv ing on the addition of water . Treatment with a solution of KCl results in the separation of oily 2-chloromercurimethyltetrahydrofuran. The oil is dissolved in ether and the solution dried over fused sodium sulfate. Evaporation of the ether g ives 12.8 g (yield: 82%) of the required product in the f o rm of an oil.



Pen-l-en-5-ol acetate and the mercury salt of trinitromethane give the acyclic product (No2)3CHgcH2CHC(NO2)SCH2CH2CH2OCOCH3

in water and, in dry nitromethane [238], the symmetric compound Hg[C H2 C HC (NO2)3C H2C H2C H2OH]2.

With a mercuric salt in water, 2,6-dimethylhept-5-en-2-ol [7, 49, 239] forms both a cyclic product and an open-chain adduct [239]. The addition of mercuric acetate in lower alcohols to higher alcohols containing double bonds has been described [240],

Methoxymercuration of the monomethyl ether of vinylethylene glycol gives the normal product XHgCH2CH(OCH3)CH(OH)CH2 (OCH3) in a yield of 31% [241],

Vinylglucose [242] and allylacetorhamnose [243] heated moder-ately with mercuric acetate in acetic acid for several hours give products of the addition of -OCOCH3 and -HgOCOCH3 to the double bond.

The additions of mercuric acetate to allyl-a-mannitol (in water or in dioxan) result in elimination of water and in the formation of a mixture of isomers containing the dioxane ring [244].

Data concerning the additions of mercuric salts to o-allyl ethers of d-mannitol, sorbitol and other polyhydric alcohols will be found in [245-248].

3-Allyl-l,2,5,6-di-isopropylidene-af-mannitol worked up with mercuric acetate under anhydrous conditions [249] gives, in addi-tion to the main product RHgOCOCH3: 2-acetoxymercurimethyl-4,6-bis-(2,2-dimethyl-l,3-dioxolan-4-yl-p-dioxan) ([II); about 1% of the symmetric product R2Hg: bis-[5,6-bis-(2,3-dimethyl-l,3-dioxolan-4-yl-2-p-dioxanylmethyl)]mercury ( I V ) [249]:

H H H I I I

H—C—O CH3 H—C—O CH3 H3C O - C - H

I X C / I \ r / \ C / I I / \ I / \ / \ I

H—C—O CH3 H—C—O CH3 CH3 O - C - H I I I

H - C - O - C H 2 H - C - O - C H 2 H 2 C - O - C - H I I ! I I I

H-C-O-CHCH 2 HgO 2 CCH 3 H - C - O - C H C H 2 H g C H 2 HC-O—C—H I I I

H—C—O CH3 H - C - O CH3 H3C O—C—H

I \ r / I \ r / \ r / I I / \ I / \ / \ I

H—C—O CH3 H—C—O CH3 H3C O—C—H

H H H I I I I V

The addition of mercuric acetate in methyl alcohol to D-glucal and its 3,4,6-triacetate gives respectively methyl-2-acetoxymer-curi-2-desoxy-/3-D-mannoside (cis) ( V ) and methyl-2-acetoxy-mercuri-2-desoxy-3,4,6-tri-o-acetyl-/3-D-glucoside (trans) ( V I )


[250], The addition to the 3,4,6-triacetate has also been carried out in ethanol and methanol (configuration not established) [250].

AcO

H g ( O A c ) 2

CH3OH

H g ( O A c )

CH3OH

A c O

H 2 O H

O s

C H 2 O A e

O C H 3

. O H A c O H g

v 1 Y h y H H

O C H 1

VI H

In the methoxymercuration of cyclohex-3-en-l-ol and its methyl ether and acetate, only one product was isolated in each case out of the possible four isomers [251]; in these isolated products the OCH3- and -HgOCOH 3 groups were trans to the starting OH-group (or its derivatives).

The hydroxyl group present in the unsaturated compound exerts a directing effect on the stereochemistry of the addition of HgX and OR to the double bond [252]. The structure of the final product is determined by the formation of a ring as a result of the partici-pation of the correspondingly positioned alcohol group. This is the case, for example, in carbinol (VII) [252]:

H O C H 2

VII

or trans-hex-3-en-l-ol:

H e X g * 2

ROH

XHg.

O- - C H 2

OH XHg

Hex, ROH / \ y >

H5C2 O

Other examples of such directing effects of substituents have also been described [250, 251]. In the cases of 4-substituted cyclohexenes (the substituents were OH and OCH3) and cis -hex-3-en- l -o l , the

Referciiccs sec page 212

126 188 ORGANOMERCURY COMPOUNDS

substituent merely favors stereospecific addition of XHg and OR' to the double bond, but no cyclization takes place, for example [252]:

OR HgAc11

R'OH

ClHg Kci \ Q /

R'O

OR

OH ClHg OH / X / HgAc11 KCl

R'OH X R'O C2H5

Preparation of 3-chloromereuricyclohexan-l,4-diol [252], A solution of 5 g of cyclo-

hex-3-enol and 15 g of mercuric acetate in 150 ml of water is shaken for 10 days at room temperature; 3 g of NaCl are then added, the solution evaporated to dryness under vacuum and the product extracted from the residue with ether. Yield: 16.5 g (94%). Crystallization from benzene. The substance decomposes above 150°C.

a-Terpineol [7, 49] adds mercuric salts under the usual condi-tions, and, by intramolecular anhydrization, forms an organomer-cury derivative of cineole and two products - organomercury derivatives of terpine; according to [253], the latter are not di-astereomers but polymorphic forms of one and the same compound (for the structure of this compound see also [252]).

Mercuric salts have been added in the usual manner to cinnamyl alcohol [254, 265], o, o'-dimethoxystyrene [202], and a , / 3 - d i a l l y l -CL -mesityl-/3 ,/3 -dimethylethanol [ 207].

In an aqueous medium, the propenyl group in unsaturated aromatic alcohols and phenols and their derivatives does not add mercuric salts; the corresponding compounds with the allyl group do give addition products. Thus, addition products are obtained from safrole [141-143, 211, 255, 256], methylchavicol [143, 211, 255], eugenol [141, 143, 257, 258] and its ethers [141, 143], apiole [143] and myristicin [211, 255], but not from isosafrole [143, 211], anethole [211], isoeugenol [143], isoapiole [143], isomyristicin [143, 211] and asarone [143, 255]. It is possible that the latter also would add mercury salts in alcoholic media.

The addition of mercuric salts to o-allylphenol [45] (in water) and to its homologs and derivatives [46, 260] is accompanied by ring closure and the formation of the organomercury derivatives of l-methyl-l,2-dihydrobenzofuran:

CH2CH=CH2 CH2CHCH2HgX

+ Hgx2 i n S X , . O CH2HgX

OH OH


The same ring closure occurs during the action of mercuric salts on 2- and 4-allylresorcinols [50] and on o-allyl-p-t-butyl-phenol [261].

In the same way, 2,2-diphenylpent-4-en-l-ol gives the corres-ponding tetrahydrofuran derivative on prolonged standing with methanolic mercuric acetate [197].

Preparation of l-chloromercurimethyl-l,2-dihydrobenzofuran [ 4 5 ] , A suspension of 25 g of o-a l ly lphenol in a solution of 52.5 g of HgCl 2 in 1 l i ter of water g ives , on st irr ing f o r 3 hours, a white precipitate which a f ter recrysta l l i zat ion f r om alcohol weighs 66.5 g; m.p. 137° C.

Preparation of 1-acetoxymercurimethyl-l ,2-dihydrohenzofuran [ 4 5 ] , A solution of 23.7 g of mercur i c acetate in 100 ml of water is slowly s t i r red into a suspension of 10 g of o-al ly lphenol in 100 ml of water. A heavy grayish oil separates out a f te r the mixture has been s t i r red f o r 30 minutes. The aqueous solution decanted f r o m this oil y ie lds crysta ls on the fol lowing day. The oi l so l id i f ies in the course of the next few days and is then mixed with the above crysta ls and recrys ta l l i zed f r om water or alcohol; m.p. 80-81°C; yield: 100% (see " in t roduc t i on " to this chapter).

The action of HgO in 80% acetic acid on the allyl ethers Ol phenol and /3-naphthol results in nuclear mercuration without involvement of the double bond [262]; see also Chapter 5.

A method has been suggested [263] for the separation of vinyl and ethyl derivatives of quinine alkaloids based on the former 's ability to form addition products with mercuric salts.

The addition of mercuric acetate or nitrate to diallyl ether in an aqueous medium with subsequent KCl treatment leads to 2,6-dichloromercurimethyldioxan [146, 167]

CH2 CH2 CH2 CH2

I l icci I I CH2 = CH CH = CH2 + HgX2 + H2O —L ClHgCH2-CH CH - CH2HgCl

\ 0 /

which is a mixture of cis- and frms-isomers [264] with a pre-dominance of the former [55].

Similar ring closure with the formation of a dioxan mercury derivative occurs during the addition of mercuric acetate in water to the monoallyl ether of glycerol [244, 245] and ethylene glycol[244].

Mercuric salts add under the usual conditions to allyl acetate [187] and the cinnamic ester of p-nitrobenzoic acid [265],

Mercuric oxide has been added in water to the double bond of the allyl group in p-phenolsulfonic acid salt of l-allyl-4-diethyl-aminoethoxy-5-methoxybenzene, in substituted p-allyloxybenzoic acid, and its ester, and in p-allyloxybenzenesulfonic acid [258]; mercuric acetate has been added in water to allyloxybenzoic acid and its esters [266] and to allylsulfonamide [259].



A d d i t i o n t o t h e t h i o a n a l o g s o f h y d r o x y c o m p o u n d s . Diallyl sulfide forms with mercuric acetate in aqueous solution a cyclic product [167, 266 a] and with mercuric chloride one having an acyclic structure [267]:

(CH2 = C H - C H 2 — ) 2 S

/ V y . CH 3 CO 2 HgCH 2 u CH 2 HgO 2 CCH 3

(C IHgCH 2 CH (OH)CH2J2 S

Synthesis of 2,6-di-(acetoxvmercurimethyl)-l,4-thioxan [266a], Diallyl sulfide (0.251 mole ) is rapidly added to a st irred solution of 0.5 mole of mercuric acetate in 500 ml of water. After 29 hours the reaction for mercury ion proves to be negative. The precipita-tion is f i l tered off and dried to constant weight. Yield: 81.6 g; m.p. 166-182°C (with decomposition), rising to 197-199°C (still with decomposition) after several recrystal-lizations from acetone. Treatment of the f i ltrate with KI gives the di- iodomercuri derivative. The weight after drying is 62.6 g. Total yield: 82%.

The addition of mercuric acetate in water to diallyl sulfone results in the corresponding cyclic sulfone [266a].

Dimethallyl sulfide adds mercuric acetate in water to form 2,6-dimethyl-2,6-bis-(acetoxymercuri)- j>-oxathian [266a]:

[ C H 2 = C (CH 3 ) CH 2 ] a S + Hg (O2CCH3 )2 + H 2 O — L H3C / x I c h ^

\l 1

A 0 A 1

I/ Nl I H g ° H g I

A d d i t i o n t o v i n y l e t h e r s a n d e s t e r s . Nesmeyanov, Lutsenko and Vereshchagina [124] have found that the action of mercuric acetate in an aqueous medium on vinyl ethers (vinyl ethyl, vinyl butyl, vinyl isoamyl and divinyl) results in the usual addition to the double bond, the orientation obeying Markovnikov's rule. The molecule then eliminates the elements of alcohol and forms a solution of acetoxymercuriacetaldehyde. Precipitation with chlo-ride or bromide readily affords solid chloromercuri- or bromo-mercuri acetaldehyde:

C H 2 = C H - O R - I - H g A c 2

O R

+ H 2 O AcHgCH 2 — CH / A c H g C H 2 C H O Cl HgCH 2 CHO

O H

In the same way, isopropenyl n-butyl ether gave the simplest mercurated ketone - chloromercuriacetone [124],


Vinyl ethyl ether adds the mercury salt of trinitromethane in the same way as mercuric acetate [227].

Preparation of chloromercuriacetaldehyde [124]. With strong shaking, 10 g (0.1 mo le ) of vinyl butyl ether are gradually added to a f i l t e red solution of 32 g (0.1 mo l e ) of m e r -curic acetate in 150 ml of water. The addition occurs rapidly, with slight evolution of heat. The resulting solution, f r eed f rom traces of mercury , is treated with a solution of 7.5 g (0.1 mo le ) of KCl in the least possible amount of water. White crysta ls appear at once. Y ie ld : 24 g (85%); m.p. 130-131°C ( f rom hot water) .

Preparation of chloromercuri acetone [124 ] , Isopropenyl n-butyl ether (1.2 g, 0.01 mo l e ) is added to a solution of 3.2 g of mercur ic acetate in 15 ml of water. The ether dissolves rapidly with slight evolution of heat. The small amounts of mercurous salts are f i l t e red of f . On addition of 0.75 g of KCl in 3 ml of water, the solution becomes turbid and we l l - f o rmed crystals begin to precipitate a f ter 2-3 minutes. A f t e r 15 minutes, the solid mater ia l is f i l tered off and washed with cold water. Y ie ld: 1.7 g (58%); m.p. 104°C ( f rom methanol).

Brief boiling of /3 -phenylvinyl ethyl ether with mercuric chlo-ride and mercuric oxide in aqueous acetone resulted in an 88% yield of chloromercuriphenylacetaldehyde [268]:

2C,H5CH = CHOC2H5 + HgCl2 + HgO + H2O-* 2C«H5CHCHO + 2C2H5OH

HgCl

/3-Phenylvinyl ethyl ether boiled for 2 hours with an excess of aqueous mercuric acetate gave a mixture of insoluble mercury-containing polymeric substances [102, 268], appearing [268] to be the products of oxidation and mercuration of the initially formed monomercurated phenyl acetaldehyde. a-Phenylvinyl ethyl ether (and also a-acetoxystyrene) reacts smoothly with aqueous mercu-ric acetate to give &j-acetoxymercuriacetophenone [268]:

CH2 = CC6H5 + (CH3COO)2 Hg -f H2O C6HsCOCH2HgOCOCH3 I OC2H5

+ CH3COOH + C2H5OH

Preparation of chloromercuri phenyl acetaldehyde [268]. A solution of 1.35 g (0.005 mo l e ) of HgCl 2 in 8 ml of acetone is added to a mixture of 1.5 g (0.01 mo l e ) of /3-phenyl-vinyl ethyl ether, 1.1 g (0.005 mo le ) of HgO, 5 ml of acetone and 1 ml of water. The entire mixture is brought to the boil and then quickly f i l t e red and cooled. Evaporation of some of the acetone results in crysta ls of the required product, which are washed with a l itt le cold acetone and absolute ether. Y ie ld : 3.2 g (88%); m.p. 121-123°C.

Halogenomercurated oxo-compounds have also been obtained [127] by the addition of mercuric salts in water, at room temper-ature, to the enol acetates of oxo-compounds (with subsequent addition of halide ions):

RCH = CHOCOCH3 + Hg (OCOCH3)2 + H2O -^L ClHgCHRCHO + 2CH3COOH



Vinyl acetate gave a quantitative yield of chloromercuriacetalde-hyde [127], /3-methyl- and /3-ethylvinyl acetates the corresponding chloromercurialkyl aldehydes [269], isopropenyl acetate chloro-mercuriacetone and cyclopentyl acetate o-chloromercuricyclo-pentanone (in yields of 70-85%) [127].

Preparation of chloromercuriacetaldehyde from vinyl acetate [127] , With strong shaking, 4.3 g (0.05 mole) of freshly distilled vinyl acetate (b.p. 72-74°C) are gradually added to a solution of 16 g (0.05 mole ) of mercuric acetate in 75 ml of water. Addition takes place rapidly, with slight evolution of heat. The solution, freed from traces of mercurous salts, is treated with 3.8 g (0.005 mole ) of KCl in 10 ml of water. White crystals appear at once (quantitative yield) and are recrystal l ized from water; m.p. 129-130°C (with decomposition).

The additions of mercuric salts to vinyl and allyl acetates are described in [187].

The addition reaction of mercuric acetate with double bonds has been utilized [270] for a qualitative analysis of mixtures of vinyl acetate and vinylalkyl esters of dicarboxylic acids by paper chro-matography.

The addition of mercuric salts to vinyl ethers and esters in an alcoholic medium and in the presence of HgO (which combines the liberated acetic acid) can be used as a method of synthesizing acetals of mercurated acetaldehyde [128]:

2CH2 = CHOR + (CH3CO2)2Hg + HgO + 2ROH -* 2CH3COOHgCI I2CH(OR)2

+ H2O % ClHgCH2CH(OR)2

Preparation of the diethyl acetal of chloromercuriacetaldehyde from vinyl ethyl ether [ 128]. With cooling, 7.5 g (0.1 mole) of vinylethyl ether are stirred into a mixture of 15.9 g (0.05 mole ) of mercuric acetate and 20 ml of absolute ethanol. At the end of the addition 10.8 g (0.05 mole ) of dry yellow mercuric oxide are added in 1-g portions to the system, waiting until each portion dissolves before adding the next one. The reaction mixture is then poured into 7.8 g (0.1 mole ) of KCl in 60 ml of water. The resulting heavy oil is separated off, dissolved in 100 ml of dry diethyl ether and dried over CaCl2 . A f ter filtration, the ether and alcohol are evaporated off under vacuum and the residue dried in a vacuum desiccator over P2O5. This procedure gives 26 g (yield: 73%) of the required product in the form of colorless heavy oil.

The interaction of mercuric oxide in the presence of mercuric acetate in aqueous alcohol with vinyl alkyl ethers leads directly to excellent yields of mercuri-bis-acetaldehyde; in the case of the a-substituted vinyl alkyl ethers, the products are mercuri-bis-ketones [271]:

CH3COOHgOH + C H 2 = CR'OR-» [HOHgCH2CR'(OR)OCOCH3] D ' CjH2=UrlUK

-H- Hg (CH2CR'0)a + ROH + CH3COOH

R' = H or Alk. When this reaction was carried out with vinyl ethyl ether in


absolute alcohol, the product was the hemiacetal of mercuri-bis-acetaldehyde [128]:

OCaHg /

(C2H6O)1 CHCH2HgCH2CH \

OH

Preparation of mercuri-bis-acetaldehyde [ 2 7 l ] . With shaking, 6 g of vinyl butyl ether are added in drops to a mixture of 5.4 g of yel low mercur i c oxide, 0.2 g of mercur ic acetate, 1 ml of water and 2 ml of alcohol. The HgO dissolves with evolution of heat. The reaction mixture is f i l t e red f r e e f r om traces of metal l ic mercury while st i l l warm. Strong cooling of the f i l t rate results in precipitation of crystals , which are separated off, washed with cold alcohol and ether and dried in a vacuum desiccator over P2 O 5 . Y ie ld : 6 g (86%); m.p. 93-95°C ( f rom alcohol).

Mercuri-bis-acetaldehyde has been obtained in the same way from vinyl ethyl, vinyl isopropyl and vinyl phenyl ethers, in yields of 87, 90 and 81%, respectively.

Preparation of diacetonylmercury [271]. With shaking, 3.3 g of isopropenyl ethyl ether are added in drops to a mixture of 2.7 g of yel low mercur ic oxide, 0.1 g of m e r -curic acetate, 3 ml of alcohol and 0.5 ml of water. A f t e r dissolution of the HgO, the reac-tion mixture is f i l t e red f r e e f r om traces of metal l ic mercury and the f i l t rate evaporated in vacuum. The y ie ld of diacetonylmercury is 3.8 g (98%); m.p. 68°C ( f rom benzene).

Mercuri-bis-acetaldehyde has been made by the action of HgO in the presence of mercuric acetate on the divinyl acetals of various aldehydes [272]:

OCH = CH1 / Hg (OCOCH1),

RCH + HgO • RCHO + Hg (CHjCHO), \

OCH = CH2

Preparation of mercuri-bis-acetaldehyde [272 ] , With st irr ing, 14.2 g of divinylbutyral are added in drops to a mixture of 21.6 g of yel low mercur i c oxide, 0.8 g of mercur ic acetate, 4 ml of water and 8 ml of alcohol. The mercur ic oxide dissolves with evolution of heat. The mixture is f i l t e red while sti l l warm and the f i l trate cooled with ice water. The resulting crysta ls are separated off and washed with cold alcohol and ether. Y ie ld : 24.8 g (85%); m.p. 93-94°C.

Mercuri-bis-acetaldehyde can also be prepared [273] by the action of arylmercury hydroxide on vinyl ethers, with intermediate formation of an asymmetric organomercury compound

OR

ArHgOH + CH2 = CHOR ArHgCHzCH \

OCH3



which later decomposes:

OR / OR x / ( / \

2ArHgCH2CH Ar2Hg + Hg CH2CH

^OCHa V xOCH3/ 2

(see Chapters 7 and 8). The elements of mercuric salts will also add to the double bond

in vinyl ethers without any participation of the solvent if the reaction is carried out in ether [274].

Preparation of acetoxymercuriacetaldehyde monoethyl acetal acetate [274]. Absolute ether (10 ml ) is added to 3.2 g (0.01 mole ) of mercuric acetate, the mixture cooled and 0.72 g of vinyl ethyl ether poured in. The mercuric acetate dissolves rapidly. The required product precipitates on cooling with a mixture of salt and ice. Yield: 3.6 g (92.3%); m.p. 38-39° C (from ether).

The chemical behavior of mercurated oxo-compounds has already been outlined earl ier in this chapter. For the addition of mercuric salts to a-alkoxyacrylonitriles, see below. For the interaction of vinyl alkyl sulfides with mercuric salts, see Chapter 16.

A d d i t i o n o f M e r c u r i c S a l t s t o A m i n e s C o n t a i n i n g a D o u b l e B o n d

Diallylamine smoothly adds mercuric acetate in aqueous media, forming a morpholine derivative which was isolated, after preci-pitation, as 2,6-di-(chloromercurimethyl)morpholine [146]:

NH NH / \ / \

CH2 CH2 CH2 CH2

I ! I 1 CH2 = CH CH = CH2 - f HgX2 + H2O - » XHgCH2 — CH C H - C H 2 H g X

\ 0 /

Preparation of 2,6-di-(chloromercurimethyDmorpholine [ l 4 6 ] . Diallylamine (5 g, 0.05 mole; b.p. 108-111°C) is added to a solution of 30 g of mercuric acetate in 100 ml of water. The amine dissolves with considerable evolution of heat. After 12 hours, 0.3 g of a mercurous salt is f i l tered off and the fi ltrate treated with 7 g of KCl in 50 ml of water. The resulting white precipitate (26 g) is dissolved in 10% alkali, leaving behind a small amount of yellow mercuric oxide, A white precipitate of 2,6-di- (chloromercuri-methyl)morpholine appears on neutralization of the f i ltrate. The compound is insoluble in organic solvents and decomposes without melting on being heated.

In alcoholic media, mercuric salts add to octadec-9-enylamine, bis-octadec-9-enylamine and hendec-l-enylamine [275], p-Crotyl-aminophenylacetic acid adds mercuric salts in alcohols and glycols [266]. Additions of mercuric salts in methanol to o- and p-allyl-aminobenzoic acids are described in [276].

The addition to allyl acid amides will be described later in this chapter.


A d d i t i o n o f M e r c u r i c S a l t s t o O x o - C o m p o u n d s C o n t a i n i n g D o u b l e B o n d s a n d t o T h e i r F u n c t i o n a l D e r i v a t i v e s

A d d i t i o n o f m e r c u r i c s a l t s t o o l e f i n i c k e t o n e s . Saturated ketones such as benzalacetophenone [149, 277], benzalchloroacetophenone [277] and dibenzalacetone [277], and also unsaturated long-chain aliphatic ketones [278] and arylalkenyl and arylalkadienyl ketones with long-chain alkene or alkadiene groups [279] give addition products on reacting with alcoholic mercuric acetate in the cold. The reaction of benzalacetophenone is strongly accelerated in the presence of dimethyl peroxide, hydrogen peroxide and boron trifluoride-diethyl ether, and is slowed down by admixtures con-taminating the mercuric acetate: acetonitrile, pyridine, diethyl sulfide, and iJmns-styryl cyanide [149].

The addition to a,/3-unsaturated oxo-compounds, as always in such systems, proceeds against Markovnikov's rule.

Preparation of a-acetoxymercuri-/3-methoxy-/3-phenylpropiophenone [227 ] , Asolut ion of 25 g of benzalacetophenone and 38 g of mercur i c acetate in 250 ml of absolute methanol is le f t to stand till the NaOH reaction f o r mercur ic ion becomes negative. Evaporation of the solvent g ives 53 g of crysta ls . The melting-point a f ter recrysta l l i zat ion f rom methanol is 115°C.

Aryl vinyl ketones form on standing with methanolic mercuric acetate at room temperature addition products (isolated as halides) ArCOCH(HgHal)CH2OMe [280].

A d d i t i o n o f m e r c u r i c s a l t s t o k e t e n s a n d t h e i r d e r i v a t i v e s . Reac-tion of ketens with mercuric acetate or HgO in alcohol gives good yields of mercuri-bis-acetic acid esters [136]. The best proce-dure is to use mercuric oxide in the presence of a little acetate:

HgO + 3CH* = C = O + 2ROH H g ( ° C Q C H A > Hg (CH2COOR)2 + CH3COOH

Preparation of methyl mercuri-bis-acetate [136 ] , Keten (0.4-0.6 mo l e ) is added to an energet ical ly s t i r red suspension of 20 g (0.092 mo l e ) of HgO and 3 g (0.009 mo le ) of mercur i c acetate in 120 ml of absolute methanol, until complete dissolution of the HgO takes place. During the passage of keten the temperature is controlled so that it does not exceed 20-25°C. At the end of reaction the small amount of f r e e mercury is f i l t e red off and the solvent evaporated on a water pump at a temperature below 30°C. The re -maining crysta ls of the desired product (m.p. 96-98°C) , contaminated with methyl methoxymercuriacet ic acid, are dissolved in 100 ml of absolute methanol and an addi-tional 0.2 mole of keten passed in. Evaporation of the solvent under vacuum yields 35 g (100%) of the product, which is washed with the minimum volume of ether; m.p. 99-IOO0C ( f rom methanol).

The reactions of a - and / 3 - m e r c u r a t e d oxo-compounds with keten are accompanied by displacement of the compounds with the less active multiple bonds (olefin and vinyl alkyl ether) by the compound with the more active multiple bond (keten). Depending



on the medium in which the reaction is carried out, the products are mercurated acetic acid and its esters. The yields are high [41, 137], Halogenomercuriacetic acid and its esters have been obtained from )3-halogenomercuriethyl methyl ether:

X H g C H 2 C H t O C H 3 + CH 2 = C = O + R O H XHgCH 2 COOR

+ CH 2 = C H 2 + CH 3 OH

and from a-halogenomercurated ketones:

X H g C H 2 C O R ' + CH 2 = C = O + R O H XHgCH 2 COOR

(where R = H or Alk). Acetoxymercuriacetaldehydemonoethyl acetal acetate yielded mercuri-bis-acetic ester.

Preparation of chloromercuri acetic aci d [137] . Keten (0.05 mole) is passed into a solution of 1.5 g (0.005 mole) of /3-chloromercuriethylmethylether in 75 ml of hot water. Evaporation of the solvent gives 1.35 g (yield: 90%) of large crystals of the required pro-duct; m.p. 196°C (from methanol; sealed capillary).

Preparation of methyl chloromercuriacetate. A sixfold excess of keten is passed into a solution of 11 g (0.037 mole) of chloromercuriethyl methyl ether in 100 ml of absolute methanol. Evaporation of the solvent gives 9.2 g (yield: 90%) of the required product; m.p. 83°C (from methanol). Bromomercuriethyl methyl ether reacts with an excess of keten in ethyl bromide with the formation of methyl bromomercuriacetate in 82% yield.

Preparation of methyl bromomercuriacetate. Keten (0.05 mole) is passed into a suspension of 6.25 g (0.0185 mole) of bromomercuriacetone in 15 ml of absolute methanol at 5°C. Evaporation of the alcohol gives 6.6 g (yield: 100%) of the desired product; m.p. 80-81°C (from a mixture of benzene and n-octane).

Mercuri-bis-aldehydes and -ketones react with keten in water and alcohols to give mercuri-bis-acetic acid and its esters, e.g. [41, 137]:

H g (CH 2 CHO) 2 + 2H 2 0 + 2CH2 = C = O Hg (CH 2COOH) 2 + 2CH3CHO

Preparation of t-butyl mercuri-bis-acetate. Keten (0.6 mole) is passed into a cooled suspension of 43 g (0.15 mole) of mercuri bis-acetaldehyde in 100 ml of absolute t-butanol until all solids dissolve. Evaporation of the alcohol gives a 100% yield (64.3 g ) of the de-sired product; m.p. 85-86°C (from hexane).

The reactions of a-halogenomercuri- and mercuri-bis-oxo-compounds with keten in benzene afford a ,/3-unsaturated esters of halogenomercuri-bis-acetic acid [41, 137]:

O

— HgCH 2 — COR + CH 2 = C = O — H g C H 2 C ^ \

OC = CH 2

I R


Preparation of a-propylvinyl ester of mercuri-bis-acetic acid. Keten (0.1 mo le ) is passed into a cooled solution of 15 g (0.03 mo l e ) of mercur i -b i s - (methy l propyl ketone) in 50 ml of benzene. Evaporation of the solvent y ie lds 13.45 g (100%) of the required product; m.p. 70-71°C ( f rom absolute methanol).

The interaction of keten diacetal with mercuric acetate in anhy-drous acetone gives (after salting out with KCl) a 60% yield of an ester of tri (chloromercuri) acetic acid as a result of addition to the double bond and mercuration [281]:

CH2 = C (OR)2 + (CH3CO2) Hg

OR

(CH3CO2Hg)3 C — C -OR \

OCOCH3

O

(CH3CO2Hg)3C-C

O S ci' S

+ CH3CO2R (ClHg)3CC

\>R \>R Preparation of ethyl tri(chloromercuri) acetate [281], Small portions (total, 1 g ) of

mercur ic acetate are rapidly added to a solution of 2 g of keten acetal in 5 ml of dry acetone. Some heat is evolved and the solution becomes reddish owing to partial poly-merizat ion of the keten acetal. Water is added ti l l the system becomes slightly turbid, fo l lowed by aqueous KCl (in drops ) till nomore precipitate appears. Y i e ld 5 g (60% on the mercur i c acetate). Crystal l izat ion f r om methanol. The compound decomposes without melt ing.

The less reactive diacetals of chloroketen and bromoketen give with aqueous-alcoholic mercuric acetate small yields of ethyl mercuri-bis-chloro- (or bromo-)-acetates [281]: the yields are slightly higher if HgO in the presence of mercuric acetate is used instead.

When the reaction is conducted in ether, simultaneous addition to the double bond and mercuration result in the formation of ethyl di(acetoxymercuri)chloro- (and bromo-) acetic acid [281]:

2CHX= C (OC2H5)2+ 2Hg (OCOCH3)2 (CH3COOHg)2CX — COOC2H5

+ XCH2COOC2H5+ CH3COOC2H5

Preparation of ethyl di(acetoxymercuri)chloroacetate [281]. Solid mercur i c acetate (4 g ) is added to a solution of 6 g of chloroketen acetal in 5 ml of ether. A f t e r 24 hours, the precipitate is f i l t e red off and washed with ether. Y ie ld: 2.3 g. Evaporation of the solvent g ives an additional 1.3 g of the substance. Y ie ld : 3.6 g (90% on the mercur ic acetate); m.p. 159-160°C ( f rom alcohol or dichloroethane; decomposition).

Preparation of ethyl di(chloromercuri)chloroacetate [28 1J. A solution of IN KCl is added drop by drop to a solution of 0.2 g of ethyl d i (acetoxymercuri )chloroacetate in 20 ml of water ti l l no more precipitation takes place. Crysta l l i zat ion f r om alcohol. Y ie ld : 0.13 g (65%); m.p. 260-262°C (with decomposition, in a sealed capi l lary) .



For the addition of mercuric acetate to a-alkoxyacrylonitriles, see below.

The action of phenylmercury hydroxide on keten diethyl acetal gives, after intermediate formation of a fully substituted unsym-metric organometallic compound. Diphenylmercury and mercuri-bis-(ethyl acetate), isolated after reaction with mercuric chloride as chloromercuriethyl acetate [273] (see Chapter 12).

The interaction of dimethylketen dimethyl acetal with butyl chlo-ride, ZnCl, and HgCl2 leads to a 99% yield of methyl a-chloro-mercuri-isobutyrate [282].

The addition of mercuric salts in alcohols to the oxo-derivatives of certain heterocyclics containing double bonds in the ring will be referred to later in this chapter.

Allylacetone oxime adds mercuric salts in the cold in the pres-ence of alkalis, giving dihydroiso-oxazine derivatives [49]:

H2C = C H - CH2 - C H 2 - C - CH 3 + HgX (OH) -Il

HON

H2C CHCH2CH2CCH3 I I Il

XHg OH HON

CH2 — CH2

/ \ XHgCH2CH CCH3

x O /

An analogous compound is given by methylheptenone oxime [49], The additions of HgXOAlk to antipyrine and other alkylated 1-aryl-5-pyrazolones, accompanied by mercuration, will be referred to later in this chapter (see also Chapter 5).

The addition of mercuric chloride to the double bond in a carbonyl derivative of phosphorylide (VIII) (conditions not reported) leads to the formation of mercurated pnosphonium salts (IX) [362]:

(C0H5)3 P = CHCOC6H5 + HgCl2 -

V I I I

HgCl /

(C6H5)3 P + - C - H \

COC6H5. I X

Cl-

Salt (IX) is a quasicomplex and exhibits dual reactivity. With benzaldehyde, it reacts with the elimination of HgCl2 and formation of £mns-benzoylstyrene. On the other hand, sodium methoxide el im-inates HCl from this salt, giving mercury-containing phosphorylide. The latter product may be converted back into (IX) with dil. HCl.


A d d i t i o n s o f M e r c u r i c S a l t s t o C a r b o x y l i c A c i d s C o n t a i n i n g E t h y l e n i c B o n d s a n d T h e i r D e r i v a t i v e s

Unsaturated acids of this type add mercuric salts under the same conditions as the olefins. In the case of a,/3-unsaturated acids, the mercury enters into the a-position of thecarboxyl and the hydroxyl (or alkoxyl, in alcoholic media) into the /3-position of the -COOH. This has been shown, for example, by converting the product of the addition of mercuric acetate to crotonic acid in an aqueous medium into /3-hydroxybutyric acid by the action of H2S; the reaction is specific for these substances. According to Biilman [145, 284], only the cis- (and not trans-) configurations of a,/3-unsaturated acids are capable of adding mercuric salts. Thus [145], acrylic, crotonic, maleic, itaconic, citraconic and allocinnamic acids add mercuric salts, whereas cinnamic, fumaric and mesaconic acids do not. However, this only applies to reactions in aqueous media, since in alcoholic solutions these acids add mercuric acetate (out of those listed, only cinnamic acid has been tried).

Acrylic acid [145, 167, 285], its ester [167] and /3-cyclopentyl-acrylic acid [286] form under the usual conditions, e.g. by the action of methanolic mercuric acetate, addition products with the mercury in the a-position with respect to the carboxyl group. Studies have been carried out on the kinetics of the methoxymercu-ration of acrylic esters (second-order reactions) [62] and meth-acrylic esters [450].

Whereas in keten diacetal the double bond is passivated by the replacement of one OR group by CN, the interaction of the resulting a-alkoxyacrylonitriles with aqueous mercuric acetate leads to the esters of monomercurated acetic acid [135]:

OR

CH2 = C + HgAc2 + H2O \

CN

- CH3COOHgCH2COOR + Hg (CN)2 + 2CHSC00H

In contrast to the almost instantaneous addition to propylene, the above reaction requires several hours.

Two moles of mercuric acetate should be taken for every mole of the unsaturated compound; if the molar ratio of the reagents is 1:1, the yield falls from 90-95 to 40-45%.

Preparation of acetoxymereuripropyl acetate [135 ] , a -P ropoxyacry l on i t r i l e (11.1 g, 0.1 mole ) is added, in several portions and with vigorous shaking, to a cooled solution of 63.6 g (0.2 mo l e ) of mercur i c acetate in 150 ml of water. The white precipitate is separated off. Evaporation of the mother l iquor results in a further portion of prec ip i -tate, which is again separated off . The total y ie ld is 34.6 g (95%); m.p. 1 0 9 - I l l 0 C ( f rom methanol).

/ CH3COOHgCH2C-CN

\ OHJ

HgAc2



The addition of methanolic mercuric acetate to / 3 - m e t h y l c r o t i n i c acid has been carried out under the usual conditions [287].

Lactones

ClHgCH2CH-CH2

I 0 1

O = C CR2

(where R = H, C6H5) are formed by the addition of mercuric salts in methanol or water to allylacetic and allyldiphenylacetic acids [288, 289, 451, 452]. Mercuric salts have been added in alcohols and glycols to 2-monenoic [266] and 5-phenyl-2-pentenoic [266] acids. The additions of methanolic mercuric acetone to a-propyl-crotonic [290] and 2,7-carbethoxy-2-heptenoic [291] acids have been described. Aqueous mercuric acetate adds in the usual man-ner to undecylenic acid [292], and the product of the interaction of undecylenic acid with aqueous HgO solution (after acidification with acetic acid) has been separated in the form of a lactone [293], Mercuric salts in methanol have been added to oleic and erucic acids [294].

Normal conditions were used for the additions of mercuric ace-tate in the presence of lower aliphatic alcohols to the nitriles of oleic acid (product: 9-acetoxymercuri-10-alkoxypalmitonitrile), undecylenic acid (product: l-acetoxymercuri-2-methoxyundecano-nitrile), and other higher unsaturated acids [295].

The esters of the unsaturated acids, for example oleic and Iino-Ieic, and in particular of triolein, readily give addition products, giving esters of mercurated ether-acids [8, 296, 297]. These fatty acid derivatives are oils distinguished by a high specific gravity [296],

As for the other unsaturated compounds, the addition of methan-olic mercuric acetate to the esters of the higher unsaturated acids (oleic, elaidic, erucic, and brassidic) occurs faster with the cis-isomers than with the trans (second-order reactions [298]). Thus, the rate constants of the additions of mercuric acetate to the methyl esters of oleic and elaidic acids are in the ratio of 12.5:1.

Synthesis of 9-aeeto xymercu ri-10-methoxy palmitic acid [298] . Methyl oleate ( I O g ) is added to a solution of 14 g of mercuric acetate in 250 ml of methanol containing 2.5 ml of water and 1 ml of glacial acetic acid. After being mixed in a vessel f i l led almost to the top, the system is set aside for 24 hours in the dark at room temperature. The greater part of the methanol is evaporated off on a water bath at 90° C and the residue extracted with 200 ml of chloroform and washed with water. After drying and vacuum evaporation of the chloroform, the residue was held for 5 hours under vacuum at 30-40°C/0.01 Atm, for complete removal of the solvent. The traces of sludge are f i ltered off through a glass f i l ter ; the yield of colorless liquid is 13.2 g (66%).

The different rates of the addition of mercuric salts to the cis-and ^roms-isomers of unsaturated acids and their derivatives have


been applied to determinations of the compositions of mixtures of elaidic and oleic esters [299].

In the case of the unsaturated fatty acid esters containing two or more double bonds (linoleic and linolenic), different rates have been observed for the formation of mono- and di-adducts (and also of the tri-adduct in the case of the linolenic ester) [300],

Chaulmo-ogric acid and its ethyl ester give addition products with mercuric acetate in the cold in a mixture of ethanol and acetic acid [301]. The probable structure of the adduct in the case of the acid is

HgCH-CH (CH2)i2COt I I

C2H5OCH CH2

I CH2

The additions of mercuric acetate (in ethanol) to diallylacetic and (in methanol) to diallylmalonic acid have been carried out on both allyl groups [302]. In the first case the product was

CH2CH(OC2H5)CH2HgBrx

C2H5O2CCH J O

^CH2CHCH2HgBr / 2

The additions of mercuric acetate to bicycloheptencarboxylic acid and to 4-hydroxy- (and 4-methoxy)cyclohexencarboxylic acids, and to the latter's nitrile, have been conducted by setting the mixtures aside for 2-7 hours in methanol [252], Inthe f irst case the reaction was accompanied by lactonization.

The addition of aqueous mercuric acetate to 1,4-methylene-A5-cyclohexen-2-carboxylic acid [stereoisomer (X)] leads to two lac-tones, (XI) and (XII), forming in yields of 77 and 3%, respectively,

H P X 2

COOH H O O

H g X

This is the f irst example of the formation of two diastereomers during hydroxymercuration [303],

The stereoisomeric acid (X')

OOH

/ X'

also forms two products, in the ratio of 4:1, to which definite configurations had not, however, been assigned [303],



According to [28, 198, 304], the additions of mercuric salts to norbornen- endo-cis-2,3-dicarboxylic acid ( X H I ) (of mercuric acetate in methanol [304] and of aqueous mercuric chloride at 80°C [28]) and to the dimethyl ester of 1,4- eajo-ethylen- A5-Cydo-hexen- endo-2,3-dicarboxylic acid [304] occur in the endo-cis -position, since after appropriate treatment the adducts give inter-nal mercuric salts of the carboxylic acids and lactones. However, Kreevoy and Kowitt [61] consider it more probable that these in-ternal mercuric salts are bipolar ions (see [266]); for example, the product of the addition to ( X I I I ) has the structure (XIII')

H g X 2

HOH

xiir COO^

and the addition of OR- and HgX-groups occurs as usual in positions trans with respect to one another.

According to Wright et al. [28, 304], the addition of mercuric salts to the dimethyl ester of norbornen-endo - cis-2,3-dicarboxylic acid ( X I V ) (of mercuric acetate in methanol, dioxan, or acetic acid) and to norbornen- trans -dicarboxylic acid [28] ( X V ) (of mercuric chloride in aqueous solution at 100°C) occurs both in the e x -positions (OR with respect to HgX) [predominantly for the acid, product ( X V ) ] and in the trans -positions [predominantly for the ester, product ( X I V ) ] :

Hg(QCOCH3 )2

COOMe CH3OH (C4H8O2 lCH3COOH)

RO

X I V COOMe XHg

X I V '

COOH HgCl 2

H 2 O

COOH

COOMe

COOMe

COOH

CIHg OOH X V -

Addition of aqueous acetate to the ester gives [28] the monoester lactone together with the £mns-product of addition to the £m?is-acid.

According to Chiu and Wright [198], and in amendment of ear l ier data [304], the addition of OR- and HgX-groups during the hydroxy-mercuration (with aqueous mercuric chloride or acetate) of A5-2,2,2-bis-cyclo-octen-2,3-dicarboxylic acids and their derivatives {cis- and trans -dicarboxylic acids, dimethyl ester and anhydride ( X V I ) of the endo-cis- acid) occurs into the positions trans with


respect to one another, with simultaneous lactonization. For ex-ample, (XVI) gives ( X V I ) :

HgX2

H2O XHg

xvi- COOH

One of the rare cases of cis-addition of OR and HgX to the double bond is the hydroxymercuration [75, 305, 306] and ace-toxymercuration [306] of the dimethyl ester of exo-cis-3,6-endo -oxo-A4-tetrahydrophthalic acid (XVII); the product is (XVI I ) [75, 305, 306]:

O O J ^ y C O O C H 3 H g (OCOCH3 )2 j C l ' ^ C l t ' g y J ^ C O O C H 3

/ L ^ ^ p COOCH 3 HOR R o n Z J ^ J c o o c h 3

XVII XVir

( R = H [75, 305] or CH3CO [306]). The reaction of the mercuric salt of trinitromethane in water

with (XVII) results in a hydroxymercurated compound and not in a product of the addition of X and HgX (X = (NO23C) across the double bond; this also indicates the cis-structure of the addition product [198a] (see [61, 238]).

Preparation of the dimethyl ester of 4-hydroxy-5-chIoromercuri-3,6-endo-oxyhexa-hydrophthalic acid [306].

0

ClHg\IX^/COOCH3

h o X Z A Z c O O C H 1

A mixture of 1 g of the dimethyl ester of exo-cis -3,6-endo-oxo- A4-tetrahydro-phthalic acid and 1.1 g of mercuric acetate in 70 ml of water is stirred for 12 hours and filtered. A solution of 0.5 g of NaCl is added and the precipitate separated off. The yield is 1.9 g (90%); m.p. 246°C (with decomposition, from methanol).

The same reaction in glacial acetic acid leads to the 4-acetoxy-5-chloromercuri- derivative. The 4-acetoxy-5-acetoxymercuri-derivative has been obtained by using mercuric acetate in dioxan.

Owing to coordination of the mercuric ion with the endo-carbo-methoxy group, the addition of aqueous mercuric acetate to the



dimethyl ester of eao-l-methoxy-3,6-enrfo-oxo-4- £mns-tetrahydro-phthalie acid is endo - cis- [306a] and not exo-cis- as in the case of the non-methoxylated exo-exo- acid (see above):

As has already been mentioned, cinnamic acid in various alcoholic solutions adds mercuric acetate to give C sHsC H(OR)CH(HgX)COOH, where R = CH3 [199, 256], C2H5, C3H7, n-C4H9, n-C5Hu and n-C16H33

[256]. No addition takes place in glycol and the mercuric acetate is

merely reduced to the mercurous salt [256], Diastereomers of the adducts and of their internal mercuric

salts have been obtained in the methoxymercuration of cis- and drans-cinnamic acids [307] (see above).

The addition of mercuric salts to cinnamic acid in aqueous media has been reported [308],

Methyl cinnamate gives well-crystallizing methyl a-acetoxy-mercuri-/3-phenyl-/3-methoxypropionate according to the scheme [8,72,296,450]:

C 6 H 5 C H = C H C O 2 C H 3 + (CH3COO)2 Hg 4- CH 3 OH - CH 3 COOH

+ C 6 H 5 C H - C H C O 2 C H 3

I I CH 3 O HgOOCCH 3

Preparation of the methyl ester of a-ace toxymercuri-3-phenyl-.5-me thoTy propionic acid LA]. Methyl trans-cinnamate ( I O g ) is added to a solution of 19.6 g of mercuric acetate in 100-120 ml of acetone and the mixture well stirred. Crystals begin to appear after 4 hours and after 6 hours an NaOH test fails to disclose the presence of mercuric ions.

After 2 days the yield of crystals reaches 18 g (64-65%). An additional amount of the product may be obtained by evaporation of the mother liquor in the form of an acetate, or by precipitation with aqueous NaCl in the form of a chloride. The acetate is recrystal-lized from ethyl acetate, with additions of petroleum ether if necessary; m.p. 139°C.

The same method was used to obtain mercury derivatives of al-koxy-acid esters, of general formula C6H5CH(OR)CH(HgX)COOAlk,


where R = C2H5 [8, 72], n-C3H7, iso-C3H7 and n- and iso-C4H9 [9], carrying out the reactions in the corresponding alcohols.

The melting-temperatures of the ethyl esters of a-halogeno-(and a-acetoxy-) -mercuri-^-methoxyhydrocinnamic acids have been determined [20]. According to Wright [72], the interactions of mercuric salts with unsaturated acids are considerably accel-erated in the presence of a little nitric acid. Thus, the addition of mercuric acetate in methanol to methyl trans-cinnamate requires 75 minutes in the presence of nitric acid (0.05 g per 0.01 mole of mercuric acetate) and 36 hours in the latter 's absence.

The addition to the ezs-isomer occurs immediately without a catalyst [72],

The addition of methanolic mercuric sulfate to allyl cinnamate occurs in both double bonds. After treatment with NaCl, the product has the structure [9, 309]

C 6 H 5 C H — CHCOOCH2 — C H — C H 2

I l I l O C H 3 HgC l O C H 3 HgC l

The action of the addition product obtained f rom a mercuric salt and cinnamic ester in alcohol on the semi-allylamide of camphoric acid results in addition of the mercuric salt to the allylic double bond [310].

Z-Menthyl [43] and rf-bornyl [44] cinnamates give addition pro-ducts on standing for a few days with cold methanolic mercuric acetate (see beginning of this chapter).

Cis- and trans-styryl cyanides react with methanolic mercuric acetate in the presence of h n o 3 [144] or boron trifIuoride-diethyl ether [149]; the £m«s-isomer gives also the R2Hg compound [149].

Methanolic j»-methoxycinnamic acid boiled for 20 hours with an excess of mercuric acetate gives a-3,5-triacetate of mercuri-/3-4-dimethoxydihydrocinnamic acid [311] as a result of both addition to the double bond and mercuration into the ring.

Addition products are given by 0- and w-nitrocinnamic acids after boiling for many hours with mercuric acetate in methanol [311] (see [256]; the 0-isomer requires 30 hours and the m-isomer 10 hours.

Glutaconic acid reacted with mercuric acetate yields a mixture of the mercurated compound (XVII I ) , obtained by substitution of a methylene hydrogen, and compound (XIX), resulting both f rom addition to the double bond and mercuration [312]:

O - H g O - H g H g - O

C O — C H C H = C H C O O H C O — C H C H O H - C H — C O

XVIII XIX Eugenolacetic [268, 361] and allylphenoxyacetic [314] acids add

mercuric acetate in methanolic solution. Fortheadditionof mercu-ric salts to p-allyloxybenzoic acid, to its ester and to allyloxyben-zene sulfonic acid.



Under the usual conditions, in the cold, methanolic mercuric acetate adds to o- and p-allylaminobenzoic acids and their esters [276].

Mercuric salts are added in methanol to each double bond by o-and p-diallylacetaminobenzoic acids and diallylacetophthalimide [276].

The addition of R" OHgX to olefinic acids forms the foundation of a method of synthesizing a-amino-/3-hydroxy-carboxylic acidsfrom unsaturated acids [287, 315, 316]:

RCH =CHCOOR' S R C H - C H C O O R ' Br, R "OH

OR" HgX

RCH - CHCOOR' RCH - CHCOOR' H y d r ° l y s j s RCH-CHCOOH

OR" Br OR" NH2 HO NH2

Coumarin, coumaric and coumarinic acid, and their derivatives add mercuric salts to give various products, depending on the con-ditions of the reaction (temperature, solvent) and on whether the mercuric salt is the chloride, oxide, or acetate. Thus, mercuric chloride in organic solvents adds in the cold to the double bond in coumarin (and also to the double bond in 7-methylcoumarin), forming compounds of the type

R O

CHCl

R = H or CH3 [317], which are also obtained when coumaric and 4-methylcoumaric acids are boiled with HgCl2 [318]. An analogous compound is obtained from 5-nitrocoumaric acid [318]. Coumaric acid [254], coumaric acid methylated on the phenolic hydroxyl [254] (see, however, [319]) and coumarinic acid [254] add mercu-ric acetate in methanol in the usual manner (addition of RO and HgX). Heating of these acids [319, 320], 4-methylcoumaric acid [320], the methyl esters of coumaric [319, 320] and 4-methylcou-maric [320] acids, coumarin [256, 317] (see [254]), umbelliferone [321] (in this case with all reagent ratios) and 4,7-dimethylcoumarin [321] with methanolic mercuric acetate results in both addition to the double bond and in ring mercuration of the above acids and esters into positions 3 and 5 and into coumarin; for example

OH

^ J j^ + Hg (OCOCH3)2 + CH3OH

CH=CHCOOH


CH3COOH 4

CH3COO7

HgOCOCH3

A - O H ki1—CH(OCH3)CH(HgOCOCH3) COOH

in ring mercuration of umbelliferone into positions 6 and 8, and in ring mercuration of 4,7-dimethylcoumarin into position 6.

5-Nitrocoumaric acid and its methyl ester give under these con-ditions 3, a-diacetoxymercuri-5-nitro-/3-methoxydihydrocinnamic acid and its ester, respectively [320]:

/ ^ J - C H = CHCOOR + Hg (OCOCH3)2 + CH3OH -O2N

HgOCOCH3 I

- CH3COOH + 0)_CH(0CH3)CH(Hg0C0CH3)C02R O2N

(R = H or CH3). 5-Nitro-2-methoxycinnamic and -allocinnamic acids are not mer-

curated by cold methanolic mercuric acetate, but merely enter into addition reactions [319], Only addition to the double bond occurs also during the action of alkaline HgO solutions on coumarin, 7-methylcoumarin, and 6-nitrocoumarin [322], e.g.

O v „ .OH X N C O H g ( O H ) 1

h J c H OH' ' \ A c : H(OH)CH(HgOH)COOH

In aqueous solution, coumarinic acid reacts with three molecules of mercuric acetate in the cold, forming the product of addition to the double bond which is also mercurated in the ring in positions 3 and 5 [320].

Synthesis of a-acetoxymercuri-/3,2-dimethoxydihydrocinnamic acid [31**].

OCH3

c. CH(OCH 3 )CH(HgOCOCH 3 )COOH

Mixing of equimolar amounts of coumarinic acid methylated at the phenolic hydroxyl (1.8 g in 10 ml of methanol) and mercur i c acetate (3.2 g in 20 ml of methanol) results in the format ion of a white crysta l l ine precipitate within a few minutes. The reaction is complete within 4 hours. The precipitate is f i l t e red off and washed care ful ly with methanol. It decomposes at 204° C.



Synthesis of A,3,5-triacetoxymercuri-/3-2-dimethoxydihydrocinnamie aeid [319],

HgOCOCH3

,OCH3

CH3COOHg CH(OCH3)CH(HgOCOCH3)COOH

Mercuric acetate (12.5 g, > 3 moles) and 1.8 g (1 mole) of the methyl ether of cou-marinic acid in methanol are boiled for 20 hours. The dark precipitate forming after the f i rst 30 minutes is f i l tered off and rejected, and the final product (colorless preci-pitate) is washed several times with methanol. The compound decomposes at 220-221°C).

The addition of methanolic mercuric salts to 3-carboxy-8-allyl-coumarin has been carried out only with respect to the allylic double bond, without involving the double bond of the pyrone ring. 6-Allyl-7-hydroxy-4,8-dimethylcoumarin also adds methanolic HgCl2 only to the allylic double bond [324].

For the mercuration of coumarin derivatives without the involve-ment of the double bond, carried out by the action of mereurating agents in the presence of alkali, see Chapter 5.

The addition of alcoholic mercuric acetate to the allyl esters of xanthogenic acids is accompanied by replacement of the thione sulfur with oxygen and also by conversion of the thione function into a thiol one [325].

The additions of mercuric salts to esters containing a double bond in the alcohol residue have already been mentioned.

A d d i t i o n o f M e r c u r i c S a l t s t o A l k e n y l A m i d e s

Vinylphthalimide adds mercuric acetate in methyl alcohol to the double bond of the vinyl group [326].

For the additions of mercuric salts in aqueous or alcoholic solutions to the allyl amides of acids, carried out under condi-tions normal for the addition of mercuric salts to double bonds (sometimes in the cold, often on boiling), the reader is referred to the literature: to allylurea [152, 327-335], allylalkylurea [336], allylbiuret [332, 337], allylhydantoins [338], allylveronal [339], mono- and poly allylbarbituric acids [340], propionylallylurea [331], N-allylparabanic acid [331], |6-carboxypropionylallylurea [341], allyl amide of propionic acid [331], N-allyl-carbamyl-jS-carbamyl-propionic acid [343], allyl amides of some aliphatic carboxylic hydroxy-acids [331, 334, 345], 4-allylcarbamoylcyclohexancar-boxylic acid [347], to allylsuccinimide [348-350], to the allyl amide of adipic [348] and azelaic [349] acids, to the allyl amido of hydantoic acid [152], to the allyl amide [346, 351-353], and the monoamide [354] of camphoric acid (the latter possibly containing a different unsaturated chain) (see also [310]), to diallyl amide of cyclohexandicarboxylic acid [355], to the monoallyl amide of t r i -


methylcyclopentandicarboxylic acid [356], to N-allylbenzamide (in piperidine [357]), to the N-allylcarbamates of o- [266, 332, 355, 358, 359], m- [266], and p-phenoxyacetic acids, to the allyl amide of ^-aminosalicylic acid [360], to the allyl amide of hippuric acid [152], to the diallyl amide of saccharinic acid [344], to the allyl amides of substituted naphthoic acids [363], to the N-allyl amide and N-semi-amide of phthalic acid [355, 364], to N-allylphthalimide [365-370], to the allyl amide of nicotinic (inpiperidine [331]), quino-linic [331], and other substituted pyridinecarboxylic acids [302, 331, 371-375], to the allyl amides of alkanesulfonic [152] and alkanesul-famic [152, 363] acids, to N-allylsulfonamidobenzoic acid [376], substituted uracilcarboxylic acids [152], to the allyl amides of thiophencarboxylic [152] and thiophensulfonic [152] acids, to the allyl amide of theophylline-7-acetic acid [377] and the allyl amides of several acids in the medium of secondary amines [18, 357].

Preparation of N - (/3 - carboxypropionyl) - N - (2 - methoxy - 3 - halogenomercuripropyl)urea [ 3 4 l ] . A hot solution of I O g (0.05 mo l e ) of N- (/3-carboxypropionyl )N ' -a l ly lurea in 150 ml of methanol is rapidly added to a hot solution of 15 g (0.048 mo l e ) of mercur ic acetate in 200 ml of methanol. A white precipitate appears at once and the resulting suspension is boi led f o r 3 hours, cooled overnight to room temperature and f i l tered. The precipitate is washed with 100 ml of methanol. Y ie ld : 20 g (91%). The melting-point of the crude product is 177-178.5°C (with decomposition). A f t e r puri f ication by dissolu-tion in aqueous NaHC03 (but not alkal i ) and precipitation with acetic acid, the yie ld is 90% and the melting-point 188.5 190.5°C (with decomposition). The halide is obtained by slow dissolution of 0.05 mole of the product in 50 ml of water containing 0.052 mole of Na or K halide. A f t e r f i l trat ion f rom the trace of precipitate, the solution is acidi f ied with 3 ml of acetic acid. Theresu l t ingprec ip i ta te i s washed with water and recrys ta l l i z ed f r om methanol (50 ml per g f o r the chloride and 80 ml pe r g f o r the bromide) . The yields are 98%, fal l ing to 92-93% af ter recrysta l l i zat ion; m.p. 161-162.5°C (chloride) and 163-164°C (bromide) .

The addition of mercuric salts to the allyl amides of a-amino acids (glycine, alanine, d , Z-leucine, d, ^-methionine, d, Z-phenyl-alanine) is possible only if the amino group is benzoylated [378],

Mercuric salts add in the usual manner to allyl groups in the side chains of purines [379-385] and in allyl-containing urethanes [380, 381, 386].

A d d i t i o n o f M e r c u r i c S a l t s t o H e t e r o c y c l i c C o m p o u n d s C o n t a i n i n g D o u b l e B o n d s i n t h e R i n g o r S i d e C h a i n

Heating of a solution of thionaphthenesulfone in methanol with HgO in acetic acid results, after 5 days, in an addition product [387] by the reaction:

0 Jj + Hg (CH3CO2)2 + CH3OH

SO2 0 ]j T-OCH3

HgOCOCH: SO2

3



Aqueous mercuric acetate has been added to the allylic double bond in N-methyltetrahydroquinoline-8-allyl ether sulfate [258]. Mercuric acetate in glacial acetic acid has been added to 3-allyl-oxysulfolan in methanol, after the mixture had been boiled for about 12 hours [313]. The product was an oil.

; T-OCH2CH=CH2 H g ( O C O C H j ) 2 j T-OCH2CH(OCH3)CH2HgO2CCH3

SO2 CH>OH SO2

Mercuric acetate has been added to 2,5-dihydrothiophene-5-dioxide (sulfolene-3) [313]:

p , Hg(OCOCH3)2 CH3O HgOCOCH3

Addition of mercuric salts to sulfonene-3 [313]. Preparation of 3-acetoxymercuri-2-

methoxysulfolan. A solution of 11.8 g of sulfonene-3 in absolute methanol is treated with 2.42 g of benzoyl peroxide and then with a solution of 31.9 g of mercuric acetate and 7.2 g of acetic acid in hot methanol. The mixture is boiled for 12 hours and then concentrated at 50-60°C. The resulting oil is stirred with acetone and the insoluble white residue rejected. The solvent is evaporated at room temperature. Dissolution of the remaining oil in chloroform, treatment with animal charcoal and extraction with ether gives a colorless oil which crystallizes after a few weeks; m.p. 105°C; yield: 63%. The chloride, obtained from the acetate by aqueous NaCl, decomposes during crystallization.

The addition of mercuric acetate in methanol to 2,3-dihydropyran gives 3-acetoxymercuri-2-methoxytetrahydropyran [250]:

HgOCOCH3

Hg(OCOCHs)2 ^ N / CH3OH

O

Antipyrine and other alkyl-substituted l-aryl-5-pyrazolones react with alcoholic mercuric acetate at 60°C, with addition of HgX and OR to the double bond and simultaneous mercuration into position 4 and into the aromatic ring [289], In the case of 4-bromo- and 4-amino-substituted antipyrines, addition to the double bond occurs only on fusion with mercuric acetate (160°C); solution of -HgOCOCH3 and HO- groups takes place side by side with mercuration into the benzene ring [283] (see under "Mercu-ration of heterocyclic compounds", Chapter 5).

Additions of mercuric salts in various alcohols to the vinyl groups in N-vinylcarbazole, pyrrolidone and &)-caprolactam have been described [388]. Mercuric acetate has been added to 2-diethyl-aminomethyl-3-vinylquinuclidine in a mixture of dilute sulfuric and acetic acids [389], The additions of mercuric acetate in various


alcohols to l,6-diazabicyclo-(4,4,0)-3-decen-7,10-dione and to 2,5-dimethyl-3-decen-7,10-dione have been carried out with 3-hour periods of boiling [390, 391]:

O ChR c

H C V g N ^ 8 C H 2

H C V ; w h > CHR Cj

O

Hg(OCOCH3)2

R'OH

CH2

C N CH2

H3CCO2Hg/ x C ^ R x C x

O

The addition of mercuric salts to the allylic double bonds in the allyl amides of pyridinecarboxylic acids and allyl-containing purine derivatives has already been mentioned in the previous section. The additions of mercuric salts (in methanol, n-propanol or water) to several derivatives of 1,2,3,6-tetrahydropyridazine, 1,6,8-triaza-bicyclo-(4,3,0)-nonen-7,9-dione:

O

H g ( O C O C H 3 ) 2

R ' O H

H3CCO2

i I ) H8AzV

NR

and 1,2-dicarbamyl-l ,2,3,6-tetrahydropyridiazine:

R V , f4 6 NCONH2 Hg(OCOCH3)2

U3 INCONH2 v2/

R'OH 'NCONH2

NCONH2 A H3CCO2Hgx N/

occur only in the presence of nitric acid. In the latter's absence, the mercury adds to the amide nitrogen [391],

Preparation of 4-chloromercuri-5-methoxy-l,2-dicarbamy lhexahydropyridazine [391 ] . 1,2-Dicarbamyl- 1,2,3,6-tetrahydropyridazine (8.5 g, 0.05 mo ie ) is d issolved in 1 l i ter of boiling methanol and a hot solution of 15.9 g (0.05 mo l e ) of mercur i c acetate in 125 ml of methanol containing 0.5 ml of conc. HNO3 is added. The resulting white precipitate is redissolved by heating and addition of 12.5 ml of g lacial acetic acid, and the mixture set aside f o r 18 hours at room temperature. The prec ip i tate weighs 18 g (yield: 78%) of the 4-acetoxymercur i -5-methoxy- l ,2-d icarbamylhexahydropyr idaz ine ) .

In a solution containing 1.6 g (0.04 mo le ) of NaOH in 150 ml of water is suspended 0.039 mole of this mater ia l , the solid dissolved by heating to 35-40°C on a water bath and the solution f i l t e red through diatomaceous earth to r emove an admixture of insoluble black mercurous salts. The f i l t ra te is saturated with C O 2 and the resulting solution of 4 -hydroxymercur i - der ivat ive treated with 2.4 g (0.04 mo l e ) of NaCl in 10 ml of water, cooled, and again saturated with CO 2 . The crysta l l i z ing product g ives 11.6 g (0.022 mole ; yie ld: 44%) of the des ired compound; m.p. 224-229°C. This is pur i f ied further by dissolution in a solution of 0.9 g (0.022 mo l e ) of NaOH in 100 ml of water at 3°C. F i l t ra -tion, cooling and saturation with CO2 g ives a precipitate which is washed with absolute alcohol and ether and dried under vacuum. Y ie ld : 8.3 g (40%); m.p. 232-233°C.



c) Addition of Mercuric Salts to Carbon Monoxide

This reaction is in many respects analogous to the addition of mercuric salts to ethylene in an alcoholic medium and, like the latter, was discovered by Schoeller and Schrauth [104]. The re-action occurs when alcoholic acetate is saturated, with shaking, by CO at an excess of pressure of 1 Atm. As for the olefins, the alcohol participates in the formation of the final product

Hg (OOCCH3)2 + CO + ROH CH3COOHgCOOR + CH3COOH

Here too, the reaction is faster in methanol than in ethanol, but the addition as a whole is much more difficult than the addition to ethy-lene. The mercuric acetate is reduced to a mercurous salt as a side reaction.

The structures were demonstrated on the reactions

N H 3

ClHgCOOCH3 + I2 - HgI2 + C1C00CH3 —* H2NCOOCH3

A l H g + H 1 O CH3COOHgCOOC2H6 HCOOC2H5

and were confirmed by infra-red and proton resonance spectra [109], As usual, the acetate ion is readily replaced by a halogen by the

addition of a solution of K or Na halide. Heating above the melting-temperature results in decomposition with evolution of CO, and heating with alkalis in precipitation of the metal and formation of a carbonate. An excess of hydrogen sulfide (and all symmetrizing agents except triphenylphosphine, see Chapter 13), decomposes the compound with elimination of CO, whereas an equivalent amount of H2S precipitates a white crystalline sulfide.

Preparation of methyl acetoxymercuriformate [104], A solution of 26 g (85%) of mer-curic acetate in 100 ml of methanol is placed in a 300-ml thick-walled vessel fitted with a tube carrying two narrower tubes (ground joints) provided with taps. The vessel is con-nected by pressure tubing to a nitrometer, whose bulb is connected to the system with a length of vacuum tubing capable of withstanding a 1 Atm excess of pressure. The taps are lubricated with graphite, the joints sealed with paraffin wax and the tubing reinforced with rings of copper wire. After displacement of the air with carbon monoxide, an excess of pressure of 1 Atm is set up in the apparatus by raising the nitrometer bulb and the vessel put on a mechanical shaker.

Slow continuous absorption of CO takes place, which comes to an end after 24 hours. In all, 1151 ml of CO (reduced to STP ) are absorbed, 21 ml of this volume corresponding to gas dissolved without reaction in the mixture. The calculated amount is 1113 ml. More -over, 1.2 g of mercuric acetate is reduced to the mercurous salt. At the end of the absorp-tion, the latter is f i l tered off and the f i ltrate f reed from methanol and acetic acid by evaporation at 30-35°C under vacuum. The oily residue sets into a crystalline crust of starlike clusters of small needles. This material is dissolved in 75 ml of warm chloro-form and the solution f i l tered and treated with 5-6 volumes of petroleum ether. Immediate precipitation takes place. After 24 hours in an icebox, the precipitate again forms clusters of needles. The system is placed f o r a further 2 hours into a cooling mixture to increase the yield and the precipitate finally f i l tered off and washed with a little cold methanol and then with ether. Yield: 15 g (88%); m.p. I lO0C (with decomposition). The substance dis-solves readily in methanol and ethanol and in chloroform, is moderately soluble in warm water, ethyl acetate and benzene and sparingly so in ether, petroleum ether and ligroine.


Conversion to the ch loromercur i -der ivat i ve is accomplished by the addition of 0.5 g of NaCl of the acetoxymercuri compound in 10 ml of methanol. A f ter 12 hours at 0°C and 2 hours in a cooling mixture, the precipitate is f i l t e red off . Y ie ld : 1.5 g (80%); m.p. 110°C (with decomposit ion).

Preparation of ethyl acetoxymercuriformate. This compound is prepared exactly as above, f rom 20 g of mercur i c acetate in 150 ml of absolute alcohol, but the absorption of CO requires 3 days. Y ie ld: 12.5 g (90%). When the compound is heated in a capi l lary, it softens at 65°C and decomposes rapidly at 125°C. The solubility is s imi lar to that of the methyl ester . C lHgCOOC 2H 5 melts with decomposition at 88°C.

For the symmetrization of the products of the addition of CO to mercuric salts, see Chapter 13.

An excess of benzyl bromide and carbomethoxymercury acetate (boiled for about 23 hours in chloroform) gives rise to benzyl ace-tate, methyl benzyl ether, carbomethoxymercury bromide and both mercuric and mercurous salts [453], Thereactionofbenzyl bromide with carbomethoxymercury bromide under analogous conditions results in liberation of CO and the formation of methyl benzyl ether and mercuric bromide [453], Photochemical decomposition of car-bomethoxymercury iodide in benzene (6-hour exposure to ultra-violet light at 6-10°C, under nitrogen) gives methyl benzoate and possibly toluene [453], It is well worth noting that carboxymercury acetate with ethylene in ethanol forms ^-methoxyethylmercury acetate (5 hours in an autoclave at 600C) [453], This is one of the two known cases of obtaining one type of quasicomplex from another.

Carbon monoxide adds readily to HgCl2 in secondary amines [108]. A product having the composition

C 5 H i o > N — C - H g C l - C 5 H i 0 N H Il O

has been obtained in quantitative yield by saturating with CO a solu-tion of mercuric chloride in dry piperidine at room temperature.

d) Addition of Mercuric Salts to Triple Bonds

A d d i t i o n o f M e r c u r i c S a l t s t o A c e t y l e n i c H y d r o c a r b o n s

The early work on the addition of mercuric salts to acetylenic hydrocarbons was carried out by Kucherov [96, 97], who estab-lished the structures of the products in the cases of allylene and acetylene and found that acetone and acetaldehyde, respectively, were formed on decomposition of these addition products in acid media. This reaction has achieved wide industrial application.

The composition and character of precipitates forming when nc "ylene is passed into aqueous solutions of mercuric salts de-pend on the conditions of the medium and on the actual mercury salt. The action of acetylene on a solution of mercuric nitrate



acidified with HNO3 results in a crystalline product to which the structure Hg=C(HgNO3)CHO has been ascribed [103, 393]; see also [393, 394]. This also seems to be the substance obtained in the mercuration of acetaldehyde.

The properties of this compound are best explained by the struc-ture proposed for it by Korshak and Zamyatina [395] (see below). The product of the addition of acetylene to mercuric nitrate in acetic acid has the composition C2H2N2O7Hg and its structure is probably (O3NHg)CH-CHO [395]. More work has been done on the adduct of acetylene and aqueous HgCl2 [98, 396-398], to which Biltz and Mumm ascribed the structure of tris-(chloromercuri)acetalde-hyde, C(HgCl)3CHO. There is no doubt that in these cases the addi-tion is accompanied by substitution of one of the mobile hydrogens of acetylene with mercury. In addition to the above compound, under the conditions of its preparation [77, 79, 399], and better in absolute alcohol [76], the adduct proper C2H2HgCl2 (Biginelli) is formed, for which the structure ClCH=CHHgCl has been es-tablished. The elucidation of the structure of this compound has already been mentioned. The substance is very simple to make in yields of approximately 100% by saturating with acetylene a con-centrated solution of HgCl2 in 15% aqueous hydrochloric acid [80], It is the irans-isomer, a fact which was confirmed by X-ray studies [400, 401].

Cis -chloromercurivinyl chloride, first made by Nesmeyanov and Borisov [84] by means of exchange reaction (cyclo-ClCH=CH)3Sb + HgCl2, is also obtained [87] by the combination of acetylene and mercuric chloride in the vapor phase at IOO-IlO0C.

Trans - /3-chlorovinylmercury chloride transforms into the cis-isomer in the presence of peroxides [85] (the reaction in CCl1Jor CBr4[402] is accompanied by the formation of 1,1,1,3-tetrachloro-or l , l , l-tribromo-3-chloropropylene) and under the action of ultra-violet [85].

The part of trans -chlorovinyl chloride in the Kucherov reaction has been described by Klebanskii and Titov [403] and by other authors.

Preparation of £ran.s-,3-chl<]rovinylmercury chloride [80 ] . A solution of 72 g of HgCl2

in 75 ml of hydrochloric acid is saturated in the cold with acetylene, with strong shaking. A white crystall ine precipitate appears after 40minutes. This is f i ltered off after 3 hours, washed with water and dried. Weight 25 g. An additional 23 g of HgCl2 are dissolved in the fi ltrate, acetylene again passed in f o r 3 hours, with stirring, and an additional 28 g of the product are obtained. The f i ltrate is then treated once more in the above manner with 26 g of HgCl2 and acetylene for3hours, and yields another 31.5 g of the required product. The combined precipitates are recrystal l ized from benzene; m.p. 123-124°C. The chloride can be easily converted to salts of other acids [82],

Preparation of cis-/3-chloroviny lmercury chloride [87 ] , Mercuric chloride (3 g) on glass wool is placed in a two-necked flask and maintained at 85-100°C. Acetylene is then passed in for 3 hours, and the product extracted with CCI4. Yield: 1.7 g (51%); the melting-point of the crude product 68-70°C. After several recrystall izations from petroleum ether (80-IOO0C fraction), the melting-point r ises to 77-78°C.


The mechanism of this reaction has already been discussed in this chapter.

The species obtained in this way and described as a cis-com-pound contains an admixture of a transproduct, as shown by NMR and IR spectra. A. N. Nesmeyanov and A. E. Borisov have shown that the melting point of a compound purified by prolonged repeated fractional crystallization is 58 to 59°. The data of IR spectra: un-planar vibrations of C-H characteristic of cis-compounds are 918 c m - 1 and those in the region of C=C are 1580 cm" 1 . The data of NMR spectroscopy are: 5A = 6.31, 5B = 6.94. /AB = 6.8 Hz.

The regularities of configuration conservation upon electrophilic and homolytic exchange that were established before for pure trans- and cis-compounds described in the monograph are valid also for the cis-compound purified in this way.

The data given on p. 323 for cis-, cis-di-/3-chlorovinyl mercury should be replaced by: b.p. = 76 to 78° at 0.5 mm, n^ = 1.6100; df = 2.7810. The cis -configuration was confirmed by the IR and NMR spectra.

Intermediate formation of chlorovinylmercury chloride has been reported in the HgCl2-Catalysed interaction of acetylene with ar-senic trichloride [404].

Trans-/3-chlorovinyl chloride shaken with aqueous mercuric ni-trate forms [395] the same product, C2HO4NHg2, which is obtained by the action of acetylene on aqueous mercuric nitrate.

Dimethylacetylene and diphenylacetylene add mercuric acetate, but not mercuric chloride. The former reacts with mercuric ace-tate in glacial acetic acid, giving three isomeric organomercury derivatives isolated in the form of chlorides: two geometrical isomers of a,^3-dimethyl-j8-acetoxyvinylmercury chloride, ( I ) and ( I I ) , and a structural isomer, 2-acetoxy-3-chloromercuribut-1-ene ( I I I ) [93, 94]:

CH3OOC CH3 CH3 CH3 CH2

x C = C ^ ; x C = C ^ ; CH 3 -CH-C^ CH3 HgCl CH3COO HgCl i1ctci OCOCH3

I II " H I

The conditions of obtaining each of these isomers separately have been worked out [94],

Preparation of trans-l-methyl-2-acetoxy-l -propen-1 -yl-mercury chloride [94] ( I ) . Dimethylacetyiene (1.2 g, 0.02 mole), cooled with a mixture of salt and ice, is added to a solution of 7 g (0.02 mole ) of mercur ic acetate in 25 ml of glacial acetic acid cooled to -18°C. The mixture is set aside fo r 24 hours at room temperature in a sealed ampoule which is then cooled in ice and opened. The precipitate (0.2 g ) of mercurous acetate is f i l tered off and the f i l t rate treated with saturated aqueous KCl. The precipitate is f i l -tered off and recrystal l ized f rom C C I 4 . 5.4 g (yield: 70%) of crystals with a melting-point of 140° C separate out at room temperature.

The corresponding bromide is obtained (yield: 65%; m.p. 162-163°C) by treatment of the f i l trate with saturated aqueous NaBr.



Preparation of eis-l-methyl-2-acetoxy-l-propen-l-yl-mercury chloride [94] (II). The same quantities of the starting products after 24 hours of standing are heated for 2 hours at 56°C. Mercurous acetate (0.3 g, 4.5%) is f i l tered off and the f i l trate treated as before. The precipitate is recrystal l ized from a 2:1 mixture of ligroine and benzene. The precipitating crystals are f i l tered off and recrystal l ized twice from the same sol-vent; m.p. 140°C. Yield: 0.4 g (4.4%). Partial evaporation of the fi ltrate gives needle-like crystals; m.p. 95-96°C after recrystall ization from ligroine (b.p. 110- 130°C), which do not change their melting-point on further recrystallizations. Yield: 3.66 g (40.4%),

Preparation of l-methyl-2-acetoxy-2-propen-l-yl-mercury chloride [94] (III ) . Di-methylacetylene (2.2 g, 0.04 mole ) is added to a solution of 13 g (0.04 mole ) of mercuric acetate in 39 ml of glacial acetic acid cooled to -18°C. The products of the reaction are heated for 2 Vq hours at 76°C in a sealed ampoule. The products are isolated under the conditions described above for compounds ( I ) and ( I I ) . The precipitate of mercurous acetate amounts to 1 g (9.5%). Twofold recrystallization of the chloride gives a material melting at 130°C, in a yield of 2.4 g (17%).

The bromide melts at 127-128°C.

The addition of Cl and HgCl to l,4-dichlorobut-2-yne has been carried out by treating the latter with a saturated solution of HgCl2

in saturated aqueous NaCl [138],

Preparation of l,2,4-trichloro-3-chloromercuribut-2-ene [138]. l,4-Dichlorobut-2-yne (1 g) is mixed with 10 ml of a saturated solution of HgCl2in saturated aqueous NaCl and the mixture set aside for 48 hours (with frequent shaking). The crystalline precipi-tate is then f i l tered off and washed with water. The f i ltrate is saturated with HgCl2 and set aside for another day, after which the precipitated crystals are added to the main portion. Recrystall ization from aqueous methanol gives 2.4 g (yield: 77%) of colorless fine leaflets, m.p. 85-86°C. The substance dissolves readily in acetone and alcohol, dissolves in benzene and chloroform and is insoluble in water.

It has been suggested [405] that an intermediate addition of HgCOOC H3-groups and the formation of a ^-complex occurs in the mercury-catalysed addition of mercuric acetate to hex-3-yne.

Diphenylacetylene adds mercuric acetate in glacial acetic ace-tate (2Y2 hours, at a temperature not exceeding 96°C) with the f o r -mation of only one compound which appears to be the cis-isomer [93, 406, 407]. According to other data, both cis- and fraws-isomers are formed in this reaction, the latter being due to a rearrangement of the initially formed cis-compound.

On reaction with aqueous solutions of mercuric salts, the mono-substituted lower acetylene homologs form amorphous products which are converted to ketones by the action of acids; thus methyl-acetylene yields acetone [96, 97].

Biltz and Mumm [98] proposed the formula CHgCOC(HgCl)3, for the precipitate obtained from methylacetylene and HgCl2, and the formula (ClHg)3CCOC2H5, trichloromercurimethyl ethyl ketone, f o r the precipitate f rom acetylene and HgCl2, which gives methyl ethyl ketone under the action of acids [98],

The product of the addition of aqueous mercuric nitrate to acety-lene, once obtained by Hofmann [98, 396, 409] is believed [395] to have the structure

C H = C—HgNO3

I 1 O Hg


Preparation of acety Ipropiony lmethane from dimethyl acetylene in the presence of a mercuric salt L4101. The above product is obtained by heating a mixture of a solution of dimethylacetylene in ethanol with alcoholic HgC l 2 f o r 6 days at 100°C in a sealed tube; b.p. 158°C.

The action of mercuric acetate in glacial acetic acid at 70-100°C on the higher acetylene homologs suchashept-l-yneand oct-l-yne, and also on phenyl acetylene (accompanied by replacement of the mobile hydrogen at the triple bond by mercury) consists in addition according to the scheme [101]:

- C = C H + 3 H g (CH 3 CO 2 ) 2 + H 2 O - - C = C ( H g O 2 C C H 3 ) 2 - f 3 C H 3 C 0 2 H

I O H g O 2 C C H 3

Kinetic studies have shown that diphenylacetylene in water prac-tically does not add HgCl2 in the presence of LiCl in methanol, nor in the presence of NaCl [411]. The reaction of phenyl acetylene with mercuric chloride in a sealed tube at 50°C proceeds explosively [411].

The action of mercuric acetate at 60-700C on vinylacetylene CH2=CH-C = CH or on the vinylacetylide (CH2=CH-C = C)2Hg (obtained from vinylacetylene and K2HgI4 or mercuric acetate in acetic acid at room temperature) gives rise to the compound

C H 2 = C H - C = C ( H g O 2 C C H 3 ) 2

O - H g O 2 C C H 3

which forms methyl vinyl ketone on being treated with hydrochloric acid; the action of bromine converts it to tribromomethyl vinyl ketone CH2=CHCOCBr3 [412],

Butadienyl esters CH2=CRCH=CHOAc are formed from the inter-action between acids and compounds CH2=CR-C = CR' (where R and R' = H, aryl, or alkyl) in the presence ofmercury salts [413]. Ace-tylene and alkylacetylenes give acetals with alcohols in the presence of mercury salts [414, 415]. The latter also catalyze the formation of cyclic acetals from alkylacetylenes and glycols [416] (see also [417]).

A product withstructureC6H5CCl=C(HgCl)-C(OC2H5)=CH-CH3was also obtained by the action of aqueous-alcoholic HgCl2 on phenyl-methyIdiacetylene C6H5C = C-C = CCH3 [418].

Nesmeyanov et al. have prepared several other monomercury derivatives of unsaturated hydrocarbons, containing the mercury on the olefinic carbon: propenyl [419], isopropenyl [420], styryl [421], stilbenyl [95] and vinyl [422] derivatives of mercury, via the corresponding organolithiums and organomagnesiums (see Chapter 2) and also via the organometallic compounds of thallium and tin (see Chapter 9).

The retention of the geometrical configurations of isomers during the homolytic and electrophilic reactions of these organo-mercuries has been mentioned earlier in this chapter, but see also Chapters 13 and 14.



A d d i t i o n o f M e r c u r i c S a l t s t o A c e t y l e n i c A l c o h o l s

Acetylenic alcohols readily form adducts with mercuric chloride [138]. Owing to their lability, they are obtainedfrom saturated solu-tions of HgCl2 in saturated NaCl. The action of such a solution on propargyl alcohol, dimethylethynylcarbinol, butyn-l,4-diol and 2,5-dimethylhex-3-yn-2,5-diol gave 2-chloro-3-chloromercuriprop-2-enol, 2-methyl-3-chloro-4-chloi'omercuribut-3-en-2-ol, 2-chloro-3-chloromercuribut-2-en-1.4-diol and 2,5-dimethyl-3-chloromer-curihex-3-en-2,5-diol, well-crystallizing substances with clearly expressed quasicomplex properties [138].

Addition of mercuric chloride to propargyl alcohol [138] , Propargyl alcohol (2.5 g as the monohydrate, b.p. 97-98°C) is mixed with 20 ml of a saturated solution of HgCl2

in saturated NaCl. The mixture becomes turbulent and crystal l izes within a few minutes with some evolution of heat. After an hour the crystals are f i l tered off, washed and dried in air. Recrystall ization from aqueous methanol or benzene gives fine colorless needles, m.p. 104-105°C. The yield of 2-chloro-3-chloromercuriprop-2-enol is 6.0 g (55%).

The adduct of HgCl2 and the methyl ether of propargyl alcohol was obtained similarly by shaking the ether with a saturated solu-tion of mercuric chloride in saturated NaCl [411].

Mercuric acetate in acetic acid and but-2-yn-l-yl acetate give (after precipitation with KCl) the adduct l,3-diacetoxy-2-chloro-mercuribut-2-ene [423].

Let us now turn to the addition of mercuric salts to unsaturated glycols. The action of HgCl2 (1-6 hours of boiling in alcohol) on dimethylphenylphenylethynylethylene glycol leads to a cyclic pro-duct [424]; in contrast, mercuric acetate (2%-4 hours at 890C) gives a product having an open structure [425]:

CH3 C6H5

) C — C < CH3 Qj_j QPJCsCC6H5

HgCl5/ \ H g (CH3CO1)2

C6H5C = C-HgCl C6H5

H3Cv X6H5 CH3x x C C< xC-C=C-CO-C6H6

HsC/ \ / XOH CH3/ I I O OH HgOCOCH3

Other ethynylpinacones also behave differently with respect to mercuric chloride and mercuric acetate. Thus, diphenylmethyl-phenylethynylethylene glycol adds only to mercuric acetate (3 hours in the cold), giving a product with an open structure [426]; it does not form a mercury-containing compound with HgCl2.

Secondary-tertiary glycols (l,4-diphenyl-2-methylethynyl glycol [427], 5,5-dimethyl-1,2-diphenylhex-3-yn-1,2-diol [428], 2-methyl-4-phenylbut-3-yn-l,2-diol [429], 1,2,4-triphenylbut-3-yn-l,2-diol [430] and 3-methyl-5-phenylpent-4-yn-2,3-diol [430]) give with


mercuric chloride /3-mercurated substituted furans as a result of the elimination of HCl and H2O followed by ring closure.

Synthesis of 2,5-diphenyl-4-methylfuryl-3-mercury chloride [427]. A mixture of 3 g of l ,3-diphenyl-2-methy lethynyl glycol and 3.25 g of mercur i c chloride is set aside f o r 3 days at room temperature. The precipitate is washed severa l t imes with alcohol and then recrys ta l l i z ed f rom benzene. Y ie ld : 4.9 g (87%); m.p. 237-238°C.

A d d i t i o n o f M e r c u r i c S a l t s t o A c e t y l e n i c K e t o n e s

The addition of mercuric chloride to phenylethynyl methyl ketone gs.ve [139] l-phenyl-l-chloro-2-chloromercuribut-l-en-3-one, con-taining the system C1-C = C-C = 0

I HgCl

in which the Hg-C bond is conjugated at the same time with the Cl-C and the C=O bonds. Because of this conjugation, the com-pound is labile and has clearly expressed quasicomplex pro-perties. The substance eliminates HgCl2 not only in the presence of reagents which combine with it but also (to an appreciable extent) on recrystallization from ether.

Addition of mercuric chloride to phenylethynyl methyl ketone [ l 3 9 ] , A 5-g portion of the above ketone is shaken f o r 4 hours with 100 ml of a saturated solution of HgCl 2 in saturated NaCl . A crysta l l ine precipitate appears within a few minutes. The mater ia l is f i l t e red of f , washed with water and dried over CaC l 2 . T h e f i l t rate is saturated with HgCl 2 , treated with 5 g of the ketone and the above operations repeated. Dry , combined precipitates are worked up with two smal l portions of absolute ether and dr ied in vacuum. The yield of l - pheny l - l - ch l o ro -2 - ch lo romercur ibu t - l - en -3 -one is 28.0 g (97%). Rec r y s -tall ization f rom ether g ives f ine co lo r l ess needles, m.p. 112-113°C (with decomposition).

A d d i t i o n o f M e r c u r i c S a l t s t o A c e t y l e n i c A c i d s

The simpler products of the addition of mercuric salts to the lower acetylenic acids are obtained smoothly, and in good yields, by the interaction of such acids or their esters with a saturated solution of mercuric chloride in saturated aqueous NaCl [140], In the case of the lower homologs the reaction is very rapid and is completed within 1-2 hours. This method has been used to obtain the adducts of HgCl2 with propiolic [140] and tetrolic [140, 431] acids and their esters [140], and also with the esters of phenyl-propiolic and acetylenedicarboxylic [140] acids. HgCl enters the a- and Cl the / 3 - p o s i t i o n with respect to the earbonyl group, i.e. the addition is anti-Markovnikov, as is usually observed in the case of unsaturated acids. The adducts are typical quasicomplexes, eliminating HgCl2 under the action of reagents which combine with it even more readily than /3-chlorovinylmercury chloride.

The adducts of mercuric chloride and the esters of acetylenic acids are slightly more stable.

Preparation of a-chloromercuri-^-chloroacrylic acid [ l 4 n ] . Prop io l i c acid (1.00 g ) is



mixed with 10 ml of a saturated solution of HgCl2 in saturated NaCl. The product cry-stallizes after the mixture has been scratched for a few minutes with a glass rod. After 2 hours the crystals are fi ltered off, washed with a little water and dried in a desiccator over C a C l 2 . Recrystallization from water gives fine, shiny, white needles; m.p. 178-179°C (with decomposition). Yield: 4.45 g (91%).

Preparation of methyl chloromercurifumarate [140]. A 5 .00-g portion of the dimethyl ester of acetylenedicarboxylic acid is mixed with 30 ml of a saturated solution of HgCl2

in saturated NaCl and the mixture shaken vigorously several times. Crystals appear after a few hours. After 3 days, the material is fi ltered off, washed with water and dried on a porous plate. On being saturated with HgCl2, the fi ltrate produces another crop of crystals. Recrystallization from methanol gives colorless needles, m.p. 145-145.5°C; yield: 10.72 g (73%).

The products of the addition of mercuric chloride to the methyl esters of propiolic, phenylpropiolic and acetylenedicarboxylic acids have also been made by mixing solutions of the reagents in the presence of methanolic LiCl [411]. In the case of the acetylenedi-carboxylic acid ester, acetic acid was also added to the system.

Kinetic studies of this reaction [411] showed that the rates of addition to HgCl2 decrease in the order

H C = C - C 0 2 C H 3 > C H 3 O 2 C - C S C - C 0 2 C H 3 > C 6 H 5 - C = C - C 0 2 C H 3 > C 6 H 5 - C = C - H

H — C s C — C H 2 C H 3

so that mercuric chloride practically does not add to the last two compounds of this series.

The mean rate constants of the addition of mercuric chloride at 50°C, in methanol, in the presence of lithium chloride, are calcu-lated from

[ " f C ' 2 1 = K i [ R - C s C - R ] [HgCI 2 ] [ L iC l ] 2

—3 — 1 and are equal to K1 = 0.54 mole l itermin for methyl propiolate and Ki =0.11 mole -3 liter min -1 for the acetylenedicarboxylic acid ester [432].

The higher monocarboxylic acetylenic acids and their esters H C = C ( C H 2 ) 7 1 C O O R (n = 0, 2, o r 8) a n d C H 3 ( C H 2 ) M C = C ( C H 2 ) N C O O R (m = 0, 5, or 7 and n =0, 7, or 11), and also ethyl phenylpropiolate and the hydroxy-acid CH3(CH2)3CH(OH)CH2C=C(CH2)7COOH add to mercuric acetate in acetic acid at 70-100°C according to the scheme [99-101]:

— C s C - + 2 Hg(O2CCH3 )2 + H 2O - C = C - H g O 2 C C H 3 + 2CH3COOH I

OHgO2CCH3

In addition to the above reaction, the acid HC=C(CH2)8COOH and its ethyl ester replace the mobile acetylenic hydrogen by the group HgO2CCH3:

I I H C s C (CH3CO2Hg)2C = C - O H g O 2 C C H 3

Preparation of the ethyl ester of 9,10-diacetoxymercuriketoundeeenoie acid [99], A solution of 70 g of HgO in 500 ml of glacial acetic acid is added to 33 g of the ethyl ester of 9,10-undecynoic acid and the mixture heated for 5 hours on a water bath at 70-100°C.


Mercurous acetate (about 4 g ) is f i l t e red off and the f i l t ra te diluted with water. An amber-co lored oil separates out, which so l id i f ies on shaking with water. The product is r e -crysta l l i zed f r o m 75% acetic acid. Y ie ld : 95 g.

9-Octadecynecarboxylic acid shaken for 4 hours at 70-80°C in acetic acid solution with mercuric acetate gives 10(9)-acetoxy-9(10)-acetoxymercuri-9-octadecenoic acid [433]. The compound CH3O2C(CH2)9C = C-C = C(CH2)9CO2CH3 gives with methanolic mercu-ric acetate the adduct [433] CH3O2C(CH2)9C(HgO2CCH3) = C(OCH3) C(HgO2CCH3) = C(OCH3)(CH2)9CO2CH3.

e) Addition of Mercuric Salts to Cyclopropane Derivatives

The reaction of mercuric salts with cyclopropane hydrocarbons, discovered by Levina et al., leading to cleavage of the cyclopropane ring and addition of the HgX- and OR- residues to the ends of the three-membered chain

(R = H or Alk) is only formally analogous to the additions of mercu-ric salts to the olefins. The products have no quasicomplex proper-ties and are fully stable organomercury compounds. Thereaction is carried out in water or alcohol, with cooling, and leads to the for -mation of y-mercurated alcohols or their ethers.

The ring opens across the most polarized bond, between the most and the least substituted carbon atoms. The addition follows Markovnikov's rule. The reaction has been applied to 1,1,2-tri-methylcyclopropane [434], 1,1,2,2-tetramethylcyclopropane [170, 435], l,l,2-trimethyl-2-ethylcyclopropane [436], phenylcyclopro-pane [437] (the mercury salt of trinitromethane in methanol has also been added to phenylcyclopropane; the adding elements were -HgC(NO2)3 and -OCH3 [227]), p-anisyl- and p-tolylcyclopropane [438], methyl- and 1,1-dimethylcyclopropane [439] and 1,1-dimeth-yl-2-alkylcyclopropanes (alkyl = C2H5, iso-C3H7, iso-C4Hg) [440] (the addition to the methylated cyclopropanes occurs under more vigor-ous conditions - after 20 hours of shaking on a rocker for the f irst and 10-12 hours of shaking for the others, at room temperature). It has been applied to the following bridged bicyclic hydrocarbons: 1,2,3-trimethyl- [411], 1,3,5,5-tetramethyl- [422] and 1,2-dimeth-yl-3-ethyl- [441] (0,l,3)bicyclohexane, to spiro-(2,4)-heptane [443], and to p-cyclopropylcumene [208].

Preparation of 3-hydroxy-2,2,3-trimethylbutylmercury acetate [435 ] , Te t ramethy l -cyclopropane (12.8 g ) is added to a f i l t e red solution of 41.6 g of mercur i c acetate in 150 ml of water and the mixture set aside f o r 6 days at -5 °C in a stoppered f lask, with


Ri R» + HgX2 + ROH ^ ROCR1R2CR3R4CH3HgX

R2 R3


periodic shaking. Some precipitate separates out at the end of the reaction (disappearance of the hydrocarbon layer and of mercuric ions). Four-f i f ths of the volume of water are evaporated off under vacuum (5 mm) from the solution and the residue gives, on cooling, white crystals which are subsequently recrystal l ized f rom heptane. Yield: 64%; m.p. 69-70°C. In alcohol, the reaction is complete within 3 days.

Semi-kinetic studies of the reaction of cyclopropane derivatives with mercuric acetate in methanol showed that electron-donating substituents, tending to yield their electrons by a conjugative mechanism, increase the reactivity of the cyclopropane ring towards the electrophilic mercuric acetate; conversely, electron-attracting groups in the ring decrease this reactivity. Thus, the cyclopropane hydrocarbons can be arranged in a series showing the reactivity with respect to mercuric acetate (the numbers show the percentage of hydrocarbon that reacted after 3 hours): phenylcyclopropane (71), trans-1,2-dimethylcyclopropane (48.5), trans -l-methyl-2-ethylcyclopropane (18.5), ethylcyclopropane (3.5), isopropylcyclopropane (1.5).

The following are very much less reactive (the numbers now indicate the percentage of hydrocarbon that reacted after 21 hours): trans -1,2-diphenylcyclopropane (3.8), cis-l,2-diphenylcyclopropane (3.5), 1,1-diphenylcyclopropane (2.5). Methyl cyclopropyl ketone does not react under theses conditions [444].

The following compounds are more reactive than phenylcyclo-propane (the relative reaction rates are given in parentheses [445]:

The crystal structures of the addition products obtained from mercuric salts and cyclopropane derivatives have been studied by means of X-rays [446, 447],

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V X ( 2 . 5 )

/ ^ - C 0 H 5 (1)

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CHAPTER 7

Synthesis of Organomercury Compounds by the Diazo Method

The diazo method of synthesizing aromatic compounds of mercury, proposed by Nesmeyanov [1, 2], is both convenient and universal. It consists in the decomposition of the double salts of aryldiazon-ium halides and mercuric halides by means of copper powder or copper bronze, in acetone, ethyl acetate, alcohol, or water [1]:

ArN2X-HgX2 + 2Cu ->• ArHgX + 2CuX + N2

With an excess of the copper and in the presence of aqueous ammonia the product is the fully substituted organomercury de-rivative [2]:

2ArN2X-HgX2 + 6Cu + 6NH3-» Ar2Hg + 6CuX-NH3 + 2N2

The yields in these two reactions are usually 45-75% of the theo-retical value, and occasionally may be even higher.

If the aromatic radical contains strongly electron-attracting substituents (nitro, carboxyl, sulfonic acid groups, two atoms of chlorine), the reaction must be conducted with strong cooling and particularly careful stirring [3].

The advantage of the diazo method over the methods involving the use of organomagnesium compounds or sodium amalgam is the possibility of obtaining substances with substituents such as NO2, COOH, SO3H, or COOCH3, which are not inert to Grignards or to sodium. In contrast to mercuration, the diazo method results in compounds free from isomers and substituted in the selected position.

The diazo synthesis of organomercury compounds (and in general of organometallic derivatives) both through the decomposition of the double salts ArN2X1HgX2 in the presence of a reducing agent and through other variants of the method (see below) appears to proceed by a homolytic mechanism. The free metal (the reducing metal in the case of the decomposition of double diazonium salts)

228

SYNTHESIS BY THE DIAZO METHOD 229

acts as a reducing agent on the diazonium cation and converts it into the diazo form which decomposes homolytically with the formation of an aryl radical. The aryl radical then arylates the metal:

A r — N + = N : + M e - » Ar:N = NrMe+-* N 2 + A r : + Me+

This action of metals on the decomposition of diazonium salts is confirmed by the formation of side products of homolytic cleav-age. Thus, the decompositions of aryldiazonium fluoroborates in nitrobenzene or benzoic esters, in the presence of copper powder [4] or cadmium, zinc, or silver powders [5], give rise to mixtures of mainly o- and ^-nitrobiaryls and o- and p-diphenylcarboxylic acids (after hydrolysis), respectively:

NO2 NO2 NO2

I

C8H5N2BF4 + ^ J j C u (Cd. Zn. Ag ) [[ J ^ j j - C 0 H 5

CeH5

COOAlk COOH COOH I I I

C 6 H 5 N 2 B F 1 + Q c " ( C d - Ae> OH;Q + Q-C 6H 5

I C6H5

In the absence of metals, aryldiazonium fluoroborates decompose heterolytically with the formation of an aryl cation. The latter enters the aromatic rings containing m-directing groups (nitro-benzene and the alkyl benzoates) into a position meta to those substituents, giving m-nitrobiaryls [6-8] and w-phenylbenzoie esters; the esters also undergo transesterification [6, 8, 9] (Nesmeyanov and Makarova):

C6H5N2BF4 +

NO2 NO2

I

C6H5

COOAlk COOAlk I I

C6H5N2BF4 + Q " Q x +CeH5COOC6H5

C6H5 (see also [10]).

Ascribing a heterolytic mechanism to the reaction

P-XC6H4SbCl4-C6H5N2Cl + Fe - p-XC6H4 (C6H5) SbCl3 + N2 + FeCl2



on the basis of the observed increase in its rate with increasing electron-donor properties of the substituent X, Reutov [11] pro-posed that the synthesis of other organometallic compounds by Nesmeyanov's reaction also proceeds by a heterolytic mechanism.

For the mechanism of the preparation of organomercuries by the diazo method, see also [12-14].

Spectra of the double diazonium salts with mercuric chloride have been studied in the visible region, in ultra-violet [15] and in the infra-red [16].

Diazo synthesis of organomercury compounds involves two steps: (1) preparation of the double salt of mercuric chloride (or some

other mercuric halide) and aryldiazonium chloride (or some other halide);

(2) decomposition of this double salt with copper.

a) Preparation of Arylmercury Halides

P r e p a r a t i o n o f t h e D o u b l e S a l t s o f A r y l d i a z o n i u m C h l o r i d e s a n d M e r c u r i c C h l o r i d e

This operation is carried out in one of the following ways. (1) One mole of an amine (if the amine is solid but has a low

melting-point, it is preferable to fuse it) or its hydrochloride is treated with 300 ml of conc. HCl and heated, if necessary, to ensure full conversion in the the salt. After being cooled, the mixture is treated with 300 g of finely crushed ice and diazotized, with vigorous stirring and occasional external cooling, by rapid addition of a solution of 70 g of sodium nitrite. The diazo solution is immediately stirred into a solution of 270 g of HgCl2 in 270 ml of conc. HCl to which had been added 300 g of ice. The precipitated double diazonium salt is filtered off, washed with water, alcohol and ether, and then dried in air. This method is recommended in the usual cases and very often gives an 80-90% yield of very pure diazonium salt.

(2) Finely crushed ice (300 g) is added to a solution of 270 g of HgCl2 in 300 ml of conc. HCl, cooled to -10 to -15°C and the mixture is treated, with energetic stirring and cooling (snow and salt), with a saturated solution of sodium nitrite taken in approxi-mately 20% excess. A cooled ethereal solution of l m o l e o f t h e amine (at least three times the amount) is then poured in, with vigorous shaking and external cooling. Shaking and stirring is continued for several minutes and the precipitate ground with a glass rod against the wall of the vessel, filtered off and washed as above. This procedure is used in the case of relatively soluble or low-melting double salts, e.g. carbalkoxy-substituted compounds, since the first method then gives fairly lowyields of the sometimes liquid products.


(3) The amine hydrochloride is dissolved in the minimum volume of 95% alcohol, treated with 2-3 drops of conc. HCl and diazotized with a small excess of amyl nitrite. The diazo solution is poured into a solution of an equimolecular amount of HgCl2 in a volume of ether exceeding 3-4 times the required volume of the alcohol. The precipitated double salt is filtered off and washed with alcohol and ether. The yield of the double salt is quantitative, but large amounts of solvents are required and the procedure involves work with large volumes. The method is used in the case of expensive amines.

If possible, the diazonium salts should be made up on the day of the synthesis, but they can be stored if they are not left in a closed vessel and preferably if they are spread out into a thin layer. Under these conditions, it becomes possible to work safely with amounts of 100 to 1000 g of the double salts.

P r e p a r a t i o n o f t h e C o p p e r P o w d e r

Zinc dust (60 g) is sieved into a cold solution of 250 g of copper sulfate in 1.5-2 liters of water. The suspension is then carefully stirred and filtered. The powder is washed with water, alcohol and ether, and is finally dried in air.

The copper should not be dark, but have a clean color. Darkened powder can be regenerated by washing with dil. HCl and then with water, alcohol and ether as before.

Hg, Zn, SnCl2 and other reducing agents can be used in place of the copper for the decomposition reaction [17-22], but copper gives the best results.

D e c o m p o s i t i o n o f D o u b l e D i a z o n i u m S a l t s i n O r g a n i c S o l v e n t s

The double salt is added in small portions to a cooled (snow and salt) and mechanically stirred suspension of the copper powder (50% excess) in a solvent (generally acetone) taken in an amount of 30-50 ml for each 10 g of the salt. The temperature should pref-erably be below -5°C throughout the decomposition. The solutions are then evaporated and the solid precipitate is washed with a little ether. The organomercury salt is extracted from this mate-rial with a suitable solvent (generally benzene, xylene, or acetone) and is recrystallized, either from one of the above solvents or from chloroform or alcohol. This method has given good yields of the organomercury derivatives of the following compounds: benzene [1, 17, 23-27]; benzene homologs (o- [1, 28, 29], m- [28-30] and p- [1, 26, 28] tolyl-, 2, 5-xylyl- [31] mercury halides); naphthalene (a - [1, 28], /3- [1, 32] naphthylmercury chlorides);



biphenyl [33, 34], triphenylmethane and triphenylearbinol [35]; halogenated benzenes (o- [36], p- [1, 27, 37] ehlorophenyl-, 2,5-dichlorophenyl- [1, 3], o- [27], p- [1, 27] bromophenyl-, m- [36], p-iodophenyl- [1] mercury chlorides and o-iodophenylmercury chloride [38]); nitrated benzenes ( o- [3], m- [3], p- [3, 26] nitro-phenylmercury chlorides and2-chloromercuri-4-nitrotoluene[39]); m -trifluoromethylphenylmercury chloride [29, 40]; phenolic ethers ( o - [1, 41, 42], p- [41, 42] anisyl-, o- [41], p- [1, 41] phenethyl-mercury halides, 2- and 4-chloromercuridiphenyl ether [41], 2-chloromercuri-4-methyldiphenyl ether [43]); phenols (m- [44] and p - [1] hydroxyphenylmercury chlorides); carboxylic acids ( o -chloromercuribenzoic acid [3]); carboxylic acid esters (methyl [1, 30] and ethyl [30] esters of o- [1, 30, 36], m- [30] and p- [30] chloromercuribenzoic acids [30]); benzenesulfonic acid [3] and its derivatives [45]; anthraquinone (monochloromercuri derivative from a-aminoanthraquinone [46, 47] and bis-chloromercuri de-rivatives from 1,5-diaminoanthraquinone [48]); stilbene [49]; thio-anisole [50]; naphthoxazine [51] andnaphthothiazine [52] derivatives; benzophenone [63]; thiazole [STf]. Relatively worse results were ob-tained with jS-aminopyridine and products of its substitution [53],

The double salt can also be decomposed in water, with vigorous stirring [36], The yields are as high as when the reaction is carried out in acetone, except in the case of nitro-groups and groups con-taining similar substituents, requiring greater cooling, which cannot be achieved in water.

Synthesis of phenylmercury chloride [ l ] . Aniline (23 g), 100 ml of conc. HCl, 300 ml of water, 18 g of NaNO2 and 68.5 gof HgCl2 in 70 ml of conc. HCl are mixed, treated with 70 g of ice and processed by method (1) (see above). The product is 75 g of the double salt of benzenediazonium chloride and mercuric chloride; 10 g of this salt and 3 g of copper in 40 ml of acetone give (acetone extraction) 3.9 g (yield: 51%) of phenylmercury chloride, m.p. 258°C. It is possible to raise the yield to 77% by carrying out the decomposition below -IO0C [12],

Synthesis of p-ethoxyphenylmercury chloride [ l ] . The doable salt of p -ethoxybenzene-diazonium chloride and HgCl2 precipitates out within 5 minutes, in a yield of 5.2 g, after processing by method (1) a mixture of 4.28 g of p-phenetidine hydrochloride, 20 ml of HCl, 80 ml of water, 2.2 g of NaNO2 and 8.1 g of HgCl2 in 15 ml of conc. HCl with the addition of 15 g of ice.

A 3.5-g portion of this salt and 1 g of copper in 10 ml of alcohol give (chloroform ex-traction) 2.1 g (77%) of />-ethoxyphenylmercury chloride, m.p. 249-250°C.

Synthesis of p-tolylmercury chloride [ l ] . The double salt of P-tolyldiazonium chloride and HgCl2 is obtained, in a yield of 75 g, by processing by method (1) a mixture of 32.1 g of p-toluidine, 150 ml of conc. HCl, 150 g of snow, 22 g of NaN02 and 81 g of HgCl2 in 80 ml of conc. HCl and 80 g of ice.

A 6.5-g portion of this salt and 1.8 gof copper in 30 ml of acetone give (acetone extrac-tion) 3.3 g (yield: 66%) of p-tolylmercury chloride, m.p. 238-239°C.

Synthesis of o-tolylmercury chloride [ l ] . The double salt of o-tolyldiazonium chloride and HgCl2 is obtained in a yield of 23 g by processing by method (1) a mixture of 10.7 g of o-toluidine, 40 ml of conc. HCl, 40 g of ice, 7 g of NaNO2 and 27 g of HgCl2 in 30 ml of conc. HCl and 30 g of ice.


A 4.25-g portion of this salt and 1.2 g of copper in 20 ml of alcohol g i ve (acetone ex-traction) 2.15 g (66%) of o - to ly lmercury chloride, m.p. 143°C.

Synthesis of p-chlorophenylmercury chloride [ l ] . The double salt of p-chlorobenzene-diazonium chlor ide and HgCl 2 is obtained in a yie ld of 28.7 g by processing by method (2) 10 g of p-chloroani l ine in 40 ml of ether and 21.3 g of HgCl 2 in 30 ml of conc. HCl, with the addition of 30 g of ice and 7 g of NaNO 2 .

A 16-g portion of this salt and 4.3 go f copper in 50 ml of acetone g i ve (acetone extrac-tion, recrysta l l i zat ion f r om benzene) 5.6 g (46%) of p-chlorophenylmercury chloride, m.p. 240°C.

Synthesis of a-naphthylmercury chloride [ l ] , They e l l owdoub l e sa l t o f a-naphthalene-diazonium chlor ide and HgCl2 is obtained in a yie ld of 31 g by mixing 14.3 g of a-naphthyl-amine, 10 ml of conc. HCl, 100 g of i ce and 9 g of NaNO 2 with 27 g of HgCl2 in 40 ml of conc. HCl and 40 g of ice.

A 4.6-g portion of this salt and 1.6 go f copper in 30 ml of acetone g ive (acetone extrac-tion) 2.1 g of a-naphthylmercury chloride, m.p. 191°C. Synthesis of the /3-isomer wil l be found in [32],

Synthesis of ^-hydroxy phenylmercury chloride [ l ] . T h e double salt of p -hydroxy-benzenediazonium chloride and HgCl 2 is obtained in a y ie ld of 4.0 g by processing by method (3) a mixture of 1.45 g of p-aminophenol hydrochloride in 20 ml of alcohol, with the addition of 1.5 g of amyl nitr ite and 2.7 g of HgCl 2 in 60 ml of ether.

A 3 -g portion of this salt and 1 go f copper in 10 ml of acetone g ive (acetone extract ion) 1.3 g (56%) of p-hydroxyphenylmercury chloride, m.p. 226-227°C.

Synthesis of p-carhethoxy phenylmercury chloride [ 30]. The double salt of p-carbeth-oxybenzenediazonium chloride and HgCl2 is obtained in ay ie ld of 101 g f r om a mixture of 45 g of ethyl p-aminobenzoate, 170 ml of 1:5 HCl, 18 g of NaNO 2 , 68 g of HgCl2 in 68 ml of conc. HCl and 70 g of ice.

A 20-g portion of this salt and 5 g of copper in 50 ml of acetone cooled to - IO 0 C g ive (ethyl acetate extract ion) 7 g (44.7%) of p-carbethoxyphenylmercury chloride. Recrys ta l -l ization f r om benzene; m.p. 223°C.

To obtain good yields of organomercuries containing strongly negative substituents in the aromatic ring (-NO2, -SO3H1 -COOH, two Cl atoms), the decomposition with copper must be accompanied by vigorous stirring (Witt stirrer) and must be conducted in acetone or ethyl acetate (the latter solvent in the case of o- and p-nitro-phenylmercury chlorides); the temperature must not rise above -IO0C. Stronger cooling (-70°C) is required only in the preparation of o-chloromercuribenzoic acid [3].

Under these conditions, satisfactory yields have been obtained of o-nitrophenylmercury chloride (42%), ^-nitrophenylmercury chlo-ride (56%), m-nitrophenylmercury chloride (60%), o-chloromer-curibenzoic acid (39%), p-chloromercuribenzenesulfonic acid(30%) and 3,5-di(chlorophenyl)mercury chloride (32%) [3].

In the case of the carboxy- and sulfo-compounds, which do not give double salts of the required type, the decomposition is carried out by adding to the suspension of copper powder an equimolecular mixture of the diazonium salt and HgCl2 in the solid state with the same solvent as that of the copper suspension. Extreme care must be taken, since such mixtures are very explosive.



Preparation of O- (or p-) nitrophenylmercury chloride [ 3 ] . O-Nitraniline (60 g ) is dissolved in a mixture of 150 ml of conc. HCl and 75 ml of water heated to 90°C. After the mixture has been cooled to 25°C, 250 gof snow are added. The temperature fa l ls to -20°C. The solution is then stirred vigorously with a Witt s t i r rer and a solution of 36.5 g of NaNO2 in 72 ml of water quickly poured in. The precipitate appearing on cooling rapidly redissolves. After 1-2 minutes, the diazo solution is treated with 136 g of NgCl 2 in 80 ml of conc. HCl. Rapid precipitation takes place and the whole liquid sets to a pasty mass. The precipitate is f i l tered off and washed with a minimum volume of water and then with alcohol and ether. Yield: 190 g.

A 20-g portion of the double salt is added in small portions to a suspension of 8.4 g of copper powder in 100 ml of ethyl acetate, cooled to -20°C and vigorously st irred with a Witt s t i rrer , at such a rate that the temperature remains below -15°C. At the end of the addition the mixture is stirred for a further 30 minutes. The precipitate is f i l tered off and extracted with hot acetone. Acetone and ethyl acetate are evaporated off and the com-bined precipitates washed with ether and recrystal l ized f rom acetone. Y ie ld: 6.5 g (41%); m.p. 185°C. The p - i s o m e r is prepared under the same conditions ( from 69 g of p -nitraniline, giving 144 g of the double salt). A 20-g portion of the double salt is decom-posed in ethyl acetate to g ive 8.6 g (55%) of the desired product. Recrystall ization from nitrobenzene; m.p. 265°C.

Preparation of m-nitrophenylmercury chloride [ 3 ] . m-Nitroaniline (69 g) is dissolved in 150 ml of conc. HCl and 150 ml of water heated to 90°C. The solution is mixed with 500 ml of water and cooled to 7°C. A solution of 35 g of NaNO2 in 70 ml of water is then poured in with energetic stirring. The originally precipitated amine salt dissolves. A solution of 136 g of HgCl2 in 136 ml of conc. HCl is poured in. The system sets to a pasty mass. The precipitate is f i l tered off and washed with a small amount of water and then with alcohol and ether. Weight 210 g. The salt is decomposed under the same condi-tions as f o r the O- and p-isomers, but acetone is used in place of the ethyl acetate. A 20-g portion of the salt gives 9.2 g (59%) of the desired product; m.p. 235°C.

Preparation of p-chloromercuritriphenylcarbinol [35] . Finely ground p-aminotr i -phenylcarbinol (13.75 g ) in a mixture of 40 ml of water and 5 ml of HCl are treated with 20 ml of conc. HCl. A red, f ine precipitate of the salt appears and is diazotized with 5 g of NaNO2 in 15 ml of water. The diazo solution is f i l tered and poured into a solution of 25 g of HgCl2 in 25 ml of conc. HCl. The precipitated salt is f i l tered off, washed with three portions of ether and dried in air. Yield: 21 g (91%) of salt having the composition [ (CeHjs)2C (OH)CjH4N2Cl]2HgCl2. A 20-g portion of this salt is treated with 100 ml of cooled ethyl acetate containing 5.5 g of HgCl and, with vigorous stirring and cooling, with 5 g of copper powder. A f ter 24 hours the solvent is evaporated off and the residue washed well with warm petroleum ether and extracted with hot ethyl acetate. The solution is concentrated and gives 10 g of white crystals (40% calculated on the amine). Recrys-tallization f rom benzene; m.p. 158°C (compound containing 1 mole of CgHj ) . The benzene can be removed at 140°C, after which the melting-point is 93°C.

Preparation of o-iodophenylmercury iodide [38] . o-lodoaniline (27.4 g, 0.125 mole) is dissolved on heating in 220 ml of 10% H2SO4 . The mixture is cooled to O0C and is then subjected to a slow addition, with energetic stirring, of 8.7 g (0.125 mole ) of NaNO2 . The resulting diazo solution is set aside on ice and a saturated solution of Hgl2 in NaI poured in. The precipitated double salt is washed with water, alcohol and several portions of ether. The yield of the crude product is 75 g (75%). Af ter reprecipitation with absolute ether f rom acetone and nitromethane, the salt melts at 69-69.5°C (with decomposition).

A 44-g portion of the double salt and 33 g of copper in 250 ml of acetone (not above -5 °C ) give, after extraction with 1 l i ter of acetone, 10.26 g (35%) of o-iodophenylmercury iodide. After two recrystall izations f rom a 1:1 mixture of nitromethane and benzene, the melting-point is 154°C.

D e c o m p o s i t i o n o f t h e D o u b l e D i a z o n i u m S a l t i n W a t e r [ 3 6 ]

The double salt is added in small portions to a well stirred and cooled (0°C, with ice-water) suspension of copper powder (50%


excess) in water (50-60 ml for every 10 g of the salt). The tem-perature is preferably maintained around 0°C throughout the decomposition, which takes 4-5 hours. The precipitate is then filtered off and washed with a small volume of alcohol and ether, and the organomercury salt is extracted with benzene, acetone, or ethyl acetate. Finally, the compound is recrystallized from one of the above solvents or from chloroform or alcohol.

This method has been used to obtain the organomercury deriv-atives of benzene and its homologs, naphthalene, halogenobenzenes and carboxylic acid esters, in good yields, practically equal to those obtained by decomposing the double salts in acetone. m-Nitrophenyl-mercury chloride was obtained in only 27% yield, owing to the im-possibility of cooling the solution to the required extent [36] (cf. [3]).

Synthesis of phenylmercury chloride. A 25-g portion of the double diazonium salt and 7.5 g of copper in 100 ml of water give (acetone extraction) 10 g (52.8%) of the desired product, m.p. 251°C.

Synthesis of p-tolylmercury chloride. A 12.5-g portion of the double salt and 3.5 g of copper in 60 ml of water give (acetone extraction) 6.47 g (68%) of the desired product, m.p. 237°C.

Synthesis of a-naphthylmercury chloride. A 14.1-g portion of the double salt and 4.95 g of copper in 100 ml of water give (acetone extraction) 7.4 g (66.8%) of the desired pro-duct, m.p. 190- 191°C.

Synthesis of OT-bromophenylmercury chloride. A 13-g portion of the double salt and 3.5 g of copper in 90 ml of water give (benzene extraction) 4.5 g (43.4%) of the desired product, m.p. 198°C.

Synthesis of p-carbethoxyphenylmercury chloride. A 22.2-g portion of the double salt and 5.8 g of copper in 110 ml of water give (ethyl acetate extraction) 10 g (56%) of the desired product, m.p. 220°C.

b)Preparation of Diarylmercuries

The double salt of aryldiazonium chloride and mercuric chloride (10 g) is mixed with 8 g of copper powder, and 50 ml of previously cooled acetone are poured onto the mixture. Five minutes after the end of reaction an equal volume of 25% aqueous ammonia is added and the whole mass is stirred vigorously for a few minutes and set aside for 24 hours at room temperature. It is then heated for 1-2 hours under reflux, a large excess of water added to pre-cipitate all the organomercury compound and the precipitate is filtered off and washed with water and then with a little ether. The diarylmercury is extracted with alcohol, benzene, or chloroform, and is as a rule recrystallized from one of these solvents. This method was used to obtain the fully substituted organomercuries of hydrocarbons (diphenyl- [2, 54], d i -o - [2], di-m- [55] and di -p-


[2, 56] tolyl-, dipseudocumyl- [55], d i -a - [2] and di-/3-naphthyl [32] mercury), halogenated hydrocarbons (di-p-fluorophenyl- [58], di-<?-, di-m- [59] and di-/>- [60] chlorophenyl-, bis-2,5-dichloro-phenyl-, di-?-bromophenyl- [2, 38, 61], d i -o - [38] and di-p-iodo-phenyl- [2] mercury), nitrated hydrocarbons (di-^-nitrophenyl-mercury [2], bis-(5-nitro-2-methylphenyl)mercury [39]), phenolic ethers (d i -o- [2, 41] di-m- [57] anddi -p- [41, 55] anisyl-, d i -o -[55] and di -p- [55] phenethyl-, bis-(phenoxyphenyl)- [41] mercury), halogenated phenolic ethers (bis-(3-iodo-4-methoxyphenyl)mercury [62]), benzoic esters (mercuri-bis-o- and m-methyl benzoates [30]), biphenyl [41], anthraquinone [46], and pyridine [64].

Preparation of diphenylmercury [2 ] . Thedoublesal to fbenzenediazoniumchlor ideand HgCl2 is obtained in a yield of 20.35 g, by mixing 4.65 g of aniline in 20.0 ml. of conc. HCl1

20.0 g of ice, 3.5 g of NaNO2 in 7.0 ml of water and 13.5 g of HgCl2 in 15.0 ml of conc. HCl with the addition of 15.0 g of ice.

A 10-g portion of this salt, 8 g of copper powder, 40 ml of acetone and then 40 ml of 25% ammonia give, after extraction with alcohol, 3.0 g (68%) of diphenylmercury, m.p. 125°C (from alcohol).

Preparation of di-o-tolylmercury [2 ] . The double salt of o-tolyldiazonium chloride and HgCl2 is obtained in a yield of 16.4 g by mixing 10.7 g of o-toluidine, 40 ml of HCl and 40 g of ice, 7.0 g of NaNO2 in 14 ml of water, 27 g of HgCl2 in 30 ml of conc. HCl and 30 g of ice.

A 10-g portion of this salt, 9 g of copper, 50 ml of acetone and 50 ml of ammonia give, after extraction with chloroform, 5.3 g of d i -o-to ly lmercury, m.p. 107°C.

Preparation of di-a-naphthylmercury [2 I . The double salt of a-naphthyldiazonium chloride and HgCl2 is obtained in a yield of 13.9 g by mixing 4.78 g of a-naphthyiamine, 15 g of conc. HCl, 15.0 g of ice, 2.3 gof NaNO2 in 7 ml of water, 9.09 g of HgCl2 in 10 ml of conc. HCl and 10 g of ice.

A 10-g portion of this salt, 8 g of copper, 50 ml of acetone and 50 ml of 25% ammonia give 2.6 g (53%) of di-a -naphthylmercury, m.p. 249°C. The S - isomer is prepared in the same manner [65].

Preparation of di-p-bromo phenylmercury [ 2 ] . The double salt of p -bromophenyl diazonium chloride and HgCl2 (with a nitrogen content dif fering slightly f rom the calcu-lated value) is obtained in a yield of 31 g by method (2), by mixing 30 g of p-bromoaniline in 75 ml of ether, 47.1 g of HgCl2 in 50 ml of conc. HCl and 100 g of ice, and 20 g of NaNO2 .

A 10-g portion of this salt, 8 g of copper, 50 ml of acetone and 50 ml of 25% ammonia give (chloroform extraction, crystallization from acetone) 3.0 g of di-p-bromophenyl-mercury, m.p. 243-244°C.

Preparation of di-p-iodophenylmercury [ 2 ] . The double salt of p-iodophenyldiazo-nium chloride and HgCl2 is obtained in a yield of 45 g by method (2), by mixing 22 g of P-iodoaniline in 100 ml of ether, 30 g of HgCl2 in 30 ml of conc. HCl and 30 g of ice and I O g o f N a N O 2 .

A 10-g portion of this salt, 8 g of copper, 50 ml of acetone, and 50 ml of 25% ammonia give, after extraction with chloroform, 3.9 g (70%) of di-p-iodophenylmercury; m.p. 270-272°C (from pyridine or xylene).

Preparation of bis-(TO-carbomethoxyphenyl) mercury [30]. Thedouble salt of m-carbo-methoxyphenyldiazonium chloride and HgCl2 is obtained in a yield of 46 g by mixing 21.7 g of methyl m-aminobenzoate in 100 ml of ether, 39 g of HgCl2 in 40 ml of HCl and 40 g of ice and a saturated aqueous solution of 15 g of NaNO2 .


A 10-g portion of this salt, 2.5 g of copper, 25 ml of acetone (at -10"C), another 5.5-g portion of copper and 30 ml of 25% aqueous ammonia give 1.4 g of b is - (m-carbomethoxy-phenyl) mercury; m.p. 129°C ( from ethyl acetate).

a-Aminoanthraquinone diazotized in sulfuric acid monohydrate heated for 1% hours at 180°C with a suspension of mercuric sul-fate in the same acid gave directly a 100% yield of a, a-dianthra-quinonylmercury [46]. An analogous method was used to make the /3, f3-isomer [46], in a yield of 94.7%. Thesea r e the only known cases in which fully substituted mercury compounds are obtained directly from diazo compounds, without reducing and symmetrizing agents.

Preparation of a,a-dianthraquinonylmercury [46]. a Aminoanthraquinone (1.0 g) is dissolved in 30 ml of sulfuric acid monohydrate over 3 hours at 60°C and 7.5 g of dry NaNO2 are added. The resulting diazo solutionis added in a thin stream, over 15 minutes, to a fine suspension of 0.73 g of HgSO4 in 100 ml of the above acid. The mixture is heated to 180°C and maintained at this temperature for I1A hours. It is then cooled, 300 ml of water added and the gray precipitate f i l tered off. This is washed f r e e f rom H g 2 + with 3% H2SO4 and f inally rinsed with water and boiling alcohol to remove a possible admixture of a-hydroxyanthraquinone. The precipitate is dried in a steam oven at I lO 0C. Yield; 1.35 g (98.5%); m.p. 275-276°C ( from acetic acid).

Arylmercury chlorides can be obtained by the action of metallic mercury on the corresponding aryldiazonium salts in water or other solvents [12, 14, 18, 19, 66], but only with special high-speed st irrers. The yields are 20-72% [66]. The method proposed by McClure and Lowy in 1931 has no advantages over the method de-scribed by Nesmeyanov in 1929.

Preparation of phenylmercury chloride from benzenediazonium chloride and metallic mercury [66] . Disti l led aniline (5 g ) is dissolved in 30 ml of conc. HCl and 50 ml of water and the solution cooled to O0C and diazotized in the usual manner. The diazo solu-tion is made up to 200 ml with distilled water and poured onto a 1.5 cm deep layer of mercury in a 600 ml beaker, which is then placed in an ice bath and maintained below 5°C throughout the experiment. The contents are st irred f o r 4 hours, at 1000 rpm, with an anchor-type s t i r rer made f rom a glass tube 4 mm in diameter, provided with an aperture at the bottom and containing many capillary openings on the underside of the rounded blades of the anchor. The precipitate is f i l tered off and boiled fo r a few minutes with 100 ml of water. Th iscauses themercury to collect into drops and allows its separa-tion f rom the precipitate by decantation. The product is finally f i l tered off and recrysta l -l ized from acetone. Yield: 45%; m.p. 251°C.

The reaction of potassium arylazocarboxylate with mercuric chloride leads [67] to the formation of arylmercury chlorides in up to 54% yields (the aryl group was phenyl, p-tolyl, p-bromo-phenyl, p-nitrophenyl, p-sulfoxyphenyl and a-naphthyl). Judging by the character of the side products, the reaction proceeds by a homolytic mechanism.

Synthesis of phenylmercury chloride [67] . Potassium phenylazocarboxylate (2 g) is added over 30 minutes, at room temperature, to a solution of 8.7 g of HgCl2 (threefold excess) in 100 ml of acetone, with mechanical st irring. The stirring is continued fo r 30 minutes after the end of the addition, the solvent evaporated off, the dry residue washed



f r ee f rom HgCl2 with a solution of NaCl and then washed with water. Acetone extraction gives 1.78 g of the desired product (54%), m.p. 251-252°C. The weight of calomel is 1.03 g. The corresponding reaction with HgBr2 gives a 40% yield of phenylmercury bromide, m.p. 275°C.

Diphenylmercury was obtained, in a yield of 94%, by the action of potassium phenylazocarboxylate on phenylmercury chloride [67]. For the reactions of potassium arylazocarboxylates with / 3 - c h l o r o -vinylmercury chlorides, leading to arylmercury chlorides, see Chapter 6.

Phenylazotriphenylmethane [20, 21] andbenzylaminodiazobenzene [68] stirred for a long period in CCl4 with metallic mercury give small yields of phenylmercury chloride (15% in the second case).

The phenylmercury acetate forming in the decomposition of nitrosoacetanilide in radioactively labeled benzene (in the presence of metallic mercury) is inactive [22].

c) Synthesis of Organomercury Derivatives with the Aid of Aliphatic Diazo Compounds

Diazomethane reacts with HgCl2, HgI2 [69] and HgBr2 [70] (Heller-man) in the absence of a reducing agent, giving the corresponding halogenomethylmercury halide:

CH 2 N 2 + H g X 2 -> X C H 2 H g X + N 2

The reaction is carried out in ether. An analogous reaction occurs between diphenyldiazomethane and mercuric chloride:

(C0H5 )2CN2 + HgCI2 - » N 2 + (C6H5 )2C (Cl) HgCl

If the diazomethane is taken in excess, it reacts with mercuric salts according to

X H g X + 2CH 2N 2 2 N 2 + X C H 2 H g C H 2 X

giving bis(halogenomethyl)mercury [69]. According to Hellerman and Newman, bis-(iodomethyl)mercury

can be obtained in 75% yield if dioxan is used as the solvent in place of ether [71].

In contrast, the action of diazomethane in ethereal solution on mercuric acetate does not result in liberation of nitrogen but pre-dominantly in the formation of an explosive polymeric compound (-HgCNN-) and a small amount of bis-(diazomethyl)mercury Hg(CHN2)2 [71a].

Two fully substituted organomercury compounds are formed in the interaction between diazomethane and salts RHgCl (R = C6H5, CH3C6H4; C6H5CH2) [69]:

2RHgCl + 2CH2N2 2N2 + (2RHgCH 2 Cl ) R 2 H g + (C lCH 2 ) 2Hg


The intermediate RHgCH2Cl is stable when R = C6H5CH2.Theaetion of diazomethane upon arylmercury salts of carboxylic acids also gives fairly stable compounds of the type RCO2CH2HgAr [72, 73]. Trichloromethylmercury bromide and diazomethane give trichloro-methylmonobromomethylmercury [74] (see also Chapter 12).

Preparation of chloromethylmercury chloride [69 ] . Diazomethane (2.1 g ) obtained by the slow addition of 12 g of nitrosomethylurethane to a mixture of 60 ml of ether and 18 ml of methanolic 25% KOH, at such a rate as to keep the reaction mixture co lor l ess , is passed into a solution of an equimolar amount of H g C l 2 (13.6 g ) in 200 ml of ether, with continuous st i r r ing . Rapid reaction takes place, with evolution of gas and with appearance of crystals towards the end. Evaporation of the ether g ives the desired product, which is subsequently recrys ta l l i z ed f r om alcohol. The y ie ld is quantitative; m.p. 131°C.

bis-(Chloromethyl)mercury is also obtained by the addition of 2 moles of diazomethane to 1 mole of HgCl, in ether. At the end of the addition, the solution should be yellow" owing to the excess of diazomethane. Traces of calomel are filtered off, and the solution is rapidly evaporated in a current of dry air. The remaining slightly colored oil crystallizes within a few days, and is recrystallized from ether; m.p. 37-40°C.

Both these substances are highly toxic and burn the skin. Diazotization of methylamine hydrochloride with amyl nitrite in

the presence of HgCl2 and copper powder results in a very small yield of chloromethylmercury chloride [75].

The interaction of mercuric chloride and diazoacetic ester according to the formula [75]:

4CHN2COOCo H5 + 3HgCl2 2CH2C1C00QH5

+ Hg (ClHgCClCO(X2H5)2 + 4N2

gives a product in which the diazo group is replaced by HgCl and Cl, and is accompanied by mercuration of the a-hydrogen.

Guided by the formal analogy between the electronic structures of (C6H5)3P=CH2 and diazomethane, Seyferth and Grim [76, 77] reacted the former compound with mercuric bromide in ether at room temperature. The product was precipitated in the form of bis-(tribromomercuri)mercurate [(C6H5)3P+CH2]2Hg(HgBr3)£", bis-tetraphenylborate, or reineckate.

d) Synthesis of Organomercury Compounds by the Action of Arylhydrazines on Mercuric Salts

Arylhydrazines are oxidized by mercuric salts, and arylate the latter to arylmercuries (Fischer). Thus, phenylhydrazine reacts with mercuric oxide to give an appreciable yield of diphenylmer-cury [78, 79].



Preparation of diphenylmercury from phenylhydrazine. An excess of yellow HgO is added to an ethereal solution of 10 g of phenylhydrazine. Immediate liberation of nitrogen takes place. Evaporation of the ether gives 4 g of diphenylmercury; m.p. 125°C.

The possibility of using other solvents in this reaction has also been studied [80], Thus, the action of phenylhydrazine on an aqueous solution of mercuracetamide gives diphenylmercury and several other products [81].

Arylmercury acetates [83] are formed in good yields by the action of arylhydrazines on mercuric acetate in the presence of copper acetate. The reaction passes, of course, through an inter-mediate formation of a diazo compound [82], This method has been used to prepare phenylmercury, p-nitrophenylmercury and p-bromophenylmercury acetates. Phenylmercury acetate has been converted into diphenylmercury by means of phenylhydrazine.

Preparation of phenylmercury acetate [83] . A concentrated solution of 1 g of copper acetate is added to a solution of 31.8 g of mercuric acetate in 200 ml of water acidified by 3 ml of concentrated acetic acid. The whole mixture is heated to 90°C and gradually treated with 5.5 g of phenylhydrazine, with vigorous stirring. Immediate reaction takes place, accompanied by evolution of nitrogen and liberation of metallic mercury. The solution assumes a purplish-red color which disappears only when all the phenylhydra-zine has been added. The mixture is then heated to complete the reaction and the preci-pitate, which forms on cooling, is f i l tered off and recrystal l ized from 5% acetic acid in the presence of animal charcoal. Yield: 11.8 g (70%); m.p. 146-147°C.

e) Synthesis of Organomercury Compounds with the Aid of Hydrazones

As has been shown by Nesmeyanov, Reutov and Loseva [84-86], hydrazones of aldehydes and ketones react easily with mercuric acetate at moderate temperatures (in the cold or at 70-90°C), in water, methanol, or benzene, with liberation of nitrogen and with the formation of mercurous salts and organomercury derivatives in which the mercury is attached to the secondary or tertiary carbon. The reaction evidently proceeds through an intermediate stage involving the formation of diazo compounds which, after liberation of nitrogen, add to their freed valences the acetoxy-mercuri group and the corresponding electronegative residue which depends on the nature of the solvent: an acetoxy group in the case of benzene, an alkoxy group in the case of alcohol, or a hydroxyl group in the case ofwater. However, in the last-mentioned case the products are not a-hydroxyalkylmercury derivatives but ether derivatives:

+ H g 2 (OCOCH3)2 + N2

0 + H g 2 (OCOCH3)2+N2

2

A l k O H

RR'C=NNH2+Hg(OCOCH3 )2

RR'C T / HgOCOCH3

H i O R R ' C /

x O A l k

HgOCOCH3I


In benzene N2 + Hg2 (OCOCH3)2 + R R ' C /

HgOCOCH3

RR 'C=NNH 2 + Hg (OCOCH3)2 \ OCOCH;

In most cases dimercurated compounds are formed independently of whether equimolar or smaller quantities of mercury are used in the reaction, owing to mercuration at the adjacent carbon:

R = H, Alk, or CH3CO. The above reaction is applicable to the hydrazones of aliphatic,

alicyclic and aromatic aldehydes andketones (acetaldehyde, acetone, methyl ethyl ketone, butyrone, eyelopentanone, cyclohexanone, 4-methylcyclohexanone, camphor, o-nitrobenzaldehyde and benzo-phenone). The yields are generally high and in some cases reach 96-98%.

The reactions of the hydrazones of cyclohexanone and 4-methyl-cyclohexanone with aqueous mercuric acetate give monomercurated cyclohex-l-ene and 4-methylcyclohex-l-ene.

Synthesis of a ,a ' , /3, /3-tetrachloromercuridi-isopropyl ether [85 ] .

Fresh ly dist i l led acetone hydrazone (5 g, 0.07 mo le ) is added, drop by drop and with vigorous mechanical st irr ing, to a solution of 44 g (0.14 mole ) of mercur i c acetate in 250 ml of water heated to 70°C. Immediate reaction takes place, accompanied by evolu-tion of heat, l iberation of nitrogen and formation of mercurous acetate. At the end of the hydrazone addition all mercurous acetate is reduced to metal l ic mercury , which is f i l t e red off a f ter 5 minutes of st i rr ing. Treatment of the f i l t ra te with 10% KCl results in the appearance of a white voluminous precipitate of the des ired product. Weight 17 g. A f ter two reprecipitations with water f rom acetone, the substance decomposes above 150°C without melt ing.

Synthesis of l- (aeetoxymercuri) cyc lohex- l -ene and l-(chloromercuri) cyc lohex- l -ene [86 ] . Cyclohexanone hydrazone (5 g, 0.045 mo le ) is added drop by drop, with intensive st irr ing, to a solution of 28.5 g (0.09 mo le ) of mercur ic acetate and 1 g (0.005 mo le ) of copper acetate in 250 ml of water heated to 90°C. The reaction Is accompanied by evolu-tion of heat, separation of mercurous acetate and l iberation of nitrogen. The reaction mixture is f i l tered. On cooling, the f i l t ra te yields white crysta ls of l - ( a ce toxymercur i ) cyc lohex- l - ene , in a y ie ld of I g (46% on the hydrazone); m.p. 116-116.5°C ( f rom methanol).

Treatment of the aqueous f i l t rate remaining after the separation of the l - ( a c e t oxymer -curi )cyclohex 1 ene with 10% KCl solution results in the precipitation of white f lakes of l - ( ch loromercur i ) cyc lohex 1 ene; weight 5 g; m.p. 191-192°C ( f rom toluene).

R "OH R C - N N H 2 + Hg (OCOCH3)2

\ R ' -CH 2

RC-HgOCOCH3

I OR" R ' -CH-HgOCOCHs



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CHAPTER 8

Synthesis of Organomercury Derivatives via Halogenonium Compounds

Aromatic organomercuries may be obtained by the action of metallic mercury on chloronium, bromonium, or iodonium com-pounds (the latter at higher temperatures), or by the decomposition of the double salts of diarylhalogenonium halides with mercuric halides in the presence of a reducing agent.

Sandin, McClure and Irwin [1] were the f irst to obtain arylmercury chlorides by boiling diaryliodonium chlorides with metallic mercury in water or n-propanol:

Ar2ICl + Hg ArHgCl + ArI

The same method has been used to make phenylmercury and p-tolylmercury chlorides.

S y n t h e s i s of phenylmercury chloride [ l ] . Asolutionof 3 g of diphenyliodonium chloride in 150 ml of n-propanol is boiled for 5 hours with 2 g of mercury and the solution f i ltered. Cooling of the f i l trate gives 1,25 g (40%) of the desired product; m.p. 251°C [2],

Makarova and Nesmeyanov [2, 3] obtained a 50% yield under these conditions. Benzene, and particularly acetone, proved to be even better media for the above reaction [4]. In the latter solvent, the corresponding diaryliodonium chlorides gave, after boiling for 3 hours, compounds ArHgCl where Ar was (yields in parentheses) C6H5 (76%), P-CH3C6H4 (55%), P-CH3OC6H4 (53%), P-ClC6H4 (77%), P-BrC6H4 (75%), M-O2NC6H4 (40%) and P-C2H5OCOC6H4 (47%). In the decomposition of mixed diaryliodonium chlorides the mercury takes up the more electropositive radical; thus, the decomposition of C6H5(^-CH3OC6H4)ICl gives C6H5HgCl (70% yield) and the de-composition of P-CH3OC6H4Kp-C2H502CC6H2)ICl leads to P-C2H5

OCOC6H4HgCl (56%). If the two radicals di f fer only slightly in their electronegativity, both arylmercury halides will be formed:

C6H6 (P-IC6H4) ICl + Hg -> C6H6HgCl + P-IC6H4HgCl

246

SYNTHESIS VIA HALOGENONIUM COMPOUNDS 247

Decomposition of diphenyliodonium iodide by 24 hours of shaking with metallic mercury at 80°C in labeled benzene (14C6H6) gave a 15% yield of inactive phenylmercury iodide [5].

On being shaken with mercury in isopropanol at room tempera-ture, bromonium and chloronium salts - diphenylbromonium and diphenylchloronium halides (iodides, bromides and chlorides) -arylate the mercury to give up to 45% yields of the corresponding phenylmercury halide. The dipheny lbromonium iodide reacts even in water, on boiling. Phenylmercury bromide has been obtained in this way from diphenylchloronium bromide in a yield of 66% [6, 7].

In contrast to aryldiazonium fluoroborates, the diarylhalo-genonium fluoroborates do not give organomercuries with metallic mercury [2, 3, 6], though they can arylate the less noble (more nucleophilic) metals (thallium, tin, lead and bismuth) capable of converting the halogenonium cations into a form giving covalent bonds with the metals.

Like the double salts of aryldiazonium halides with mercuric halides, the double salts of diarylhalogenonium halides with mer-curic halides give r ise to organomercury compounds when they are decomposed in the presence of a reducing metal in a suitable solvent. Decompositions of the double salt of diphenyliodonium chloride and mercuric chloride by the action of mercury, zinc powder, or copper powder in acetone or alcohol ( for zinc and copper), and also in water (for mercury) gave up to 34% yields of phenylmercury chloride; decompositions in the presence of mercury in water gave 70, 45 and 28% yields of ArHgCl for A r = C6H5, P-ClC6H4 and P-CH3OC6H4, respectively.

In the decomposition of (C6H5)2CLHgCl2 by iron powder in acetone or alcohol, the main reaction product (39 and 21% yields) is diphenyl-mercury [4]:

2 (C6H3)2Cl-HgCI2 + 2Fe ->• (C6H5)2Hg + 2C6H5 + 2FeCl2 -J- Hg

Double salts of diphenylchloronium iodide and of diphenylbromo-nium iodide with HgI2 gave phenylmercury iodide in yields of 22 and 38.5%, respectively, on being decomposed with copper powder in acetone in the cold [8].

Decomposition of the double salt of diphenylchloronium iodide and mercuric iodide. Preparation of phenylmercury iodide [ 8 ] . A solution of 3.8 go f the double salt and 1 g of copper in 100 ml of dry acetone is shaken f o r 7 hours at room temperature. The product is 0.39 g (yield: 22%) of phenylmercury iodide; m.p. 270°C.

Decomposition of the double salt of diphenylbromonium iodide and mercuric iodide. Preparation of phenylmercury iodide [ 8 ] . A solution of 3.3 g of the double salt and 1 g of copper in 90 ml of dry acetone is shaken f o r 4 hours at room temperature. The product is 0.63 g (yield: 38.5%) of phenylmercury iodide; m.p. 270°C.

Decomposition of diphenylbromonium chloride with metallic mercury. Preparation of phenylmercury chloride [7, 8]. A solution of 0.4 g of diphenylbromonium chloride, 2 ml



of mercury and 4 ml of isopropanol is shaken for an hour at room temperature. The product is 0.22 g (47%) of phenylmercury chloride; m.p. 260°C.

Decomposition of diphenylchloronium bromide with metallic mercury. Preparation of phenylmercury bromide. A solution of 0.2 g of diphenylchloronium fluoroborate in the minimum volume of water saturated WithNaBr, 1.5 ml of mercury and 3 ml of isopropanol is shaken for 30 minutes at room temperature. The yield is 0.17 g (66%) of phenylmercury bromide; m.p. 280°C.

Bibliography

1. R. B. Sandin, F. T. McClure and F. J. Irwin, J. Am. chem. Soc., 61, 2944 (1939).

2. L. G. Makarova and A. N. Nesmeyanov, Izv. Akad. Nauk SSSR, Otdel. khim. Nauk, 617 (1945).

3. A. N. Nesmeyanov and L. G. Makarova, Uchen. Zap. mosk. gos. Univ., 132, 109 (1950).

4. O. A. Reutov, O. A. Ptitsyna and K. V. Khu, Dokl. Akad. Nauk SSSR, 122, 825 (1958).

5. G. A. Razuvaev, G. G. Petukhov and B. G. Zateev, ibid., 127, 803 (1959).

6. A. N. Nesmeyanov, T. P. Tolstaya and L. S. Isaeva, ibid., 117, 996 (1957).

7. A. N. Nesmeyanov, T. P. Tolstaya and L. S. Isaeva, ibid., 125, 330 (1959).

8. A. N. Nesmeyanov, O. A. Reutov, T . P. Tolstaya, O. A. Ptitsyna, L. S. Isaeva, M. F. Turchinskii and G. P. Bochkareva, ibid., 125, 1265 (1959).

CHAPTER 9

Synthesis of Organomercury Compounds by the Substitution of Mercury for Acid Groups,

Heavy Metals and Some Metalloids in Organic Compounds

Its high electrophilicity permits mercury to be substituted into organic compounds not only for hydrogen (mercuration proper), but also for metalloid atoms in certain groups (mercuration in the wider sense) [1].

In an important method for the preparation of aromatic mercury compounds, mercury is substituted for acid groups, such as those in aryl(alkyl)boronic acids, sulfinic acids, carboxylic acids and iodoxy derivatives. Although the main field of application lies in the aromatic series, the reactions involving the CO2H, B(OH)2 and the SO2H groups are also used in the aliphatic series. The substi-tution of mercury for heavy metals [Sn, Pb, Bi, Tl , Cd, Si, Sb(III), and As(III)] in aryl (and sometimes in alkyl and alkenyl) derivatives can also be used for the synthesis of the aromatic and aliphatic (saturated and unsaturated) compounds of mercury.

As we shall see, mercury can be substituted in certain cases for metalloids such as boron in its organic compounds other than aryl(alkyl)boronic acids, silicon, and phosphorus, as well as titani-um and chromium in their organic compounds.

a) Substitution of Mercury for the Boric Acid Group and for Boron in Other

Organoboron Compounds

The mixing of boiling aqueous solutions of aryl(alkyl)boronic and diarylboronous acids and mercuric chloride, mercuric bromide, or mercury acetate leads to the formation of organomercury salts [2], the reaction proceeding quantitatively and extremely fast with any arylboronic acid and particularly with diarylboronous acids.

Refcrcnces see page 2(i') 2 4 9


RB (OH)2 + HgX2 + H2O RHgX + B (OH)3 +HX RaBOH + 2HgXa + H2O -> 2RHgX + B (OH)3 + 2HX

This reaction has been used to prepare the following organo-mercury compounds from the corresponding arylboronic acids: the chlorides of phenylmercury [2, 3], o-tolylmercury [4, 5], m-tolylmercury [5, 6], p-tolylmercury [5, 7], o-chlorophenylmercury [5], p-bromophenylmercury [5, 7, 14], m-methoxyphenylmercury [5], p-methoxyphenylmercury [4, 5], o-carboxyphenylmercury [5], m -carboxyphenylmercury [5], p-carboxyphenylmercury [5, 9], m-hydroxyphenylmercury [7], a.-naphthylmercury [5], /3-naphthylmer-cury [3, 4], o-nitrophenylmercury [10], 4-methyl-3-nitrophenyl-mercury [7], 4-methyl-3-hydroxyphenylmercury [7], benzylmercury [6], the acetates of p-bromophenylmercury [5], o-, m- and v-methoxyphenylmercury [5], o-, m- and p-tolylmercury [5], a-naphthylmercury [5], /3-naphthylmercury [5], m-carboxyphenyl-mercury, and the bromides of phenylmercury [3,11] (see also [12]), 2-hydroxymethylphenylmercury [3], 2-formylphenylmercury [3], 2-methyl-3,5-dinitrophenylmercury [3], 2-nitro-4-aminophenylmer-cury [3], 3-nitro-5-aminophenylmercury [3], a-furylmercury [13] and a-thienylmercury [13].

Synthesis of m-hydroxy phenylmercury chloride [7] . A saturated solution of HgCl2

is added dropwise to a solution of 0.3 g of m-hydroxyphenylboronic acid in 100 ml of water at 50°C until no more precipitate has formed. Ten minutes later the precipitate is f i l tered off and washed with hot water to remove the excess mercuric chloride. The product obtained in a practically quantitative yield is recrystal l ized f rom 30% alcohol; m.p. 240-241.5°C.

A few arylboronic acids, such as 3-nitro-5-carbomethoxyphenyl-boronic acid, which react with HgX2 in an aqueous solution only with difficulty or not at all, give the corresponding arylmercury halides in high yields when the reaction is carried out in an acetic acid medium in the presence of catalytic amounts of HClO4 [3].

Synthesis of 3-nitro-5-carbomethoxyphenylmercury chloride [3]. 3-Nitro-5-carbo-methoxyphenylboronic acid (0.1 g) is dissolved in 3 ml of glacial acetic acid at 80-90°C and 0.16 g of mercury acetate and 0.05 ml of 60% perchloric acid added. The reaction mixture is kept at this temperature for 2 hours, after which it is poured into 15 ml of water containing 0.2 g of KCl. This results in an immediate separation of a white pre-cipitate. Yield: 92%. It is recrystal l ized from ethanol; m.p. 247-249°C. Analogous oper-ations lead to 2-nitro 4-carbomethoxyphenylmercury chloride [3] in a yield of 97%; m.p. 172-173°C.

n-Propylboronic acid reacts with HgCl2Under vigorous conditions and boiling in water at 140-150°C for 20 hours leads to n-propyl-mercury chloride in a yield of 55% [14]. This is accompanied by the side reaction:

C3H7HgCl + HgCl2 Hg2Cl2 + C3H7Cl

SYNTHESES BY SUBSTITUTION OF Hg FOR VARIOUS GROUPS 251

The boiling of exo- or enfifo-5-norbornen-2-boronic acid with an equimolar amount of HgCl2 in 83% aqueous acetone until nearly all the acetone has evaporated results in nortricyclylmercury chloride in a yield of 80-83% [14a].

The ezo-isomer reacts 100 times faster than the endo-isomer. It is possible that this reaction proceeds via a rr-complex followed by transannular elimination of boric acid:

w-Styrylmercury chloride is obtained in a quantitative yield when styrylboronic acid and HgCl2 are heated in acetone for a short time [15]; trans -/3-chlorovinylmercury chloride has been prepared similarly [8].

Other alkylboronic acids do not react with HgX2 when boiled in an aqueous solution for 30 minutes, but the reaction proceeds readily when the reactants are heated in glacial acetic acid [3].

Synthesis of n-octylmercury chloride [3]. n-Octylboronic acid (0.10 g ) is dissolved in 2 ml of cold glacial acetic acid, 0.26 g of mercury acetate added and the solution heated to 90-100°C f o r 4-5 minutes. A solution of 0.1 g of NaCl in 15 ml of water is then added, which causes the immediate precipitation of n-octy lmercury chloride in a y ie ld of 0.18 g (81%); m.p. 115-116°C.

The same method has been used [3] for the preparation of iso-butylmercury chloride, in a yield of 50%; m.p. 54-55°C.

Synthesis of ferrocenylmercury chloride [ l 6 ] . An aqueous acetone solution of 0.19 g of HgCl2 is added to a hot solution of 0.16 g of ferrocenylboronic acid in 20 ml of water, resulting in the immediate separation of a yel low precipitate. The mixture is heated f o r a few minutes and the precipitate then f i l tered off, washed with water and dried in a vacuum desiccator over P 2 O 5 . Fe r roceny lmercurych lo r ide i sob ta ined in a y ie ld of 0.22 g (76%). Decomposit ion temperature 190-192°C; after recrysta l l i zat ion f r om xylene the melting-point is 192-194°C.

1- (T-Chloroferrocenyl )mercury chloride and 1-(1' -bromoferro-cenyl)mercury bromide can be obtained from the 1- (T -halogeno-ferrocenyl)boronic acids in an aqueous alcoholic solution with an aqueous acetone solution OfHgCl2 OrHgBr2 , inyields exceeding 80%.

H B(OH)2

References see page 2(i 9


The use of mercuric oxide (instead of the halides) with aryl(alkyl)-boronic acids in these reactions leadstothecorresponding diorgano-mercury derivatives in good yields [14].

Kinetic investigations [18] of this reaction, which is bimolecular and of first order with respect to each reactant, suggest that the product (Ar2Hg) is obtained via the intermediate formation of ArHgOH:

ArB (OH)2 + HgO + H2O ArHgOH + B (OH)3

ArHgOH + ArB (OH)2 Ar2Hg + B (OH)3

S y n t h e s i s o f d i -p - t o l y l m e r c u r y [ l 4 ] . p -To ly lboron ic acid (2.72 g, 2 mo l es ) is reacted with 2.16 g (1 mo l e ) of HgO in 50 ml of water at 100°C, giving 2.7 g of d i -p - t o l y lmercury ; m.p. 236°C (a f ter recrysta l l i zat ion f r o m benzene).

Phenylboronic acid reacts with mercuric nitrate in the presence of sodium acetate to give diphenylmercury in quantitative yield [19], whereas in the presence of KI, ammonium nitrate and ammonia, phenylmercury iodide is obtained, also in a quantitative yield [19].

Di- p-bromophenylmercury is prepared in a quantitative yield by boiling for 15 minutes p-bromophenylboronic acid and mercuric nitrate in water containing 1% of NaOH [19a], Di-p-bromophenyl-mercury Containing 202Hg has been prepared in the same way [19a].

The preparation of arylmercury compounds from boronic acids is today used mainly for identifying the latter; the fact that the arylboronic acids must first be prepared (generally by a Grignard reaction) prevents wide preparative application of this method. However, the method may gain new perspectives in the aliphatic series, since the addition of borohydrides and halides to olefins and acetylenes has resulted in the availability of a great number of saturated and unsaturated organoboron derivatives.

The use of arylboronic acids (and other arylating agents) for the synthesis of asymmetric diorganomercuries is discussed in Chapter 12.

In certain cases, mercury can also be substituted for boron in other organoboron compounds. Thus, all three groups are severed from the boron trialkylborons [22, 23] and triarylborons [20, 21] are treated with HgCl2 under mild conditions. Thus, diethylmercury is obtained from triethylboron in water and HgCl, [22], HgO in an alkaline solution [24], or mercury acetate (in diglyme [23, 24], or in water at room temperature [25]). The reaction of triallylboron with mercuric chloride has also been described [26], The reaction of triphenylboron or tris - p-dimethylaminophenylboron with HgCl2

in an aqueous alcoholic solution leads to the corresponding aryl-mercury chloride in a quantitative yield.

Further trialkylborons reacted with HgO in water to prepare dialkylmercuries include trioctyl-, trivinyl-, tr ihex-l-enyl- , t r i -octadec-l-enyl- and trioctadecylboron [22],

When reacted in an aqueous alcoholic solution with HgCl2 in the


cold, tetra-aryldiboroxides (Ar = phenyl [27] or p-tolyl [28]) lose quantitatively all four aryl groups to mercury:

Ar2BOBAr2 + 4HgCl2 + 5H20-> 4ArHgCl + 4HC1 + H3BO3

The same reaction occurs with metal tetra-arylborates in water [20, 21, 29], methanol [20, 21, 29], or acetone [30] in the cold:

Me BAr4 + 4HgCl2 + 3H20 4ArHgCl + MeCl + 3HC1 + B(OH)3

where Me = Li , Na, K, or NH4. Sodium triarylcyanoborate behaves in the same way, with cleavage of the three aryl groups. Sodium tetraphenylborate reacts with mercuric hydroxide in acetone to give diphenylmercury and phenylmercury hydroxide [29, 31], and with mercuric acetate in an aqueous alkaline solution to give diphenylmercury [32],

Synthesis of diethylmercury from triethylboron and HgO [24] . Mercur i c oxide (0.05 mole ) is suspended in water heated to 75°C and containing 0.15 mo le of NaOH and the suspension s t i r red with 0.05 mole of triethylboron. Completion of the react ion is manifested in 10 minutes by dissolution of the HgO and the format ion of a heavy oily substance which sinks to the bottom when the st i rr ing is discontinued. On disti l lation, this substance g ives diethylmercury in a y ie ld of 95%; b.p. 67-68°C/19 mm Hg.

Diethylmercury was obtained in a yield of 66% when triethylboron was boiled for 2 hours with mercuric acetate in 1,2-dimethoxyethane [24].

Synthesis of phenylmercury chloride from HgCl2 and tetraphenylborate [30] . Potas-sium tetraphenylborate (0.1224 g ) is dissolved in acetone and a smal l amount of water, fo l lowed by an acetone solution of 0.5 g of HgCl 2 , added. Phenylmercury chlor ide sepa-rates out instantaneously. F o r complete decomposition of the organoboron, the mixture is heated on a water bath and the acetone disti l led off . Phenylmercury chlor ide is f i l -tered off and washed with water; m.p. 252°C; yield: 0.41 g (95%).

Diethylmercury was obtained in a yield of 80% from the reaction of sodium tetraethylborate with HgCl2 or mercuric acetate in an aqueous alkaline solution on heating [32],

Tetramethylammonium bis-2,2'-bipheny leneborate is decomposed on being boiled for 1 hour in an acetone solution with 2N sulfuric acid to give o -biphenylylboronous acid. Subsequent reaction with HgCl2 in methanol leads to o-biphenylmercury chloride [21].

X + HgCI2

• N (CH3)4 * O-C6H5C6H4HgCl

Refercnc-es see page 2h9


When carried out in the presence of NaI,the same reaction leads

Treatment of tetramethylammonium bis-2,2'-biphenyleneborate with alkali in acetone and subsequent boiling with HgCl2 resulted in o, o -bis-chloromercuribiphenyl in a yield of 51% [21].

Boiling for 3 hours in ethanol in the presence of NaI leads to o, o-biphenylenemercury in a yield of 90% [21]. This compound exists as the tetramer [33] (see Chapter 2).

By contrast, only one aryl group is lost to the mercury when lithium potassium, or ammonium tetra-arylborates are shaken with metallic mercury for 70-80 hours in chloroform, preferably at -10 to -15°C, the reaction leading to diary lmercury. Tr iary l -borons do not react with metallic mercury [34], The corresponding Ar2Hg are formed from MefB(C6H5)3Ar] where Me is lithium [35], potassium [36], or ammonium [36], and from Li(BC6H5Ar3) [35], where Ar is tolyl or a-naphthyl. Phenylmercurychlorideis formed when the double salt Li[B(C6H5)4].2LiBr is shaken for 70-80 hours with metallic mercury in chloroform [36],

b) Substitution of Mercury for the SO 2 H Group

The Peters reaction between HgCl2 and sulfinic acids [37]

was fairly widely used in its time for the synthesis of organo-mercury salts, since before the discovery of the diazo method it represented the simplest preparation of those ring-substituted organomercury isomers which cannot be obtained by direct mer-curation. This reaction, initially used in the aromatic series, is today used also for the synthesis of mercury-containing aliphatic and heterocyclic compounds and metallocenes. In some cases the reaction takes place in the cold, but it generally proceeds less readily than the interaction between arylboronic and diarylboronous acids and mercuric salts (only on being boiled generally for not less than 1 hour).

The simpler alkyl derivatives of mercury have been prepared by the Peters reaction.

Synthesis of methylmercury chloride [38]. Sodium methylsulfinate (50 g ) in 200 ml of ethanol is mixed with 135 g of HgCl2 in 600 ml of ethanol giving immediately a white pre-cipitate. The inorganic mercury salt is removed by steam-distillation; m.p. 170°C. An additional portion of methylmercury salt is precipitated from the f i ltrate with KI, giving methylmercury iodide; m.p. 152°C.

to (O-C6H5C6H4)2Hg [21].

\ \ HgCl HgCI

RSO2H + HgCl2 RHgCl + SO2 + HCl


The halides of ethylmercury and butylmereury have been pre-pared in the same manner [38]. I-Dodecylmereury chloride is obtained from sodium 1-dodecylsulfinate in a yield of 49.3% [39]. The mercury derivatives of camphor have also been prepared with the aid of this reaction [40],

Synthesis of camphor-10-mercury chloride [40] .

Camphor-10-sul f in ic acid (1 mo l e ) is boiled f o r 4-5 hours with an ethanolic solution of 2 moles of HgCl 2 . The product is poured into water and allowed to stand f o r 12 hours. The precipitate is then col lected, washed with ethanol, extracted with hot ch loro form and twice recrys ta l l i z ed f r om ethanol containing a smal l amount of ch loro form; m.p.

3-Chloro- and 3-bromocamphor-10-sulfinic acids give the cor-responding mercury derivatives in good yields by the Peters re-action only in pyridine, or, with much less satisfactory results, when alkali metal sulfinates are used instead of the free sulfinic acids [41].

Synthesis of 3-chlorocamphor-10-mercury chloride [ 4 l ] . 3-Chlorocamphor-10-sul-f inic acid (9 g ) is boiled f o r 3 hours with 18 g of HgCl 2 in 30 ml of pyridine. T h e solution is then cooled and, after removal of the metal l ic mercury , it is added to an excess of dil. HCl. The precipitate is col lected, washed (finally with alcohol), dr ied and extracted in a Soxhlet with chloro form. Cool ing of the solvent results in separation of the product in the f o rm of long needles; m.p. 218-219°C; yield: 40-50%.

3-Chloro- and 3-bromocamphor-77-sulfinic acids do not undergo the Peters reaction with mercury salts [41].

Synthesis of phenylmercury chloride from benzenesulf inic acid [37] . Benzenesulf inic acid (3 g, 1 mo le ) is dissolved in aqueous alcohol, and 6 g of HgCl 2 (more than 1 mo le ) are dissolved in water. The two solutions are boiled and combined. Sulfur dioxide is evolved, and a white precipitate fo rmed. The reaction mixture is boiled until the odor of SO2 has disappeared, f i l tered, f r eed f r om metal l ic mercury by dissolution in pyridine and precipitated with water. The mater ia l is washed with ethanol, dissolved in hot ether and cooled. Phenylmercury chlor ide separates out; m.p. 251°C; the y ie ld is not given.

The reaction carried out in water in the presence of sulfuric acid gives phenylmercury chloride in ayieldof 73.6% [42] (see also [43]).

A better yield can sometimes be obtained by preventing HCl from being formed in the reaction. This is achieved by the use not of the f ree sulfinic acid but of its sodium salt, or by carrying out the re-action in pyridine.

Synthesis of 771-nitrophenylmercury chloride [44] . Sodium m-nitrobenzenesulf inate (8 g ) is dissolved in 40 ml of water and a solution of 21 g of HgCl 2 in 100 ml of ethanol

C H 2 H g C l

166°C.



added. Glacial acetic acid is then added in an amount slightly greater than that needed for the separation of the sulfinic acid (2.3 ml). The mixture is then boiled for 20 hours. m-Nitrophenylmercury chloride is extracted from the resulting precipitate with acetone and recrystal l ized f rom ethanol; m.p. 236-237°C; yield: 42% (see also [165]).

o- and p-Nitrophenylmercury chlorides were prepared by the same method [44].

The method is the best for preparing the aromatic compounds of mercury when halogenobenzenesulfinic acids are used. Thus, halogenophenylmercury acetates are formed when the corresponding halogenobenzenesulfinic acids are boiled with three equivalents of mercury acetate in glacial acetic acid (the mercurous salt being f i ltered off ) and water or alkali is added to precipitate the product. This method has been used to prepare the acetates of o-, m- and V -chlorophenylmercury, o-, m- and ^-bromophenylmercury, p-iodophenylmercury [45] and the chlorides of 2,4-dichlorophenyl-mercury, 3,5-dichlorophenylmercury and 2,4,6-trichlorophenyl-mercury [46]. The chlorides were obtained by adding NaCl to aqueous or alcoholic solutions of the acetates.

Preparation of p-chlorophenylmercury acetate [45]. A solution of 50 g of mercury acetate (not less than 3 mole-equivalents) in 100 ml of glacial acetic acid is added to a solution of 11.3 g of freshly prepared p-chlorophenylsulfinic acid in 50 ml of glacial acetic acid. A white precipitate of mercury sulfinate is immediately formed. This is then boiled for 15 minutes. This results in complete conversion into p-chlorophenylmercury acetate. The accompanying mercurous salt is f i l tered off and the acetate precipitated with water or alkali. Yield: 14.0 g; m.p. 193°C. T h e p r o d u c t i s r e c r y s t a l l i z e d f r o m alcohol.

The mother liquor of the sulfinic acid preparation is treated with 100 ml of 10% aqueous mercuric acetate. The mercury sulfinate precipitated out (4.7 g) is f i l tered off and mixed with 40 mi of glacial acetic acid and 4 g of mercuric acetate, heated to boiling and the P-chlorophenylmercury acetate isolated as above. The additional 1.5 g of the product thus obtained raises the over-al l yield to 15.5 g (70%).

This method has also been used with success for the preparation of p-tolylmercury chloride [37, 47-49] (andother salts [50]), 5- and 4-chloromercuri-2-nitrotoluenes [51], 2-chloromercuri-4-nitro-toluene [52] (though it is obtained in a higher yield by the diazo method [52]), a series of isomeric chloronaphthylmercury chlorides [53], ethylphenylmercury chloride [54], <?-benzylphenylmercury chloride [55], 2,5-dichlorophenylmercury chloride [52], o-( 1-naphthyl)phenylmercury chloride [56], 6-hydroxy-5-chloromercuri-coumarin [57], 2-chloromercuri-3,4',5-trimethyldiphenylmethane from sodium 2-(4-methylbenzyl)-4,6-dimethylbenzenesulfinate [58] and 4-stilbenylmercury iodide [59].

The boiling of w-benzenedisulfinic acid WithHgCl2 for 20 minutes in an alkaline solution leads to m-dichloromercuribenzene in a yield of 82% [60].

Preparation of 1,3-dichloromercuribenzene [60], A suspension of 4.70 g (0.0238mole) of w-benzenedisulfinic acid in 10 ml of water is rendered alkaline with a 50% solution of NaOH and added to a solution of 16.35 g (0.06 mole) of HgCl2 in 50 ml of water. A curdy


precipitate separates out almost at once, and the reaction mixture sets to a pasty con-sistency on a water bath. The strongly acidic mixture is diluted with 50 ml of water over 20 minutes and heated on a water bath f o r 6 hours. The precipitate is f i l t e red off and washed with hot water to r emove the mercury salt (of which 0.015 mole was washed out), subsequent washing being carr ied out with boiling alcohol and boiling benzene. These operations led to 70.7 g (82%) of infusible 1,3-dichloromercuribenzene,

m-Diacetoxymercuribenzene can be obtained in a yield of about 70% by boiling for 2 hours potassium w-benzenedisulfinate with mercuric acetate in glacial acetic acid [61].

Boiling for 3 hours of an alkaline solution of 1,8-anthraquinone-disulfinic acid with an aqueous solution of HgCl2 leads to 1,8-di-chloromercurianthraquinone in a yield of 85% [62].

This method has been used to prepare 2-chloromercuri- and 2,8-dichloromercuribenzofuran [63].

Preparation of 2-chloromercuribenzofuran [63] . A hot solution of 12.7 g (0.05 mole ) of sodium benzofuran-2-sulf inate in 150 ml of water is added quickly and with st i rr ing to a boiling solution of 27.2 g (0.1 mo le )o f HgCl2 in 200 ml of water. The product is r ec rys ta l -l ized f rom acetone and obtained in a y ie ld of 82%; m.p. 236.5-237°C.

2-Pyridylmercury chloride and 6-chloropyridyl-3-mercury chlo-ride have been obtained by boiling for 15 minutes the corresponding sulfinic acid with HgCl2 in water and setting it aside for 2 hours.

The Peters reaction has also been used for the synthesis of the mercury derivatives of metallocenes. Thus, chloromercuriferro-cene and dichloromercuriferrocene are readily obtained from the corresponding ferrocenesulfinic acids [65].

Synthesis of chloromercuriferrocene [65] . An alcoholic solution of 0.27 g (0.001 mo le ) of HgCl2 is added to a solution of 0.31 g (0.001 mo l e ) of sodium ferrocenesul f inate . A precipitate of ch loromercur i f e r rocene separates out at once. This is isolated, dried and weighed. Yie ld: 0,41 g (quantitative); m.p. 194-196°C.

Synthesis of dichloromercuriferrocene [65] . An alcoholic solution of 0.32 g (0.0078 mo le ) of sodium ferrocenedisul f inate is heated with 0.55 g (0.002 mo l e ) of HgCl 2 . A yel low precipitate of d ich loromercur i ferrocene separates out. Y ie ld: 0.41 g (80%).

When the sodium salt of tricarbonylmanganesecyclopentadienyl-sulfinic acid is boiled for 45 minutes with HgCl2 in an aqueous-alcoholic solution, chloromercuricyclopentadienylmanganesetri-earbonyl is obtained in a yield of 80% [66],

Loudon [67] has shown that the Peters reaction cannot be used to establish the structure of addition compounds formed between mercury salts and unsaturated compounds.

c) Substitution of Mercury for the Iodoxy Group

In a method devised by Nesmeyanov and Makarova [68], organo-mercury hydroxides are prepared from iodoxy-substituted aromatic



compounds in the following manner:

Ar IO2 + HgO + AgOH ArHgOH + Ag IO3

This is analogous to the preparation of compounds of the type of Ar2IOH by Victor Meyer's method:

ArIO2 + ArIO - f AgOH -> Ar2IOH + AgIO3

This method has been used for the synthesis of organomercury compounds containing hydrocarbon groups and the halogen and nitro-derivatives of hydrocarbons. A suspension of mercuric oxide in water is boiled with an iodoxy-substituted aromatic com-pound in the presence of an alkali, preferably AgOH. The resulting organomercury hydroxide separates out as a salt when the reaction mixture is treated with an acid or an alkali metal salt and an acid.

Mercuric oxide is prepared by the addition of an excess of NaOH to a hot aqueous solution of HgCl2, followed by decantation until a neutral reaction is obtained, and finally filtration at the pump. It is used in the form of a wet paste.

Preparation of phenylmercury bromide [68]. Iodoxybenzene (1.18 g) is boiled for 4 hours with 2 g of a mercuric oxide paste and 2 g of AgOH paste in 100 ml of water. The precipitate is f i l tered off, another 100 ml of water added and the mixture again boiled for an hour. This is repeated until the addition of KBr to the f i ltrate no longer gives a precipitate (after the water has been replaced three times). The product obtained by precipitating the compounds of the f i ltrate with an aqueous solution of KBr and by acidifying with acetic acid is phenylmercury bromide (1.66 g); after recrystall ization from acetone 1.56 g (88%); m.p. 275°C. Without repeated boiling, the yield is 70-80%.

If instead of being treated with KBr the reaction mixture is concentrated to a small volume under vacuum, so that no atmos-pheric CO2 can enter the aqueous medium, phenylmercury hydroxide is obtained in the form of needle-shaped crystalline prisms.

p-Tolylmercury bromide and the chlorides of o-, m- and p-chlorophenylmercury and of o- and m-nitrophenylmercury [68] have been prepared by a method similar to that for phenylmercury bromide.

When the hydroxide shows a poor solubility, the organomercury compound is isolated in the following manner. After the boiling stage, the precipate is mixed with an alkali metal salt of the cor-responding acid, treated with a small amount of a weak acid, and the organomercury salt is extracted from this mixture with a suitable solvent.

Synthesis of p-nitrophenylmereury chloride [68]. p Iodoxynitrobenzene (1.4 g ) is boiled for 12 hours with 2 g of a mercury oxide paste and 2 g of AgOH paste in 100 ml of water. The precipitate was f i l tered off, triturated with an excess of NaCl under 5 ml of 2N acetic acid, f i ltered and extracted with acetone. Yield of p-nitrophenylmercury chloride: 0.95 g (54%); m.p. 265°C.


This method enables several salts from the same organomercury hydroxide to be prepared simultaneously by precipitating portions of the filtrate with various anions.

d) Substitution of Mercury for the Carboxyl Group

In several cases the carboxyl group can be replaced by mercury by heating the mercury salt of the carboxylic acid, or by heating the carboxylic acid with mercury salts. In the second case, the synthesis proceeds via the intermediate formation of the organo-mercury salts.

The elimination of the carboxyl group and the introduction of mercury in its place by heating the mercury salts of fatty acids proceeds with ease whenever the a-carbon atom carries a sub-stituent such as CH3CO or C6H5CO [69].

Depending on the conditions, the reaction with benzoylacetic acid takes place as follows:

C 1 H 5 O H , h e a t i n g ^ + ^ ^ H ^ H g

( C 6 H 5 C O C H 2 C O O ) 2 H g — C H C l 3 , h e a t i n g 1 • C 6 H 5 C O C H C O + C a H 5 C O C H 2 C O O H

I I H g - O

By heating the mercury salts of a,a-dialkylaeetoacetic acids in vacuum at 85-90°C, Kharasch and Staveley [69] obtained mercuri-bis-acetodialkylmethanes, the alkyl groups being CH3 or C2H5 .

Nesmeyanov, Lutsenko and Ananchenko [70] have appreciably improved this method of a-mercuration of oxo-compounds by decarboxylation of the mercury salts of / 3 - k e t o acids. The a -chloromercuriketone, the final product, is reached in the improved method not in three steps (as in Kharasch and Staveley's method) but in a single step and in a yield of 50-70%, whereas the yields obtained by Kharasch and Staveley were only 5-7%. The reaction is carried out by heating for 5 minutes an aqueous solution of the / 3 - k e t o acid with mercuric acetate.

Synthesis of methyl a-chloromereuri-isopropyl ketone [70] . Dimethylacetoacetic acid (48 g, 0.37 mo l e ) is added dropwise to a solution of 115 g of mercury acetate in 300 ml of water, result ing in the precipitation of mercur ic dimethylacetoacetate. Decarboxyla-tion is car r i ed out by heating this salt in an aqueous solution, the completion of the reaction being indicated by disappearance of mercur i c ions f r o m the solution; the solution becomes transparent. The solution is f i l t e red hot and to the sti l l -hot solution is added dropwise a solution of 26.7 g of KCl in 150 ml of water . A white precipitate separates out, which at f i r s t rapidly red isso lves , but separates out again in the f o r m of white crysta ls as mor e and more KCl is added. Th is mater ia l is f i l t e red at the pump and dried over C a C l 2 in a desiccator. Y i e ld : 89 g (77%); m.p. 124°C (after recrysta l l i za t ion f rom alcohol).

Synthesis of 3-methyI-3-ehloromercuripentan-2-one [70], Methylethylacetoacetic acid (43 g ) is added to a solution of 80 g of mercury acetate in 275 ml of water. The resulting



mercury salt is decarboxylated by heating the aqueous solution to 45-50°C on a water bath. After the reaction has reached completion, a solution of 18 g of KCl in 50 ml of water is added, which gives a bulky precipitate. In the usual organic solvents, this sub-stance separates out in the form of an oil. It is dried over P 2 O 5 in a desiccator. Yield: 72 g (72.9%).

The same technique was used to prepare [70] 3-ethyl-3-chloro-mercuripentan-2-one (yield 58%; m.p. 77°C after recrystallization from methanol), 2-methyl-2-chloromercuricyclopentanone (decom-position at 125°C without fusion) and 2-methyl-2-chloromercuri-cyclohexanone (m.p. 128°C).

The reaction of the components in a 1:1 mixture of sodium tr i-chloroacetate and HgCl2 (or HgBr2) leads to CCl3HgHal. When the ratio is 2:1 and the mercury compound is HgCl2 or mercuric acetate, the reaction gives (CCl3)2Hg [71]. According to Logan [71], this reaction proceeds by decarboxylation of the intermediate CCl3COOHgX, and not through the addition of dichlorocarbeneto the Hg-X bond.

S y n t h e s i s o f b i s - t r i c h l o r o m e t h y l m e r c u r y [ 7 l ] . A solution of 27.2 g (0.1 mole ) of HgCl2

and a solution of 37.0 g (0.2 mole) of sodium trichloroacetate are boiled for 1 hour in 150 ml of the monomethyl ether of ethylene glycol. The reaction mixture is then poured into water and the product extracted with ether. The ether extract is washed with water and dried over magnesium sulfate. The ether is distilled off and the residue crystall ized f rom chloroform. Yield: 31.2 g (71.5%); m.p. 140-141°C.

When mercuric acetate is used, the yield is only 54%. The use of HgBr2 leads only to CCl3HgBr. An attempted synthesis of (CCl3)2Hg from sodium trichloroacetate and HgBr2 has been unsuccessful [71].

According to a US patent [71a], the mercury salts of polyfluoro-alkylcarboxylic acids and perfluoroalkylcarboxylic acids decarb-oxylate on being heated to high temperatures and form poly (per)-fluoroalkylmercury poly(per)fluoroalkylcarboxylates. Thus, the heating of mercuric trifluoroacetate to 300° C gives trifluoro-methylmercury trifluoroacetate, which distils over at 250-260°C (m.p. 83-92°C). The compounds obtained in the same manner in-clude pentafluoroethylmercury pentafluoropropionate (b.p. 113°C/9 mm; m.p. 49-51°C), perfluoropentylmercury perfluorohexanoate (m.p. 69.5-70°C) and 2H-tetrafluoroethylmercury 3H-tetrafluoro-propionate (b.p. 165°C/l3 mm; m.p. 58-58.5°C).

When chloromercuricamphorcarboxylate (C10H15OCO2HgCl) is boiled in water or benzene, CO2 is slowly liberated and chloro-mercuricamphor (C10H15OHgCl) is formed [71b]. Several mercury derivatives of camphor have been obtained by eliminating CO2 from the mercury salts of camphorcarboxylic acids [71b].

Theelimination of one molecule of CO2 from mercurated malonic and methylmalonic acids has been discussed in Chapter 5.

Decarboxylation was first used by Pesci [72] for the synthesis of organomercury compounds. By melting together phthalic acid and mercuric acetate, the above author obtained the internal salt of


o -hydroxymercuribenzoic acid (see also [75]):

CO

+ Hg (CH3COO)2 O + CO2 + 2CH3COOH

It has been shown by Kharasch [73] that aromatic organomercury compounds form, at high temperatures, mercury salts of carboxylic acids whose carboxyl groups are readily eliminated on being heated.

It can therefore be seen that this method has a narrow field of applicability. However, it is still valuable, since this type of organomercury compound often cannot be prepared by direct mercuration, by the diazo method, or via Grignard reagents.

Synthesis of 2,2',4,4',6,6 '-hexanitrodiphenylmercury [73] . Mercury 2,4,6-trinitroben-zoate is placed in a test-tube and heated to 210°C on a sulfuric acid bath until the evolu-tion of CO2 ends. The weight loss corresponds exactly to two molecules of C O 2 f o r each molecule of the mercury salt. The contents of the test-tube are extracted with acetone, which is then evaporated, leaving behind the desired product. The latter is r ecrys ta l -l ized f rom acetone and alcohol; m.p. 272°C.

Synthesis of the internal sal t of 2-hydroxymercuri-isophthalic acid [74] . Aso lut ion of 43.3 g (0.2 mo l e ) of HgO in 40 ml of glacial acetic acid and 70 ml of water is added to a solution of 40 g (0.2 mo le ) of hemimel l i t ic anhydride in 110 ml of 6N NaOH and 170 ml of water and the mixture heated f o r 16 hours, after which no more C O 2 is l iberated. The precipitate f o rmed (soluble in NaOH) is f i l tered off, washed and dried to constant weight at 105°C. Y ie ld : 70 g (96%).

As a result of prolonged heating of 3-nitrophthalic acid [78], 4-nitrophthalic acid [76, 77], 3-chlorophthalic acid [78], 3-bromo-phthalic acid [78], 4-chlorophthalic acid [77, 79] and 4-bromo-phthalic acid [77, 79] with mercuric acetate, one molecule of CO2

is eliminated and the carboxyl group in the 2-position is replaced by mercury.

Heating to 185-190°C for 5-6 hours the mercury salt of the monomethyl esters of 3-nitrophthalic acid (a - and / 3 - e s t e r s ) leads to quantitative elimination of CO2, its replacement by mercury and the formation of the same product [2-(C02CH3)-6-(N02).C6H3]2Hg from the two esters [80].

Whereas the mercury salt of o-nitrobenzoic acid gives on heating at 180°C for 4 hours di-o-nitrophenylmercury in a yield of 16% by the elimination of CO2 and its replacement by Hg, in the case of the corresponding m,- and p-isomers heating to 190°C for 6 hours leads to mercuration in the ring (in the 2-position) without the elimination of CO2 [76]; see Chapter 5.

When the mercury salt of naphthalic acid is heated [81] or naphthalic acid is boiled for 98 hours in an aqueous alkaline solution with a solution of HgO in acetic acid [82], the internal



salt of 8-mercuri-l-naphthoic acid is formed (in the second case, quantitatively).

On being heated until no more CO2 is liberated, the mercury salt of anthraquinone- o-dicarboxylic acid exchanges one carboxyl group for mercury, e.g. [83]:

O C O O - H g O H g - O

c x ^ r ^ - o x r Ii Ii

O O

A similar exchange takes place when ^-hydroxy- a-naphthoic acid is kept for some time in a cold solution of mercuric acetate in glacial acetic acid [84], The following method, devised by Rodionow and Fedorowa [85], for the preparation of veratr ic acid f rom hemipinic, is based on the ability of Hg to replace the car-boxylic group in carboxylic acids:

COOH CH3O-L J-COOH

I OCH3

I ^ x I l - C O O H

CH3O-^JJ I

OCH3

S y n t h e s i s o f v e r a t r i c a c i d f r o m h e m i p i n i c [ 8 5 ] . A s o l u t i o n of 35 g of h e m i p i n i c a c i d in 50 ml of a 25% solution of NaOH in 150 ml of water is boiled with a solution of 62 g of mercuric acetate in 300 ml of water and 50 ml of acetic acid for about 60 hours, to a negative reaction with NaOH for the H g 2 + ion. The mercury derivative of veratr ic acid is washed with water, dissolved in NaOH and precipitated with HCl. On being boiled for 5 hours in 120 ml of conc. HCl, 30 g of the mercury salt give 13.2 g of the product.

When a solution of trimethylisogalloflavin is heated fo r 3 hours with HgCl2 in the presence of potassium bicarbonate on a steam bath, CO2 is replaced by HgCl in the molecule [86],

The carboxyl group in a-furancarboxylic acids is replaced with great ease [87]. The corresponding furylmercury chloride is readily obtained by boiling sodium a-furylcarboxylate with an aqueous solution of HgCl3:

C4H3OCO2Na + HgCl2 C4H3OHgCl + CO2 + NaCl

The same reaction has also been carr ied out with the 5-bromo-, 5-iodo- and the methyl derivatives of sodium a-furylcarboxylates

Hg(CH3CO2)2 C O \ _ HCl

heating ' C H 3 O - ^ H g / ^ "

I OCH3


[87] and with the 3-methyl-4-carbomethoxy- derivative [88]. The boiling of 5-benzamidomethylfuran-2-carboxylic acid in an

aqueous solution of HgCl2 leads to the substitution not only of the carboxylic group, but also of the benzamidomethyl group [89] (in addition to mercuration), so that the reaction product is tetra-chloromercurifuran [89],

The substitution of mercury for the CO2H group has failed in the case of the /3-furancarboxylic acids.

When the free acid is used instead of its sodium salt, decarb-oxylation takes place without the formation of a mercury compound, since the hydrochloric acid formed exerts a cleaving action.

When mixed mercuric furoate acetate (obtained by the action of an aqueous solution of mercury acetate on a-furancarboxylic acid) is heated, the product is, unexpectedly, furan mercurated in the / 3 - p o s i t i o n [87],

Synthesis of 5-bromo-2-furylmercury chloride [87] . An aqueous solution of 1 mole of sodium 5-bromo-2- furoate (obtained by mixing equivalent amounts of the acid and NaOH) is added to a solution of 270 g (1 mo le ) of HgCl 2 in 5 l i ters of water; the mixture is set aside f o r 1 hour and then f i l t e red and boiled until the evolution of CO 2 ceases. It is then cooled and the product f i l t e red off and recrys ta l l i zed f r o m alcohol; y ie ld: 76%; m.p. 177°C.

Synthesis of /3-furylmercury chloride [87] . Mixed mercury acetate furoate of the f o r -

is obtained by adding a solution of 336 g (3 moles ) of a- furancarboxy l ic acid in 3 l i ters of water to a solution of 477 g (1.5 mo le ) of mercur ic acetate in 7.5 l i ters of water. The resulting precipitate (490 g, 88.3%) is f i l t e red off.

A f lask is then fitted with a s t i r r e r , a thermometer and a condenser with a receptacle to col lect the furan, the condenser being attached via a bottle containing a 30% solution of NaOH. A f ter 840 g (2 mo les ) of acetoxymercuri furoate has been placed in the f lask, the f lask is heated on an oil bath whose temperature is ra ised to 2IO0C in the course of 10 hours. The temperature inside the f lask remains I lO 0 C, reaching 135°C only towards the end of the reaction. T h e evolution of the gases ceases, in 10 hours and a precipitate (547 g ) is obtained. This is then dissolved in 900 ml of 95% acetic acid and the resulting solution diluted with 8 l i ters of water and f i l tered. Sodium chloride is then added to the f i l t ra te until the formation of a precipitate has ceased. The precipitate is f i l tered off, washed, dried and weighed (270 g). It is then extracted with ether in a Soxhlet apparatus. Eva oration of the ether and recrysta l l i zat ion of the residue f rom alcohol results in 87.^ g of /3-furylmercury chloride; yield: 12% on the mercur ic acetate; m.p. 184.5°C.

The substitution of mercury for the carboxyl group can also be easily effected in a-thiophenecarboxylic acids, the reaction with mercuric acetate proceeding in the cold. In some cases this reaction is accompanied by mercuration. Thus, the reaction between HgO in acetic acid and a-thiophenecarboxylic acid con-taining labeled sulfur leads to tetra-acetoxymercurithiophene [90], 2,3-Dichloro-2-thiophenecarboxylic acid gives 2,3-dichloro-4,5-dichloromercurithiophene when kept for 3 hours in a solution of HgO in acetic acid. By contrast, 2,3-dibromo-5-thiophenecarboxy-Iic acid is not mercurated under these conditions and only the CO2H


mula

O COOHgOOCCHs


group is replaced by mercury to form 2,3-dibromo-5-chloromer-curithiophene [91]. The carboxyl group is replaced by Hg in 4,5-di-iodo-3-thiotoluene-2-carboxylic acid when the latter is heated with HgCl2 in acetic acid, the replacement in the corresponding 5-mono-iodo compound being effected by the action of mercuric acetate in acetic acid (heating on a water bath) [92].

Preparation of 2,3-dichloro-4,5-dichloromercurithlophene [92]. 2,3-Dichloro-5-thio-phene carboxylic acid (40 g) in 200 ml of glacial acetic acid is added to a hot solution of 130 g of mercury acetate in 240 ml of glacial acetic acid. Liberation of CO2 begins al-most immediately. The reaction mixture is gently boiled and vigorously stirred. The separation of a white precipitate of 2,3-dichloro-4,5-diacetoxymercurithiophene starts within 15 minutes and the material is f i ltered off 3 hours later. An additional amount is precipitated f rom the fi ltrate with water. The portions are combined and boiled with an excess of sodium chloride to convert the precipitate into 2,3-dichloro-4,5-dichloro-mercurithiophene; the substance is infusible.

For the synthesis of the asymmetrical derivatives of mercury by the scheme [93, 94]:

RCOOAg + ClHgR' AgCl + RCOOHgR' -> CO2 + RHgR'

see Chapter 12.

e) Substitution of Mercury for Heavy Metals and Some Metalloids

This method is based on the reaction

RmM„Hal„_m +mHgHal, RHgHal + MmHaln

where R is an aliphatic or an aromatic residue and M denotes a metal such as Sn, Pb, Sb, Bi, or Tl . The reaction takes place in various organic solvents and leads, with a sufficient amount of mercuric halide, to complete substitution of mercury for the other metal. This method has been used with the mixed and unmixed aromatic and aliphatic compounds of tin (aromatic [95-98, 114], alkyl [99, 100], alkenyl [101-110]), lead (aromatic [95, 111-114, 116], aliphatic [114-120]), trivalent antimony (aromatic [95, 121, 122], chlorovinyl [103, 104, 123]; in particular, this reaction gave cis -(3-chlorovinylmercury chloride [123] for the first time) and bismuth (aromatic [124-126], aliphatic [127, 128]). Further com-pounds include diphenylcadmium [129] and the salts of monoaryl-thallium [14, 130-132] and diarylthallium [132]. The reaction takes place even in the cold and is very fast when the reactants are boiled in an organic solvent, preferably alcohol, other good solvents being acetone, ether (for diphenylcadmium, perfluoro-vinyltributyltin [102a], triethyltin [110] and di- and tributylvinyltin [102]) and acetic acid (for tetraethyl-lead [133]).

This reaction also takes place with a heterocyclic compound of


arsenic, trifurylarsine, when the latter is reacted with HgCl2 in an aqueous-alcoholic medium [134]. Compounds of the type of Ar3Sb1HgCl2 decompose on being boiled in alcohol to give rise to ArHgCl (Ar = m- and p-tolyl [121], p-anisyl and p-phenethyl [122]). When Ar is o-tolyl, no ArHgCl is formed under these conditions [121].

On being boiled for a long time in acetic acid, aromatic arsine oxides can arylate mercuric acetate [135], By contrast, the tr i -fluoromethyl derivatives of mercury cannot be obtained by the action of (CF3)As on mercuric iodide (2 days at 105°C or 1 day at 175°C), or by the action of CF3AsCl2 on mercury and hydrochloric acid, or by the action of (CF3)2AsHal (Hal = Cl or I) on Hg+ [135a],

Diarylmercuries and dialkenylmercuries are invariably obtained when HgO is reacted in a boiling aqueous-alcoholic alkaline medium with aryltins [95, 96], alkenyltins [106, 107]) and the aryl deriva-tives of lead [95], Sb(III) [95], As(III) [95, 136, 137] and Bi [124]. Asymmetrical organomercuries are obtained under the same condi-tions with these compounds and alkyl- or arylmercury hydroxide (in practice, alkylmercury or arylmercury chlorides are used, in the presence of an alkali) (see Chapter 12).

Compounds of the type of R2Hg (R = CH3, C2H5) are obtained when Hg2(NO3)2 is reacted in methanol at 25° C with R4Pb [137a] or R4Sn [138],

When tetraethyl-lead and mercury pentachlorophenoxide are mixed for several hours in a ball mill in the presence of an inert carr ier (talc) and alcohol, a reaction takes place and the corres-ponding salt of ethylmercury is formed [118].

The reactions between the olefinic organometallics (particularly the quasicomplexes) and mercury salts or metallic mercury (see below) proceed with particular ease and, likethe reverse reactions, with retention of the stereochemical configuration of the radical that is being exchanged (see Chapter 6).

Arylthallium di-isobutyrate can be used (Glushkova andKochesh-kov [130-132]) to give organomercuries with mercuric halides; this method has been used to establish the structure of arylthallium diacylates obtained through the thallation of aromatic compounds by the method of these authors.

ArPbX3 compounds, which had previously been inaccessible, have been prepared by a method of PanovandKocheshkov [112], in which equimolecular amounts of diary 1-lead diacylates are reacted with mercury acylates (acyl = acetate, isobutyrate) in the corresponding acids at room temperature; this reaction also leads to arylmercury salts [112].

Except for the patented methods mentioned above, all the opera-tions can be carried out in the same manner, as illustrated by the following examples.

Synthesis of methylmereury chloride [ lOO]. Tetramethyl t in (3 g, 0.016 mo l e ) is added to a solution of 9 g (0.033 mo l e ) of HgCl 2 in 40 ml of absolute alcohol. The temperature



increases and a flaky precipitate appears. After the reaction has come to an end, the precipitate is f i ltered off (m.p. 170°C). The following products are obtained from the filtrate by fractional crystallization: methylmercury chloride (m.p. 170°C, f irst and second fraction), crystals melting between 120 and 140°C (third fraction, a mixture of methylmercury chloride anddichlorodimethylstannane)anddichloromethylstannane (fourth fraction, after evaporation of the alcohol and recrystallizationfrom ligroine, m.p. 107°C). Methylmercury chloride is obtained in a yieldof7.4 g (89%) and dimethyldichlorostannane in a yield of 3.2 g (87%). The third fraction (0.22 g) is not taken into account.

Synthesis of cis-/3-chlorovinylmercury chloride [123]. A solution of 5 g (0.0163 mole) of cts-tri-/9-chlorovinylstibine (for the preparation see [166]) in 10 ml of absolute ethanol is added to -a solution of 13.3 g (0.0483 mole) of HgCl2 in 40 ml of absolute ethanol. The reaction mixture is stirred for an hour at room temperature, after which 50 ml of a 10% solution of HCl are added and the resulting precipitate fi ltered off and dried. The crude product weighs 14 g (96%). After three recrystallizations from 60-90°C petroleum ether, the melting-point is 78.5-79°C.

Synthesis of Jrans-^-chlorovinylmercury chloride [ lO l ] . To a solution of 0.35 g (0.00128 mole) of HgCl2 in 2 ml of absolute ethanol is added 0.2 g (0.00064 mole) of trans - di-^S-chlorovinyltin dichloride (m.p. 77.5-78.5°C). The reaction mixture is heated to 50°C for 30 minutes and then set aside at room temperature for 1 hour. The resulting white needle-shaped crystals are fi ltered off, dried and weighed (0.2 g). A further 0.15 g can be isolated from the mother liquor. After recrystallization from benzene, the product melts at 123°C (with decomposition). Yield: 0.35 g (92%).

Synthesis of phenylmercury chloride [95]. Diphenyltin dichloride (1.72 g, 0,005 mole) is dissolved in 10 ml of alcohol. The solution is heated to the boil, and a boiling solution of 2.71 g (0.01 mole) of HgCl2 in 10 ml of alcohol quickly added. Phenylmercury chloride precipitates out at once and is f i ltered off, washed with alcohol and dried. Weight: 2.75 g (90%); m.p. 252°C.

Synthesis of perfluorovinylmercury chloride [ l i o ] . A solution containing 6.0 g (0.021 mole) of triethylperfluorovinyltin and 57 g (0.021 mole) of HgCl2 in 25 ml of ether is boiled for 8 hours. Two-thirds of the ether are then distilled off and the residue treated with 75 ml of pentane. The precipitate is filtered off (4.0 g, m.p. 93-97°C) and redistilled at 70°C/10mm. Yield of perfluorovinylmercury chloride: 3.4 g (51%); m.p. 106°C.

Synthesis of p-anisylmercury chloride [ l30] . A solution of 1 g of HgCl2 in 15 ml of alcohol is added to a solution of 1 gof p-anisylthallium di-isobutyrate in 15 ml of alcohol and the mixture heated for 15 minutes on a water bath (brown precipitate). Hydrochloric acid is then added dropwise until the color fades. The precipitate is then filtered off, washed with alcohol and absolute ether, and recrystallized from alcohol; m.p. 239-240°C.

p-Anisylmercury bromide (m.p. 250-250.5°C) is prepared in the same manner (in acetone [130]).

Dicyclopentadienylmercury has been obtained in a quantitative yield and without an admixture of cyclopentadienylmercury chloride by the reaction of cyclopentadienylthallium with HgCl2 in tetra-hydrofuran at -30 to -40°C [139]. This is the best method for the preparation of dicyclopentadienylmercury.

Synthesis of dicyclopentadienylmercury [ l39] . A mixture of 15 ml of dry tetrahydro-furan and 6.0 g of cyclopentadienylthallium (prepared on the previous day and dried over-night over calcium chloride) is placed in a flask fitted with a stirrer, a dropping funnel and a CaCl2 tube. The mixture is cooled to -40 to -50°C and stirred. A solution of 2.35 g of HgCl2 in 30 ml of tetrahydrofuran is then added over 2!4 hours. The mixture


is kept f o r an hour at --30 to -40°C, af ter which a negative test is obtained f o r the pre -sence of mercur i c ions with a drop of the solution and alkali. The precipitate (5.17 g ) is rapidly f i l t e red off, washed twice on the f i l t e r with 7 -m l portions of tetrahydrofuran and dried in air. Vacuum sublimation leads to the recovery of 0.26 g of cyclopentadienyl-thallium f r om the precipitate. The solution is quickly (in 20-25 minutes) evaporated to dryness, without heating, on a water pump. The residue is rapidly treated with portions (20 + 20 + 10 m l ) of absolute ether and the needles of l emon-co lored dicyclopentadienyl-mercury separating out on cooling to -40°C isolated by decantation, washed with 5-7 ml of absolute ether and dried on f i l t e r paper within 5 minutes. Weight 2.21 g. A f u r t h e r 0.64 g are obtained by evaporation of the ethereal solution. Yie ld: 97.5% on the starting HgCl2- Af ter recrysta l l i zat ion f r om absolute ether the melting-point is 82-83.5°C (with decomposit ion). Dicyclopentadienylmercury is stable only at -30 to -40°C.

Synthesis of a-thieny lmercury bromide from a-thieny Ith allium di-isobutyrate and mercuric bromide [ l 3 l ] . Me rcur i c bromide (0.4 g ) d issolved in 4 ml of alcohol is added to a solution of 0.3 g of a-thienylthall ium di- isobutyrate in 2 ml of alcohol. On being heated f o r 15 minutes, the mixture g ives a brown precipitate. After the solution has been cooled, HBr is added dropwise until the co lor fades. The precipitate is then f i l t e red and recrys ta l l i z ed f r o m acetone; m.p. 168°C.

Synthesis of diphenylmercury [95]. A boiling aqueous 5N solution of NaOH (30 ml ) is added to a solution of 1.72 g (0.005 mo le ) of diphenyltin dichloride in 10 ml of alcohol. White diphenyltin oxide precipitates out. The reaction mixture is kept boiling and a hot solution of 1.35 g (0.005 mo l e ) of HgCl 2 in 8 ml of alcohol added: yel low mercur i c oxide precipitates out at once, which disappears in 5-6 seconds and is replaced by a white precipitate. The mixture is cooled f o r 1 minute, 30 ml of water added and the precipitate f i l t e red of f . It is found to be pure diphenylmercury; m.p. 125°C; weight: 1.7 g [1],

Reaction of diphenyl-lead diacetate with mercuric acetate. Synthesis of phenylmercury acetate and phenyl-lead triacetate [ 112]. Mercur i c acetate (1.92 g, 1 mo l e ) is dissolved in 40 ml of glacial acetic acid on gentle heating, the solution cooled to room temperature and 2.88 g (1 mo l e ) of diphenyl-lead diacetate added. The latter d isso lves readi ly . By the next day the reaction is virtually complete and 1.28 g of a 4.7N solution of HCl in alcohol (corresponding to 1 mo le ) are added f r om a microburet to convert the resulting phenylmercury acetate into phenylmercury chloride. The precipitate f o rmed is f i l t e red and washed with alcohol; m.p. (after recrystal l i zat ion f r om xylene) 258°C; y ie ld : 1.68 g (80%). The f i l t ra te is kept over KOH in a vacuum desiccator until the acetic acid has evaporated. The solid residue (3.63 g ) is dissolved in 15 ml of hot anhydrous f r esh ly -dist i l led ethyl acetate and f i l tered. The f i l t rate is cooled with a mixture of salt and ice and the resulting crysta ls f i l t e red off and washed with hexane. Y ie ld of phenyl-lead t r i -acetate: 2.19 g (79%); m.p. 101-102°C. The product is recrys ta l l i zed f r o m ethyl acetate.

Synthesis of di-p-ch loropheny lmercury [95] . Boil ing 5N aqueous NaOH (5 m l ) i s added to solution of 0.27 g (0.001 mo le ) of HgCl2 in 3 ml of alcohol and 0.6 g (0.002 mole ) of p-chlorophenylantimony dichloride, in 4 ml of alcohol, combined previously in the cold. A gray solid precipitates out. A f ter addition of 25 ml of water the precipitate is f i l t e red off and extracted with hot acetone, giving0.34 go f d i -p-ch loropheny lmercury (80%). A f ter recrysta l l i zat ion f r o m acetone, the product melts at 242°C.

Synthesis of a-furylmercury chloride [ l 3 4 ] . A solution of 1 g of t r i fury lars ine in 20 ml of ethanol is combined with a solution of 3.2 g of HgCl 2 in 100 ml of water and alcohol, and the mixture is heated to boiling. a -Fury lmercury chloride crys ta l l i zes out on cooling. Water is then added and the precipitate f i l tered off . Y ie ld : 1.6 g (60%); m.p. 151°C.

Fully substituted mercury derivatives are obtained when metallic mercury interacts with di-/6-chlorovinyl-lead [140], diaryl-lead [140], alkenyl derivatives of thallium R2TlX in alcohol or acetone, in the cold or onheating[103,104,141-147], trimethylthallium [148]



in ether at room temperature, triphenylthallium (boiling in benzene) [149] and diphenylthallium bromide (boiling in pyridine) [149].

Synthesis of di-c£s-/3-chlorovinylmercury [ l 4 l ] . D i - cis -/3-chlorovinylthall iumchlo-r ide (0.1 g ) is shaken f o r 90 hours with 0.4 g of metal l ic mercury in 10 ml of methanol at room temperature. The precipitate and the unreacted mercury are f i l t e red off and thal-Ious chlor ide removed by decantation. The weight of the metal l ic mercury is 0.35 g and that of the thallous chloride 0.06 g (theoretical ) . T h e alcoholic f i l t ra te is evaporated to dryness under vacuum and the residue extracted with petroleum ether. Evaporation of the solvent on a water bath, on a water pump, leaves behind a liquid, which is found to be d i - c i s -/3-chlorovinylmercury. Weight: 0.09 g; nD21 1.6152.

Synthesis of di- ( l-methyl-2-acetoxy-l-propen-l-yl )mercury [143]. D i - ( l - m e t h y l - 2 -ace toxy- l -propen- l -y l ) tha l l ium chlor ide (0.25 g), 40 ml of acetone and 2.3 g of metal l ic mercury are placed in a two-necked cyl indrical f lask f i tted with a s t i r r e r and a ref lux condenser and the reactants heated, with vigorous st i rr ing, f o r 10 hours at 60°C. The solution is then separated f rom the thallous chloride and the unreacted meta l l ic mercury . The f i l t ra te is evaporated to dryness and the residue extracted with benzene. Removal of the benzene by distil lation leaves behind a crysta l l ine product melting at 107-111°C. A f t e r being twice recrys ta l l i z ed f r o m 40-60 petroleum ether, it melts at 112-113°C. The yie ld of the recrys ta l l i z ed product is 0.09 g (40.9%).

Ethylmereury chloride has been obtained in a yield of 15% by heating tetraethylsilane with HgCl2 to 140-150°C for 2 hours in the absence of solvent [100], Aryltrimethylsilanes also arylate mercury acetate at 25°C in glacial acetic acid, giving rise to aryl-mercury acetates [150, 151]. When heated to 110°C, the compound [(C6H5)3SiO]2Hg rearranges into (C6H5)3SiOHgC6H5 [152].

Synthesis of phenylmercury chloride from trimethylphenylsilane and mercuric acetate [150]. A solution of 15 g (0.1 mo l e ) of trimethylphenylsilane and 3.6 g (0.011 mole ) of mercur i c acetate in 200 ml of g lac ia l acetic acid is set aside at room temperature until the reaction reaches completion (test f o r the absence of Hg ions). The mixture is then poured into an excess of NaCl. The precipitate is f i l t e red off and dried. Y i e ld of phenyl-mercury chloride: 3.25 g (92%); m.p. 249-250.5°C.

The following compounds have been obtained in the same manner: o- and p-tolylmercury chlorides, 3- and 4-chloromercuri-o-xy-lenes, chloromercuri-p-xylene and 2-, 4- and 5-chloromercuri-m -xylenes [150].

Mercury salts have not yet been alkylated with organogermaniums. bis-Cyclopentadienylphenyltitanium phenylates both HgCl2 and

metallic mercury, forming phenylmercury chloride [153], These reactions are carried out in chloroform (in the first case also in benzene; the yield of phenylmercury chloride is 90%).

When heated with HgO at IOOcC for 36 hours in a sealed tube, perfluorotrimethylphosphine gives diperfluoromethylmercury in a yield of 96% [154].

Pentaphenylantimony [155] and pentaphenylphosphorus [156, 157] arylate metallic mercury. When they are shaken for several days with metallic mercury in chloroform at room temperature, phenyl-mercury chloride is obtained in a quantitative yield, together with


tetraphenylantimonium chloride (or the corresponding phosphorus compound), and other products.

Triphenylbismuth (2 g) interacts with metallic mercury (14 g) when heated to 250°C for 10 minutes, to give a mixture of 74% of triphenylbismuth, 24% of diphenylmercury and 2% of biphenyl [158].

The triphenylchromium complexes (C6H5)3Cr1(THF)3, (C6H5)3

Cr.(THF)3 .3MgClBr.(THF)3 react with HgCl2 in tetrahydrofuran to give phenylmercury chloride quickly and quantitatively [159, 160]. The penta-aquobenzylchromium cation in water interacts with HgCl2

to give benzylmercury chloride in a low yield [161]:

C6H5CH2Cr (H2O)5++ + HgCI2 + H2O C6H5CH2HgCl + Cr(H2O)6++ + Cl"

By contrast, the penta-aquo(dichlorometnyl)chromium cation [Cl2CHCr(H2O)5]+4" does not react with mercuric chloride [162],

The presence of C - Z r a-bonds in the cyclopentadienyl deriva-tives of zirconium that contain aryl groups, (C5H5)2 ArZr2 O (Ar = C6H5, P-CH3C6H4) is shown by the formation of a small amount of ArHgCl on reaction with HgCl2 at 60-65°C (stirring for 2 hours in tetrahydrofuran) [163]. The reaction between mercuric chloride and Tr-C5H5Fe(CO)2C6H5-CT leads to phenylmercury chloride in a good yield [164].

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159. W. Herwig and H. H. Zeiss, J. Am. chem. Soc., 79, 6561 (1957).

160. W. Herwig and H. H. Zeiss, ibid., 81, 4798 (1959). 161. F. A. L. Anet and E. Leblanc, ibid., 79, 2649 (1957). 162. F. A. L. Anet, Can. J. Chem., 37, 58 (1959). 163. E. M. Brainina, G. G. Dvoryantseva and R. Kh. Freidlina,

Dokl. Akad. Nauk SSSR, 156, 1375 (1964). 164. A. N. Nesmeyanov, Yu. A. Chapovskii and L. G. Makarova,

Izv. Akad. Nauk SSSR, Ser. Khim., 1310 (1965). 165. M. P. Newell, M. F. Argus and F. E. Ray, J. Am. chem.

Soc., 78, 6122 (1956). 166. A. N. Nesmeyanov and A. E. Borisov, Izv. Akad. Nauk SSSR,

Otdel. khim. Nauk, 251 (1945).

CHAPTER 10

Synthesis of Organomercury Compounds by the Action of Free Radicals

(from Peroxides and Other Sources) on the Mercury Salts of Carboxylic and Other Acids and on Metallic Mercury

A new method of synthesizing alkyl and arylmercury derivatives has been proposed by Razuvaev and Ol'dekop [1, 2], consisting in the decomposition of mercury salts of carboxylic acids, initiated by free radicals provided by acyl peroxides. In general form, the reaction may be written

(RCOO)2Hg + (RrCOO)2 R'HgOOCR + RHgOOCR + 2C02

In view of its recent discovery, the method has not yet gained the wide application that it deserves. It offers a possibility of obtaining good yields of compounds RHgX from easily available materials, R being mainly aliphatic but also alicyclic or aromatic. On the other hand, the R group obviously must not contain inhibitor sub-stituents which would react with the peroxides, such as amino groups, hydroxyl and so on. In the synthesis of the aliphatic de-rivatives, the advantage of this method over the commonest method of preparing aliphatic organomercury salts (via organolithiums and organomagnesiums) is that it is possible to make RHgX with sub-stituents such as the halogens, and that it is unnecessary to work with absolute solvents and with a solvent such as ether.

In contrast to mercuration, synthesis of the aromatic organo-mercuries by this free-radical method gives isomer-free individual products, similarly to the diazo method, but, unlike the situation in the latter case, compounds containing reducing group or in-hibitors of chain reactions cannot be prepared. In the aromatic series, the method has so far been applied only to the synthesis of phenylmercury salts.

In the alicyclic series, the method has been tried on only one example.

276

SYNTHESES BY THE ACTION OF FREE RADICALS 277

a) Decomposition of Peroxides in the Presence of Mercury Salts

(Unless otherwise stated, the yields in this section are calculated with respect to the mercuric salt.)

The reaction proceeds by a chain mechanism:

(RCO2)2 2RC02 (1 )

RCO2 • —> R • + CO2 (2)

R I

(R-CO2)2Hg + R • - (R-CO2HgO2CR') - RHgO2CR' + R1CO2 (3 )

R-CO2--* R'- + C O 2 (4)

(R-CO2)2 Hg + R'--+ R-HgO2CR' + R'C02 (5)

R-CO2-* R ' . + C O 2 (6)

so that if R and R' are different, the products are a mixture of organomercury compounds; this is a disadvantage of the method.

The mercuric salts are decomposed on heating in benzene or some other solvent, best of all in glacial acetic acid (or, in the case of acyl peroxides, in the acid from which the peroxide is derived), in the presence of 0.05-0.1 mole of peroxide per mole of the mercuric salt.

In the decomposition of mercury acetate with acetyl peroxide in glacial acetic acid, the yield of the methylmercury salt reaches 99% on the starting mercury salt (and over 100% on the peroxide, indicating that the reaction proceeds by a chain mechanism).

Apart from acetyl peroxide [1, 2, 19], the peroxides used to initiate the decomposition of mercuric acetate are dibenzoyl peroxide [1-4] (at 98°C, in CH3COOH, the yield of methylmercury salt is 95.5% [4]; after 12 hours of boiling in benzene the yield of the methylmercury salt is 54% [2] (70% [4]) and that of phenyl-mercury salt 41.7% (on the benzoyl peroxide) (11.7% [4])), d i -w-nitrobenzoyl peroxide [5] (in acetic acid, the yield of the methyl-mercury salt is about 70%), di-t-butyl peroxide [6] (19 hours of boiling in acetic acid gives a 50% yield of methylmercury salt) diacetylated cyclohexyl 1,1-dihydroperoxide [4] (heating to 80 and 98°C in acetic acid or boiling in benzene; the yields of methyl-mercury salts are, respectively, 95.4, 98 and 96.5%), dicyclohexyl peroxydicarbonate [3, 7] (heating to 98°C in acetic acid; the yield of methylmercury acetate is 83%).

During its decomposition, t-butyl peroxide generates methyl radicals; the decomposition of mercuric trimethylacetate with



this peroxide gave, after 24 hours in boiling chlorobenzene a 35.7% yield of the methylmercury salt [8]. A methylmercury salt was also obtained from mercuric benzoate and t-butyl peroxide in chlorobenzene (20 hours' boiling) [6], in a yield of 20%. The action of acetyl peroxide dissolved in diethyl phthalate on a solution of HgO in a mixture of acetic acid and acetic anhydride at 90°C re-sulted in a 90% yield of methylmercury acetate [9].

The effects of the reaction conditions on the yields of products forming in the decarboxylation of mercuric acetate under the action of free radicals (from diacetylated cyclohexyl 1,1-dihydroperoxide and benzoyl peroxide) have been investigated [9a]. The decomposi-tions were conducted in acetic acid at 80 and 97-98°C, and also in benzene at 80°C. In the decompositions in acetic acid by the action of the diacetylated cyclohexyl 1,1-dihydroperoxide, the yield of methylmercury acetate was 94-95% at 80°C and 98% at 98°C. The increased temperature reduced the reaction time from 3-3!^ hours to 40-60 minutes. During the decomposition of mercuric acetate with diacetylated cyclohexyl 1,1-dihydroperoxide in benzene, the yield was increased by adding acetic acid.

In the decomposition of mercuric acetate by the action of benzoyl peroxide in acetic acid at 80°C, the yields of the methylmercury and phenylmercury salts were, respectively, 87 and 5.3%. When the temperature was raised to 97-98°C and more benzoyl peroxide added, the yield of the phenylmercury salt rose to 60% whereas that of the methylmercury salt fell to 39%. The above rise in tem-perature also reduced the time of the reaction from 6-7 hours (at 80°C) to iy2-2 hours.

In the decomposition of mercuric acetate carried out in benzene by the action of benzoyl peroxide, the reaction was strongly ac-celerated by the addition of a little acetic acid, and, at 80°C, the yields of both methylmercury and phenylmercury salts were then enhanced. At the same temperature but in the absence of acetic acid, 34% of the mercuric acetate remained unreacted.

The decomposition of mercuric propionate in propionic acid in the presence of propionyl peroxide gives an 89% yield of ethyl-mercury salt [3, 10]. On the other hand, the decomposition of mercuric propionate in propionic acid in the presence of benzoyl peroxide (at 97-98°C) gave the ethylmercury salt in 54% yield and a phenylmercury salt in a yield of 16%; when the same reaction was carried out in benzene at 80°C, the main product was the phenylmercury salt (yield: 50%) and the yield of the ethylmercury salt fell to 24% [10] (34% according to [2]). Hydrogen peroxide has also been used to initiate the decomposition of mercuric propionate [10]; the reaction was carried out in a mixture of propionic acid and propionic anhydride at approximately 100°C. The yield of the ethylmercury salt was 76%. The decompositions of mercuric mon<- -chloroacetate in boiling benzene with benzoyl peroxide and mi. . j -chloroacetyl peroxide resulted in respectively up to 60 and 45%


yields of phenylmercury salt; chloromethylmercury monochloro-acetate was also formed in the latter case [3, 11]. An analogous picture is observed in the decomposition of mercuric n-caprate with benzoyl peroxide or n-decanoyl peroxide in benzene: the yields of the phenylmercury salts were, respectively, 88.5 and 16.5%; the yield of nonylmercury salt in the latter case was 46.5% [3, 12].

In the decompositions with benzoyl peroxide in these and similar cases, the phenylmercury salt is formed both as a result of an exchange of the alkyl radical for the phenyl radical provided by the peroxide and as a result of mercuration of the benzene with mercuric acetate (see Chapter 5).

Heating of camphenonyl peroxide with the mercury salt of camphenonic acid in the absence of solvent, at 70-80°C, proved to be the only way of obtaining a-chloromercuricamphenilone [13] (after precipitation with KCl).

Mercuric trimethylacetate boiled for 10 hours in benzene in the presence of benzoyl peroxide gave [8] the phenylmercury salt in a yield of 94.8% (calculated on the benzoyl peroxide).

A description of the formation of phenylmercury salt containing labeled carbon during the decomposition of mercuric acetate in benzene containing14 C, initiated by benzoyl peroxide, will be found in [14].

Preparation of methylmercury salts from mercuric acetate and acetyl peroxide in acet ic acid [2 ] . Mercur i c acetate (58.8 g), 230 ml of g lacial acetic acid, 3.0 ml of acetic anhydride and 2.0 g of acetyl peroxide are heatedfor i hour, with mechanical st irr ing, on a boi l ing-water bath, in a three-necked f lask provided with a ref lux condenser. At the end of the reaction, 2-3 volumes of water are added and methylmercury iodide precipitated with NaI. Y ie ld : 62.8 g (99% on the mercur i c acetate). Methylmercury acetate can be obtained f r om the acetic acid solution by careful evaporation of the reaction mixture; after sublimation, the melting-point is 128°C.

Reaction of mercuric propionate with propionyl peroxide in propionic acid. Preparation of ethylmercury sal ts [ i o ] . (a) Preparation of the solution of the propionyl peroxide in propionic acid: 10 ml of 27% H2O2 are added to a mixture of 52 g of propionic anhydride and 2 g of NaOH, with continuous st i rr ing and cooling with snow and water. The peroxide content in the solution is estimated iodometr ical ly .

(b) Reaction of mercur ic propionate with propionyl peroxide at 97-98°C: 44.0 ml of a propionic acid solution of propionyl peroxide, containing 8.95 g (0.06 mo l e ) of the per -oxide, are added in 5-ml portions, over 2 hours, to a heated mixture of 10.4 g (0,03 mole ) of mercur ic propionate in 100 ml of propionic acid. The heating and st i r r ing are con-

Jtinued f o r 3 Y2 hours. Ethyl acetate and propionic acid are then dist i l led off f r om the reaction mixture (the acid under vacuum). The residue is dissolved in water, and 4.8 g of ethylmercury chloride precipitated f r om the solution with NaCl. Af ter recrysta l l i zat ion of the compound f r o m alcohol and ether, the melting-point is 194°C; y ie ld: 61.5%. An ex-cess of KI added to the mother liquor g ives 2.82 g of ethylmercury iodide; m.p. 181°C (after sublimation). The over -a l l y ie ld of ethylmercury salts is 88.8%.

Reaction of mercuric propionate with hydrogen peroxide in a mixture of propionic acid and propionic anhydride. Synthesis of ethylmercury salts [ lO j . With st i rr ing, 10 ml of 42% H 2 O 2 are added over 23 minutes, at room temperature, to a mixture of 10,4 g (0,03 mole ) of mercur ic propionate, 100 ml of propionic acid and 40 ml of propionic anhydride, placed in a four-necked flask f itted with a s t i r r e r (mercury seal) , a ref lux condenser, a dropping funnel and a thermometer . The whole mixture is s t i r red f o r another 25 minutes, the temperature ra ised to 97-98°C and the st i rr ing continued f o r 2 hours. Initially, violent

Rcfercnccs see page 282


evolution of gas takes place. This comes to an end within 1)4 hours. Metall ic mercury is removed from the reaction mixture and the solvent distilled off under vacuum. The residue is dissolved in water and ethylmercury chloride precipitated f rom the solution by means of KCl. Yield: 5.57 g (70.0%). The action of an excess of KI on the mother liquor gives 0.68 g (6.35%) of ethylmercury iodide. The over-al l yield of ethylmercury salts is 76.35%.

The decomposition of the mercurous salts of carboxylic acids with peroxides also leads to the formation of organomercury salts; the yields are comparable to those obtained with mercuric salts.

Prolonged boiling of mercurous acetate in benzene in the pres-ence of acetyl peroxide gave [2] a methylmercury salt in a yield of 49% on the starting peroxide; in the presence of benzoyl peroxide the product was a phenylmercury salt (yield: 29% on the peroxide) [2], and in the presence of t-butyl peroxide in acetic acid a 36% yield of methylmercury salt was obtained [6] (the latter decomposi-tion carried out in boiling chlorobenzene resulted in an 18% yield of the methylmercury salt; the yield of the methylmercury salt with diacylated cyclohexyl 1,1-dihydroperoxide is 70-80% in benzene and acetic acid, and with 1,1' -bis-acetoperoxydicyclohexylperoxide is 100% in benzene and 80% in acetic acid [31]. Dibenzoylated cyclo-hexyl 1,1-dihydroperoxide, l , l ' -bis-benzoylperoxydicyclohexylper-oxide also give under these conditions high yields of phenylmercury acetate with mercuric acetate [32].

In the decomposition of acetyl peroxide in acetic acid in the presence of HgSO4, HgI2, Hg2SO4 and Hg2Cl2, the yields of the methylmercury salts are very low. No ethylmercury salt is formed when this decomposition is carried out in the presence of mercuric chloride [15].

b)Decomposition of Mercury Salts Initiated by Radicals Generated by Irradiation with Ultra-violet

The alkyl radicals initiating the decarboxylation of mercury salts and alkylating the mercury can also be produced from these salts themselves, under the action of ultra-violet light [16, 17]:

hv

(RCO2)2Hg -> RCOOHg- + RCO2'

RCO2- R' + CO2

R- 4- "HgCOOR RHgCOOR

Irradiation of mercuric or mercurous oxide in glacial acetic acid, or of mercuric propionate in propionic acid [17, 18] or in benzene, results in up to 70% yields of methyl- and ethylmercury salts [16, 17, 19, 20]. Mercuric acetate in benzene gives on ir-radiation a 30-34% yield of methylmercury acetate [14, 19, 20]: The same behavior is observed with mercuric n-butyrate in benzene [20], mercuric benzoate in acetone and chlorobenzene,


and mercuric naphthoate in benzene [33]. Mercuric caproate in benzene gave a 45.5% yield of an n-nonylmercury salt [34]. On the other hand, the irradiation of trimethylacetate in benzene did not lead to the formation of an organomercury compound but led only to the separation of metallic mercury [9],

Preparation of methylmercury iodide by irradiation of mercuric acetate [ l 6 ] . The experiment is ca r r i ed out in a quartz f lask f i t ted with a ref lux condenser. A PRK-4 m e r -cury lamp is placed in a quartz tube sealed horizontally into the f lask. The leve l of the reaction mixture is above the latter tube. The heat given out by the lamp is suff icient to keep the solvent at the boil. A solution of 25.0 g of mercur i c acetate in 135 ml of glacial acetic acid is i rradiated f o r IOhours, f r e e m e r c u r y separated off and 250 ml of water and 15 g of NaI added. The yield of methylmercury iodide is 19.0 g (71%).

c) Decompositions of Mercury Salts Initiated by Radicals Formed by Other Sources

The decarboxylations of mercuric salts can also be initiated by methyl radicals produced in the decomposition of leadtetra-acetate [21]. Here too the best reaction medium is glacial acetic acid. The decomposition is conducted by boiling with an excess of mercuric acetate until no more gas is evolved. The yield of the methyl-mercury salt is over 80% on the lead tetra-acetate (3.6% on the mercuric acetate) [21].

Like the peroxides (but to a much smaller extent), phenyl iodoso-acetate initiates the decarboxylations of mercuric acetate on boiling in acetic acid, anisole, or cumene, with the formation of a methylmercury salt [22], Boiling of phenyl iodosoacetate with metallic mercury in benzene or acetic acid gives, as a result of a reaction of the methyl radicals produced by thermal decom-position of the phenyl iodosoacetate with the forming mercurous acetate, methylmercury acetate (in the latter case, in a yield of 2.2%); no methylmercury salt is obtained when this reaction is carried out in the cold.

d) Decompositions of Peroxides in the Presence of Metallic Mercury

The yields given in this section are calculated on the peroxides. Organomercury compounds can also be obtained by the decom-

position of peroxides in the presence of metallic mercury [23, 24]. Alkylation (arylation) of the mercury occurs only when the reaction is carried out with boiling [25]. The usual solvents are benzene or acetic acid; lower yields are obtained in carbon tetrachloride. Methylmercury salts have been obtained (after additions of the corresponding anions) by the decompositions in the presence of metallic mercury of acetyl peroxide [23, 24] (after 20 hours of



boiling in benzene, the yield of the methylmercury salt was 64.7%), diacetylated cyclohexyl 1,1-dihydroperoxide [26] (the yield of methylmercury salt was 32.5% after 6-7 hours of boiling in ben-zene, 63.7% in acetic acid and practically zero in CCl4) and t-butyl peroxide [6] (a very small yield of methylmercury salt was obtained after 20 hours of boiling in acetic acid).

A phenylmercury salt has also been obtained from benzoyl peroxide [23] (31.5% yield after 20 hours of boiling in benzene [23], insignificant yield after heating in CCl4 [27]). The phenyl-mercury chloride obtained in very low yield by the decomposition of benzoyl peroxide in 14C6H6 in the presence of metallic mercury contained 3% of phenyl groups from the solvent [28],

Acetyl benzoyl peroxide boiled for 4Y2 hours in benzene in the presence of metallic mercury gave (after precipitation with NaCl and KI) 13.8% of phenylmercury chloride and 31.3% of methyl-mercury iodide [29], The decompositions of m-nitrobenzoyl ben-zoyl peroxide and p-nitrobenzoyl benzoyl peroxide (boiling in benzene for 11 and 20 hours, respectively) in the presence of metallic mercury gave only phenylmercury chloride, in low yields [29].

The radicals formed in the thermal decompositions of benzene and toluene become affixed to the mercury [30].

The reaction between acetyl peroxide and mercury in benzene [23]. (a) Preparation of the solution of acetyl peroxide: 10 g of potassium peroxide and 100 ml of benzene are placed in a wide-necked open flask or in a beaker and the mixture cooled with snow and ice to -10°C. The contents of the flask are st irred with a rapid mechanical s t i r rer to stop the benzene from freezing. Acetic anhydride is added drop by drop and the stirring continued for another hour. The solution is next treated with ice, at f i rst in small portions, until the potassium peroxide is fully decomposed. The benzene layer is separated off, washed with water and dried over sodium sulfate. The peroxide content is determined iodimetrically.

(b) Preparation of methylmercury iodide [23]: metallic mercury is placed in a three-necked flask (fitted with a mechanical s t i rrer (mercury seal), a dropping funnel and a reflux condenser) and covered with a shallow layer of benzene. The benzene is heated to boiling and a solution of 9.9 g of acetyl peroxide in 200 ml of benzene added, with stirring, f rom the dropping funnel (the end of which is below the surface of the benzene layer). The addition is slow (8 hours) and towards the end the reaction mass is heated on a water bath. The benzene layer is then heated for another 12 hours, separated from metallic mercury and washed with several portions of water. Addition of a saturated KI solution to the above aqueous extracts precipitates white methylmercury iodide; yield: 18.6 g (on the peroxide); m.p. 144-145°C.

Bibliography

1. G. A. Razuvaev, Yu. A. Ol'dekop and N. A. Maier, Dokl. Akad. Nauk SSSR, 98, 613 (1954).

2. G. A. Razuvaev, Yu. A. Ol'dekop and N. A. Maier, Zh. obshch. Khim., 25, 697 (1955).

3. N. A. Maier and Yu. A. Ol'dekop, Sb. nauch. Rab. Inst, f i z . -org. Khim., Minsk, 8, 113 (1960).

4. Yu. A. Ol'dekop and N. A. Maier, Zh. obshch. Khim., 30, 275 (1960).


5. G. A. Razuvaev and Yu. A. Ol'dekop, Trudy Khim. khim. Tekhnol., Gor'kii, 1, 178 (1958).

6. Yu. A. Ol'dekop and M. M. Azanovskaya, Zh. obshch. Khim., 30, 2291 (1960).

7. G. A. Razuvaev and L. M. Terman, Zh. Vses. khim. Obshch., 6, 473 (1961); Zh. obshch. Khim., 31, 3132 (1961).

8. Yu. A. Ol'dekop and T. V. Vasilevskaya, Zh. obshch. Khim., 28, 3008 (1958).

9. Czech. Pat. 98,129 (1959); Chem. Abstr., 56, 7356 (1962). 9a. Yu. A. Ol'dekop and N. A. Maier, Vest. Akad. Nauk belorussk.

SSR, Ser. fiz.-tekh. Nauk, 2, 37 (1960). 10. Yu. A. Ol'dekop and N. A. Maier, Zh. obshch. Khim., 30, 619

(1960). 11. Yu. A. Ol'dekop and N. A. Maier, ibid., 30, 3472 (1960). 12. Yu. A. Ol'dekop and N. A. Maier, ibid., 30, 3017 (1960). 13. A. N. Nesmeyanov and I. I. Kritskaya, Dokl. Akad. Nauk SSSR,

121, 447 (1958). 14. G. A. Razuvaev, G. G. Petukhov and B. G. Zateev, ibid., 127,

348 (1959). 15. Yu. A. Ol'dekop and N. A. Maier, Zh. obshch. Khim., 30, 299

(1960). 16. G. A. Razuvaev and Yu. A. Ol'dekop, Dokl. Akad. Nauk SSSR,

105, 738 (1955). 17. Yu. A. Ol'dekop and N. A. Maier, Dokl. Akad. Nauk belorussk.

SSR, 4, 288 (1960). 18. Yu. A. Ol'dekop and N. A. Maier1Dokl. Akad. Nauk SSSR, 131,

1096 (1960). 19. Yu. A. Ol'dekop and N. A. Maier, Zh. obshch. Khim., 30, 303

(I960). 20. Yu. A. Ol'dekop, N. A. Maier and V. I . Gessel'bert, Sb. nauch.

Rab. Inst. f iz . -org. Khim., Minsk, 8, 37 (1960). 21. G. A. Razuvaev, Yu. A. Ol'dekop, Yu. A. Sorokin and V. I.

Tverdova, Zh. obshch. Khim., 26, 1683 (1956). 22. Yu. A. Ol'dekop, N. A. Maier and A. V. Bystraya, Dokl. Akad.

Nauk belorussk. SSR, 6, 503 (1962). 23. G. A. Razuvaev, Yu. A. Ol'dekop and L. N. Grobov, Dokl. Akad.

Nauk SSSR, 88, 77 (1953); Zh. obshch. Khim., 23, 589 (1953). 24. G. A. Razuvaev, Sb. Voprosy khimicheskoi kinetiki, kataliza i

reaktsionnoi sposobnosti [Collection: problems of chemical kinetics, catalysis and reaction capacities], Izd-vo Akad. Nauk SSSR, Moscow, 1955, p. 790.

25. G. A. Razuvaev and Yu. A. Ol'dekop, Zh. obshch. Khim., 27, 196 (1957).

26. Yu. A. Ol'dekop and I. I. Chizhevskaya, Sb. nauch. Rab. Inst, f iz . -org. Khim., Minsk, 7, 68 (1959).

27. G. A. Razuvaev, Uchen. Zap. gorkov. gos. Univ., 15, 81 (1949). 28. V. N. Latyaeva, Sb. nauch. Rab. Inst. f iz . -org. Khim., Minsk.

8, 58 (1960).


29. G. A. Razuvaev, Yu. A. Ol'dekop and V. N. Latyaeva, Zh. obshch. Khim., 26, 1110 (1956).

30. F. Hein and H. J. Mesee, Ber. dt. chem. Ges., 76, 430 (1943). 31. Yu. A. Ol'dekop, N. A. Maier and V. N. Pshenichnyi, Zh.

obshch. Khim., 34, 317 (1964). 32. Yu. A. Ol'dekop, N. A. Maier and V. N. Pshenichnyi, Zh.

obshch. Khim., 35, 904 (1965). 33. N. A. Maier, V. I. Gesel'berg and Yu. A. Ol'dekop, ibid., 32,

2030 (1962). 34. Yu. A. Ol'dekop and N. A. Maier, ibid., 32, 1441 (1962).

CHAPTER 11

Preparation of Organomercury Compounds by Electrolysis

Several methods of electrolytic synthesis of organomercury compounds have been proposed, but their application is still rather limited.

(1) Preparation of symmetrical organomercuries by the elec-trolytic reduction [1] of ketones on a mercury cathode.

2RR'CO + Hg + 6H' (RR'CH)2Hg + 2H„0

This reaction yields full mercury derivatives of hydrocarbons with secondary radicals (the case in which the ketone function is pre-served and a primary organomercury compound is formed will be described at the end of this chapter.

(2) Preparation of fully substituted aliphatic mercury compounds by the electrolysis of NaBAlk4 or NaAlAlk3OR on a mercury anode:

NaMeAlk4 + Hg - » Alk2Hg +MeAlk 3

(3) Preparation of compounds (RHg)7l by the electrolysis of organomercury salts in liquid ammonia.

(4) Electrolytic symmetrization of organomercury salts (see Chapter 13).

The formation of fully substituted organomercury compounds, which accompanies the production of corresponding alcohols in the electrolytic reduction of ketones on a mercury cathode, can become the predominant reaction under suitable conditions (mainly temperature, and also concentration, current magnitude and current density, and the duration of the process).

Thus, the electrolysis of acetone resulted in the production of di-isopropylmercury and isopropanol [2] and the electrolysis of methyl ethyl ketone [1], under conditions described below, gave di-s-butylmercury in yields of up to 30%. In the latter case, a mercury-containing organic product was also formed, which de-composed on heating with liberationofmetallic mercury [probably owing to an admixture of a compound of the type (RHg)n ].

Electrolysis of CeH5CH2COCH3, CH3COCOCGH5, cyclopentanone,

Refcrenccs see page 288 285


cyclohexanone and 2-, 3- [3] and 4- [3, 4] methylcyclohexanones on a mercury cathode gave, respectively, (CeHsCHzCHCHs)2Hg, dicyclopentylmercury, dicyclohexylmercury and dimethylcyclo-hexy lmercury.

The electrolyses were carried out on ketones suspended in 5% H2SO4. The cathode was a mercury layer having a surface area of 15 cm2; a porous lead cylinder served as the anode. The duration of electrolysis varied from 4 to 8 hours for various ketones, the current was 2-4 A, and the temperature was 55-60°C (room temperature was also used in certain cases). Yields: 25-30%.

Benzyl methyl ketone is reduced with the formation of a mercury compound in 5% I^SO4 only at 55°C, and also in 30% H2SO4 or in a mixture of glacial acetic acid and 18% HCl. Cyclohexanone behaves in the same way. Cyclopentanone easily gives rise to the organo-mercury compound [3]. Ketones in which the carbonyl group is adjacent to a benzene ring are not reduced with the formation of organomercuries. It was impossible to obtain organomercury compounds under these conditions from menthone and dibenzyl ketone.

Dimenthylmercury has been prepared [5] from menthone in conc. H2SO4, using a mercury cathode, at 77-80°C.

Preparation of di-s-butylmercury [ l j . A 1-cm-deep layer of mercury is poured into a 11.5-cm-wide and 16-cm-tall glass beaker serving as a cathode compartment and placed in a bath at 40cC; a glass-covered copper lead ending in platinum is then immersed in the mercury. The anode compartment consisted of a porous porcelain vessel (external diam-eter 7 cm), suspended by means of a strong rubber ring and paraffinized wooden lid in the beaker in such a way that its bottom is 2-2.5 cm away from the surface of the mercury. The anode itself is a hollow lead cylinder, through which water is circulated and which is f ree ly suspended inside the porcelain vessel by a paraffinized wooden handle. The anode electrolyte is 20% H2SO4. The cathode compartment is charged with 30 g of methyl ethyl ketone and 300 ml of 30% H2SO4. The voltage on the terminals is 7.8-8.4 V at a current of 25 A and 45-50°C (the optimum temperature for this process). Amber drops of dialkyl-mercury appear within a few minutes of switching on the current and after 2 hours the amount of the oily product reaches 41.5 g. The material is separated off, f i l tered, dried over sodium sulfate and distilled on a water bath (the temperature of which does not exceed 80°C) under a pressure of 0.12-0.32 mm. The main fraction, distilling over at 46°C, is pure di-s-butylmercury; b.p. 91-93°C/15 mm. The remaining yellow oil (some-times comprising up to 30% of the crude product) decomposes violently at 90°C with liberation of metall ic mercury and cannot be distilled even under high vacuum.

Preparation of di-isopropylmercury [2]. Electrolysis of a 40% solution of sulfuric acid containing 0.125 mole of acetone for 30 A-hours on a mercury cathode, with a cur-rent density of 2.8-5.5 A/cm2, gives di-isopropylmercury and isopropanol.

Diethylmercury has been made in 81% yield by the electrolysis of NaB(C2H5)4 with mercury electrodes; triethylboron formed at the same time [6],

Preparation of diethylmercury by the electrolysis of NaB(C2H5 )4 on a mercury anode [6] . The electrolysis is carried out in a cylindrical glass vessel having a capacity of about 400 ml, provided at the bottom with a tap for running off the reaction products. The r im of the vessel is ground flat so that it can be covered with a flat, 16-mm-thick alum-inum lid. Mercury, serving as the cathode, is poured into a wide glass beaker (having, f o r example, a capacity of 250 ml), which is stood within the larger vessel on three

PREPARATION BY ELECTROLYSIS 287

sealed-on legs. A 30-ml beaker is attached central ly to the bottom of the preceding beaker by means of a suitable adhesive and f i l l ed with mercury serving as the anode. The anode is connected to the current source by a rotating rod (insulated, because it is wetted by the e lec t ro ly te ) carry ing , in the space f i l l ed with e lectro lyte , a blade s t i r r e r made of insulating mater ia l or covered with insulation. The function of this s t i r r e r is to f r e e the mercury surface f r om the react ion products.

The two beakers are f i l l ed with mercury up to the br im. The i r r ims are made to be the same height, so that the f inal arrangement consists of an anode situated concentr i-cally within an annular cathode. The cathode lead is also insulated and passed through a hole in the lid. The latter is additionally provided with openings f o r the inlet and outlet of an inert gas, a thermometer and (in the center ) f o r the rotating rod carry ing the cur-rent to the anode.

Sodium tetraethylborate is dissolved in water care fu l ly de-aerated with nitrogen (or pre ferably argon), since one of the reaction products, in addition to diethylmercury and hydrocarbons, is triethylboron. The inert gas is not passed into the vesse l itself during e lectro lys is , but the vesse l is " fanned" wi th i tby means of a T -p i e c e . During e lec t ro lys is the vesse l is cooled with water or with a small portable venti lator; the temperature of the process is about 20°C. NaB(C2H5 )4 (31.6 g, 0.211 mole ) is subjected to e lec t ro lys is (13 A/dm 2 on the anode, 6.5 V) . Co lo r l e ss drops of d imethylmercury and tr iethylboron soon appear and col lect at the bottom. Passage of 14,450 A-seconds (0.150 f ) g ive 15.7 g (0.122 mole, 81%) of diethylmercury (b.p. 52°C/10 m m ) and 13.0 g (0.133 mole , 87%) of triethylboron (b.p. 94-95°C).

Preparations of dialkylmercuries by electrolysis of M[Al(Alk)j R] (M = Na, K) on a mercury anode have been reported [7],

Electrolysis OfMtAl(C2H5)3OR] on a mercury anode (with a copper cathode) gave [8] and 82% yield of diethylmercury.

The compound Hg(CH2CH2COCH3)2, isolated in the form of a semi-carbazone and 2,4-dinitropheny lhydrazone [9], forms in electrolytic reduction of methyl vinyl ketone on mercury electrodes, at a catho-dic potential of 1.05-1.30 V and pH<5.

As was f irst shown by Kraus [10] in 1913, compounds having the composition RHg are formed on the cathode in the electrolysis of salts RHgX where R = CH3 [10-13], C0H5 [10, 12], n-C3H7 [10, 12], Iso-C3H7 [11, 13], n-C4H9 [11, 13], S-C4H9 [14], n-C5Hu [14], iso-C5H11 [14], U-C6H13 [14], U-C7H15 [14], n-C8H17 [10], Cydo-C6H11

[14], CgH5 [10, 12] and also P-CH3C6H4 [14]; X = Cl [10, 12, 14], Br [13], I [6, 14], NO [11] in liquid ammonia. No such compounds could be prepared in the case of C6H5CH2HgCl and trans-ClCH= CHHgCl [12]. CH3Hg has been obtained by electrolysis of aqueous or alcoholic CH3HgCl [10].

These compounds are usually black powders distinguished by a high electrical conductivity, decomposing at room temperature into R>Hg and metallic mercury. Compounds with secondary alkyl groups are less stable than those with normal alkyls; many of them already begin to decompose at -50°C.

These substances are regarded as "organic metals" with de-localized f ree electrons. According to Coates [15], their structural cell is RHg + , in which the mercury is bonded covalently to the alkyl group. It is possible [14] that such a structure is stable within the limits of the temperature stability of these compounds; at higher temperatures the electrons are attracted to the mercury atom and all bonds between R and Hg in the crystal lattice become

References sec page 288


equal [1, 13]. This hypothesis is particularly supported by the loss of optical activity which occurs when optically active s-butylmercury bromide is electrolyzed in liquid ammonia and when the cycle

H g B r s

R0HgBr - » (RHg)n R2Hg + Hg RHgBr

(where R0 is the optically active radical) is carried through [14]. Electrolysis of the products of the addition of mercuric salts

to ethylene and carbon monoxide has already been described in Chapter 6 in connection with the determination of the structure of such adducts.

Bibliography

1. J. Tafel, Ber. dt. chem. Ges., 39, 3626 (1906). 2. C. Haggerty, Trans. Am.electrochem. Soc., 56, 5 (1929); Chem.

ZentBl., I, 338 (1930). 3. T. Arai, Bull. chem. Soc. Japan, 32, 184 (1959). 4. F. R. JensenandL. H. Gale, J. Am. chem. Soc., 82, 145 (1960). 5. C. Schall and W. Kirst, Z. Elektroehem., 29, 537 (1923). 6. K. Ziegler and O. W. Steudel, Justus Liebig's Annln. Chem.,

652, 1 (1962). 7. U.S.S.R. Pat. 132,136 (1960). 8. West German Pat. 1,127,900 (1962); Chem. Abstr, 57, 11,235

(1962). 9. L. Holleck and D. Marquarding, Naturwissenschaften, 49, 468

(1962). 10. C. A. Kraus, J. Am. chem. Soc., 35, 1732 (1913). 11. F. O. Rice and B. L. Evering, ibid., 56, 2105 (1934). 12. B. G. Gowenlockand J. Trotman, J. chem. Soc., 2114 (1957). 13. B. G. Gowenlock, P. Pritchard-Jones and D.W. Ovenall, ibid.,

535 (1958). 14. B. H. M. Billinge and B. G. Gowenlock, ibid., 1201 (1962). 15. G. E. Coates, Rev. chem. Soc., 4, 226 (1950).

CHAPTER 12

Methods of Synthesis of Fully Substituted Organomercury Compounds RHgR

a) Synthesis of RHgR through Organomagnesiums

Fully substituted asymmetric compounds RHgR' were f irst ob-tained in relatively pure form by Hilpert and Griittner [1] (cf. [2]) by the action of Grignard reagents on aryl(alkyl)mercury salts:

RMgX + R'HgX ^ R'HgR + MgX2

Benzylphenylmercury [1], benzylethylmercury [3], ethylphenyl-mercury [1] and benzyl-o-tolylmercury [1] have been obtained in this way. High temperatures must be avoided during the syntheses of these compounds, because some of them are unstable and even at room temperature (more readily on heating) tend to decompose into a mixture of two symmetric derivatives:

2RHgR' ^ R2Hg + R^Hg

According to Hilpert and Griittner, asymmetric compounds can be obtained from organomagnesiums in only one way; for example, C6H5CI^HgC6H5 can be made by the action of C6H5MgBr on C6H5CH2

HgBr but not by the action of C6H5CH2MgBron C6H5HgBr. However, Kharasch [4, 5] showed that both the reaction of RMgX with R'HgX and of R'MgX with RHgX can lead to RHgR' if an excess of the Grignard is avoided and the temperature is carefully controlled. Kharasch et al. used this method to obtain C6H5HgCH3, C6H5HgC6H11, C 6H 5HgC 4H r n , CHsHgCH2C6H5, C6H5HgC10H7, C2H5HgC10H7jCH3HgC4

H9-U, C6H5HgC6H4OCIfe-O, CH3HgC6H11, C2H5HgC6H11, C6H5Hg(CH3)3

C6H3-1,3,5, QH7HgC4H9-U j C6H5HgC6H4CH3-?, H-C4H9HgC5H11-Iso, CH3Hg(CH3)3C6H2 -1,3,5 [4], C6H5HgC2H4Q3H5, C6H5CH2HgQH4C6H5, C6H5HgC4H3S [2], C2H5HgC7H15, C4H9HgC7H15, Iso-C4H9HgC4H9, iso-C3H7HgC3H7, C6H5HgC6H4Cl-P, C6H5HgC6H4Cl- 0, C6H5HgC6H4Cl- m, O-ClC6H4HgC6H4Cl-P, C6H5HgC6H4CH3-O, O-CH3C6H4HgC6H4CH3-?, 0 -CH3C6H4HgC6H4Cl-p, O-CH3C6H4HgC6H4CH3-P, O-CH3CsH4HgCe

H 4 C l - P , C6H5HgC6H4CH3-P, C6H5HgC6H4CH3-m, W-CH3C6H4HgC6

H4CH3-P1 TO-ClC6H4HgC6H4Cl- 0, M-CH3C6H4HgC6H4Cl-P, O-CH3

References see page 299 289


C6H4HgC6H4OCH3-O, CH3HgC6H4Cl- to, P-CH3OC6H1HgCgH4OCH3-a-C10H7HgC6H4OCH3-?, a-C10H7HgC6H4OCH3-O [5], C6H5HgC6

H4F-m, C6H5HgC6H4F- p, C6H5HgC6H4Br-O, C6H5HgC6H4Br- m, C6H5HgC6H4Br-?, C6H5HgC6H4CF3- to, W-ClC6H4HgC6H4C F3-m, C6H5

CH2HgCH2C6H4Cl-O, C6H5CH2HgCH2C6H4Cl- m, C6H5CH2HgCH2CgH4

Cl-p , TO-ClC6H4CH2HgCH2C6H4Cl-O, P-ClC6H1CH2HgCH2C6H4Cl-O, [6], C6H5CH2HgC4H9-I, C6H5CH2HgC3H5, C6H5HgC3H5 [7], C6H5HgC6

H3Cl2-2,4, o-ClC6H4HgC6H3Cl2-2,4, TO-ClCgH4HgCgH3Cl2^,4, CgH5

CH2HgC6H3Cl2-2,4, C6H5HgC3H3Cl2-2,5, TO-ClC6H4HgC6H3Cl2-2,5, CH3HgC6H3Cl2-2,5, TO-ClC6H4HgCH2C6H5 [8], CH2=CHHgR(R = C2H5, CeH5) [77],

An analogous method was used to obtain (CH3)3 SiCH2HgR (R = CH3, C6H13, C6H5) [9], P-CH2=CHC6H4HgC6H5 [10,11], C4H9Hg(CH2)5HgC4H9

( from 1 mole of BrHg(CH2)5HgBr and 2 moles of C4H9MgBr [12]), ( - )s-butyl ( i ) -s-butylmercury [13], C4H9HgC6H4OCH3-O [14] and CH2=CHCH2HgC2H5 [15] ( from CH2=CHCH2MgBr and C2H5HgBr). C3H5HgBr and C2H5MgI do not give RHgR' but give Hg, (C2H5)2Hg and C2H5HgI; also, C3H5HgBr and (C2H5)2Zn give (C2H5)^Hg, diallyl-mereury and metallic mercury [15],

Di(methylmercuri)benzene and di-(l,4-methylmercuri)durene were obtained [16] from di-l,4-chloromercuribenzene and 1,4-dichloromercuridurene respectively and CH3MgX (X = I or Cl). The preparation of cis-2-methoxycyclohexylneophylmercury from cis -2-methoxycyclohexylmercury chloride and 2-methyl-2-phenyl-propylmagnesium chloride has been described [17].

Nesmeyanov et al. [18] obtained CeH5CH2HgC6H11, C2H5HgC4Hg-n, a-C10H7HgC6H2(CH3)3, U-C4H9HgCH jC6H5, C6H5HgCH2C6H5 and n-C4H9HgC6H11.

Cis, trans-dipropenylmercury has been synthesized from cis-propenylmercury bromide and trans -propenyl-lithium [19], Koton et al. have synthesized p-styrylphenylmercury [20]. Compounds CF2=CH-HgR (where R was CH2=CH, C2H5, and C6H5) have also been made [21].

p-bis-(Phenylmercuri)benzene has been obtained in 16% yield f rom p-bis-(bromomagnesio)benzene and phenylmercury bromide (10 hours of stirring in ether) [22].

Preparation of ethylbutylmereury [ l 8 ] . Finely powdered butylmercury bromide (16.88 g, 0.05 mole ) is added at 2-10°C, in small portions and with vigorous stirring, to a solution of Grignard reagent prepared from 10.9 g(0.1 mole) of ethyl bromide and 2.4 g (0.1 mole ) of magnesium in 45 ml of dry ether. After 2 hours the reaction mass is de-composed with 100 ml of 1% H2SO4 at 5°C. The ethereal layer is dried over CaCl2 and the solvent removed on a water pump. The residue (13 g, 90%) is a mobile I iquidjnJ1 '5

1.5114.

Preparation of benzyIphenylmercury [ ] ] . Finely ground dry benzylmercury chloride (10.5 g ) is added in small portions, with stirring, to 32 g of phenylmagnesium bromide (4 moles) in absolute ether. Dissolution takes place with moderate boiling of the ether. After having been set aside for 30 minutes (longer periods, and especially boiling, should be avoided) the reaction mass is decomposed with \% H2SO4 and the ether separated, dried and evaporated in vacuum at 40°C. The remaining pale-yellow oil is shaken in a

SYNTHESIS OF FULLY SUBSTITUTED RHgRy 291

separating funnel with 5 volumes of cold absolute alcohol and then poured, with st irr ing, into 200 ml of boil ing absolute alcohol, the solution is immediately f i l t e red and the oil again separated by strong cooling. This operation is repeated twice more , and the oil, which is still slightly colored, then dried at 35°C in a desiccator over P 2 O 5 to constant weight [1] (see also [18]).

Phenylmercury bromide has been obtained [23], in addition to phenyltrichloromethylmercury, by the interaction of trichloro-methylmercury bromide with C6H5MgBr.

Asymmetric AlkHgCsCH (Alk = CH3, C2H5, n-C3H?, and t-C4H9) have been made by the reaction of alkylmercury halides with ethynylmagnesium bromide [24].

Synthesis of ethyIethynylmereury [24]. The synthesis is carr ied out under a current of dry nitrogen. A solution of 8.75 g (0.0247 mo l e ) of ethylmercury iodide in 50 ml of tetrahydrofuran is added, drop by drop, over 50 minutes, to an i ce -coo led solution of ethynylmagnesium bromide [25] ( f reshly prepared f rom 2.07 g, 0.086 g-atom, of mag-nesium) in 125 ml of tetrahydrofuran. The mixture is s t i r red with a magnetic s t i r r e r during this addition and then f o r an additional 17 hours at room temperature. It is next cooled to + 5 °C and subjected to a slow addition of a mixture of 450 ml of 6.6% aqueous ammonium nitrate and 190 ml of ether, with st i rr ing and cooling in ice . The lower, aqueous, layer is separated off and extracted with two 100-ml portions of ether. The combined ethereal extracts are washed and dried over anhydrous magnesium sulfate. Evaporation of the solvent in vacuum gives 5.37 g of a yel low crystal l ine product with a character ist ic unpleasant odor. Sublimation of the substance at room temperature under a pressure of 1 mm results in 4.6 g (73.4% y ie ld ) of white crysta l l ine sublimate; m.p. 71-72°C.

An analogous method was used to prepare the other AlkHgCsCH. CH3HgC= CH melts at 117-118°C. The higher members of this series are involatile liquids.

Preparation of p-tolylphenylmercury [4]. Finely ground p - t o l y lmercury chloride (1 mo l e ) is added in small portions to 2 mo les of phenylmagnesium bromide in absolute ether, with continuous st irr ing, maintaining the temperature at about 5°C to avoid de-composition of the product into two symmetr ica l molecules. (Such a decomposition is almost quantitative after 30 minutes at the boiling temperature of the ether . )

The mixture is next shaken f o r 30 minutes, or until all to ly lmercury chloride passes into solution and the excess of the Grignard reagent decomposes with 0.1% H 2SO 4 , im-mers ing the f lask in ice to keep the temperature below 10°C. The asymmetr ic organo-mercury compound is extracted with ether, the extracts dr ied over anhydrous Na2SO4

and the ether evaporated under vacuum in the absence of moisture. The product is careful ly washed with 5 portions of alcohol (to remove HgCl2 and the symmetr ic or -ganomercur ies ) and again dried under vacuum. The compound decomposes at approxi-mately 120°C.

Synthesis of perfluorovinylvinylmercury CF j =CFHgCH=CH 2 [ 2 l ] . An ethereal solu-tion of perf luorovinylmagnesium iodide or perf luorovinylmagnesium bromide in tetra-hydrofuran (0.1 g RMgBr in 100 ml of the solvent) is treated with an equimolecular solution of v iny lmercury bromide in the same solvent, at - 10°C, with vigorous shaking. At the end of this addition the mixture is s t i r red at 0°C f o r 12 hours. T h e solvent is then disti l led off under vacuum and the residue fractionated. The boil ing-point of per-f luorov inylv inylmercury is 45°C/2 mm; nD" 1.5220; rf/3 2.9510. Yie ld: 35%.

The same method was used to prepare perfluorovinylethylmercury (yield: 30°C; b.p. 53°C/l2 mm, nj4 1.4711, d f 2.7805).



b) Synthesis of RHgR' by Decarboxylation of RCOOHgR'

Kharasch proposed that his method of synthesizing organomer-curies by the decarboxylation of the mercury salts of carboxylic acids (Chapter 9) can also be extended to the preparation of asym-metric RHgR' [26]. When organomercury salts of carboxylic acids, obtained by the action of aryl(alkyl)mercury chloride on silver salts of carboxylic acids, are heated in high vacuum, carbon di-oxide is liberated and an asymmetric mercury compound is formed:

RCOOAg + ClHgR' AgCl + RCOOHgR' CO2 + RHgR' The salts RCOOHgR' can also be made by the action of the

corresponding RCOOH on R'HgOH [27]. The method is applicable to carboxylic acids in which the carbon dioxide is easily split off, especially when R is a radical with strongly negative substituents. Asymmetric compounds of this type are stable and show no tendency toward transforming into a mixture of two symmetric compounds.

Preparation of phenyl-2,4,6-trinitrophenylmercury [26]. Phenylmercury chloride (2.4 g) is added, with shaking, to a suspension of 3 g of s i lver trinitrobenzoate in 30 ml of benzene. A dense white precipitate separates out. The mixture is shaken for 30 min-utes, 20 ml of benzene added and the material extracted for several hours in an extrac-tor. The extract is then cooled and the mercury salt f i l tered off and dried under vacuum over H2SO4 ; yield: 3.1 g; m.p. 228°C.

A flask containing 2 g of phenylmercury trinitrobenzoate is connected to a high-vacuum pump and heated on a bath to 222°C. After 5 minutes at this temperature the contents darken and contract. The material is maintained f o r a further 5 minutes at 226°C and the temperature then raised to 228°C. As soon as the substance begins to melt, the bath is removed and the pump disconnected. The grayish product is washed on the f i l ter with 15-20 ml of ether. Yield: 1.73 g. The melting-point is 227.5°C after recrystall ization from benzene and washing with ether.

Analogous procedures were used to obtain p-tolyl-2,4,6-trinitro-phenylmercury [26, 27] and ethyl-2,4,6-trinitrophenylmercury [27]. According to Logan [27a] the synthesis of CCl3HgC6H5 by the inter-action of CCl3COONa with C6H5HgCl consists in the decarboxylation of CCl3COOHgC6H5, which forms as an intermediate, and not in the introduction of dihalogenocarbene into the Hg-C linkage.

c)|Synthesis of RHgAr' by the Arylation of RHgOH with Aromatic Compounds of

Tin, Antimony(III ) and Boron

A synthesis of RHgR' proposed by Nesmeyanov et al. [28] and consisting in the arylation of organomercury hydroxides in alkaline media with aromatic compounds of Sn, Sb(III) and B

2RHgOH + R2SnO 2RHgR' + H2SnO3

RHgOH 4- R'B(OH)2 RHgR' 4- H3BO3

2RHgOH 4- 2R'SbO 2RHgR' + Sb2O3 + H2O


has none of the disadvantages associated with the synthesis via Grignards (impossibility of preparing compounds with reactive substituents) or by the decarboxylation of organomercury carb-oxylates (limitation to the easily decarboxylating acids).

The asymmetric mercury compound crystallizes out when boiling solutions (or suspensions) of the two reagents in aqueous-alcoholic alkali are mixed, heated briefly to a temperature not exceeding 80°C and cooled. If the product is liquid, it is extracted from the reaction mixture with ether. If necessary, the reaction can be conducted at room temperature.

Synthesis of p-nitrophenylphenylmercury [28] . Abo i l i ng solution of 1.9 g(0.005 mo l e ) of p-ni trophenyimercury chloride in 120 ml of alcohol is mixed with 5 ml of 20% aqueous NaOH and with a solution of 1 g (0.003 mo le ) of diphenyltin dichloride in 20 ml of alcohol. T h e mixture is f i l t e red hot and the f i l t ra te diluted with 100 ml of water . The resulting suspension is left to se t t l e f o r 15-20minutes and then f i l t e red . The precipitate of p -n i t ro -phenylphenylmercury weighs 2.1 g (yield: 100%). A f t e r two r e c r y s t a l l i z a t i ons f r om benzene, the melt ing-point is 144-145°C (with decomposition).

Synthesis of methylphenylmercury [28]. Boil ing solutions of 3.4 g (0.01 mo l e ) of methyl-mercury Iodide in alcohol and 1.2 g (0.01 mole ) of phenylboronic acid in 20 ml of alcohol +5 ml of 20% NaOH are poured together and the mixture diluted with two volumes of water and extracted with ether. The ethereal layer is washed with 25% NaOH, then with water, and f inally dr ied over CaCl 2 . Evaporation of the ether y ie lds 1.85 g (81%) of the des ired product.

An 80% yield of p-chlorophenylphenylmercury was obtained in the same way from p-chlorophenylmercury chloride and phenyl-boronic acid [29],

Synthesis of p-ehlorophenylbenzylmercury [28] . A solution of 2 g (0.08 mo le ) of p-chlorophenylst i lbine oxide in 200 ml of boiling alcohol, 5 ml of 20% NaOH and a boiling alcoholic solution of 2.6 g (0.08 mo l e ) of benzylmercury chloride are mixed and f i l t e red hot. The f i l t rate is diluted with an equal volume of water. T w o hours later the precipitate is f i l t e red off and dried. The y ie ld is 56%. A f ter two recrysta l l i zat ions f r o m l igroine, the melting-point is 104-108°C.

The products of the addition of mercuric salts to the double bonds in unsaturated compounds can also be arylated in alkaline media with the aromatic compounds of tin, givingthe corresponding asymmetric organomercuries [30]:

2HOCH2CH2HgX +Ar2SnX2+4Na0H^2H0CH2CH2HgAr+H,Sn03 + 4NaX + H2O

(see also the first section of Chapter 6).

Synthesis of <3-hydroxyethy 1-p-toly lmercury [30] . A hot solution of 3.02 g (0.007 mo le ) of d i -p - to ly l t in dichloride in 10 ml of ethanol is poured into a boil ing solution of 3.25 g (0.01 mo le ) of /3-hydroxyethylmercury bromide in a mixture of 70 ml of alcohol and 5 ml of 20% KOH. The mixture is boiled f o r 3 minutes on a water bath, diluted with 150 ml of cold water and extracted with ether. The ethereal layer is washed with water, dr ied over sodium sulfate and f r e ed f r om the ether under vacuum. The y ie ld of Q-hydroxyethy i -p- to ly lmercury is 1.85 g (55%). T w o recrysta l l i zat ions f r o m petroleum ether g ive co lo r l ess crysta ls ; m.p. 52.5-53.5 C.



The interaction of trichloromethylmercury bromide with diphenyl-tin dichloride can proceed in various directions, depending on the amount of alkali used in the reaction [23]. Phenyltrichloromethyl-mercury was obtained in 49% yield by the reaction

2CCl3HgBr + (C6H5)2SnCl2 + 6NaOH 2CCl3HgC6H5 + Na2SnO3

+ 2NaCl + 2NaBr + 3H20

when the reagents were taken in stoicheiometric proportions. In the presence of a greater amount of alkali, the reaction gives a 29% yield of diphenylmercury. Considerable amounts of infusible and insoluble mercury-containing precipitates are also formed in both cases.

Synthesis of phenyl-o-hydroxycyclohexylmercury [30], Hot solutions of 1.8 g (0.005 mole ) of o-hydroxycyclohexylmercury acetate in 40 ml of ethanol, 0.9 g (0.025 mole) of diphenyltin dichloride in 10 ml of alcohol and 5 ml of 25% aqueous NaOH are poured together and heated for 3 minutes on a water bath. The precipitate obtained on dilution with water (1.6 g, 85%) is recrystal l ized twice from petroleum ether; m.p. 101-102°C.

The action of phenylboronic acid in boiling aqueous-alcoholic alkali on CHCl2HgCl leads to the formation of C6H5HgCHCl2 [39a],

d) Synthesis of RHgR by the Action of Diazomethane on RHgCl

The action of diazomethane on RHgCl (R = C6H5lCH3C6H4lC6H5CH2) [31], on CCl3HgBr [32] and on ArHgO2CR [33, 34] for example

RHgCl + CH2N2 RHgCH2Cl 4- N2

is a special case of the preparation of asymmetric organomercury compounds.

Of the resulting asymmetric organomercuries, only chloro-methylbenzylmercury, CCl3HgCH2Br and ArHgCH2OCORarestable; those remaining decompose immediately into a mixture of dichloro-methylmercury and diarylmercury.

Preparation of benzylchloromethylmercury [ 3 l ] . A solution of 1.05 g (5% excess) of diazomethane in ether is added, with vigorous stirring, to a suspension of 8.18 g of benzylmercury chloride in 200 ml of ether cooled to 0°C. The reaction proceeds slowly, with evolution of nitrogen, which continues until 1 equivalent of diazomethane has been added; all suspended material then passes into solution. Evaporation of ether and of the excess of diazomethane in dry air results in a noncrystallizing oil of C e H s C ^ H g C H 2 C l , which is dried to constant weight in a vacuum desiccator over paraffin and P 2 O 5 .

The asymmetric compounds of this type HOCH2CH2HgCH2X, obtained from hydroxyethylmercury salts, are extremely unstable and exist only at very low temperatures [35].

SYNTHESIS OF FULLY SUBSTITUTED RHgR' 295

e) Synthesis of RHgR with the Aid of Dihalogenocarbenes

Dihalogenocarbenes (diehloroearbene, obtained by the decomposi-tion of CCl3COONa [36, cf. 27a] or ethyl trichloroaeetate [37], or diehloro- [38] or dibromo- [38] carbenes made by the action of potassium t-butoxide on the corresponding haloform) can be intro-duced into Hg-Hal bonds with the formation of trichloromethyl-mercury compounds, including the asymmetric ones (Razuvaev et al. [36], Reutov and Lovtsova [38, 39a]):

= C C l ClHgCI -CCl3HgCI

=cci, AiHgCI- • ArHgCCI3

The latter reaction is carried out in benzene at room temperature [38-39a], In the same way, ArHgCHHal2 have been made by using CH2Hal2 in place of the CHHal3 in the reaction with potassium t-butoxide and ArHgHal [39a]:

ArHgHal C " H a ' . ArHgCHHal2

According to Seyferth [40], in the reaction using potassium t-butoxide and haloform the CCl^" anion simply displaces the halide ion:

ArHgBr + C O " ArHgCCl3 + Br~

Preparation of phenyltrichloromethylmercury [38] . A suspension of 4.9 g (0.016 mole ) of phenylmercury chloride in 100 ml of absolute benzene is treated with 5 g (0.062 mo le ) of absolute ch loro form. I -C 4 HgOK prepared f r om 1.2 g (0.03 g -a tom) of potassium is gradually added, with st irr ing and cooling by ice-water . A f ter 30 minutes of st irr ing, the blackened reaction mixture is poured into water and the precipitate f i l t e red off and washed with benzene. Evaporation of the benzene g ives 1.7 g of C e H j H g C C l 3 ; m.p. 114°C ( f rom alcohol). The precipitate not dissolving in benzene is extracted with hot acetone, evaporation of which results in 2.32 g of a mixture of phenylmercury chloride and phenyltr ichloromethylmercury. Treatment of this mixture with cold benzene g ives 1.55 g of CeH 5 HgCCl 3 , melting at 112-114°C. The residue contains 0.55 g of unreacted phenylmercury chloride; m.p. 256°C. The ove r -a l l y ie ld of phenyltr ichloromethylmer-cury is 3.25 g (52%).

Diehloroearbene can also enter one C-Hgbond in some symmetric organomercuries in which the mercury is linked with a secondary carbon. On heating, these compounds decompose not into a mixture of two symmetric R2Hg but into an organomercury salt and an un-saturated compound. The introduction of CHHal into the HgX bonds of organomercury compounds has been carried out by the scheme [76]:

RHgX + CH2X2 + (CH3)3COK - RHgCHX2 + KX + (CH3)3COH

in absolute benzene, with cooling by ice-water.

r? fences see pa 99


f ) Synthesis of RHgR' by "Cosymmetrization" of RHgX and R'HgX

Asymmetric compounds RHgR' are also obtained by "cosymmet-rization" of RHgX and R'HgX, where R^R ' , accomplished by the action of ammonia in chloroform and other organic solvents. Thus, "cosymmetrizations" have been carried out on P-XC6H4CH(HgBr) COOC2H5 with p-X'C6H4CH(HgBr)COOC2H5 [41, 42] and on a -bromomercuriarylacetic esters with benzyl mercury bromide [43].

The mechanism of this reaction is described at the beginning of Chapter 13.

g) Synthesis of RHgR' by the Action of RHgX (and R 2 Hg) on Compounds Containing Mobile Hydrogen

Organomercury bases RHgOH can mercurate compounds con-taining mobile hydrogen: acetylene [44], phenylacetylene [45], fluorene [45], cyclopentadiene [45], indene [45], triphenylmethane [45], propionic [45], malonic [45] and cyanoacetic [45] acids, and also trichloroethylene [45] and superaromatic heterocycles such as thiophene [46], as well as, unexpectedly, acridine [46], 2,6-dimethylpyridine [46] and quinaldine [46], giving asymmetric com-pounds according to the scheme

RH + R'HgOH -» RHgR' + H2O

(cf. second section of Chapter 5).

Synthesis of perchlorovinvlcyclohexvlmercury [45]. A solution of 30 g of cyclohexyl-mercury hydroxide in 200 ml of benzene is treated with 15 g of trichloroethylene. Separa-tion of the solvent gives a crystall ine residue; m.p. 44°C.

Synthesis of 2,4-diphenylthienylphenylmercury [46].

C6H5

AJn C6H3Hg S C6H5

A product melting at 114°C precipitates out when alcoholic solutions of 11.96 g of phenylmercury hydroxide and 4.72 g of 2,4-diphenylthiophene are mixed.

Unstable asymmetric products of the addition of aromatic organo-mercury bases to unsaturated compounds, e.g.

OR

ArHgOH +CH2=CHOR ^ ^ ArHgCH2CH^ NVOCH3


decompose immediately into a mixture of two symmetric organo-mercuries [47] (see Chapter 13).

Arylmercury hydroxides will also mercurate j3-dicarbonyl com-pounds, with the formation of mono- and dimercurated C-derivatives. The latter are generally unstable and readily undergo symmetriza-tion [48]. A diarylmercuri derivative of dibenzoylmethane has been obtained [48]. Stable products result from the mercuration of /3-disulfonyl compounds with arylmercury hydroxides [48],

Arylmercury hydroxides [48] and acetates [49] react with phenols under mild conditions (in alcoholic solutions, at room temperature or with gentle warming), giving Hg-O derivatives incapable of conversion into mercurated phenols.

The Hg-O product of the interaction between divinylmercury and phenol decomposes easily with liberation of metallic mercury and formation of vinyl phenyl ether [49]. Hg-O derivatives are also formed from diarylmercuries [50] with pentachlorophenol, from phenylmercury acetate with polychlorophenols [51], and from phenylmercury hydroxide and acetate with polyhydrophenols [52],

According to Koton et al. phenylmercury hydroxide [53] and acetate [54], symmetric (AlK)2Hg, where AlK = CH3 [55] C2H5 [56], H-C5H11 [57], and Ar2Hg, where Ar = C6H5 [54, 58, 59], o- [60] and V- [60] CH3C6H4, P-CH3OC6H4 [59, 61, 62], O-HOC6H4 [62], o- [62, 63], m- [62, 63] and p- [59] NO2C6H4, G-C10H7 [58], P-NH2C6H4 [59, 62, 64], and also asymmetric RHgR' [65] (CH3HgC6H5, CH3HgC10H7-a, C6H5HgC10H7-Q) mercurate phenols to give asymmetric organo-mercuries. The authors believe that mono-, di- and trimercurated products are formed, depending on the substituents present in the phenol. The reactions were conducted at 130-140°C in sealed tubes, in the absence of solvent (in individual cases in alcohol, and in the case of the diarylmercuries also in boiling xylene), for periods of several hours.

Heating R2Hg and RHgX (including RHgHal [66]) with polyphenols and with a- and /3-naphthols under these conditions leads to a destruction of the organomercury compound with separation of metallic mercury and (in most ArHgHal) of Hg2Hal2. Dibenzyl-mercury [67] reacts with all phenols in this way, with separation of Hg.

According to the same authors, dibenzylmercury mercurates (after 3 hours at 150°C) salieylaldehyde and also acetophenone, benzalacetone and benzalacetophenone, with the formation of monomercurated products [68],

Under the same conditions, di-p-toIylmercury mercurates acet-aldehyde, propionaldehyde, butyraldehyde, benzaldehyde and 0 -and m-hydroxybenzaldehydes [69]. Acrolein gives a dimercurated product (a monomercurated product at 180° C) and paraldehyde (120-150°C) gives r ise to di-p-tolylmercuricrotonaldehyde; in the presence of water (3 hours at 150°C),the products are metallic mercury and p-tolylmercuricrotonaldehyde. Di-p-aminophenyl-



mercury has been reacted in this way with propionaldehyde, butyraldehyde, acrolein, benzaldehyde and salicylaldehyde with the formation of p-aminophenylmercurialkyl(aryl)aldehyde [69],

In the light of the work carried out by Nesmeyanov and Kravtsov [48], who showed the products obtained by the interactions of ArHgOH with phenols, nitrosophenols, etc., to beArHgOcompounds (see above, and also Chapter 14), the ArHgC structures of the pro-ducts obtained by Koton et al. from reactions of organomercuries with phenols should be regarded as doubtful.

In accordance with the high thermal stability of perfluorinated mercury compounds, the asymmetric compound CH3HgC6F5 is distinguished by unusual stability. It does not decompose on being heated to 200° C and is obtained by heating dimethylmercury with bis-(pentafluorophenyl)mercury [70].

Preparation of me thy lpentafluoropheny lmercury [70]. bis-(Pentafluorophenyl)mercury (0.5 g ) and an excess of dimethylmercury are heated to 60°C in an evacuated Carius tube. The solid dissolves immediately but crystal l izes out again on cooling. After 12 hours at 60°C and cooling, the precipitate no longer crystal l izes out and the tube is then opened and the excess of dimethylmercury distilled off under vacuum. The residue (m.p. 34°C) is methylpentafluorophenylmercury.

h) Synthesis of RHgR' by Rearrangement of Radicals in Organomercury Compounds

Asymmetric organomercuries have been obtained [71] by re-arrangements of the type:

R2Hg + R'HgX RHgX + RHgR'

Thus, derivatives RHgCO^CH3 have been prepared by the reaction of carbomethoxymercury chloride with R2Hg (R = C H5, JB-CH3OC6H4, n-C4H9, CO2CH3).

Synthesis of phenylcarbomethoxymercury [7 l ] . A solution of 10.5 g (0.03 mole) of di-phenylmercury in 100 ml of warm (55°C) benzene is added to a solution of carbomethoxy-mercury chloride (10 g, 0.033 mole) in 100 ml of warm benzene. A precipitate of phenyl-mercury chloride appears at once. The mixture is cooled, the precipitated C6HsHgCl f i l tered off and the f i ltrate evaporated to dryness under vacuum at a temperature below 50°C. Recrystall ization from ether (with cooling)gives 8 g (70% yield) of material melting at 68-69.5°C.

Carbomethoxy-p-methoxyphenylmercury (m.p. 89°C) and oily n-butylcarbomethoxymercury were prepared in the same manner; in the latter case the reaction is carried out in alcohol.

Calingaert et al. [72-74] has reported the formation of RHgR' during the reaction of R2Hg with R 2Hg or R 4Pb in the presence of a i c i 3 which acts as a catalyst.

Radical exchange between R3Bi and R'2Hg has been reported [75].


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CHAPTER 13

Symmetrization of Organomercury Compounds and the Reverse Reaction

Since most methods of synthesizing the organometallic compounds of mercury lead to derivatives RHgX, the symmetrization reaction (conversion of salts RHgX into fully substituted organomercuries R2Hg) is one of the most important reactions of organomercury derivatives. Schematically, the process may be visualized as an equilibrium between the organomercury salt and the symmetriza-tion products:

2RHgX ^ R2Hg + HgX2

For the reaction to proceed to completion in the direction of the formation of the R2Hg, the mercuric ion must be removed in the form of an insoluble salt, e.g. HgS, HgFe(CO)4, a complex (for example, K2HgI4) or metallic mercury, so that the above equi-librium is displaced to the right. Symmetrization thus requires a reducing agent such as various metals (Na, Na and other amal-gams, Cu, Zn), alkaline sodium stannite, or hydrazine and its derivatives, or a complex-former such as KI, NaI, KCN, KCNS, Na2S2O3, or NH3 (in certain cases K2S, NaOH and triphenylphos-phine). The production of fully substituted organomercuries in the electrolysis of certain organomercury salts is also an example of reductive symmetrization. If the anion of the RHgX can form an insoluble compound with mercuric ions, the symmetrization can sometimes occur in the absence of other symmetrizing agents; this takes place when organomercury sulfides and thiosulfates are subjected to moderate heating, for example:

(RHg)2S -s- R 2 H g + HgS

The disproportionation of asymmetric organomercury compounds to a mixture of two symmetric products:

2RHgR' - » R2Hg + R2Hg

lies at the basis of symmetrizations by unsaturated compounds and certain organometallics (butyl-lithium); mentioned later in this

302

SYMMETRIZATION AND THE REVERSE REACTION 303

chapter. Some exceptional cases will be described in which the symmetrization proceeds in the absence of reducing or complexing agents.

Studies have now been carried out on the kinetics, stereochemistry and mechanisms of both symmetrization and desymmetrization of organomercury derivatives. Nesmeyanov, Reutov et al. found that the symmetrization of optically-active organomercuries, diastereo-mers of the Z-menthyl [1-4] and ethyl [4] esters of a-bromomercuri-phenylacetic acid in the presence of ammonia is a second-order, both with respect to RHgX and the NH3 [5], and proceeds with retention of the configuration at the asymmetric carbon atom involved in the reaction. On the basis of this, the above authors formulated a rule [1-3] that configuration is retained during bi-molecular electrophilic substitution at a saturated carbon atom (cf. the rule about the retention of configuration at an unsaturated carbon during electrophilic and homolytic substitutions, derived from the behavior of quasicomplex organomercury compounds; see Chapter 6).

The bimolecular rate constant of the symmetrization under the action of ammonia for C6H5CH(HgBr)COOR depends on the nature of R [6] and for P-XC6H4CH(HgBr)COOC2H5 on the nature of X [7]. The effects of the X groups satisfy Hammett's equation [8]. The rate of the symmetrization of P-XC6H4CH(HgBr)COOC2H5 increases if different molecules of these organomercury salts are reacted, in one half of which X is an electron-donor and in the other half an electron-acceptor, because this facilitates fission of the C-Hg and Hg-Br bonds in the transition state [9, 10].

It has been shown by using radioactive mercury that during such "cosymmetrizations" the C-Hg bond is broken in the molecule con-taining the electron-acceptor substituent. According to Reutov, this is in agreement with the proposed mechanism involving a four-center transition state, such as:

Benzylmercury bromide, which is not itself symmetrized with ammonia, enters into "Cosymmetrization" of this type with the ethyl esters of a-bromomercuriarylacetic acids. The C-Hg bond is broken in the four-center transition state in the molecule of benzylmercury bromide, as has been shown [1] by using benzyl-mercury bromide labeled with 203Hg.

The reaction opposite to symmetrization, when R^R', is given later.

Br

Hg

H g

x s C - C 6 H 4 C H

References see page 32'J


The stable diastereomers of 3-bromomercuri-i!-camphor and 3-bromomercuri-rf-camphor symmetrize in the presence of Na 2Sp 3

with a retention of the configuration [12], so that this reaction too is an electrophilic substitution. Ontheother hand, it has been shown on the examples of the symmetrizations of 2-methoxycyclohexyl-mercury iodide [13] and s-butylmercury bromide [14] under the action of sodium stannite that the symmetrizations proceeding by a radical mechanism take place with an inversion of the configura-tion. In the latter case both alkyl groups racemize.

However, it is obvious that no inversion of the configuration occurs if the mercury atom is rigidly fixed at the head of a bridge structure, as in the case of 4-chloromercuricamphane [15], even in the presence of a symmetrizing agent acting by a radical mechanism, such as sodium stannite.

The inversion occurring during the symmetrization of 3-bromo-mercuricamphor [16, 17] and of the adducts of mercuric salts to unsaturated compounds [19] under the action of hydrazine hydrate shows that the symmetrizations with the latter reagent are also homolytic [16, 17].

The stereoisomeric alkylmercury salts (cis- and trans-4-methylcyclohexylmercury bromides, L- (- ) -s-butylmercury bro-mide) symmetrize stereospecifically under the action of magnesium with 85-97% retention of the configuration [20]. A mechanism in-volving a mercurous organic compound has been proposed for this reaction [20],

The homolytic symmetrization occurring during electrolysis is accompanied by racemization [21].

Wright [22] showed that the reaction reverse to symmetrization also proceeds with retention of the configuration. This has been confirmed by Nesmeyanov and Reutov [23, 24], in partial correction of earl ier data [1-3].

Reutov et al. believe that the same kinetics and stereochemistry as the symmetrization (under the action OfNH3 [1-10], Na2S2O3 [12])

2R3CHgX (R3C)2Hg + HgX2 (1)

and the desymmetrization [23, 24]

(R3C)2Hg+ HgX2 - 2R3CHgX (2)

reactions are also shown by other electrophilic substitutions as a saturated carbon atom-isotope exchanges between organomercuries and compounds containing labeled mercury:

R3CHgX + 203HgX2 R3C203HgX + HgX2 [25-37] (3)

R3CHgX + R203HgX j i R3C203HgX + RHgX [38] (4)

(R3C)2Hg + R3C203HgX (R3C)2203Hg+ R3CHgX [39] (5 )

Reactions (3-5) are bimolecular and are of f irst order with respect


to each component; they occur with retention of configuration. On this basis, Reutov [40] proposed a common mechanism for these (Sg 2) reactions in nonpolar solvents or in solvents having only a low polarity, which he represented by the following scheme with the same transition state:

X I

X Y Hg X / \ \ /

R 3 C - H g + Hg R3C Y ^ R3CHg + Hg / \ I \

R' Hg R' Y I

R'

(reaction (1): R3C = R', Y = X = halogen; reaction (2): X = R3C, R' = Y = halogen; reaction (3): Y = X = halogen; reaction (4): R3C = X (see however [41]; for symmetrization with ammonia, see also [44]), R = Y = halogen; reaction (5): R3C = X = R', Y = halogen). In solvents exhibiting basic properties and during symmetrizations occurring under the action of ammonia, either one or both the mercury atoms are coordinated in the transition state to molecules of the base [40a-40e].

Analogous views are developed by Hughes, Ingold and others. Thus, Charman, Hughes and Ingold [43] confirmed the mechanism of the equilibrium symmetrization

2RHgX ^ R2Hg + HgX2

and the fact that the configuration is retained when the reaction proceeds in either direction, from their kinetic studies of the desymmetrizations of di-s-butylmercury with mercuric bromide, mercuric acetate and mercuric nitrate and with mercuric bromide in the presence of butyl-lithium.

The same Sg 2 mechanism was accepted by the above authors for the noncatalysed reactions (3) [45, 46] and (5) [47] on the basis of kinetic studies and the retention of stereochemical configuration at the carbon linked with the exchanging mercury atom (see Chapter 14).

The configuration is preserved in the reactions of di-s-butyl-mercury [14] and of (-)-s-butyl, (+)-s-butylmercury [14, 48] with mercuric bromide.

Second order and an 2 mechanism have also been confirmed for the desymmetrizations of various alkyl and aryl R2Hg with HgX2

(X = Cl, Br, I). Since the rate constants depend on the polarity of X and the polarity of the Hg-X bond, a mechanism with a four-center transition state involving the ion pair XHg + and X - has been pro-posed [49].

The dependence of the rate of the reaction

RHgR + Hg I 2 - » RHgI + R'Hgl



on the nature of R and R' and on the solvent is due to a change in the entropy of activation andthepolarizability of the C-Hg bond [42].

The isotope method has been used to study the desymmetrization

RHgR' + HgX2 RHgX + R'HgX

in the case of R^R' (see also Chapter 14). The relative bond strengths in RHgR' have been established from the distribution of 203Hg between RHgR' and R'HgBr in the reaction of RHgR' with 2 03HgBr2 [50, 51]. Nesmeyanov and Reutov found that, contrary to what had been reported by Dessy [42], it is the bond between the phenyl group and the mercury in phenylethylmercury that undergoes fission [51].

The interaction of czs-2-methoxycyclohexylneophylmercury with 203Hg-labeled mercuric chloride proceeds with retention of the configuration of the involved eyclohexane ring carbon [41]; the radiomercury is distributed statistically between the two radicals.

The proposition that a symmetric product may form as an inter-mediate in the reactions:

RHgX + Hg*Xj RHg*X + HgX2

RHgX+ H g * - R H g - X + Hg has not found experimental confirmation [29].

The action of the complex-forming symmetrizing agents KI, KCNS, Na2S2Q3, KCl, etc. on a-mercurated aldehydes, ketones and car-boxylic acid esters leads not to symmetrization but to hydrolysis of the Hg-C bond and formation of enolates, e.g. [52]

ClHgCH2CHO + 4NaI - Na2HgI1 + NaCl + CH2=CHONa

owing to the considerable a-n-conjugation in these compounds. No symmetrising agent is equally effective in all classes of

organomercury compounds; different reagents exert optimum effects in different fields.

One of the most universal methods is symmetrization with sodium stannite, which is widely applicable for saturated and unsaturated aliphatic, aliphatic-aromatic, alicyclic, aromatic and heterocyclic mercury derivatives. Almost universal action is also exerted by copper in the presence of ammonia or other nitrogen-containing bases, which is also used for the symmetrization of the adducts obtained from mercuric salts and unsaturated compounds and of a-mercurated oxo-compounds.

Recently, increasing use has been made of ammonia in inert solvents (benzene, chloroform, etc.). Ammonia is an excellent reagent, even in the absence of copper and is convenient for the symmetrization of a very wide range of compounds under very mild conditions. It also symmetrizes compounds with extremely labile C-Hg bonds, such as a-halogenomercurioxo- and a-halo-genomercuricarboxy-compounds, which in aqueous or alcoholic


solutions hydrolyze under the influence of most of the usual sym-metrizing agents (Kl, NaCN, Na2S2O3):

RHgX + AY + H2O RH + Hgl'4 + OH' - f X '

(see above and Chapter 6). This method is therefore particularly recommended.

Potassium iodide is widely used, especially for the symmetriza-tion of aromatic and heterocyclic organomercury salts, and for the mercury derivatives of the metallocenes. Like the other complex-formers (KCN, KCNS, Na2S2O3), it is unsuitable for the symmetriza-tion of quasicomplexcompounds. The limitationsofpotassium iodide are dealt with later in this chapter.

One of the most commonly used symmetrization agents is an aqueous solution of sodium thiosulfate. Its action is mild and it is applied in cases in which the mercury atom is labile; however, aqueous Na2S2O3 is inferior in this respect to ammonia in an inert solvent.

Sodium cyanide, sodium stannite and copper in the presence of nitrogen-containing bases are used for the simple aliphatic com-pounds of mercury. Symmetrization by electrolysis is particularly successful in these cases.

Cadmium amalgam has proved to be a specific reagent for the symmetrization of the lower perfluoroalkyl mercury derivatives. The latter do not give rise to symmetric products in the presence of other symmetrization agents, such as sodium, alkaline sodium stannite solution and KI or KCNinwateror acetone [78], The action of these reagents (except Na) on CF3HgI results in the formation of fluoroform [78].

Products of the addition of mercuric salts to the double bonds in acyclic alkenes do not symmetrize but decompose under the influ-ence of the complex-formers (KI, KCN, KCNS, Na2S2O3), with evolution of the olefin. This is of course a manifestation of the quasicomplex character of these adducts (see Chapter 6). The reducing symmetrization agents, for example sodium amalgam, replace the mercury by hydrogen in these compounds. An exception is the symmetrization of the adducts of mercuric salts and carbon monoxide, carried out in the presence of triphenylphosphine.

Another special case is the sodium-amalgam symmetrization of the adduct obtained from HgCl2 and allylphenol.

The products of the additionof mercuric salts to alicyclic alkenes are symmetrized by ammonia, hydrazine hydrate and sometimes other reagents. a-Halogenomercurioxo-compounds are symme-trized by ammonia in benzene or chloroform, and in one case by copper in the presence of pyridine. Quasicomplex products of the addition of mercuric salts to triple bonds liberate acetylene with all the complex-forming symmetrization agents, but are very easily symmetrized by ammonia in benzene or chloroform. The



product of the addition of mercuric acetate to diphenylacetylene symmetrizes under the influence of KI in acetone.

The extremely labile quasicomplexes made by the addition of HgCl2 to acetylenic alcohols, ketones, and acids are merely de-composed by all symmetrizing agents.

Other alkenyl organomercuries, exhibiting no quasicomplex properties, can in several cases be symmetrized by KI in acetone, KCN, sodium amalgam, sodium stannite, butyl-lithium and other reagents.

The symmetrization of aromatic and heterocyclic monomercury salts can be accomplished with various reagents, depending on the lability of the Hg-C bond.

Polymercurated compounds symmetrize under vigorous condi-tions, for example in the presence of copper in pyridine or sodium amalgam.

The ranges of application of the various symmetrizing agents will be described individually in the following sections. It should be remembered that specific symmetrizing agents so far used in isolated cases may prove to be applicable to a wider range of compounds.

a) Symmetrizations of Organomercury Compounds

Very few cases of symmetrization with metallic sodium have been reported. Di-/3-thienylmercury derivatives have been ob-tained by heating /3-thienylmercury chloride and its derivatives with sodium in xylene [53].

Cases of symmetrization of a-mercurated thiophenes by this method are also known [54], but these are more often symmetrized by milder agents, such as the alkali metal iodides, sometimes thiocyanates or sodium stannite.

Preparation of 2,3,2',5 ',-tetramethyl-3,3'-dithienylmercury [53].

Sodium (1.5 g) is added to a boiling solution of 5.6 g of 3-chloromercuri-2,5-thioxene in 30 ml of dry xylene and the mixture is refluxed for 30 minutes with vigorous shaking. The dark precipitate is f i l tered off and the brown f i l trate very strongly evaporated. Frac-tional crystallization of the resulting brownish precipitate f rom petroleum naphtha (b.p. 70-120°C) gives the starting material (m.p. 152-155°C) and the required product (m.p. 144- 145°C). Yie ld: 0.3-0.4 g.

S y m m e t r i z a t i o n b y t h e A c t i o n o f M e t a l s

S o d i u m , s o d i u m a m a l g a m a n d a t i n - s o d i u m a l l o y .

2RHgX + 2Na R2Hg + Hg + 2NaX,

2RHgX + Na2Hg - » R2Hg + 2NaX + 2Hg


The action of sodium dispersed in a mixture of benzene and nonane on chloromercuriferrocene gives diferrocenylmercury [55],

Sodium amalgam in an inert solvent or in alcohol has been used more widely, mainly for the symmetrization of the organomercury derivatives of the hydrocarbons. It has also been used for phenyl-mercury acetate and phenylmercury iodide [56], a-naphthylmer-cury iodide [57] and for dibromomercuripentamethylene, which gives a heterocyclic compound, cyclomercuripentamethylene [58, 59] (mercuracyclohexane)

CH2CH2

/ \ H2C Hg

\ / CH2CH2

Adams, Roman and Sperry [18] converted 1-chloromercurimethyl-1,2-dihydrobenzofuran into the corresponding symmetric compound by using sodium amalgam:

^Y-CH2 ( f \ — , , C H 2 \ „ I v I J x ^ H C H 2 H g C l \\Jk^jCHCHiJ

Preparation of bis-(l-methyl-l,2-dihydrobenzofuryl)mercury [ l 8 ] . A suspension of 15 g of 1-chloromercurimethyl-1,2-dihydrobenzofuran in IOOml of absolute alcohol is placed in a round-bottom f lask connected to a ref lux condenser. Amalgam (3%) containing 1.5 g of Na is slowly added through the condenser. T h e reaction is initiated by gentle heating. A f ter 20 minutes, when the amalgam has decomposed, the mixture is boiled f o r half an hour. At the end of this period the crysta ls of 1 -ch loromercur imethy l -1 ,2-d i -hydrobenzofuran disappear and a gray precipitate is f o rmed. Af ter cooling, the prec ip i -tate (2.5 g NaCl and organic impur i t ies ) is f i l t e red off and the f i l t rate evaporated. The resulting precipitate is recrys ta l l i z ed f r o m ether. The y ie ld of the pure mater ia l is 6 g; m.p. 93°C. A fur the r 1 g of impure product can be obtained f r o m the mother l iquor, equiva-lent to about 50% of the y ie ld of a puri f ied product.

In many cases the action of sodium amalgam (especially in water) results not in symmetrization of the organomercury but in replace-ment of the HgX group by hydrogen.

On interaction with an 85-15 Sn-Na alloy, cis-{3 hours of boiling in benzene) and trans- (3 hours of boiling in xylene) a-chloromer-curistilbenes do not give r ise to organotins but undergo symme-trization [60]. The yield of the trans - a-mercuri-bis-st i lbene was 77% and that of the c is- isomer amounted to 97%. When the reaction with the irons-isomer is carried out in benzene, the mixture must be boiled for 8 hours to achieve a 70% yield.

C o p p e r . Copper itself is not a particularly convenient symme-trizing agent since it requires prolonged heating with the solution of the organomercury salt. It has therefore been used only in a few cases (see for example [61-64]). On the other hand, the use of copper in the presence of organic [65, 66] or inorganic [66, 67] nitrogen-containing bases, NA, proposed by Hein and Wagler [65]:



2RHgX + 2Cu + NA - » R2Hg +2CuX • NA + Hg

is one of the most convenient and universal methods. This procedure has yielded excellent results with aliphatic [65] (the a-mercurated oxo-compound ethyl a-chloromercuriacetate gives a low yield of the symmetric product [68]) and alicyclic [69] organomercury derivatives, as well as with the following classes of aromatic com-pounds: mercurated hydrocarbons [67, 70] and their halogeno and nitro derivatives [65, 67, 71], phenols [72] and thiophenols [183], amines and their derivatives [65, 73], ketones [62], acids [74] and esters [74, 75]. The bases NA were ammonia, amines, pyridine and pyridine homologs.

Symmetrization in the absence of ammonia or pyridine is pre-ferred in those cases in which the base is not inert with respect to the symmetrizing substance; the yields are then higher (cf. the symmetrizations of chloromercuribenzoic esters).

Preparation of the methyl ester of mercuri-bis-acetic acid [68]. Copper (4 g ) is added to a solution of 6.2 g (0.02 mole ) of methyl chloromercuriacetate in 20 ml of absolute pyridine. Heat is evolved and the mixture assumes a green color. After 1 week the liquid is f i l tered off, the pyridine removed under vacuum and the residue extracted with two 5-ml portions of hot benzene. Some benzene is then evaporated off and an equal volume of hexane added. The resulting dark precipitate (mainly copper salts) is f i l tered off and the f i ltrate treated with ether till the appearance of turbidity. Cooling to -30°C results in the appearance of pale-green crystals, which are subsequently recrystal l ized from a mixture of benzene and ether. Yield: 0.8 g; m.p. 96-98°C. Repeated recrystall ization f rom a mixture of methanol and ether gives 0.5 g (14%) of the pure product; m.p. 99-100°C.

Preparation of diphenylmercury [65]. A solution of 0.5 g of phenylmercury bromide in 4 ml of pyridine, contained in a SchIenk tube f i l led with N 2 or CO2 , is treated with 0.8 g of finely cut pieces of copper wire. An intense yel low-green color appears within a few minutes and mercury is liberated, partly as an amalgam. No other visible changes take place after the mixture has been shaken for 1 week. The pyridine is evaporated off under vacuum at a temperature below 40°C and the residue washed f ree f rom inorganic mercury salts with cold aqueous ammonia. Recrystall izationfromalcohol yields material melting at 125°C.

Preparation of diphenylmercury [65]. Approximately 4 g of benzylmercury chloride treated with copper in pyridine by the procedure described above gives 7.5 g of the re-quired product; yield: 75%; m.p. I l l 0 C .

Preparation of di-p-chlorophenylmercury [65], p-Chlorophenylmercury chloride (5 g), 6.5 g of copper and 35 ml of pyridine under the above conditions give 2.5 g of the required product; yield: 81%; m.p. 242-243°C (from acetone).

Preparation of bis-o-nitrophenylmercury [65]. Copper wire (5.3 g) is added to 4.5 g of o-nitrophenylmercury chloride dissolved in 30 ml of pyridine and the mixture set aside for 1 day in a vessel f i l led with CO2 . The pyridine is removed under vacuum below 40°C and the residue wetted with alcohol and washed f ree f rom copper salts with aqueous ammonia. Yield: 2.3 g (92%). Recrystall ization from alcohol or acetone gives small, rather dark needles; m.p. 206-207°C.

Preparation of di-p-dimethylaminophenylmercury [65]. p-Dimethyiaminopheny.' cury c nloride (2 g), 10 ml of pyridine and 1 g of copper give, after the same treatment as in the nreceding experiments, 1.0 g (81%) of the required product; m.p. 167-168°C.


The same method was used to obtain di- a-naphthylmercury (m.p. 243°C) and di-p-bromophenylmercury (m.p. 245°C). Methyl-mercury and ethylmercury iodides have also been symmetrized in this way [65].

Preparation of the ethyl ester of mercuri-bis-p-benzoic acid by the action of copper in the absence of ammonia [64] . Ethyl p-ch loromercur ibenzoate (3.84 g, 0.01 mole ) is boiled f o r 10 hours with 3 g of copper in 150 ml of benzene. Y ie ld : 2.4 g (96%); m.p. 192°C. Recrysta l l i zat ion f r om alcohol.

Preparation of the methyl ester of mercuri-bis-p-benzoic acid by the action of copper in the presence of ammonia [74] . Methyl p-ch loromercur ibenzoate (6.6 g ) is mixed with 4 g of copper powder, 60 ml of acetone added and the whole mass careful ly st i rred. Then, 30 ml of 25% aqueous ammonia are added, with shaking, and the mixture shaken vigorously f o r 10 minutes and poured into an excess of water (300 ml ) . The precipitate is f i l t e red off, dr ied at 100°C and extracted with hot ethyl acetate. Y i e ld : 2.85 g (68%); m.p. 264-265°C ( f rom chloro form or acetone). F o r the less easi ly hydrolysed ethyl es ter the yield under these conditions is 88.5%.

Addition of copper powder and 25% ammonia during the prepara-tion of organomercuries by the decomposition of double salts of HgCl2 and aryldiazonium chlorides gives directly the corresponding diarylmercury; the arylmercury chloride need not be isolated (see Chapter 7).

Z i n c . Zinc has also been used occasionally as a symmetrizing agent. Thus, ethyl p-chloromercuribenzoate heated over a long period with zinc dust gives a 58% yield of di- p-carbethoxyphenyl-mercury [64],

Heating of y-mercurated alcohols containing secondary or tertiary alcohol groups with zinc dust leads to the separation of metallic mercury via the intermediate formation of the corre-sponding symmetric organomercuries [76].

Under the action of zinc dust in alkaline solution, ethyl a- (2-chloromercuriethyl)acetoacetate gives bis-y-acetopropylmercury [77],

M a g n e s i u m . Magnesium has been applied to the symmetrizations of cis- and trans-4-methylcyclohexylmercury bromides andL- ( - ) -s-butylmercury bromide [20]; the conditions were not reported.

C a d m i u m , c o p p e r a n d s i l v e r a m a l g a m s . These are specific for the perfluoroalkyl compounds of mercury [78].

Preparation of bis-(trifluoromethyl)mercury [78] . T r i f luoromethy lmercury iodide (2.0 g ) is heated with s i l ve r amalgam (10 g Ag, 25 ml Hg) in a sealed tube at 140°C in a rotating furnace f o r 20 hours. The excess of amalgam is then separated off and the solid precipitate extracted with ether. Evaporation of the ether yields a white solid which sublimes at 70 cC at atmospheric pressure; m.p. 163°C (sealed capi l lary ) . Y ie ld : 80%.



The yield of bis(trifluoromethyl)mercury was 80-90% with cadmium amalgam (10 hours at 120-130°C), 20% with copper amalgam (12 hours at 120°C) and 50-60% with copper amalgam in acetone.

S y m m e t r i z a t i o n b y t h e A c t i o n o f S o d i u m H y d r o s u l f i t e

A salt of o-nitrophenylmercury has been symmetrized in this way [78a].

S y m m e t r i z a t i o n b y t h e A c t i o n o f F e r r o u s H y d r o x i d e

This agent has been used, for example, for the symmetrization of mercurated nitrobenzoic acids with their simultaneous reduc-tion [184].

S y m m e t r i z a t i o n b y t h e A c t i o n o f S o d i u m S t a n n i t e

An excellent and widely used method of symmetrization is the use of an alkaline solution of sodium stannite:

2RHgX + Na2SnO2 + H2O RaHg + Hg + 2NaX + H2SnO3

This is applicable to various classes of both aromatic and ali-phatic organomercury compounds. It has been used for the organo-mercury derivatives of aliphatic hydrocarbons [14] (including olefinic hydrocarbons [13, 79, 181]); in particular, divinylmercury [80] and diallylmercury [81, 82] have been obtained in this way (however, KCN is better for the symmetrization of allylmercury iodide [83]). Sodium stannite has also been applied to the symme-trization of the salts of cis- and trans-stilbenylmercury [84], 3-alkanolmercury salts [85, 86], certain products of the addition of mercuric salts to unsaturated compounds, e.g. the product of the methoxymercuration of styrene [90a], terpene derivatives: cineole [87], camphane [88, 89] and camphor [90] (also with the HgCl at the head of the bridge [15]), organomercury derivatives of aliphatic-aromatic [91] and aromatic (see for example [91, 95]) hydrocarbons, phenolic ethers [94, 95], aromatic acids [96], heterocycles [97, 98], ferrocene [55], and so on.

In certain rare cases the action of alkaline Na2SnO2 on organo-mercury salts results not in symmetrization but in reduction. Thus, in the reaction of 0.5N Na2SnO2 with CF3CClFHgF, the latter does not symmetrize but the mercury is replaced by hydrogen [99].

Hydrocarbons containing two HalHg groups at the ends of the chain symmetrize to cyclic compounds in which the mercury


forms part of the ring. Thus, 1,6-dimercuracyclodecane was ob-tained from 1,4-dichloromercuributane [100] and O(CH2CH2HgBr)2

gives with alkaline sodium stannite a compound to which Sand ascribed [101] the structure of l-oxa-4-mercuracyclohexane but which X-rays showed [102] to be the dimer l,7-dioxa-4,10-dimer-curacyclodecane:

C H 2 C H 2 H g C H 2 C H 2

c / \ \ /

C H 2 C H 2 H g C H 2 C H 2

Preparation of l,7-dioxa-4,10-dimercuracyclododeeane ClOl] . Di (bromomercur ie thy l ) ether is d issolved in 10% KOH and f i l t e red alkaline Na2SnO2 is poured in till no more precipitation takes place. The precipitate is careful ly washed by decantation and dried over H2SO4 . The gray-v io le t mater ial (5 g ) is covered with benzene, sealed in a tube and heated f o r severa l hours at 140°C. The liquid above the l iberated mercury is f i l l ed with small , elongated, co lor l ess pr isms which are subsequently recrys ta l l i z ed f r om benzene or ch loro form; m.p. 145°C; y ie ld : 60%.

The product obtained by the action of sodium stannite on the trans [103] mercury derivative of dipropylene oxide [101] is poly-meric [103]:

X H g H 2 C

\ n / l

OH', SnO 2

l i ght

C H 2 H g X

— H , C

C H 2 H g -

P r e p a r a t i o n o f d i b e n z y i m e r c u r y [ 9 1 ] . Alkaline sodium stannite (prepared f r om 25 g of NaOH in 125 ml of water and 10 g of stannous chlor ide dihydrate in 125 ml of water ) is added to a suspension of 15 g of benzylmercury iodide in 10 ml of alcohol and 225 ml of water. The mixture is then s t i r red mechanically f o r 1 hour. The precipitate is f i l -tered off, washed with water, dr ied and extracted with acetone. The impurity of f inely divided mercury is removed by adding a l i tt le zinc dust and f i l tration. The f i l t ra te is treated with water to the appearance of turbidity and then cooled to -15°C . The resulting needle- l ike crysta ls of dibenzyimercury (64 g; 93.2%) have a melting-point of I i l 0 C .

Preparation of divinylmereury [80] . Alkaline sodium stannite, prepared f r om 4.02 g (0.017 mo le ) of SnCl 2 .2H 20 in 36 ml of water and 8.27 g of NaOH in 30 ml of water, is added to a solution of 10 g (0.0326 mo l e ) of v iny lmercury bromide in 120 ml of acetone. A f t e r 30 minutes a fract ion boil ing between 58 and 87°C is disti l led off (cooling the r e c e i v e r to -25 to -30°C) . Th is is treated with saturated aqueous sodium chlor ide. The separating oil Y ie ld : 53%.

is dr ied and dist i l led; b.p. 90-91°C/80 mm; nD20 1.5978; rf,20 2.7713.

Preparation of 10,10-mercuri-bis-eamphor [90] .

/

\A Hg

CH 2 / 2

iO-Chloromercuricamphor (1 g ) d issolved in hot acetone is poured into 150 ml of water



and the resulting suspension stirred for 2 hours with a solution prepared f rom 10 g of NaOH, 8 g of SnCl 2^H 2O and 200 ml of water. The precipitate is f i l tered off and extracted with boiling acetone. Careful dilution and cooling gives the required product in the form of crystals; m.p. 255-256°C.

Preparation of diphenylmercury from phenylmercury acetate [93]. Asolutionprepared f rom 125 ml of 40% NaOH and 50 g of SnCl2.2H20 in 25 ml of water is added to 30 g of phenylmercury acetate in 300 ml of water, with energetic mechanical stirring, and the stirring continued f o r an hour. The resulting gray-black precipitate is f i l tered off, washed with water and extracted with acetone. Zinc dust is added if finely divided mercury is seen to pass through the f i l ter . The f i l trate is treated with water to the appearance of slight permanent turbidity. The extraction can be carried out with benzene in place of acetone. The crystals appearing after cooling are f i l tered off and dried; yield: 13.2 g (95.6%); m.p. 125°C.

Preparation of diphenylmercury from phenylmercury chloride [97]. A solution of 6.2 g of phenylmercury chloride in 40 ml of pyridine is added to 2.5 g of stannous chlo-ride in 5 ml of water in an excess of 30% aqueous NaOH. After a few hours, the pyridine is distilled out and the precipitate f i l tered off and dried. Diphenylmercury is extracted with 95% alcohol. After recrystall ization from alcohol, the yield is 3.6 g (90%); m.p. 124-125°C.

Preparation of diferrocenylmercury [55]. A solution prepared from 5.0 g of NaOH in 25 ml of water and 1.8 g of SnCl2 .2H20 in 25 ml of water is added to a suspension of 2.1 g (0.005 mole) of ferrocenylmercury chloride in 20 ml of 95% ethanol and 50 ml of water. The yellowish-orange color disappears immediately and grayish-black material is precipitated. After stirring for 3 hours, the precipitate is f i l tered off, washed with water, dried and extracted with boiling xylene. Cooling gives 1.0 g (yield: 70%) of yel low-orange crystals of the desired product. Recrystallization from xylene; m.p. 234-235°C (with decomposition).

S y m m e t r i z a t i o n b y t h e A c t i o n o f H y d r a z i n e a n d R e l a t e d C o m p o u n d s

Hydrazine hydrate, hydrazine salts, phenylhydrazine (also in the presence of copper [105]), semicarbazide, and also hydroxylamine give good yields of diarylmercury compounds from organomercury derivatives of hydrocarbons. Diphenylmercury [104], di-p-tolyl-mercury [104], di-p-chlorophenylmercury [106], earo-3-chloro-mercurinorcamphor, dipentafluorophenylmercury [106b] and di-et-furylmercury [104] have been obtained in this way. The method was also applied in the aliphatic series: n-butylmercury chloride gave a 40% yield of di-n-butylmercury [104].

Hydrazine hydrate has been used for the symmetrization of optically-active organomercuries, in particular 3-bromomercuri-camphor [16, 17], 2-chloromercuricamphane [88] (diastereomeric mixture) and also products obtained by the addition of mercuric salts to unsaturated compounds [18, 19]. The configurations of these compounds, however, became inverted [17-19]. Itshouldbeborne in mind that the action of an excess of hydrazine on the adducts of mercuric salts and olefins results in replacement of the mercury by hydrogen [22], sometimes accompanied by the elimination of the OR group (but not OH) [107] and regeneration of the double bond.


The replacement of Hg with H by means of hydrazine will be described in Chapter 14.

Hydrazine hydrate has also been used to symmetrize various other RHgCl (R = Ar , a- and /3-naphthyl, a-thienyl) [108],

Symmetrization of the diastereomeric mixture of 3-bromomercuri-Z-camphor by hydrazine hydrate [ l 7 ] . 3 -Bromomercur i -1 -camphor (2 g ) are s t i r red into a solution of 0.6 g of hydrazine hydrate in 15 ml of dioxan. Af ter 30 minutes the precipitate of met-al l ic mercury is f i l t e red off and the f i l t ra te diluted with water to 150 ml . The resulting precipitate of 3 ,3 -mercur i -b is -Z-camphor is f i l t e red off and washed with water; yield; 0.6 g (50%). A f ter recrysta l l i zat ion f r o m aqueous dioxan, the substance decomposes at 200-205°C.

On the other hand, the symmetrization of exo - cis-3-hydroxy-2-norbornylmercury chloride by hydrazine in methanolic solution in the presence of alkali occurs with retention of the configuration [106a]:

Synthesis of di-eao-3-hydroxy-e®o-2-norbornylmercury [ l 06a ] . A solution of 1.28 g of NaOH in 4 ml of water and 1.09 g of 95% hydrazine we re added to a solution of 5.6 g (0.016 mo le ) of exo-c i s~3-hydroxy-2-norborny lmercury chloride in 72 ml of absolute methanol. F r e e mercury appears immediately. The solution is boiled f o r 6 hours and decanted f r om the mercury into 300 ml of ether. The mercury is washed successive ly with methanol, water and acetone, and then dried and weighed (1.814 g, 56.2%). The ethereal solution is washed with two 200-ml portions of disti l led water, dried over sodium sulfate and evaporated to about 20 ml. Cool ing y ie lds 1.243 g of precipitate; m.p. 152-152.5°C. exo-norborneol can also be separated f r om the f i l t ra te (0.6685 g, 37%); m.p. 115-127°C.

S y m m e t r i z a t i o n b y t h e A c t i o n o f S o d i u m ( P o t a s s i u m ) A l k o x i d e s

4RHgX + R-CH2ONa + 4NaOH 2R2Hg + R'COONa + 4NaX + 2Hg + 2HaO

Sodium methoxide and sodium ethoxide have been used in some cases, with varying success. Six hours of heatingof o-nitrophenyl-mercury chloride in methanol with NaOCH3 gave an 80% yield of di-o -nitrophenylmercury [78a], Poor results were, however, obtained with mercurated chloronaphthalenes [109].

Fully substituted mercury compounds in yields of 7 0-100% can be obtained by the reductive symmetrization of organomercury salts during the latter's electrolysis. In the case of methylmercury ace-tate the necessary conductivity of the aqueous solution is achieved

CH3OH NaOH

S y m m e t r i z a t i o n b y E l e c t r o l y s i s



by adding pyridine. The symmetrizations of alkylmercury sulfates and succinates (alkyl = CH3, C2H5, C4H9, and iso-C5H11) are conducted in the presence of sodium sulfate.

Symmetrization also occurs during the electrolysis of j8-chloro-vinylmercury chloride [110].

Symmetrization of methylmercury acetate [ i l l ] . The electrolysis vessel is a glass cylinder narrowing towards the bottom, fitted at the bottom with a tap, with a graphite anode contained in a porous clay chamber and with a platinum strip cathode arranged concentrically around the clay chamber at a distance of some mil l imeters. The vessel is surrounded by a water-jacket (which maintains the temperature at 30-40°C) and is f i l led with a 25% aqueous solution of methylmercury acetate to which 2 moles of pyridine have been added f o r every mole of the methylmercury acetate. At a current of 2.5 A and 30-35 V with a current density of 1.8 A/dm2 of the cathode, the electrolysis requires 2 hours 10 minutes. The yield of dimethylmercury is 92%. Current eff iciency: 90%.

Symmetrization of ethylmercury sulfate [ l l 2 ] . The process is conducted without a diaphragm, in a cylindrical vessel, 18 mm in diameter. The cathode (a layer of mercury) is placed at the bottom. The anode is a spiral of 0.5-mm platinum wire. The entire assembly is immersed in a water bath. The source of current is a bank of lead accumu-lators (6.2 V).

The electrolysis is carried out on a solution of 3 g of ethylmercury sulfate and 0.1 g of Na2SO4 in 15 ml of water (at 20°C, with a current density of 0.02 A/cm2 ) . The separa-tion of diethylmercury ceases after 3-4 hours and the material is separated f rom f ree mercury and the solution in a micro-separating funnel and dried over CaCl2 . Yield: 1.2 g (about 90%); b.p. 159°C.

The same conditions were used to symmetrize the corresponding methylmercury, propylmercury, and butylmercury salts (50°C for the first 15 minutes, then at 20°C), as well as isoamylmercury sulfate (56°C, current density 0.04 A/cm2) [112].

Symmetrization of propylmercury succinate [ l l 2 ] . A s o l u t i o n o f l g o f p r o p y l m e r c u r y succinate and 0.1 g of Na2SO4 in 15 ml of water is electrolysed at 80-90°C and a current density of 0.03 A/cm2 . At the end of the electrolysis, and after cooling of the electrolyte, dipropylmercury is separated f rom f r ee mercury and water and dried over CaCl9 . Yield: 70%; b.p. 186-187°C.

Diethylmercury was similarly obtained by electrolysis of ethyl-mercury succinate (at a current density of 0.04 A/cm2) [112].

S y m m e t r i z a t i o n b y t h e A c t i o n o f P o t a s s i u m ( S o d i u m ) I o d i d e

These two salts are excellent symmetrizing agents for many classes of organomercury compounds. The symmetrizations with KI have been studied by Whitmore and Sobatzki [113], who found that the reactions are reversible:

2RHg I + 2K I ^ R2Hg + K2Hg I4

If the R2Hg is much more soluble in the reaction medium than the RHgX (as is the case when R = C6H5), then because of the faster rate of the reverse process the reaction practically does not


proceed at all and KI cannot be used for the symmetrization of such compounds. To displace the equation to the right it is neces-sary to use an approximately tenfold excess of the KI (NaI) with respect to the RHgX.

This method has been used in several cases for the symmetriza-tion of alkenyl (but not quasicomplex) compounds of mercury [60, 180]. The perhalogenovinylmercury salts symmetrize particularly readily in the presence of NaI (KI) (and also KCNS, cf. below), even when the latter are taken in only equimolecular proportions and not in the large excess necessary for the remaining RHgX [114]. Apart from the above limitation, the method of fers a means of smooth and efficient symmetrization of the organomercury de-rivatives of aromatic hydrocarbons [115], biphenyl [116,117,124b], chloronaphthalenes [109], halogenoalkylamines [118], esters of nitrobenzoic acids [119] and heterocyclics ( a-mercurated thiophene [53, 54, 97, 120, 121] and selenophene [122] and their derivatives, a -mercurated thionaphthene [123]). Mercurated phenolic ethers and phenols with an acylated hydroxyl group can also be symmetrized in this way. Phenols with a free hydroxyl group decompose under the action of potassium iodide [124]:

The decomposition of quasicomplexes, including a-mercurated oxo-compounds in the presence of KI (and other complex-formers) is described at the beginning of this chapter and in Chapter 6.

Treatment of 2,2'-dichloromercuribiphenyl with ethanolic NaI gives the cyclic tetrameric o-biphenylenemercury [124a], It is probable that the products of the symmetrization of other dimer-curated compounds, e.g. dichloromercurithiophene [97] and di-chloromercuriferrocene [124b] (especially under the action of KI or NaI) are also polymeric (and perhaps have a ring structure).

Thus, in the presence of ethanolic NaI 1,1'-dichloromercuri-ferrocene gives a compound (C10H8FeHg)a.:

which is probably a mixture of linear polymers and perhaps some cyclic oligomers with a small value of x.


HOC6H4Hg I + 3KI + H2O - C6H5OH + K2Hgl4 + KOH


Preparation of irans-a-mereuri-bis-stilbene [60]

CeH5

\ / C = C Hg

/ \ H CeHs

A solution of 3.35 g (0.02 mole) of KI in 54 ml of acetone and 6.5 ml of water is added to a solution of 2 g (0.0021 mole) of trans -a-bromomercuristiibene (m.p. 157-158°C) in 150 ml of acetone and 10 ml of water. After being set aside for 24 hours at room tem-perature, the precipitate is fi ltered off and dried. The yield of the desired product is 1.2 g (99%); m.p. 239-241°C (from dioxan).

In the symmetrization of cis - a-bromomercuristilbene (m.p. 118-120°C) under these conditions the product had to be salted out at the end of the reaction by addition of water, because cis -a -mercuri-bis-stilbene has an appreciable solubility in aqueous acetone. The yield was 53%; m.p. 145-146°C (frombenzene/alcohol). 7.5% of unreacted RHgBr was also recovered, c is-a-Bromomer-curistilbene gives a 94% yield of cis - a-mercuri-bis-stilbene when it is symmetrized with sodium stannite and an 88% yield when it is symmetrized with ammonia.

The preparation of di-p-tolylmercury is described in [115].

Preparation of di-o-biphenylmereury [ 124a]. An ethereal solution of 57 millimoles of 0-Iithiobiphenyl (160 ml, prepared in the usual manner from o-iodobiphenyl and lithium in ether), are added in portions to a solution of 16 g of HgCl2 in 480 ml of absolute ether and the mixture boiled for an hour (until Gilman's test for active organo-metallics gives a negative result). The ether is then distilled off and the residue shaken up with 400 ml of hot water, filtered, washed with water and extracted with 700 ml of boiling ethanol. The alcoholic extract, yielding crystals on cooling, is treated with 30 g of NaI and boiled for 8 hours for complete conversion of o-biphenylylmercury chloride into di- 0-biphenyIylmercury. The latter crystallizes out when the solution is cooled to 0°C. The precipitate is filtered off and recrystallized from ligroine; needles, m.p. 161-162°C. A sample mixed with o-biphenylylmercury chloride shows a depression of the melting-point. Yield; 84%.

Preparation of di-(3-biphenylyl)mereury [ 117]. 3-Chloromercuribiphenyl (4.58 g) is boiled for 20 hours with 7.50 g of NaI in 250 ml of ethanol and the mixture filtered hot. Di-(3-biphenylyl)mercury, m.p. 187-189°C, crystallizes out of the filtrate. Yield: 56%. After crystallization from n-heptane, the melting-point is 188.5-189°C.

Preparation of di-a-thienylmereury [53]. A solution of 10 g of NaI in 75 ml of acetone is added to a solution of 10 g of a-thienylmercury chloride in 175 ml of acetone. After several hours the resulting white precipitate is fi ltered off and the filtrate diluted with a large volume of water. This operation gives rise to further precipitation. The two precipitates are combined, washed with water and recrystallized from benzene. Yield: 5.3 g (92.6%); m.p. 198-199°C.

Preparation of 2,5,2 ',5 '-dithienyldimereury [97] .


A solution of 0.75 g (2 mo les ) of Nal in 80 ml of pyridine is added, over 6 hours, with vigorous st irr ing, to 1 g of 2,5-dichloromercurithiophene dissolved in 100 ml of pyridine. The mixture is f inal ly s t i r red f o r a further 45 minutes. The precipitate is f i l t e red off and the strongly held pyridine removed by prolonged treatment with steam, f i l trat ion and successive washing with hot water, alcohol and ether. A f ter drying in vacuum at 60°C, the y ie ld is 0.37 g (72%). The substance is infusible, and may be a polymer:

Potassium cyanide was the first symmetrizing agent, used by Buckton [125] in 1858 to obtain dimethylmercury and diethylmercury. It is rarely used in the aromatic series, though it affords reasonably good yields. Sodium cyanide is an excellent agent for converting /3-naphthylmercury chloride into di-(/3-naphthyl)mercury [108].

In concentrated solution, KCN is one of the best symmetrizing agents for allylmercury iodide. In contrast to the other symme-trizing agents, it effects this conversion quantitatively in the cold [83]. It is unsuitable for the symmetrization of quasicomplexes.

The range of the applications of these agents is the same as that of KI and NaI, but the yields are somewhat inferior. For example, KCNS and NaCNS have been used to symmetrize phenolic ethers [125] and thiophene derivatives [97, 126].

Like Na(K)I and P(C6H5)3, KSCN is the symmetrizing agent par excellence for the perhalogenovinylmercury salts; the action of 1 equivalent of KCNS on such salts results in up to 90% yields of the corresponding R2Hg [114]. Like the other complex-formers, KCNS is unsuitable for the symmetrization of quasicomplex com-pounds .

Preparation of bis-perchlorovinylmercury [114]. KCNS (1.36 g, 0.014 mo l e ) in 25 ml of anhydrous acetone is added drop by drop, with rapid st i rr ing, to 5.0 g (0.014 mo le ) of perchlorov iny lmercury chloride dissolved in 25 ml of acetone. The resulting white pre-cipitate (0.71 g ) is f i l t e red off . Evaporat iono f the f i l t ra te to dryness yie lds 6.3 g of another white precipitate (m.p. 149-154°C), which is washed with f i ve 10-ml portions of hot pentane. The remaining white crysta ls (2.4 g; m . p . 140-150°C) g ive 2.0 g (91%) of m e r -curic thiocyanate af ter recrysta l l i zat ion f r om water; m.p. 175°C. Evaporation of the pentane gives 2.8 g (88%) of b is -perchlorov iny lmercury ; m.p. 72-73°C ( f rom pentane).

S y m m e t r i z a t i o n b y t h e A c t i o n o f P o t a s s i u m o r S o d i u m C y a n i d e s

2RHgX + 4KCN - R2Hg + 2KX + K2Hg (CN)4

S y m m e t r i z a t i o n b y t h e A c t i o n o f P o t a s s i u m a n d S o d i u m T h i o c y a n a t e s

2RHgX + 4KCNS - R2Hg + 2KX + K2Hg (CNS)4



S y m m e t r i z a t i o n b y t h e A c t i o n o f C a l c i u m C h l o r i d e

This reagent has been used for a-thionaphthenylmercury acetate [124] and for the product obtained by the addition of mercuric acetate to dimethylphenylphenylethynylethylene glycol [127],

S y m m e t r i z a t i o n b y t h e A c t i o n o f S o d i u m T h i o s u l f a t e

2RHgX + 2Na2S203 - R2Hg + 2NaX + Na2 [Hg (S2O3)2Ja

Sodium thiosulfate is a good agent for the symmetrization of compounds with labile mercury, such as the mercurated amines [92, 128-131] and phenols [72, 92], and also the mercury derivatives of camphor [12, 16] and certain heterocyclics: a-(but not /3-) mer -curated furan [132] and furyl alcohol [133]. its has also been used to symmetrize mercurated pyridine [75], quinoline [134] and met-allocenes [124b, 135-137]. During the symmetrization of 3-bromo-mercuricamphor, some way must be found to prevent the reverse interaction of the symmetric organomercury with the mercuric salt [16]: the process is carried out in the heterogeneous benzene-water mixture, so that the more benzene-soluble R2Hg is removed f rom the sphere of reaction.

The decomposition of quasicomplex organomercury compounds by Na2S2O3 is described earl ier in this chapter and in Chapter 6.

Preparation of di-p-aminopheny lmercury [ 129, 130], A solution of 16 g of sodium thiosulfate in 200 ml of water, heated to 45-50°C, is stirred into a suspension of 20 g of p-aminophenylmercury acetate in 75 ml of water at the same temperature. The acetate dissolves and a little mercuric sulfide is precipitated. The mixture is heated (not above 65-70°C) and fi ltered. The fi ltrate, the temperature of which does not exceed 55°C, is treated with a solution of 90 g of sodium thiosulfate in 70 ml of water. The pre-cipitate of di-p-aminophenylmercury is f i l tered off after 2 hours, washed with water and dried. Yield: 8 g (73%). After recrystall ization from dioxan, the melting-point is 174°C (capillary introduced into a bath preheated to 165°C). The same method has been used for the symmetrization [129] of compounds containing dialkylamino groups; yields: 70-75%.

Preparation of di-p-am ino-0-bromopheny lmercury [ 131]. 4-Acetoxymercuri-2-bro-moaniline is st irred into a paste with an excess of 50% aqueous sodium thiosulfate, set aside for 48 hours and f i ltered. White plates; m.p. 125°C.

Preparation of di-m-hydroxy phenylmercury [72]. OT-Hydroxyphenylmercurychloride (8 g) is dissolved in a solution of 17 gof crystalline sodium thiosulfate in 110 ml of water. Turbidity appears soon after mixing and is followed by precipitation. After 24 hours the precipitate is f i l tered off, washed and recrystal l ized f rom alcohol. Weight: 4.6 g (100%). The substance decomposes above 265° C without melting.

Preparation of di-a-furylmercury C132]. a-Furylmercury chloride (0.1 mole) is rapidly added to 50 g of Na2S2O3 in 200 ml of water and the mixture shaken vigorously for a few minutes. Rapid precipitation takes place. After 8 hours the solid material is f i l -tered off (yield: 95%) and recrystal l ized from aqueous acetone or from alcohol; m.p. 114°C.


Ferrocenylmercury chloride is smoothly symmetrized to di-ferrocenylmercury by a saturated aqueous solution of sodium thiosulfate [137]. Chloromercuricyclopentadienyltricarbonylman-ganese gives a 79% yield of mercuri-bis-cyclopentadienyltricar-bonylmanganese [135].

Preparation of mercuri-bis-cyclopentadienyltricarbonylmanganese [ 135]. A solution of 2.2 g (0.005 mo le ) of chloromercuricyclopentadienyltr icarbonylmanganese in 2 ml of acetone is added to 8 g of Na2S2O8 in 30 ml of water. The mixture is s t i r red f o r 2 hours at room temperature and then set aside overnight. The precipitate is f i l t e red off, washed with water, dried over CaCl 2 and extracted with benzene. Evaporation of the benzene ex-tract yields 1.19 g (78.3%) of pale-yel low crystals, soluble in alcohol; m.p. 174.S0C (with decomposition). A f ter two precipitations f rom benzene or C C I 4 the melting-point rose to 178-179°C [138],

S y m m e t r i z a t i o n b y t h e A c t i o n o f A l k a l i M e t a l a n d A l k a l i n e E a r t h S u l f i d e s

2RHgX + K2S R2Hg + 2KX +HgS

Symmetrizations with K2S, Na2S, or Ba(HS)2 are not very con-venient and are now little used. Organomercury sulfides are ob-tained as intermediate products, decomposing on heating into R2Hg and HgS.

The only way of symmetrizing a-mercuricamphenilone salts is to heat the sulfide to 214-220°C: this leads to an 80% yield of di-et -camphenilonylmercury [139], Alkali metal sulfides have been applied to the symmetrizations of the organomercury derivatives of aromatic hydrocarbons [56], nitro compounds [140], acids [141], amines [142], phenols [125, 144] and heterocyclics [124],

McCutchan and Kobe [145] have worked out the conditions for conversion of over 90% of phenylmercury acetate into diphenyl-mercury by this method.

Preparation of diphenylmercury [ 145]. (a) Decomposition in the absence of solvent: 75 g of phenylmercury acetate are dissolved (in a 2 - l i t e r Er l enmeyer f lask) in 1 l i ter of dist i l led water containing 100 g of ammonium acetate and 25 ml of concentrated ammonia. Hydrogen sulfide is passed in t i l l precipitation ceases. The precipitate is then f i l t e red off, washed with disti l led water, aspirated to the maximum possible dryness, dried f o r 20 minutes at 120°C and aspirated once more on the f i l t e r . Final ly, it is decomposed in an oven over a period of 1 hour. The mater ial is then cooled, ground up and extracted with 600 ml of acetone. The precipitate of mercur ic sulf ide is f i l t e red off and washed with acetone. Diphenylmercury is precipitated with 3.5 l i ters of water, f i l t e red and dried overnight in air ; y ie ld: 33.7 g (85.4%).

(b) Decomposition in toluene: the precipitated phenylmercury sulfide is partially dr ied by washing with 1 l i ter of boiling water and pressing out with a spatula under suction. It is then placed in a 2- l i ter round-bottom f lask fitted with a ref lux condenser and a Dean-Stark water trap. T o the f lask is added 500 ml of toluene. The mater ial is ref luxed f o r 35 minutes at a temperature suff icient to remove all the water during this time. The f lask and the precipitate are washed with 200 ml of hot toluene to remove any remaining diphenylmercury and the solvent dist i l led out to 75 ml. The solution is placed in a dist i l -lation flask and allowed to cool. Diphenylmercurycrysta l l i s ingout at this point is f i l t e red



off. The remaining toluene is removed by adding 200 ml of ethanol and distilling the mix-ture. Diphenylmercury is recovered from the alcohol by precipitation with about 5 volumes of water. Only a small amount of toluene remains after the f i rst distillation; it is allowed to evaporate off and the residual diphenylmercury is weighed; yield: 19.0 g (97.5%).

Preparation of di-(o-nitro-p-tolyl)mercury [ 140] -

NO2

( H * c -0 " l H g

4-Chloromercuri-2-nitrotoluene (3.7 g) added to an aqueous solution of 1.2 g of crystalline Na2S is gradually converted into a colorless sulfide. The mixture is heated for 2 hours on a water bath and the black product fi ltered, washed, dried and extracted with acetone. The dark extract is f i ltered cold; black colloidal HgS passes through the fi lter, leaving a white crystalline residue. This operation is repeated several times and the material finally recrystall ized from toluene; m.p. 291°C.

When phenylmercury hydroxide is added at room temperature to carbon disulfide, the mixture effervesces and forms diphenylmer-cury in a yield of 30% [146]. Phenylmercury sulfide is probably formed as an intermediate:

2C6H5HgOH + 2CS2 - (C8H5Hg)2S + 2COS + H2S

(C6H6Hg)2 S - HgS + (C6H5)2 Hg

(see also "Anion exchange in organomercury salts" Chapter 14).

S y m m e t r i z a t i o n b y t h e A c t i o n o f A l k a l i s

2RHgX + 2KOH - R2Hg + 2KX + H2O + HgO

Alkali material hydroxides can also be used as symmetrizing agents, but since the mercury then forms the slightly soluble mercuric oxide which can react with the H2Hg to form RHgOH, the symmetrizations do not proceed as far as with the usual agents [147].

S y m m e t r i z a t i o n b y t h e A c t i o n o f A m m o n i a

2RHgX + 2NH3 R2Hg + HgX2-(NH3)2

Ammonia is a mild and effective agent for the symmetrization of the addition products obtained from mercuric salts and unsaturated aliphatic compounds, and is consequently used widely in this field. Symmetrizations with ammonia are the best studied from the points of view of mechanism and stereochemistry. Thus, the configurations of stereoisomers are not inverted (this aspect of the reaction has


hardly been studied at all in the case of the other symmetrizing agents). This method is used successfully to an ever-increasing extent for the symmetrization of organomercury compounds in cases where severe conditions should be avoided (see for example [148, 149]) and for the a-mercurated aliphatic oxo-compounds and acids.

Cyclopentadienylmercury chloride has been symmetrized by the action of ammonia [143],

The reaction is usually carried out in chloroform or dichloro-ethane and sometimes in benzene. Both cis- and trans -ClHgCH= CHCl [150, 151] can be symmetrized in this way to di-(/3-chloro-vinyl)mercury.

Preparation of trans,tfWis-di-(/3-chlorovinyl)mercury [ l50] , A current of ammonia is passed through a solution of trans -/3-chlorovinylmercury chloride in chloroform. The white precipitate of mercuriammonium chloride is f i l tered off. Evaporation of the f i l trate gives (ClCH=CH)2Hg; m.p. 60°C.

Preparation of ois,cis-di-(/3-chlorovinyl)mercury C1 Si] - Ammonia is passed for 6 minutes into a solution of 2.6 g of cis -,3-chlorovinylmercury chloride (m.p. 73°C) in 35 ml of dry benzene, at a rate of 80-100 bubbles per minute. The precipitate is f i l tered off. The f i l trate is f i rst slowly concentrated at 30-35°C and then stored for several days in a vacuum desiccator at 10 mm. The weight of the resulting colorless liquid is 1 g (yield: 70.9%). The compound does not solidify even on cooling to -70°C; d,20 2.8090; n c 20 1.6308.

Ammonia is also the best agent for the symmetrization of a-halogenomercuri ketones [152], which are hydrolysed by aqueous solutions of all the other symmetrizing agents. To avoid the un-desirable effects of an excess of ammonia on the yield of the resulting mercuri-bis-ketone, the ammonia is added in dichloro-ethane or chloroform solution to the halogenomercuri ketone until precipitation ceases. The reaction is conducted at room temperature, as the yields become , lower at increased tempera-tures [152].

Preparation of diacetonylmercury C152]. A solution of ammonia in dichloroethane is added to a solution of 9 g (0.03 mole ) of chloromereuriacetone in 250 mi of dichloro-ethane until precipitation ceases. The precipitate is f i l tered off and washed with di-chloroethane. The solutions are then combined and the dichloroethane evaporated away in the cold. The yield of diacetonylmercury is 4.5 g (100%); m.p. 69°C ( from benzene/ heptane).

The products of the addition of HgCl2 to the acetylenic alcohols [153] and to acetylenic acids and their esters [154] do not sym-metrize under the action of ammonia (or other symmetrizing agents) but decompose into the starting components. Chloromer-curiacetic esters also do not symmetrize with ammonia, but form complexes [68], On the other hand, the esters of a-halogeno-mercuriarylacetic acids symmetrize smoothly in the presence of ammonia in chloroform or other solvents [6-11].



The mechanism of the symmetrization with ammonia and the structure of the transition state are described at the beginning of this chapter. Data on the "Cosymmetrization* of RHgX and R'HgX with ammonia and the formation of RHgR' are given both at the beginning of this chapter and in Chapter 12.

S y m m e t r i z a t i o n b y t h e A c t i o n o f P y r i d i n e

2RHgCl + C5H5N - R2Hg + C5H5N • HgCl2

RHgCl (where R represents indanedione derivatives), which according to Hantzsch [155] are C-Hg compounds, symmetrize in the cold in the presence of pyridine.

S y m m e t r i z a t i o n b y t h e A c t i o n o f T r i e t h a n o l a m i n e

Phenylmercury acetate has been symmetrized [156] by triethanol-amine in the presenceof lactic and citric acids. The initially formed double compound decomposes on heating to diphenylmercury:

C3H5HgOCOCH3 + N(CH2CH2OH)3-C6H5Hg(CH3CO2 )N(CH2CH2OH)3- (C6H5 )2 Hg

+ CH3CO2Hg(CH3CO2)N(CH2CH2OH)3 + N(CH2CH2OH)3.

S y m m e t r i z a t i o n b y t h e A c t i o n o f U n s a t u r a t e d C o m p o u n d s

The reaction between organomercury bases and unsaturated compounds gives rise to asymmetrical organomercuries [157], for example:

OR C H 3 O H /

ArHgOH + CH 2 =CHOR ^ArHgCH2CH \

OCH3

which immediately decompose into a mixture of two symmetrical products:

OCH3 OCH3

2ArHgCH 2CH / ' - Ar2Hg + Hg ( C H 2 - C H ^

\ V \ OR OR

The reaction can be used [157] for the symmetrization of organo-mercury salts under very mild conditions; for this purpose, there is no need to isolate the ArHgOH obtained by boiling ArHgX with CHgOH/KOH.


The active unsaturated compounds that have been used in this way are vinyl ethers and keten diacetal. The simultaneously forming mercuri-bis-acetaldehydes andmercuri-bis-ketones (or the deriva-tives of both these series) were not isolated as such but in the form of organomercury salts by the addition of mercuric salts to the filtrate after separation of the Ar2Hg.

Preparation of diphenylmercury [ l57 ] . To 5 g of phenylmercury chloride dissolved in 100 ml of methanol are added 26.5 ml of 40% methanolic KOH. The mixture is boiled for 30 minutes, cooled and then f i ltered. The f i l trate is treated with 1.5-2 g of vinyl ethyl ether. On the following day one-third of the solvent is distilled off and the pre-cipitating diphenylmercury f i l tered off. Yield: 2.6 g (92%); m.p. 119-120°C.

Analogous conditions are used to obtain 2.7 g of d i -p-to ly lmercury (95.5%) (m.p. 237-238 C ) f rom 5 g of p-toly lmercury chloride and 2 g of vinyl ethyl ether.

S y m m e t r i z a t i o n b y t h e A c t i o n o f B u t y l - l i t h i u m

This was the method used for the symmetrization of the stereo-isomeric mercury derivatives of stilbene. The reaction probably proceeds via an unstable, asymmetrical, fully substituted mercury compound [158]:

2C6H5CH=C (HgCl) C6H5 + 2C4H9L1 -» [2C6H5CH=C (HgC4H9) C6H5 + LiCl] -- (C6H5CH=CC6H5)2Hg + (C4H9)2 Hg.

Preparation of Jrans-a-mercuri-bis-stilbene [ l58 ] . A solution of 1 g of trans-a-chloromercuristilbene in a mixture of 40 ml of benzene and 60 ml of ether is prepared. To this is added an equimolecular amount of a titrated ethereal solution of butyl-lithium at -40 to -30°C under a current of nitrogen. Precipitation begins at once. The mixture is set aside at this temperature for 40 minutes and then decomposed with 50 ml of 3% HCl. The precipitate of trans-a-mercuri-bis-stilbene is f i l tered off and the layers separated. This procedure yields 0.5 g (83%) of trans-a-mercuri-bis-stilbene; m.p. 239-241°C. The ether-benzene layer gives a small amount of trans - a-chloromercuristi lbene.

In the same way, 1 g of cis-a-chloromercuristilbene gives 0.4 g (66%) of cis-a-mercuri-bis-sti lbene [158], isolated, after removal of the solvents under vacuum, from the CaCl2~dried ether-benzene layer. After recrystall ization from a mixture of alcohol and benzene, the melting-point is 145-147°C. The reaction is conducted in an atmosphere of nitrogen.

In the attempt to induce transmetallation of chloromercuricyclo-pentadienyltricarbonylmanganese under the influence of butyl-lithium, the former compound was found to symmetrize to di(cyclo-pentadienyltricarbonylmanganesemercury [ 138].

S y m m e t r i z a t i o n b y t h e A c t i o n o f D i p h e n y l m e r c u r y

This agent combines with the forming mercuric halide to give the sparingly soluble phenylmercury halide which can be easily separated from the more soluble symmetrical compound [159]. It has been demonstrated with the aid of NMR spectra [182] that



the reaction proceeds with the intermediate formation of asym-metrical RHgCgH5.

Diphenylmercury has been used to symmetrize compounds con-taining "mobile" hydrogen: acetonylmercury chloride, the ethyl ethers of a-bromomercuri- and p-bromo-a-bromomercuriphenyl-acetic acid, 3-bromomercuri-3-benzylcamphor and trans-/3-chloro-vinylmercury chloride.

Preparation of the ethyl ester of a-mercuri-bis-phenylacetic acid [ l 59 ] . Aso lut ion of 4.5 g (0.01 mo le ) of ethyl a.-bromomercuriphenylacetate in 30 ml of chloro form is poured into a solution of 1.8 g (0.005 mo le ) of diphenylmercury in 15 ml of chloroform. The precipitate of phenylmercury bromide is f i l tered off and washed with a small volume of chloro form. Evaporation of chloroform f r om the f i l t rate g ives 2.28 g (85°J;) of the required product; m.p. 104-105°C.

S y n m e t r i z a t i o n b y t h e A c t i o n o f T e r t i a r y P h o s p h i n e s

2RHgX + 2R;P -* R2Hg + (R^P)2 HgX2

The complex-forming tertiary phosphines are selective sym-metrizing agents. The character of their reaction with RHgX depends both on R and R' and on the medium in which the process is carried out. Thus, methylmercury bromide is symmetrized by triethylphosphine in benzene, but in ether it forms the phosphonium salt [CH3HgP(C2H5)3]Br [160], Triphenylphosphine is generally used for the symmetrizations. With CH3HgBr [148] in ether and with cis- [84] and trans - [114] ,S-ClCH=CHHgCl in alcohol, t r i -phenylphosphine forms only the complexes [(CGH5)3P]2.HgHal2, but in the case of perchlorovinylmercury chloride in ether or ethanol this complex is accompanied by an up to 88% yield of the symme-trization product [CCl2=CCl)2Hg [114]. The methoxymercuration product of carbon monoxide, carbomethoxymercury chloride, gives bis-carbomethoxymercury with triphenylphosphine in benzene [161]. Phenylmercury chloride gives a 1:1 complex with triphenylphos-phine, but does not symmetrize [161].

On the other hand, the following reaction takes place when phenyl-mercury acetate is heated for 30 minutes in benzene with tributyl-phosphine [162a]:

2C6H6HgOCOCH3 + (n-C4Hg)3P - Hg + (C0H5)2 Hg + (CH3CO)2O + (H-C4H0)3 PO

Preparation of bis-perchlorovinylmercury. Triphenylphosphine (3.7 g, 0.014 mole ) in 350 ml of ethanol is added to 0.5 g (0.014 mole ) of perchlorovinylmercury chloride in 50 ml of ethanol. A white precipitate appears almost immediately, which is f i l te i i off and washed with alcohol. Y ie ld : 4.8 g (86%). (C 6 H b ) 3 P -HC l 2 , m.p. 274-276°C. centration of the combined ethanolic solutions to one-tenth of their volume g ives 2.8 g (88%) of b is-perchlorovinylmercury; m.p. 72-73°C.


Preparation of bis-carbomethoxymercury [ l 6 l ] . A solution of 23 g (0.08 mole ) of carbomethoxymercury chloride in 250 ml of benzene is poured into a solution of 20.8 g (0.08 mole ) of triphenylphosphine in 250 ml of benzene. T h e triphenylphosphine-HgCl2 complex which immediately precipitates, is f i l t e red of f . Evaporation of the f i l t ra te under vacuum, at a temperature not exceeding 50°C, g ives the required product, which is recrys ta l l i zed f r o m ether; m.p. 84.5°C.

S y m m e t r i z a t i o n b y t h e A c t i o n o f P e n t a c a r b o n y l i r o n a n d i t s D e r i v a t i v e s

HgFe(CO)4 and R2Hg are the final products of the action of pentacarbonyliron on phenylmercury hydroxide in methanol [164] and of the reaction which takes place when a solution of iron carbonyl hydride is added to a solution of methylmercury hydroxide or some other organomercury base [164].

The action of CaFe(CO)4 on RHgOH (where R = CgH5, C2H5) gives (RHg)2Fe(CO)4 which immediately disproportionates into R2Hgand HgFe(CO)4. In the case of R = CH^thecorresponding(RHg)2Fe(CO)4

is stable but it too disproportionates slowly into (CH3)2Hg and HgFe (CO)4 [163].

S y m m e t r i z a t i o n b y t h e A c t i o n o f A l u m i n a

o-Iodophenylmercury iodide symmetrizes in 94% yield [165] on being chromatographed on an alumina column with a mixture of benzene and cyclohexane.

S y m m e t r i z a t i o n s i n t h e A b s e n c e o f S y m m e t r i z i n g A g e n t s

In certain rare eases, organomercury salts undergo spontaneous symmetrization on heating. Thus, mercurated benzanthrone sym-metrizes on being heated to its melting-point [166], Phenylmercury fluoride heated to 200°C at a pressure of 10 mm transforms into diphenylmercury [167], 2,5-Dichlorophenylmercury acetate sym-metrizes [71] at 142-143°C in p-xylene or mesitylene and CH2IHgI forms (CH2I)2Hg after 2% hours of boiling in tetrahydrofuran [186],

Heating of o-iodophenylmercury iodide results in the formation of bis-o-iodiphenylmercury [164],

On being heated for 75 minutes to 145°C in nitrogen, (CgH5)3

SiOHgCeH5 gives diphenylmercury [168] and phenylsiloxanes.

Preparation of bis-2,5-(diehlorophenyl)mercury [ 7 l ] . A solution of 0.5 g of acetoxy-mercur i -p-d ich lorobenzene in 17 ml of p -xy lene (or mes i ty lene ) is heated f o r 10 hours at 142-143°C. Removal of a large proportion of the solvent gives 0.21 g of the required product, which is recrys ta l l i zed f r o m a mixture of acetone and chloro form; m.p. 237°C. Meta l l ic mercury is found in the reaction products.



b) Reaction Reverse to Symmetrization

This process, the preparation of organomercury salts from fully substituted organomercuries and mercuric salts,

R2Hg + HgX2 2RHgX

is a reaction of considerable preparative importance. As a rule, the reaction proceeds smoothly and in most cases it is sufficient to heat equimolar amounts of the reactants in alcohol, acetone, tetrahydrofuran [80], or even ether [169], In certain cases, espe-cially with the mercuric salts of organic and dibasic acids [170, 171], the reaction is conducted by fusion without any solvent, and even the heating may be unnecessary if one of the reactants is a liquid. In the case of tribasic acids the reaction is carried out without a solvent, in the presence of a small quantity of water [172], and in the case of the mercuric salts of organic acids also in the medium of the corresponding acids [80].

Nesmeyanov and Borisov [151, 173, etc.] showed that the con-figuration of stereoisomers is strictly retained during the formation of organomercury salts by the reaction of mercuric salts with trans ,trans- and cis, cis- symmetrical products of the addition of mercuric salts to acetylenic compounds.

Configuration is also preserved during the interaction of optically active symmetric organomercuries with mercuric salts.

For the reaction Of 203HgCl2 with RHgR', occurring with retention of the configuration and isotope exchange, see under: "Isotope ex-change of organomercury compounds with radiomercury and with compounds containing radiomercury", Chapter 14.

Diastereomeric mixtures obtained by the interaction of optically active symmetric organomercury compounds (di-s-butylmercury and bis-2-methylhexyl-5-mercury) with a mercury salt of mono-ethyl ester of ^-tartaric acid were resolved by crystallization into optical antipodes which were separated in the form of stable bromides by treatment with calcium bromide [174],

s-Butylmercury tartrate and I-phenylglycollate have also been resolved into optical antipodes [43].

Cyclic organomercury compounds containing the mercury atom in the ring react with mercuric halides with ring cleavage and the formation of alkyl(aryl)mercury halides [100,175]. Thus, hexameric o -phenylenemercury gives o-bis-chloromercuribenzene on being boiled for 8 hours with HgCl2 in acetone solution [175].

The preparation of RHgNO3 (R = aryl [138, 176, 177], arylalkyl, or alkyl [138, 176]) by the reaction of R2Hg in acetone with aqueous mercuric nitrate is carried out in the presence of nitric acid to prevent the formation of a basic nitrate.

Like other RHgX, arylmercury fulminates have been made by the reaction of R2Hg with Hg(CNO)2 [185],


In certain cases (when the C-Hg bond in R2Hg has a partial ionic character) the reaction reverse to symmetrization does not take place. Thus, the attempts at the preparation of C6H5C=CHgI from (C6H5C=C)2Hg and HgI2 were unsuccessful [162], (CF3CFCF3)2Hg also does not react with HgCL, (24 hours at 100°C) [178].

Preparation of methyl m-bromomercuri benzoate [74]. The methyl ester of mercuri-bis-m -benzoic acid (0.12 g), 0.09 g of HgBr2 and 2 ml of ethanol are heated for 2 hours in a sealed tube on a water bath. The tube is then cooled, broken open and the alcohol gently removed. Yield: 0.22 g (90%). Recrystallization f rom benzene; m.p. 204°C.

Preparation of /3-naphthy lmercury chloride [ 170]. A solution of di-^-naphthy lmercury and mercuric chloride in pentanol is boiled. The /3-naphthylmercury chloride which pre-cipitates on cooling is recrystal l ized from ethanol; m.p. 2710C.

Preparation of ethylmercury succinate [ l 7 l ] . Diethylmercury (2.6 g) is heated to 100"C on a water bath with 3.2 g of mercuric succinate. The product dissolves com-pletely in alcohol (mercuric succinate is practically insoluble in alcohol). Recrystal-lization from alcohol. The yield of pure substance is 4.7 g (81%); m.p. 157-158°C.

Preparation of cis-/3-chlorovinylmercury chloride [ 151]. To a solution of 0.15 g (0.00046 mole) of cis-di-(/3-chlorovinyl)mercury in 8 ml of the same solvent is added 0.125 g (0.00046 mole ) of HgCl2 in 8 ml of dry ether. Soon after that a sample withdrawn f rom the mixture and treated with alkali shows the absence of the mercuric ion. After evaporation of the solvent the remaining white crystalline precipitate melts at 77-78°C; yield: 0.26 g (96%). After recrystall ization from a 1:2 mixture of benzene and petroleum ether, the melting-point r ises to 78.5-79°C.

For the preparation of ethylmercury chloride, see [179].

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2114 (1957). 111. I. L. Maynard and H. C. Howard, ibid., 123, 960 (1923). 112. N. N. Mel'nikov and M. S. Rokitskaya, Zh. obshch. Khim.,

7, 2596 (1937). 113. F. C. Whitmore and R. J. Sobatzki, J. Am. chem. Soc, 55,

1128 (1933). 114. D. Seyferth and R. H. Towe, Inorg. Chem., 1, 185 (1962). 115. Sintezy organicheskikh preparatov [Synthesis of organic

preparations], Coll. 1, IL, Moscow, 1949. p. 201. 116. S. Lamdan, Revta asoc. bioquim. argent., 114, 295 (1947);

Chem. Abstr., 43, 4236 (1949).


117. M. D. Rausch, J. inorg. nucl. Chem., 1, 414 (1962). 118. F. C. Whitmore, J. Am. chem. Soc., 37, 1841 (1915). 119. F. C. Whitmore and E. Middleton, ibid., 44, 1546 (1922). 120. W. Steinkopf, Justus Liebig's Annin Chem., 424, 40 (1921). 121. W. Steinkopf and P. Leonhardt, ibid., 495, 166 (1932). 122. M. T. Bogert and P. P. Herrera, J. Am. chem. Soc., 45,

328 (1923); 48, 223 (1926). 123. F. Challenger and S. A. Mil ler, J. chem. Soc., 1005 (1939). 124. F. C. Whitmore and E. Middleton, J. Am. chem. Soc., 45,

1753 (1923). 124a. G. Wittig and W. Herwig, Ber. dt. chem. Ges., 88, 962 (1955). 124b. M. D. Rausch, J. org. Chem., 28, 3337 (1963). 125. G. B. Buckton, Justus Liebig's Annln Chem., 108,105 (1858). 126. W. Steinkopf, ibid., 428, 123 (1922). 127. E. D. Venus-Danilova, Trudy leningr. tekhnol. Inst., 60, 32

(1960). 128. W. Schoeller and W. Schrauth, Ber. dt. chem. Ges., 53, 634

(1920). 129. V. P. Chalov, Zh. obshch. Khim., 18, 608 (1948). 130. A. E. Borisov (in the press). 131. L. Vecchiotti, Gazz. chim. ital., 58, 243 (1928). 132. H. Gilman and G. F. Wright, J. Am. chem. Soc., 55, 3302

(1933). 133. W. J. Chute, W. M. OrchardandG. F. Wright, J. org. Chem.,

6, 157 (1941). 134. T . Ukai, Chem. ZentBl., 1, 1108 (1929). 135. A. N. Nesmeyanov, K. N. Anisimov and Z. P. Valueva, Izv.

Akad. Nauk SSSR, Otdel, khim. Nauk, 1683 (1962). 136. A. N. Nesmeyanov, V. A. Sazonova, V. N. Drozd and L. A.

Nikonova, Dokl. Akad. Nauk SSSR, 131, 1088 (1960). 137. A. N. Nesmeyanov, E. G. Perevalova, R. V. Golovniya and

O. A. Nesmeyanova, ibid., 97, 459 (1954). 138. M. Cais and J. Kozikowsky, J. Am. chem. Soc., 82, 5667

(1960). 139. A. N. Nesmeyanov and I. I. Kritskaya, Dokl. Akad. Nauk

SSSR, 121, 477 (1958). 140. S. Coffey, J. chem. Soc., 128, 639 (1926). 141. W. Schoeller, W. Schrauth and R. Hueter, Ber. dt. chem.

Ges., 53, 637 (1920). 142. L. Pesci, Gazz. chim. ital., 23, 529 (1893); 28, 446 (1898). 143. A. N. Nesmeyanov, G. G. Dvoryantseva, N. S. Kochetkova,

R. B. Materikova and Yu. N. Sheinker, Dokl. Akad. Nauk SSSR, 159, 847 (1964).

144. E. Fourneau and A. Vila, J. Pharm. Chim., Paris, 6, 433 (1912).

145. R. T. McCutchan and K. A. Kobe, Ind. Engng Chem., 46, 675 (1954); U.S. Pat. 2,628,241 (1953).

146. W. T . Reichle, Inorg. Chem., 1, 650 (1962).


147. F. C. Whitmore, E. R. Hanson and F. L. Carnahan, J. Am. chem. Soc., 51, 894 (1929).

148. 0. A. Reutov and M. A. Besprozvannyi, Dokl. Akad. Nauk SSSR, 80, 765 (1951).

149. A. N. Nesmeyanov and O. A. Reutov, Izv. Akad. Nauk SSSR, Otdel. khim. Nauk, 655 (1953).

150. W. J. Jenkins, J. chem. Soc., 119, 747 (1921). 151. A. N. Nesmeyanov, A. E. Borisov and A. N. Gus'kova, Izv.

Akad. Nauk SSSR, Otdel. khim. Nauk, 639 (1945). 152. A. N. Nesmeyanov, I. F. Lutsenko and R. M. Khomutov, Dokl.

Akad. Nauk SSSR, 88, 837 (1953). 153. A. N. Nesmeyanov and N. K. Kochetkov, Izv. Akad. Nauk

SSSR, Otdel. khim. Nauk, 76 (1949). 154. A. N. Nesmeyanov, N. K. Kochetkov and V. M. Dashunin,

ibid., 77 (1950). 155. A. Hantzsch and F. Gajewski, Justus Liebig's Annln Chem.,

392, 302 (1912). 156. U.S. Pat. 2,423,261 (1947); Brit. Pat. 605,442 (1948). 157. I. F. Lutsenko and E. I. Yurkova, Izv. Akad. Nauk SSSR,

Otdel. khim. Nauk, 27 (1956). 158. A. N. Nesmeyanov, A. E. Borisov and N.A . Vol'kenau, ibid.,

992 (1954). 159. O. A. Reutov, I. P. Beletskaya and L. P. Filippenko, Nauch.

Dokl. vyssh. Shk., Khim. khim. Tekhnol., 754 (1958). 160. R. J. Cross, A. Lauder and G. E. Coates, Chemy Ind., 2013

(1962). 161. F. E. Paulik and R. E. Dessy, ibid., 1650 (1962). 162. R. E. Dessy, W. L. Budde and C. Woodruff, J. Am. chem.

Soc., 84, 1172 (1962). 162a. T . Mukajama, J. Kuwajima and Z. Suzuki, J. org. Chem.,

28, 2024 (1963). 163. F. Hein and E. Heuser,Z. anorg. allg. Chem., 249, 293 (1942);

Chem. Abstr., 37, 3685 (1943). 164. F. Hein and H. Pobloth, Z. anorg. allg. Chem., 248, 84 (1941);

Chem. Abstr., 37, 2676 (1943). 165. G. Wittig and H. F. Ebel, Justus Liebig's Annln Chem., 650,

20 (1961); Angew. Chem., 72, 564 (1960). 166. A. Bernardi, Gazz. chim. ital., 67, 380 (1937); Chem. ZentBl.,

11, 2833 (1937). 167. G. F. Wright, J. Am. chem. Soc., 58, 2653 (1936). 168. A. K. Ghosh, C. E. Hansing, A. I. Stutz and A. G. MacDiarmid,

J. chem. Soc., 403 (1962). 169. R. N. Meals, J. org. Chem., 9, 211 (1944). 170. A. Michaelis, Ber. dt. chem. Ges., 27, 244 (1894). 171. N. N. Mel'nikov and M. S. Rokitskaya, Zh. obshch. Khim.,

7, 2518 (1937). 172. N. N. Mel'nikov and M. S. Rokitskaya, ibid., 11, 592 (1941);

Zh. prikl. Khim., Leningr., 14, 446 (1941).


173. A. N. Nesmeyanov, A. E. Borisov, I. S. Savel'eva and M. A. Osipova, Izv. Akad. Nauk SSSR, Otdel. khim. Nauk. 1249 (1961).

174. O. A. Reutov and E. V. Uglova, ibid., 757 (1959). 175. G. Wittig and F. Bickelhaupt, Ber. dt. chem. Ges., 91, 883

(1958). 176. U.S. Pat. 2,366,683 (1945). 177. Canad. Pat. 424,236 (1944). 178. W. T. Mil ler, jun., and M. B. Freedman, J. Am. chem. Soc.,

85, 180 (1963). 179. G. Vitte and P. Mesnard, Bull. Soc. chim. Fr., 8, 350 (1941). 180. A. N. Nesmeyanov, A. E. Borisov and V. D. Vil'chevskaya,

Dokl. Akad. Nauk SSSR, 80, 383 (1953). 181. A. N. Nesmeyanov, A. E. Borisov and N. V. Novikova, Izv.

Akad. Nauk SSSR, Otdel. khim. Nauk, 1216 (1959). 182. F.R.Jensen and J. Mil ler, J. Am. chem. Soc., 86, 4736 (1964). 183. I. T . Eskin, Izv. Akad. Nauk SSSR, Otdel. khim. Nauk, 405

(1947). 184. German Pat. 249,729 (1911). 185. W. Beck and E. Schuierer, J. organometall. Chem., 3, 55

(1965). 186. E. P. Blanchard, jun., D. C. Blomstrom and H. E. Simmons,

ibid., 3, 97 (1965).

CHAPTER 14

Reactions of Organomercury Compounds

In comparison with other organometallics the organometallic compounds of mercury are very unreactive. Thus, the C-Hg bond does not react with the labile hydrogen of water, alcohols, or amines, and is only cleaved by the mineral acids, at rates which vary from one class of compounds to another. Being perfectly inert to oxygen-containing compounds, especially the carbonyl group, and to double bonds C=N, C=S, N=O1 and reacting very slowly with organic halides in the absence of initiators such as ultra-violet light or peroxides (the photochemical reactions of organomercuries are discussed later in this chapter), the organo-metallic derivatives of mercury find limited use as synthetic agents; they are applied mainly to the preparation of other organo-metallic compounds by their reaction with metals, inorganic halides and organometallic halides.

The aromatic derivatives are more susceptible to the action of acids, halogens, and other reagents breaking the C-Hg linkage than aliphatic ones. The fully substituted R2Hg are much more reactive than salts RHgX.

a) The Action of Oxygen

Organomercuries are stable to aerial oxygen and can be handled without any special precautions in this respect, although some of them (especially where the mercury atom is linked to secondary and tertiary aliphatic carbons) liberate metallic mercury on pro-longed standing, evidently by slow oxidation. This is the case with di-isopropylmercury [1] and dicyclohexylmercury [2]. Products of the oxidation of the organic part of the molecule (ketone and alcohol) are formed simultaneously.

Prolonged action of oxygen on di-isopropyl- and dicyclohexyl-[2a], di-t-amyl- [2b] and dibenzyimercury [2b] has been studied in certain solvents. Di-isopropylmercury shaken with oxygen in a sealed tube, in isopropanol solution, reacts as follows:

(Iso-C3H7)2Hg + O 2 - [(Iso-C3H7)2Hg-O2] - Hg + (CH3)2CO +(CH3 )2CHOH

337 KcJcrcnccs see page 426


(14C-Iabeled di-isopropylmercury was used to detect the isopropanol formed).

The same products, plus isopropylmercury chloride andisopropyl chloride, are formed when the reaction is carried out in c c i 4 (for 20 hours at 17-20°C); when the relative amount of di-isopropyl-mercury is increased and the reaction is carried out for 18 hours at 44° C, no metallic mercury or isopropanol are formed and the proportions of the other products are altered. The products of a reaction in chloroform are mercury, isopropylmercury chloride, acetone and isopropanol [1],

A solution of dicyclohexylmercury in isopropanol exposed to a current of dry oxygen for 40 hours at 60°C forms metallic mercury (64%), cyclohexanol and cyclohexanone; in chloroform (25 hours at 25°C) a little cyclohexane and cyclohexene appears in addition to the mercury (20%), cyclohexanone and cyclohexanol, as well as cyclohexylmercury chloride (in a yield of 70% on the starting dicyclohexylmercury); the same products (in smaller amounts) and 76% of cyclohexylmercury chloride [2] are obtained in CCI4 after 30 hours at room temperature. Analogous products are obtained from the oxidation of di-t-amylmercury in CCl4, CHCl3, benzene and cyclohexane. Dibenzylmercury gives benzaldehyde [2b].

The rates of the cleavage of aqueous isopropylmercury and t-butylmercury iodides with perchloric acid are considerably accelerated in the presence of oxygen [3] and the order of the reactions is changed; this is ascribed to the oxidizing action of oxygen on the organomercuries.

The presence of aerial oxygen accelerates the thermal decompo-sition of diphenylmercury in benzene into mercury and biphenyl, and the exchange of the phenyl radicals between diphenylmercury and labeled benzene [4]; the degree of the photodecomposition of diphenylmercury in benzene into mercury and biphenyl is also increased [4],

The action of ozone on the alkenyl organomercuries is described in this chapter and in Chapter 15.

b) The Action of Acids

E x c h a n g e o f M e r c u r y f o r H y d r o g e n a n d O t h e r R e a c t i o n s o f O r g a n o m e r c u r i e s w h i c h a r e n o t t h e P r o d u c t s o f

A d d i t i o n s o f M e r c u r i c S a l t s t o O l e f i n s

The C-Hg bond is easily cleaved by the hydrogen halides and is only slightly more stable to the oxo-acids. Fully substituted organo-mercuries are readily decomposed by mineral acids, and somewhat less readily by carboxylic acids [5-18, 21, 22];

R2Hg + HX - RHgX + RH

REACTIONS OF ORGANOMERCURY COMPOUNDS 339

Carboxylic acids generally have no effect on organomercury salts (for the reaction under vigorous conditions see below), whereas the mineral acids decompose them with particular ease at high tem-peratures:

RHgX + HX — RH + HgX2

The stability of organomercury compounds with respect to acids varies between wide limits. Acids very easily cleave off acetylene from acetylides of the type RC = CHgR, whereas the adducts of acetylene and mercuric chloride (ClCH=CHHgCl) are stable to a not too concentrated hydrochloric acid.

The adducts of HgCl2 and acetylenic ketones or acids undergo the usual exchange of HgX for hydrogen in the presence of acids (see Chapter 6).

Mercury occupying the site of the most labile hydrogen is split off most easily by acids. Aryl groups are always cleaved off more readily than alkyl. On the other hand, the perfluoroarylmercury compounds are unusually stable. Thus, bis-pentafluorophenyl-mercury can be recrystallized from conc. H2SO4 [44]. The same stability to acids is shown by the perfluoroalkyl derivatives. Among the aliphatic compounds of mercury, particular stability is shown by the mercarbides. The oxide of fully mercurated ethane converts into the chloride in cold hydrochloric acid, without losing the mercury [45]:

HOHg HgOH

/Hg)c -C^Hgv ^(C1Hg)3C-C(HgCl)3

\Hg Hg/

(ClHg)2CH-CH(HgCl)2, obtained by the action of dil. HCl on the cyanide which according to Hofmann has the composition (NCHg) HgC-CHg(HgCN), is converted by boiling conc. HCl into ClHgCH2-CH2HgCl and undergoes no further transformation [46].

Bleshinskii and Usubakunov [47] found that the final product of the acidolysis of mercarbide by HCl is not 1,1-dichloromercuri-ethane but methylmercury chloride, which they regard as one of the proofs that Hofmann's mercarbide is a derivative not of ethane but of methane.

bis-Perchlorovinylmercury does not react with 10% HCl [47a], but with hydrobromic acid and with a solution of HBr in chloroform gives mercuric bromide and trichloroethylene in 83% yield [47b].

Certain /3- and even a-mercurated dicarboxylic acids are difficult to decompose with acids; thus a-mercuri-di-/3-phenyl-anhydrohydracrylic acid

C6H5CH-CH-COOH I I O Hg I I

C6H5CH-CH-COOH

References see page 42(:i


decomposes only on prolonged boiling with concentrated HCl, CH3COOH, or HNO3 [47c]. Mercuri-bis- m-biphenyl, (W-C6H5C6H4)2

Hg, does not react with hydrochloric acid even on boiling. The ease of the decomposition of Alk2Hg by HCl [43] falls in the

ser ies Alk = I-C4Hg >iso-C4H9 > n-C4H9 and iso-C3H7 > n-C3H7. Many studies have been carried out on the kinetics of the acidoly-

sis of R2Hg by dilute acids: formic (R = C6H5 [10, 22]), acetic (R = n-C4H9 [17], S-C4H9 [17], CH2=CH-CH2 [53], C6H5C(CH3)2CH2 [17], 4-camphyl [21], C6H5 [10,17,22]), tetrachloroacetic (R = C6H5 [23]), hydrochloric (R = CH3 [24], C2H5 [23, 24, 25], n-C3H7 [24, 25], iso-C3H7 [24, 25], C6H5CH2 [18, 26], C6H5CH2CH2 [18], C6H5CH2CH2CH2

[18], CH2=CH [24, 27, 28], C6H5CH=CH [28], c is -and trans-ClCH= CH [27, 28], cis- and ^ans-CH3CH=CH [27, 28], cis- and trans-CH3OCOC(CH3)=C(CH3) [27, 28], cis- and ^ans-C6H5CH = C(C6H5) [28], CIS-CH3OCOC(C6H5)=C(C6H5) [27], ZC6H4C = C [23] (where Z = H, 3-CH3, 2,4-(CH3)2, 2,6-(CH3)2, 4-t-C4H9, 4-F , 3-C1, 4-C1), cyclo-C3H5 [24], C6H5 [18, 24, 25, 27-29], O-CH3C6H4 [18, 27, 28], m-CH3C6H4 [18, 27, 28], P-CH3C6H4 [18, 24, 27, 28], ^-S-C4H9CgH4

[18], O-CH3OC6H4 [27, 28], P-CH3OC6H4 [25, 27, 28], p-FC6H4 [27, 28], O-ClC6H4 [27], Ot-CIC6H4 [27], P-ClC6H4 [25, 27], a-C10H? [27, 28], /S-Ci0H7 [23], n-C4H9C = C [23], Ot-NO2C6H4 [25], P-C6H5C6H4

[25], o-phenylene [23]), hydrobromic (R = C6H5 [23, 29]),perchloric (R = n-C4H9 [17], S-C4H9 [17], C6H5C(CH3)2CH2 [17], C6H5 [10, 17, 22, 23]), p-toluenesulfonic (R = C6H5 [23]). See also below.

The acidolysis reaction is of second order (S E 2 mechanism), though an apparent f i rst order is observed in the reactions with acetic and formic acids when the latteraretaken in a large excess.

The relative ease of the cleavage of a radical by acid is deter-mined by its position in an electronegativity series derived by Kharasch [30-36] on the basis of the reaction

RHgR' + HCl - RHgCl + R'H

where R is regarded as the more electronegative radical. R' forms the following series: CN > P-C6H4OCH3 > O-C6H4OCH3 > a-C10H7> 0-C6H4CH3 > P-C6H4CH3 > Ot-C6H4CH3 > C6H5 > P-C6H4Cl > O-C6H4Cl > m-C6H4Cl >CH3> C2H5 > C3H7 > C4H9 > C6H5CH2 > C(CH3)3; a-thienyl and a - furyl , and also p-hydroxyphenyl and p-aminophenyl are at the very beginning of this sequence. This series is discussed in [37-39].

Winstein and Tray lor , Dessy, Nesmeyanov and Borisov, and other authors inserted further radicals into Kharasch's ser ies by studying the kinetics of the reactions of hydrochloric acid with Alk2Hg [17, 23, 24, 28b], with Ar2Hg [18, 23-25, 27, 28], with symmetric quasi-complexes and other alkenyl compounds of mercury [27, 28], and with compounds of the type (XC6H4C = C)2Hg [23]. Some of these additions are listed below: P-CH3OC6H4 > P-C6 H5C6H4 > C6H5 > p-FC6H4 > P-ClC6H4 > Ot-NO2C6H4 [25], P-CH3C6H4 > O-CH3C6H4 > Ot-CH3CgH4 [18], 7~C6H5C3H6> C6H5CH2CH2>C6H5CH2 [18].


The position of branched aliphatic groups in the electronegativity series (based on the decomposition of RHgR' by alcoholic HCl) is seen from the following sequence [28a]:

C6H5 > CH3 > C2H5 > n -C3H7 >

^ Tn-C4H9; (CH3)3CCH2CH2 ^ In-C6Hj3; (CH3)3CCH2CH2CH2 > (CH3)3CCH (CH3)

CH3

C6H5CH2X(CH3)3C; (CH3)3CCH2]

The groups shown in brackets are indistinguishable by this method, i .e., give mixtures of R'HgCl and RHgCl.

On the basis of the rates of the acidolysis of R2Hg by HCl in 90% aqueous dioxan, the following series has been obtained for the R groups: 1,3,S-(CH3)3C6H2 > Srons-CH3CH=CH > P-C2H5OC6H4 > cis-CH3CH=CH > ^-CH3OC6H4 > C6H5CH=CH > âns-CH3OCOC(CH3)= C(CH3) > Cis-CH3OCOC(CH3)=C(CH3) > a-thienyl > o-CH >C 6H 4> p-C2H5C6H4 > P-CH3C6H4 > cis -C6H5CH=C(C6H5) > O-CH3OC6H4 > a-C ,„ H7 > M-CH3C6H4 > CH2=CH > CgH5 > p-FCgH4 > W-CH3OC6H4 > trans-C6H5CH=C(C6H5) > P-ClC6H4 > P-BrC6H4 > W-FC6H4 > W-ClC6H4 > CH3

OCOC(C6H5)C(C6H5) > O-CH3OCOC6H4 > âns-ClCH=CH > C2H5 > p -CH3OOCC6H4 > Cis-ClCH=CH > O-CH3OOCCgH4 > n-C4H9 > O-ClC6H4 > C6H5CH2.

This shows that the rate of the acidolysis of Ar2Hg falls in the order p-CH3OC6H4»O-CH3OC6H4 > CgH5 > W-CH3OCgH4; O-CH3CgH4 > P-CH3C6H4 > W-CH3C6H4 [28]; P-C2H5C6H4 > P-CH3CgH4, depending on the nature of the substituents and on their position in the benzene ring [28].

Accumulation of methyl groups in 0- and p-positions considerably accelerates the acidolysis with hydrochloric acid, so that dimesityl-mercury reacts at the highest rate. As usual, the ring is inactivated with respect to electrophilic attack by halogens in 0-, w- and im-positions, and by acetoxy and carbomethoxy groups in the 0- and p-positions. /3-Chlorovinyl compounds also react slower than divinylmercury.

For the halogenated phenyl groups, the rate of the reaction de-creases in the order P-ClC6H4 > W-ClC 6Hô-ClC 6Ht and p-FC6H4 > P-ClC6H4 > P-BrC6H4 (the same trend occurs in the w-derivatives).

On the basis of the rate of formation of RH in the reactions of RHgCHCl2 with alcoholic HCl, the R groups fall into the series CC13>C6H5>CHC12 [39a].

Saturated aliphatic compounds react considerably more slowly than the majority of aromatics and unsaturated aliphatics. Apart f rom &>-mercuri-bis-stilbene, the irons-isomers of unsaturated organomercury derivatives react faster than the cis - isomers. The highest reactionrate studied was observed with dially lmercury [28b].

Rcfcrcnccs sec page 426


The rate of the decomposition of compounds RHgR by hydrochloric acid in a mixture of dimethyl sulfoxide and dioxane depends on the hybridization of the attacked carbon atom. The rate increases in the order sp3< sp2 < sp, in the ratios of approximately 1:100:1000 [23].

Following the decreasing rate constants (pseudofirst-order equation) of the reactions OFR2Hgwithhydrogenchloride in aqueous tetrahydrofuran (15% H2O), the R groups may also be arranged in the ser ies CH2=CH > CF2=CF > C2H5 [40]. The analogous decomposi-tions of perfluorovinylvinylmercury, perfluorovinylethylmercury and perfluorovinylphenylmercury result in trifluoroethylene [40].

The series obtained by Dessy et al. [24] (by reacting R2Hg with HCl in a 10:1 mixture of dimethyl sulfoxide and dioxan): cyclo-C3H5 > H2C=CH > C e H 5 »C 2 H 5 > iso-C3H7 > n-C3H7 > CH3, does not quite agree with the series obtained by Kharasch et al. [28].

Dessy and his associates [23, 24a] proposed a four-center mecha-nism for the attack on an organomercury compound by an acid:

R - H g - R R — H g — R R H

f = T - X j — + H - C l H - C l RHgCl

involving an electrophilic molecular attack or an attack by an HCl ion-pair. This is confirmed by the fact that electron-attracting substituents in aromatic organomercuries retard the decomposition by hydrogen chloride, whereas the electron-repell ing groups wil l accelerate it.

In view of the similarity between the values of the activation energies and activation entropies for the CleavageofCeH5-Hg bonds during the reactions of HCl with C6H5HgC2H5 and with (C6H5)2Hg, Dessy [23] further believes that the splitting of RHgR' by hydro-chloric acid is a measure of the availability of electrons at the attacked carbon atom and not of the electronegativity of the group which is split off. However, there is some uncertainty about the possibility of a transfer of electric effects via a mercury atom [23, 24], The role of the anion of the acid HHal in the stage deter-mining the rate of acidolysis appears in the considerable changes in Esand AS*on passing f rom HCl to HBr [23].

The linear dependence of log K on the acidity functions H of various solvent systems indicates an attack by ion pairs; the de-viations shown by the HCl-dioxan system are due to attack by HCl molecules. No clear dependence exists between the dielectric con-stant of the solvent and the rate of the acidolysis.

Application of Hammett's equation to the acidolysis of Ar2Hg by HCl has been described [23, 25, 28], in particular for (ZC6H4C = C)2

Hg [23]. Linear correlations have been observed [28] in the acidolysis of

m - and p-substituted aromatic organomercury compounds between


log K and Hammett's a constant, <r+, and (a+a+)/2. The best co r -relation is that with ((j + o+)/2 [23, 25, 28]. Thus, although the attack of Ar2Hg by HCl is on the whole similar to an electrophilic substitu-tion in the benzene nucleus (correlation with a+ ) , there is a slight deviation (in the direction of correlation with a ) . Taft 's equation with polar substituent constants a+ applies to the unsaturated o r -ganomercuries (for the radical linked to the mercury atom) [28a]. The observed [28b] correlation of log K/Kq with Hammett's ov. a£ and (a+a+)/2 for the substituents R of unsaturated organomercury compounds indicates a greater conjugation of the /3-substituents of an unsaturated system with the reaction center in comparison with an aromatic system. The values of Hammett's p for the arylacetyl-ides (ZC6H4C = C)2Hg show that the latter's reaction with hydro-chloric acid is less sensitive to substituents in the ring in com-parison with aromatic compounds [23].

The acidolyses of AlkHgI with HClO4 and H2SO4 are of pseudo-f irst order owing to the excess of the acids [41, 42]; on the basis of their relative reactivities in this reaction, the following sequence of radicals has been obtained: cyclo-C3H5»CH3 >C2H5 > n-C3H7 > iso-C3H7>n-C6Hu>t-C4H9 [42].

Fo rA lk = iso-C3H7 and t-C4H9, the kinetics depend on the presence of oxygen [ 3].

The action of DCl on tetrachloromercurithiophene leads to deuterothiophene [48], and the action of TCl on the same compound (also containing labeled sulfur) gives tetratritiated thiophene [49],

The acidolyses of di-L- (- ) -s-butylmercury and the d i - c i s - and di-trans -4-methylcyclohexylmercury by deuteroacids occur accor-ding to the scheme

R2Hg + DX • RD + RHgX

Partial retention of the configuration of the R group is found in the f i rst case (action of CH3COOD and DCl in dioxan), and a high degree of retention (cleavage by DCl in dioxan) in the last two cases [50]. Other acids (CH3COOD, D2SO4) in dioxan give predominantly the trans - isomers of the RD [50].

Descriptions have been published of the action OFH2SO4 and other sulfonating agents on the mercury derivatives of anthraquinone [59-62] and also of the action of HNO3 containing nitrogen oxides on organomercury derivatives.

Thiophenols react with diphenylmercury and with RHgX (R = Ar and Alk) [63, 64] at 130°C like acids, forming mercuric thiophen-oxides or metallic mercury. Whenboiledwiththiophenols in benzene for 6 hours, the Ar2Hg give thiophenoxides and the ArHgAr ' split off radicals in accordance with Kharasch's electronegativity series [64].

The action of phosphoric acid on bis-ethylmercuriacetylene leads to acid monoethylmercury and di(ethylmercury)phosphates [65].

According to Koton[16], at high temperatures (6-9 hours at 150°C)



carboxylic acid esters react with diphenylmercury in the following manner:

(C0H5)2Hg + R C O O R ' - RCO2HgC6H5 + C6H5R'

Tributyl borate does not react with diphenylmercury at 140°C [66] or with ArHgOH and ArHgOCOCH3 at 150°C [67].

Dimethylaniline hydrochloride reacts with Ar2Hg at 130-150°C like free hydrochloric acid, giving rise to ArHand HgCl2 [68]. With Ar2Hg in alcohol or benzene at IOO0C trimethylamine hydrochloride gives ArHgCl, and at 130°C in water or without a solvent (sealed tube) it decomposes the Ar2Hg and ArHgCl to Hg and HgCl2 [69].

Acid amides [70] and imides [70-72] react with Ar2Hg like the acids: the amide or imide protons combine with the radical and the ArHg residue forms an ArHgN- derivative.

Phenyltrihalogenomethylmercury reacts in two ways with hydro-gen chloride (in toluene, at 80°C):

i—» C6H6 + CCl2BrHgCl C6H5HgCCl2Br + HCl —

U C6H5HgBr + CHCl3

C6H5HgCBr3 does not form bromoform with hydrogen chloride, and the main reaction product is benzene [50a]. C6H5HgCCl3 and methano-lic HCl give chloroform and C6H5HgCl [538].

In the same way, esters RCOOCHCl2 and mixed dichloromethyl ethers ROCHCl2, respectively, are formed with carboxylic acids (in benzene at 60-80°C) and alcohols (inethylbenzene at 80-85°C) [50a].

The main product of the reaction of benzoyl peroxide with (C2H5)2

Hg and with (C6H5)2Hg in benzene is RHg benzoate [72a]. Reutov et al [73a, 73b] have found the first examples of a proto-

demercuration reaction, proceeding by an S^l mechanism at saturated, olefinic and aromatic carbon atoms.

R e a c t i o n s o f O r g a n o m e r c u r y C o m p o u n d s w i t h A c i d s L e a d i n g t o t h e S e p a r a t i o n o f

M e t a l l i c M e r c u r y ( D e m e r c u r a t i o n s )

Organomercuries R2Hg and salts RHgX heated to high tempera-tures with acetic acid in a sealed tube decompose completely with separation of metallic mercury [51]. Thus, dimethylmercury gives (250°C) metallic mercury, ethylene, methane and hydrogen [51]; diethylmercury (several hours at 160-190°C) mercury, ethyl acetate, ethylene, ethane and hydrogen [51]; di-isoamylmercury (16 hours at 190-200°C) mercury, amyl acetate and isopentane [51]; benzylmercury acetate (7 hours at 170°C) mercury and benzyl acetate; dibenzylmercury (2 hours at 170°C [51, 52]), apart from the last two products, also toluene andbibenzyl; and phenylmercury


acetate and diphenylmercury (220-230°C) give benzene, biphenyl and tar [51] (but see also [53]).

Alkenylmercury acetates heated above IOO0C with acetic acid decompose with the formation of alkenyl acetates and f ree mercury [53]. Methyl-, phenyl- and cyclopropylmercury acetates do not undergo a decomposition under these conditions [53].

Far-reaching solvolysis can also occur at moderate temperatures in the acid decompositions of many organomercury salts, in which the salts decompose with separation of metallic mercury and with the formation of products resulting f rom the interaction of the organic residue with the acid residue, e.g. with the formation of an ester of the acid used in the reaction; olefins are formed in several cases:

RHgZ + HX - HZ + Hg + RX + olef in

This reaction has been observed as a side process in the cleavage of R2Hg and HClO4 in acetic acid (R = neophyl [17]) and by deutero-acetic and other deutero-acids (R = L- ( - ) -s -buty l and 4-methyl-cyclohexyl [50]).

On moderate heating with carboxylic acids in alcohol, benzene, toluene, heptane, or in the absence of solvent, divinylmercury gives r ise to f ree mercury and the corresponding vinyl esters via the intermediates RCOOHgCH=CH2 [54].

Similar reactions are observed between divinylmercury and phenols (heating on a water bath for 1-3 hours), thiophenols (instantaneous exothermic reaction at room temperature) and alkyl thiols (3 hours at 115°C): the products are metallic mercury and vinyl aryl ethers, vinyl aryl sulfides and vinyl alkyl sulfides [54]. Other dialkenylmercuries react with thiophenols in the same way [53].

The interactions of p-toluenesulfinic acid with divinylmercury [54] (in ethanol, on a water bath) and with dicyclopropylmercury [64a] yield the same products: ethylene, vinyl p-tolyl sulfone and metallic mercury, whereas with carboxylic acids divinylmercury gives the corresponding vinyl esters [54] (see above).

Kinetic study [19] of the cleavage of cyclohexylmercury acetate with acetic acid at 25°C, either with or without HClO4, showed that this reaction is of f i rst order. Similar studies of the solvoly-sis of alkylmercury perchlorates (alkyl = CH3, C2H5, iso-C3H7, n-C4H9, S-C4H9, t-C4H9 [20]) and of cyclohexylmercury perchlorate and other salts [19] in water and acetic acid suggest that a carbo-nium ion is involved in the transition state [19, 20]:

RHgX R H g + + X -

RHg + R + + Hg

R + — Reaction products



The rates OftheformolysisandacetolysisofC2H5HgClO4 increase sharply when aryl groups (phenyl, m- and p-tolyl), and particularly a phenyl group and two methyl groups simultaneously are introduced into position 2 [54a]. Hammett's equation has been applied to this reaction [54a].

Phenylmercury salts, especially the perchlorate and tosylate in acetic acid and even in toluene, also undergo solvolysis of this type (to the phenylmercury cation) with perchloric acid; this is indicated by the formation of the ferricinium cation when the reaction is carried out in the presence of ferrocene [54b], The solvolysis of crotylmercury salts by acids is very much faster than the solvolysis of saturated organomercury compounds and is accompanied by allyl rearrangement of the radical [54c]. Thus, under the action of HCl in ethyl acetate, or of HClO4 in acetic acid, crotylmercury halides and crotylmercury acetate (only with HCl) form an olefin, but-l-ene. Analogously, cinnamylmercury acetate and hydrochloric acid yield allylbenzene [54c]. The solvoly-sis of crotylmercury acetate by acetic acid at 500C affords almost exclusively s-butenyl acetate; in the presence of HClO4, 71% of the above product and 29% of a mixture of trans - and cis -crotyl acetates:

H AcOH CH3CHCH=CH2 CH3CH=CHCH2OAc trans cis

CH3 C so°c OAc \ / \ >99.5% 0.5%

C CH2 ArOH OR0C I I ' 25 , 71% 28.5% 0.5% H HgOAc HCio1

First order is observed in the demercurations of benzy lmercury, /3-(p-methoxyphenyl)ethylmercury and nortricyclylmercury ace-tates [55a] in aqueous acetic acid (the last-named compound also in acetic anhydride) in the presence of HClO4 which proceed with the formation of metallic mercury and the corresponding alkyl acetate. The reaction of benzylmercury acetate with mercuric acetate under the same conditions, proceeding according to the scheme [55]:

ArCH2HgAc + HgAc2 ^ ArCH2Ae + Hg2Ae2

is kinetically of second order; see also below. The first-order rate constants of the demercurations of exo-

norbornylmercury, cyclohexylmercury and endo-norbornylmercury acetates by HClO4 in acetic acid are in the ratios of 5xlOs:43:l [55a, 55b].

The interaction (in boiling benzene) between diphenylmercury and tributylphosphine in the presence of acids (carboxylic acids, phosphoric monoesters, p-toluenesulfonic acid) yields the acid anhydride, tributylphosphine oxide and metallic mercury; for


example [55c]:

(C6H5)2 Hg + (Ii-C4H9)3 P + 2RCOOH - Hg + (RCO)2 O + (Ii-C4H8)3 PO + C6H6

The reaction of phenylmercury acetate with tributylphosphine in the presence of an acid proceeds analogously, with intermediate formation of diphenylmercury [55c]:

2C6H5HgOCOCH3 + 2 (n-C4H9)3 P + 2RC00H - 2Hg + (CH3CO)2 O + (RCO)2 O + 2 (Ii-C4H9)3 PO 4- 2C6H6

Equimolar proportions of diphenylmercury, tributylphosphine, benzoic acid and ethanol (boiling for 8 hours) give a 76% yield of ethyl benzoate, metallic mercury (85%) and tributylphosphine oxide (85%). If aniline is used in place of the alcohol, the products contain a good yield of the anilide of the acid used in the reaction [55c].

A c t i o n s o f A c i d s o n P r o d u c t s o f t h e A d d i t i o n o f M e r c u r i c S a l t s t o O l e f i n s a n d T h e i r D e r i v a t i v e s

Another type of reaction is observed between acids and the products obtained from the addition of olefins and their derivatives to basic mercury salts; the olefin is regenerated (desoxymercura-tion), for example:

HOCH2CH2HgX + HX » C2H4 + H2O + HgX2

This reaction proceeds easily in the cold with the mineral acids and is characteristic for substances of this type [76] (see also Chapter 6). According to Sand [77], the acid stability of several such compounds can be somewhat increased by benzoylation of the hydroxyl group, but another type of solvolysis then takes place:

2RCOOCH2CH2Hg I - RCOO- + CH2=CH2 + HgI2 + RCOOCH2CH2Hg+

This occurs readily with acetic acid and also in a neutral medium in aqueous alcohol or aqueous dioxan [78],

Kinetics have been studied of the HCl- decompositions of adducts obtained from mercuric salts and ethylene [79, 80] and cis- and trans -stilbenes [81]; decompositions of the cyclohexene adduct with HCl, trifluoroacetic acid [81, 82] and HClO4 [83, 86]; HClO4-decompositions of the adducts of mercuric salts with ethylene [84-86] and tetradeuteroethylene [84], with propylene [87], with cyclopentene [85, 86], bicyclo-(2,2,l)-heptene [85, 86], acryloni-tri le [87a], styrene [88] and with styrenes deuterated in position 1 or 2 [88]; and of decompositions of the product of addition to carbon monoxide [89a] with HCl, trifluoroacetic and acetic acids.



The geometric configurations of the alkenes are retained during their regeneration by the action of acids on the products of the addition of mercuric salts to olefins and their derivatives, as can be seen on the examples of cis - and trans -stilbene [89].

The elements XHg and OR are cleaved off by acids more easily from the trans -adducts to cycloalkenes than from their cis-isomers, and more easily from the products of additions in water (^-hydroxy-alkylmercury salts) than from the products of additions in alcohols (/3-alkoxyalkylmercury salts) [85a].

With rare exceptions, carboxylic acids do not react with such adducts at moderate temper atures. The decomposition of the adducts from mercuric salts and CO by acetic and trifluoroacetic acids in dimethyl sulfoxide is accelerated by many substances, accelerators combining with the mercury salt [89a], These substances can be arranged into the following sequence of decreasing accelerating power [89a]:

C0H5SH > I" > Br- > Cl" > (C6HS)3 PO > (C6H5)8 P, C6H5OH

For the mechanism of desoxymercuration under the action of acids of the products obtained by addition of mercuric salts to double bonds see Chapter 6 and also, for example, [90, 91].

The decompositions at 40°C in the presence of strong acids (H2SO4, H3PO4, HClO4, ArSO3H) of organomercury salts (without their separation) forming in the reactions between aromatic compounds and the adducts of mercuric acetate and olefins (ethyl-ene [56], propylene, but-2-ene, styrene, cyclohexene [57]) are accompanied by demercuration with separation of metallic mercury (and sometimes also a mercurous salt) and formation of /3-aryl-alkyl acetates and /3-diarylalkanes. The reactions are of second order [57a].

Organomercury compounds forming in the reactions of aceto-acetic ester with the adducts of mercuric salts and olefins (ethylene, propylene, styrene) demercurate on moderate heating in acetic acid in the presence of boron trifluoride/diethyl ether, with the formation of metallic mercury and a-(2-acetoalkyl)acetoacetic ester [58], e.g.,

B F 5 ( C s H 1 ) 2 O CH3COCH (CH2CH2HgOCOCH3) COOC2H5

C H 1 C O O H

->• Hg + CH3COCH (CH2CH2COCHS) COOC2H5

A cyclization product (a furan derivative) has been isolated in the case of styrene.

c) The Action of Alkalis

As a rule, alkalis do not cleave the C-Hg bond. Exceptions are the formation of NaOCfiH1HgOH from di-o -hydroxyphenylmercury under the action of alkali [92], and also the full decompositions,


with separation of metallic mercury, of ethyl mercuri-bis-chloro-mercuriacetate [93] and bromomethylmercury bromide [94] on heating with weak solutions of alkali.

In the presence of alkali, the product of the reaction of potassium monochloroacetate with HgO (to which Hofmann ascribed a structure of a complex of potassium chloride with a chloromercuriacetic salt) yields mercuric oxide and a glycolic acid salt [95].

The product obtained from the addition of mercuric acetate to chloroketene acetal (ethyl ester of di-(acetoxymercuri)chloroacetic acid) is decomposed by 20% aqueous KOH [96].

Alkaline treatment results in the splitting off of mercuric salts added to the double bond in coumarinderivatives [97, 98] (cf. Chap-ter 6), but the usual products of the addition of mercuric salts to unsaturated compounds (including coumarin [62, 99]) are stable to alkalis. The action of bases (and alkalis) on the /3-chlorovinyl compounds of mercury has already been described in Chapter 6.

d) The Action of Hydrogen Sulfide and Alkali Metal Sulfides

With rare exceptions, full organomercuries do not react with the above compounds. Organomercury salts usually give colorless sulfides (RHg)2S, which often tend to split off HgS on heating or storage (especially in the aromatic series and in the case of the most electronegative radicals).

(RHg)2S-* R 2 H g + HgS

This reaction is sometimes used for the symmetrization of organo-mercury salts (Chapter 13).

Mercury is relatively easily replaced by hydrogen as a result of the action of H2S on pentafluorophenylmercury compounds [99a].

The products of the addition of mercuric salts to olefins also give, as a rule, colorless sulfides, which decompose fairly rapidly. In contrast to their reaction with acids, the adducts of mercuric salts and a)(S-unsaturated acids under the action of alkali metal sulfides do not regenerate the unsaturated compounds but replace the Hg by H, giving good yields of /3-hydroxy acids [100], for

C6H5CH-CH-COOH + Na2S-* C6H5CH-CH2-COOH I l I OH HgCl OH

In certain cases the alkali metal sulfides, including ammonium sulfide, cleave off the mercury atom from organomercury com-pounds. Thus, mercury splits off easily from salts of mercurated acetic and propionic acids under the action of (NH4)2S [101, 102].



e )The Action of Certain Oxidizing Agents, in Particular Mercuric Salts

Certain organomercury salts, especially those in which the Hg is linked to a secondary carbon, are oxidized by mercuric salts at moderate temperatures, reducing the latter to mercurous com-pounds or to metallic mercury and forming (depending on the reaction medium) alcohols and products of their oxidation in water, and ethers in alcohols.

Nitric esters are also formed in the oxidation of RHgNO3 with mercuric nitrate. In this section we shall ignore the oxidations in which only intermediate formation of organomercury salts can be assumed.

Mercuric nitrate has been used for the (room temperature) oxidation of methanolic benzylmercury [103] and cyclohexylmer-cury nitrates [104], and of aqueous cyclohexylmercury nitrate [104]; the oxidation of cyclohexylmercury nitrate in aqueous methanol with pernitric acid affords the same products as the oxidation with mercuric nitrate in methanol [104].

The oxidation of organomercury acetates with mercuric salts is slower than the corresponding oxidation of organomercury nitrates, but the products are of the same type [104]. Hg + and cyclohexanone were obtained during the oxidation of cyclohexyl-mercury acetate with peracetic acid in methanol (7 hours of boiling in a mixture of alcohol and chloroform); the ketone is due to an oxidation of the initially formed cyclohexanol by the peracetic acid and Hg2+ .

The oxidations of organomercury nitrates and acetates are of second order, and Robson and Wright [104] believe them to be homolytic.

H g + and the corresponding ether were obtained in the oxidation of l-phenyl-2-methoxy-2-methylpropylmercury acetate with mer-curic acetate in the presence of boron trifluoridediethyl ether (in c h 3 o h , after 24 hours at 50°C). The oxidation of 4-hydroxycyclo-hexylmercury acetate with Fenton's reagent in water yielded formyl-cyclopentane and 2-chloromercuricyclohexanone (after addition of NaCl [104]).

Cyclohexylmercury salts (trifluoromethylacetate and nitrate without a catalyst and acetate only in the presence of BF3-ether), 2-propylmercury acetate and 3-amylmercury acetate undergo in methanolic solution and at a moderate temperature (50°C) hetero-polar monomolecular autoxidation with the formation of metallic mercury and an olefin [105]. Olefin formation occurs also in the case of 1-methyl-l-cyclohexylmercury acetate [105].

The action exerted by ozone on alkenyl organomercuries under the usual conditions under which ozone reacts on organic compounds leads both to ozonization of the organic part of the molecule and to fission of the C-Hg bond [106] (see also Chapter 15).


f ) The Action of Metal Carbonyls

The action of pentacarbonyliron with heating on RHgX and R2Hg gives HgFe (CO)4 [107]. Mn(CO)5H and RHgOH form [Mn(CO)5]2Hg [108].

g ) The Action of Halogens

Free halogens decompose organomercury compounds in two stages:

R2Hg + X2 RHgX + RX (1)

RHgX + X2 RX + HgX2 (2)

The R2Hg react more energetically than the RHgX. Dimethylmercury and diethylmercury ignite spontaneously when

added in drops to dry chlorine, and react with bromine and iodine according to reaction (1) without ignition. The reaction proceeds more mildly in a solvent, and under these conditions it is used widely to establish the position of the mercury in the molecule (generally Br 2 or I2 in aq. KBr or KI, in alcohol, CS2, CHCl3, CCl4, CH3COOH) and to obtain halogen derivatives which are otherwise difficult to prepare.

Dioxan dibromide may be used as a mildly acting agent [114]. Studies have been carried out on the kinetics and the stereo-

chemistry of the reaction of S-C4H9HgBr with Br 2 in c c i 4 [109a], and also on the kinetics of the reaction

R 2 H g + I 2 - * R H g l + RI

in carbon tetrachloride [109]. The activation energy of this reaction increases in the order P-CH3OC6H4 < O-CHpC6H4 < /S-C10H7 < a-Ci0H7 < P-CH3C6H4 < O-CH3C6H5 < C6H5 < P-C2H5O2CC6H4 < p-FC6H4 < O-C4H3S < P-ClC6H4 < CH3 < Q-C2H5OOCC2H4 < C2H5 <n-C4H9<n-C6H11

< iso-CsHji < iso-C3H7 <C6H5CH2, which essentially coincides with Kharasch's series.

C6H5HgSC6H5 and bromine give C6H5HgBr and (C6H5)2S [291]. The reactions of a-bromomercuriphenylacetic ester and benzyl-

mercury bromide with iodine are of second order in the presence of CdI2 (in aqueous dioxan); in the absence of CdI2 these reactions are of the f irst order and proceed by a radical mechanism [110]. Second order has also been observed for the electrophilic reactions of trans - and cis -/3-chlorovinylmercury chlorides with iodine in the presence of CdI2 in aqueous dioxan [111a], methanol [111b] and dimethylformamide [111c], proceeding with retention of the con-figuration of the radical [111c], In the absence of iodine ions in non-polar solvents (benzene, CCl4), these reactions are homolytic



and the geometrical configuration is not preserved; in highly ion-izing solvents such as dimethyl sulfoxide the reactions follow first order, which the authors interpret as an SeI mechanism at the olefinic carbon, and the configuration is retained [ l l l d ] .

In the presence of an excess of CdI2 (in dimethylformamide, methanol and ethanol [112a], or in 70% aqueous dioxan [112a, 112b]), the reaction of benzylmercury chloride with iodine is of over-all second order; in CCl4 and under a 150-W lamp the reaction is of f irst order with respect to the iodine and of zero order with respect to the mercury compound [112c, I l l b ] . The kinetics in dimethyl-formamide are more complex: the reaction does not proceed in the dark and without heating [112c]. The reaction between benzyl-mercury chloride and bromine (and NH4Br) is of second order in dimethylformamide, methanol, and 70% aqueous dioxan [113a]. The kinetics of the reaction of benzylmercury chloride with bromine (in CCl4 it is of f irst order with respect to bromine and of zero order with respect to the benzylmercury chloride) shows that it proceeds via free radicals [113b]. The order increases to second in the presence of oxygen-containing substances. The reaction rate depends upon the solvent and decreases in the sequence CH3OH > C2H5OH > (C2H5)2O >iso-C3H7OH>t-C4H9OH [113b]. Ithas been sug-gested that the bromine is polarized by forming complexes with these compounds and the reaction with benzylmercury chloride occurs as a bimolecular electrophilic substitution [113b].

The action of a benzene solution of bromine [114] on trans-a -

mercuri-bis-stilbene leads to a replacement of the mercury atom by bromine; if the halogen is in the form of dioxan dibromide (in dioxan), it is possible to isolate the intermediate trans - a -bromo-mercuristilbene. The cis-isomer both of R2Hg and RHgBr give directly RBr at room temperature with dioxane dibromide [114]. Stereochemically speaking, the reaction proceeds clearly, with the formation of only one geometrical isomer:

CflHs

H C6H5

\ c = c ^ J Hg

QH s

H

/ Br,

H C6H5 CjHgO2- Brg \ c = c /

C4H1O2 / \ 2 C6M5

C6H5

C8H5 Br

HgBr

C6H5 C6H5

>c=c< \ H /:

Hg

CflH5

CflH5 C6H5

\ c - c / \ BrHg

C4H1O2-Br,

C6H5

Br H

H

C4H8O2- Br2


The action of halogens on the adducts of mercuric salts and unsaturated compounds has already been described in Chapter 6.

Cis- and trans -4-methylcyclohexylmercury bromides [115] and the optically active 2-bromomercuributane [116a] eliminate the HgBr group in the presence of bromine under conditions that favor a radical mechanism (in CCI4 or CS2, in the case of the 2-bromomercuributane in CS2) with full racemization of the resulting RBr. The configuration is partly retained in nonpolar solvents con-taining a little alcohol. In polar media (pyridine, 0°C), the HgBr is eliminated from the first two compounds with retention of the configuration, whereas in the case of 2-bromomercuributane, in contrast to earlier data [116b], the configuration is partly lost. A stereospecific course of the reaction with the last-mentioned compound is also promoted by a low temperature (-65°C), and with the first two compounds by carrying out the reaction not in nitrogen but in air.

The action of iodine in aqueous chloroform on 2,6-bis-(acetoxy-mercurimethyl)-p-oxathiane gives cis-and trans -di-iodides [117]:

S

c i s - , m.p. 73°C trans-, m.p. 64-68°C

Dimethyl-2,6-bis-(acetoxymercurimethyl)- p-oxathiane reacted with iodine under the same conditions also gives rise to both isomeric RI [117], The corresponding sulfones give only the higher-melting cis -product [117].

The action of bromine [118, 119] on pure diastereomers of 2-bromomercuri-3-phenylpropionic acids gives a mixture of two diastereomeric 2-bromo-3-phenylpropionic acids [118]. The rela-tive proportions of the diastereomers in these mixtures depend on the temperature, the solvent and other experimental conditions [118]. Neopentylmercury chloride is converted by halogens into the cor-responding bromide or iodide without any change in the configuration [120], On the basis of the kinetics of the reaction of 4-camphylmer-cury iodide with iodine it has been shown that, depending on the experimental conditions, the mechanism may be homolytic or heterolytic [21]. The tri-iodide ion decomposes 4-camphylmercury and n-butylmercury iodides at the same rate [21].

The occurrence of an electrophilic replacement of HgBr in cycloalkylmercury bromides by bromine in pyridine with full



retention of the configuration makes it possible to establish the configuration of RHgBr on the basis of the known configuration of RBr. This method has been used to establish the configurations of cis-and tfrons-4-methylcyclohexylmercury bromides [121], the product of the hydroxymercuration of dimethyl exo-cis-3,6-endo-oxo- A4-tetrahydrophthalate and certain other acids [122a],

The replacement of mercury by Br in the dimethyl esters of 4-hydroxy- (or 4-acetoxy-) -5-chloromercuri-3,6-en^o-oxohexa-hydrophthalic acid by the action of bromine [122b] in polar solvents (pyridine, glacial acetic acid) leads to cis -bromohydrin, and in nonpolar solvents (CCl4, CHCl3) to a mixture of cis - and trans -bromohydrins with a predominance of the cis-isomer. The reaction of the 4-hydroxy derivative with bromine in glacial acetic acid is accompanied by acetylation of the hydroxyl:

hVZS7C02CH3B, HO' C 1 h S S s Z ^ J Z C O 2 C H 3 ^ 1 7 - B r

C H 3 C O 2 H B r ,

O CH3CO2sJX^yCO2Ch3

B r ^ / ^ / ^ j J c O j C H a

The cis- and trans -RBr are formed in various proportions as a result of the action of bromine in CCl4, CH3OH, CHCl3 and pyridine on methyl-2-chloromercuri-2-desoxy-3,4,6-tri-0-acetyl-/3,D-glu-coside [122c]:

AcO

C H 2 O A c

O C H 3 A c O Br2

HgCI

C H 2 O A c

+

H Br

C H 2 O A c

O C H 3 A c O OCH 3

K O A e B r / H \ | | / H

H H

Only one isomer is formed in the reaction between bromine and the acetoxymercuri derivative.

If the reaction of RHgCl with iodine is carried out over a long time, HgCl can be replaced not only by iodine but also by chlorine owing to an interaction between the forming HgCl2 and RI [123]. Thus, the action of iodine in chloroform over 5 days on 1,4-bis-chloromercuributan-2,3-diol leads to l-chloro-4-iodobutan-2,3-diol [123] and not to a replacement of the two HgCl groups by


iodine [124]:

CHCl1

- C H 2 I

CHOH + I2 + HgCl2 -

CHOH 5 d a y s CHOH CHOH

CH2HgCl CH2I CH2I

The exchange of HgX by chlorine can be carried out by the action of chlorine formed in the reaction between chloric and hydrochloric acids. Thus, 2-acetoxymercuridiphenylene has been converted into 2-chlorodiphenylene by the action of HCl and potassium chlorate [125].

Preparation of 2-chlorodiphenylene [ 125] - A saturated aqueous solution of 0.020 g of KCIO3 is added dropwise to a stirred mixture of 0.180 g of 2-acetoxymercuridipheny-lene, 50 ml of conc. HCl and 25 ml of chloroform. After 30 minutes a further 0.005 g of KClO3 is added in the same way and the stirring continued for 4 hours. The chloroform layer is washed with an aqueous solution of soda. The product is sublimed. The yield of the crude material is 0.056 g; m.p. 56-60°C. This product is worked up with an alcoholic-acetic acid solution of 2,4,7-trinitrofluorenone (product m.p. 133-134°C) and is liberated from the complex by passing its benzene solution through Al2O3. This procedure yields pure 2-chlorodiphenylene in the form of pale-yellow leaflets; m.p. 67.5-68.5°C.

2-Acetoxymercuridiphenylene has been converted into 2-bromo-diphenylene by a solution of bromine in chloroform and into 2-iodo-diphenylene by iodine in KI.

The replacement of a mercury atom by halogen in mercury diacetylides represents a convenient way of synthesizing halo-genoacetylenes. No addition of the halogen to the triple bond takes place if an excess of the halogen is avoided [312].

Preparation of l-trans-2 -bromovinyl-2,2-bromoethynylbenzene [311].

A solution of 1.81 g of bromine in 20 ml of benzene is added in drops to a stirred solu-tion of 3.4 g of bis- (0- trans-2'-bromovinylphenylethynyl)mercury in 150 ml of benzene. At the end of the addition the mixture is stirred for another 10 minutes and the solvent then distilled off under vacuum at 60°C. The residue is extracted with several portions of light petroleum ether and the extract f reedfrom dissolved HgBr2 by passing it through a short column packed with 5 g of animal charcoal containing 0.1 part by weight of a 10% mixture of Pd on carbon. Evaporation of the eluate yields 2.45 g of pale-yellow oil (79%) of _ 1- t rans 2'-bromovinyl-2,2'-bromoethynylbenzene; m.p. about -10°C; b.p. 60°C/ IO"4 mm.

1-Bromo-oct- l-yne and 1-bromophenylacetylene were obtained in a similar manner in yields of 75 and 87%, respectively; CCl4

was used as the solvent in place of benzene [311]. The action of an equimolecular amount of chlorine on trans,

trans - and cis, cis-di(/3-chlorovinyl)mercury (in carbon tetrachloride at room temperature in the first case and at O0C in the second) gives



chlorovinylmercury chloride having the same configuration as the starting symmetric compound [126],

The action of chlorine on cis,cis-di(/3-chIorovinyl)mercury. Preparation of cis-B-chlorovinylmercury chloride [126].

H H H H ( ^>C=C<^ ) Hg + Cl2 ^>C=C<^ + RCl X l Cl HgCl

A solution of 0.032 g (0.000927 g-atom) of chlorine in 5 ml O fJX l 4 cooledjto 0°C is added with stirring to a solution of 0.15 g (0.000464 mole) of cis,cis-di-(£-chloro-vinyl)mercury in 5 ml of the same solvent and the mixture set aside for 30 minutes at room temperature. The resulting precipitate is filtered off and dried. It has a melting-point of 78.5°C. Yield: 0.1 g (72.4%). The melting-point is unaffected by recrystall iza-tion from petroleum ether.

The reaction of cis -^-chlorovinylmercury chloride [127] with an equivalent amount of iodine in ethereal solution leads to 1,2-chloroiodoethylene of the same configuration.

Reaction of cis-/3-chlorovinylmercury chloride with iodine [127]. Preparation of cis-l,2-chloroiodoethylene. A solution of 1.2 g of iodine in dry ether is added to a solution of 1.5 g of cis -/3-chlorovinylmercury chloride in 25 ml of dry ether and the mixture left to stand for 2 days at room temperature. The precipitate is then filtered off and the filtrate decolorized with a few drops of aqueous thiosulfate and dried over anhydrous sodium sulfate. Removal of the ether and distillation of the residue on an oil bath at 109-113°C gives 0.62 g (67%) of the desired product; n™ 1.5805.

bis-Perehlorovinylmercury reacts in the usual manner with chlorine only in the presence of strong illumination [47a]; its reactions with bromine (in CCl4) or with iodine (in boiling xylene) could not be arrested at the stage of the RHgX, even when equi-molar proportions of the reactants were used [47b].

Reaction of the diethyl acetal of chloromercuriacetaldehyde with bromine. Preparation of the diethyl acetal of bromoacetaldehyde [128].

ClHgCH2CH(OC2H6)2 + B r 2 - BrCH2CH(OC2H5)2 + HgBrCl

A solution of 26 g of the acetal in 50 ml of dry chloroform is subjected to a dropwise addition of 12 g of bromine in 30 ml of the same solvent, with cooling and stirring. A few minutes after the end of the addition the mercury salt is filtered off, the residue washed with chloroform and the solvent evaporated off from the combined filtrates. Distillation of the residue gives 11.2 g (80%) of the desired product; b.p. 45-46°C/10 mm; V 1.4405; d420 1.2853.

Reaction of the ethyl ester of mercuri-bis-acetic acid with bromine [ 129]. A solution of 10 g (0.062 mole) of bromine in 10 ml OfCCl4 is added drop by drop, with shaking, f irst with cooling and finally with heating to 50°C on a water bath, to 11.5 g (0.031 mole) of the ester in 15 ml of CCl4 . After cooling, the mercuric bromide is separated off (10 g, 91%) and the filtrate subjected to two fractionations. The fraction coming over between 165 and 168°C is collected. The yield of ethyl bromoacetate is 6.9 g (69%); nD20 1.4510; df 1.503.


In inert compounds such as the perfluoroalkyl organometallic derivatives of mercury, the Hg is replaced by a halogen in the absence of solvent, in an autoclave at a high temperature [130].

Preparation of heptafluoro-2-iodopropane [ l 3 0 ] . b i s -Per f luoro i sopropy lmercury (540 g, 1 mo le ) and 510 g (2 mo les ) of iodine are heated f o r 8 hours in an autoclave at 200°C. T h e autoclave is then placed in an ice bath, opened and the cooled product f i l t e red , making use of a solid CO 2 trap to prevent f i l trat ion losses. Th is operation g ives 454 g of crude mater ial which on disti l lation y ie lds 439 g (74%) of pale-pink heptafluoro-2-iodopropane; b.p. 40°C.

Phenylmercury bromide is formed from the action of bromine (in CCl4 at -15°C) on phenylvinylethynyl- and phenylallylmercury [131], but the reaction of bromine in CHCl3 WithC6H5HgCHCl2

gives rise to cleavage of the bond between the mercury atom and the aromatic ring [39a].

The action of bromine and KOBr on dicyclopentadienylmercury [132] leads not only to displacement of the metal by halogen but also to bromination of the organic part of the molecule. In view of the thermal instability of dicyclopentadienylmercury above -15°C, the reaction was carried out between-17 and -20°C.

Reaction of dicyclopentadienylmercury with bromine [ l 3 2 ] . (a) Preparat ion of 1,2,3-tr ibromocyc lopent-4-ene: 4 ml of a heptane solution of bromine (0.127 g of Br per m l ) a re added drop by drop to 0.33 g of dicyclopentadienylmercury in 20 ml of n-heptane and 3 ml of benzene cooled to -20 C, maintaining the bath temperature between -17 and -20°C. The bromine is absorbed very rapidly and a c ream-co lo red , f inal ly crystal l ine, precipitate f o r m s on the walls of the f lask (further addition of bromine g ives a perma-nent color in the solution). The resulting co lor less solution is decanted, the precipitate washed with two 10-ml portions of n-heptane and the washings combined with the main solution. The weight of a i r -dry precipitate of HgBr 2 is 0.35 g. The heptane is evaporated. The crysta l l ine c r eam precipitate (0.57 g ) darkens rapidly in air and exhibits the charac-ter is t i c odor of unsaturated bromides; m.p. 47-55°C. Chromatography on a s i l i ca -ge l column ( d = 12 mm, h = 300 m m ) f r om an 8:2 heptane-benzene mixture and then a 1:1 heptane-benzene mixture (protected f r om the light) g ives 0.41 g of transparent, co lor less , highly re f ract ing crysta ls ; m.p. 63-64°C. The y ie ld of tr ibromocyclopentene is 93%.

(b) Preparation of i somer ic pentabromocyclopentanes: 6 ml of bromine solution are absorbed at a temperature between -2 and-5°C. Chromatography on si l ica ge l (d = 12 mm, h - 300 mm, f r o m heptane) g ive the des i red products; m.p. 96-101°C and 105-107°C. Y ie ld : 49%.

Reaction of dicyclopentadienylmercury with potassium hypobromite. Preparation of hexabromocyclopentadiene [ l 3 2 j . A solution of 0.34 g of the organomercury in 20 ml of benzene is added to a reagent prepared f r om 20 ml of water, 4.5 g of KOH and 0.65 ml of bromine and cooled to f-2°C. The mixture is s t i r r ed mechanically f o r 2 hours at 0 -2 °C , 0.2 g of HgO f i l tered off, the benzene layer separated and the aqueous layer washed with two portions of benzene. The combined benzene solution is dr ied over Na 2SO 4 . Evaporation y ie lds 0.68 g of ye l low crysta ls which af ter chromatography on si l ica gel ( d = 12 mm, h = 100 mm, f r om n-heptane) af fords 0.60 g of the bromide; m.p. 70-72°C. Repeated chromatography g ives C 5 B r 6 ; m.p. 86-86.5°C.

Preparation of 4-bromofluorene from 4-fluorylmercury chloride [ 134]. Asuspension of 40 g of 4 - f luory lmercury chlor ide in 200 ml of glacial acetic acid is s t i r red f o r 8 hours with 14.5 g of bromine in 25 ml of the same solvent. The mixture is boiled and f i l t e red hot. Hydrogen sulf ide is passed into the warm f i l t rate (to r emove the mercury ) and HgS is f i l t e red off . Cooling the f i l t rate g ives 4-bromof luorene, which is subsequently recrys ta l l i zed f r om acetic acid; m.p. 165°C. Y ie ld : 16.1 g (66%).



For the preparations of o-iodophenol and o-iodoeresol, see [132a] and [133], respectively.

Heating bis-pentafluorophenylmercury with iodine for 15 hours at 150-155°C in a sealed tube resulted in a small yield of pentafluoroiodobenzene [134a]. Replacement of the HgCl group in mercurated polystyrene by 3 hours of boiling with iodine in CHCl3 gave a quantitative yield of poly( o-iodostyrene) [134b].

Halogen derivatives of ferrocene were f irst prepared [135, 136] by a mercury-halogen exchange. Iodo- and bromoferrocene were obtained by the action of the corresponding halogens on ferrocenyl-mercury chloride, and di-iodo- and dibromoferrocene analogously from 1,1' -dichloromercuriferrocene [135] (di-iodoferrocene was also made by the action of iodine in xylene on its symmetrization product). 1 '-Chloro-I- iodo- and 1'-bromo-l-iodoferrocene were prepared by the action of a hot solution of iodine in xylene on 1-(l '-chloroferrocenyl)mercury chloride and l - ( l ' -bromoferrocen-yl)mercurybromide [136].

Preparation of iodoferrocene [135]. A solution of iodine in xylene is gradually added to a hot solution of ferrocenylmercury chloride, precipitating the pale gray-green com-plex of ferrocenylmercury chloride with iodine which is easily converted into d i ferro-cenylmercury by aqueous sodium thiosulfate. Addition of a large excess of iodine re-places the mercury by iodine in the complex, and the latter 's color changes to black. The solution is cooled and the precipitate washed with alcohol, carefully ground up and stirred for I ^ hours with aqueous thiosulfate. This operation is repeated twice and the precipitate washed several times with ether. The ethereal extracts are combined and the solvent evaporated. The yield of iodoferrocene is 64%. Crystallization from methanol on cooling of the saturated solution to - 10°C gives a product with a melting-point of 44-45°C.

Chloromercuricyclopentadienyltricarbonylmanganese easily r e -acts with iodine or with iodine chloride, giving iodocyclopenta-dienyltricarbonylmanganese [ 137].

Reaction of chloromercuricyclopentadienyltricarbonylmanganese with iodine [137]. A solution of 2.5 g (0.01 mole) of iodine in 100 ml of absolute CCU is added drop by drop, at the boiling-point of the carbon tetrachloride, to a suspension of 2.2 g (0.005 mole) of the carbonyl in 25 ml of the same solvent. The color becomes permanent after half of the iodine has been added. The cooled mixture is f i l tered and the f i l trate treated with aqueous Na2S2O3 , washed with water and dried over MgSO1J. Vacuum evaporation of the solvent gives 1.52 g (92.1%) of pure iodocyclopentadienyltricarbonylmanganese; m.p. 33-34°C.

Free thiocyanogen reacts with organomercury derivatives simi-larly to the halogens:

RHgX + (CNS)2 —• RCNS + HgXCNS

The reaction of diferrocenylmercury with thiocyanogen,leadingtoa replacement of mercury by sulfur, is described further on in the chap-ter under "Synthesis of the organic compounds of group VI elements".


Iodine chloride reacts according to the reactions

R2Hg + 2 ICl 2R i + HgCl2

RHgX + IC1-* RI + HgXCl

The action of ICl3 will be mentioned later in this chapter. Like the acids, N-bromoamides [73], N-bromoimides [70, 74,75]

(with divinylmercury [64a]) and hypobromites [70] react with fully substituted aromatic organomercuries. The positive bromine atom of these acid derivatives combines with the radical, and in the case of the N-Br compounds the RHg residue forms an RHgN- derivative. For example:

RHgR ' + BrN (COCH2)2 -> RBr + R 'HgN (COCH2)2

If the RHgR' is asymmetrical (R / R' ) , the bromine combines with the radical which is more electronegative in Kharasch's series [74, 75]. The reactions are carried out with moderate heating and the acid derivative sometimes plays the part of a solvent.

Ultra-violet irradiation results in a radical mechanism; the bromine then adds not to the radical but to the mercury atom.

The action of nitrosyl chloride on fully substituted polyfluoro-chloroalkyl compounds of mercury is accompanied by replacement of the Hg byCl[140a]. The main reaction is, however, replacement of the Hg by NO.

h) Reactions with Halides and Other Salts of Elements, and Also with their

Alkyl (Ary l ) Halides and Hydrides

The reactions of normal exchange between halides and fully substituted organomercuries or organomercury salts:

R2Hg + M w X 7 1 RHgX + RM<"> X B - 1

R2Hg + 2M<"> Xn ^ HgX2 + 2RM" l>Xn-i

RHgX + M<^X„ HgX2 + RM<"»X„_,

are important from the preparative point of view. In comparison with Grignard reagents, the use of organomercury

derivatives in such exchanges allows the synthesis of a narrower range of organometallics. On the other hand, the method permits very diverse radicals to be joined to the element in question, in-cluding those radicals which are not inert to Grignards.



Alkali metal and alkaline earth halides do not enter into reactions of this type with organomercury derivatives. The halides of Be, Mg, Zn and Cd also have not been utilized for the synthesis of organometallic compounds by the above reaction. The simplest example of such a process, described later in this chapter, is the interaction of organomercuries with labeled mercuric salts Hg+X2. The above exchange cannot be used to prepare the organometallics of the elements situated in the odd periods (from K to Ni, Rb to Pd, and so on). The action of Cu, Mn, Fe, Co and Ni halides, which initiate the decomposition of the organomercury compounds, are mentioned later in this chapter. The exchange with the halogen compounds of C, N and O also does not lead to the desired result. The halides of B, In, T l , Si, Ge, Sn, P, As, Sb, Bi, S, Se, Te and I do enter into the above reaction and have been utilized for the preparation of the organometallic compounds of these elements (Ladenburg, Friedel and particularly Michaelis).

ICl and I C I 3 react most easily in this way, similar to the free halogen themselves.

The reactions with aromatic (and in the case of I C I 3 also with /3-chlorovinyl) compounds take place in aqueous suspension at room temperature; ICl gives the aryl iodide (see the preceding section), and ICl3 the diaryl(di-/3-chlorovinyl)iodonium chloride and aryl-(3-chlorovinyl iodide chloride. At room temperature, the reaction proceeds with BCl3 and AsCl3, more slowly with P C I 3 . However, heating is generally required, especially to com-plete the reaction, sometimes to temperatures as high as 200-300°C. The reaction conditions must be made more vigorous if a more highly alkylated (arylated) product is desired, corresponding to fuller dealkylation (dearylation) of the organomercury compound (to mercuric halide). The actual choice of the conditions depends on the radical passing from the mercury to the other atom. Satu-rated aliphatic radicals are exchanged with some difficulty, phenyl more readily, and phenyl radicals containing class I substituents in the 0 - or p-position, e.g. anisyl, as well as furyl, thienyl and other superaromatic five-membered heterocycles undergo the r e -action with the greatest ease. Vinyl radicals are exchanged readily, similarly to the phenyl.

It should be noted that the above method is not applied very widely for organo-elemental syntheses, although in certain cases (for example, if polymercurated compounds are used as the starting materials) it offers unique possibilities. This is partly due to the fact that in the case of the simpler radicals the preparation via a Grignard reagent is even more convenient, and in the case of the organometallic derivatives of complex radicals and elements ofthe greatest interest to investigators, e.g. As or Sb, there are other, more convenient methods, such as the diazo method. Despite this, the above group of synthetic methods contains many unexplored possibilities and may still undergo considerable development.


S y n t h e s i s o f t h e O r g a n i c C o m p o u n d s o f E l e m e n t s o f G r o u p III o f t h e P e r i o d i c T a b l e

S y n t h e s i s o f o r g a n o b o r o n d e r i v a t i v e s . Alkenyl and aromatic boron halides have been obtained by the interaction of boron halides with the organic compounds of mercury.

The former are obtained in the cold or with moderate heating. Examples of compounds prepared in this way are vinylboron di-fluoride (from BF3 and divinylmercury [141]),vinylborondibromide [142], /3-chlorovinylboron dichloride (from RHgCl and BCl3 at 50°C) [143], di-^-chlorovinylboron chloride [143] and pentafluorovinyl-boron dichloride [144] (fromR2HgandBCI3; conditions not reported).

Preparation of vinylboron dibromide [ 142]. BBr 3 (15.0 g, 0.06 mo l e ) is condensed onto 12.5 g (0.05 mole ) of d iv iny lmercury. The mixture is then allowed to warm up to room temperature and set aside f o r some time. T h e product is puri f ied by disti l lation under vacuum; b.p. 35°C/50 mm; y ie ld : 8.1 g (82%).

The interaction between boron trichloride and diarylmercuries, which begins already in the cold, yields arylboron dichloride [66, 145-147]:

A r 2 H g + 2BC13 - » 2 A r B C l 2 + H g C I 2

which reacts further with the excess of diarylmercury to give diary lboron chloride [147]:

A r B C l 2 + A r 2 H g - » A r 2 BCl + A r H g C l

When the Ar was a hydrocarbon residue, Michaelis conducted reaction (1) in a sealed tube at 180-200°C; the interaction with dianisyl- and diphenetylmercury proceeds at room temperature.

On the other hand, Gilman and Moore [66] maintain that high temperatures and pressures are unnecessary even if the Ar in reaction (1) is a hydrocarbon residue. Thus, reaction for 30 min-utes at room temperature between diphenylmercury and BCl3 (in chlorobenzene) gives, after hydrolysis, a 52-70% yield of phenyl-boronic acid [66].

The reaction of Ar2Hg with BBr3 (giving ArBBr2 ) is more con-venient than that with BCl3. It is carried out not in a sealed tube, but by refluxing in benzene [148]. Reports have been published on the syntheses of phenylborondichloride[146] (m.p. 0°C,b.p. 175°C), phenylboron dibromide [148], o-tolylboron dichloride [147], p-tolylboron dibromide [146, 148], p-tolylboron dichloride [146] (m.p. 27°C), 0- (b.p. 212°C), m- (b.p. 218°C) [148] and p- (b.p. 206°C) [146] xylylboron dichlorides, pseudocumylboron dibromide [146, 148], a - (b.p. 124°C/25 mm) and /3- (m.p. 116°C) -naphthyl-boron dichlorides [147], o-and p- (b.p. 182°C/l70 mm, m.p. 300°C) anisylboron dichlorides [147] and 0- and p- (b.p. 400°C/220 mm, m . p . 2°C) phenetylboron dichlorides [147].



Preparation of phenylboronic acid [66l. A suspension of 0.05 mole of diphenylmercury in 500 ml of chlorobenzene is placed in a three-necked round-bottom flask fitted with a st irrer . The flask is connected to a receiver cooled with CO2 acetone and provided with a mercury pressure-relief valve and a gas-inlet tube reaching below the level of the liquid. The inlet tube is connected to a BCI3 supply through a mercury trap serving to remove any chlorine present in boron trichloride and to allow observation of the latter's flow rate. A 100% excess of BCla is passed into the reaction mixture (the amount intro-duced is estimated from the change in the weight of the BCI3 container) and the contents of the flask stirred for 30 minutes. The mixture is fi ltered to separate phenylmercury chloride and the fi ltrate hydrolysed by slow addition of ice. The resulting acid is ex-tracted with four portions of 10% KOH (totalling up to 250 ml). The aqueous layer is washed with 100 ml of ether and acidified. The precipitating pale-yellow solid is re-crystallized from water; yield: 70.5%.

Reaction (2) is conducted in a sealed tube at 300-320°C. Even after several hours of heating with BCl3 in chlorobenzene

[147], p-chloromercuriphenol, p-chloromercuribenzoic acid and methyl-p-carboxyphenylmercury do not give r ise to organoborons. Similarly, no organoboron compound was obtained f rom reactions of diphenylmercury with tri-n-butyl borate under various conditions [66].

F o r m a t i o n o f o r g a n o a l u m i n u m d e r i v a t i v e s . Synthesisofunstable readily polymerizing vinylaluminum halides f rom aluminum halides and vinylmercury compounds (in benzene or CCI4) has been de-scribed [149].

S y n t h e s i s o f o r g a n o i n d i u m c o m p o u n d s . According to Goddard [150], diphenylindium chloride is formed when diphenylmercury is boiled for 37 hours in xylene with anhydrous InCl3.

Preparation of diphenylindium chloride [150]. Anhydrous indium trichloride (from 1.16 g of metallic indium) and 10.77 g of diphenylmercury (3 moles) are boiled for 37 hours in 50 ml of xylene. The mixture is then fi ltered and the precipitate extracted in a Soxhlet with dry benzene to remove organomercury compounds. The residue in the thimble (0.647 g) is diphenylindium chloride, a cream-colored insoluble and infusible crystalline powder.

S y n t h e s i s o f o r g a n o t h a l l i u m d e r i v a t i v e s . Di-n-propylmercury and thalliumchloride give di-n-propylthallium chloride and n-pro-pylmercury chloride [151]. No organothalliums are formed when thallium chloride is reacted under these conditions with di - isoamyl- , dibenzyl- and benzylethylmercury, or with 2-thienylmercury iodide [151].

Fully substituted organomercuries with the mercury attached to the olefinic carbon (/3-chlorovinyl [152, 153], propenyl [154, 155], isopropenyl [156, 157], butenyl [106], vinyl [158] and a- [159 ] and &>- [160] styryl) react with T lC l 3 and T lBr 3 under mild conditions (in ether), giving r ise to the corresponding dialkenylthallium halides. When the ratio was 1 mole of R 2 Hgto 2 moles of TICI3, d i - cis,cis- and di- trans, trans-1 -methy l -2-acetoxy- l -propen- l -y l -mercury also gave high yields of the corresponding cis - and trans-


RTCl 2 compounds [106]. The im/is-isomers of the above organo-mercuries react easier than the e is- isomers. Thus, combination of ethereal solutions of cis, Smras-dichlorovinylmercury and TlCl3

results in immediate precipitation of di - trans - (S-chlorovinylthallium chloride, whereas the precipitate of di-cis-/3-chlorovinylthallium chloride begins to appear only after 4 hours [152]. Under these conditions, cis, trans -dipropenylmercury and TlCl 3 g ive di -trans-propenylthallium chloride [155]. All these reactions proceed with retention of the configuration of the transferred radical (see Chapter 6).

Reaction of trans,trans-dipropenylmercury with thallium tribromide. Preparation of irons,irans-dipropenylthallium bromide [ l54] .

(CH3 H

\ C = C / ) TlBr

H T l B r 3 (0.8 g, 0.0018 mole) is added to 1 g (0.0035 mole) of freshly prepared but not

distilled trans, trans -dipropenylmercury in 3 ml of ether. Immediate abundant precipi-tation takes place. After 1 hour the precipitate is fi ltered off and washed with acetone. The yield of dry product is 0.61 g (94%). Two recrystallizations from pyridine give a crystalline product which becomes yellow but does not melt on heating to 360°C. From the ethereal filtrate, 0.96 g (84%) of trans-propenylmercury bromide is isolated; m.p. 118.5-119.5°C.

Preparation of cis-1-me thy 1-2-ace toxy-1-pro pen-1-y Ith allium dichloride [ 106].

CH3 CH3

> c = c <

CH3COO TlCl2

An ethereal solution of 2.16 g (0.006 mole) of TlClg is added at room temperature to an ethereal solution of 1.5 g (0.003 mole) of di- ( l -methyl-2-acetoxy-l-propen-l-yl ) -mercury (m.p. IOl0C). A crystalline precipitate appears 10 minutes later. After the mix-ture has been set aside for 40 minutes at room temperature, this is filtered off, washed with ether and recrystallized from water. Decomposition temperature 135°C; yield: 80%. After repeated recrystallization from alcohol, the substance decomposes (without melting) at 135°C; it dissolves readily on heating in alcohol, acetone and water, and sparingly in benzene and ether.

Preparation of diphenylthallium chloride [ l 6 l ] . Addition of 2.5 g of T l C l g i n d r y ether to a solution of 2.8 g of diphenylmercury in 50 g of the same solvent results in immediate formation of a white precipitate which, after a few hours, is filtered off and washed with benzene to remove phenylmercury chloride. The residue is diphenylthallium chloride; m.p. 250°C.

Di- o-acetoxyphenylthallium bromide was obtained in a small y ie ld when 1 mole of alcoholic R2Hg was boiled for 3 hours with approximately 2 moles of T lBr 3 ^H 2 O [162].

Considerably better results are obtained by the method devel -oped by Glushkova and Kocheshkov [163, 164] for the synthesis of RT lX 2 and R 2 TlX by the interaction between diarylmercuries and a Tl ( I I I ) salt of an organic acid, thallium tri- isobutyrate. The yields are high in both cases. The reaction proceeds rapidly under mild


364 % ORGANOMERCURY COMPOUNDS

conditions (on br ie f heating in ch loro form) . The method has been used f o r the synthesis of aromatic and thienyl compounds of thal-l ium, and deserves wide application.

Monoarylthal l ium salts are obtained f r o m the interaction of equimolar proportions of R 2 Hg and TlX3

R 2 H g + Tl ( O C O C 4 H 9 - I S O ) 3 - * RT l ( O C O C 4 H 9 - I S O ) 2 + R H g ( O C O C 4 H 9 - I S O )

(R = phenyl, a- and /8-naphthyl, p -ch loro - and p-bromophenyl, p-anisy l , a-thienyl) .

Synthesis of thallium tri-isobutyrate C163]. Heating of 2 g OfT i 2O 3 (0.045 mole) for 5 minutes (until dissolution) in 10 ml of boiling isobutyric acid and subsequent cooling gives a white crystalline precipitate which is f i ltered off and washed with petroleum ether. T h e y i e l d is 1.8 g (44%); m.p. 174-174.5°C, 179-179.5°C after recrystallization from benzene.

Preparation of /?-ch loropheny Ith allium di-isobutyrate [164,]. Thallium tri-isobuty-rate (4.65 g, 0.01 mole) in 15 ml of chloroform is added to a suspension of 4.25 g (0.01 mole) of di-p-chlorophenylmercury in 15 ml of the same solvent. The organo-mercury compound begins to pass into solution when the reagents are mixed, leaving behind a small amount of precipitate which dissolves on heating. Some chloroform is then evaporated and the resulting precipitate filtered off and washed with petroleum ether. Recrystallization from dichloroethane gives 3 g of a substance (m.p. 229°C, with decomposition) and 0.6 g of a substance with a melting-point of 224-225°C. The yield of the product is 73.5%.

Preparation of p-anisylthallium di-isobutyrate [ l63] . A suspension of 3.82 g (0.01 mole) of di-p-anisylmercury in 25 ml of chloroform is added to a solution of 4.65 g (0.01 mole) of thallium tri-isobutyrate in 10 ml of the same solvent (heating). The mixture is heated on a water bath and filtered. After cooling, the f i ltrate gives 3.15 g (yield; 65%) of p-anisylthallium di-isobutyrate, which is subsequently recrystallized from dichloro-ethane; m.p. 196°C.

Diarylthal l ium salts can be prepared by reacting 2 moles of the d iary lmercury with 1 mole of thallium tr i - isobutyrate under the same conditions [164]:

2R2Hg + Tl (OCOC4H9-iso)3 -> R2Tl (OCOC4H9-iso)

This method has been used to obtain good y ie lds of diphenyl- [164], d i - p - t o l y l - [164] and d i - p - an i s y l - [164] thallium salts.

Preparation of di-p-anisylthallium isobutyrate [ 164]. Thallium tri-isobutyrate (2.35 g, 0.005 mole) in 10 ml of chloroform is added to a suspension of 4.15 g (0.01 mole) of di-p-anisylmercury in IOml of the same solvent and the mixture heated until full dis-solution takes place. After some evaporation of the solvent in the cold, the precipitate which appears is filtered off, washed with petroleum ether and recrystallized from dichloroethane. This procedure gives 2 g (66%) of a substance melting at 246°C. Re-peated recrystallization from dichloroethane raises the melting-point to 252°C.

On the basis of the re lat ive ease of c leavage of radicals f r om unsymmetr ic organomercur ies under the action of T lCl3 (in ether

REACT IONS OF ORGANOMERCURY COMPOUNDS 365

or a mixture of ether and toluene) according to the react ion

2RHgR'-+TlCl3 - R2TlCl + 2RHgCI

(RHgR ' =C 6 H 5 HgC 2 H 5 , Q-C1aH7HgC2H5, O-C10H7HgC6H5, and a lso 0-CH3OC6H4HgC10H7-Q and O-C10H7HgC6H2 (CH3 )3 ) , the R groups can be arranged into a s e r i e s which is essent ia l ly in agreement with the s e r i e s which was obtained by Kharasch on the basis of the c leavage of RHgR by acids [165].

C4H9HgCH2C6H5 and T lC l 3 gave only R H g C l . R ' H g C l and thall ium chlor ide [155].

The react ion of dicyclopentadienylmercury with T lOH, conducted in aqueous methanol at +2°C and leading to the format ion of c y c l o -pentadienylthall ium in a y ie ld of 30% [166], has no analogy in the chemistry of organomercury compounds with loca l i zed Hg-C 0 -bonds.

S y n t h e s i s of the O r g a n i c C o m p o u n d s of E l e m e n t s of G r o u p IV of the Per iodic T a b l e

Dichloro- (and d ibromo- ) car bene, f o rming during the decompo-sit ion of phenyl tr ihalogenomethylmercuries , adds to CH bonds of methine and methylene groups of hydrocarbons giv ing r i s e to dihalogenated hydrocarbons. The react ion is conducted with an excess of the hydrocarbon [167]. Th is method has been used [167] to obtain C6H5CH(CH3 )CCl2H (in 35% yie ld, by react ion with C6H5CH2

CH3 ) , C6H5 (CH3 )2CCCl2H (58%, react ion with C6H5CH(CH3 )2 ) , c y c l o -C6H11CCl2H (32%. react ion with cyclo-C6H1 2 ) andC6H5CH(CH3 )CBr2H (6.5%, react ion with C6H5CH2CH3 ) .

The react ions of phenyltr ihalogenomethylmercuries (C6H5HgCCl2

B r , C 6H 5HgCClBr 2 , C6H5HgCBr3 ) with o le f ins has been suggested as a method of synthesis of gem -dihalogenocyclopropanes [168, 406a]; Br in the CHal3 group faci l i tates the react ion [340]

Hal Hal \ /

RHgCHal3 + > C = C < - * C +RHgHal

Synthesis of hexachlorocyclopropane [ 168]. Phenyl (bromodichloromethyl)mercury (0.1 mole) in 1 mole of tetrachloroethylene is heated for 1 hour at 90°C. Phenylmercury bromide precipitates (in a yield of 94%) and a 74% yield of hexachlorocyclopropane is obtained; m.p. 103-104°C.

In the same way, bromopentachlorocyclopropane (m.p. 106.4-107.6°C) was obtained in a 48% y ie ld f r o m tetrachloroethylene and C 6H 5CClBr 2 ; tetrachloroethylene and C6H5HgCBr3 gave a 26% y ie ld of 1 ,1-dibromotetrachlorocyclopropane, m.p. 114-115°C [168].



1,1-Dibromocyclopropane has been made in 53% yie ld f r om ethylene and CeH5HgCBr3 (autoclave, 24 hours, in benzene), 1,1-dichlorocyclopropane (65% yie ld, in chlorobenzene) f r om ethylene and C6H5HgCCl2Br, and l , l -d ich loro-2 ,3-d iphenylcyc lopropane (90% y ie ld , 2% hours at 85°C in benzene) f r o m frans-stilbene and C6H5HgCCl2Br [168].

The methylene group generated in the decomposit ion of b i s -halogenomethylmercury or a halogenomethylmercury halide adds to the double bond in cyclohexene with the format ion of norcarane (the reaction is car r i ed out by boi l ing in benzene f o r 8 days, in the latter case in the presence of diphenylmercury) , for example [166a]:

S y n t h e s i s of o r g a n o s i l i c o n compounds . In this f ie ld , synthesis of ary l t r ich loros i lanes , requir ing heating to high temperatures, has been accomplished:

Preparation of phenyltrichlorosilane [ l69] . Diphenylmercury (IOOg) is heated for several hours with 50 g of silicon tetrachloride to 300°C in a sealed tube. Distillation of the product gives 30 g of a fraction boiling at 197-198°C, representing the desired compound.

p-To ly l t r i ch loros i lane was prepared in the same way [169]. The react ions of SiCl4 and also alkyl (ary l and alkoxy) ch loro -

si lanes with mercury der ivat ives of oxo-compounds are ca r r i ed out in boil ing isopentane and lead to full replacement of the halo-gens by the vinyloxy group, giving good y ie lds of te t rav iny loxy-si lane or of v inyloxyalkyl - , v iny loxyary l - , or v inyloxyalkoxysi lanes, respec t i ve ly [170]:

nHg(CH2CHO)2 + R4_„ SiClrt R4^rtSi (OCH=CH2)rt +ClHgCH2CHO

R =CH3 , C2H5, C6H5, ClCH2, C2H5O; « = 1, 2, 3, 4

Preparation of viny loxytrime thy Isi lane [ l70] . A solution of I l g (0.11 mole) of trimethylchlorosilane in 20 ml of isopentane is gradually stirred into 32 g (0.11 mole) of mercuri-bis-acetaldehyde in 70 ml of the same solvent and the mixture boiled for 2 hours and filtered. The precipitate is washed with two portions of isopentane and the isopentane evaporated off. Fractionation gives 8.4 g (72%) of vinyloxytrimethylsilane; b.p. 74-75°C; Tio201.3885; <f420 0.7720. For (C2H5)3SiOCH=CH3; b.p. 53-54°C/20 mm; n ™ 1.4275; and for Si(OCH=CH2)4; b.p. 79-80°C/2 mm; nD 201.4896.

Tr ia lky l iodos i lanes react easi ly with the es ters of m e r c u r i - b i s -acet ic acid according to the scheme:

Ar2Hg + 2SiCU -+ 2ArSiCl3 + HgCl2

2Alk3Si I + Hg (CH2COOR)a 2Alk3SiCH2COOR + HgI2


Thus, methyl tr iethyls i ly laeetate was prepared in a 52% y i e ld f r o m tr iethyl iodosi lane and mercur i -b i s - (me thy l acetate) [171].

Dihalogenocarbenes fo rming in the decomposit ion of phenyl-t r iha logenomethylmercur ies also enter the Si-H bonds in a r y l -s i lanes, giv ing 77-90% y ie lds of dihalogeno der ivat ives of organo-s i l icon compounds [167], The react ion is applicable to R3SiH and (C6Hs)2SiH2 with benzene as the solvent.

C 6H 5HgCCl 2Br and C6H5HgCBr3 and v inyl tr imethyls i lane (30 hours of boi l ing in benzene) gave, respect i ve ly , 1 ,1-d ich loro- and 1,1-d i -bromo-2- t r imethy ls i l y l cyc lopropanes , in y ie lds of 67 and 57% [168].

Syn thes i s of o r g a n o g e r m a n i u m c o m p o u n d s . Esters of m e r c u r i -b is -ace t i c acid react in inert solvents with t r ia lky lgermanes (in tetrahydrofuran) or better with t r ia lky l iodogermanes (in petro leum ether) with the format ion of good y ie lds of t r i a lky lgermy lace t i c es t e rs [171]:

/ ° \ ° 2R3Ge I + Hg J CH2C^ J -» R3GeCH2C^ + Hg I2

\ ^o rA ^ O R

The react ions are ca r r i ed out in the presence of pyr idine, which binds the mercur i c iodide f o rmed into a complex, HgI2.2C5H5N, that is easi ly separated by f i l trat ion.

Preparation of methyl tripropylgermylacetate [ l 7 l ] . Tripropyliodogermane (33 g) is added drop by drop to a solution of 17.5 g of the methyl ester of mercuri-bis-acetic acid and 6 ml of pyridine in petroleum ether. The mixture is boiled for 30 minutes and filtered. Fractionation of the filtrate gives 19.5 g (71%) of the required product; b.p. 81.5-84°C/1.5 mm; Tiz520 MSSO; ^420 1.0518. The same method is used to prepare the ethyl (b.p. 105-108°C/5 mm; nD20 1.4562; ^4201.04 1 8), methyl and propyl tributylgermyl-acetates.

The react ions of the es ters of mercur i -b i s - ace t i c acid with t r iamylhalogenogermanes are conducted by boil ing the reactants f o r an hour in tetrahydrofuran.

V iny l t r ich lorogermanium has been made [172] in 70% y ie ld by heating d iv iny lmercury to 80°C with germanium tetrachlor ide:

GeCl4 + (CH2=CH)2Hg - CH2=CHGeCI3 + CH2=CHHgCl

The interactions of d ia ry lmercur i es with GeCl 4 in an autoclave at 180°C g ive r i se to smal l amounts of A r G e C l 3 [173], Considerably better results are obtained f r o m the react ion of d ia ry lmercur i es with Ge( I I ) halides (see later in this chapter) .

Dihalogenocarbenes f o rmed in the decomposit ion of phenyltr i -halogenomethylmercur ies again add to Ge -H bonds. The reactions a re ca r r i ed out in benzene, as in the case of the organosi l icon



compounds [167]. This method is used to prepare (C6H5 )3GeCCl2H in 88% y ie ld f r o m (C6H5 )3GeH.

In general f o rm , this react ion can be represented by

S y n t h e s i s of o r g a n o t i n c o m p o u n d s . Heating of a mixture of d i -phenylmercury and stannic chloride g ives r i s e to severa l phenyl organotin der ivat ives f r o m which diphenyldichlorostannane can be isolated [174]. Better results are , however , obtained f r om the r e -duction of diphenylmercury with stannous chloride (see later in this chapter) .

The interaction of phenyl (bromodichloromethyl )mercury with tri-n-butylstannane proceeds according to the reaction [413a]:

(Ii-C4H9)3SnH + C6H5HgCCl2Br - (n-C4H9)3SnBr + C6H5HgCCl2H

S y n t h e s i s of o r g a n o l e a d c o m p o u n d s . The exchange react ion proposed by Kocheshkov and Nad' [176] o f f e r s wide preparat ive poss ib i l i t ies in the f i e ld of synthesizing organolead der ivat ives of aliphatic and aromatic s e r i e s . The starting lead salt is the te t ra-acetate , in v iew of the low stability of the tetrahalides. The react ion proceeds according to the equation:

R2Hg + Pb (OCOCH3)4 R2Pb (OCOCH3)2 + Hg (OCOCH3)2

and is ca r r i ed out in ch loro form at room temperature. The y ie lds are excel lent . With other reagent rat ios the interaction of d i a ry l -mercur i e s with lead tetra-acetate (acetate, isobutyrate) prov ides a way of synthesizing monoary l - l ead compounds [177-178]:

These react ions are also conducted in ch loro form [177, 178] and proceed less readi ly in benzene [179]. The d iary lmercury can of course arylate the monoary l - l ead compound. Diary l - Ieaddiacetates have been prepared in this way [178a].

Reac t i on s with t i t an ium ha l ides . The react ion with titanium tetrachlor ide [180] is

2 (C6H5)2Hg + 2 TiCI4 - » 2C6H6HgCl + Ti2Cl6 + C6H5C6H5

See also [181]. (C5H5 )2TiCl2 and (CgH5 )2Hg g ive r i s e to (C5H5)2

Ti (C 6H 5 ) 2 [1381.

C6H5HgCX2Br + -^M-H - M - C X 2 H + C6H5HgBr

M = C, Si, Ge; X = Cl or Br

\ \

Ar2Hg + Pb (OCOR)4 ArPb (OCOR)3 + ArHgOCOR


Syn thes i s of the O r g a n i c C o m p o u n d s of the E lements of G r o u p V of the Per iodic Tab le

Synthes i s of o r g a n o p h o s p h o r u s compounds . The reactions of organomercury compounds with phosphorus tr ichlor ide ( t r ibromide ) proceed according to the reactions

and are an important method for the synthesis of alkyl (ary l ) d ich loro-phosphines and diarylchlorophosphines.

The reactions of P C l 3 with organomercur ies [182-184] occur v e r y much more easi ly than those of SiCl4 , but less readi ly than those of AsCl 3 . They are usually car r i ed out at 180-250°C. The y ie lds are better if the P X 3 or R P X 2 is in excess .

As usual, the reactions of alkyl (aryl )dichlorophosphines with d iary lmercury compounds

occur much less readi ly than those of R2Hg with PCl 3 , and the r e -action of A lkPC l 2 with d ia lky lmercur ies , where the alkyl group is a residue of a saturated hydrocarbon, has not been uti l ized at al l . The above reaction was also used to make the mixed R R ' P C I . The d iary lmercury can be replaced by an a ry lmercury halide, par t i -cularly when the ary l is easi ly exchanged, i .e . when it is more e lectronegat ive (in the Kharasch ser i es , already mentioned in this chapter) than phenyl, for example to ly l .

Preparation of alkyldiehlorophosphines [183]. Perfectly dry dialkylmercury (20 g) and 60 g of HCl-free PCI3 are heated for 6 hours in sealed tubes at 250°C. The object of this heating is to decompose the alkylmercury chloride formed into an olefin and calomel, as otherwise it interferes, being partly distilled over with the phosphine. To prepare ethyldichlorophosphine, 15 g of diethylmercury and 45 g of PCl 3 are used. When the tubes are opened, the liquid is decanted from the crystals and carefully distilled in the absence of moisture. The yield is low.

Ethyldichlorophosphine has a boiling point of 114 117°C, n-propyldichlorophosphine 140-143°C, isopropyldichlorophosphine 135- 138°C, isobutyldichlorophosphine 155-157°C and isoamyldichlorophosphine 180-183°C.

The reactions of d iv inylmercury with phosphorus trihalide are conducted under mi lder conditions. Vinyldichlorophosphine [141, 185] and vinyldibromophosphine [142, 185] have been obtained.

Preparation of vinyldibromophosphine [ l42] . PBr3 (13.5 g, 0.05 mole) and 12.7 g (0.05 mole) of divinylmercury are heated with stirring for 12 hours at 80°C. The liquid (fuming in air) is distilled off. Repeated distillation gives 8.5 g (78%) of vinyldibromophosphine; b.p. 60°C/20 mm.

R2Hg + PCl3 - RPCl2 -r RHgCl

RHgCl + PCl3 RPCl2 + HgCl2

R2Hg + RPCl2 -> R2PCl + RHgCl

(1) (2)

(3)

RPCl2 + R2Hg R2PCl + RHgCl



[(CH3)3SiCH2J2Hg does not react with PC l 3 at 760C and af ter 12 hours of boil ing in benzene [185a].

Preparation of phenyldichlorophosphine [ l84] . Diphenylmercury (10 g) is heated with 34 g of PCl3 to 180"C in a sealed tube. After being cooled, the liquid is decanted from the large amount of phenylmercury chloride formed and subjected to distillation. The excess of PCI3 is followed between 216 and 220°C by a slightly turbid liquid from which a little metallic mercury separates out on standing. This liquid is decanted from the mercury and redistilled. It is then obtained in perfectly pure form; various authors quote boiling-points for C 6 H 5 PCl (225, 221-222, 222°C); d ™ 1.319.

The preparations of o - [187, 188], m- [188] and p- to ly ld ich loro-phosphines [188], w-chlorophenyldichlorophosphine [189], a-naph-thyldichlorophosphine [190] and p-dimethylaminophenyldichloro-phosphine [186] have been reported.

During the preparat ion of diphenylchlorophosphine [191] by the action of diphenylmercury on phenyldichlorophosphine the react ion proceeds only to the stage of phenylmercury chlor ide, even at a high temperature (222°C) and when the phenyldichlorophosphine is taken in a la rge excess .

Improved method of synthesis of diphenylchlorophosphine [ l92] . Diphenylmercury (55 g) and 125 g of phenyldichlorophosphine are heated for IJ hours at 230-240°C under a current of CO2 in a round-bottom flask provided with reflux and a CaCl2 tube, and then the product is extracted with 4 portions of benzene. Benzene and phenyldichloro-phosphine are then distilled off at ordinary pressure up to 260°C and the residue frac-tionated under vacuum. The f irst fraction (56 g, 178- 189°C/16 mm) gives on repeated distillation 50 g of pure diphenylchlorophosphine boiling at 179 180°C/16 mm. The second fraction (20 g, 188-230°C/16 mm) is mainly diphenylchlorophosphine oxide.

With an excess of diphenylmercury, the y ie ld of the diphenyl-chlorophosphine [193] is 55%.

The same method can be used to synthesize asymmetr ica l d i a ry l -chlorophosphines R R ' P C I . The tolyl radical is t rans fe r red more read i ly than the phenyl.

Preparation of phenyl-p-to Iy lchlorophosphine [194]. Phenyldichlorophosphine (78 g) and 60 g of p-tolylmercury bromide (an equivalent amount of p-tolylmercury chloride can of course be used) are refluxed for 2-3 hours at 270°C under a current of CO2. The initial reaction proceeds very vigorously. The mixture is extracted with benzene, the solvent distilled off after filtration and the residue fractionated in CO2 under reduced pressure. At 230-240°C/100 mm, 30 g (yield: 63%) of the product is collected, and 24 g of CeH5PCl2 were recovered.

Similar results a re obtained start ing f r o m tolyldichlorophosphine and diphenylmercury [148,195]. Phenylpseudocumylchlorophosphine [195] was prepared in the same way; m-anisylphenylchlorophosphine has been synthesized f r o m d i -w -an i sy lmercury and phenyldichloro-phosphine (1 hour at 215-220°C, under nitrogen) [195a].

Syn thes i s of o r g a n o a r s e n i c c o m p o u n d s . Th is is based on the fo l lowing group of react ions:

R2Hg + AsCl3 - » RHgCl + RAsCl2


RHgCl + AsCI3 HgCl2 + RAsCl2

R2Hg + 2AsCl3 - , HgCl2 + 2RAsCl2

R2Hg + R1AsCl2 —• RHgCl -| RR'AsCl

Rl IgCI + R'AsCI2 HgCI2 - RR'AsCl

R2Hg + AsCl3 HgCl2 + R2AsCI

2RHgCl + AsCl3 - HgCI2 I- R2AsCI

R2Hg + R'AsS HgS + R'RoAs

and is in wider use than any other method described in this section. Michaelis used this method to obtain for the f i rst time the r e -

presentatives of such important classes of arsenic compounds as aryldichloroarsines and diarylchloroarsines, in particular phenyl-dichloroarsine and diphenylchloroarsine. To the present day the method finds particular application when the ary l - and alkylarsonic acids through which chloroarsines are now usually obtained cannot be synthesized f rom diazo compounds or f rom alkyl halides. For example, this is the case with furan and thiophene derivatives, and so on.

The reaction of AsCl3 with organomercuries proceeds readily. Thus, even diethylmercury reacts already at room temperature with ASCI3, with evolution of heat, dealkylating to the stage of C2H5HgCl. As expected, the mercury derivatives of radicals situated in the electronegative part of Kharasch's ser ies react with particular ease, especially furyl , thienyl, etc.

Replacement of the second chlorine atom in AsCl3 with organo-mercury derivatives is more difficult, and more vigorous conditions are required to utilize the radicals in organomercury salts RHgCl. The reaction is usually completed (brought to a state of equilibrium) by not too prolonged heating.

A whole ser ies of papers has been published [191-207] laying down the formations of this method. Descriptions have also appeared on the preparation of asymmetrical diarylchloroarsines [199] and synthesis of aliphatic chloroarsines [203-208]: /3-chlorovinyldi-chloroarsine (Lewisite I, f rom AsCl3 and jS-chlorovinylmercury chloride [209]) and perfluorovinyldichloroarsine [40, 144].

C F 2 = C F A S C I 2 and C2H5HgCl have been obtained f rom the inter-action of CF2=CFHgC2H5 with AsCl 3 [40]. The following have been synthesized: anisyl- [201, 210] and phenetyldichloroarsines [210], phenoxyphenyldichloroarsine [211], 0- and p-tolyldichloroarsines [200, 210], di-p-toly lchloroarsine [203], 0-, m- and p-xyly ldi-chloroarsines [212], pseudocumyldichloroarsine [212], a-naph-thyldichloroarsine [190, 208, 210, 213], /3-naphthyldichloroarsine [212], as well as pr imary [207, 214-216], secondary [214] and tert iary [214] arsines of the thiophene and furan ser ies [204, 205].



S y n t h e s i s of o r g a n o a n t i m o n y compounds . Dimethylmercury r e -acts v igorously with StaCl3 to g ive a compound of methylmercury chlor ide with trimethylantimony chloride and separation of metal l ic mercury [217].

Triphenylantimony chloride and diphenylantimony t r ich lor ide are obtained [218] when diphenylmercury is heated to 130°C with SbCl3

in xylene in a sealed tube. Under mi lder conditions (boiling in benzene) the only organoantimony der ivat ive f o rmed is diphenyl-antimony chloride [219]. The latter is not produced in the react ion of SbCl3 wi thphenylmercury bromide ([220], conditions not reported ) .

S y n t h e s i s of o r g a n o b i s m u t h c o m p o u n d s . Production of organo-bismuth der ivat ives f r o m BiX3 and organomercur ies has r ece i ved l i t t le attention, and that only in the aromatic s e r i e s . The react ion is not always smooth. Thus the action of B iC l 3 on diphenylmercury (5 hours in boiling ch loro form) leads not to an organobismuth c o m -pound, but only to the formation of C6H5HgCl [222, 223]. On the other hand, triphenylbismuth has been made in 100% y ie ld by the react ion of diphenylmercury w i thB iBr 3 over 20 hours in ether [224].

In the case of d i -o -carboxypheny lmercury the exchange in ether proceeds with di f f iculty, and the react ion can only be car r i ed out in the absence of solvent [221].

The react ion of diphenylmercury with O-C1 0H7BiBr2 gave [224] mainly phenylmercury bromide, some (O-C10H7 )2Hg and (C6H5 )3Bi, and a very smal l amount of a product which could have been a -C10H7Bi(C6H5 )2 . Rather unexpectedly, the react ion of (C6H5 )2Hg with (O-C1 0H7 )3BiBr2 gave not A r 3 BiAr ' 2 but a mixture of ( a -C1 0H7 )3Bi, (C6H5)3Bi and O-C10H7Bi(CgH5)2 with C6H5HgBr and (O-C10H7 )2Hg [224].

F o r m a t i o n of o r g a n o v a n a d i u m compounds . Unstable C6H5VOCl2

and C6H 5 VCl2 appear in the interactions of diphenylmercury with VOCl 3 and VCl4 in cyclohexane at room temperature [225].

S y n t h e s i s of the O r g a n i c C o m p o u n d s of E lements of G r o u p Vl of the P e r i o d i c T a b l e

The action of sulfur dichloride has been t r i ed out on the m e r -carbides. C2Hg6Cl6 does not react with S2Cl2 at 120°C. The base C2Hg6O2(OH)2 g ives the compound

(ClHg)2C-C(HgCl)2

with a solution of S2Cl2 in benzene, el iminating some of the mercury [225a].

The react ions of thionyl chloride with R 2Hg are accompanied by


scission of one (R = C6H5 [226], C6H4N(CH3)2 [227]) or both (R = /3-C10H7 [226]) C-Hg bonds. The former reaction gives the c o r r e s -ponding RHgC 1, the latter /S-C10H7Cl and metall ic mercury .

Arylsulfonic acid chlorides, for example benzene- and toluene-sulfonic acid chlorides, give with diarylmercuries very small y ie lds of diaryl sulfones [228]:

2RSO2Cl + R'2Hg 2RS02R'

Chloromercuriacetaldehyde and sulfur trioxide in dichloroethane (12 hours on a water bath) f o rm sulfoacetic acid (isolated in the f o rm of the barium salt) in 41% yield [229].

Preparations of the sulfonic acid derivatives of anthraquinone by the action of sulfonating agents on the mercury compounds of anthraquinone have been described [59-62].

Diary lmercuries (RCgH4)2Hg and arylsulfenyl chlorides R C6H4

SCl give the asymmetrical diaryl sulfides RC6H4SC2H4R' after standing for 48 hours in chloroform in the dark at room tempera-ture [230].

Di ferrocenylmercury and thiocyanogen give a complex which is transformed into di ferrocenyl disulfide in 15% yield on treatment with sodium thiosulfate [231].

Diarylselenides are formed in the interaction of diarylmercury with SeBr4 in carbon disulfide:

SeBr4 4- 3R2Hg - R2Se + RBr + 3RHgBr

Fxill dearylation of the diarylmercury occurs when the SeBr4 is in excess [232]:

2SeBr4 |- SR2Hg 3HgBr2 + 2R2Se + 2RBr

A 21% yield of diferrocenylselenium has been obtained f rom di ferrocenylmercury and SeBr4 (boiling for an hour in chloroform, fol lowed by treatment with sodium thiosulfate) [231].

Careful heating of dialkylmercuries with SeO2 g ives dialkyl-seleniums [233].

Diarylselenium halides react with diarylmercuries according to the reaction [234, 235]:

R2SeCl2 + R2Hg - R2Se + RCl + RHgCl

in CS2, acetone, or CCl4 in the cold, or according to

RHgCl + R2SeCl3 - R3SeCl-HgCl2

on heating in acetone or in the absence of solvent. Mixed A rSeAr ' have also been obtained for various aryls in

compounds of mercury and selenium [236]. Unexpectedly, the action of tellurium dichloride on diphenyl-

mercury (several hours of heating to 2000C in a sealed tube) g ives



r i s e to chlorobenzene and tel lurium amalgam [237]:

R2Hg + TeCl2-> 2RC1 + HgTe

Boi l ing of RHgCl having the structure

^ v c V HgCl x X

with TeC l 4 in ch lo ro fo rm ( for X = CH3 ) or in acetonitr i le (X = COOC2

H5) resulted in the corresponding ary l te l lur ium tr ich lor ides [238]:

RHgCl + TeCl4 -> RTeCl3 + HgCl2

Symmetr ica l (when A r = A r ' ) and asymmetr ica l diaryl te l lur ides have been made by the react ion [239]:

ArTeCl3 + ClHgAr' HgCl2 + ArAr'TeCl2 ArTeAr'

on boil ing in dioxan in the absence of moisture. An attempt to prepare organouranium compounds by heating d i -

e thy lmercury with UF4 at 150-170°C [240] was unsuccessful.

S y n t h e s i s of the O r g a n i c C o m p o u n d s of E lements of G r o u p V l l of the Per iod ic Tab le

P r e p a r a t i o n of i o d o n i u m salts a n d i od ide d i c h l o r i d e s RlCl2 Wi l l ge rod t ' s react ion [241, 242], the preparation of iodonium salts f r o m ary l iodide chlor ides and d iary lmercur i es (or organomercury sal ts ) :

C6H5ICl2 + (C6H5)2Hg (C6H5)2 ICl + C6H5HgCl (1)

C6H5ICl2 + C6H5HgCl (C6H5)2 ICl + HgCl2 (2)

has an ext remely wide applicabil ity. Use is general ly made of r e -action (1), which proceeds smoothly under mi ld conditions (at r oom temperature, in aqueous suspension or solution in organic solvents) .

Preparation of diphenyliodonium chloride [241, 242]. Diphenylmercury (5 g) is dis-solved with 5 g of phenyl iodide chloride in a small amount of water, diluted with water, shaken for 12 hours and filtered. Evaporation of the filtrate results in crystallization of needles of diphenyliodonium chloride; m.p. 230°C. The solid residue fi ltered off con-tains C6H5HgCl and the double salt (C6H5 )2 ICLHgCl2 . The latter is dissolved by boiling with water and mercury precipitated from the filtrate with H2S; evaporation of the filtrate gives a further amount of diphenyliodonium chloride.

The exchanges between A rHgX or Ar 2 Hg and iodine t r ich lor ide :

2ArHgCl + ICl3 •-> Ar2 ICl + 2HgCl2


Ar2Hg + IC l 3 - * Ar2ICl + HgCI2

proceed just as easily [243]. The reactions with vinyl organomer-curies take place in a similar manner. These reactions o f fer a simple synthetic route to the iodonium salts. A ry l iodide chlorides can be made if the ICl3 is taken in excess and the diarylmercury is gradually added to the reaction mixture:

Ar2Hg + ICl3-* ArICl2 + ArHgCl

This reaction is of preparative significance in the case of the vinyl-type organomercuries.

Preoaration of the double salt of diphenyliodonium chloride and mercuric chloride [243]. A solution of 2 g (0.008 mole) of ICl3 in 1:10 HCl is added to 2.5 g (0.007 mole) oi diphenylmercury with energetic stirring and cooling. When the reaction is complete (15-20 minutes) the solid material is fi ltered off, washed with alcohol and ether and recrystallized from water; m.p. 168-170°C; yield: 2 g (50%). Thecomposi t ionof the product is (C6H5 )2 ICLHgCl2 .

j3-Chlorovinylmercury chloride [and di-(/3-chlorovinyl)mercury] reacting with ICI3 or chlorovinyl iodide chloride gives the double salt of HgCl2 and di-/3-chlorovinyliodonium.

Preparation of di-/3-chlorovinyliodonium chloride [244]. A 30-ml portion of 3% HCl is poured onto 46 g (0.15 mole) of irons-/?-cMorovinylmercury chloride and a solution of 17.5 (0.075 mole) of ICl3 in another 30 ml of 3% HCl gradually added. The reaction comes to an end in 20-30 minutes with the appearance of an oily layer and a crystalline residue. The residue is washed f ree from unreacted ClCH=CHHgCi with hot chloroform. The product recrystall izes from water, melts at 149-150°C and has the composition (CICH=CH)2ICl2HgCl. Yield: 3.9 g. A 2-g portion of this product is dissolved in 300 ml of water and the solution acidified with HCl and saturated with H2S over 40 minutes. After the mercuric sulfide has been filtered off, the fi ltrate is evaporated under vacuum at 30-40°C. The crystalline residue weighs 0.5 g (72%). Di-/3-chiorovinyliodonium chlor-ide recrystallized from water melts with decomposition at 110-112°C and forms a pic-rate (m.p. 140°C).

/3-Chlorovinyl iodide chloride is obtained f rom equimolar pro-portions of chlorovinylmercury chloride and iodine tr ichloride.

Cl H Synthesis of trans-0 -chlorovinyl iodide dichloride C=C [245]. Onto

H ^ ^ I C l 2

1.32 g (0.004 mole) of Srans-ClCH=CHHgCl (m.p. 124°C), are poured 5 ml of 16% HCl and a solution of 1 g (0.004 mole) of ICl3 in 5 ml of 15% HCl is added with cooling. The whole mixture is then cooled and shaken for 30 minutes. The product is washed with 15% HCl, alcohol and two portions of ether; m.p. 71°C; yield: 64%.

i) Reactions of Organomercury Compounds with Organic Halides

These occur only rare ly (when the C-Hg bond is not activated by conjugation), and generally under vigorous conditions, in a manner s imi lar to the interactions between alkyl halides and the



organometall ic compounds of active metals such as L i , Na, or sometimes Mg, with the formation of carbon-carbon linkages:

R 2 Hg+ 2R'X-»2RR' +HgX 2

R2Hg + R ' X - RR' -» RHgX RHgX + R'X -» R R ' + HgX2

The reaction proceeds in this way when HX cannot be split out of the alkyl halide under the action of the organomercury compound.

Interactions of this type have been observed for the reaction of diphenylbromomethane [246] withdibutyl-, diphenyl- anddi -p- to ly l -mercur ies , taking place in xylene at temperatures ranging f rom 200°C (d i -p- to ly lmercury ) to 340°C (dibutylmercury) and giving R2R CH; for the reaction of diphenylmercury with benzylidene chloride (at 150°C) giving triphenylmethane [247]; for the r e -action of diphenylmercury with ethylene bromide (6-10 hours at 180-200°C in a sealed tube) giving phenylmercury bromide and ^J-phenylethyl bromide [248]; for the reactions of d i - p -chloromercuriphenyl ether with benzyl chloride [249] and a -fury lmercury chloride with a-chloromethylfuran [250]; and for the reactions of di-p-chloromercuriphenyl ether [249], phenyl-mercury chloride [251], a- furylmercury chloride [250], a-thienyl-mercury chloride [252], a-selenylmercury chloride [253], a-th'ionaphthenylmercury acetate [254], diethylmercury [255], di-phenylmercury [251, 256, 257], ditolylmercury [257] and d i - a -thienylmercury [252, 258, 259] with acid chlorides, giving r ise to ketones. The reactions proceed under milder conditions in the presence of aluminum chloride [260, 261].

Reaction of phenylmercury chloride with benzoyl chloride in the presence of AlCl3. !'reparation of benzophenone [26l ] . Anhydrous AlCls (1.3 g, 0.01 mole) is added, over 30 minutes, with stirring and cooling, to a mixture of 3.2 g (0.01 mole) of phenylmercury chloride and 1.7 g (0.01 mole + 20% excess) of benzoyl chloride. The reaction mixture is heated to 50°C for 2 hours on a water bath and decomposed with ice. Steam-distillation yields 1.04 g of benzophenone (59%).

The yields are lower when the same reaction is carr ied out in carbon disulfide or in nitrobenzene.

Ketones are not always formed in the reactions with acid halides: thus, boiling of phenylmercury fluoride with acetyl chloride results in separation of acetyl f luoride and a 90% yield of phenylmercury chloride [262].

Di ferrocenylmercury boiled for 4 hours in benzene with t r i -phenylchloromethane gives triphenylmethylferrocene in a yield of 18% [231]; with the halides of carboxylic and sulfonic acids the reaction proceeds less readily, requires longer periods of boiling in benzene and results in very small yields of acetyl ferrocene and phenyl ferrocenyl sulfone [231].

The action of triphenylchloromethane in pyridine on a-mercurated


fur furyl alcohol gives r i se to f ission of the C-Hg bond and the f o r -mation of the triphenylmethyl ether of furfuryl alcohol [263].

Only compounds that contain labile mercury react with the halo-genohydrocarbons under mild conditions, with the formation o f C - C linkages. Thus the action of triphenylhalogenomethanes in the cold on mercurated oxo-compounds leads to triphenylmethylacetaldehyde and triphenylmethylacetone [264-266].

Preparation of triphenylmethylacetaldehyde [265]. A solution of 3 g of triphenyl-bromomethane in 25 ml of absolute benzene is added to 3 g of dry unrecrystallized bromomercuriacetaldehyde, the mixture is heated for 2 hours at 50~60°C, boiled for 4 hours and filtered. Evaporation of the benzene yields 2.4 g of crude triphenylmethyl-acetaldehyde; m.p. 85-95°C. Repeated recrystallization from ligroine and then from methanol raises the melting-point to 99-100.5°C.

The p-nitrophenylhydrazone of this compound melts at 245-246°C (from toluene).

The action of t r i - ( ;»-nitrophenyl)bromomethane [265] and the chlorides of carboxylic acids [128, 264-267] (sulfonic acids [268], phosphoric [269], phosphorous [270], phosphinic [269]) on the mercury derivatives of oxo-compounds is directed on the oxygen and leads to vinyl esters of the corresponding acids.

Interaction between chloromercuriacetaldehyde and acetyl chloride (reaction with a transfer of the reaction center). Preparation of vinyl acetate [266].

ClHgCH2CHO + CH3COCl » CH3CO2CH=CH2 + HgCl2

A solution of 7.8 g (0.1 mole) of acetyl chloride in 10 ml of xylene is added to 28 g (0.1 mole) of chloromercuriacetaldehyde in 15 ml of dry xylene. Considerable evolution of heat takes place after 1 minute. After 1 hour the xylene solution is separated off and the solid component washed with xylene. The combined xylene solutions are fractionated on a 30-cm Vigreux column and the 72-74°C fraction collected. Yield: 4.1 g (48%). The last traces of acetyl chloride are removed from the vinyl acetate by shaking with an aqueous suspension of zinc hydroxide. After drying and repeated distillation the vinyl acetate has a boiling-point of 72-74°C; nD201.39 60; d 2 ° 0.9292.

The reaction of chloromercuriacetaldehyde with benzoyl chloride is very much slower (6-8 hours of heating in benzene at 50°C).

Interaction between chloromercuriacetone and acetyl chloride (reaction with a transfer of the reaction center). Preparation of isopropenyl acetate [266].

ClHgCH2COCH3 + CH3COCl » CH3COOC(CH3)=CH2 + HgCl2

Chloromercuriacetone (16 g, 0.05 mole) is treated with a solution of 3.9 g (0.05 mole) of acetyl chloride in 30 ml of dry xylene. Considerable heat is evolved within 1 minute. After 1 hour, 2 ml of quinoline are added to combine the unreacted acetyl chloride, and the solid fi ltered off and washed with two portions of xylene. The fraction boiling at 95-97cC is collected from the combined xylene solutions distilled on a 30-cm Vigreux column. Weight: 3.3 g (66%). After a second distillation the isopropenyl acetate has a boiling-point of 96-97°C; nD201.4 0 03; d 20 0.9127.

The products obtained f rom the addition of mercuric salts to phenylethynyl methyl ketone are also acylated at the oxygen [271],



The esters of mercur i -b is -ace t i c aeid are acylated by acid chlorides both at the carbon and at the two oxygen atoms [129]:

4 O

1 2 3 , / - H g - C H 2 - C + R'COCl

\ 4 ' OR

•U R'COCH2COOR Direction I

^ t C H 2 = C Z 0 c 0 r ' Direction II xOR

— R'COOR + CH2=C=O Direction III

The actual proportions of the products depend on the nature of R and R ' [129].

Reaction of the methyl ester of mercuri-bis-acetic acid and acetyl chloride (direction II) (reaction with a transfer of the reaction center). Preparation of a-methoxyvinyl acetate [ 129]. A solution of 7.5 ml (0.1 mole) of acetyl chloride in 10 ml of chloroform is added with stirring over 30 minutes, to a solution of 34 g (0.1 mole) of the methyl ester of mercuri-bis-acetic acid in 50 ml of dry chloroform. A very small amount of heat is liberated. The mixture is heated for 3 hours at 50-55°C and set aside overnight. The resulting methyl chloromercuriacetate (m.p. 82-83°C) is fi ltered off and the filtrate treated with isopentane for a fuller separation of the organomercury compound. After filtration of the solution and evaporation of isopentane and chloroform, the residue is distilled under vacuum. This procedure yields 3.8 g (35%) of a-methoxyvinyl acetate, b.p. 79-85°C; nD20 1.4121; d ™ 1.045.

The isobutyl ester of mercur i -b is -ace t i c acid gave isobutyl acetoacetate, a product of acylation at the carbon, as well as isobutyl acetate, a product of acylation at the ethereal oxygen [129] (see also Chapter 6).

The action of acetyl chloride on ethyl a-bromomercuriphenyl-acetic acid g ives ethyl a-phenylacetoacetate (together with the O-acyl der ivat ive of phenylacetic ester and ethyl phenylacetate [272]).

In the reactions of arylsulfenyl chlorides with fully substituted mercury compounds one of the aryl groups in the latter is replaced by chlorine [230]. A ry lmercur i aryl sulfides [230] react with a ry l -sulfenyl chlorides (in CCI4, at room temperature) according to the reaction:

ArHgSAr' + Ar"SCl — Ar'SSAr" + ArHgCl

The action of acetyl chloride or P-CH3C6H4SO2I on ArHgSAr ' (in boil ing benzene) also leads to cleavage of the S-Hg and not the C -Hg linkage, and to the formation of A r H g C l o r A r H g I [230]. p-To luene-sulfonic acid chloride does not enter into such a reaction even on boil ing.

Diethylmercury and iodoform (at 120°C) g ive ethylene and ace-tylene [273] together with ethylmercury iodide and ethyl iodide [273].

According to [274], diphenylmercury does not react at 130°C with ch loro form or bromoform; with iodoform it reacts according to the fol lowing scheme, via the asymmetr ical C6HsHgCI3:

(C6H5)2Hg + CHI3 - C6H6 -f C6H5HgCI3 2C6H5Hg I 4- C214


Diphenyl- [275] and dicyclohexylmercury react above 260°C with chloro form and carbon tetrachloride, but in the presence of B iCl 3

diphenylmercury g ives (after 5 hours of boiling in ch loro form) phenylmercury chloride, benzene and biphenyl [276].

The reaction of diphenylmercury (and other R2Hg) with CCl 4

proceeds in di f ferent directions depending on whether it is initiated by peroxides or by light. While the products of the l ight-init iated reaction are phenylmercury chloride, chlorobenzene, and hexa-chloroethane [277, 278], peroxide initiation results in phenylmercury chloride and benzotrichloride [279]. Formation ofhexachloroethane in this reaction has also been reported [279] (see under "Pho to -chemical reactions of organomercury compounds" later in this chapter).

Interaction between diphenylmercury and CCl4 in the presence of acetyl peroxide [279]. Diphenylmercury (5 g, 0.014 mole), 15 g (0.097 mole) of CCl4 and 0.1 g of acetyl peroxide are heated for 3 hours at 120-125°Con an oil bath in a sealed tube. After cool-ing, the tube is opened, another 0.1 g of the peroxide added and the tube resealed and heated for a further 2 hours at the same temperature. Increased pressure is observed when the tube is opened. The reaction products are heated to 30°C and the precipitate of phenylmercury chloride fi ltered off and recrystallized twice from acetone. Weight: 2.2 g (54%); m.p. 257°C. Unreacted diphenylmercury precipitates out of the mother liquor on cooling and after recrystallization from acetone (m.p. 124°C) is found fo amount to 2 g, i.e. 40% of the starting amount.

The reaction product freed from phenylmercury chloride and diphenylmercury is fractionated from an Arbuzov flask. After all CCl4 has been distilled off, a colorless liquid comes over at 86-90°C/18 mm (nD 2° 1.5565) which is collected and subjected to nitration. CT-Nitrobenzoic acid is obtained, which after recrystallization from water melts at 141°C; weight: 0.25 g, corresponding to 18.7% on the reacted diphenylmercury. The above colorless liquid is accompanied by hexachloroethane, which crystallizes in the condenser (0.1 g). After sublimation it melts in a sealed capillary at 185°C.

Application of this reaction to asymmetr ica l organomercur ies :

(C4HSCOO)2

RHgR' + CCl4 RHgCl + R-CCl3

allowed Nesmeyanov, Bor isov et al. [279a] to der ive a radical se r i es showing theorder of decreasing affinity toward the f r e e radical CCI3: 2,4,6-(CH3 )3C6H2 , G-C10H7, P-CH3C6H4, O-CH3C6H4, WI-CH3C6H4, C6H5, C2H5, C4H9, C6H5CH2, C6H11. This sequence coincides with Kharasch's se r i es constructed on the basis of decreasing proton aff inity of radicals in a heterolyt ic reaction with hydrochloric acid.

In the absence of oxygen, d i - isopropylmercury reacts with CDCl3 , CHCl3 and CCl4 over 10 hours at 130°C, abstracting the chlorine and forming isopropylmercury chloride [281a] (cf. under "Photo -chemical reactions of organomercury compounds" later in this chapter: Alk generated f r om Alk2Hg abstracts the hydrogen f r om CHCl3 ) ; severa l other products are fo rmed at the same t ime.

However , acyl peroxides do not initiate the above-descr ibed decomposition of R2Hg (R = C2H5 ). Benzoyl peroxide and diethyl-mercury (under nitrogen, 12 hours at 70-95°C, in the absence of



solvent) give C2H5HgOCOR ( R = C 6 H 5 1 C2H5C6H41 CH3), C2H61C2H4

and very small amounts of Hg, CO2, n-C4H10 and C6H5COOC2H5 [280]. Heating of di ferrocenylmercury in absolute CCl4 results in 57%

of chloromercuri ferrocene, 22% of ferrocene and a tar containing Hg, Cl , C, H and Fe [281], Neither the tar nor chloromercur i -ferrocene is formed in the presence of hydroquinone or benzoyl peroxide. A chain mechanism has been proposed for this reaction [281].

Al ly l iodide reacts with diethylmercury at 120°C with the f o r -mation of biallyl, ethylmercury iodide, and ethyl iodide [273]; d i -phenylmercury does not enter into such a reaction even after boiling in xylene for 300 hours [246].

The action of allyl bromide on p-hydroxyphenylmercury chloride in pyridine at -10°C results, rather remarkably, in easy elimination of mercur ic halide [282].

No formation of C -C bonds is observed in the action of cyanogen halides on organomercuries; cyanogen iodide and dimethylmercury in ethereal solution give mercuric cyanide at 50°C, and mercuric iodide and methyl isonitri le at I lO 0 C [283].

Cyanogen bromide does not cleave the C-Hg bond but replaces the X in RHgX by bromine, as has been shown on the example of a -acetoxymercuri-/3-methoxy-j3-phenylethane [284].

In a few cases the organomercury compound reacts with the organic halide with abstraction of the corresponding hydrogen halide and formation of an unsaturated compound:

2RC2H—CXR2 -I- R12Hg 2R2C = CR2 + HgX2 2R'H

Such reactions have been observed for t-butyl bromide [246] and t -amyl iodide [246] with diphenyl- and di- jp-tolylmercury, and for l -bromo- l , l ,2- tr icarbethoxyethane [246], neopentyl bromide and neopentyl iodide [285] with d i -^- to ly lmercury . The yields are extremely small and the conditions vigorous - boiling for 340 hours in toluene [246] or many hours of heating in a sealed tube at 200°C or at a higher temperature [285].

9-Bromofluorene reacts according to the scheme

2RC2HBr + 2R'2Hg - R2C = CR2 + 2R'H + 2R'HgBr

with the formation of bis-diphenylene ethylene [246]. When d i -p- to ly lmercury is boiled for 340 hours in toluene with

stilbene dibromide, the halogen is split out and an unsaturated compound is formed [246]:

C6H5CHBrCHBrC6H5 + R2Hg =< C6H5CH= CHC6H5 +RBr + RHgBr

However, in most cases organic halides do not react at all with organomercury compounds [246] (18 out of the 32 RX tested), even after 300-350 hours of boiling in toluene.


The action of alkyl halides (methyl iodide) on the products of the addition of mercuric salts to ethylene is characteristic: it leads to liberation of the ethylene [286, 287]. The action of acyl halides on ^S-hydroxyalkylmercury [288] and /3-alkoxyalkylmercury [289] halides also results in the formation of an unsaturated com-pound. For the reaction between alkyl halides and the adducts of mercur ic salts with olefins see also Chapter 6. Razuvaev et al. [290] described the reaction of CCl4 and methanol in the presence of diphenylmercury. The photochemical reactions between organo-mercury compounds and organic halides are given later in this chapter. The reaction of divinylmercury with methylene iodide in the presence of Zn or Cug i v es dicyclopropylmercury [64a].

j ) The Action of Reducing Agents on Organomercury Compounds, in

Particular the Reaction with Metals

The cycle of reactions expressed by the scheme

I-R2Hg + M" - y Hg + RnM" (1)

(where M is a metal n-valent in its organometall ic compounds) is used widely for the preparation of the organometall ic derivatives of various elements, for which it is the main and sometimes the only method of synthesis.

One of the simplest cases of reaction (1) is the isotope exchange between R2Hg and labeled mercury (see later in this chapter).

The interactions between dialkyl- or diarylmercuries and L i , Na, Be, Mg, Zn, Cd, A l , Ga, In, Sn, Bi, or Te lead to the formation of full orgamometall ic compounds of these metals, and the reaction of cyclopentadienylmercury compounds with Fe gives ferrocene.

With the most reactive metals (L i , Na) the reactions proceed at room temperature or slightly higher temperatures (e.g. below IOO0C). Other metals require temperatures of 120-230°C and the reactions are conducted in the melt or , more conveniently, in solution, for example in xylene. The aromatic organomercuries enter into these reactions more readily than the aliphatic, and the latter are utilized to a much smaller extent. On heating, the reaction is complicated by the decomposition

R2Hg - R2 + Hg

which is so pronounced in the case of dibenzylmercury and analogous compounds that the latter compound is rare ly used to prepare the organometall ic derivatives of the heavy metals (Sn). Benzyl-l ithium and benzylsodium are obtained normally. The choice of the solvent is important; it should be inert to the mercury compounds under the reaction conditions, to the desired organometall ic product, and



of course to the starting metal. From the point of view of the f i rst of these conditions, it should be remembered that at high tempera-tures many substances capable of dehydrogenation, such as the alcohols [292-294] (also those containing D [299]), hydroquinone [292], tetralin [294], or hydrazobenzene [418] convert the R2Hg into RH and Hg.

The source of hydrogen reducing the forming radicals may be secondary or tertiary alcohol groups in the organic part of the organomercury molecules [295]. The organomercury salts react in the same way with the alcohols [296-298], with the formation of RH and metall ic mercury. The hydrogen does not originate f rom the alcoholic hydroxyl group [299].

Apart f rom the above, RHgCl and R2Hg are reduced to RH and Hg by triethylsilane [300], LiAlH4 [21, 99a, 301, 303], NaBH4 [302] and NaBH(OCH3)3 [105]. For the last three of these the reaction proceeds via intermediates L iA lR 4 [303] or LiAlH2R2 and NaBr4 , respect ively, which are then hydrolysed by dilute acid. Reactions of this type can be used for the elimination of mercury where this cannot for some reason be done with the aid of HCl.

Reduction of diphenylmercury with lithium tetrahydroaluminate [301]. Diphenyl-mercury (3.5 g) in ether is treated with an excess of LiAlH4 . Mercury separates out immediately. The mixture is boiled for 30 minutes and the mercury fi ltered off; its weight is 1.93 g (theoretical amount, 1.95 g). The ethereal solution is washed with dil. H2SO4 and water, and then dried over sodium sulfate. The ether is then distilled off through a Vigreux column. The residue, crystallizing on freezing, is benzene (m.p. +2°C).

Preparation of the lactone of 2,a-hydroxybicyclo-(2,2,1)-heptane-6,arcarboxy 1 ic acid

The lactone of 5,/3-chloromercuri-6, a-hydroxybicyclo-(2,2, l)-heptane-2, a-carboxy-Iic acid (17 g) in 50 ml of a 1:3 mixture of ether and methanol is refluxed for 3 hours, with stirring, with 3.8 g of sodium tetrahydroborate. Hydrochloric acid is then added and the product extracted with ether and recrystallized from light petroleum ether. Yield: 5.8 g (80%); m.p. 154-155°C.

The XHg group is replaced by H in RHgX, in particular in the adducts of mercuric salts and unsaturated compounds, by the action of such reducing agents as sodium amalgam in alkaline solution, hydrazine hydrate, sometimes H2S, and also electrolyticai ly (see Chapter 11).

Preparation of cyclohexane-l/3,4a-diol [302].

[302],

ClHg OH OH


To a boiling solution of 10.7 g of 3/3-chloromercuricyclohexane-1/3,4 a-diol in 85 ml of aqueous NaOH are added 5.5 ml of hydrazine hydrate. The mixture is boiled for 16 hours. The product is extracted with ethyl acetate and recrystallized from acetone. Yield: 2.95 g (90%); m.p. 138.5-140°C. The melting-point of the dibenzoate is 150-151°C.

The action of hydrazine on mercarbide (4 hours of boiling) leads to full replacement of mercury by hydrogen and to the formation of ethane according to [46] and of methane according to [47].

The replacement of mercury by hydrogen in di ferrocenylmercury is a somewhat dif ferent reaction. Thus, heating of d i ferrocenyl -mercury for 15 hours in boiling benzene with metall ic sodium gave a 10% yield of f e rrocene [281]; mosto f the d i ferrocenylmercury did not react.

A 15% yield of ferrocene was also obtained, and mercury was detected, after the interaction between di ferrocenylmercury and SnCh for 15 hours in ether. Again most of the organomercury did not react [281]. As was already shown above, the solvent in r ea c -tions of this kind should be inert to the metal and to the produced organometall ic compound; this must be borne in mind in syntheses of organometall ic substances containing active hydrogen (OH, NH2

groups), i .e. especially in the synthesis of the organic compounds of the alkali metals.

Alkylsodiums react also [304, 305] with aromatic hydrocarbons (and heterocycles of the type of furan and thiophene) according to the schemes

RNa + C6H6 - » C6H5Na + RH

RNa + C6H5CH3 - C6H5CH2Na + RH

RNa + I^ J - > ( I^JJ x + R H

S S Na

These reactions l imit the choice of solvents in the synthesis of the alkyl derivatives of the alkali metals, but they also make possible a synthesis of the aryl , ar alkyl and heterocycl ic derivatives of these metals f r om alkylsodiums obtained f rom organomercuries.

The reactions described in this section include the interactions between ary lmercury chlorides and metal l ic tin [307] (a method of synthesizing tetra-arylt ins) and the reaction with B i -Na alloys [308] giving diphenylmercury and triphenylbismuth.

In conclusion, it may be mentioned that nonmetallic elements -hydrogen (at a high temperature and pressure [292]), sulfur [237, 309, 310], selenium [237, 310, 311], tellurium [237, 310, 421] and the halogens - enter also into reactions of this type, removing the radical f rom the organomercury; the di f ference is that in the case of S, Se, T e and the halogens the mercury combines with the excess of these elements:

R 2 H g + 2 E - R 2 E + H g E



where E = S, Se, T e , + X2

R2Hg + X2-* RHgX + RX » RX + HgX2

Trans f e r of radicals f r o m the organomercury compounds to the reducing molecules has been much less studied. The reactions of SnCl2 and SnBr2 with R2Hg and RHgX, proposed by Nesmeyanov and Kocheshkov [423] (a ve ry convenient method of synthesizing organotins R2SnX2) belong to this category, as do the reactions of R2Sn and R3Sn-SnR3 with d iary lmercur ies , accompanied by t ransfer of radicals to the tin atom and formation of asymmetr ica l R2SnR2 ' and R 3 SnR ' [314 ] .

Other reactions of this type are those of GeI2 with d i a r y lme r -cur ies , which lead to mono- , d i - and t r iary lated compounds of germanium. Details concerning the range of application and the conditions under which these reactions are car r i ed out wi l l be indicated in succeeding sections.

It is pract ical ly certain that the principle underlying the above examples of synthesis must have a more general s igni f icance, and that compounds such as CrC l 2 or VCl2 , and other suff iciently strong reducing agents, should also be capable of splitting radicals away f r o m organomercury compounds. However , the choice of the r e -action medium remains an unavoidable di f f iculty, since water and alcohols, capable of yielding their hydrogen under the influence of the reducing agent, would probably cause the radicals R to split of f in the f o rm of RH (see the section on the reactions of organo-mercury compounds with SnCl2).

The interaction of arsenobenzene with diethylmercury, giving phenyldiethylarsine and mercury [315, 316] should also be men-tioned in this context.

The Ac t i on of Meta l s without the F o r m a t i o n of O r g a n o m e t a l l i c C o m p o u n d s

Cu, Ag , Au, the r a r e earths, T i , Z r , Hf, V , Nb, Ta , C r , Mo, W, U, Mn, T c , Re , Co, Ni , Pa , Rh, Pd, Os, Ir , P t , and in all probabil ity Ca , Sr, Ba, Ra, Sc and Y are incapable of fo rming organometal l ic compounds f r o m organomercur ies . Heating of fully substituted organomercury compounds with some of them (Pt , Pd [294, 317], A g [318-322]) mere ly catalyzes the decomposition

R2Hg R2 + Hg

somet imes (Pd) sharply lowering the required temperature.

Decomposition of diphenylmercury with metallic palladium [317]. A mixture of 1 g of diphenylmercury and 0.5 g of Pd obtained by precipitation from one of its salts by formalin is heated for 12 hours at IOO0C in a sealed tube and then extracted, f irst with ether and subsequently with benzene. Evaporation of the ethereal extracts gives 0.37 g


(86%) of biphenyl, purified by sublimation; m.p, 69°C. The benzene extracts give, after evaporation, traces of diphenylmercury. The weight of mercury washed with ether and benzene is 0.5322 g (94.2% decomposition).

Heating of the tetramer ie o-biphenylenemereury with Ag powder to 300 0C gives biphenylene in a yield of 54% [320]:

Dimer ie o-terphenylenemercury heated with Ag powder for 10 minutes at 280°C under an atmosphere of nitrogen gives a 71% yield of triphenylene [319]:

Similar ly, a 55% yield of biphenylene was obtained f r om hexameric o-phenylenemereury and s i lver at 260°C [318]:



(in high vacuum, 9.5% of triphenylene was also f o rmed ) . 3,4-Benzobiphenylenemercury heated with Ag powder to 360°C

tinder nitrogen gave a 16.8% y ie ld of 3,4-benzobiphenylene ( isolated as a complex with 2,4,7-tr initrof luorenone [231]):

On the other hand, the react ion between d i f e r roceny lmercury and Pd black [323] gave only traces (1-6%) of b i f e r roceny l . The latter was prepared in 43-54% yie ld (together with f e r rocene ) when Ag powder was used for the decomposition of the d i f e r roceny lmercury [322]:

C5H5FeC5H4HgC5H4FeC5H5 ^ C5H5FeC6H4C5H4FeC5H5

The formation of b i f e r roceny l occurs when the react ion is ca r r i ed out at a temperature not lower than 265°C [322] (eightfold molar excess of s i l v e r , heating f o r 17 hours); in the absence of s i l v e r the main product of the thermal decomposit ion (at 265°C) is f e r rocene . Combined decompositions of d i f e r roceny l - and d ia ry lmercur i es with s i l v e r (molar reactant rat io 1:1:15, 17-22 hours at 235-300°C) gave a ry l f e r rocenes with the fo l lowing yie lds: phenyl ferrocene 45%, 2 -biphenyly l ferrocene 6%, 3-biphenyly l ferrocene 22%, 4-biphenylyl-f e r r ocene 20% [322].

Heating of the po lymer ic compound ( -C 5H 4FeC 5H 4Hg- ) (mentioned in Chapter 13), obtained by symmetr izat ion of 1 ,1 -d ich loromercur i -f e r rocene , with Ag powder to 300°C leads to the format ion of po ly -f e r roceny lene , as wel l as t races of f e r rocene and b i f e r roceny l [327].

Preparation of biphenylene I I I [320]. A mixture of 2.7 g of tetrameric

biphenylenemercury and 6 g of Ag powder is heated to 296-300°C on a metal bath in sublimation apparatus. After an hour crystals of biphenylene appear on the cold finger; these are removed from time to time. Yield: 54%; m.p. 107-109°C. Chromatography of a solution of this product in petroleum ether through an alumina column raises the melting-point to 109.5-111°C. A picrate, m.p. 122°C, is obtained.

Phenylmercury acetate g ives biphenyl already in aqueous alkaline solution of treatment with a nickel-aluminum alloy [324].

Syn the s i s of the O r g a n o m e t a l l i c D e r i v a t i v e s of

S o d i u m a n d Lithium from O r g a n o m e r c u r i e s

Fully substituted organomercury der ivat ives of aliphatic and aromat ic hydrocarbons react with L i and Na to g ive L i and Na


alkyls and aryls [325]:

R2Hg + 2Li ( N a ) 2 R L i (Na) + Hg (1)

The reactions are usually carr ied out in l igroine or gasoline, some-t imes in ether. The aromatic and aliphatic-aromatic compounds are synthesized in benzene.

In view of the extreme sensitivity of the simpler alkyl-Iithivims and alkylsodiums toward oxygen, moisture and carbon dioxide, reactions (1) [above] and (2) [below] are conducted under oxygen-f r e e , dry, very pure nitrogen in special apparatus.

Thus, for example, ethyl [325], n-propyl [325], n-butyl, isoamyl and 3-n-heptyl [326] lithium derivatives have been prepared, as wel l as vinyl-lithium (reaction in pentane [142] or in ether [158]) and butylethynyl-lithium ( from dibutylethynylmercury and lithium, in dioxan [328]).

Phenyl-Iithium has been made in benzene [325, 329] and in ether [359], and o-, m-, and p-tolyl-l ithiums [330] in ether; o-dil ithio-benzene has been prepared after shaking of hexameric o-phenylene-mercury with lithium in ether for several days [318], as well as o -Iithiobiphenyl f rom tetrameric o-biphenylylmercury and lithium [331] and 2,2'-di l i thio-o-terphenyl f rom o-terphenylenemercury and lithium [319].

In the presence of a I i t t leAlkLianexchange occurs [332] between organomercuries and organic halides:

A I k L i

R2Hg + 2R' I Z=T R'2Hg + 2RI

with intermediate formation of organolithiums:

R2Hg + 2R'Li «2 R'2Hg + 2RLi

2R'I + 2RL i^2RI + 2R'Li

isolated, for example in the case when R was benzyl [354]. In the case of sodium, methyl [325], ethyl [333, 335, 337] and n-

propyl [325, 336, 338] derivatives have been reported, as wel l as s-butylsodium (isolated after carboxylation in the f o rm of methyl-ethylacetic and methylethylmalonic acids [339]), amylsodium [334], octylsodium [325] and benzylsodium [325].

Benzylsodium and benzylpotassium are made starting f rom any isomer of ditolylmercury; when the initially formed tolylsodium (po-tassium) is heated, the metal atom migrates to the side chain [338].

Vinylsodium and vinylpotassium have been prepared f rom divinyl-mercury and the corresponding metal in pentane [142]. Phenyl-sodium [325, 341] (see [342]) and furylsodium [306] have been obtained. Complexes (R 2Li )Me [329a, 330, 343] (where R is alkyl or aryl) are formed when R2Hg and RL i are shaken with an alkali metal (Na, Cs) in ether, via intermediate alkali-metal organo-metal l ics. In the case of potassium the shaking operation is carr ied



out not with this metal itself , which displaces lithium f rom organo-metal l ic compounds, but with an Na-K alloy [330].

Since dimethylmercury reacts only slowly with metal l ic lithium with the formation of insoluble CH3Li , separating according to r e -action (1) and contaminated with the metal, methyl-lithium is more conveniently prepared by the double exchange:

(CH 3 ) 2 Hg + 2 A l k L i 2CH 3 Li + A l k 2 H g ( 2 ) insol . inso l . s o l . inso l .

The action of solutions of L i or Na in liquid ammonia on the mercury derivatives of aldehydes or ketones results in vinyloxides of these alkali metals [344]:

Hg (CH2CHO)2 + Me/NH3 Me/Hg + CH2 = CHOMe

(where Me = L i , Na). Phenyl-Iithium can be made either by the reaction of L i with

diphenylmercury, or (and this is the experimentally s impler method) by the reaction of diphenylmercury with ethyl-lithium.

Transmetallations of chloromercuri ferrocene with ethyl- [345], n-butyl- [322, 345] and phenyl-lithium [345], and of d i ferrocenyl -mercury with n-butyl-lithium [345], gave, respect ively, 90, 50, 58 and 43% yields of ferrocenyl- l i thium. The reactions were carr ied out in ether, at 0°C.

The transmetallation of 1 ,1 ' -b is- (chloromercuri ) ferrocene with ethyl-lithium in ether at room temperature resulted in l , l ' - f e r r o -cenyldilithium in a yield of 44% [345] (the yields were calculated f r om the formation of carboxylic acids after carboxylation).

In several syntheses proceeding via organosodiums there is no need to isolate the latter f rom the reaction mixture. Thus, Schorygin [346] per formed the fol lowing syntheses:

(1) (C2H5)2Hg + Na + C6H5COC6H5 - (C6H5)2C2H5COH (2) (C2H5)2Hg + Na + C6H5COOC2H5 -* C6H5 (C2H5)2COH (3) (C2H5)2Hg + Na + C6H5CHO - C6H5C2H5CHOH (4) (C2H5)2Hg + Na + CO2 - CH3CH2COOH (5) (CH3)2Hg + Na + CO2 - CH3COOH (6) (iso - C5H11J2Hg + Na + CO2 - iso - C4H9CH2COOH

by adding the second component to the mixture of dialkylmercury and sodium. Reactions (1-6) were carr ied out in ether.

The action of CO2 on a mixture of sodium and diethylmercury or diamylmercury in pentane or l igroine gives the alkylmalonic acid in addition to the monocarboxylic acid [334].

If one works with a mixture of dialkylmercury and sodium in an aromatic hydrocarbon, the solvent participates in the reaction and


the action of CO2 at room temperature g ives r i s e to an a r y l ca rb -oxy l i c acid [304], and at low temperature also to a d icarboxyl ic acid [334] ( for example, a mixture of isophthalic and terephthalic acids are f o rmed in benzene [334]). In work with benzene homologs the carbon dioxide enters into the side chain; thus toluene g ives phenylacetic acid [304] (plus phenylmalonic at lower temperatures [334]) , m-xylene g ives m-tolylacetic acid [304], ethylbenzene hydratropic acid [304], o-xy lene o- to ly lacet ic acid [305], ^-xy lene P - to ly lacet ic acid [305], mesi ty lene 3,5-dimethylphenylacetic acid [305], diphenylmethane diphenylacetic acid [305] and p-cymene P -homocuminic acid [305].

When the react ion is car r i ed out in thiophene, furan, a -methy l -furan, or a-methylthiophene, the acid product is a-thiophenecarb-oxy l i c [305], a - furancarboxy l i c [306], 2 ,5-methyl furancarboxyl ic [306], or 2,5-methylthiophenecarboxyl ic [306] acid; the y ie lds are higher than for the i socyc l i c hydrocarbons.

In the action of sodium on diethylmercury in ethers, the latter a re decomposed by the forming ethylsodium to g ive sodium alkox-ides [347], for example:

C2H5Na + (C2H5)2O - C2H5ONa + C2H6 -J -C2H4

Synthes i s of O r g a n o m e t a l l i c C o m p o u n d s of Me ta l s of

G r o u p Il of the Pe r i od i c Tab le

Bery l l ium, magnesium, zinc, and cadmium react with ful ly substituted mercury compounds according to the scheme

R2Hg + Me — R2Me + Hg

Th i s is the most convenient method of prepar ing, in individual state, ful ly substituted aliphatic compo unds of Mg and aromatic compounds of Be , Mg and Zn. Tne reactions should be ca r r i ed out in an inert atmosphere (nitrogen, argon, also carbon dioxide in the preparat ion of the organozincs) . Heating of d ia lky lmercur ies with meta l l i c Be in a sealed tube at 130°C resulted in the format ion of d imethyl -bery l l ium [349-353] (including dimethylberyl l ium containing 'Be [351]), diethylberyl l ium [355, 356] (see [357] ) , d i -n-propy lbery l l ium and di-n-butylberyl l ium [355, 356].

Apparatus f o r the synthesis of d imethylberyl l ium (not in a sea led tube) has been descr ibed [351]. The preparat ions of d i a ry l -bery l l iums require higher temperatures and the addition of a cata-lyst: diphenyl- and d i -p - to l y lbe ry l l ium have been obtained by heating d ia ry lmercur i es to 225°C for 6 hours, in a sealed tube, with equi -valent amounts of Be, in the presence of t races of HgCl2 [357]; diphenylberyl l ium has been made in the presence of BeBr 2 (72



hours at 170°C) [358] and by heating diphenylmercury with Be in xylene for 72 hours at 150°C [359, 360].

Preparation of diphenylberyllium 1.359, 360J. A mixture of 9 g of diphenylmercury, 0.8 g of Be and 25 ml of dry xylene is heated in a sealed tube for 72 hours at 150°C. All manipulations are carried out under nitrogen. The xylene is distilled off under vacuum and the diphenylberyllium dissolved in 50 ml of absolute ether and filtered off from the Be amalgam. Concentration and cooling of the ethereal solution give cubic crystals melting into a yellowish liquid at 28-32°C. The preparation loses ether only at 130°C under vacuum and then melts (with decomposition) at 160-165°C. Yield: 86% [360],

Dialkylmercuries heated with magnesium for several hours in a sealed tube gave dimethylmagnesium (35 hours at 120-130°C [361]; 24 hours at 95-105°C, triply sublimed Mg [361a]), diethylmagnesium [361] (according to Gilman [362], only in the presence OfHgCl2 ) , di-n-butylmagnesium (heating for 10 hours [363]) anddi- (2-methyl-butyl)magnesium [364]. Diethylmagnesium (in a yield of 81%), dipropylmagnesium (89% yield) and di-isopropylmagnesium (in various yields) were obtained [348], without isolation f rom their ethereal solution, by the reactions of R2Hg with Mg for 24 hours at 115-120°C in sealed tubes, under nitrogen. Diphenylmagnesium is made by heating diphenylmercury with magnesium to 200°C for 5-6 hours [342, 365, 366] (in the presence of ethyl acetate to 180-185°C), preferably in the presence of a little HgCl2 as a catalyst [367]. Diethyl- and diphenylmagnesiums are also obtained after prolonged shaking of an ethereal solution of the corresponding R2Hg with magnesium [368].

Heating of dialkylmercuries with Zn in a sealed tube to 120-130°C for several hours, or prolonged heating on a water bath, gave dimethylzinc (24 hours at 120°C, also by boiling dimethyl-mercury with granulated zinc) [368], diethylzinc (36 hours at 100°C) [369], di-n-propylzinc [370, 371], di-isobutylzinc (120-130°C [372, 373], 36 hours [373], 60 hours on a water bath) [374, 375] and di- isoamylzinc (36 hours at 130°C) [369].

A simple and convenient method of synthesizing fully substituted aromatic derivatives of zinc, allowing in particular the preparation of diarylzincs with substituents in the benzene ring, is to boil a diarylmercury in xylene with metall ic zinc (Kocheshkov et al. [376]). This method has been used to make diphenyl-, d i -p - f luoro -phenyl-, d i-p-chlorophenyl- , d i - o - to l y l - , di-p-dimethylamino-phenyl- and dinaphthylzinc. In the case of diphenyl-, d i -p -ch lo ro -phenyl- and di- p-dimethylaminophenylzinc the reaction is completed within 2-3 hours. Di -o- to ly l z inc requires 5-6 hours. D i -p-carbeth-oxyphenylmercury does not react at all with zinc, even on heating in a sealed tube to 210°C.Di-p-bromophenyl-anddi-?>-iodophenyl-mercury do not react with zinc on boiling in xylene and on heating to 220-230°C with zinc and xylene in a sealed tube they decompose without forming organozinc compounds. Dibenzyimercury heated with zinc to I lO c C gives bibenzyl, either in xylene or in the absence of solvent.


Preparat ions of diphenylzinc have also been descr ibed by Gi lman [377] and Hi lpert [342].

With meta l l i c cadmium, diethylmercury g ives at 100-130°C a mixture of diethylcadmium and diethylmercury [369]. A f t e r heating d imethyl - and diethylmercur ies with Cd to 200°C in a sealed tube, Lohr [361] was unable to isolate organocadmium compounds. The diphenylcadmium forming in the interaction of diphenylmercury and Cd could not be isolated f r o m its isomorphous mixture with d i -phenylmercury [342].

For the preparat ion of diphenylcadmium see [378].

S y n t h e s i s of the O r g a n o m e t a l l i c C o m p o u n d s of M e t a l s of G r o u p III of the Periodic Tab le

Fully substituted mercury compounds react with A l , Ga and In according to the react ion

3R2Hg + 2Me - 2R3Me + 3Hg

which provides a means of synthesizing organometal l ic der ivat ives of these meta ls . Some fully substituted aliphatic compounds of A l , Ga and In and aromat ic compounds of A l we r e f i r s t obtained by this method.

The fo l lowing aliphatic compounds of aluminum were prepared by heating d ia lky lmercur ies with A l shavings in n i t rogen- f i l l ed or evacuated sealed tubes, to 100-130°C for severa l hours: t r i -methylaluminum [379-383], (also by boil ing dimethylmercury with A l [368a]) triethylaluminum [379, 381-385], t r i -n-propyla luminum [5, 356, 370, 382, 384], tr i - isopropylaluminum [384] (this substance was actually [386] a mixture of t r i -n -p ropy l - and t r i - i s op ropy l -aluminum, since the secondary Alk 3Al rearrange into p r imary ones on heating), a mixture of t r i - s -buty l - andtri-n-butylaluminum[386] (start ing f r o m d i -s -buty lmercury [386]), tr i -n-butylaluminum[356] and tr i - isoamyla luminum [382, 287],

(+)- [C3H7CH(CH3 )CH2 ]2Hg and the corresponding racemic R 2Hg g ive (+J-R3Al and the racemic R 3 Al , respect i ve ly , on heating f o r 3 days with aluminum in iso-octane [353].

So lvent - f ree trivinylaluminum has been made [149, 388] f r o m granulated meta l l ic aluminum and div inylmercury in pentane.

The react ion of lithium tetrahydroaluminate with an excess of d iv iny lmercury g ives L iAl (C 2H 3 ) 4 [149, 388].

The action of L iA lH 4 on 4-camphenylmercury chloride in absolute ether (5 hours at 0°C, then 12 hours at 25°C) after decomposit ion with water gave a 19% yie ld of camphane [21].

The react ion between AlCl3.N(CH3)3 (1 mole ) in ether and div inyl -mercury (1.75 moles ) g ives (CH2=CH)3ALN(CH3 )3 [388]. (CH2=CH) AlH2 .N(CH3 )3 has been obtained f r o m 1 mole of (CH2=CH)2Hg and 2 mo les of AlH3 lN(CH3 )3 [388].



On the other hand, a Fr i ede l -Cra f t s reaction occurs during the in-teraction between RHgCl (R = C6H11, 6 hours; S-C4H9, 15hours) and AlCl3 in benzene, so that the product is the alkylbenzene (75% yield) and metal l ic mercury (in the f i r s t of these cases also Hg2Cl2) [105].

The interaction between diperf luorovinylmercury and aluminum hydrate-thimethylamine in ether g ives tr is- (per f luorov inyl )a lum-inum-trimethylamine (CF2=CH)3ALN(CH3 )3 [3891.

Preparation of lithium tetravinylaluminate [388]. Divinylmercury (11.4 g, 0.045 mole) is condensed onto 7.6 g (0.02 mole) of LiAlhU (crystalline, 100 mesh) in 100 ml of dry ether and the reaction mixture slowly heated to room temperature, stirred for 16 hours, set aside overnight and then fi ltered under nitrogen; 0.0399 mole of hydrogen is evolved during this time. The ether is distilled off under vacuum and the soluble soft residue ex-tracted with a few portions of benzene. Cooling yields a white precipitate, which is f i l -tered off and dried under vacuum.

After recrystallization from benzene, the product forms fine white needles with a decomposition point of 180°C. The substance is pyrophoric and ignites in air throwing off sparks.

Of the aromatic fully substituted compounds of aluminum, t r i -phenylaluminum [377, 390-393] (also the same compound containing 14C [394]) and tr i -p-to ly la luminum [395] have been made f r om the corresponding d iary lmercur ies and A l .

Boil ing of d iary lmercur ies with metal l ic aluminum in xylene or some other indifferent solvent, such as toluene, octane, or in certain cases dekalin, provides a method of synthesizing aromatic com-pounds of aluminum [396], This method has been used to prepare tr iphenyl- [396, 397], t r i - o - t o l y l - , t r i -m- t o l y l - , tr ipseudocumyl-, t r i - o - a n i s y l - , t r i -p- f luoropheny l - , t r i -p-ch loropheny l - , t r i - a -naphthyl- and tri-p-biphenylaluminum [396]. Boiling of d i - o -phenetyl- and di-/3-naphthylmercury with A l in an octane-nonane fract ion of motor fuel gave r i se to viscous colloidal solutions f r om which organoaluminums could not be isolated. Di -o-ch loropheny l -and d i - p-dimethylaminophenylmercury decompose on being boiled with A l in xylene o r nonane, not giving r i s e to organoaluminum compounds. D i -p -an i sy l - , d i -p-phenety l - , d i -p-carbethoxyphenyl-and di-p-carbmethoxyphenylmercury do not react with metal l ic A l at all on boiling in xylene or even in dekalin [396].

T rans fe r of radicals f r om mercury to aluminum occurs also in the room-temperature interaction between L iA lH 4 in ethereal solu-tion and diphenylmercury, leading to LiAlH2 (C eH5 )2 andLiAl(C6H5 )4, identif ied by the formation of phenylmercury chloride with HgCl2

[303]. Decomposition of the reaction mixture with acid g ives ben-zene [301].

A good y ie ld of tr imethylgal l ium is obtained when metal l ic gall ium is heated for 91 hours at I lO 0 C, in a sealed vesse l , with dimethyl-mercury in the presence of Hg [398]. The same reaction has been ca r r i ed out by boiling for a few hours in an open tube [399] in the presence of t races of mercur ic chloride.

Pro longed heating of diethylmercury to 165°C with an excess of


meta l l i c gal l ium, in a sealed vesse l , under nitrogen, gave t r i -ethylgal l ium [400], the f i r s t ful l organogal l ium compound.

Tr iv iny lga l l ium has been obtained f r o m div iny lmercury and an excess of meta l l ic Ga after 24 hours of react ion at r oom t empera -ture in a nitrogen atmosphere [401].

Tr iphenylgal l ium has been made [393, 402] f r o m diphenylmercury and Ga under the conditions used f o r the synthesis of t r imethy l -and tr iethylgal l ium ( for 50, or better st i l l 75, hours at 170°C in a sealed tube, under nitrogen) ; the melt ing-point of this compound is 166°C [402].

The interaction between meta l l ic indium and d imethylmercury in the presence of a l i tt le HgCl2 , or better HgCl2 and t races of iodine and magnesium [403], at 100°C, under carbon dioxide, y ie lded tr imethyl indium [404].

Y i e lds of up to 80% of triphenylindium (m.p. 208°C [406]) have been obtained by heating diphenylmercury and In f o r 50 hours at 130°C in a sealed vesse l , under CO2 [405] or better nitrogen [393, 406].

Heating of 1.5 g of In with 2.25 g of diphenylmercury f o r 30 min -utes to 270°C, under nitrogen at a pressure of 17.2 mm, gave a f ter cool ing, extraction with ether, and evaporation of the latter , an oi l which so l id i f ied upon the addition of petro leum ether. Repeated dissolution in ether and precipitat ion with petro leum ether gave the substance CeH5InOJn2O3 [150] not melt ing up to 290°C.

Syn thes i s of the O r g a n o m e t a l l i c C o m p o u n d s of

E lements of G r o u p IV of the Periodic Table

Preparat ion of o r gano s i l i c on d e r i v a t i v e s . The interaction of (C6H5 )3SiLi with Ar 2 Hg (Ar = C6H5 and P-CH3C6H4 ) and C6H5HgBr (in tetrahydrofuran, at r oom temperature) g i ves r i s e to (C6H5 )3SiAr, [(C6H5)3SiJ2, (C6H5)3SiOH and some meta l l ic mercury [407].

Preparat ion of o r g a n o g e r m a n i u m de r i va t i ve s . Me ta l l i cme r cu ry separates out f r o m the react ion between GeI2 and diethyl- or d i -n -buty lmercury; in the latter case an organogermanium compound was also isolated to which the structure [(C4 H9 J2GeJ2 has been ascr ibed [408].

The interaction between d ia ry lmercur i es and GeI2 al lows syn-thesis of the aromatic compounds of germanium [409, 410]. The react ion occurs when equimolar proport ions of the reactants are b r i e f l y boiled in toluene. The main products are diarylated com-pounds of germanium, f o rmed in y ie lds of 40-70%; these are the only products on the case of o-substituted ary ls . Ar 3 GeI and ArGeI 3

are also f o rmed in certain cases. This react ion has been ca r r i ed out f o r A r = phenyl, o-, m- and p-to ly l , o-, m- and p-chlorophenyl , o- and p-bromophenyl , p-anisy l , o- and p-phenetyl and a-naphthyl.



The interaction of diphenylmercury with germanium di-iodide [410]. A mixture of 3.55 g (0.01 mole) of (C6H5 )2Hg and 3.26 g (0.01 mole) of GeI2 is boiled for 15 minutes with 30 ml of sodium-dried toluene, in a flask fitted with a reflux condenser closed by a CaCl2 tube. Grayish-black, finely divided mercury begins to separate even before the toluene boils, and the golden-yellow GeI2 is consumed. Greenish-yellow flakes gradually precipitate out. After cooling of the reaction mass, the solids are f i ltered off and washed with two small portions of toluene. Treatment of the material with KI solution quickly destroys the greenish-yellow substance. Reaction with ammonia shows that the filtrate contains the H g 2 + ion. After washing with water, 0.07 g of CeH5HgI (m.p. 260-262°C) is extracted from the residue with acetone. NaOH (10%) is then used to extract GeO2, which is precipitated out with H2S in the form of GeS2 from the fi ltrate acidifed with conc. HCl. Droplets of metallic mercury remain on the filter. To decompose the organomercuries and remove the inorganic mercury iodides, the toluene filtrate is shaken up in a separating funnel f i rst with iodine-colored HI (sp. gr. 1.7) (until the acid is no longer decolorized) and then with colorless acid to extract the iodine dissolved in the toluene. The toluene is next removed under slight vacuum, by heating on a water bath, leaving behind a pale-yellow oil which, on cooling, yields 0.37 g of a colorless substance; m.p. 137-157°C. Following recrystallization from nitromethane and subsequently from n-heptane, the melting-point becomes 155-157°C. After separation of (C6H5)SGeI, the liquid portion of the residue is resolved by distillation under a pressure of 2 mm into two fractions. The f irst of these, a pale-yellow liquid (b.p. 152-155°C) weighs 0.9 g; the second, a pale-orange liquid (b.p. 160-161.5°C) amounts to 1.55 g.

The f irst fraction does not crystall ize on cooling and hydrolyses on heating with 20% NaOH (with 15-20 ml of alcohol added first). This reaction yields 0.16 g of colorless (C6H5 )2GeO (m.p. 283-293°C) insoluble in organic solvents. Acidification of the alkaline fi ltrate with HCl gives 0.05 g of yellowish flakes. The substance is purified by repeated dissolution in alkali. This procedure results in the isolation of 0.02 g of phenylgermanic acid anhydride. The second fraction crystallizes on cooling, giving 1.1 g of yellowish substance melting at 56-61°C. Twofold recrystallization from nitromethane and a single one from n-heptane results in colorless crystals of (C6H5 )2Gel2 (m.p. 63-65°C). The yields of these products, calculated on the phenyl used up, are as follows: (CeH5 )2GeI2

39% (0.004 mole), (C6H5 )8GeI 37% (0.0016 mole) and C6H5Gel3 0.5%.

Prepara t ion of o rganot in der i va t i ve s . Meta l l i c tin interacts with a ry lmercury and alky lmercury chlor ides in boil ing toluene according to the react ions

6ArHgCl + 3Sn 3Ar2SnCl2 + 6H (1)

3Ar2SnCl2 — 2Ar3SnCl + SnCl4 (2)

SnCl4 + Sn -> 2SnCI2 (3)

with the format ion of t r iary l t in chloride [307]. Chlor ides of t r i -phenyl- , t r i - p - t o l y l - , t r i -p -carbethoxypheny l - , and tr ibenzylt in have been made in this way in y ie lds of up to 70%. The interactions between ary lmercury chlorides and a 15% Na tin-sodium alloy in boi l ing xylene g ive te t ra-ary l t ins and hexa-aryldi t ins:

6ArHgCI + 3Na2Sn - 3Ar2Sn-f 6NaCl + 6Hg (4)

3Ar2Sn -* Ar3Sn -SnAr3 + Sn (5)

Ar3Sn-SnAr3-^Ar4Sn + Ar2Sn (6)

Te t rapheny l - , t e t ra - p - t o l y l - and te tra-p-chlorophenyl t in have been synthesized in this way [307],

Diphenylmercury boi led in xylene with meta l l i c tin g ives a 28.6% y ie ld of tetraphenyltin [307]; the y ie ld can be ra ised to 100% by


carrying out this reaction in the absence of solvent, in a sealed tube, at 200°C [411] (see [342]). They i e ldo f t e t rapheny l t inobta inedby heating diphenylmercury in xylene solution with an Sn-Na alloy is low [307].

Stereoisomeric ethylenic organomercuries, cis-, and trans-(fi-chlorovinyl)mercury chlorides, react with the Sn-Na alloy (in benzene, at 45-50°C) according to the reaction

4CHCl=CHHgCl + NaSn- (ClCH=CH)3SnCl -[- CH=CH + 4NaCl + 4Hg

The cis -organomercury gives t r i - c i s - ( /8-chlorovinyl)tin chloride, and the /!rans-isomer only t r i - trans-( j8-chlorovinyl)tin chloride [412]. The cis —isomer requires longer heating than the trans. The inter-action between di - <mws-((8-chlorovinyl)mercury and metallic tin results in t r i - tfnms-(/3-chlorovinyl)tin chloride,as well as d i - trans-(|S-chlorovinyl)tin dichloride and /3-chlorovinyltin tr ichloride [412]. As usual, longer reaction times favor the formation of t r i - trans -(/3-chlorovinyl)tin chloride.

The organometall ic tin compound forming in the interaction between cis -di-(/3-chlorovinyl)mercury and metall ic tin has not been isolated, but its cis-configuration has been demonstrated [412]. The reactions of cis- and trans- a-chloromercuristi lbenes with an Sn-Na alloy result only in symmetrization of the mercury compounds; no organotins are formed [228] (see also Chapters 6 and 13).

Triethylstannane reacts easily with esters of mercur i -b is-acet ic acid [413]:

The reaction takes place when the reactants are heated to 70° C under nitrogen and is followed by the amount of mercury separating out.

Triethylstannane reacts with diethylmercury (in the absence of solvent, over 5 hours at 100°C) in all reactant ratios [175]:

See, however, under "Synthesis of organotin compounds" ear l ier in this chapter.

Preparation of propyl triethylstannylacetate [413]. The propyl ester of mercuri-bis-acetic acid (24.3 g) and triethylstannane (12.5 g) are heated for 90 minutes at 75°C

1 r nitrogen. The solution is then decanted from the precipitate of metallic mercury (11.5 g, 96%). Distillation results in 3.1 g of propyl acetate (51%), b.p. 99-101°C/743 mm, and 13.2 g (73%) of propyl triethylstannylacetate, b.p. 102- 105°C/3.5 mm; n 201.4779; d ™ 1.2226. °


O

OR

(R=CH 3 , n-C3H7)

(C2H5)2Hg + 2(C2H5)3SnH - (C2H5)sSn2 + Hg + 2C2H,


The methyl ester was analogously obtained in 68%yield. Nesmeyanov and Kocheshkov [423, 424] found that the interaction

of d iary lmercur ies with SnCl2 and SnBr2 occurs according to the reaction

R2Hg + SnX2 - R2SnX2 + Hg (7)

and can be used for the synthesis of diaryltin dihalides. The reaction is conducted with anhydrous SnX2 in dry acetone, at the boil ing-temperature of the latter, and is complete in 30-60 minutes. Acetone is disti l led out of the liquid decanted f rom the metall ic mercury, the residue extracted with petroleum ether and the required product crystal l ized out of the extract. Thismethodhasbeen used [423-425] f o r diphenyl-, d i - p - t o l y l - , di-a-naphthyl- , di-/3-naphthyl-, d i - p -chlorophenyl-, di - p -bromophenyl - , d i - p-iodophenyl- and d i - p -carbethoxyphenyltin dichlorides and dibromides. In alcohol, only diphenylmercury and diary lmercuries containing radicals more electroposit ive than phenyl (in Kharasch's ser i es ) react normally according to reaction (7). The others replace the mercury by hydrogen:

R2Hg + SnX2 + 2C2H5OH 2RH -(- Hg + (C2H5O)2SnX2 (8)

Compounds containing stil l more electronegative radicals, for example p-aminophenyl, eliminate them in the f o rm of RH in ace-tone, which l imits the usefulness of the method [423]. Ary lmercury chlorides can also react in two main directions:

2RHgCl 2SnCl2 — R2SnCl2 + 2Hg + SnCl4 (9)

RHgCl + SnCl2 + C2H5OH RH + Hg + C2H5OSnCl3 (10)

The predominance of one or other direction depends in this case on the conditions mentioned in the preceding paragraphs. Whereas dibenzyimercury converts re lat ively smoothly into dibenzyltin dichloride, purely aliphatic organomercury compounds are not very suitable for transformation into organotins by this method because the reaction is extremely slow, is incomplete, and is accompanied by side formation of RHgCl , which in turn are almost wholly inert to SnCl2.

However, both trans, trans- and cis, c is - isomers of d i - ( ^ - ch lo ro -vinyl )mercury react smoothly and rapidly in the cold [426] with alcoholic SnCl2, forming two stereo isomers of di-/3-chlorovinyltin dichloride: a solid one (m.p. 77.5-78.5°C) and a liquid one (b.p. 101-102°C/3 mm; ^O 1.7494; n20 1.5675).


Reaction between trans,trans- di-(/3-chlorovinyl)mercuiy and stannous chloride. Prep-aration of trans,<rans-di-/3-chlorovinyltin dichloride [426].

/Cl H1

SnCU ( > = < ) , \ H /2

Trans,Jrons-di-(/3-chlorovinyl)mercury (2 g, 0.0063 mole) in 5 ml of absolute alcohol slightly acidified with dry hydrogen chloride and 1.2 g (0.0063 mole) of anhydrous SnCl2

in 5 ml of absolute alcohol are poured together. The reaction begins immediately in the cold. Heating for 10 minutes at 45-50°C and setting the mixture aside for an hour at room temperature results in an almost quantitative separation of metallic mercury (0.5 g, 97%). At the end of the reaction, the clear solution is decanted from the mercury and the alcohol driven off as completely as possible at 50-60°C on a water pump. Petroleum ether (10 ml) is then added; with this the remaining alcohol is distilled off. The residue in the flask is recrystall ized twice from petroleum ether. Yield; 1.05 g (58%). The trans,<rans-di-/3-chlorovinyltin dichloride is in the form of white crystals (m.p. 77.5-78.5°C) yellowing in the capillary at 135°C.

Cis- and trans -dipropenyltin dibromides are s imi lar ly prepared with retention of the configuration f r om cis- and trans -propenyl-mercury bromides and stannous bromide [427].

Of the s tereo isomer ic mercury derivatives of stilbene, only cis -a -mercur i -b is -s t i lbene forms with SnCl2 in acetone d i - a -stilbenyltin dichloride, together with a-stilbenyltin tr ichlor ide and cis-stilbene. 7Y» is -a-mercur i -b is -s t i lbene does not react with SnCl2 in alcohol or without a solvent in the molten state at 240-260°C [313]. Trans-a-chloromercuristilbene in alcohol sym-metr izes under the action of SnCl2, giving trans- a -mercur i -b i s -stilbene [313]. It is interesting that aromatic organomercury bro -mides react with SnBr2 di f ferently than the chlorides with SnCl2, i .e . [423]:

2RHgBr + SnBr2 — R2SnBr2 + 2HgBr ( H )

A side process is here the reaction

RHgBr + SnBr2 - RSnBr3 + Hg (12)

Synthesis of dibenzyltin dichloride [423]. Freshly prepared dibenzyimercury (5.7 g, 0.015 mole) and 4.5 g (0.0225 mole) of SnCl2 are heated to boiling in 25 ml of absolute alcohol. The reaction is very fast and most of the mercury separates out during the f irst few minutes. To complete the process, the mixture is heated to boiling for 30 min-utes. Metallic mercury separates out in a yield of 2.92 g. Evaporation of the alcohol and working up of the residue with a large volume of petroleum ether gives (after removal of the latter solvent) 5.56 g of the desired product; m.p. 160°C. The yield is almost theoretical.

The applicability of the reaction of organomercuries with com-pounds of divalent tin has been extended by carrying out the reaction in inert solvents. Thus, whereas in alcohol or acetone the reactions of cis-and £nms-propenylmercury derivatives with stannous halides do not g ive r i se to propenyltins, the latter can be obtained in 70-75%



yields in petroleum ether or l igroine [154]. Di-isopropenyltin d i -bromide and tetraisopropenyltin have been made f rom di - isopro-penylmercury and SnBr2 in petroleum ether, at room temperature and on heating to 65°C, respectively [428]. The geometric isomers of dipropenylmercury react with SnBr2 to g ive only dipropenyltin dibromide [154]. This variant of the method also allows the prep-aration of aliphatic organotin compounds [428]. Diethyltin dichloride and ethylmercury chloride have been found among the products of the interaction between diethylmercury and SnCl2 [428]. The r e -actions of diphenylmercury with SnCl2 in petroleum ether at various temperatures yield invariably only triphenyltin chloride [428] which is evidently formed via (C6H5)2SnCl2 according to the scheme:

The reaction with SnBr2 is analogous, but the yield of triphenyltin bromide is not so high [428]. Di - p-to ly l - , d i - o - t o l y l - a n d d i - a -naphthylmercury form with SnCh only the corresponding diaryltin dichlorides [428]. Attempts at synthesizing aromatic tin derivatives containing substituents such as OH and N(CH3 )2 in the ring were unsuccessful. A little phenol is found among the products of the reaction of di-o-hydroxyphenylmercury and SnCl2; the reaction did not proceed with p-dimethylaminophenylmercury chloride or with dibenzylmercury [428].

Apart f rom the stannous halides, organotins of the type R3Sn-SnR3

and R2Sn can be used [314] for the preparation of organotin der iva-tives by the reduction of organomercury compounds; the reactions with diarylmercuries can be written

An aliphatic organomercury compound (the methyl ester of mercuri -bis-acet ic acid) has also been reacted according to equation (13) [413].

Preparation of hexaethyldistannane [314]. Triethyltin chloride (40 g), obtained accord-ing to [430], is heated for 5 hours at 130°C with 5 g of powdered metallic sodium in 50 ml of isopentanol. The product is isolated by fractionation under nitrogen; b.p. 160°C/23 mm; yield: 70%.

Preparation of the methyl ester of triethylstannylacetic acid [413].

2 (C6H5)2SnCl2 + Hg ( C 6 H 5 ) 2 - 2 (C6H5)3SnCl + HgCl2

R 3 S n - S n R 3 + R 2 H g — 2R'SnR3 + Hg

R2Sn + R 2 H g - R2SnR2 + H g ( 1 4 )

( 1 3 )

O (C2H5 )3SnCH2C/

\ OCH3

Hexaethyldistannane (10.5 g) and 8.7 g of the methyl ester of mercuri-bis-acetic acid are heated for an hour to 160°C under nitrogen and the liquid then decanted from the


metallic mercury (3.4 g, 68%). Distillation gives 5.6 g (41%) of the desired product; b.p. 69-71°C/1.8 mm; nD10 1.4835; ^4201.2 9 56.

Preparation of diethy Idi phenyl tin [314]. Diethyltin (8.5 g, 0.05 mole) is heated for 30 minutes with 17 g (0.05 mole) of diphenylmercury to ISO0C on an oil bath. After cool-ing, the reaction mixture is worked up with petroleum ether and decanted from the metal-lic mercury. Evaporation of the solvent and fractionation of the residue at 4 mm gives a large fraction boiling at 154-156°C, which proves to be the required product. The yield is 9 g (60%).

S y n t h e s i s of the O rganometa l l i c C o m p o u n d s of E l ement s of G r o u p V of the Periodic Tab le

Trimethylant imony was obtained by heating the metal with d i -methy lmercury and t races of HgCl2 , in a sealed tube, f o r 160 hours at 150°C [414].

Experiments on the interaction of d iethylmercury with bismuth powder at 120-140°C, car r i ed out as ear ly as 1864 [369] by Frank-land and Duppa, led to the format ion of tr iethylbismuth.

The react ion of diphenylmercury with metal l ic bismuth does not proceed to complet ion: heating of diphenylmercury and an excess of Bi to 250° C in a current of hydrogen resulted in a mixture con-taining 41% of triphenylbismuth, 57% of diphenylmercury and 2% of b iphenyl [342] .

The interaction between phenylmercury chloride and a bismuth-sodium alloy containing 10% Na in boi l ing xylene gave r i s e to d i -phenylmercury and a negl ig ible y ie ld of triphenylbismuth [308].

Synthes is of the O r g a n o m e t a l l i c C o m p o u n d s of

Elements of G r o u p Vl of the Per iod ic Table

The reaction R2Hg+2 E - R 2 E+HgE, where E = S, Se or T e , occurr ing when d ia ry l - or d ia lky lmercur ies a re heated to 190-235°C with S, Se, or T e , has been used to p repare , f o r example, diperf luoroethyl [415], diphenyl [416, 417], d i - o - t o l y l (heating to 225-230°C) [310] and d i -p - t o l y l [310] sul f ides.

Dibenzy lmercury heated with sulfur to 100°C g ives only bibenzyl [418].

The reaction of secondary per f luoroa lky lmercury compounds with boil ing sulfur prov ides a method of synthesizing per f luoroth ioke-tones, f o r example [419]:

s (CF3 )2CF-HgCF(CF3 )2 - C F 3 - C (S) - C F 3

Tr i f luoroth ioacety l f luor ide has been s imi lar l y prepared in an 80% yie ld f r o m b i s - ( l - c h l o r o - l ,2 ,2,2-tetraf luoroethyl )mercury and sulfur [420].



Diphenyl [237], d i - o - t o l y l (220°C) [310], d i - p - t o l y l (225°C) [310] and di-a-naphthyl (190°C) [311] selenides and diphenyl (230°C) [237], d i - o - t o l y l (225-235°C) [310], d i - p - t o l y l (225-230°C) [310] and di-a-naphthyl [421] te l lur ides have been prepared analogously to the sul f ides.

Preparation of di-o-tolyl sulfide [310]. Di-o-tolylmercury (5 g) and 0.8 g of finely ground sulfur are heated for 12 hours at 225-230°C (the last 4 hours at 235°C) in a sealed tube f i l led with carbon dioxide. Di-o-tolyl sulfide is extracted from the reaction mixture with ether, distilled several times under vacuum until it crystallizes and finally recrystall izes from alcohol; m.p. 64°C; b.p. 175cC/16 mm.

Preparation of diphenyl selenide [237]. Diphenylmercury (4 g) and 1.79 g of selenium are heated for 4 hours at 220cC in a sealed tube fi l led with carbon dioxide. A slightly colored oil is formed. Yield: 2.2 g (85%). The product becomes colorless after distil-lation at 160-162°C/12 mm.

Preparation of di-a-naphthyl telluride [42l ] . Di-a-naphthylmercury (4.5 g ) and 2.5 g of tellurium powder are heated for about 8 hours at 190- 198°C/16.5 mm in a small Anschutz flask connected to a water pump. After cooling, the solidifying mass is steam-distilled to f ree it from naphthalene collecting in the upper regions of the flask. The residue is extracted with ether and the extract rapidly filtered and evaporated. The residue is recrystallized from alcohol. Slimy brownish-yellow leaflets are formed; m.p. 126.5°C. The yield of the crude product is 53%.

An unsuccessful attempt to obtain organouranium compounds by heating diethylmercury with uranium to 150-160° C has been d e -scr ibed ea r l i e r in this chapter.

S y n t h e s i s of the O r g a n o m e t a l l i c C o m p o u n d s of E lement s

of G r o u p Vl l l of the Pe r i od i c T a b l e

The product of the mercurat ion of cyclopentadiene, consisting of a mixture of cyclopentadienylmercury chlor ide and d i cyc lo -pentadienylmercury, reacts easi ly with iron powder in te trahydro-furan to g ive f e r r ocene [422]. In contrast to the usual methods of prepar ing cyclopentadienyl compounds of meta ls , in this case there is no need to use anhydrous solvents.

Preparation of ferrocene [422]. Tetrahydrofuran (150 ml) is added to a mixture of 150 g of the product of the mercuration of cyclopentadiene and 30 g of iron powder with vigorous stirring. The reaction begins rapidly and is controlled by cooling with cold water (not a cooling mixture). When the spontaneous reaction slows down, the mixture is boiled for 20 minutes on a water bath, poured into 500 ml of water containing 5 g of sodium dithionite and extracted with petroleum ether (b.p. 65-75°C). Evaporation of the solvents gives 12-15 g of crude ferrocene, which is subsequently recrystallized from ethanol; yield: 24-30%, calculated on the cyclopentadiene.


k) Reactions with Nitrogen Oxides

The reaction of nitrosyl bromide with diarylmercury

Ar2Hg + 2NOBr - 2 ArNO + HgBr2

has already been used by Bayer [430a] to prepare nitroso compounds for the f i rs t t ime.

The reaction of symmetrical polyfluoroalkyl organomercuries with nitrosyl chloride leads to polyfluoroalkyl nitroso compounds [140a], In certain cases it is accompanied by replacement of the mercury with chlorine, and, if the polyfluoroalkyl group contains hydrogen, by replacement of this hydrogen with chlorine [140a]. The reaction medium is dimethylformamide.

Organomercury compounds do not react with NO [431]. The action of nitrogen dioxide on diarylmercuries [431-433] or

arylmercury salts [433] gives r i se to nitroso compounds:

Ar2Hg + N2O4 -> ArNO + ArHgNO3 , ArHgX + N2O4 - ArNO + HgXNO 3

and the action of N2O4 on organomercuries in organic solvents to nitro compounds [434].

The interaction of a diarylmercury with nitrogen trioxide gives a 50% yield of the corresponding aryldiazonium salt [431, 432]:

Ar2Hg + N2O3 -> ArHgNO3 + ArN2NO3

Pure nitrogen trioxide does not split mercury out of organo-mercury salts. On the other hand, the simultaneous action of N2O3 and NO leads to an 85% yield of phenyldiazonium nitrate [435] calculated on the basis of the reaction:

(C6H5)2Hg + 4N203 - 2C6H5N2N03 + Hg (NO3)2

Reacting nitrogen trioxide with dimethylmercury, Bamberger obtain-ed, not the expected diazomethane, but imidodihydroxamic acid [437]:

HON = C — N H - C = NOH I I

HO OH

Preparation of phenyldiazonium nitrate from diphenylmercury [435]. A current of nitric oxide is passed into a solution of 1.1 g of diphenylmercury in 25 ml of CHCl3, cooled to 15°C, and about IOml of a 10% solution of N2O3 in the same solvent rapidly stirred in. The stirring and the passage of NO are continued for 30 minutes, after which the solution is shaken in four portions with 100 ml of water. The combined aqueous extracts contain the entire diazonium salt. The yield of phenyldiazonium, determined by coupling with /3-naphthol and weighing the resulting benzeneazo-/3-naphthol, is 85%.

Whereas HNO3 f r e e f rom nitrogen oxides mere ly replaces the mercury in organomercury compounds by hydrogen [438], s imi lar ly to other acids, the action of nitric acid containing nitrogen oxides



on aromatic organomercuries leads to a replacement of the Hg by the nitroso group and to the formation of nitroso compounds and products of their further transformations (depending on the con-centration of the HNO3): diazo compounds (mainly in dilute acid), nitro compounds [434, 436, 438-441], polynitro compounds [434, 436, 438, 440], nitrophenols [436, 438] and so on.

The interaction between m-diacetoxymercuribenzene and dilute (about 40%) HNO3Over 1% hours at 45°C gives only 2,4-dinitrophenol [436]; a " and /3-naphthylmercury nitrates reacted with concentrated nitric acid in the presence of nitrogen oxides give r i se to 2,4-dinitro-a-naphthol. The f o rmer compound fo rms also a small amount of a -nitronaphthalene [442],

The action of nitric acid and nitrogen oxides (N2O3) on benzyl-mercury chlor ide leads, depending on the conditions, to phenyl-nitroso- and phenylnitromethane or to diphenylfuroxane [443], The action of N2O4 on benzylmercury chloride or on dibenzyi-mercury gives benzyl nitrite and benzyl nitrate [443]. D i - n -butylmercury and N2O4 react in chloroform at -5° C to f o rm butylnitrite [443]. According to [444], diazonium salts are formed by Bamberger 's reaction through the intermediate formation of organomercury compounds, fol lowing the action of nitrosylsulfuric acid on aromatic sulfonic and carboxyl ic acids and on nitro com-pounds, in the presence of mercur ic salts.

Organomercuries containing a CO group in the position a to the mercury atom react under mild conditions with aryldiazonium fluoroborates in media having a high die lectr ic constant, with replacement of the Hg atom by the ary lazo group [449],

1) Reactions with Ketones

Formation of ketones during the interactions of ketene with R2Hg and RHgX has been reported [445-447].

The reaction of quasicomplex mercury compounds (mercurated hydroxy- and oxo-compounds) leads to high yields (depending on the medium in which the reaction is carr ied out) of mercurated acetic acid or its esters (see Chapter 6).

m) Reactions of Organomercury Compounds with the Grignard Reagents and with the Organometallic

Derivatives of Lithium, Sodium, Zinc Aluminum and Other Metals

The subject of this section is also dealt with in Chapters 2 and 12. When R,Hg (R = C6H5, p-CeH4CH3, p-BrC6H4 , p-ClC6H4 [448],

CgH5CH2, 3-iodo-4-methoxyphenyl) react with R ' L i in ether or a


mixture of benzene and petroleum ether, the radicals in these organometall ics are exchanged, leading to the formation of R'2Hg and RLi [450, 451],

In the reaction of Grignard reagents with RHgX containing a sufficiently labile mercury atom, for example one in a position a to the carbonyl group, the mercury is replaced by MgX, anal-ogously to the Tserevit inov-Chugaev reaction in which a labile hydrogen is replaced by MgX:

RHgX + CH3MgX - RMgX + CH3HgX

RH + CH3MgX - RMgX + CH4

This behavior is observed, for example, with halogenomercuri-acetophenone [452]:

CsH5CCH2HgX + RMgX - RHgX + C6H5CCH2MgX Il Il O O

(the product is tautomeric with C6H5C=CH2), which contrary to

OMgX ear l ier reports [453, 454] does not exhibit the reaction of the carbonyl group. An analogous reaction occurs between o-halo-genomercuriphenol and Grignard reagents [455]:

OH OMgBr

+ 2C 2H 5MgBr-J 1 +C2H6 + C2H5HgCl V N .. .

HgCl MgBr

Less labile mercury atoms do not react in this way, for example:

- C - + C2H5MgBr / \

HgBr " 5 ^ 2 C " H g B r O ^ , , d . H5C2 OH

The action of phenylmagnesium bromide on allylphenylmercury [138] follows the above pattern:

CH2=CHCH2HgC6H5 + C6H5MgBr - C6H5MgCH2CH=CH2 + C6H5HgBr

The reaction of di- (bromoethynyl)mercury with phenylmagnesium bromide in ether gives r ise to. diphenylmercury and - /3-bromo-ethynylmagnesium bromide. This constitutes one of the proofs that di- (bromoethynyl)mercury does not exhibit quasicomplex properties [456] (compare the action of C6H5MgBr on trans -/3-chlorovinyl-mercury chloride, yielding diphenylmercury and acetylene). In s imi lar reactions involving transfer of an optically-active radical



(in dibutyl ether at 80°C) :

R2*Hg + R'MgBr ^ R*R'Hg + R*MgBr

[where R* = (+JC2H5C+H(CH3)CH2CH(CH3) and R ' = (CH3)2CHCH2CH2

C+H(CH3 ) ] , and in the reaction of optically active di-isoheptylmer-cury with racemic isoheptyl-lithium, the configuration of the radical is partially preserved [429].

In accordance with the hypothesis put forward by Knunyants et al. [457] that radical exchange between organometallic compounds should be facilitated by large differences between the electro-negativities of the exchanging radicals, considerable degrees of radical exchange have been demonstrated [144] in the following reactions:

Ether (CF3)2Hg + C2H5MgBr (C2H5)2Hg (60%)

T H F (CF3)2Hg + CF2=CFMgBr ' (CF 2 =CF) 2 Hg

T H F (CF2=CF)2Hg -J- CH2=CHMgBr ' (CH2=CH)2Hg (43%)

T H F (CF2=CF)2Hg + CsH5MgBr (C6H5)2Hg 4- CF2=CFMgBr

In the same way, in his attempts to prepare asymmetrical fully substituted organomercury compounds, Frankland [459] isolated only diethylmercury from diethylzinc and methylmercury iodide, and only diethyl- and dimethylmercury from dimethylzinc and ethylmercury chloride. Similarly, Hilpert and Griittner [460] obtained only dibenzyimercury f rom benzylmagnesium bromide and ethylmercury bromide, and only diethylmercury f rom ethyl-magnesium bromide and phenylmercury bromide.

The reaction

R2Hg + R^Mg R'2Hg + R2Mg

(in tetrahydrofuran at 25°C) proceeds the faster the greater is the dif ference between the stabilities of R and R' . However, various dialkylmagnesium compounds react at the same rate with dietnyl-mercury. On the basis of their tendency to form bonds with mag-nesium (in order of decreasing stability), the radicals R fall into the following sequence: C6H5C = C > C6H5 > CH3 > C2H5 > CH(CH3)2.

(t-C4H9)2Mg does not enter into an exchange with (iso-C3H7)2Hg or (C6H5)2Hg after 5 hours at approximately 20°C [458a].

The exchange

(C6F5)2Hg + 2CH3Li 2C6F5Li+ (CH3)2Hg

has been studied [99a], The radical exchange between diferrocenylmercury and n-butyl-

lithium (25°C, ether-benzene solution), leading tp the formation of


monolithioferrocene and di-n-butylmercury,proceeds to completion within 10 minutes. The degree of exchange (73%) is not increased by more than a fourfold excess of the butyl-lithium [322], Monolithio-ferrocene is also obtained f rom ferrocenylmercury chloride and n-butyl-lithium [461].

Isotope exchange has been used [462, 463] to show that fully substituted compounds of mercury exchange their radicals with the organometall ic derivatives of Na, Mg, Zn, Al , Si and Sn. Thus, diethylmercury [462] reacts with the following ethyl compounds of metals containing 14C in the ethyl group (the reaction conditions and the degree of exchange are shown in parentheses): C2H5Na (2V2

months at room temperature, 9.5%; 5 hours at IOO0C, 19.9%) and (C2H5)3Al (5 hours at IOO0C, 59.5%). Diethylmercury containing 14C also reacts with diethylzinc (27% exchange after 20 hours at 65°C). (CD3)2Hg exchanges radicals with (CH3)2Mg (8 days, in tetrahydro-furan, at 28°C) and with ethylmagnesium bromide [361a]. Onthe other hand, NMR studies [368a] proved that no radical exchange takes place between (CD3)2Hg and (CH3)2Cd or (CH3)2Zn [361a], or between (CH3)2Hg and (CH3)2Cd or (CH3)2Zn.

No exchange occurs between tetraethyl-lead and (C2H5)2Hg after 20 hours at IOO0C [462]. Radical exchange occurs to the extent of 91% between diphenylmercury and triphenylaluminum labeled with 14C [463]; no active diphenylmercury could be isolated f r om the mixture containing diphenylmercury and phenylsodium labeled with 14 C. In accordance with the inert character of the C-Si bond and the relat ive lability of the C - P b bond, the exchange between (C6H5)2Hg containing 14 C and tetraphenylsilane occurs to the extent of only 0.06% after 20 hours at IOO0C; under the same conditions,tetraphenyl-lead undergoes 88% exchange [463].

Reutov et al. found that both the fully substituted and also some mixed organomercury compounds undergo exchange reactions with radiomercury (203Hg):

n) Isotope Exchange of Organomercury Compounds with Radiomercury and

Compounds Containing Radiomercury

RHgX + Hg* RHg*X + Hg

RHgR + Hg* zi RHg*R + Hg ( 1 )

(2)

and with ^wHg halides 203

R2Hg + Hg*X2 S R2Hg* + HgX2

RHgX + Hg*X2 j i RHg*X + HgX2

(3)



The following types of exchange have also been reported:

R2Hg + R2Hg* R2Hg* + R2Hg (5)

R2Hg + R'Hg*X t R2Hg*+RHgX (6)

R'HgX 4- RHg*X RHg*X+ R'HgX (7)

Of the mixed organomercuries RHgX belonging to the aliphatic and acyclic ser i es , only the a-mercurated oxo-compounds react with 203Hg under mild conditions (in the cold, in benzene or acetone) [464, 465]. The reactivity of RHgX toward metall ic mercury fal ls off in the fol lowing ser ies : a-bromomercuricyclohexanone > ethyl ester of a-bromomercuriphenylacetic acid > Z-menthyl ester of a -bromomercuriphenylacetic acid > phenylmercury bromide > 3-bromomercuri-3-benzylcamphor > 3-bromomercuricamphor. The exchange between 203Hg and the Z-menthyl ester of a -bromomer-curiphenylacetic acid, which occurs to the extent of 100% within 15 hours, proceeds without a change in the stereochemical con-figuration [465]. Cis- and trans -/8-chlorovinylmercury chlorides also preserve their configuration during exchange with 203Hg in cold acetone [466],

Di - t rans- and di-c is -chlorovinylmercury react readily with finely dispersed metallic mercury in cold acetone, the isotopic equilibrium becoming established within a few hours [466]. The stereochemical configuration of the chlorovinyl group is retained, in accordance with the rule established by Nesmeyanovand Borisov (see references under "Reactions of the products of the addition of mercuric salts to triple bonds", Chapter 6).

The aromatic R2Hg enter into isotope exchange with metall ic mercury under mild conditions:

+ Hg* ^ X - Q > - H g * - < Q - X + Hg

at a rate which depends on the nature of X , increasing in the order :

NO2lCl < H < CH3 < OCH3

This order was established by carrying out the reactions in pyridine at 60°C [467].

Di -p-anisy lmercury reacts with Hg* in benzene already in the cold, reaching equilibrium after 16 hours [467]. For diphenylmer-cury the isotopic equilibrium requires 2.75 hours in dioxan at 60°C and only 30 minutes in xylene at 140°C [467].

Ary lmercury salts react faster with metall ic mercury than the diaryl compounds [468], Electropositive substituents accelerate the isotope exchange, whereas electronegative ones retard it.


Winstein et al . [469] have reported that in the reaction

RHgR' + 203HgCl2 - * RHgCl + R'HgCl

the labeled mercury becomes stat ist ical ly distributed between the two radicals splitting away f r o m RHgR ' . However , this work, carr i ed out to establish exchanges of the type of reaction (5), naturally did not take this complication into account, and should be repeated more accurately.

The isotope exchange between cis -2-methoxycyclohexylneophyl-mercury and 203HgCl2 also proceeds with retention of the conf igura-tion of the radical [469] (see also Chapter 13). The re la t i ve polar i t ies of the C -Hg bonds in RHgR' have been determined [470] f r o m the distribution of 203Hg. between RHgBr and R 'HgBr in the reaction of 2 0 3HgBr2 with RHgR' (in ether at -20°C in the case of the aliphatic compounds and tetrahydrofuran in the case of d ia ry lmercur i es ) (the HgBr2 attacks the more polar C -Hg l inkage). Among the aliphatic rad ica ls , the strength of this bond increases with in-creasing chain length of R(C3H? > C2H5 > CH3 ). In the compounds ArHgAlk , the bond between the mercury and ,the a r y l , capable of taking part in conjugation, is stronger than Hg-Ailk [470] (see however [472]). In the C6H5HgAr (Ar = P-BrC6H4 and P-CH3OC6H4 ) it is the phenylmercury bond that is broken [470].

Dessy 's report [471] that in the reaction between phenylethyl-mercury and 203HgCl2 the 203 Hg is equally distributed between the two radicals is" based on an experimental e r r o r [472]; in fact , c leavage of the phenyl-mercury bond takes place.

Organomercury salts consisting of a-mercurated oxo-compounds, and also cis- and trans-/3-chlorovinylmercury chlor ides, react with 203Hg halides [reaction (4)] under mild conditions: the f o r m e r in benzene, dioxan, or ethanol at room temperature or at 50°C [473], the latter in acetone in the cold. T h e r e a c t i v i t y o f t h e a-mercurated oxo-compounds decreases in the fo l lowing s e r i e s : a -bromomercuricyc lohexanone > 3 -bromomercur i -3 -benzy l cam-phor > ethyl ester of a-bromomercur iphenylacet ic acid > l -menthyi es ter of a-bromomercuriphenylacet ic acid > 3 -bromo-mercur icamphor . The interactions of cis- and trans-^-chloro-v iny lmercury chlorides [466] and of c i s - and trans-2-methoxycy-c lohexylmercury chlorides [465] with HgCl2 occur with retention of the s tereochemica l configuration. In the latter cases the best reaction medium is dioxan, and the optimum temperature 120-130°C [465]. Reaction (4) is of second order . Measurements have been carr ied out f o r R = CH3 (in alcohol, at 100°C f o r X = Cl [474, 475], I [476]; at 60°C f o r X = Br , CH3CO2 [476]; in a mixture of alcohol, HNO3 and traces of water at O0C fo r X = NO3 [476]); C2H5

(in alcohol, IOO0C [475]); CsH7 (as f o r ethyl [475, 477]); S-C4H9

( X = B r , in alcohol at 60°C [476]); (CH3 )3CCH2 (as fo r s-butyl , 130°C [476]); C6H5CH2 (in quinoline [478]); C6H5CHCOOC2H5 [479,



480]; P-XC6H4CH2 (in quinoline at 70°C [481]); C6H5 (in glacial acetic acid, 50% alcohol, water , benzene [482], aqueous benzene [483]; in pyridine kinetic measurements are di f f icult owing to the rapidity of the exchange [475, 489]); and p-HOOCC6H5 [485].

In the case of R = S - C 4 H 9 reaction (4) proceeds with retention of the configuration of the alkyl group. Retention of the configura-tion and the character of the kinetic relationships of reaction (4), part icularly the increase of the rate of exchange in the order X = B r < I « CH3CO2 « NO3 [476], the character of the salt e f fect [476], and the negl igible e f fec t of s ter ic factors appearing for R in the order CH 3 < pr imary alkyl < secondary alkyl [486], all indicate that this reaction takes place by an SE 2 mechanism. However , the mechanism and the order of the reaction between 203HgBr2 and a-bromomercuriphenylacet ic acid depend on the reaction medium [466]: in pyridine [487] ,dimethyl formamide [487a], aqueous alcohol [487a, 488], and benzene [487a] the reaction is of o v e r - a l l second order (SE2 mechanism), whereas in dimethyl sulf-oxide [488a] and dioxan [487b] the process is of f i rs t o rder (the mechanism is S#1 in the latter case, contrary to ear l i e r data [480]).

The rates of the reactions of 203HgBr2 with p-substituted benzy l -mercury bromides depend on the nature of the substituent, de -creasing in the order (CH3)2CH > CH3 > H > Cl > F [481], The reactions proceed much faster in dimethyl sulfoxide than in quinol-ine, and are catalyzed by additions of KBr [481], In the latter case the p-substituents exert a di f ferent e f f ec t on the reaction rate [481], For all these benzyl compounds the reaction proceeds by an SE 2 mechanism, even in (CH3)2SO; an mechanism could be rea l i zed only in the case of p-nitrobenzylmercury bromide containing a strongly electron-attract ing substituent [488b],.

Another factor which af fects the rate of the isotope exchange, f o r example that between ethyl a-bromomercuriphenylacetate and 203HgBr2 , is the polarity of the solvent: the exchange reaches 52% af ter 9 hours at 75° C in benzene and 89% af ter 1% hours at the same temperature in 70% aqueous dioxan [480, 489].

The exchanges between RHgX and radiomercury halides are accelerated by acids [482] and bases (diethylamine, pyridine) [473, 480].

Two types of catalysis of reaction (4) by metal halides ( L iX ) have been established. The two types can be distinguished as one-anion and two-anion ones, depending on the number of ions X supplied by the L i X and participating in the transition state [490]. The stereochemical configuration of optically active R groups (R = S -C 4H 9 ) is retained [490] in both cases. The mechanism is SS 1 [490].

In reaction (5), with R ' = CgH5 and R = p -ClC6 H4, in pyridine at 60° C, the t ime required to reach 50% exchange is equal to 3 hou^ . R ' = P -C lC g H 4 does not undergo isotope exchange with R2Hg ^II = CH2CHO) at 20°C in acetone solution. However , in the case of


R' = C6H5 or P-CH3OC6H4 , the interaction with R2Hg (R = CH2CHO) achieves isotopic equilibrium almost instantaneously in acetone at 20°C [491].

The isotope exchange in reaction (6) ( for R ' = CH3CH(CH2)2

CH(CH3 )2 and R the same optical ly-act ive radical X = Br in ethanol at 60°C [492] and f o r R = S -C 4H 9 , R ' = opt ical ly-act ive S -C 4H 9 , X = Br in ethanol at 35°C, X = CH3COO and NO3 at 0°C [493]) is accompanied by distribution of the optical activity between the two mercury compounds and occurs with retention of the s t e r eo -chemical configuration. Kinetic studies [493] ( for R = S-C4H9 ; bimolecular reaction) showed a dependence of the reaction rate on the polarity of the anion (the rate increases in the order X = Br < CH3COO < NO3 ) and the presence of a salt e f fect . Retention of the stereochemical configuration and the kinetic data show that the latter reaction is SE 2 [493], If R is isoheptyl, the reaction is of over -a l l second order ( f i rst order with respect to each compo-nent) [483a],

Rapid isotope exchange occurs in the C6H5HgBr- (C6H5 )2Hgsystem, both in pyridine at 100°C and in the molten state, in the absence of solvent [484].

Reaction (7) between two organomercury salts, phenylmercury bromide containing 203Hg and ethyl a-bromomercuriphenylacetate in pyridine, is of over -a l l second order ( f i rst order with respect to each component) [494].

The isotopic equilibrium between a l ly lmercury bromide and p-(CH3)2NC6H4 03HgBr is established ve ry rapidly [473a].

0) Pyrolysis of Organomercury Compounds

On being heated to elevated temperatures (generally above 300°C, though lower temperatures suff ice in some cases) , organomercury compounds decompose with separation of metal l ic mercury (and a mercury salt in the case of the decomposition of RHgX) . The fully substituted compounds are said [495, 496] to decompose in a single stage:

R2Hg - » 2R' + Hg

with transition of the mercury f r om the divalent sp -state to the zero-valent s2 -state, o r , less probably, in two stages:

R 2Hg-> RHg + R-

RHg' - R- + Hg

It is possible that the actual route of decomposition depends the temperature [497]. The resulting radicals R' behave normally for



radicals in the gaseous phase, dimeriz ing, disproportionating, or reacting with fragments of the organomercury compound or with other substances present in the reaction vesse l , particularly metal mir rors (498, 499]. For a discussion of the subsequent behavior of these radicals, which is outside the scope of this book, the reader is re ferred to the appropriate l i terature: pyrolysis of dimethyl-mercury [495, 496, 498-513, 515-520], diethylmercury [495,500, 520-523], di-n-propylmercury [495, 524, 525, 529], di- isopropyl-mercury [495, 497, 526-529], diperf luoroisopropylmercury [130] di-n-butylmercury [529-531], di-s-butylmercury [531] (at I lO 0 C [43]), di-t-butylmercury (at 40°C) [43], divinylmercury [524], cis-di-/3-chlorovinylmercury [126], dicyclohexylmercury (in benzene) [2a], dibenzylmercury [194, 532], diphenylmercury [248, 418, 495, 523, 533], 2,2-diphenylenemercury [580],n-propylmercurychloride [523], di-(3-hydroxy-3-phenylpropyl)mercury (120-130°C in vacu-um) [534], di-(3-hydroxy-3-methylbutyl)mercury ( IOO-I lO0C) [534], cis -/3-chlorovinylmercury chloride [127], phenylmercury chloride [523], bromide [523], iodide [535] and p-vinyl benzoate [553], It has been shown quantitatively that the stability of (XCeH4)2Hg at 130-150° C depends on the nature of the substituent X [536].

Pyrolyses of vinylmercury xanthate (115-125°C/25 mm) and thiocyanate (100-120°C/10 mm) gave the vinyl esters of the co r -responding acids (in the latter case a mixture of vinyl thiocyanate and vinyl isothiocyanate) [514].

Pyrolysis of d i - ( o-iodophenyl)mercury at 600°C gives o-d i -iodobenzene and biphenylene (25-64%), together with HgI2, Hg2l2 and traces of triphenylene [537].

bis-Pentafluorophenylmercury is unchanged after heating for 5 hours to 250°C in a sealed tube [44].

Dibenzylmercury has been decomposed in nitrobenzene [532a] and nitrosobenzene [532b],

Thermal decomposition of diphenylmercury in cyclohexane [539] (260-280°C, 150 hours, in sealed tubes) and C6D6 [539a] occurs to the extent of approximately 9% and gives somewhat different pro-ducts than photodecomposition; the products in cyclohexane are mercury, benzene, cyclohexene, phenylcyclohexane, traces of b i -phenyl and a polymer ( -C6H4Hg-)n , whereas in C6D6 unlabeled b i -phenyl predominates among the products. On the other hand, in toluene, thermal decomposition (280-300° C) and photodecomposition of diphenylmercury proceed in the same way, with the formation of tar , benzene (the hydrogen is split off by the phenyl radical not f rom the CH3 group but f rom the aromatic ring of the toluene), mercury, and a mixture of o-, m- and p-methylbiphenyls [539b]. The decom-position of di ferrocenylmercury at 265°C gives ferrocene (68%) and bi ferrocenyl (13%) [322], For the thermal decomposition of d i -ferrocenylmercury in the presence of metals, see ear l ier in this chapter.

Acceleration of the polymerization of vinyl acetate by products


of the decomposit ion of diphenyl- and d ibenzy imercury has been studied [540].

Thermal decomposition of cis-di-/3-chlorovinylmercury [126]. vinylmercury (0.1178 g) is heated, with quantitative collection of the liberated acetylene in ammoniacal cuprous chloride. Acerylene begins to be evolved at 100-105°C. The heating is continued for an hour. The acetylene is flushed out with hydrogen from the reaction vessel over a period of 40 minutes. Titration of the solution of the resulting cuprous acetylide accounts for 99.12% of acetylene, calculated on the weight of the starting sample.

C6H5HgOCOCH3 and C6H5HgNO3 heated with molten benzoin to 150-120°C decompose to g i ve , respec t i ve ly , acet ic acid and nitrous acid [458].

p) Photochemical Reactions of Organomercury Compounds

React ions in the G a s Phase

Under the action of u l t ra-v io le t (wide range of wavelengths) , the R2Hg decompose into radica ls :

R H g R - R H g ' + R and further

RHg " -> R ' + Hg

For the reactions of the organic radicals R" f o rming during the photolysis of organomercury compounds, a discussion of which is beyond the scope of this book, the reader is r e f e r r e d to the l i t e r a -ture : photolysis of d imethylmercury [542-571], d iethylmercury [572-575], d i -n-propy lmercury [576], d i -n-buty lmercury [577-578], d iper f luoroethy lmercury [579], diphenylmercury [580] and d iv iny l -mercury [580a].

Photolysis of methylmercury chlor ide at 2000C under the influence of photo-excited mercury has been descr ibed, for example in [581],

U l t ra-v io le t light causes interconvers ions between geometr i ca l i somers of ethylenic organomercury der ivat ives (see below) .

R e a c t i o n s in So lut ion

Razuvaev and his associates have shown that organomercur ies in solution initiated by u l t ra-v io le t i rradiat ion lose their customary inertness towards organic hal ides, compounds capable of dehydro-genation (alcohols, certain ethers , e tc . ) , and aromat ic hydrocarbons.

In the presence of u l t ra-v io le t l ight,both R2Hgand RHgX (X = OH) in solution decompose into radicals

R 2 H g RHg- + R - ( 1 )

Rejcrenccs see page 426


RHgOH -* RHg' + OH ( 2 )

as in the gaseous phase. The resulting radicals RHg' may react with the solvent, depending on the nature of R, decompose further:

In the present section we shall not be concerned with the behavior of mercury - f r e e radicals R' forming in the photolysis of R2Hg and RHgX.

In the photolyses of R2Hg (R = methyl [278, 582], ethyl [583], 2-carbomethoxyethyl [584], cyclohexyl [585], phenyl [277, 278, 585-597], o-tolyl [278, 598], p-tolyl [599], p-chlorophenyl [598], p-anisyl [600], carboxy- and carbomethoxyphenyl [601], a-naphthy 1 [277, 602], and i3-naphthyl [603]) in halogen-containing solvents (chloroform [277, 572, 582-585, 587, 598-603], bromoform [587, 601], CCl4 [277, 278, 582, 585, 590, 595, 598-603], methyl iodide [582-584, 593, 602], trichloroethylene [587], ethyl bromide [595, 602], ethyl iodide [602], dichloroethane [598, 603],tetrachloroethane [586, 602], hexachloroethane [586], isobutyl bromide [588], t-butyl chloride [587], Chlorex [588], isopentyl bromide [602], decyl bromide [589], benzyl chloride [278, 592], benzyl iodide [592], bromobenzene [588], iodobenzene [591, 592], o-nitroiodobenzene [594], o-iodoanisole [594], and o-iodoacetophenone [594]), the radical RHg' abstracts the halogen f rom the solvent and forms RHgX. In chloroform, partial separation of the mercury takes place by reaction (3).

The same behavior has been observed in these solvents for the radical RHg ' forming in the photolysis of RHgOH (R = phenyl [604, 605], mesityl [606], p-dimethylaminophenyl [606]).

The photoreactions of diphenylmercury with chlorobenzene and of d i -p-anisy lmercury with CCl4 [600] g ive r i s e toca lome l and tar. Anisole is also found among the products in the latter case.

In solvents not containing halogens (alcohols [277, 585-587, 601], acetone [277, 587], ethylcellosolve [277, 587, 599], dioxan [601, 607], diethyl ether [587], ethyl formate [277], 2,2,4-trimethyl-pentane [277, 587], isopropylbenzene [608, 609], morpholine [610], hexane [611] and others), the decompositions of R2Hg (R = methyl [611], ethyl [583], n-butyl [609], phenyl [277, 585-587, 589, 607, 608, 610, 612], o-tolyl [277, 598], p-tolyl [599], p-chlorophenyl [589], p-anisyl [600], carboxy- and carbomethoxyphenyl [601], a-naphthyl [277] and /3-naphthyl [603]) and RHgOH (R = phenyl [604, 605, 613] (in benzene) [614], o- and p-tolyl [606], p-nitro-phenyl [606, 615] and p-dimethylaminophenyl [613]) do not stop at stages (1) and (2) but continue to (3) with separation of mercury;

R H g ' R - + Hg (3)

or react between themselves:

2RHg'-» R2Hg + R' (4)


the resulting radicals R' dehydrogenate the solvent, sometimes dimerize and disproportionate.

Aromatic substitution occurs during the photolyses of R2Hg [4, 72a] RHgOH [613] and RHgX [616] in aromatic compounds:

R2Hg + ArH -> RAr + Hg

RHgOH + ArH RAr + Hg + H2O

In the case of diphenylmercury this has been proved by decom-position in labeled benzene [4]. No isomerization of the radical occurs during the decomposition of diphenylmercury labeled with 14C in positions 1,1 (in benzene) [532c].

The photolysis of methylmercury iodide in isopropylbenzene gives r ise to methane, 2,3-dimethyl-2,3-diphenylbutane, and m e r -curous iodide; in the photolysis of the same salt in benzene and chlorobenzene, the methyl radicals methylate the solvent to give, respectively, toluene and a mixture of o-, m- and p-chlorotoluenes [616].

Both radicals are split off during the photolyses of dimesityl-mercury [617], di-2-phenylethylmercury [618], dicyclohexylmer-cury [585], partly diethylmercury [583] and mercuri-di-/3-pro-pionic acid [584], giving in halogen-containing solvents RCl in CCl4

and RH in CHCI3 as well as Hg2Cl2, and forming RH in solvents not containing halogens. Photolysis of dibenzylmercury [75, 619] and benzylmercury hydroxide [620] and succinimide [621] in all solvents results in bibenzyl and mercury (HgCl2 is formed in CHCl3). The absence of an interaction between dibenzylmercury and the solvent on irradiation has been confirmed by irradiating the above compound in a deuterated solvent [622]. Biphenyl forming under the action of ultra-violet on diphenylmercury and uC 6H 6 contains 50% [4] and, during decomposition in C6D6, up to 88% of labeled benzene nuclei; in the latter case a little C6H5C6H5 and C6D5C6D5 is also formed [539a], as well as C6H6 and hydrogen-containing deuterobenzene; the photodecomposition of (C6D5)2Hg in C6H6 gives r ise to C6D^H, C6D4H2, C6DsH3 and biphenyl molecules of all these three types [539a].

C-14C exchange following the irradiation of phenylmercury bro-mide and C6H6 and of phenylmercury bromide and C6H5Br proceeds without any additives only in the fo rmer case; in bromobenzene considerable reaction occurs only in the presence of cobalt or aluminum salts or of metallic s i lver [623].

Diphenylmercury and dicyclohexylmercury photolysed in media containing 14C andDundergo radical exchange [585, 612] (see above).

The fact that the photoreactions of diphenylmercury and phenyl-mercury hydroxide take place by different mechanisms has been established by means of labeled atoms [624, 625].

The radicals forming in the photodecomposition of diphenyl-mercury in a mixture of two solvents only one of which contains a halogen react in such a way that C6H5Hg' abstracts a halogen



f r om the halogen-containing component to g ive phenylmercury chloride, whereas C6H5 abstracts hydrogen f r om the other com-ponent and fo rms benzene [626]. The reaction is initiated by pe r -oxides [627]. In a mixture of chlorine- and bromine-containing solvents, C6H5Hg' abstracts bromine in pre ference to chlorine [628], However, the position is reversed and chlorine is taken up preferent ial ly , if the bromine is joined to an aryl and the chlorine to an alkyl group [628].

The action of the halides of metals that do not f o rm stable organometallic compounds is s imi lar to that of ultra-violet . They too initiate the decomposition of R2Hg into RHg' and R' [629], RHg' splits off a halogen atom f rom the metal halide to give RHgCl; in the case of CoCl2 , FeCl3 [630], NiCl2 , MnCl2 [629], the R' radicals abstract hydrogen f rom the solvent, and in the case of CuCl2 they split off Cl f r om the metal salt and f o rm RCl. Metal halides taken in an amount calculated for the splitting off of both radicals com-pletely dearylate diphenylmercury, giving r ise to HgCl2 and benzene (in hydrogen-containing solvents) and chlorobenzene in the case when the metal halide is CuCl2 [629]. Full dearylation of diphenyl-mercury with the formation of benzene has also been reported under the action of FeCl3 , CoCl2 and CuCl2 in morpholine (CoCl2 gives a small amount of phenylmercury chloride) [630].

Under the action of FeCl3 and CoCl2 , dibenzyimercury decomposes in ethylcel losolve to metall ic mercury with the formation of the ethyl benzyl ether of ethylene glycol. The action of CuCl2 in ethyl-cel losolve and dioxan results in HgCl2 and the same ether, HgCl2

and benzyl chloride being formed in dioxan. Theproducts with FeCl3 , in dioxan, are benzylmercury chloride and benzyl chloride [631]. The reaction between cupric chloride and di ferrocenylmercury in dioxan leads to a mixture of chloroferrocene and ferrocene [281]:

CuCl2 (C5H5FeC5H4)2Hg * C5H5FeC5H4Cl + (C5H5)2Fe

Photo- and thermal decompositions of organomercury compounds in solution do not always proceed in an analogous manner, but may nevertheless be the same in certain cases. This happens in the reaction between diphenylmercury and methanol [292]:

(C6H5)2Hg + CH3OH ^ r 2C6H6 + Hg + CH2O

Both kinds of decomposition of diphenylmercury in toluene give the same products, in roughly the same proportions (seeabove) .

On the other hand, the photodecomposition of diphenylmercury in cyclohexane gives (after 100-150 hours) benzene (70-80%),bicyclo-hexyl, cyclohexene, phenylcyclohexane, and biphenyl [539], For the thermal decomposition of diphenylmercury see above.

The photodecomposition of diphenylmercury in cyclohexene r e -sults in benzene and bicyclohexenyl; the formation of benzene due


to abstraction of hydrogen f r om the solvent by the phenyl radical has been confirmed by using labeled (14C6H5)2Hg [539J. The d i f f e r -ence between the photolytic and thermal decompositions of diphenyl-mercury in labeled benzene has already been described.

The decomposition of diphenylmercury in carbon tetrachloride proceeds in dif ferent ways depending on whether it is initiated by light or peroxides:

Av

(C 6H 5 ) 2Hg + 2CCU - C 6 H 5 HgCl + C2Cl6 + C6H5Cl [277, 278] ( 1 )

(RCOO)i (C6H5)2Hg + CCl4 — C6H6HgCl + C6H5CCl3 [279] (2)

The above reaction (2) applies also to the decompositions of /3-chlorovinylmercury compounds in CCl4 in the presence of acetyl , benzoyl and other peroxides [279].

Reaction between diphenylmercury and CCl4 under the influence of ultra-violet irradi-ation [278]. A solution of 5 g of diphenylmercury in 75 ml of CCl4 is placed in a quartz flask provided with a reflux condenser because the irradiation (50 hours; quartz mercury lamp PRK-2) gives rise to slow boiling. After irradiation, the solution assumes a brownish tint and leaflets of phenylmercury chloride separate out (3.0 g). After crystallization from acetone, the melting-point is 257°C.

The CCl4 solution is steam-distilled and the carbon tetrachloride coming over gives on evaporation a residue of hexachioroethane. After sublimation, the latter melts in a sealed capillary at 185°C.

Nitration of the CCl4 distillate allows separation of p-chloronitrobenzene; m.p. 83°C (after crystallization from acetone and methanol). Steam-distillation gives 1.75 g of a viscous brown mass, which is worked up with hot acetone. The acetone solution gives, on cooling, a further 0.5 g of phenylmercury chloride; m.p. 257°C; 0.8 g of unreacted diphenylmercury (m.p. 125°C after recrystallization) is recovered from the mother liquor.

The ser ies o-anisyl > phenyl > tolyl > p-bromophenyl [633] > a -naphthyl > methyl [75] obtained by Razuvaev et al. on the basis of the ease of splitting away f r om the mercury atom in RHgR' in homolytic reactions

R H g R ' - f CCl4 hZ RHgC l + R'Cl + (CCl3)2

/IV R H g R ' + CHCl 3 - RHgC l + R ' H + (CCl3)2

di f f e rs considerably both f rom Kharasch's ser ies based on reactions proceeding by a heterolytic mechanism and f r om a ser ies derived by Nesmeyanov, Borisov et al. [279a] on the basis of peroxide-initiated decompositions of RHgR' in CCl4 (mentioned ear l ier in this chapter).

Both the photolysis and the pyrolysis of diphenylenemercury results in biphenylene [580],

Following the photolysis of o-iodophenylmercury iodide in ben-zene, the products were found to contain 42% of biphenyl, 36% of o -terphenyl and 21% of bis-o -diphenylylmercury, as well as in-organic mercuric salts [537]. The products of the photolysis of



o -iodophenylmercury iodide in cyclohexane are benzene and mercuric iodide [537].

A 25% yield of 1,2,3,4-tetraphenylnaphthalene has been obtained by 8 hours of ultra-violet irradiation of o- iodophenylmercury iodide in benzene in the presence of tetracyclone [634]:

hv

HgI

§ + H g I 2

X6H5 C6H5

O=C \ ^C-C6H5

C6H5 C6H5

The photolysis of b is- o -iodophenylmercury proceeds in the same way [634], via dehydrobenzene formed as an intermediate [537, 634].

The reaction between N-bromosuccinimide and diarylmercury changes to a radical mechanism in the presence of ultra-violet light [75] (see p. 282 ear l ier in this chapter).

q ) Cis-trans Transformations of Unsaturated Organomercury Compounds

Interconversions between the geometrical isomers of ethylenic organomercuries can be accomplished by ultra-violet irradiation, by peroxides and sometimes by moderate heating (Nesmeyanov, Borisov et al. ) . In the presence of ultra-violet, d i - trans-/3-chloro-vinylmercury transforms smoothly into the c is- isomer and trans-/3-chlorovinylmercury chloride in absolute alcohol, toluene, or best in benzene, passes into the c is -sa l t inay ie ld of 23.7% [635]. On the other hand, the czs-mercury derivative of stilbene irradiated by ultra-violet transforms into trans [541],

Transformation of trans, 2rans-di-(/?-chlorovinyl)mercury into its cis, cts-isomer [635]. Ten grams of the trans,trans-isomer (m.p. 71-72°C) are placed in a quartz tube, fused and then irradiated for 17 hours with a PRK-4 quartz lamp from a distance of 2-3 cm. On cooling to room temperature, the molten substance does not crystallize. After the irradiation, the slightly yellowed liquid mass is distilled under vacuum; 4.5 g (yield: 45%) of a colorless liquid (b.p. 56°C/6.4 x IO - 3 mm) are collected.

When the period of irradiation is extended to 76 hours, the yield rises to 65.5%. The residue in the distillation flask is dissolved in 15 ml of benzene, worked up with activated carbon and fi ltered. Cooling of the colorless filtrate gives crystals of trans-/3-chloro-vinylmercury chloride; weight: 3.8 g; m.p. 122-123°C.


Transformation of irans-/3-chlorovinylmercury chloride into its ois-isomer [635]. Four grams of the Jrons-salt in 25 ml of dry benzene are irradiated with a PRK-4 mer-cury quartz lamp for 50 hours at room temperature from a distance of 2-3 cm and the resulting turbidity removed with activated carbon. On cooling, the clear solution gives 2.4 g of crystals; m.p. 123-124°C (with decomposition). The solvent is removed from the filtrate by gentle heating, under suction from a water pump, and the residue sub-jected to fractional crystallization from a 1:4 mixture of benzene and petroleum ether. The crystals are in the form of small plates (the initial substance consists of needles). After repeated recrystallization, the melting-point is 78°C. Yield: 0.95 g (24%).

Transformation of cis-cwnercuri-bis-stilbene into irans-a-mercuri-bis-stilbene [541]. Cis- a-mercuri-bis-stilbene (1 g) in 50 ml of chloroform is irradiated for 3 hours with a PRK-4 quartz lamp. Fine needles begin to precipitate after 30 minutes. Filtration of this precipitate gives 0.50 g (50%) of the Srans-isomer, melting without recrystallization at 243-244°C. Evaporation of the chloroform gives 0.3 g (30% of the starting amount) of the c is- isomer.

The tfrans-isomers of the mercury derivatives of stilbene could not be transformed into the cis - f o rm ; ultra-violet irradiation resulted mere ly in decomposition.

Trans-f$-chlorovinylmercury chloride transforms into the cis-isomer in the presence of peroxides [632] in peroxide-containing xylene, in the presence of benzoyl, acetyl, or sodium peroxide in xylene, toluene, dioxan, or CCl4 on heating to 95-100°C. Hydro-quinone prevents the isomerization f rom taking place.

The products of the addition of mercuric salts to unsaturated hydrocarbons generally decompose with liberation of the starting unsaturated compound when they are heated above their melting-temperature [127], In certain cases, at not too high temperatures, the thermal decomposition is accompanied by a cis - trans trans-formation. Thus, cis - a-mercuri-bis-st i lbene converts into the trans-form on heating [541].

Isomerization of cis-ct-mercuri-bis-stilbene into the irons-form [54l ] . The cis -isomer (0.5 g) is heated in a sealedtubefor 4 hours at 140-160°C. Metallic mercury sep-arates out at the bottom of the tube. The contents are then worked up successively with benzene and dioxan. The dioxan extract gives 0.25 g (50%) of the trans isomer (m.p. 242-244°C) and the benzene extract 0.1 g of Jrons-stilbene (m.p. 121-122°C).

r ) Anion Exchange in Organomercury Salts

Organomercury halides are obtained directly f rom soluble RHgX (X = OH, CH3COO1 NO3) by the addition of K, Na, or Ca halide. The RHgHal precipitate out [636-644]. RHgOH are made f rom RHgHal by heating the latter with equimolar proportions of s i lver oxide [620, 645-647] in water, alcohol, or n.athanolic alkali [620, 648, 655]. The required salt, RHgOH, is obtained after f i l ter ing off the Ag(K)Hal f rom the f i l trate (after evaporation). The structures of methylmercury hydroxide and tri (methylmercuri)oxonium hydroxide [ (CH3Hg)3O]+OH- will be discussed below.

Transition f rom one organomercury salt to another can be



accomplished by neutralizing the solution of the f o rmer with appropriate acid [649]. Nitrates, acetates, sulfates and perchlor-ates are prepared f rom the halides by heating the latter in water or alcohol with the corresponding s i lver salts [372, 442, 650-653]. The s i lver halide is then f i l tered off and the f i l trate is evaporated.

Preparation of a-naphthylmercury nitrate [442]. Equimolar proportions of a-napthyl-mercury chloride dissolved in hot acetone and alcoholic si lver nitrate are mixed and the mixture filtered. Evaporation of the residue gives a-naphthylmercury nitrate in the form of fine needles; m.p. 137-138°C.

Phenylmercury nitrate has also been made f rom phenylmercury acylates and nitric acid [654]. Certain hydroxides have been ob-tained f rom the acetates by the action of aqueous [655, 656] or alcoholic [657] alkalis or by the action of aqueous alkali on the acylate dissolved in an organic solvent, for example benzene [658].

C6H5CH2HgCl and potassium fulminate in methanol (with cooling) gave C6H5CH2HgCNO [659].

Anions can also be exchanged in RHgX by the usual methods used in the preparation of salts: interaction of the organomercury salt with an inorganic salt of a metal forming with the anion of the RHgX a soluble salt which is washed out [660] or an insoluble salt which is f i l tered off [661] - or heating of the organomercury salt of a volati le acid with an involatile acid [662].

Alkylmercury sulfides (RHg)2S and RHgSHgR' can be made in the pure f o rm in alcohol f rom the corresponding halides and aque-ous sodium sulfide [663]. The interaction of various classes ,pf RHgX with ammonium sulfide and with thiosulfates also leads to (RHg)2S [663a].

In many cases it is preferable to symmetr ize the salt and to heat the resulting fully substituted organomercury with another mercuric salt, with or without a solvent, according to the scheme:

2 R H g X R 2 Hg ; R 2 H g + H g X 2 - » 2 R H g X

Preparation of methylmercury hydroxide [648] (see [664, 665]). Methylmercurybromide (30 g) is wetted with methanol, covered with 100 ml of methanolic KOH and heated for 30 minutes on a water bath. It is then filtered hot, treated with 20 ml of water, evapora-ted under a pressure of 17 mm at 60°C, treated with a little water and filtered once more. The precipitate of methylmercury hydroxide is dissolved in 40 ml of pyridine at 80°C and decanted from the alkali which separates out again. The pyridine solution is fi ltered and cooled; The resulting needles of methylmercury hydroxide are f i ltered off, washed with several portions of absolute ether and dried over CaCl2. Yield: 16 g (68%); m.p. 137°C. The material should be stored in a vessel closed with a ground-glass stopper. Other RHgOH have also been obtained: R = C2H5 (m.p. 37°C), n-C3HT (m.p. 78°C), n-C4H9 (m.p. 68°C), n-C5Hu (m.p. 50°C); n-C6Hi3 (m.p. 54.5°C); n-C7Hi5 (m.p. 51°C), n-CieHa3 (m.p. 78°C), CgH5 (decomposition at about 200°C), a-CioH7 (decomposition at about 280°C) [648],

Alkylmercury hydroxides consist in fact of a mixture of an alkyl-mercury oxide (AlkHg)2O and tri (alkylmercuri)oxonium hydroxide


[ (AlkHg)3OJ +OH - [664, 665J. On dehydration by boiling in toluene solution or under vacuum, this mixture converts into the oxide [the melting-points of (AlkHg)2O are as fo l lows: Alk = CH3 139°C, C2H5 47°C, n-C3H7 98°C, iso-C3H? 135°C, C4H9 74°C (Grdenic)] .

The salts [ (A lkHg) 3OJ +X - can be made in several ways. (a). By careful treatment of the (AlkHg)2O in methanol or acetone

with acid; this method has been used to obtain t r i (methylmercur i ) -oxonium fluoroborate [664J, carbonate [665] (by passing CO2 into methanolic (CH3Hg)2O), perchlorate [665], nitrate [665], t r ichloro-acetate [665] and dichromate (action of 10% aqueous CrO3 ) .

(b). By the addition of RHgX to (RHg)2O (in methanol); this has been used for tri (methylmercuri)oxonium sulfate and carbonate.

(c). By double decomposition of (CH3Hg)3OX and KX ' , X ' = CIO4, BF 4 (in methanol, in acetone in the case of the action of KMnO4); this method has also been used for the acetate, hexafluorophosphate and reineckate.

(d). Tri (methylmercuri )oxonium nitrate has also been made f rom (CH3Hg)2O and AgNO3.

The formation of tri (alkylmercuri)oxonium dithizonates f rom t r i -(alkylmercuri)oxonium salts and dithizone has been described [729].

Preparation of tri(methylmercuri)oxonium perchlorate [665]. A solution of 5 g of bis-(methylmercury) oxide in 20 ml of methanol is neutralized by the dropwise addition of "70% HCIO4 dissolved in three volumes of the same solvent. The perchlorate (m.p. 148°C) is precipitated out with ether.

Tri (methylmercuri )oxonium hydroxide base has been obtained by reacting a solution of KOH in methanol with the perchlorate [665],

Tri (methylmercuri )sulfonium salts have been made in an analo-gous manner, by shaking a benzene solution of bis-methylmercury sulfide (see below for the preparation of this compound) with aqueous CrO3 ; the resulting dichromate was converted into nitrate (CH3Hg)3S +NO3 - by double decomposition with lead nitrate ( t r i -turation with a small amount of ethanol).

The course of the reaction of alkylmercury bromides with tert iary phosphines depends on several factors , including the nature of the alkyl group, the phosphine and the reaction medium. Ethylmercury bromide adds to phenyldimethylphosphineandtotriethylphosphinein methanol to g ive , respect ively, (EtHgPMe2Ph)Br and (EtHgPEt3)Br.-The product of the reaction of methylmercury bromide with t r i -ethylphosphine in ether, [CH3HgP(C2H5)3JBr, has been isolated in crystal l ine form [667]. For the reactions between phenylmercury acetate and tert iary phosphines, see also [55c]. Theproducts of the interaction between phenylmercury acetate and triethyl phosphite contained phenylmercury dialkyl phosphite [55c] (see Chapter 13).

Preparation of bis-methylmercury sulfide [663]. Awarm solution of 0.5 g of Na3S.9H20 (pressed out on f i l ter paper) in 10 ml of alcohol is mixed with a saturated solution of 1 g of methylmercury chloride in 10 ml of alcohol. The reaction mixture is cooled under



running water. Broad leaflets of bis-methylmercury sulfide separate out (0.7 g, 90%). The material is recrystallized from alcohol or chloroform; m.p. 145°C.

Preparation of methylmercury ethylmercury sulfide [663]. A warm solution of 5.0 g of Na2S.9H2O in 50 ml of alcohol is added to 5.0 g of methylmercury bromide in 50 ml of the same solvent and the mixture treated with a warm, saturated, alcoholic solution of ethylmercury bromide (5.0 g in approximately 50 ml). The entire mixture is heated, fi ltered rapidly in the hot and the filtrate cooled. The resulting grayish precipitate (broad leaflets from chloroform) weighs 7.0 g (89%); m.p. 73.5°C.

Methylmercury n-propylmercury sulfide (m.p. 51 °C ) has been made in the same way.

Synthesis of bis-(ethylmercury) sulfide [663]. A warm alcoholic solution of 1.6 g of Na2S.9H2O is added gradually to a warm alcoholic solution of 4.0 g of ethylmercury bro-mide and the mixture cooled under running water. This procedure gives 3 g (yield: 94%) of a gray precipitate which after two recrystallizations from benzene forms broad leaf-lets; m.p. 105°C. The same method has been used to make bis-n-propylmercury sulfide (m.p. 70°C, from alcohol), bis-isopropylmercury sulfide (m.p. 59.5°C) and bis-n-butyl-mercury sulfide (m.p. 59°C).

Preparation of ethylmercury nitrate [668]. A solution of 4.25 g of AgNO3 in warm water is added to 9 g of ethylmercury iodide (or an equivalent amount of the bromide or chloride) in 300 ml of alcohol and the mixture refluxed for 2 hours on a water bath. Water (200 ml) is then added, the alcohol distilled off, the water evaporated out under vacuum and the resulting dry, grayish, ethylmercury nitrate purified by reprecipitation with petroleum ether from the smallest possible volume of methanol; m.p. 87°C.

Preparation of benzylmercury nitrate [669]. Benzylmercury chloride (11.35 g) in ether is mixed with a solution of 5.89 g of AgNO3 in ethanol. After 1 hour of shaking, the AgCl is fi ltered off, the filtrate evaporated at a low temperature under vacuum and the residue recrystall ized from ether; white needles; m.p. 90-91°C (with decomposition).

Synthesis of benzylmercury hydroxide from benzylmercury chloride and moist silver oxide [690]. Benzylmercury chloride (5.00 g) in 100 ml of hot methanol or ethanol is treated with moist silver oxide obtained by precipitation from 3.25 g of AgNOa (20% excess). After 4-5 hours at 80cC on a water bath, the AgCi is filtered off and the excess of alcohol distilled on cooling. Yield: 2.46 g (58.4%); m.p. 125-127°C (from alcohol).

Synthesis of benzylmercury hydroxide from benzylmercury chloride and sodium hydroxide [620]. Benzylmercury chloride (5.00 g) in 100 ml of hot methanol or ethanol is treated with 0.62 g of NaOH dissolved in the same alcohol. The mixture is heated for 2 hours at 80°C on a water bath. The precipitate of NaCl is filtered off and about two-thirds of the alcohol distilled out. The yield of benzylmercury hydroxide is 4.38 g (92.8%).

Synthesis of phenylmercury hydroxide [657]. To a solution of 12 g of phenylmercury acetate in 1 l iter of isopropanol heated on a water bath is added, gradually, 10 ml of 30% KOH. The heating is continued for another hour and the solution diluted with an equal volume of water, f i ltered and evaporated down to about 200 ml. Crystals of phenylmercury hydroxide appear on cooling and are recrystallized from hot water (7.9 g, 75%; m.p. 200°C, with decomposition; see also [670]).

Synthesis of phenylmercury hydroxide [658]. A solution of 33.6 g of phenylmercury acetate in hot benzene into which 0.15 mole of 5-10% NaOH has been stirred is distilled for 20 minutes to remove the solvent. The product separates out on cooling and is re-crystallized from water. The yield is 75-79%.


Similar procedures were used to prepare to ly lmercury, mesi ty l -mercury and nitrophenylmercury hydroxides.

Preparation of phenylmercury hydroxide f rom the nitrate-hydrox-ide PhHgNO3.PhHgOH has been described [671]. The same compound has been made in 94.6% yield [670] by boiling aqueous NaOH for 1 hour with (C6H5Hg)2NH2OCOCH3, formed f rom boiling solutions of NH4OH and C6H5HgOCOCH3. The reaction of phenylmercury acetate itself with NaOH is said to be less convenient [670].

Preparation of phenylmercury fluoride [672], A solution of 40.6 g (0.17 mole) of freshly precipitated mercuric oxide and 14 g (0.35 mole) of 50% HF in 400 ml of water is shaken for 5 hours with 78 g (0.25 mole) of phenylmercury chloride moistened with ethanol. The precipitate is fi ltered off and extracted with 400 ml of boiling ethanol. A small amount of solid appears on cooling. The solution is decanted and concentrated in vacuum. The residue is extracted again with boiling ethanol and fi ltered. On cooling, the filtrate yields 32 g (43%) of phenylmercury fluoride; m.p. 170°C. Following re-crystallization from chloroform, the melting-point rises to 171°C.The yield can probably be increased by extending the reaction time.

Remarkable unstable salts (RHg)2Fe(CO)4 are formed by the action of CaFe(CO)4 [673] or carbonyliron hydrides [107] on RHgOH (see Chapter 13).

Methylmercury hydroxide-nitrate has been made by the action of an insufficient amount of HNO3 on methylmercury oxide or hydroxide [674], or by the action of mercuric oxide or hydroxide on methyl-mercury nitrate [675]. For the preparation of phenylmercury hydroxide-nitrate see [676].

The action of CO2 on RHgOH in alcohol gives RHgHCO3, and the latter and CS2 in the absence of alcohol yield RHgSH [739],

The methods mentioned at the beginning of this section have been used to prepare ethylmercury phosphate f rom ethylmercury hydroxide and phosphoric acid [668], alkylmercury [678-680] and ary lmercury [677, 679-682] diaryl and dialkyl phosphates [681] and dialkyl thiophosphates and 3-pyridylmercury metaborate [683]. The preparation of the following compounds hasalsobeen reported: alkylmercury and arylmercury phenoxides, including the polychloro-phenoxides [64, 684-697], alkylmercury and ary lmercury alkoxides [698], alkylmercury naphthoxides [619], alkylmercury [686, 688, 699a] and phenylmercury [699, 699a] 8-hydroxyquinolinates, alkyl-mercury salts of certain carboxylic acids [700, 701], oxalates of mercurated phenols [702], phenylmercury sulfates, phenylmercury sulfanilates, in particular the compound C 6 H 5 H g O 3 S C H 2 C H 2 ( C H 3 ) N O C ( C H 2 ) 7 C H = C H ( C H 2 ) 7 C H 3 [703], alkylmercury sulfonates [704], 2- (3-C6 H5 HgO3 SC joH6 )2CH2 ( f rom phenylmercury acetate and the corresponding acid 2-(HO3SC10H6)CH2CH2 in alcoholic solution [705]), compounds of the type C 6 H 5 H g N R 3 O R ' (R = alkyl, R' = polyhalogenoaryl [706]), alkylmercury sulfides [679, 707-709] and alkylmercury perthiocyanates [710, 711]. *

Alkyl (aryl ) mercury mercaptides and; thiophenoxides RHgSR' are easily obtained [712, 713], usually by the interaction between



the alkyl (aryl )mereury acetate or hydroxide and R'SH or R'SNa, in aqueous or alcoholic solution in the cold. This method has been used to prepare RHgSR' (where R is alkyl or aryl and R' is alkyl [714], CH3CONH [715, 716], polyalkoxyalkyls [717],alkyls containing a dialkylamino group [718, 719, 721-724], e.g. (CH3)2NCH2CH2 [719, 721-724], substituted pyrimidyl, pyridazyl [715], benzothiazolyl [725], triazines [726, 727],troponyl [728, 759]andthiodiazolyl [720]).

Methylmercury dithizonate, CH3HgSC(N=NC6H5)NNHC6H5,has been made f rom methylmercury bromide and dithizone [729]. RHgSR' have been obtained by a s imi lar method [730] f rom mercaptans and alkyl -(aryl )mercuriacylamides or -sulfonamides, for example

N - H g R

|| ^ O R ' S H , RHgSR' , R ' S H C6H5SO2N(HgR) C6H4OCH3-P

CO

Examples of the replacement of the anion at the mercury in products obtained by the addition of mercuric salts to olefins by the SR group are also known; thus, the acetoxy group has been replaced by the SR residue following the action of mercaptans or thiophenols on the products of the addition of mercuric acetate in water to l -decen-10-carboxyl ic acid and its ester [731].

A case is known in which the replaced anion is a theophylline residue [732], The chloride anion in y - c h l o r o m e r c u r i - / 3 - h y d r o x y (and methoxy)propyltheobromine has also been replaced by barbi-turic acid residues [733].

According to [734], the products of methoxymercuration of alkenes f o rm, with ammonia and amines, ammonium salts RHgNR'H2X (R' = H or Alk; R = C6H5CH(OCH3)CH2, CH3(CH2)7CH(OCH3)CH2, 2-meth-oxycyclohexyl, CH3(CH2)12 CH(OCH3)CH2).

Other examples of the replacement of anions in adducts of me r -curic salts to unsaturated compounds are mentioned in Chapter 6.

Alkyl (aryl )mercury dioctyl sulfosuccinates have been made by brief boiling of alkyl (aryl )mercury acetates with dioctyl sulfosuc-cinate [735]. Alkyl (aryl )mercury derivatives of cyanoguanidine have been prepared f rom the latter 's s i lver derivatives and RHgHal [736], or f rom cyanoguanidine and RHgOH [737]. In RHgBr (R = CH3, C2H5, n-C3H7, n-C4Hg), the bromine atom is exchanged by labeled bromine on reaction with HgBr*2 , the isotopic equilibrium being established within 10 minutes [738]. Organomercury xanthates RHgSSCOR' can be made by the action of CS2On alcoholic RHgOH [679, 739]. When phenylmercury hydroxide is mixed at room tem-perature with CS2 in the absence of alcohol, diphenylmercury is obtained in 30% yield [740]. The reaction probably involves inter-mediate formation of phenylmercury sulfide (see Chapter 13 and [739]).

Vinylmercury xanthate (and thiocyanate) have been made by

(


exchanges between vinylmercury acetate and an alkali metal xan-thate (and thiocyanate) [514],

Preparations of ethylmercury N-alkyl dithiocarbonates and dithiocarbamates have been reported [740-742], Theyareconducted in water, in the cold, f rom the sodium salts of the corresponding dithio acids and ethylmercury chloride in the presence of t r i -ethanolamine and ammonium acetate.

The interaction of bis- (ethylmercury) phosphate with N-a lky l -N-phenyldithiocarbamate in aqueous solution in the cold, or of ethyl-mercury chloride with methylaniline and CS2 in alkaline solution, results in ethylmercury N-alkyl-N-phenyldithiocarbamates [743].

Phenylmercury acetate transforms into 8-phenylmercuroxy-quinoline polychlorophenoxide on boiling in benzene either with 8-hydroxyquinoline polychlorophenoxide or with a mixture of poly-chlorophenol and 8-hydroxyquinoline.

Conversions of salts RHgX in which the anion X is replaced by a residue combining fa ir ly strongly with the mercury via N or S and containing atomic groups promoting solubility in water are particularly important for the practical aim of preparing water-soluble organomercury compounds. Compounds soluble in aqueous alkalis are obtained by condensation of organomercury salts with mercaptocarboxylic [744-755, 757, 758,' 760, 762, 763, 765, 766, 780], mercaptosulfonic [761, 763], or mercaptoarsonic [745] acids, according to the reaction

R H g X + HSR' , R H g S R ' + H X

where R' is a radical containing the COOH1SO3H, or AsO3H2 group. For example, salts RHgSR' (R' = C11H23COOH) have been made by the action of w-mercaptoundecanoic acid on alkylmercury phos-phates [767].

ClCH2HgSR have been made f r om ClCH2HgCl and RSH (mercap-tomalic acid or its esters ) by boiling in methanolic solution [768]. Esters R " CH(SHgR )COOR have been prepared by the interaction of R'HgCl with the corresponding mercapto acid in cold alkali [769]. The preparation of alkylmercurithiosalicyl ic esters will be found in [770].

Preparation of ethylmercurithiosalycilic acid [765]. Asolutionof 2.5moles of NaHCOa in 250 ml of water is added drop by drop to a suspension of 1 mole of thiosalicylic acid and 1 mole of ethylmercury bromide in 750 ml of water. The mixture is heated to 50°C, cooled, fi ltered with charcoal to remove the excess of ethylmercury bromide and acidified with 162 ml of acetic acid; the precipitate is washed with 600 ml of water, stirred with 500 ml of ice-cold absolute ethanol, washed again with cold alcohol and dried at 50°C. Yield: 75-80%; m.p. I l l 0 C .

Preparation of phenylmercurithioglycolic acid [746]. A suspension of IOg OfC6Hs HgOH in 80 parts of ethanol is worked up with 10 g of thioglycolic acid. Dilution with water gives fine needles; m.p. 114°C.



Interactions of organomercury salts or bases with imides [755, 756, 764, 771-781] ( for example succinimide, phthalimide, etc), imines [776, 782] ( for example quinonimine) and amides [783-789] ( for example acetamide, arylsulfonamides) [787, 788, 790] g ive water-soluble organomercury derivatives of these nitrogeneous bases, with the mercury bonded directly to the nitrogen.

The action of theophylline and pyrrol idineaceto-2,6-dimethyl-anilide on 8-(2' -methoxy-3-hydroxymercuripropyl )coumarin-3-carboxylic acid in water gives the pyrrol idineaceto-2,6-dimethyl-anilide salt of 8-[2 '-methoxy-3'- (7-theophyl l inylmercuri )propyl ] coumarin-3-carboxylic acid [791].

A rHg- derivatives of theophylline have been obtained by reactions of ary lmercury acetates or chlorides with theophylline in ethanol, after 5 hours of boiling [791-793].

Preparation of N-v inylmercur i - imides by the reactions of v inyl-mercury salts with imides in the presence of bases has been pro -posed [514].

The compound

has been made [793] f rom AlkHgOH and alkylmercaptobenzimid-azole , as well as the analogous compound f rom 2-mercaptobenz-oxazole [756].

Preparation of O-hydroxyphenylmercuri succinimide [774]. Succinimide (3.3 g) in 18.7 ml of water is added to 10.95 gof o-hydroxyphenylmercury chloride in 25 ml of warm water, the mixture cooled as much as possible without the formation of a precipitate and 18.7 ml of 10% KOH added. The crude product, obtained after shaking and cooling, is recrystallized from 200 ml of ethanol and 100 ml of water. Yield: 72.3%; m.p. 232-235°C.

On the other hand, the SAr ' group in ArHgSAr ' can be replaced for a halogen by the action of benzoyl chloride [794, 795], aryl sulfochlorides [794, 795] and aryl sulfoiodides [794, 795], or for the N-succinimido group by the action of bromosuccinimide [795]. The R' group in RHgSR' can also be exchanged for R " by the action of R " S S R " , (R"S)2Hg, or HSR" [794]. For example, ethylmercuri-thiosalicylate and m-tolylmercurithioglycolate have been made to enter into exchange reactions with dithizone [796]:

[Dz = C6H5N=NC(S-)=NNHC6H5 ] , by shaking their weakly alkaline aqueous solutions with a benzene solution of dithizone at roo i temperature.

On prolonged standing in aqueous solution (faster in direct

N

C 2H 5HgSC 6H 4COO- + DzH ^ DzHgC 2 H 5 + HSC6H4COO


sunlight) O-C2H5HgSC6H4COONa transforms spontaneously into O-C2H5HgSC6H4COOHgC2H5 [797]. ArHgSAr is transformed into ArHgOCOR by RCOOH [798].

Salts of phenylmercury with anions capable of polymerization (jp-vinylbenzoate [553], acrylate and methacrylate) have been obtained by neutralizing phenylmercury hydroxide with the c o r -responding acids in alcohol [553, 676, 799].

The products of the interaction of a r y l m e r c u r y hydroxides with nitroanilines and nitronaphthylamines in aqueous or alcoholic solutions, at room temperature, have been shown to be HgN-derivatives by means of in fra-red spectroscopy [800]; the a r y l -mercury derivatives of nitrosophenols, obtained under the same conditions, have a quinone-oxime structure in the solid state. In solution, a metallotropic equilibrium

OHgR 0 - 0 O

6 < > 6 — 6 I I H >1

NO NO NO- NOHgR

is set up [801], The a r y l m e r c u r y derivatives of nitrosoanilines exhibit a benzenoid structure [802], A benzenoid structure

RHgO N=NC 6H 6

has been demonstrated for the p -dimethylaminophenylmercuri derivatives of hydroxyazo compounds [803], and structure , such as

C6H5COCC6H5

VHgAr x C 6 H 5

for the derivatives of the phenylhydrazones of anthraquinone, a c e -naphthenequinone and benzil [803].

The interactions between a r y l m e r c u r y hydroxides and phenols under mild conditions (in alcoholic solution, at room temperature and with heating [804]) give r i s e to a r y l m e r c u r y phenoxides in-capable of transforming into asymmetr ica l hydroxyarylmercury compounds (compare the action of a r y l m e r c u r y hydroxides on phenols under vigorous conditions, which according to certain authors leads to arylmercuriphenols; cf . Chapter 12.

In accordance with its halogen-like propert ies , during the reactions between Hg(CF3)2 and KHal the C F 3 group enters into the composition of the complex anion: K2IHg(CF3)2Hal2] [805, 806]. However, cryoscopic measurements on aqueous solutions refute this point of view about their s tructure, and suggest that such



compounds .are 1:1 adducts of Hg(CF3)2 and Hal" [714a], The inter-actions of diethylmercury with triethylsilane [795a] and penta-ethyldisilane [795b] give r i s e to compounds C2H5HgSi(C2H5)3 and C2H5HgSi(C2H5)2Si(C2H5)3 together with other products (see Chapter 16). CeH5HgSi(C6H5)3, obtained by the action of diphenylmercury or phenylmercury bromide on (C6H5)3SiLi, is unstable and immediately disproportionates into Hg and (C6H5)4Si [795c],

The formation of clathrate compounds of diethylmercury with tr i -o-thymotide has been described [807].

The association of R H g + with sulfhydryl and other functional derivatives of proteins has been studied [808-818].

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(1964). 809. S. Y . Singer, J. E. Fothergil l and J. R. Shainoff, ibid., 82,

565 (1960). 810. L. R. McDonnell, R. B . Silva and R. E. Feeney, A r c h s

Biochem. Biophys., 32, 288 (1951). 811. L. Hellerman, Physiol . Rev. , 17, 454 (1937); Cold Spring

Harbor Symp. quant. Biol . , 7, 165 (1939);Chem. Abstr . , 35, 6985 (1941).

812. L. Hellerman, F. P. Chinard and V . R . D e i t z , J. biol. Chem., 147, 443 (1943).

813. P . D. Boyer , J. Am. chem. Soc., 76, 4331 (1954). 814. A. D. Swenson and P. D. Boyer , ibid., 79, 2174 (1957). 815. O. L. Polyanovskii , Biokhimiya, 27, 734 (1962). 816. G. Szabolcsi and E. Biszku, Biochim. biophys. Acta, 48,

229 (1961). 817. L. Fedjarn and E. Jellum, Acta chem. scand., 17, 2610 (1963). 818. H. Edelhoch, E. Katchalski , R. H. Maybury, W. L. Hughes,

jun., and J. T . Edsall , J. Am. chem. Soc., 75, 5058 (1953).

CHAPTER 15

Changes in the Organic Moiety in Organomercury Compounds

Changes in the organic part of the molecule in organomercury compounds are in most cases conducted by the usual methods of organic chemistry and are not specific to organomercury deriva-t ives. Reactions of the organic moiety not accompanied by cleavage of the C-Hg bond are not very numerous. In the aliphatic series they are confined to acylation of hydroxyls by means of acyl halides [1, 2] (including the hydroxyls in the mercury derivatives of al-kenediols [3]), acid anhydrides [1, 4, 5] and isocyanates [6], to oxidation of primary alcohol groups to carboxyl [4, 7] by the action of bromine in alkali [7] or alkaline permanganate [4] (the yields are low both in the first [8] and in the second case) and of secondary alcohol groups to keto [9, 9a] (50-60% yields [9]), to reduction of the aldehyde groups to alcohols (for example, by means of alumi-num isopropoxide [10]), to salt formation with mercurated acids, to esterification of acids by the action of diazomethane [11], to a replacement of the alkoxy group by the action of carboxylic [12-14] and sulfonic [12] acid amides for acyl- or sulfinimino groups and to the entrance of bisalkylmercuriacetylenes [15] (cf. ^-chloro-vinylmercury chloride [16]) into diene syntheses with cyclones. The acylals of mercurated oxo-compounds are hydrolysed by strongly diluted sulfuric acid in 50% alcohol.

Synthesis of 2-iodomereuriethyl benzoate [ l ] , /3-Hydroxyethylmercury iodide (IOg) in 10 ml of a 10% solution of KI a r e cooled to 0°C and shaken with 10 g of benzoyl chloride, taking c a r e that the temperature does not r i s e above 0°C [2], T h e result ing white pre-cipitate is purif ied [2] by washing its chloroform solution with three portions of 10% NaI and by r e c r y s t a l l i z a t i o n f r o m a mixture of chloroform and petroleum ether. T h e yie ld of such purified m a t e r i a l is 16%; m.p. 1 1 5 - 1 1 8 ° C .

T h e react ion must be c a r r i e d out at 0°C. If this precaution is not observed, or if the product is c r y s t a l l i z e d f r o m ethanolic N a I a s r e c o m m e n d e d b y Sand [1], energet ic desoxy-mercurat ion takes place and the final product is mainly benzoic acid [21.

Reduction of chloromercuriacetaldehyde to /3-hydroxyethylmercury chloride [lC

C l H g C H o X . H O ( i s o ' G 3 H , 0 ) 3 1 ' c iHgCH 2 C H 8 O H

(1) Preparat ion ; aluminum isopropoxide [18]: aluminum shavings are treated with

456

CHANGES IN THE ORGANIC MOIETY 457

aqueous NaOH till considerable evolution of hydrogen takes place, washed with water till the washings a r e neutral, treated with 1% HgCl2 solution, washed s u c c e s s i v e l y with water, alcohol and ether, and dried. A round-bottom f lask fitted with a ref lux condenser is then charged with 1 g of the Al shavings, 30 m l of absolute isopropanol and a few c r y s t a l s of iodine. Reaction begins already at room temperature, and the f lask i s heated on a water bath t i l l all the metal d i sso lves . T h e solution i s f i l tered.

(2) Reduction of chloromercuriaceta ldehyde: 12 ml of Al isopropoxide solution a r e added to 7 g (0.04 mole) of chloromercur iaceta ldehyde and the mixture set aside f o r 3 days. T o d isso lve the agglutinated precipitate 10% NaOH is added and the solution then f i l tered. A current of CO2 is used to precipitate /3-hydroxyethylmercury chlor ide f r o m the f i l t rate . T h e m a t e r i a l i s r e c r y s t a l l i z e d f r o m methanol; m.p. 1 5 1 ° C .

Preparation of chloromercuriacetone from propylene [9].

CH 3 — CH = CH2 -I- Hg (CH3COO)2 -> CH 3 CH (OCOCH3) C H 2 H g O C O C H 3 K M n ° " K C : '

CH3COCH2HgCl

Propylene is passed into a solution of 16 g of m e r c u r i c acetate in 150 ml of water (till the reaction f o r m e r c u r i c ion becomes negative) and the solution f i l t e r e d . Acetic acid (6 ml) is then added and 5.3 g of KMnO4 s t i r r e d in (in smal l portions). At the end of reaction, the solution is heated f o r 15 minutes on a water bath to precipitate the colloidal MnOp. T h e precipitate is f i l tered off and washed with w a r m water. T h e f i l t r a t e i s treated with a solution of 3.7 g of KCl . Removal of the water under vacuum at room temperature g i v e s 7 .75 g (53%) of the required product; m.p. 102-102.5°C (from methanol). T h e melting-point of the pure compound is 103-104°C.

Dimethyl sulfate has been used to methylate products of the hydroxymercuration of cycloalkenes (see, for example, [19]).

Methylation of a-l-chloromercuri-2-hydroxycyclohexane. Preparation of a-l-chloro-mercuri-2-methoxycyclohexane [ l9 ] .

OH

HgCl

-f KOC4H9-1

OK

HgCl _

(CHa)2SO4

OCH 3

HgCl

S u l f u r - f r e e toluene (80 ml) i s placed in a modified C l a i s e n f l a s k , 15 ml dist i l led out (to r e m o v e the t r a c e s of sul fur) and 0.59 g (0.015 mole) of potassium and 10 ml of dry t-butanol are added to the f l a s k under nitrogen. T h e e x c e s s of the alcohol is dist i l led off a f ter the potassium has dissolved on s t i rr ing and boiling. The remaining suspension i s cooled, treated with 1.68 g (0.005 mole) of a - 1 c h l o r o m e r c u r i - 2 - h y d r o x y c y c l o h e x a n e and s t i r r e d until the m e r c u r y compound d i s s o l v e s (20 minutes). At the same t ime 15 ml of m a t e r i a l is dist i l led out under vacuum, over 15 minutes, by using a wide tube through which nitrogen is passed in. T h e residue is treated with 1.89 g (0.015 mole) of dimethyl sulfate. The whole m a s s is v igorously s t i r r e d f o r 90 minutes and then 20 ml of 10% NaOH a r e added. T h e mixture is s t i r r e d f o r 10 minutes and the toluene dist i l led out under vacuum. The res idue i s f i l tered off, diluted with 90 ml of 1.5% aqueous NaCl and satura-ted with C O 2 . T h e product (1.57 g, 90%) melts at 1 0 9 - 1 1 2 ° C . Recrys ta l l i za t ion f r o m 8 m l of methanol g i v e s 1.1 g of m a t e r i a l melt ing at 1 1 3 - 1 1 5 , 5 ° C .

The action of methylene iodide on divinylmercury in the presence of zinc in tetrahydrofuran at 40°C leads to dicyclopropylmercury [20]. For other changes in the organic moiety of the adducts of m e r c u r i c compounds to unsaturated compounds, see under " R e a c -t i o n s of the products of mercury salts to olefinic compounds", Chapter 6.

The nucleophilic attack of the I - ion on C2H5HgCH2Cl in dry or



aqueous acetone, proceeding according to the scheme Slow

t£T

C2H5HgCH2Cl < C2H5HgCH2Cl- — C2HsHgCH2I + KCl

and the solvolysis of U-C4H9HgCH2Cl in 80% aqueous ethanol are second-order reactions [20a].

The reaction CCI

(CFI = CH)2 Hg + Br2 — I (CF IBrCHBr)2 Hg

has been carr ied out [20b], whereas alkenyl compounds of mercury not containing fluorine, including quasicomplex ones, SplitoutHgHal2

under the action of halogens (see Chapters 6 and 14). The action of trimethylamine on bis-iodomethylmercury gives r i s e to a mixture of ammonium salts (1) and (2) [21]:

(ICH2)2 Hg [(CH3)3 NCH2HgCH2IJ+, I- (1)

[(CH3)3 NCH2HgCH2N (CH3)3P 21" (2)

In the aromatic s e r i e s , nitration of mercurated benzene has also been reported [22], giving up to 50% of the w-nitroderivative, as well as functional changes of amino, hydroxyl and aldehyde groups, namely acylation [23-26], alkylation [23, 27-29] and other changes [29] of amino groups (including the preparation of quaternary ammonium salts [30]).

Other reports have dealt with condensation of mercurated amines with aldehydes into mercurated Schiff bases [31], con-densation with dinitrophenylpyridinium chloride [32], leading to c leavage of the pyridine ring, and condensation with acetals [27]. Several authors have studied acylation [33-35] (particularly by the action of dialkyl phosphorochloridates [36, 37]) and alkylation [38, 39] (including allylation [40]) of hydroxyl groups; (the allylation of sodium o-chloromercuriphenoxide with allyl chloride in acetone gives only the symmetrical product R2Hg [40]).

Acetylation of a phenolic hydroxyl. Preparation of 77!-acedoxyphenylmercury chloride [35].

OH OCOCH3

I I (CH3CO)2O

^ J - H g C l C=H=N ' ^ J - H g C l

A solution of 3 g of m-hydroxyphenylmercury chlor ide in 6 g of pyridine is treated with 1.2 g of acet ic anhydride in 2.5 g of pyridine. T h e mixture i s set aside f o r a day and then heated f o r an hour on a water bath and poured into water acidif ied with HCl. T h e result ing precipitate is f i l tered off and r e c r y s t a l l i z e d f r o m alcohol. Y ie ld : 100%; m.p. 199-200 C .

The l iterature contains reports on diazotization of amino groups in mercurated amines [31, 41-47] and on the reactions of the resulting


diazonium compounds, on the condensation of mercurated aldehydes with amines into Schiff bases [48] and on esterif ication of m e r c u -rated acids [49]. Mention can also be made of the nitrosation [50] and azo coupling of mercurated phenols [25, 27, 33, 41, 51-53] and amines [41], transformation of mercurated nitrosophenol into nitro-soaniline by means of ammonium salts [50] and transformation of carboxyl ic acids into acid chlorides [49, 53a]. The oxidations of methyl [54, 55] and methylol [56] groups into a carboxyl by alkaline permanganate proceed smoothly, and this method was used to ob-tain, for example, m- [55] and p- [54] chloromercuribenzoic acids and anhydro-2-hydroxymercuri-4-nitrobenzoic acid [57].

Whitmore's [54] oxidation of m-chloromercuritoluene. Preparation of OT-chloro-

Finely ground m-chloromercur i to luene (10 g) is added in smal l portions to 15 g of KMnO4 and 24 g of NaOH in 360 ml of water and ground in this solution. T h e mixture is heated for 15 minutes to 95°C on a water bath, the e x c e s s of permanganate decomposed with alcohol, M n O 2 f i l tered off and the f i l trate acidif ied with HC1. T h e precipitated m - c h l o r o m e r c u r i b e n z o i c acid is f i l tered off , washed careful ly with water and dried. Y ie ld: 6.42 g. C o l o r l e s s , sparingly soluble c r y s t a l s ; m.p. 273°C.

Mercurated nitrobenzoic acids can be reduced to mercurated aminobenzoic acids by alkaline or neutral (but not acid) reducing agents [58].

Rapid exchange between the phenyl groups occurs in the Ph + HgBr-Ph*2Hg system (where Ph* contains labeled carbon) in pyridine or dioxan [59].

In the heterocyclic s e r i e s , in furan derivatives pr imary alcohol groups are oxidized into aldehydes [60], and alkylpyridinium salts (Alk = RsSnOC(CH2)7lX) mercurated in the p-position of the pyridine have been obtained by heating it for a few minutes with AlkHal [30].

Cleavage of the C-Hgbondaccompaniesozonization of the mercury derivatives of alkenes (under the usual conditions, in chloroform) such as cis- and i i rans- l -methyl -2-acetoxy- l -propen- l -y lmercury chlorides (CH3)(H3CCOO)C=C(CH3)HgCl and l - m e t h y l - 2 - a c e t o x y - 2 -p r o p e n - l - y lmercury chloride CH2=C(OOCCH3)CH(HgCl)CH3 [61], or the product of the addition of mercur ic lactate to cyclohexane [62]. Reactions in the anionic parts of salts RHgX are also possible, for example, by heatingoftriethanolamine,methyltriethanolamine, etc. , under vacuum in ethanol with ethylmercury thiosalicylate or with ethylmercury salts of other carboxylic acids yields the c o r r e s -ponding ethanolamide derivatives.

8-Phenylmercuroxyquinoline polychlorophenoxides have been prepared (by boiling in benzene) both from 8-phenylmercuroxy-quinoline and polychlorophenol and from phenylmercury polychloro-

mercuribenzoic acid [55].

CH; COOH


phenoxide and 8-hydroxyquinoline [64]. Bis-pentafluorophenyl-m e r c u r y r e a c t s readily with nucleophilic reagents, exchanging the f luorine:

(CeF5)2 Hg * (p - XC6F4)2 Hg

For example, the reaction requires 1 hour at 100°C with KOH in t-butanol and boiling for 24 hours in methanol. The yields are high. The reaction with hydrazine hydrate proceeds on boiling in alcohol over a period of 6 hours and is accompanied by the for-mation of m e r c u r y , pentafluorobenzene and jo-tetrafluorophenyl-hydrazone[65] .

Bibl iography

1. J. Sand, B e r . dt. chem. Ges. , 34, 1385 (1901). 2. M. M. Kreevoy and G. B. Bodem, J. org . Chem., 27, 4539

(1962). 3. A. N. Nesmeyanov and N. K. Kochetkov, Izv. Akad. Nauk SSSR,

Otdel. khim. Nauk, 76 (1949). 4. J. Sand and F. Singer, Justus Liebig 's Annln Chem., 329,

166 (1903). 5. M. J. Abercrombie, A . Rodgman, K. R. Bharucha and G. F.

Wright, Can. J. Chem., 37, 1328 (1959). 6. A. N. Nesmeyanov a n d R . K h . Freidlina, Zh. obshch. Khim., 7,

2748 (1937). 7. K. A. Hofmann and J. Sand, B e r . dt. chem. G e s . , 33, 1340 (1900). 8. J. Sand and O. Genss ler , ibid., 36, 3699 (1903). 9. I. F. Lutsenko and R. I. Sivkova, Zh. obshch. Khim., 29, 1182

(1959). 9a. T . G. T r a y l o r and A . W. Baker, J. Am. chem. Soc., 85, 2746

(1963). 10. A. N. Nesmeyanov, I. F. Lutsenko and N. I. Vereshchagina,

Izv. Akad. Nauk SSSR, Otdel. khim. Nauk, 63 (1947). 1 1 . D. D. Chiu and G. F. Wright, Can. J. Chem., 37, 1425 (1959). 12. U.S. Pat. 2,329,883 (1944). 13. U.S. Pat. 2,369,339. 14. T . Ukai, I. Yamamoto, S. Kanatoma and A. Kawakami, Chem.

Abstr . , 50, 10,737 (1956). 15. V. S. Abramov and L. A. Shapshinskaya, Dokl. Akad. Nauk

SSSR, 59, 1291 (1948). 16. V. S. Abramov, Izv. Akad. Nauk SSSR, Otdel. khim. Nauk,

330 (1945). 17. A . N. Nesmeyanov, I. F. Lutsenko and R. M. Khomutov, ibid.,

942 (1957). 18. H. Lund, B e r . dt. chem. Ges . , 70, 1520 (1937). 19. W. R. R. Park and G. F. Wright, Can. J. Chem., 35, 1088

(1957).


20. E. Tobler and D. J. Foster , Z. Naturf., B , 17, 135 (1962). 20a. A. Ledwith and L. Phil l ips, J. chem. Soc., 3796 (1962). 20b. K. M. Smirnov, V. A. Ginsburg and A. Ya. Yakubovich, Zh.

v s e s . khim. Obshch, 8, 231 (1963). 21. G. Wittig and K. Schwarzenbach, Justus L iebig ' s AnnlnChem.,

650 1 (1961). 22. F. Challenger and E. Rothstein, J. chem. Soc., 1258 (1934). 23. O. Dimroth, B e r . dt. chem. Ges. , 35, 2032 (1902). 24. M. S. Kharasch, F. W. M. Lomment and I. M. Jacobsohn,

J. A m . chem. Soc., 44, 793 (1922). 25. L. Vecchiotti and A. Michetti, Gazz . chim. ital . , 55, 372 (1925). 26. U. H. Hodgson and D. E. Hathway, J. chem. Soc., 123 (1945). 27. F. Reitzenstein andG. Bonitsch, J. prakt. Chem., 86, 73 (1912). 28. Swiss Pat. 265,755 (1950); Chem. Abstr . , 45, 652 (1951). 29. U.S. Pat. 2,471,622 (1949); 2,415,555 (1947). 30. V. L. Mi l ler and J. K. Chan, J. org. Chem., 28, 1938 (1963). 31. W. A . Jacobs and M. Heidelberger, J. biol. Chem., 20,

513 (1915). 32. F. Reitzenstein and G. Stamm, J. prakt. Chem., 81, 154 (1910). 33. O. Dimroth, B e r . dt. chem. Ges. , 35, 2853 (1902). 34. F. C . Whitmore and E. Middleton, J. A m . chem. Soc., 43,

619 (1921). 35. A. N. Nesmeyanov and E. M. Toropova, Zh. obshch. Khim.,

4, 664 (1934). 36. M. S. Malinovskii, D. G. Yurko and V. B. Tul 'chinskii , ibid.,

30, 2170 (1960). 37. M. S. Malinovskii, D. G. Yurko and N. I. Mashtak, Izv. vyssh.

ucheb. Zaved., Khim. khim. Tekhnol., 4, 514 (1961). 38. O. Dimroth, B e r . dt. chem. Ges . , 31, 2155 (1898). 39. O. Dimroth, ibid., 32, 758 (1899). 40. A . N. Nesmeyanov and R. Kh. Shatskaya, Zh. obshch. Khim.,

5, 1268 (1935). 41. S. S. Guha-Sircar and M. K. Rout, J. Indian chem. Soc., 30,

361 (1953). 42. S. S. Guha-Sircar and M. K. Rout, ibid., 30, 364 (1953). 43. S. S. Guha-Sircar and M. K. Rout, ibid., 30, 366 (1953). 44. S. S. Guha-Sircar and M. K. Rout, ibid., 30, 435 (1953). 45. W. B r a k e r a n d W. G. Christ iansen,Chem. ZentBl . , I , 851 (1937). 46. H. Willstaedt, M. Borggard and K. Myrback, A r k . Kemi, 1,

331 (1949). 47. E. McMahon and C. S. Marvel , J. Am. chem. Soc., 52, 2528

(1930). 48. F. C . Whitmore and E. Middleton, ibid., 45, 1330 (1923). 49. F. C. Whitmore and L. L . Isenhour, ibid., 51, 2785 (1929). 49a. V. M. Stepanov and L. F. Matyash, Zh. obshch. Khim., 33,

316 (1963). 50. M. S. Kharasch and J. F. P iccard, J. Am. chem. Soc., 42,

1855 (1920).


51. E. Bamberger , B e r . dt. chem. Ges . , 31, 2624 (1898). 52. H. H. Hodgson and H. S. Turner , J. chem. Soc., 391 (1943). 53. F. C . Whitmore, E. R. HampsonandG. J. Leuck, J. Am. chem.,

Soc., 48, 1013 (1926). 53a. L. F. Matyashand V . M . Stepanov, Izv. Akad. Nauk SSSR, Otdel,

khim. Nauk, 111 (1964). 54. F. C. Whitmore and G. E. Woodward, J. Am. chem. Soc., 48,

533 (1926). 55. A . N. Nesmeyanov and L. G. Makarova, Zh.obshch. Khim., 1 ,

598 (1931). 56. T . Ukai, Y . Yamamoto and M. Yotsuzuka, Chem. Abstr . , 50,

5665 (1956). 57. P . I. Petrovich, Zh. v s e s . khim. Obshch., 5, 106 (1960). 58. German Pat. 249,725 (1912). 59. E. N. Sinotova, M. F. Vobetskii, Yu. N. Loginov and L. N.

Evtikheev, Radiokhimiya, 1 , 687 (1959). 60. W. J. Chute, W. M. Orchard and G. F. Wright, J. org. Chem.,

6, 157 (1941). 61. A. N. Nesmeyanov, A. E. Borisov and V. D. Vi l 'chevskaya,

Izv. Akad. Nauk SSSR, Otdel. khim. Nauk, 1008 (1954); Dokl. Akad. Nauk SSSR, 90, 383 (1953).

62. G. F. Wright, J. Am. chem. Soc., 57, 1993 (1935). 63. Jap. Pat. 21,197 (1961); Chem. Abstr . , 57, 16,655 (1962). 64. T . Unga, Jap. Pharm. Chem., 34, 237 (1962). 65. J. Burdon, P . L . Coe, M. Fulton and J. L. Tatlow, J. Chem.

Soc., 2673 (1964).

CHAPTER 16

Synthesis and Reactions of Compounds in which the Mercury is not Joined

to the Organic Residue through Carbon

In accordance with its pronounced electrophilic character, m e r -cury has a high tendency to combine with electronegative atoms (O, S, Se, N, sometimes P) present in organic molecules, forming products which are not true organomercury derivatives since the mercury is joined to the organic residue not via carbon but via the corresponding heteroatom.

Among such compounds, those containing the O-Hg bond are the least stable and are relatively difficult to prepare. Compounds with S-Hg and Se-Hg linkages (though the latter have not been so widely studied) form readily and exhibit particular stability. The strength of the N-Hg bond varies between wide limits, but does not exceed that of the S-Hg bond in the mercury derivatives of the organic compounds of sulfur.

Organic compounds containing O-Hg and N-Hg bonds are often the f irst intermediates in the mercuration of oxygen- and nitrogen-containing organic compounds, and transform into compounds m e r -curated at the carbon when the process is carried out under more vigorous conditions, e.g. at a higher temperature or a lower pH.

The bibliography given in this book on organic compounds in which the mercury is linked with the organic radical through O, S, Se, or N is not exhaustive, and both the selection and the dis-tribution of the material treated in this chapter are somewhat arbitrary. Thus, we omitted the mercury salts of carboxylic, sulfonic and other acids, chelates and other compounds of mercury with ionic or weak covalent bonds, but mentioned briefly the mer-cury salts of cyanic, fulminic and thiocyanic acids and similar compounds.

In contrast to the plan adopted in the remainder of the book, where a separate chapter (Chapter 14) has been devoted to the reactions of organomercury compounds, in this chapter the pro-perties and reactions are discussed either at the point where the given compound is mentioned or are outlined for a whole group of similar compounds.

463


For the preparation of compounds RHgZR', where R is an organic radical linked to the m e r c u r y via carbon and R' an organic radical linked to the mercury via a heteroatom Z, see Chapter 14.

a) Compounds with an O-Hg Bond

O - H g D e r i v a t i v e s of A l c o h o l s a n d P h e n o l s

O - H g d e r i v a t i v e s o f a l c o h o l s ( m e r c u r y a l k o x i d e s ) . W h e n m e r -curic chloride is added to a solution of the corresponding sodium alkoxide in methanol or ethanol [1], mercury methoxide and ethoxide are formed. These compounds are unstable.

Preparation of mercury methoxide [ l ] . An orange-red precipitate of mercury methox-ide appears when an equimolar amount of HgCl2 in methanol is added to sodium methoxide in absolute methanol.

No alkoxides have been obtained with the higher alcohols. Compounds (RO)2Hg^Fe(CO)5 , where R = C H 3 , C2H5 and C3H7,

have been made by the action of pentacarbonyliron on a solution of m e r c u r i c acetate (for R = CH3 also on a solution of mercur ic propionate) in the corresponding alcohol. These double compounds are decomposed by concentrated nitric or hydrochloric acid and decompose gradually on being boiled in water [1], They react with HgCl2 in aqueous acetone, for example:

2Fe (CO)5-Hg (OCH3)2 + 3HgCl2 + 2H 2 0 - 2Fe (CO)4-Hg2Cl2 + 2CH3OH + 2HC1

The product of the addition of mercury amide-chloride to g ly-cerol has been obtained by precipitating a solution of HgCl2 in g lycerol with ammonia and by the action of mercury amide-chloride on g lycerol [2].

O - H g d e r i v a t i v e s o f p h e n o l s ( m e r c u r y p h e n o x i d e s ) . M e r c u r y does not form stable monophenoxides (ArO)2Hg or ArOHgX (where A r is the phenyl group or a residue of a benzene homolog). The unstable mercury phenoxides which form initially when mercur ic salts interact with alkali metal phenoxides rearrange fairly rapidly into r ing-mercurated phenols dissolving in alkalis without separa-tion of m e r c u r i c oxide. Manchot [3] has described the formation of products of addition of m e r c u r i c salts at the oxygen following the mercuration of phenols and phenolic ethers. Only the mercury phenoxides of phenols containing in the ring severa l halogen atoms, a nitro group, etc. , have been isolated, e .g. mercury tr ibromo-phenoxides (C6H2OBr3)2Hg, prepared [4, 5] from 2,4,6-tribromo-phenol and mercur ic acetate in dilute alcohol; the compound is obtained in the form of ye l low-red plates which dissolve fair ly readily in alcohol. Dark yellow mercurous 2,4,6-tribromo- and

COMPOUNDS WITH -HgXC- GROUPS 465

tri-iodophenoxide precipitate out when a slightly acidified mercu-rous nitrate solution is added to an alcoholic solution of the c o r r e -sponding trihalogenophenol [6].

Mercury pentachlorophenoxide [7] (C6Cl50)2Hg + 2H20 l o s e s w a t e r at I lO 0 C and transforms into (C6Cl5O)2Hg. The latter compound is formed as an amorphous yellow powder, insoluble in the usual solvents, as a result of the action of a str ict ly neutral solution of sodium or potassium pentachlorophenoxide on an aqueous solution of a m e r c u r i c salt, with heating.

Preparation of mercury pentachlorophenoxide [7]. A mole of pentachlorophenol is d i s -solved in aqueous KOH or NaOH containing slightly m o r e than 1 mole of the alkali metal hydroxide and strongly diluted nitr ic acid added dropwise to the result ing solution, with s t i r r ing , until a s l ight precipitate of insoluble pentachlorophenol begins to appear. T h e precipitate is f i l tered off and the c l e a r solution of pentachlorophenoxide not containing an e x c e s s of alkali treated with 1 mole of neutral m e r c u r i c salt . The product i s f i l tered off. M e r c u r y pentachlorophenoxide is readi ly decomposed even by weak acids.

Mercuric picrate [C6H2(N02)30]2Hg.2H20 [5, 8, 9] is obtained by heating picr ic acid in water, at a temperature not exceeding 80°C, with freshly precipitated m e r c u r i c oxide. It has been reported [9] that under all conditions this compound is obtained only as the explosive double salt [C6H2(NO2)3Oj2Hg1Hg(OH)2lGH2O. On being boiled in water, or in the presence of dil. HCl, it decomposes with the formation of r ing-mercurated picric acid [5]. The latter com-pound has been obtained by Liebig [10], who regarded it as m e r c u -rous picrate [5].

According to Patent l i terature [11], the action of acetic acid on (£-C10HT)2Hg gives ^-C10H7OHgOCOCH3.

4-Nitro- l -naphthol-O-mercury acetate has been obtained by mixing aqueous solutions of mercur ic acetate and 4 - n i t r o - a -naphthol [12]. When this compound is dissolved in acetic acid the mercury migrates into the ring (see Chapter 5).

Whereas phenol and naphthols are mercurated into the ring under the influence of mercur ic chloride and sodium bicarbonate in the presence of g lycerol (see under "Mercuration of aromatic hydroxy compounds", Chapter 5), pyrocatechol, resorcinol , hydroquinone, orcinol , guaiacol and phloroglucinol form compounds [13] containing the OHgCl group, e.g. the green O-C6H4(OHgCl)2, decomposing around 150° C, which precipitates out when HgCl2, NaHCO3 and glycerol r e -act with an aqueous solution of pyrocatechol. Thecontent of the O-Hg product increases with increasing pH of the medium [14].

A red compound containing an O-Hg bond precipitates out when m e r c u r i c chloride solution is added to the sodium salt of 4-phenyl-azo-l-naphthol [15],

O - H g derivatives of alkylnitroamines. Compounds (RNNO2)2Hg, which appear to contain Hg-O linkages, are prepared by treating aqueous solutions of alkylnitroamines with freshly precipitated

Refcreiiccs sec page 494


mercur ic oxide. The m e r c u r y derivative of methylnitroamine con-s i s t s of c o l o r l e s s needles sparingly soluble in cold water or alcohol [16] and the mercury derivative of ethylnitroamine of leaf lets or plates (explosive) [17].

O - H g c o m p o u n d s o f o x y g e n c o n t a i n i n g c y a n o g e n d e r i v a t i v e s . Analys is of the Raman spectrum of the mercury derivative of cyanic acid, obtained by the action of a mercur ic salt on potassium cyanate as a double salt with a potassium salt, led Birckenbach and Kolb [18, 19] to regard it as an Hg-O compound, but the structures of both m e r c u r y cyanates themselves and of their double salts are st i l l insufficiently c l e a r [20].

Preparation of the double salt of mercuric cyanate and potassium chloride [ 18]. Pow-dered mercuric chloride (28 g) is gradually stirred, at 15-20°C, into a solution of 20 g of potassium cyanate in 150 ml of water (neutralized to methyl red with dil. HCl). Im-mediate precipitation takes place and the reaction mixture sets to a pasty mass. The solid material is filtered off, washed with several portions of 50% ethanol, then with pure ethanol and finally with ether. Yield: 12 g (80%).

Recrystallization from 100 ml of water (40°C) and removal of the slight turbidity gives 15 g of the double salt (41,5%) in the form of colorless, finely crystalline powder.

Mercuric fulminate (CNO)2Hg is obtained by the action of m e r -curic nitrate in nitric acid on ethanol [21-25], according to the following scheme [30]:

CH3CH2OH + HNO3 CH3CHO + HNO2

+ H2O -> ONCH2CHO HON = CH — CHO

<°> HON = CHCOOH H N ° 3 . HON = C (NO2 )COOH HON = CHNO2

- » H - O - N = C + HNO2

2HONC + Hg (NO3)2 - » Hg (ONC)2 + 2HN03

The industrial manufacture of mercur ic fulminate is based on this reaction.

The ethanol may be replaced by acetaldehyde, dimethyl acetal , or malonic acid [26]. Mercuric fulminate can also be made by adding the sodium salt of acinitromethane, CH2NO2Na, to aqueous HgCl2 at O0C [27-29] and subsequent boiling with dil. HCl:

2CH2N02Na + HgCl 2 - * (CH2NOO)2 Hg - (ONC)2 Hg + 2Ha0 + 2NaCl

The yellow basic salt

Hg

2

is also formed. This very explosive compound is the only product when m e r c u r i c chloride solution is added to a solution of the sodium salt of nitromethane.


Another way in which mercur ic fulminate can be prepared is by boiling methylnitrolic acid HON=CHNO2 in dil. HNO3 in the presence of mercur ic salts [30]. The very low e lectr ica l conduc-tivity of mercur ic fulminate [16] shows that it may contain not Hg-O but Hg-C bonds [31].

Preparation of mercuric fulminate [24, 25]. A solution of 50 g of m e r c u r y in 600 g of HNO3 (sp. gr . 1.4) and 550 g of 98.5% ethanol is gradually s t i r red into the st i l l -hot (about 70°C) solution. When the evolution of the white f u m e s c o m e s to an end, 1 l i ter of water is added to the contents of the react ion v e s s e l . T h e result ing fulminate is stored under water.

Mercur ic fulminate is a white or gray crystal l ine compound. It contains half a molecule of water when crysta l l ized from that solvent, but may be obtained in an anhydrous state by c r y s t a l l i z a -tion from alcohol or by precipitation from aqueous ammonia with nitric acid [32, 33]. It is insoluble in most organic solvents, spar-ingly soluble in water and benzene, and dissolves more readily in warm acetone, alcohol, ammonia, pyridine, or a solution of potassium cyanide. It can be purified by dissolution in aqueous KCN, pyridine, or aqueous ammonia, and precipitation with dilute acid. With hydrochloric acid, mercuric fulminate gives chloro-formaldoxime in the cold [28, 34], and a mixture of hydroxylamine and formic acid on heating [35]. Under the action of chlorine or bromine, mercur ic fulminate gives r ise to a dihalogenofuroxane. An e x c e s s of chlorine results in HgCl2, chlorocyanogen and chloro-picrin [36] (cf. [37]). Aqueous ammonia gives urea and guanidine [38]. For the action of ammonia and amines, see also [38-40], Boiling of mercuric fulminate in water with copper or zinc results in the formation of the fulminates of these metals and the separa-tion of metall ic mercury [35]. Metal fulminates are also formed when the amalgams of sodium [35], potassium, alkaline earths, cadmium, thallium, or manganese react with mercur ic fulminate in methanol under an atmosphere of hydrogen [41-44].

Hydrogen sulfide decomposes mercuric fulminate (suspension in water) with the formation of NH4CNS, HgS and CO2 [36]; a c c o r -ding to [45], thioformhydroxamic acid also appears among the products (see also [38, 46]).

The action of ethyl iodide results in ethyl isocyanate and ethyl cyanurate [28], the action of acetyl chloride in acetyl isocyanate, CH3CON=CO, mercuric chloride, a little HCN, acetylurea and diacety lurea [47] and the action of benzoyl chloride in dibenzoy lurea [48]. A warm concentrated solution of thiourea gives with mercuric fulminate mercur ic sulfide, mercur ic thiocyanate and urea [49]. No interaction has been observed when mercur ic fulminate is mixed with diethylmercury, but the action of hydrogen chloride on such a mixture gave ethylmercury chloride and a complex having the composition 5HgCl2.2NH2OH.HC1.2NH4C1.2(CH3)2CO [50],

References see page 4 <>4


It has been shown that, depending on the order in which the r e -agents are added, the products of the interaction between mercur ic fulminate and aromatic hydrocarbons in the presence of AlCl 3 , A1C13+6H20, and Al(OH)3 are nitr i les [52] or aromatic aldoximes [51, 53-55]. The latter were in fact f i rs t prepared in this way.

The reaction between the double salt of m e r c u r i c fulminate with KCN and alkylarylpyrazolones leads to the formation of 4-cyanoalkylary!pyrazolones [56].

The l i terature dealing with mercur ic fulminate, one of the most important detonators, is very extensive. For industrial manu-facture of m e r c u r i c fulminate, see for example [57-61],

According to Hantzsch [62], the mercury derivat ives of cyanuric acid, obtained by the action of mercur ic chloride or acetate on a solution of an alkali metal cyanurate at O0C, are also O-Hg compounds.

O - H g de r i va t i ve s of s o m e heterocyc les . F o r t h e m e r c u r y d e -r ivat ives of insatin, which can be regarded both as an Hg-O and an Hg-N compound, see the section on Hg-N compounds.

According to Curtius [63], isat in-^-hydrazone or its desmo-tropic form heated with mercur ic oxide in benzene gives the m e r c u r i c salt of 3-diazohydroxyindole

Mercury derivatives of antipyrine containing Hg-O bonds have been described [64].

P r e p a r a t i o n f r o m m e r c a p t a n s a n d s imple su l f ides, a n d cer ta in reac t i on s of mercury a l k y l m e r c a p t i d e s . W h e r e a s m e r c u r y a l k o x i d e s and phenoxides are known only for a number of c a s e s , the forma-tion of stable (RS)2Hg proceeds readily and is character ist ic of the mercaptans. In fact, this was the bas is of the lat ter ' s name corpus mercurium captans [65]. Mercury mercaptides are obtained by the action of RSH on HgO or Hg(CN)2, general ly in aqueous or alcoholic solution. The reaction is accompanied by a considerable evolution of heat.

b) Compounds with an S-Hg Bond

M e r c u r y A l k y l m e r c a p t i d e s

Preparation of mercury ethylmercaptide [66]. T h e product precipitates out in the f o r m of f ine, tangled, f l ex ib le needles when an aqueous solution of m e r c u r i c cyanide is


shaken with ethyl mercaptan. Recrystallization from alcohol gives white leaflets; m.p. 76-77°C [67-69] (78°C [23]).

The same method has been used to make [70] the methylmercaptide (CH8S)2Hg; m.p. 175°C (with decompositon) [70, 71]; b.p. 215-220°C/0.1 mm [72],

Bradley et al. [72] showed mercury methylmercaptide to be polymeric .

Mercury propylmercaptide (m.p. 71°C) has been made from propyl mercaptan and HgO [73] or Hg(CN)2 [74]. The melting-points of severa l mercury alkylmercaptides have been reported [74]: (iso-C3H,S)2Hg 62-63°C (see [75]), (n-C4HgS)2Hg 85-86°C, (iso-C4H9S)2Hg 94-95°C, (C5H11S)2Hg 74-75°C, (Iso-C5H11S)2Hg 100°C, (C7H15S)2Hg 76-77°C,

The formation of the benzylmercaptide is strongly exothermic, even if the mercaptan and the mercur ic oxide are reacted in strongly diluted alcoholic solution [76, 77].

Preparation of mercury benzylmercaptide [76]. Finely ground red mercuric oxide is added to an alcoholic solution of benzyl mercaptan and the resulting white mass filtered off and extracted with several portions of hot alcohol. Recrystallization from ethanol gives fine threadlike needles; m.p. 121-125°C [76a],

RSHgX are prepared [82, 83] by the interaction of RSH with HgX2

(X = Hal, NO3 [77-82] and other groups) under mild conditions, e.g. in alcohol, by the action'of HX (X = Cl [70], NO3 [82]) on (RS)2Hg, or by heating (RS)2Hg with RX (X = B r , I). In the latter case , when X = I, the product may be RSHgI [84], R3SI1HgI2 and (R3SI)2.HgI2

[83, 85], or R2S. Hgl2[85], depending on the conditions. Ethyl bromide r e a c t s l e s s readily than ethyl iodide [83]. RSHgX can also be obtained by a double decomposition:

RSHgX ' + K X - - RSHgX + KX '

(see, for example, [86]). C2H5SHgNO3 has been made by the action of gaseous nitrogen

oxides on (C2H5S)2Hg [83]. It is possible that the iodides are covalent - RSHgI - and the nitrates ionic - (RSHg) +NO^ [85]. In contrast to (AlkS)2Hg, the AlkSHgX form complexes with ammonia [83], Halogens react with (RS)2Hg under mild conditions, giving RSHgHal or RSHal [85a-85c].

C2H5SHgOCOCH3 has been prepared by the action of mercuric acetate on ethyl thioacetate, in warm alcohol, or in acetic an-hydride at room temperature [78]:

CH3C - S - C2H5 + Hg (O2CCH3)2 C2H5SHgO2CCH3

Il O

According to [79], the molecular weight of salts RSHgX (X = halide, acetate, perchlorate, etc.) correspond to twice the empir-ical formula.



The product of the reaction of RSHgX with R'X has the composition R2S2.HgX2.R'X [89].

Mercury benzylmercaptide-chloride, C6H5CH2SHgCl, has been made by the action of HgCl2On sodium benzyl thiosulfate [90]; the action of Hg(CN)2 in cold aqueous solution, followed by heating for an hour or a water bath, g ives mercury benzylmercaptide (C6H5

CH2SJ2 Hg [76a]. Mercury ethylmercaptide has been prepared by an analogous method [76a].

The m e r c u r y derivatives of cycl ic triethylene polysulfides are described in [91],

2-Alkoxyethyl mercaptans ROCH2CH2SH react with alcoholic HgCl2 to give white precipitates of high-melting mercaptomercury chlorides ROCH2CH2SHgCl [88, 92-94] (R = C2H5, C4H9 [92, 93]), sparingly soluble in organic solvents, and in this respect they di f fer from the isomeric 1-alkoxyethanethiols CHsCH(OR)SH.

Preparation of (C jH5SHgO2CCH3)2 [79]. M e r c u r y ethylmercaptide (16.14 g) s t i r r e d with 15.94 g of m e r c u r i c acetate in 60 ml of warm water g ives a c l e a r solution, f r o m which slow evaporation produces l a r g e c r y s t a l s of the pure salt , readily soluble in water , alcohol and CCI4.

Fair ly detailed attention has been focused on mercury b i s -trif luoromethylmercaptide, (CF3S)2Hg, f i rs t obtained by Brandt, Emeleus and Haszeldine [95, 96] by ultra-violet irradiation of a mixture of mercury and trif luoromethyl disulfide, and also by the reaction of CS2 with HgF2 at 250°C [97, 98],

Preparation of mercury trifluoromethylmercaptide from trifluoromethyl disulfide and mercury [96]. T r i f l u o r o m e t h y l disulf ide (5.0 g) and 80 g of mercury in a quartz tube are exposed to the action of u l t ra-v io le t light for 4 days, with vigorous shaking. T h e e x c e s s of disulf ide is then disti l led out and the solid res idue is extracted with ether. Evaporation of the ethereal extracts , dried over P 2 O 5 at room temperature, in a dry atmosphere, g ives a 90% yield of the required product; m.p. 37-38°C.

Preparation of mercury trifluoromethylmercaptide from carbon disulfide and mercuric fluoride [98]. M e r c u r i c f luoride (715 g, 3 moles) and 453 g (about 6 m o l e s ) of carbon disulf ide are heated f o r 4 hours at 250°C in a 1 - l i t e r autoclave lined with s ta in less s tee l . Af ter cooling to room temperature, m e r c u r i c sulf ide is f i l tered off and carbon disulfide evaporated away f r o m the f i l t rate . Disti l lation of the low-melt ing res idue at 80-81°C/ 21 mm gives 250-350 g of the required product; y ie ld (average): 72%.

The reaction of mercury trif luoromethylmercaptide with HgCl2

gives mercury tri f luoromethylmercaptide-chloride [99]; the chlo-ride ion may be exchanged for a nitrate or acetate by exchanges with the corresponding s i lver salts (in water, at room tempera-ture) [99],

Preparation of mercury trifluoromercaptide-chloride [99] . M e r c u r y t r i f luoromethy l -mercapt ide (0.301 g) in 10 m l of ether and 0.204 g of H g C l 2 in 10 ml of the s a m e solvent are shaken together at room temperature . The product obtained by evaporation of the ether is sublimed in vacuum at 40-50°C. Yie ld: 0,45 g.


Mercury trif luoromethylmercaptide does not react with mercuric bromide under these conditions [99].

Spectroscopic ( infra-red and Raman) studies have shown that equilibria

(CF3S)2 Hg + HgX 2 2CF3SHgX

a r e set up in the reactions of mercury trif luoromethylmercaptide with mercur ic salts in aqueous or aqueous-alcoholic solutions (X = Cl , B r , I [101], OCOCH3, OCOCF 3 , NO3 [100]).

Reversible complex-formation takes place with the s i lver salts of these oxygen-containing acids [100]:

.AgX + (CF3S)2 Hg - AgX (CF3S)2 Hg

Conductimetric titrations show that, with potassium iodide and with tetramethylammonium chloride or iodide, mercury tr i f luoro-methylmercaptide f o r m s complexes in which it enters into the composition of the anion [102], for example:

(CH3)4 N + [ H g (SCF3)2Cl]-

Mercury trif luoromethylmercaptide reacts with phosphorus t r i -chloride already at room temperature (sealed tube) [99] (see [98]). With equimolar proportions of the reagents, the reaction is as follows:

(CF3S)2 Hg + PCl3 - CF3SPCl2 +• CF3SHgCl

If the trif luoromethylmercaptide is in a large e x c e s s , the products are (CF3S)2PCl and (CF3S)3P. Heating is necessary if the latter compound is to be formed.

The reaction with arsenic trichloride proceeds in the same way. In these reactions mercury trif luoromethylmercaptide resembles Alk2Hg and Ar2Hg, but di f fers from bis-(tr i f luoromethyl)mercury which is inert to PCl 3 and A s C l 3 even at 100°C. When heated with copper, mercury trif luoromethylmercaptide forms (CF3S)x Cu [98].

Reaction of mercury trifluoromethylmercaptide with copper [98]. Heating 6 g of fine copper powder with 9 g of mercury trifluoromethylmercaptide at 80- 100°C results in a strongly exothermic reaction leading to the appearance of a bright orange color. The heating is continued for 30 minutes at 150°C. After cooling, the solid residue is extracted with 500 ml of ether. Evaporation of the extract gives pale-green Cu(SCF)2; which still contains some ether.

Other metals , such as Pb or T l , form with mercury methyl-mercaptide fluorides M F n [98]. A r y l and alkyl halides, sulphenyl halides and acyl halides give r i s e to tr i f luoromethylaryl (alkyl) sulf ides, thioacylates and disulfides [98], for example

CH2 = CHCH2SCF3, C2H5CSCF3, CCl3SSCF3

Il O



The interaction between mercury trif luoromethylmercaptide and hydrogen chloride in a sealed tube at room temperature over a period of 48 hours resulted in a quantitative yield of trif luoromethyl mercaptan [96].

S-Hg compounds are also readily formed with thiol groups in other c l a s s e s of organic compounds. F o r e x a m p l e j S - H g d e r i v a t i v e s of the type of (RS)2Hg of thioglycolic, thiolactic and thiobutyric acid anilides precipitate instantly when alcoholic solutions OfHgCl2

and of an excess of the appropriate mercapto acid anilide are poured together [103].

According to [324], thioamides react with m e r c u r i c nitrite in the tautomeric form of iminomercaptans, giving r i s e to RC(NH)SHgNO2. The latter products are unstable and decompose immediately to an aldehyde, an acid, ammonia and an inorganic salt.

Thiourea may also react with mercuric nitrite with the initial formation of H2NC(SHgNO2)=NH, which later t ransforms into more complex products.

The action of caustic soda and mercur ic chloride on an aqueous solution of HO2CCH2CH2SC(NH)NH2 g ives sodium |6-mercurimethyl-mercaptopropionate [105].

Mercuric thiocyanate, Hg(SCN)2, is obtained in the usual manner: from m e r c u r i c oxide and thiocyanic acid [106-108] in aqueous solu-tion, or from alkali metal thiocyanates and m e r c u r i c nitrate [106, 107, lt>9], acetate [110] (cf. [ I l l ] ) (colloid [112]), or chloride [113], The formation of mercur ic thiocyanate from the fulminate and thiocyanic acid has already been mentioned. Mercur ic thiocyanate consists of small needles or plates, sparingly soluble in cold water , more so in boiling water [106]; the compound dissolves more readily in alcohol, and is somewhat soluble in ether. It decomposes at a temperature of around 165°C, with strong swelling ("Pharaoh's serpents"); with other thiocyanates, halides and cyanides, it readily forms complexes M[Hg(SCN)3] and M2[Hg(SCN)4], in which the thiocyanato group can be exchanged for CN and a halogen [111] and H2O [111a] (see [114]). Thetrithiocyanates are as a rule difficult to dissolve in water, whereas the tetrathiocyanates dissolve without difficulty [115].

The e f fects of the nature of the solvent on the formation of com-plexes by mercur ic thiocyanate have been studied [115a].

Studies of the infra-red spectra of m e r c u r i c thiocyanate and complexes MHg(SCN)j and MHg(SCN)6-C6H6 (M = Co, Ni, Cd) led the authors of [115b] to postulate in the latter compounds the p r e s -ence of a kind of n - a bond.

Mercuric thiocyanate also exhibits a very pronounced tendency toward the formation of double sal ts .

Monothiocyanates NCSHgX (where X = Cl [115, 116] (see [117]), B r [115], I [118], ClO4 [119], CH3CO2 [120, 121], HS [118]) are obtained by treating Hg(SCN)2 with an excess of the corresponding m e r c u r i c sal ts in hot water.


Mercur ic thiocyanate reacts even more easi ly with R2Hg in dioxan than m e r c u r i c iodide or cyanide [122].

Mercurous thiocyanate is formed from very dilute aqueous solutions [107, 123, 124] of mercurous nitrate and alkali metal thiocyanates, and by the action of thiocyanogen on metall ic m e r c u r y [125]. The resulting white precipitate decomposes on heating, but not so character ist ical ly as mercur ic thiocyanate. It dissolves in solutions of alkali metal thiocyanates to give M2 [Hg(SCN)4] and metallic m e r c u r y [107].

Monothioglycols [88, 126, 326], dithioglycols [89], monothio-g lycerol [326] and dithioglycerol [326] also give r i s e to the c o r r e -sponding S-Hg compounds under conditions analogous to those used in the preparation of m e r c u r y mercaptides from the mercaptans. For example, compounds O2NHgSC2H4SHgNO2 and S2(C2H4SHgNO2)2

have been obtained [89] f rom mercur ic nitrite and ethylene dithio-glycol .

P r e p a r a t i o n of S - H g d e r i v a t i v e s b y the a c t i o n of t h i o a c e t a l s , v inyl su l f ides a n d s i m i l a r c o m p o u n d s with mercur ic s a l t s . W h e r e a s t h e normal dialkyl sulfides form complexes with m e r c u r i c chloride, the sulf ides derived from aldehydes - monothioacetals, thioacetals and certain thioketones, and also vinyl sulf ides, a r e cleaved by HgCl2 or HgO with the formation of the corresponding carbonyl compound (in water) or its acetal (in alcohol) and with the evolution of HCl and mercury mercaptide-chloride. With thioacetals, the reaction can be carr ied out in either one or two stages:

SR /

RCH(SR)2 + HgCl2 4- R'OH RCH 4 RSHgCl + HCl \

OR'

SR /

RCH + HgCl2 + R'OH RCH (0R')2 + RSHgCl + HCl

OR' Treatment of thioacetals with H g O i n w a t e r r e s u l t s in the splitting

off of one SR group. Both SR groups are cleaved off by HgCl2 in the presence of cadmium carbonate.

Acrole in [133] and crotonaldehyde [134] are formed when the corresponding diethylthioacetals(mercaptals) are boiled with an e x c e s s of aqueous m e r c u r i c chloride.

This reaction has been applied to the regeneration of L-cyste ine f rom S-benzylthiomethyl-L-cysteine by the action of HgCl2 in warm IN HCl [135]. The reaction is accompanied by precipitation of thiobenzylmercury.

The ease of the c leavage of the thiol groups from aldehyde



thioacetals by HgCl2 makes it possible to protect the aldehyde group by mercaptalization, c a r r y out several reactions, e.g. in the case of aldehydes containing other functional groups, and then regenerate the aldehyde with mercur ic chloride. For example:

HgCl2

RCOCH ( S R ' ) J — RCH ( O H ) C H (SR')a -777: RCH ( O H ) C H O + R 'SHgC l H2O

Synthesis of mandelaldehyde by cleavage of its diethyl thioacetal with mercuric chloride and cadmium carbonate [136]. A solution ot 10 g of the diethyl thioacetal of mandel-aldehyde in 120 ml of acetone and 15 ml of water is treated with 50 g of cadmium c a r -bonate and 45 g of HgCl 2 in 50 m l of acetone and 10 ml of water . Af ter being s t i r r e d f o r 2 hours at room temperature and f i l tration, the f i l t ra te i s worked up with 20 g of a 1:1 mixture of m e r c u r i c chloride and cadmium carbonate and ref luxed for 30 minutes. T h e sa l ts a r e f i l tered off and washed with acetone. T h e f i l t r a t e is evaporated under vacuum, the res idue extracted with chloroform and the solution shaken up with a solution of KI and washed with water til l it is f r e e f r o m halide. Drying over sodium sulfate and vacuum evaporation of the ch loroform gives an oil which begins to c r y s t a l l i z e on stand-ing f o r a cer ta in time. After working up with 2-3 portions of ether and petroleum ether, the c r y s t a l s a r e r e c r y s t a l l i z e d f r o m a mixture of absolute tetrahydrofuran and petroleum ether. Yie ld: 2.5 g (44.5%); m.p. 134-137°C (with pre l iminary decomposition).

Stirring with mercur ic chloride for severa l hours at room temperature in the presence of substances neutralizing the s imul-taneously evolved hydrogen chloride (sodium o r cadmium carbonate) allows regeneration of carbonyl compounds from their cycl ic thio-acetals obtained by the action of 1,2-ethanedithiol [137] or 1 ,3-propanedithiol [138-140] on the carbonyl compound.

Thus, the action of m e r c u r i c chloride and sodium bicarbonate on sodium 2-phenyl-l ,3-dithian-5-sulfonate is as follows [140]:

S - C H 2 S - C H 2

CeH 5 — CH x C H S O 3 N a H g C ' 2 , H g ^ X C H S 0 3 N a + C 6H 6CHO \ / N a H C O , \ /

S - C H 2 S - C H 2

Preparation of sodium l,3-mercuridimercaptopropane-2-sulfonate [ l40] . HgCl 2 (35 g) and 12 g of NaHCOg are added in portions, with s t i r r i n g and heating at 60-65°C, to a solution of 40 g of crude sodium 2-phenyl- l ,3 -d i th ian-5-sul fonate in400 m l of water . T h e solution is then heated for a further hour and its content of sodium m e r c u r i d i m e r c a p t o -propanesulfonate (44.8 g, 81%) determined iodimetr ica l ly . T h e s a l t i s precipitated f r o m the solution with alcohol (500 ml) in the f o r m of a 72% pure technical product.

Whereas vinyl ethers add mercur ic salts a c r o s s the double bond (see Chapter 6), the action of mercur ic chloride on vinyl alkyl sulfides in alcoholic or aqueous solutions is directed at the second reaction center of the molecule, the sulfur atom, leading to the formation of RSHgCl [141]:

CH 2 = CHSC2H5 + HgCl2 + 2C2H5OH - » C2H5SHgCl + HCl + CH 3CH (OC2Hs )2

CH 2 = CHSC2H5 +- HgCl 2 + H 2O - C2H5SHgCl + HCl + CH 3 CHO


The reaction proceeds quantitatively in ethanol and can be used for a t i tr imetr ic determination of vinyl sulfides [142], In an ethereal solution, the reaction of ethyl vinyl sulfide with m e r c u r i c chloride g ives an unstable complex having the approximate composition SCH2=CHSC2H5.4HgCl2, decomposing rapidly in the presence of alcohol and water into acetaldehyde, hydrogen chloride and C2H5

SHgCl [141].

The reaction of ethyl vinyl sulfide with alcoholic HgCl 2 . Preparation of mercury ethylmercaptide-chloride [ l 4 l ] . T h e sulf ide (0.13 g) is treated with 4.5 ml of alcoholic 20% HgCl 2 and s e t aside overnight. The result ing prec ipi tate is f i l tered off , washed with alcohol and ether, and dried under vacuum to constant weight. Y ie ld: 0.37 g (96,2%). T h e product is r e c r y s t a l l i z e d f r o m boiling xylene, washed with alcohol and ether and dried under vacuum. It does not melt on heating to 200°C and s lowly decomposes at 300-350°C.

The same type of reaction is observed between /3-alkoxyethyl vinyl sulfides and m e r c u r i c chloride in ethanol:

ROCH 2CH 2SCH = CH 2 + HgCl 2 + 2C2H5OH - » ROCH 2CH 2SHgCl

+ HCl + CH 3CH(OC 2H 5 ) 2

with quantitative evolution of the ^3-alkoxyethylthiomercury chloride and HCl [142]; see [143]. Acetaldehyde is formed when the above reaction is carr ied out in an aqueous solution [142].

A s has been shown by Pr i lezhaeva et al. [92, 144], of the three types of di(alkoxyethyl) sulfides:

ROCH 2 CH 2 ROCH 2CH 2 CH 3 CHOR

\ \ I S S S

R O C H 2 C H 2 ^ R O - C i I C H 3 CH 3 CHOR

P , P ' a, P a, a'

the /3,|3-sulfides react with m e r c u r i c chloride to give the complex sal ts typical of the usual sulf ides. The HgCI2-complexes of the a , p -and a ,a-der ivat ives decompose immediately. The o,/3-derivatives form /3-alkoxyethylthiomercury chlorides and acetals and eliminate 1 molecule of hydrogen chloride:

OR OR / /

CH 3 CH + HgCl 2 - f R ' O H CH 3CH + ROCH 2CH 2SHgCI + HCl \ \

SCH 2CH 2OR O R '

The complex salts of the a ,a ' - isomers decompose into yellow residues and l iberate 2 molecules of hydrogen chloride.

The action of mercuric chloride on a,^S-di(butoxyethyl) sulfide. Preparation of /3-bu-toxyethylthiomercury chloride [ 144].

^ O C 4 H 9 OCjH 9

CH 3 CH + HgCl2 + C2H5OH -» CH 3 CH + C4H9OCH2CH2SHgCl + HCl n xSCH2CH2OC4H9 n s O C 2 H 5



HgCl (3.5 g) in 15 ml of ethanol i s added to 2.5 g of a ,,S-di(butoxyethyl) sulf ide. A white curdy precipitate soon made an appearance. T h e mixture is set aside overnight. T h e solid m a t e r i a l i s then f i l tered off and washed with cold solvent. Evaporation of the f i l t ra te g ives an additional, v e r y s m a l l , c r o p of c r y s t a l s . T h e total weight of the p r e -cipitate i s 3.5 g (87.7% on the start ing sulfide). R e c r y s t a l l i z a t i o n f r o m a l a r g e volume of boiling ethanol r e s u l t s in white gl istening plates (m.p. 137 .5-138°C) pract ica l ly insoluble in cold alcohol, ether and acetone.

/3-Ethoxyethylthiomercury chlor ide (m.p. 1 5 5 . 5 - 1 5 6 ° C , f r o m alcohol), has been made by the s a m e method.

On reaction with alcoholic mercur ic chloride, bis-/3-alkoxy-ethy lmercapto- l , l -e thanes form the corresponding mercury m e r -captide-chlorides and evolve hydrogen chloride [144]:

CH 3 CH(SCH a CH 2 OR) 2 + 2HgCl 2

+ 2 R ' 0 H - » CH 3 CH(OR ' ) 2

+ 2ROCH 2 CH 2 SHgC l + 2 H C 1

Acetaldehyde is formed on heating with an e x c e s s of m e r c u r i c chloride in water. The mercaptide residues are isolated in two stages.

The action of mercuric chloride on bis-(/3-ethoxyethylmercapto)-l,l-ethane. Prepara-tion of /3-ethoxyethylthiomercury chloride [ 144].

CH 3 CH (SCH2CH2OC2H5)2 + 2HgCl2 + 2C2H5OH CH 3 CH (OC2H5)2

+ 2C2H5OCH2CH2SHgCl + 2HC1

A solution of 0.3 g of m e r c u r i c chlor ide in ethanol is added to 0.2 g of bis-(/3-ethoxy-e t h y l m e r c a p t o ) - l , l - e t h a n e , result ing in the appearance of white 3-ethoxyethyl th iomer-cury chloride. A f t e r being dried in a vacuum d e s i c c a t o r , the weight of the precipitate is 0.60 g, m.p. 155 .5-156°C (following repeated r e c r y s t a l l i z a t i o n from boiling ethanol).

The same procedure yielded 0.5 g (theoretical 0.49 g) of /3-butoxyethylthiomercury chloride, m.p. 1 3 7 . 5 - 1 3 8 ° C , f r o m 0.2 g o f b i s - ( / 3 - b u t o x y e t h y l m e r c a p t o ) - l , l - e t h a n e .

The reaction with mercur ic chloride has been suggested by Holmberg [145-149] for quantitative determinations of the thio-acetals and thioketols of thioacetic, thioglycolic, thiolactic and thiohydracrylic acids (titration of the evolved HCl with alkali or iodimetric determination of HgCl2). In alcoholic media, the r e -action has been developed by Pri lezhaeva et al. for quantitative determinations of monothioacetals [92, 144, 189], thioacetals [141, 142] and vinyl sulfides [94, 142, 144, 150-157], and by various authors for the determination of other sulf ides and derivatives of aldehydes and ketones (for example [158]). The cleavage by HgCl2 is not quantitative if a benzoate group is present in a position /3 with respect to the SR group,

The products of the addition of dialkyl phosphorothiolothionates to vinyl [159a] and thiovinyl [159a, 160] ethers react with m e r c u r i c chloride in alcohol s imi lar ly to the thioacetals, liberating two equivalents of hydrogen chloride and decomposing according to


/ CH3CH + HgCl2 -f 2C2H5OH CH3CH (OC2H5)2 + 2HC1 + R'SHgCl

the reaction:

S R '

H

\ SPS(OR)2

+(RO)2P(S)SHgCl (1)

The mixed mercury salt of dialkyl phosphorothiolothionic and hydrochloric acids (1) disproportionated on recrystal l izat ion:

2 (C2H5O)2 PSSHgCl -* HgCl2 + [(C2H5O)2 PSS]2 Hg

Reaction of 0,0-dialkyl S-(a-alkylmercapto)ethyl phosphorothiolothionates with mer-curic chloride [ l60] , Preparation of ethylthiomercury chloride. H g C l 2 (2.2 g, 0.0081 mole) in I l ml of 96% ethanol i s added to 1 g (0.0036 mole) of 0 , 0 - d i e t h y l S - ( a - e t h y l -mercapto)ethyl phosphorothiolothionate. Af ter 3 hours the white precipitate i s f i l t e r e d off and washed with cold alcohol. T h e washings are combined with the f i l t r a t e and the res idue dried under vacuum; the weight of the res idue is 1.8 g. A f t e r 5 d a y s ' s torage , another 0.15 g of c r y s t a l s precipitate out of the f i l t rate . The hydrochloric acid content of the f i l -trate i s determined by titration of a portion with standard NaOH, and i s found to be 97.7% of the theoret ica l amount. T h e f i l t r a t e is evaporated to dryness under a p r e s s u r e of 10 mm, co l lect ing the dist i l la te in a solid CO 2 acetone trap. Determination of the diethyl acetal by the hydroxylamine method g ives a value of 92.6%.

T h e remaining portion is treated with 0.45 g of dinitrophenylhydrazine and 0.5 ml of conc. HCl and the mixture boiled f o r 30 minutes. Golden needles of acetaldehyde dinitro-phenylhydrazone precipitate out on cooling; af ter r e c r y s t a l l i z a t i o n , the melting-point i s 163-164°C. T h e weight of the dry res idue a f ter the above disti l lation i s 0.6 g and this i s reduced to 0.3 g af ter working up with water to r e m o v e unreacted H g C l 2 . T h e res idue darkens rapidly and i s not treated further . T h e total weight of isolated m e r c u r y sal ts i s 2.25 g (theoretical amount 2.6 g).

Salts precipitating o u t o f t h e s o l u t i o n ( 1 . 9 6 g) a r e extracted with s e v e r a l portions of boil-ing alcohol (total volume 75 ml). T h e alcohol- insoluble m a t e r i a l weighs 0.8 g. T h e nacreous leaf lets of ethylthiomercury chlor ide obtained by r e c r y s t a l l i z a t i o n f r o m boiling xylene decompose gradually above 250° C without melting. T h e a l c o h o l i c e x t r a c t g i v e s , on cooling, 0.7 g of f ine c r y s t a l s which a r e disproportionated completely by heating f o r an hour with boil ing benzene. T h e [(C2H60)2PSSJ2Hg c r y s t a l s precipitating out of the benzene solution decompose at 1 2 1 - 1 2 1 . 5 ° C .

The reaction with m e r c u r i c chloride (in the presence of cadmium carbonate, in alcohol, with st irr ing for 24 hours) and subsequent treatment with ammonia have been used to convert 2-(2-bromo-proprionamido)propionaldehyde diethylthioacetal into 2-hydroxy-3,6-dimethylpyrazine [161]:

Br N

( C 2 H 5 S ) 2 C H D H C H 3 ^ „ I I CdCO s H 3 C-^JJ-OH

H3CCH CO C 2 H 5 O H iM

N M H /

Cleavage of sugar thioacetals with m e r c u r i c chloride, f i rs t observed by Fischer [162], is utilized in the synthesis of mono-thioglucosides and alkylglucosides (reacting the sugar thioacetal



with one or two equivalents of m e r c u r i c chloride in absolute alco-hol) [163-170]:

/ SR

C

NSR C H O H

H g C l 2

SR

OC2H5

C H O H

O C H O H C ! H s O H " O C H O H I

C H O H I

- C H I

C H 2 O H

1 C H O H I

CH

CH 2 OH

HgCI 2

OC2H5

I OC2H5

C H O H

C 2 H s O H

I O C H O H

C H O H I

- C H I

CH 2 OH

and for the preparation of monoses in the aldehyde form (reacting the thioacetal with an e x c e s s of HgCl2 in aqueous alcohol) [163, 164, 171-173] .

Synthesis of monose glucosides from their benzyl thioacetals. Conversion of the benzyl thioacetals of 2-arabinose, Z-rhamnose, and (^galactose into ,3-methyl-Z-arabinoside, omethyl-Z-rhamnoside and omethyl-ii-galactoside [ l69] . A hot, concentrated solution of 1 mole of the thioacetal in methanol is rapidly treated with a hot methanolic solution of an e x c e s s of m e r c u r i c chlor ide (3 moles) and the mixture care fu l ly heated for 5 - 1 0 minutes on a water bath. T h e solution is f i l tered hot f r o m the precipitate of benzylthio-m e r c u r y chlor ide and alternately heated and f i l tered until no m o r e precipitate appears on further heating (usually about 1 hour). The e x c e s s of HgCl 2 is then removed with H2S and the acid solution neutral ized with s i l v e r carbonate (the acidity i s due to the l iberation of hydrogen chloride). T o r e m o v e the s m a l l amount of d issolved s i l v e r salt , the solution is once m o r e treated with H2S and the liquid (brown-black owing to the presence of colloidal s i l v e r sulf ide) is evaporated down to 20-30 ml , in the p r e s e n c e of a l itt le animal charcoal , in a porcelain basin. T h e f i l tered, c l e a r , neutral solution i s concentrated under vacuum to a consistency of a thick sirup. /3-Methyl-Z-arabinoside has a melting-point of 169-170°C (from alcohol), y ie ld: 90%; a-methyl-<2-galactoside, m.p. I l l 0 C (from alcohol), yield: 80%; a - m e t h y l - Z - r h a m n o s i d e , a s i r u p identified a f ter acetylation as the t r iacetate , m.p. 86-87°C.

Demercaptalization of dimethylisopropylidenexylose diethylthioacetal [ 173]. Asolution of 2 g of HgCl2 in 50 ml of absolute methanol is added over 30 minutes to a mixture of 9 g of the thioacetal, 18 g of HgO, 5 g of anhydrous Na2SO4 and 80 m l of absolute methanol. A f t e r being s t i r r e d f o r 6 hours at 45°C, the solution is f i l t e r e d off, the res idue extracted with w a r m alcohol and the combined f i l t ra tes treated with 5 m l of pyridine and set aside f o r 2 hours at 0°C. T h e pyr id ine-HgCl 2 complex i s then f i l t e r e d off and the f i l t ra te evap-orated under vacuum to the consis tency of a s irup. T h i s is subsequently f r e e d f r o m inor-ganic substances by extraction with benzene. T h e s i rup is dimethyl isopropyl idenexylose; V 1.4535,

Protection of the carbonyl group in sugars by conversion to a thioacetal is frequently used to enable various reactions of such compounds to be carr ied out; the sugars are subsequently r e -generated by reacting the thioacetals with m e r c u r i c chloride (see, for example, [174-199]).


Synthesis of 6-benzoyl-2,3,4,5-tetra-acetyl-dl-D-glucose [187]. 6 - B e n z o y l - 2 , 3 , 4 , 5 -t e t r a - a c e t y l - D - g l u c o s e di-n-propylthioacetal (2.9 g, 0.005 mole) in 40 ml of acetone and 3 ml of water i s mixed with 5 g of yel low m e r c u r i c oxide and 5 g o f m e r c u r i c chloride f o r 6 hours at 20°C and 30 minutes at 50°C. The mixture is then f i l tered, the precipitate washed with acetone and the f i l t ra te evaporated under vacuum in the presence of m e r c u r i c oxide. The r e s i d u e i s extracted with four 25-ml portions of chloroform and the extract washed with IN KI and with water , dried o v e r sodium sulfate and evaporated under vacuum. T h i s procedure g i v e s an amorphous powder which is dried and stored over paraff in at 35°C and 15 m m Hg. Yie ld: 1.58 g (70%) [a] ^ 8 + 18.8° ( c = 2.91 in chloroform).

M e r c u r y A r y l m e r c a p t i d e s ( T h i o p h e n o x i d e s )

These compounds are obtained by heating thiophenols and mercur ic oxide in aqueous or alcoholic solutions [76, 127] and sometimes even in the absence of solvent [128]. The reaction is best conducted in pyridine [129].

Preparation of mercury phenylmercaptide [ 129]. A solution of 5 g of thiophenol in 60 ml of pyridine i s shaken with 6 g of yellow m e r c u r i c oxide. T h e latter gradually decomposes with evolution of heat. T h e unreacted m e r c u r i c oxide i s f i l tered off, the res idue r insed with pyridine and the mercaptide precipitated out of the pyridine solu-tion by adding two volumes of water . T h e yield of the crude product is 9 .11 g. R e c r y s t a l -lization f r o m benzene gives c o l o r l e s s needles; m.p. 1 5 2 . 5 - 1 5 3 . 5 ° C .

Preparations of (O-CH3C6H4S)2Hg, (P-CH3C6H4S)2Hg [77], [1 ,3-(CH3)2C6H3SJ2Hg [130] and (G-C10H7S)2Hg [128, 131] have been described.

The mercaptide (p-BrCH2CH2C6H4S)2Hg has been made by the addition of an excess of m e r c u r i c acetate in dilute acetic acid to p -bromoethylthiophenol [131a].

Preparation of mercury a-naph thy lmercaptide [128]. a-Thionaphthol is added drop by drop to powdered m e r c u r i c oxide. T h e addition is accompanied by a v igorous, strongly exothermic react ion. T h e product is r e c r y s t a l l i z e d f r o m alcohol as a pale-yel low powder.

Certain RHgSCgH5 transform into (CgH5S)2Hg [327]. The action of nitrosyl chloride on mercury mercaptides g ives

r i s e to the corresponding disulfides [132]. A s y m m e t r i c a l disulfides have been made [85a] by the reaction:

( ( B - C 1 0 H 7 S ) 2 H g + 2 ( C H 3 ) 3 C S I ( C ' H ' ) z ? 2 P - C 1 0 H 7 S S C ( C H 3 ) 3 + H g I 2

M e r c a p t i d e s of S o m e H e t e r o c y c l i c C o m p o u n d s

Mercury thienyl and benzothienyl mercaptides have been obtained by the interaction between mercur ic acetate and the corresponding thiophenethiol in warm alcohol [103a].

2-Mercaptothiazoline g ives with mercur ic nitrate in alcoholic



solution [89] the mercaptide

^ ^ l i 2 1-* "

which forms with C2H5I a complex compound of the disulfide with HgI2 and C2H5I.

P r e p a r a t i o n of M e r c u r y M e r c a p t i d e s by the

A c t i o n of M e r c u r i c S a l t s on

S o m e O t h e r S u l f u r - c o n t a i n i n g C o m p o u n d s

In severa l c a s e s m e r c u r i c sal ts cleave the C - S bond in certain other sulfur-containing compounds (acetyl sulf ides, dithiocarboxylic acids, sulfoxides) under mild conditions, giving compounds contain-ing the S-Hg linkage.

Thus, for example, the compound NaCO2CH2 N(CH3)CSSHgSCH3CO2

Na precipitates out in the form of a green powder when a heated aqueous solution of the double salt with sodium and mercury ob-tained f rom the ester C2H5CO2N(CH3)CSSNH2(CH3)CH2CO^C2H5, is treated with alcohol. Evaporation of the above solution to dryness yields sodium mercury thioglycolate [104].

Phenyl thioacetate gives with mercuric acetate either CgH5SHg OCOCH3 o r (C6H5S)2Hg [200], depending on the ratio of the reagents.

Preparation of phenylthiomercury chloride [200], A solution of 1.1 g of mercuric acetate in alcohol, with additions of water and acetic acid, is treated, on boiling, with 0.5 g of C 6 H 5 SCOCH 3 . As soon as a turbidity begins to appear the heating is interrupted, the solution filtered and aqueous NaCl added to the filtrate; 0.8 g of the required product precipitates out and is recrystall ized from benzene.

(C6H5S)2Hg has been made f rom 1.5 g of m e r c u r i c acetate and 1 g of phenyl thioacetate in alcohol [200],

The action of m e r c u r i c chloride on ArSC(C6H5)3 in alcoholic solution at room temperature gives (ArS)2Hg; when there is an e x c e s s of m e r c u r i c chloride the products are ArSHgCl (Ar = C6H5, o -, m-, and JD-CH3C6H4 [200a]).

Coumaronylthiomercury chloride [201] is prepared by the r e -action:

. S H g C l

S-CH 2COOH

O Il + HgCl2 HC ,

C2H1OH

O O


P h o t o l y s i s a n d Pyro lys i s of M e r c u r y M e r c a p t i d e s

The gradual blackening of mercury mercaptides on storage was observed by Marker [77]. P h o t o l y s i s o f m e r c u r y m e r c a p t i d e s o c c u r s in various ways, depending on the nature of the organic radical . Thus, for example, whereas benzylmercaptide andcyclopentylmer-captide are photolysed to metall ic mercury , m e r c u r i c sulfide and sulfur-containing organic compounds, mercury phenylmercaptide and ethylmercaptide liberate only metallic mercury (but no m e r -curic sulfide) [202]. The stability of the mercaptides (RS)2Hgto photolysis increases in the order R = benzyl < n-propyl < isopro-pyl < cyclopentyl < t-butyl < phenyl [202].

P y r o l y s i s of mercury ethylmercaptide [68] and phenylmercaptide [127, 129] gives, respect ively , diethyl and diphenyl disulfide, as well as metall ic mercury [129], No mercur ic sulfide is formed in either case . Pyro lys is of trif luoromethylmercaptide (5 hours at 350°C, in an autoclave) and analysis of the infra-red spectra of the volatile products revealed the presence of (CF3)2S and (CF3)2S2

[98], The products of the pyrolys is of mercury p-tolylmercaptide and benzylmercaptide are HgS and the corresponding sulfides o r compounds derived from further decomposition of the sulfides [127].

c) Compounds with an Se-Hg Bond

Mercury alkylselenides (RSe)2Hg are obtained s imilar ly to the mercaptides, from alkaneselenols and mercur ic oxide or cyanide [203]. (CH3Se)2Hg has been prepared by pouring CH3SeH into Hg(CN)2

with cooling [203, 204], and its ethyl analog by the interaction be-tween C2H5SeH and HgO [203, 204]. As for the alkyl mercaptides, the reactions are exothermic.

Bubbling of dialkyl diselenides into an aqueous solution of m e r -curic chloride (acidified with HCl) or cyanide results in cleavage of the Se-Se bond (difference from dialkyl disulfides) and the f o r -mation of RSeHgCl, the double salt RSeHgCl.HgCL, and possibly RSeHgCN (R = CH3) and (RSe)feHg (R = C3H5) [205].

Reactionof dimethyl diselenide with mercuric chloride [205]. T h e a d d i t i o n o f d i m e t h y l diselenide (or its solution in alcohol) to a solution of 10 g of HgCl 2 in 80 ml of water and 20 ml of HCl resu l ts in yel lowish needles of CH 3 SeHgCl-HgCl 2 , m.p. 123°C. The sub-stance probably contains some CH 3 SeHgCl .

The salts of other mercury alkylselenides were prepared in an analogous manner.

Diperfluoromethyl diselenide does not form a double salt with HgCl2 or HgI2; simple shaking with metallic mercury gives (CF3Se)2

Hg [206], which also forms in quantitative yield in the interaction between CF 3 SeCl and Hg.



Preparation of mercury bis-trifluoromethylselenide [206]. (CF8)2Se2 (0.618 g) is sealed in a quartz Carius tube with 2 ml of mercury and the mixture shaken for 20 hours at a distance of 4 cm from a mercury lamp. The resulting volatile products are (CF3)2

Se2 and possibly (CF3)2Se. The residue is extracted with ether and the material left behind after evaporation of ether from the extract sublimed in vacuum at 50°C. This procedure gives 0.385 g of yellow needles of mercury bistrifiuoromethylselenide. After repeated sublimation, the melting-point is 5°C. The yield is 96% with more energetic shaking and direct sublimation without the extraction with ether.

(CF3Se)^Hg reacts with chlorine as follows:

(CF3Se)2 Hg -f Cl2 2CF2SeCl 4- HgCl2

CF3SeHgCl is probably formed as an intermediate. An analogous reaction occurs with bromine.

At room temperature, (CF3Se)2Hg reacts only very slightly with HCl and g ives a low yield of CF3SeH and other products at 50-100°C [206], CF3SeHgCl (m.p. 185-190°C) has been made by the reaction of (CF3Se)2Hg with HgCl2 in ether [206].

Ar2Hg and ArSeH in benzene give (ArSe)2Hg [328], ( Q-C10H7SeJ2Hg has been prepared by treating an alcoholic solution of selenonaphthol with a solution of mercur ic acetate [207],

Diaryl diselenides and m e r c u r i c chloride (in aqueous alcohol) give only the double salts A r ^ e ^ H g C l g [208].

d) Compounds with a Ge-Hg Bond

The interaction of 1 mole of diethylmercury with 2 moles of t r i -ethylgermane in the absence of aer ia l oxygen, at 100-120°C, g ives r i s e to ethane and bis-( tr ie thylgermyl)-mercury yield: 66.5% [322].

2 (C2H5)3GeH + (C2H5)2 Hg - 2QH6 + [(C2Hs)3 Ge]2 Hg

This product is a thermally stable but highly react ive compound; it is readily oxidized in a ir to triethylgermanium oxide:

2 [(C2H5)3 Ge]2 Hg + O2 2 [(C2H5)3 Ge]2 O + 2Hg

On ultra-violet irradiation, b is- ( tr ie thylgermyl)-mercury decom-poses quantitatively into mercury and hexaethyldigermane; the same rea ion o c c u r s in the presence of benzene. Photolysis in CCl 4 r e -sults in m e r c u r y , tr iethylchlorogermane and hexachloroethane, whereas in bromobenzene the products are (unexpectedly) tr iethyl-bromogermane, diphenylmercury and metall ic m e r c u r y . The r e -action with benzoyl peroxide (3-5 minutes in benzene at 20°C) is

[(C2H5)3 Ge]2 Hg + (C6H5COO)2 -> Hg + 2 (C2H5)3 GeOCOC6H5

An analogous reaction occurs with cyclohexyl peroxide [322]. The reaction with RBr proceeds according to [321]

[(C2H5)3 GeJ2 Hg + 2RBr 2 (C2H5)3 GeBr + R2Hg


Preparation of bis-(triethylgermyl)-mercury [320], T h e reaction i s c a r r i e d out under nitrogen. T r i e t h y l g e r m a n e (6.83 g) and diethylmercury (5.5 g) are heated to 100-120°C in a vesse l f itted with a ref lux condenser connected to a gas buret and 920 m l (96.8%) of ethane col lected (the gas is identified chromatographical ly) . T h e mixture is fract ionated under vacuum in a current of nitrogen. T h e fract ions a r e col lected in ampoules which are sealed off in. the c o u r s e of the process without interrupting the disti l lation. Xhe yie ld of b i s - ( t r i e t h y l g e r m y l ) - m e r c u r y is 7.34 g (66.5%); b . p . 1 1 8 - 1 2 0 ° C / 1 . 5 mm; n^,20

1.5696. The compound, a lemon-yel low liquid, produces m e r c u r y on contact with air.

e) Compounds with Si-Hg and Ge-Hg Bonds

The interaction of diethylmercury with triethylsi lane (at 130-140°C) is slower and more complicated than the corresponding reaction with triethylgermane. The products are C2H5HgSi(C2H5)3, [(C2H5)3SiJ2Hg and metallic mercury [321],

Bis-( tr iethyls i ly l ) -mercury is also formed in a disproportionation reaction [322]:

170°C 2C2H5HgSi(C2H5)3 ^ Ji-^8 (C2H5)2 Hg + [(C2H5)3 Si]2 Hg

Under the action of light, [(C2H5)3SiJ2Hg decomposes into Hg and (C2H5)6Si2 [321]. The oxidation

[(C2H5)3SiJ2Hg + O 2 [(C 2 H 5 ) 3 SiJ 2 O+ Hg proceeds readily [321].

The reaction of pentaethyldisilane and diethylmercury (19 hours at 155-160°C) gives a compound containing the group

\ I ! / —SiSiHgSiSi-/ I I \

as well as other products [332]:

(C2H5)3SiSi (C2H5)2 H J- (C2H5)2 IIg C2H6 + C2H5HgSi (C2H5)2 Si (C2H5)3

+ [(C2H5)3 SiSi (C2H5)2J2 Hg + Hg

Compounds containing Si-Hg-Ge and Si-Si-Hg-Gebondshavebeen synthesized according to the scheme:

(C2H5)3 GeH + C2H5HgR ^ C2H6 + (C2H5)3GeHgR

where R = (C2H5)3Si and (C2H5)3SiSi(C2H5)2. These reactions proceed under mild conditions, over 1 - 2 hours

at 100°C. The f irst of these compounds was obtained in 26% yield. It is a lemon-yellow liquid, b.p. 130-131°C/1 .5 mm. The second compound was prepared in a yield of 50.4%; b.p. 159-163°C/l mm. Both compounds are very sensitive to oxygen. Ultra-violet i rradia-tion results in the reaction:

ftv

(C2H5)3GeHgSi (C2H5)3 —> Hg + (C2H5)3GeSi (C2H5)3

The interaction of (C6H5)3SiLi WithHgCl2 gave (C6H5)3SiHgCl [323]. References see page 4 <>4


f ) Compounds with an N-Hg Bond

N - H g D e r i v a t i v e s of A m i n e s

P r i m a r y aliphatic amines react with m e r c u r i c sal ts under mild conditions (in aqueous solutions, in the cold or with moderate heating) to give compounds RNHHgX, RN(HgX)2, or [RN(HgX)J2Hg, depending on the relative proportions of the reactants and on the reaction conditions.

Thus, gradual addition of a weakly acidified solution of mercur ic chloride o r nitrate of medium concentration to a concentrated solu-tion of methylamine g ives a finely crystal l ine powder CH3NHHgX (X = Cl or NO5) insoluble in water , alcohol, o r ether [209].

Preparation of methylaminomercury nitrate [209]. S t i r r ing of an aqueous solution of m e r c u r i c nitrate into a concentrated aqueous solution containing a s m a l l e x c e s s of methylamine r e s u l t s in a voluminous white precipitate which t r a n s f o r m s into a white powder a f ter moderate heating on a water bath. The substance is insoluble in the usual organic solvents and decomposes on heating without fusion. Ethylaminomercury nitrate and a m y l a m i n o m e r c u r y nitrate have been prepared by the s a m e method.

The addition of a solution of methylamine (with stirring) to a concentrated solution of m e r c u r i c ChloridegivesCH3N(HgCl)2 [210],

The interactions between HgCl2 and aqueous solutions of aliphatic amines taken in excess lead to compounds which according to [211] have the composition [RN(HgCl)2J2Hg ( R = CH3, C2H5, n-C3H7) and the structure

R R \ /

N - H g - N / \

ClHg HgCl

Whereas N-benzylacetamide is mercurated in the benzene ring (see Chapter 5), according to [212] benzylamine f o r m s only an N-m e r c u r y derivative with m e r c u r i c salts . This latter compound, C6H5CH2NHHgCl, was obtained by treating 4 moles of benzylamine in boiling aqueous solution with 1 mole of m e r c u r i c chloride and boiling the precipitate with alcohol [212, 213]. The corresponding sulfate is made by precipitating a solution of the double salt of benzylamine and m e r c u r i c acetate with Na2SO4. The action of barium hydroxide on the sulfate gives C6H5CH2NHHgOH [213].

Bis-(ditr i f luoromethylamino)-mercury, [(CF3)2N]2Hg, can be prepared [214] by adding m e r c u r i c fluoride to the double bond in perf luoro-2-azapropene (in an autoclave at 100°C):

2CF3N = CF2 + HgF2 (CF3)2N — Hg — N (CF3)2

o r by the interaction between bromo-bis-(tr i f luoromethyl)amine


and metal l ic mercury at room temperature (15 hours in a sealed tube):

(CF3 )2 NBr + H g - * [ (CF3 )2 N ] , H g

Synthesis of bis-(ditrifluoromethylamino)-mercury [2141. P e r f l u o r o - 2 - a z a p r o p e n e (52 g, 0.4 mole) and 50 g or m e r c u r i c f luor ide a r e heated f o r 15 hours at 100°C in a s ta in less steel autoclave and 5 g of unreacted CF3N=CF2 a r e r e c o v e r e d when the autoclave is opened. Dist i l lat ion of the res idue g i v e s 70 g (yield: 79%) of the required product; b.p. 127°C; m.p. 17.5°C. In fact, the yield is probably higher; although all operations with the m e r c u r y compound a r e c a r r i e d out in careful ly dr ied a ir , considerable l o s s e s o c c u r during the manipulations.

Bis-(ditr i f luoromethylamino)-mercury is very sensit ive to the slightest t r a c e s of moisture and decomposes immediately with the formation of a yellow solid. It decomposes on heating to 150°C, probably to the starting m a t e r i a l s , but r e - f o r m s on cooling. The action of bromine on [(CF3)2NJ2Hg in careful ly dried CCl4 at room temperature results in a replacement of the m e r c u r y atom by bromine, giving a 90% yield of bromo-di(trif luoromethyl)amine [214], The actions of NOCl and NO2Cl on[(CF3)2NJ2Hg give, r e s p e c -tively, (CF3)2NNO and (CF3)2NNO2 [214a].

In the presence of acid chlorides (sealed tube, room tempera-ture), the m e r c u r y atom in [(CF3)2Nj2Hg is replaced by the acyl group [214b]:

[ (CF3 )2 NJ2 Hg + RCOCl -> RCON(CF 3 ) 2

The m e r c u r y derivative of glycine may also be an N-Hg deriva-tive [16].

T e r t i a r y enamines react with m e r c u r i c chloride or bromide in ethereal solution according to the scheme:

R 2 N - C H = CR 2 + 2HgX 2 [ R 2 N C H = CH 2 ]+ ( H g X 3 ) -

H g X

The reaction is conducted under nitrogen. The resulting amorphous precipitates are more stable when X = Cl than when X = B r [215a].

In the mercuration of aromatic amines by the usual mercurating agents, the f i rs t stage of the reaction is the formation of labile intermediates in which the m e r c u r y is l inkedtothe organic residue via nitrogen. Such intermediates are favored by a deficiency of acid in the reacting medium.

N-Mercuriani l ine, CgH5NHHgNHC6H5, has been made from aniline, m e r c u r i c chloride and alkali [212, 215-219],

According to [212] and [222], the product of the reaction between HgCl2 and aniline in alcoholic solution, C6H5NHgCl [220, 221], in-soluble in the usual solvents, is polymeric . It is purified by extrac-tion f rom boiling alcohol [223]. Its double compound with HgCl2 has the composition 5C6H5NHHgC1.2HgCl2 [213].



Aniline hydrochloride and mercuriacetamide give in water a

product having the structure C 6 H 5 N \ ^ g Q j 1 t 2 2 4 , 225].

N-Hg derivatives of naphthylamines and substituted naphthyl-amines have been described [12, 229-232].

The action of mercuric chloride (also in the presence of soda) on other aromatic amines (aniline, methylaniline) gives r ise to ArNHHgCl [13]. Dimethylaniline gives a P e s c i product, containing an N-Hg bond and at the same time mercurated in the ring (see Chapter 5).

Preparation of chloromercurianiline [ l3 ] . T h e action of a solution of 3 g of NaHCOg and of a hot aqueous solution of 9 g of HgCl2 on an alcoholic solution of 3 g of aniline g ives a yel low precipitate of chloromercuriani l ine .

The mercury salt of trinitromethane, which mercurates aromatic hydrocarbons and many of their derivatives, gives the N-Hg com-pound C6H5NHHgC(NO2)3 with alcoholic aniline at 20°C [226].

Jackson and Peaks [227] obtained red or brown precipitates from mercuric nitrate and nitroaniline in the presence of alkali and con-sidered the products to contain N-Hg linkages. Kharasch [228] ascribed a quinoneimino-acinitro structure to the brightly colored products formed from the interaction between mercur ic acetate and o- or p-nitroaniline.

An insoluble and probably polymeric compound [CF3CONJ2Hg has been obtained [214b] from the reaction of C F3 CONHNHCOC F3 and mercur ic acetate in aqueous solution slightly acidified with acetic acid.

(CF3CO)4N2 has been made from (CF3CON)2Hg and CF 3 COCl in a fluorinated hydrocarbon at 50° C [214b].

Preparation of tetrakis-(trifluoroacetyl)hydrazine [214b]. C F a C O C l (38 g, 0.29 mole) and 50 g of a f luorinated hydrocarbon solvent boiling around SOcC are condensed in a rotary autoclave containing 57 g (0.14 mole) of care fu l ly dried (CF3 C0N)2Hg. T h e reaction is continued for 14 hours at 50°C. The volati le products a r e pumped off and the residue fractionated; b.p. 108°C/760 min; yield: 53 g.

N - H g D e r i v a t i v e s of A m i d e s , Im ides a n d H y d r a z i d e s

Mercury replaces the hydrogen carried by an amide nitrogen more easi ly than an amine hydrogen, but the easiest substitution occurs with an imide hydrogen.

Dissolution of mercur ic oxide in molten or dissolved amides results in the formation of (RCONH)2Hg, containing N-Hg bonds which are unaffected by alkalis but cleaved by acids, sulfides, or the iodine ion. Mercuriformamide exists only in solution [233]. The interaction between mercuri formamide and HgO in alcohol g ives an amorphous precipitate of HCONHHgOH, which forms


compounds HCONHHgCl.HCl and 2HCONHHgC1.3HCl with HCl. Mercuriacetamide (CH3CONH)2Hg has been made [16, 31, 234-238] by fusing HgO and acetamide at 180°C (see under "Mercuration of aliphatic and al icycl ic structures" Chapter 5). Other mercurated acid amides can be prepared in the same way. Reports have been published on the preparations of (ClCH2CONH)Hg [239, 240], (NO2CH2CONH)2Hg [241], (CH3CH2CONH)2Hg [242, 243], (C3H7

CONHJ2Hg [244, 245] mercuri tartramide [246], mercurioxamide [244, 247], mercurisuccinamide [248], mercurisuccinimide [244, 245, 248, 249], mercuri fumaramide [241, 245] and others. For the structure of mercuriacetamides see [16].

The mercurisuccinimide obtained by the action of mercur ic acetate on succinimide in aqueous alkali cooled with ice is not very pure [250].

N-Mercuriheximide (I') has been made by the action of m e r c u -r ic acetate on heximide (I) [258]:

I V

The m e r c u r y derivatives (RCONH)2Hg where R = CF 3 , C2F5 and C 3 F 7 have been made [251] in quantitative yields by heating the corresponding amides with an excess of red m e r c u r i c oxide for 5 minutes at 150-170°C and extracting the products with boiling alcohol. The melting-points of these compounds are , respect ively , 219, 244 and 286°C.

For some N-Hg derivatives of barbituric acid and s imi lar com-pounds, see below under "N-Hg derivatives of some heterocycl ics ' ' .

Many compounds of urea with mercur ic salts (also in the form of double salts with urea and sometimes HX), CO(NHHgX)2, where X = OH [212, 245, 252], Cl [253, 254] (m.p. 125-128°C) [253], NO3

[252, 254], SO4 [254], CH3CO2 [254] have been prepared in water (sometimes with slight warming) or in methanol o r ethanol. The structures of nitratomercuriureas have been described [255]. Titration of urea with solutions of m e r c u r i c salts by P f e i f f e r ' s method has been studied [256, 257].

For the mercury compounds of cycl ic urea derivat ives, see below under "N-Hg derivatives of some h e t e r o c y c l i c s " .

The action of aqueous or alcoholic mercuriacetamide on acetyl-urethane AcNHCO2Et and its substituted amides AcNHCONHRgives products having the general formula Hg(NAcCONHR)2. The action of hydrazine or phenylhydrazine on these compounds results in separation of metallic m e r c u r y [259].

According to [260], the mercury derivatives of aliphatic amides



are best obtained by fusion of the amide with HgO [245] and extrac-tion f rom the reaction mixture with cold alcohol. On the other hand, the m e r c u r y derivatives of the aromatic amines, such as benzamide, p-chlorobenzamide, bromobenzamides, toluamides, o-anisamide and sal icylamide, which are insoluble in cold alcohol, are more conveniently made in the following manner.

Preparation of the mercury derivatives of aromatic amides [260]. Yel low m e r c u r i c oxide (5 g) and the amide (4 g) a r e added to 50 ml of 95% alcohol and the mixture boiled f o r an hour and f i l tered hot through a s intered-g lass crucible . The f i l t rate is then cooled with ice and the result ing c r y s t a l s f i l tered off and washed with cold alcohol or ether. T h e melt ing-points of the m e r c u r y derivat ives are as fol lows: benzamide 222°C, p - t o l u -amide 260°C, p -chlorobenzamide 258°C, p-bromobenzamide, 266°C, sa l icy lamide 290°C (280°C).

Mercuribenzamide (C7H6ON)2Hg has also been obtained [245, 261, 262] by dissolving mercur ic oxide in aqueous benzamide. The compound is very stable and can be recrysta l l i zed from warm aqueous KOH.

Mercuricuminamide [263] [(CH3)2CHCgH5CONHJ2Hg.^H2O, m.p. 190-191°C, c rys ta l l i zes from aqueous alcohol. It is insoluble in water but dissolves in ether. Mercuriphthalimide is a powdery precipitate [264].

Mercuriamides (RCONH)2Hg are reduced by alkyl phosphites to give metal l ic mercury , the amide and nitrile of the acid and a phosphate [265],

Al l mercuriamides , in particular mercuriacetamide, are de-stroyed by ammonium or mercurous salts with the formation of inorganic mercury compounds [224], and by the action of hydrazine and hydrazobenzene with the formation of mercury [266].

The N-Hg derivative of benzoylcyanamide has been made [267] by the action of mercuric acetate on an aqueous solution of its alkali metal salt.

The mercury derivatives of the imides are more stable, for example to hydrochloric acid, than those of the amides [244].

For the preparation of the mercury derivatives of amides see also [268, 269] and under "Mercuration of aliphatic and al icycl ic s t ructures" , Chapter 5.

N-Acylated aromatic amines also form N-Hg compounds with m e r c u r i c sal ts .

With mercur ic bromide and sodium ethoxide, formanilide gives N-mercur i -b is- formani l ide (C6H5NCHO)2Hg. N-chloromercur i for-manilide, C6H5N(HgCl)CHO, [270] is formed from formanilide, mercur ic chloride and sodium ethoxide.

A compound having the composition Hg[N(COCH3)C6H5J2 [236, 271] is formed when acetanilide is fused with m e r c u r i c oxide. Th i same compound is obtained if an aqueous solution of 2 moles acetanilide and 1 mole of mercur ic chloride is treated with a to a strongly alkaline reaction [272J.


The N-mereurated derivatives of other aromatic amines, e.g. N-acylnaphthylamines [229-232], are prepared by analogous methods.

Phenylurea reacts with mercuric chloride in boiling water (to give (C6H5NHCONHHgCl)3(HgCl2)2 which does not give a reaction for the mercuric ion) or in acetone with heating on a water bath. In the latter case the products are Hg[OC(NH2)NHC6H5]nCl2, where n = 1 or 5 [273].

C6H5(C2H5)NCONH2, (C6H5)2NCONHC2H5 and C6H5(C2H5)NCONHC6H5

form complexes Hg[OC(NHR)NRR']Cl2 with aqueous mercur ic chlo-ride in the cold [273]. Several substituted ureas do not react with aqueous HgCl2 [273].

Diphenylcarbazide reacts with mercuric and mercurous nitrates (in the presence of a boric acid/borax buffer) in aqueous alcohol to give compounds containing the N-Hg bond. In the case of mercur ic salt the diphenylcarbazide is oxidized to diphenylcarbazone and the product is an N-Hg derivative of the latter compound [274].

Similarly to the N-Hg derivatives of N-acylamides, the N-Hg derivatives of anilides decompose into the anilide and a mercury salt under the action of potassium iodide, thiosulfate, or ammonium bromide [229].

Treatment of sulfanilamides with mercur ic acetate in 98% acetic acid gives N-Hg derivatives and in hot water both N-Hg and C-Hg derivat ives. In hot 40% acetic acid the products do not contain the N-Hg bond [275].

The triamide of benzene-l ,3,5-tr isulfonic acid, C6H3(SOfeNH2)3, g ives on boiling with mercur ic oxide (1 part of the amide plus oxide obtained from 1.3 parts of HgCl2) a precipitate having the composition Hg3(C6H6O6N3S3)2 [276]. When a solution of 1 part of this amide is boiled with mercur ic oxide obtained from 2.6 parts of HgCl2 the precipitate is (HOHg)3C6H6O6N3S3 [276].

The N-mercurous derivative Hg2N2(COCH3)2 is obtained in the form of an orange powder [277] by adding an acidified aqueous solution of mercurous nitrate to N,N'-diacetylhydrazide. Its s truc-ture has been confirmed by X - r a y analysis and infra-red spec-troscopy. In the mixing of aqueous solutions containing HgCl2 and N,N'-diacetylhydrazide in equimolar proportions, the resulting mercur ic derivative Hg(NHCOCH3)2 is obtained in a purer form if this reaction is carr ied out in the absence of sodium ethoxide [269] (contrary to Stolle's recommendations [278]). Heating of m e r c u r i -acetamide to 240°C resul ts , owing to its partial decomposition into Hg and diaeetylhydrazide, in mercuration of the latter both at nitrogen and carbon, and in the formation of Hg2NC2H2O^ [269].

N - H g D e r i v a t i v e s of D i a z o a m i n o C o m p o u n d s

Compounds (ArN=N-N-Ar)2Hg are most conveniently prepared by mixing methanolic mercur ic acetate with a methanolic or a



benzene solution of the diazoamino compound [279-281]. They can also be made by the action of mercur ic oxide on a solution of diazoaminobenzene in chloroform [282]. The m e r c u r y derivative of diazoaminobenzene is s imi lar ly formed in the interaction between mercur ic acetate and phenylhydrazine in aqueous solution in the cold [283] (cf. F i s c h e r ' s synthesis of diphenylmercury from m e r -curic acetate and phenylhydrazine in ether, see under "Synthesis of organomercury compounds by the action of arylhydrazines on mercur ic sa l ts" , Chapter 7).

The mercury and other metal derivatives of diazoamino com-pounds exist in only one form [284]. The formation of two, more or l e s s colored forms of these derivatives is ascribed to con-tamination. Thus the confirmation of the fumaroid-maleid theory of the color of diazoamino compounds, based on the existence of these f o r m s , is incorrect [284].

Preparation of the N-mercury s a l t of diazoaminobenzene [ 2 7 9 ] . A s o l u t i o n of 0 . 9 0 g of diazoaminobenzene in 10 ml of methanol is added to a solution of 0.78 g of mercuric acetate in 20 ml of methanol acidified with 4-5 drops of dilute acetic acid. A yellow flaky precipitate appears immediately in quantitative yield. The product is recrystal l ized from benzene or (better) from toluene; golden-yellow needles; m.p. 232°C.

N - H g D e r i v a t i v e s o f C y a n i c A c i d s

According to its Raman spectrum [18,19], the m e r c u r y derivative of cyanic acid, obtained by the action of methanolic HgCl2 on s i lver cyanate, is an Hg-N compound (OCN)2Hg. The reaction is best con-ducted in ether [125, 256]. The actual details of the preparation are given in Chapter 5. Mercuric cyanate has also been made by neu-tralization of HgO in ether by cyanic acid [286] and by heating mercurous cyanate in water with sodium cyanate in an aqueous solution acidified with nitric acid.

The structure of mercur ic cyanates as Hg-O or Hg-N compounds has not as yet been sufficiently elucidated.

N - H g D e r i v a t i v e s o f S o m e H e t e r o c y c l i c s

A s a rule, an insufficiency of acid in the medium during the action of mercur ic salts on nitrogen-containing compounds favors the formation of N-Hg (but not C-Hg) bonds [285]; see also Chapters 5 and 6. On the other hand, whereas in many c a s e s the reaction of mercur ic acetate on nitrogen-containing organic compounds r e -sults in C-Hg derivatives, the action of m e r c u r i c chloride on the same compounds leads to the formation of products containing the N-Hg bond. Thus, mercur ic acetate or cyanate mercurate pyrrole and its derivatives lead to C-Hg compounds (see under " M e r c u r a -tion of heterocycl ic compounds" Chapter 5). Theact ionof mercur ic


chloride on pyrrole [286], 2,3-dimethyl- and 2 ,4-dimethyl-3-car-boxypyrrole [286], and 2-methyl-5- isopropylpyrrole [287] gives only N-Hg products and their double salts with HgCl2 [288].

The mercury derivative of isatin, Hg(C8H4C^N)2, which can be regarded both as an N-Hg and an O-Hg compound, obtained in best (95%) yield by the action of a concentrated solution of mercur ic acetate on a boiling alcoholic solution of isatin, consists of dark red c r y s t a l s [289]. The compound dissolves in dil. KOH to give a yellow color and gives Hg(NHC6H4C0C00H)2.2H20 when the solution is acidified with dilute sulfuric acid.

The action of mercur ic oxide or calomel on antipyrine in the presence of sufficient alkali to combine the Cl ' ion results [64] in compounds (R2N)2Hg; if the amount of alkali is insufficient, the products are RNHgCl [290]. A compound having the formula C3H3N2HgClO4H2O, which is probably polymeric , precipitates from solutions of imidazole and mercur ic perchlorate at pH values greater than 4.5 [325].

Aqueous solutions of the alkali metal salts of barbituric [267], diethylbarbituric [291], phenylethylbarbituric [291] and violuric [267] acids form N-Hg compounds with mercur ic acetate. This method has also been used to prepare m e r c u r i c derivatives of methyluracil [267] and uric acid [267].

The N-Hg compounds of pyrimidine and its derivatives, in-cluding purines, belonging both to the type (RN)2Hg and to type RNHgHal, are obtained by the interaction (in the cold or with heating) between alcoholic mercur ic chloride or bromide and a weakly alkaline solution of the corresponding heterocycle . Con-densation of the resulting mercury derivatives with acylated halogenopentoses or -hexoses is an important method of synthe-sizing nucleosides [285, 292-311, 313]. The starting nitrogen base may also be an oxygen-containing derivative of pyridine in which the mercury is linked via the oxygen. Thus, both O- and N-gluco-sides were obtained from the O-chloromercuri derivative of a-hydroxypyridine [312].

Mercury salts of benzoxazolethiones form N-glucosides by an SiV 1 mechanism with halogenoacylaldoses [316] (in dimethylfor-mamide, at room temperature).

The m e r c u r y derivatives of purine bases were described ear l ier (see, for example, the chloromercuri derivative of adenine [314, 315]).

Synthesis of penta-acetylglucopyranosylguanine [306].

HgC I

.N N

CH3CO H P>

A

acetobromog lucose



OCOCH3

(1) Preparation of the chloromercuri derivative of acetylguanine: 0.016 g of NaOH in 1 ml of water and 1.5 g of HgCl2 dissolved in a small volume of hot methanol are added to a solution of 1 g of acetylguanine in 250 ml of hot aqueous methanol. The amorphous precipitate is filtered off anddriedin a vacuum desiccator. Yield: 1.7 g (76.7%).

(2) Preparation of penta-acetylglucopyranosylguanine: 1 g of carefully ground chloro-mercuri derivative of acetylguanine is suspended inabsolutexylene and part of the xylene distilled off until the distillate becomes clear. The suspension is then treated with 1.5 g of acetobromoglucose dissolved in xylene. The mixture is heated for 1 hour with vigorous stirring, the hot solution decanted and the residue washed with chloroform. The choroform and the xylose solutions are combined, washed with 30% KI solution, dried over sodium sulfate and evaporated to dryness under vacuum. The resulting oil is dissolved in the smallest volume of absolute ethanol and the solution precipitated with absolute ether. The precipitate is ground up twice with absolute ether and recrystallized from water. Yield: 0.5 g (42%); m.p. 295°C (with decomposition).

On treatment with methanolic NaOH penta-acetylglucopyranosy 1-guanine gives 9-/3-d-glucopyranosylguanine.

The mercury derivatives of pyrimidines decompose with the formation of the starting pyrimidine on treatment with hydrochloric acid.

Mercury isocyanurate (tricarbamide), [(C0)3N3]2Hg3.2H20, is obtained from trisodium isocyanurate and a m e r c u r i c salt at 100°C, and at any temperature from solutions of cyanuric acid and mercur ic salts [62].

When l ,6,8-triazabicyclo-(4,3,0)-3-nonene-7,9-dione is boiled with m e r c u r i c acetate in methanol, the hydrogen c a r r i e d by the nitrogen atom in position 8 is replaced by m e r c u r y :

N - C O x H g ( O C O C H 3 ) 2 / N N - C C K i N - C O Z n h " ^ T * I J N - C 0 Z n h ^ o c o c h 3

This compound changes immediately into the product of addition of HgO2CCH3 and OCH3 a c r o s s the C=C bond when nitric acid is added to the reaction mixture [317].

g) Compounds with a P-Hg Bond

Dialkyl phosphonates are mercurated by m e r c u r i c acetate or by mixtures of HgO and m e r c u r i c halide or acetate to give dialkoxy-phosphinylmercury salts , which contain the P-Hg linkage [318]:

(RO)2P(O)H + Hg(O2CCH3)2 -> (RO)2 P (O) HgO2CCH3 + CH3COOH (1 )


( RO ) 2 P (O )H + H g O + H g X 2 -> 2 (RO) 2 P (O) H g X - f H 2 O ( 2 )

Reaction (1) proceeds under mild conditions at room temperature and in solution (in toluene (for R = ethyl) or in ethylbenzene or n-octane for the other alkyl derivatives). Reaction (2) is carr ied out in boiling benzene. The acetic acid formed in reaction (1) and the water formed in reaction (2) are removed by azeotropic distillation. The yields are 78-92%. The reaction with mercur ic acetate can also be conducted in the absence of solvent; considerable heat is then evolved and the product is l e s s pure.

The interaction between 2 moles of dialkyl phosphonate and 1 mole of m e r c u r i c oxide in benzene or ether yields bis(dialkoxy-phosphinyl)mercury [319]:

2 (RO) 2 P (O ) H + H g O - » [ (RO) 2 P (O ) ] , Hg + H 2 O

which converts into dialkoxyphosphinylmercury chloride on treat-ment with mercur ic chloride in boiling benzene:

[ (RO) 2 P (O ) ] , Hg + HgCl 2 -> 2 (RO) 2 P (O) HgCl

Preparation of diethoxyphosphinylmercury acetate [318]. A vigorously s t i r r e d s u s -pension of 350.5 g of m e r c u r i c acetate (1.1 mole) in 500 ml of dry toluene is treated at room temperature with 138 g (1.0 mole) of diethyl phosphonate. The mixture is s t i r r e d f o r 2 J4 hours, keeping the temperature below 25°C with the aid of an i c e bath, the insol-uble mater ia l (3 g) is f i l tered off and the acetic acid f o r m e d azeotroped off with toluene at 60 mm until the temperature r i s e s to 36°C and the volume of the dist i l la te r e a c h e s 175 ml. (Distil lation at higher t e m p e r a t u r e s resul ts in considerable amounts of meta l l ic m e r c u r y . ) A f t e r f i l trat ion, evaporation of the f i l t ra te g ives 330 g (yield: 83.3%) of crude product, which is subsequently r e c r y s t a l l i z e d f r o m toluene or f rom a mixture of benzene with ether; m.p. 106.8-107.6°C.

Other dialkoxyphosphinylmercury acetates (R = n-propyl, isopro-pyl, n-butyl, isobutyl, n-amyl , n-hexyl and n-heptyl) w e r e prepared in the same way. T h e r e a c t i o n s w e r e c a r r i e d o u t in ethylbenzene or , better, in n-octane. The acetic acid must be careful ly distilled off as the crude acetates are very soluble in this compound.

Dialkoxyphosphinylmercury chlorides and bromides can be ob-tained either from the acetates by means of aqueous alkali metal halides, o r directly from the dialkyl phosphonates by mercurating the latter with a mixture of HgCl2 (HgBr2) and HgO in boiling benzene. The iodides have been obtained only by the latter method.

Dialkoxyphosphinylmercury chlorides have also been prepared by the reaction of bis-(dialkoxyphosphinyl)mercury with mercur ic chloride in benzene.

Preparation of di-n-propoxyphosphinylmercury bromide [318]. A mixture of 8.3 g (0.05 mole) of d i -n-propyl phosphonate, 5.4 g (0.025 mole) of m e r c u r i c oxide and 9.0 g (0.025 mole) of m e r c u r i c bromide is boiled f o r 3 hours in 50 ml of dry benzene with continuous dist i l lat ion (and col lect ion) of the water formed. Soon af ter the beginning of boiling the orange c o l o r of m e r c u r i c oxide becomes white. The mixture is then cooled and the inorganic substances (2.6 g) f i l tered off. Evaporation of the f i l t rate g i v e s



a s irup which rapidly c r y s t a l l i z e s on addition of petroleum ether. Yie ld: 14.8 g (66.4%); m.p. 67-68.5°C. Two r e c r y s t a l l i z a t i o n s f r o m hot hexane give the pure product, m.p. 70.0-70.4°C.

Preparation of di-n-propoxyphosphiny lmercury iodide (n-C3H70)2 P(O)HgI [318]. A mixture of 8.3 g (0.05 mole) of di-n-propyl phosphonate, 5.4 g (0.025 mole) of m e r c u r i c oxide and 11.3 g (0.025 mole) of m e r c u r i c iodide is boiled for 5 hours in 50 ml of benzene. The water formed i s not col lected owing to strong foaming. The red c o l o r of the iodide disappears rapidly, but the precipitate has the c o l o r of m e r c u r i c oxide. The inorganic sal ts a r e f i l tered off and the f i l t ra te dried. Evaporation of the solvent g ives a cons idera-ble amount of an unidentified yellow amorphous precipitate, which is extracted with boil-ing hexane. T h e extract is dried and concentrated; this procedure y ie lds 12.1 g (49.1%) of crude product, m.p. 74 .6-75.6°C. Recrysta l l i zat ion from w a r m hexane g ives the pure iodide, m.p. 7 5 . 2 - 7 6 ° C . S imi lar methods are used to obtain diethoxy- and di-n-butoxy-phosphinylmercury iodides, in y i e l d s of 61.0% and 41.9%. The melting-points of the latter two compounds are , respect ive ly , 102-102.5 and 56-57.2°C.

Preparation of bis-(dimethoxyphosphinyl) mercury [319], HgO (49 g, 0.23 mole) is added to a v igorously s t i r r e d solution of 50 g (0.45 mole) of dimethyl phosphonate in 75 ml of dry benzene at room temperature. A further 50 ml of benzene are added at the end of this addition, the p r e s s u r e reduced to 200 mm and the mixture boiled at 40-45°C. The reaction water is dist i l led off as an azeotropic mixture with benzene and intercepted in a trap. (Although some m e r c u r i c oxide remains unreacted, the reaction may be regarded as completed when no m o r e water c o l l e c t s in the trap.) The product precipitates out of the benzene solution on cooling. A single r e c r y s t a l l i z a t i o n f r o m benzene g ives 78.9 g (83%) of the required product. After three r e c r y s t a l l i z a t i o n s f r o m benzene the melting-point is 121.6-123 C. T h e n-butyl, isobutyl and n-propyl e s t e r s , prepared by the s a m e method, a r e purified by chromatography of the reaction mixture on a column packed with alumina by the wet method. T h e result ing crude e s t e r s a r e further purified by chromatography of their solutions in n-hexane.

Preparation of bis-(diethoxyphosphinyl) mercury [319]. M e r c u r i c oxide (108.3 g, 0.50 mole) is added in small portions to a solution of technical diethyl phosphonate (138.1 g, 1.0 mole) in 150 ml of absolute ether. T h e solution is heated to strong boiling a f ter about half of the HgO has been added, and the orange co lor rapidly disappears . When the react ion abates, the last portion of the HgO is added and the mixture boiled f o r 6 hours. T h e result ing turbid, gray liquid is set aside overnight and f i l tered to remove the insoluble res idue (1.6 g) consist ing of m e r c u r y and unreacted HgO. T h e f i l trate is evaporated under vacuum and 6.7 g (0.37 mole) of water col lect in the cold trap. The gray plates forming a f ter removal of the low-boil ing products are r e c r y s t a l l i z e d three t imes f r o m petroleum ether. Yie ld: 216.1 g (91.2%); m.p. 56.8-58.2°C.

Reaction of bis-(dialkoxyphosphinyl)mercury with mercuric chloride [319], Synthesis of diethoxyphosphinylmercury chloride (C2H5O )2P(O)IIgCl. T o a solution of 4.7 g (0.01 mole) of bis-(diethoxyphosphinyl) m e r c u r y in 20 ml of dry benzene is added 2.7 g (0.01 mole) of HgCl2 and the mixture boiled for 15 minutes and cooled to room tempera-ture. The smal l (0.5 g) amount of insoluble res idue is f i l tered off and 5.9 g (78.6%) of crude diethoxyphosphinylmercury chlor ide are obtained f r o m the f i l t rate ; the melting-point is 103-104°C a f t e r r e c r y s t a l l i z a t i o n f r o m CCI4 and then f r o m water.

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Haun, ibid., 92, 3151 (1959). 190. H. Zinner and C. G. D a s s l e r , ibid., 93, 1597 (1960). 191. H. Zinner and W. Thielebeule, ibid., 93, 2791 (1960). 192. H. Zinner and E. Wittenburg, ibid., 94, 1298 (1961). 193. H. Zinner and H. Schmandke, ibid., 94, 1304 (1961). 194. H. Zinner and M. P f e i f f e r , ibid., 94, 2792 (1961). 195. H. Zinner, B. Ernst and F. Kreinbring, ibid., 95, 821 (1962). 196. H. Zinner, K.-H. Stark, E. Michalzik and H. Kristen, ibid.,

95, 1391 (1962). 197. H. Zinner, W. Rehder and H. Schmandke, ibid., 95, 1805

(1962). 198. H. Zinner and F. Schneider, ibid., 95, 2295 (1962).


199. H. Zinner and F. Schneider, ibid., 95, 2769 (1962). 200. G. Sachs and M. Otto, ibid., 59, 171 (1926). 200a. D. C. Gregg, H. A. Iddles and P. W. Stearns, jun., J. org,

Chem., 16, 246 (1951). 201. B . Holmberg, B e r . dt. chem. Ges. , 89, 278 (1956). 202. R. J. Kern, J. Am. chem. Soc., 75, 1865 (1953). 203. C. Siemens, Justus Liebig 's Annln Chem., 61, 360 (1847). 204. A. Baroni, Atti Accad. naz. Lincei Rc. , 12, 234 (1930). 205. M. L. Bird and F. Challenger, J. chem. Soc., 570 (1942). 206. J. W. Dale, H. J. Emeleus and R. N. Hazeldine, ibid., 2939

(1958). 207. J. Loevenich, H. Fremdling and M. Fohr, B e r . dt. chem.

Ges . , 62, 2856 (1929). 208. W. E. Bradt and J. F. Green, J. org. Chem., 1 , 540 (1936). 209. M. Raffo and A. Scarel la , Gazz. chim. ital. , 45, 127 (1915). 210. P. C. Ray and N. Dhar, J. chem. Soc., 103, 3 (1913). 211. D. Stromholm, Z. anorg. allg. chem., 57, 72 (1908). 212. L. P e s c i , ibid., 15, 208 (1897); Gazz. chim. ital., 26, 54

(1896). 213. G. Andre, C. r . hebd. Seanc. Acad. Sci . , P a r i s , 112, 996

(1891). 214. J. A. Young, S. N. Tsoukalas and R. D. Dresdner, J. Am.

chem. Soc., 80, 3604 (1958). 214a. S. P. Makarov, V. A. Shpanskii, V. A. Ginsburg, A. I.

Shchekotikhin, A. S. Filatov, L. L. Martynova, I. V. P a v -lovskaya, A. F. Golovaneva and A. Ya . Yakubovich, Dokl. Akad. Nauk SSSR, 142, 596 (1962).

214b. J. A. Young, W. S. Durrel l and R. D. Dresdner, J. A m . chem. Soc., 84, 2105 (1962).

215. L. P e s c i , Gazz. chim. ital., 27, 568 (1897). 215a. K. Brodersen, G. Opitz, D. Breit inger and D. Menzel, B e r .

dt. chem. Ges. , 97, 1155 (1964). 216. L. P e s c i , Atti Accad. naz. Lincei Rc. , 1, 312 (1892). 217. L. P e s c i , Gazz. chim. ital., 22, 373 (1892). 218. L. P e s c i , ibid., 23, 529 (1893). 219. L. P e s c i , ibid., 28, 442 (1898). 220. C. Forster , Justus Liebig 's Annln Chem., 175, 29 (1874). 221. C. Forster , Ber . dt. chem. Ges. , 7, 294 (1874). 222. O. Dimroth and R. Otto, ibid., 35, 2037 (1902). 223. A. W. Hofmann, Justus Liebig 's Annln Chem., 47, 62 (1843). 224. O. Furth, Mh. Chem., 23, 1155 (1902). 225. E. C. Franklin, Am. chem. J., 47, 361 (1912). 226. S. S. Novikov, T . I. Godovikova and V. A. Tartakovskii ,

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(1908). 228. M. S. Kharasch, F. W. M. Lommen and I. M. Jacobsohn,

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(1893). 234. A. Strecker , Justus L iebig ' s AnnlnChem. , 103, 324(1857). 235. W. Merkownikoff, Z. Chem., 6, 534, (1863). 236. A . Oppenheimer and S. Pfaf f , B e r . dt. chem. Ges . , 7, 623

(1874). 237. G. Andre, C. r . hebd. Seanc. Acad. Sci . , P a r i s , 102, 116

(1886) . 238. W. Schoeller and W. Schrauth, B e r . dt. chem. Ges . , 32, 784

(1899). 239. N. Menschutkin and M. Jermolajev , Z. Chem., 7, 5 (1871). 240. L. Francesconi and G. de Plato, Gazz . chim. ital. , 33, 228

(1903). 241. W. P r a g e r , Mh. Chem., 33, 1285 (1912). 242. H. Ley and W. Fischer , Z. anorg. al lg. Chem., 82, 329

(1913). 243. F. Sestini, Z. Chem., 7, 34 (1871). 244. H. Ley and K. Schaefer , B e r . dt. chem. G e s . , 35, 1309 (1902). 245. V. Desaignes, Justus L iebig ' s Annln Chem., 82, 231 (1852). 246. K. Grote, ibid., 130, 202 (1864). 247. E. Scheitz, J. E. Marsh and A. Geuther, Z. Chem., 4, 299

(1868).

248. N. Menschutkin, Justus L iebig ' s Annln Chem., 162, 168 (1872).

249. M. Landsberg, ibid., 215, 209 (1882). 250. E. Lyons, J. Am. chem. Soc., 47, 830 (1925). 251. R. H. Patton and J. H. Simons, J. org. Chem., 21, 1199 (1956). 252. J. Liebig, Justus L ieb ig ' s Annln Chem., 85, 289(1853). 253. - . Werther, J. prakt. Chem., 35, 63 (1887). 254. G. Ruspaggiari , Gazz . chim. ital. , 27, 6 (1897). 255. B . Glassman, S. Skundina and F. A. Hoppe-Seyler, Hoppe-

S e y l e r ' s Z. physiol. Chem., 160, 77 (1926); Chem. Abstr . , 21, 751 (1927).

256. J. Novak, Chem. ZentBl. , 154 (1873). 257. E. Pfl i iger, ibid., 559 (1888). 258. T . Okuda, Y . Takanashi and M. Tsuruoka, Chem. A b s t r . ,

56, 7147 (1962). 259. L. D. Shah, J. Indian chem. Soc., 15, 149 (1938). 260. J. W. Wil l iams, W. T . Rainey, jun., and R. S. Leopold, J.

Am. chem. Soc., 64, 1738 (1942). 261. A . Oppenheim and - . Czarnomsky, B e r . dt. chem. Ges . , 6,

1392 (1873). 262. A . Ostrogovich, Justus Liebig 's Annln Chem., 291, 377

(1896).


263. F . Field, ibid., 65, 49 (1848). 264. M. Landsberg, ibid., 215, 172 (1882). 265. I. F. Lutsenko and V. V. Tyuleneva, Zh. obshch. Khim., 27,

497 (1957). 266. M. O. Forster , J. chem. Soc., 73, 783 (1898). 267. S. J. M. Auld, ibid., 91, 1045 (1907). 268. H. P . Kaufmann and K. J. Skiba, Fette, Seifen, AnstrMittel ,

59, 340, 498 (1957). 269. K. Brodersen and L. Kunkel, Z. anorg. allg. Chem., 298, 34

(1959). 270. H.V.Wheeler andB.W.McFarland, Am. chem. J . , 16, 542 (1894). 271. A . Piccinini, Gazz . chim. ital., 24, 457 (1894). 272. A . Piccinini , ibid., 24, 453 (1894). 273. F. V. Gizycki and L. Reppel, Arch. Pharm. , B e r l . , 289, 61,

33 (1956). 274. I. M. Korenman and A . S. D'yachkovskaya, Uchen. Zap.

gor 'kov. gos. Univ., 1953, no. 24, 139. 275. G. Rodighiero, Annali chim. appl., 39, 261 (1949). 276. C. L. Jackson and J. F. Wing, Am. chem. J. , 9, 3251 (1887). 277. K. Brodersen and L. Kunkel, B e r . dt. chem. Ges . , 91, 2698

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(1933). 280. A . Mangini, ibid., 65, 298 (1935). 281. A . Mangini, ibid., 67, 384 (1937). 282. R. Ciusa, Atti Accad. naz. Lincei. Rc . , 20, 578 (1911). 283. L. Vecchiotti and A. Capodacqua, Gazz . chim. ital., 59, 369

(1929). 284. F. P . Dwyer, Aust . Chem. Inst. J. P r o c . , 6, 348, 362 (1939);

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148, 155 (1925). 287. L. A . Chugaev and N. A. Shlezinger, Zh. russk . f iz . -khim.

Obshch., 36, 1261 (1904). 288. R. Wil lstatter and Y . Asahina, Justus L iebig ' s Annln Chem.,

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Soc., 78, 2117 (1956). 293. J. J. Fox, N. Yung, I. Wempen and I. L. Doerr , ibid., 79,

5060 (1957). 294. J. J. Fox, N. Yung and D. Van Praag, Fedn P r o c . Fedn Am.

Socs exp. Biol . , 16, 182 (1957).


295. J. Davoll and B. A. Lowy, J. Am. chem. Soc., 73, 1650 (1951). 296. A. M. Michelson and A. R. Todd, J. chem. Soc., 816 (1955). 297. J. J. Fox, J. E. Codington, N. Yung, Z. Kaplan and J. O.

Lampen, J. Am. chem. Soc., 80, 5155 (1958). 298. H. M. Kissmann and M. J. Weiss , ibid., 80, 2575 (1958). 298a. A . R. Restivo and F. A. Dondzila, J. org. Chem., 27, 2281

(1962). 298b. Brit . Pat. 875,971 (1960). 299. B. R. Baker, J. P. Joseph, R. E. Schaub and J. H. Wil l iams,

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(1955). 301. B. R. Baker and R. E. Schaub, ibid., 77, 5900 (1955). 302. N. W. Bristow and B. Lythoe, J. chem. Soc., 2306 (1949). 303. B. R. Baker , K. Hewson, H. J. Thomas, J. A. Johnson, jun.,

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4896 (1958). 305. H. J. Schaeffer and H. J. Thomas, ibid., 80, 3738 (1958). 306. Z. A. Shabarova, Z. P. Polyakova and M. A. Prokof 'ev, Zh.

obshch. Khim., 29, 215 (1959). 307. B. R. Baker and K. Hewson, J. org. Chem., 22, 959 (1957). 308. U.S. Pat. 2,885,396 (1959). 308a. Brit . Pat. 877,318 (1960). 309. J. E. Codington, J. Am. chem. Soc., 80, 5164 (1958). 310. H. Zinner and E. Wittenburg, Ber . dt. chem. Ges . , 95, 1866

(1962). 311. M. Hoffer, R. Duschinsky, J. J. Fox and N. Yung, J. Am.

chem. Soc., 81, 4112 (1959). 312. G. Wagner and H. Pischel , Naturwissenschaften, 48, 454

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Turikova, ibid., 155, 1108 (1964). 323. M. V. George, G. D. Lichtenwalter and H. Gilman, J. Am.

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325. P . Brooks and N. Davidson, J. Am. chem. Soc., 82, 2118 (1960).

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327. D. J. Foster and E. Tobler . J. org. Chem., 27, 834 (1962). 328. D. Spinelli and C. Del l 'Erba, Annali chim., 51, 45 (1961).

CHAPTER 17

Analysis of Organomercury Compounds

a) Qualitative Determination of Mercury in Organomercury Compounds

The presence of mercury in organic compounds can be detected easily by qualitative tests.

The sample is roasted with calcium oxide or s i lver permanganate [2] in a glass tube, 20-25 cm long and up to 0.5 cm in diameter, and the mercury condensing on the walls is observed visually or detected with dithizone. Alternatively, the sample is roasted with cupric oxide and mercury is detected on account of the fact that the liberated mercury vapor gives a dark spot of reduced palladium on a paper moistened with a solution of palladium chloride [3], The contrast of the spot can be increased by exposing the paper to ammonia vapor. When the sample liberates on decomposition unsaturated compounds, which likewise reduce palladium chloride, the mercury vapor is f irst collected on a gold foil or on the walls of the tube and then, after decomposition of the organic compound, is driven over to paper moistened with palladium chloride [4].

In a few cases organomercury compounds can be detected without preliminary decomposition. For example, the phenylmercury ion gives a particularly sensitive color reaction with dithizone [4a].

Phenylmercury acetate and ethylmercury phosphate have been detected spectroscopically with the aid of 2-(l,3-dioxoindan-2-ylimino)indan-l,3-dione [4b]. Some microanalytical reactions are known for organomercury salts with various anions [5],

b ) Quantitative Analysis of Organomercury Compounds

E l e m e n t a r y A n a l y s i s of O r g a n o m e r c u r y C o m p o u n d s for C , H, H g a n d O t h e r E lements

Macromethods. Practically no use is made today of macromethods for determining mercury in the presence of carbon and hydrogen. In Liebig's elementary analysis of organomercury compounds, the

506


mercury is trapped in the curved tip of a long combustion tube (method of Hofmann [6] and Frankland and Duppa [7]), or is co l -lected on gold foil (placed at the end of the tube), with which it forms an amalgam [1, 8, 9],

In the elementary analysis according to Dennstedt, modified by Falkov and Raiz iss [10], the Hg is absorbed on s i lvered asbestos.

Micromethods. A rapid method for the microanalytical deter-mination of Hg, C, H and halogens in one and the same sample of an organomercury compound has been devised by Korshun, Sheve-Ieva and Gel 'man [11], It is based on pyrolys is [12-16] and sub-sequent gravimetr ic determination of the elements present.

Carbon and hydrogen are determined in the conventional manner [12-15], whereas mercury and the halogen are retained in the com-bustion tube, in special holders consisting of transparent quartz tubes and fi l led with s i lver (in the case of halogens) and gold (in the case of mercury) , the s i lver and gold being used in the form of gauze, foil , or wire . The increase in the weights of the holders is determined. The results do not deviate from the calculated values by more than 0.3% for carbon and hydrogen and 0.5% for mercury and halogens. The same procedure can also be used for the simultaneous determination of Hg, C, H and S [16]. The method is also suitable for determining mercury in compounds containing nitrogen and in those containing heavy metals . When the sample contains both a heavy metal and a halogen, mercury can be deter-mined only if the metal does not form volatile halides on combustion.

In compounds containing C, H, F and Hg, the f i rst three elements can be determined after the mercury has been trapped on gold in a cooled zone.

S i m u l t a n e o u s De te rm ina t i on of C, H, Hg a n d H a l [11]

Apparatus. The apparatus is the same as that used for the simul-taneous determination of carbon, hydrogen and halogen in the special holder [16]. The positioning of the holder containing the gold, the sample and the oxidation zone is shown in Fig. 1.

F i g . 1 Tube for the determination of carbon, hydrogen and mercury



Fig . 2 Tube for the determination of carbon, hydrogen, mercury and halogens (or sulfur)

If the sample contains a halogen as well , a second trap, containing s i l v e r , is placed in the combustion tube. This arrangement is shown in Fig. 2. In this case , the l e n g t h o f t h e c o m b u s t i o n t u b e m u s t b e at least 30 cm. For rapid cooling of the absorption apparatus and the traps , use is made of metal blocks provided with suitable r e c e s s e s .

Reagents. Fine gold wire or foil is used to intercept the mercury and halogens are absorbed on s i lver gauze, foil , or w i r e , weighing about 3 g. S i lver-treated pumice cannot be used since it retains some of the mercury and therefore gives erroneous results for both the m e r c u r y and the halogen. The other reagents are those commonly used in the determination of carbon and hydrogen.

Analytical procedure. We shall discuss here only the deter-mination of mercury and the positioning of the traps and sample holder in the combustion tube because the remaining procedure, concerning the determination of carbon, hydrogen and halogens, is identical with the analysis of compounds containing no mercury [16].

Before use, the inset tube acting as the trap or holder in the analysis is boiled for 10 minutes in a 50% hydrochloric acid solu-tion and is then rinsed, dried and heated to a high temperature in the combustion tube. A 4-cm-long gold strip is then placed in the narrow part of the holder. This gold strip must be positioned loosely , so as not to hinder the flow of the gas .

The holder with the gold is f i rs t weighed. Before the analysis proper , the holder is placed in the combustion tube and a blank test is carr ied out. If the holder already contains some m e r c u r y , absorbed during previous analyses, the gold strip must be cooled with ice during the blank test and the combustion, so as to prevent finely divided mercury part ic les from being c a r r i e d out of the holder by the hot oxygen flowing from the heated combustion tube. In the combustion of the organomercury compound, the holder with the specimen tube inside, containing5-8 m g o f t h e sample, is pushed into the tube so that it is not l e s s than 5 cm from the oxidation zone. The flow of oxygen is adjusted to 30-35 ml/minute and combustion of the sample is started with the aid of a gas burner or an electr ic


furnace. Towards the end of the combustion, the wide part of the holder is thoroughly heated with the burner. The narrow part is not heated, otherwise the mercury collected there would evaporate. It must be added that only part of the mercury is deposited on the gold strip, the rest forming a fine gray deposit on the cold wal ls of the narrow part of the holder. Af ter the combustion, the burner is turned off , the cooling is discontinued, and oxygen is passed through the combustion tube for 10 minutes. The absorption apparatus is then disconnected and the tube immediately closed with a stopper. The holder is removed and the specimen tube is taken out. The holder is then taken into the weighing room, placed on a metal block by the balance and weighed 25 minutes after its removal from the tube [16].

If the sample also contains a halogen, a second quartz holder, containing metall ic s i lver in its narrow part, must be placed in the combustion tube. When the wide part of the combustion tube is 30 cm long, the two holders can be loosely disposed and the combustion takes place sufficiently far from the rubber stopper. C a r e must be taken that the entire s i lver strip is heated to 575°C, so that the mercury cannot be retained in the colder parts of the strip in the form of s i lver amalgam. The combustion is carr ied out as described above. When it is finished the burner is extin-guished, the furnace is removed from the s i lver and oxygen is passed through again for 10 minutes - for the f i rst 5 minutes with cooling. The holders with s i lver and gold are weighed 25 and 30 minutes, respect ively , a f ter their removal from the combustion tube.

It is advisable to regenerate the gold after each working day. For this purpose the holder is placed in a clean quartz tube with a drawn tip and the tube connected, via a small wash-bottle fil led with a 1:1 nitric acid solution, to a Mariotte f lask or a water pump; air is then sucked through the tube and the gold heated with a burner or a furnace. When all the m e r c u r y has been ex-pelled from the surface of the gold and from the holder, the latter is removed and the tube rinsed through with nitric acid.

Mercury can also be trapped on s i lver [16a] in a simultaneous determination of C, H and Hg when the organomercury contains no halogen. The sample is heated in oxygen to 900-950° C and the vapors are passed over Co3O4 (650-680°C) on corundum.

Determina t i on of C a n d H in O r g a n o m e r c u r y C o m p o u n d s

Macromethod. To determine only carbon and hydrogen in organo-mercury compounds, the sample is placed in a long combustion tube, 15-20 cm of which protrude from the furnace. The mercury and part of the water will settle on the walls at this end. A f t e r the combus-tion the water is transferred to an absorption apparatus by careful



heating. The mercury can also be trapped on gold, as in the m i c r o -method.

Micromethod. In the usual microanalytical method determination of carbon and hydrogen the use of metallic gold for the absorption of m e r c u r y is recommended. Gold in the form of a small wad is placed in the "spout" of the combustion tube. This permits the removal of mercury simply by heating this part or changing of the gold as it amalgamates.

D e t e r m i n a t i o n of H g in O r g a n o m e r c u r y C o m p o u n d s , t o g e t h e r with E lements O t h e r t h a n C a n d H

Several wet methods have been devised for the decomposition of organomercury compounds with a view to determining their con-stituent m e r c u r y . These are exemplified by decomposition through heating with sulfuric and nitric acids [17], sulfuric acid and hydro-gen peroxide [18-21] and sulfuric acid and permanganate [22-25]. The most rel iable and widespread of these is a method based on the Car ius decomposition with fuming nitric acid in a sealed tube. The mercury mineralized by these techniques is then determined by conventional analytical methods such as titration with thiocyanate, precipitation as mercur ic sulfide, electrolytic methods including Verdino's microelectrolyt ic technique [26-28], color imetr ic meth-ods, and so on.

Organomercury compounds can also be decomposed in such a way that the mercury is isolated in the form of metall ic mercury or the amalgam. For example, the sample may be boiled with zinc dust in a neutral [29, 30] or an alkaline [31, 32] medium (see also [33]); the resulting amalgam is dissolved in nitric acid and the mercury determined in the usual manner. Other methods put forward include reduction with metallic aluminum in a neutral or a weakly alkaline medium [34], with stannous chloride [35], monoethanolamine and metall ic sodium in dioxan, etc. , but these are less rel iable and less general than decomposition by Carius ' technique or pyrolys is (see below).

A n a l y s i s of o r g a n o m e r c u r y c o m p o u n d s for mercury. In C a r i u s ' method, the organomercury compound is decomposed with fuming nitric acid (sp. gr . 1.52) in a sealed tube. If the sample contains no halogen, the contents are diluted with water and titrated with a 0.1N solution of ammonium thiocyanate in the presence of f e r r i c alum to a pale brown end-point (1 ml of 0.1N NH4CNS = O.010015 g of Hg). When the sample contains a halogen, titration with ammo-nium thiocyanate is not applicable. In this case the decomposed sample is diluted with water and the mercury determined g r a v i -metrical ly as the sulfide, as in the method described below.


A f t e r decomposition, the mercury can also be conveniently determined electrolyt ical ly or microelectro lyt ica l ly , whether or not the sample contains halogens.

A s impler and more convenient means for determining mercury in compounds from which m e r c u r y can be easi ly cleaved off, as in the addition products formed between mercur ic salts and unsaturated compounds, and in the aromatic derivatives of m e r c u r y , is offered by the Adams method.

A d a m s ' m e t h o d for the a n a l y s i s of o r g a n o m e r c u r y c o m p o u n d s for mercury [371. About 0.5 g of the organomercury compound is placed in a 200-ml round-bottom f lask fitted with a rubber bung carry ing a dropping funnel and a Peligot tube f i l led with water. From the funnel are added 5 ml of conc. HCl and the mixture is heated until a c lear solution is obtained (10-15 minutes). The water in the Peligot tube i s run in and water i s added up to 10 ml. Hydro-gen sulfide is passed through the solution until precipitation c e a s e s . The resulting mercur ic sulfide is f i l tered off through a weighed porcelain or g l a s s crucible, washed with water, alcohol and carbon disulfide, dried at I lO 0 C and weighed.

Both these methods are also applicable to the microanalytical determination of m e r c u r y .

E a r l i e r combustion methods (with calcium oxide) [1, 38] are un-suitable for the determination of Hg in organomercury compounds containing nitrogen or a halogen, particularly iodine or bromine. Two different combustion methods have therefore been devised.

If nitrogen is absent, the sample may be analysed by Boetius' method [39], based on combustion in oxygen: sulfur, chlorine and bromine are trapped on heated lead oxide and iodine on s i lvered porcelain chips. Alternatively, in Juracek's [40] semimicro variant, the combustion is carr ied out in oxygen with a platinum catalyst: chlorine and bromine are absorbed by anhydrous sodium carbonate, iodine by s i lver dispersed on magnesia and the m e r c u r y by gold. If nitrogen is present, the sample is heated in a current of CO2 in a tube containing lead ehromate, copper and s i lvered porcelain chips (Boetius [39]), or the combustion is c a r r i e d out in a current of oxygen, the latter is expelled with CO2, the m e r c u r y contaminated with its nitrate is passed through red-hot copper and the pure m e r c u r y finally absorbed on gold [41].

In a general method for determining mercury that does not depend on the presence of other elements [42], the sample is ignited under nitrogen and the decomposition products passed through a packing, heated to 750° C, which fully retains the acidic gases and is of the same nature as that used in the second method of Boetius. The m e r c u r y vapor condenses in the end of the combustion tube and is then driven over to a gold foil .

This and the other methods listed above are however being ousted by a s impler general method of pyrolys is , devised by Korshun,



Sheveleva and Gel'man [11], which also permits the determination of m e r c u r y by itself.

The same method is suitable for the simultaneous determination of m e r c u r y , halogens and sulfur in a manner that is more convenient than, for example, the simultaneous determination of these elements by the decomposition of organomercury compounds with metallic potassium in a bomb [43].

According to Hernler [44], it is possible to determine mercury and nitrogen simultaneously by the Dumas combustion method, trapping the mercury on gold.

Determination of mercury is mentioned in severa l reviews and books on organic analysis [27, 45-47].

The l i terature contains data on colorimetric [48, 49] and spec-t r o g r a p h ^ determination of organomercury compounds (phenyl-mercury acetate) [50], as well as on polarographic determination of certain c l a s s e s of organomercury compounds such as alkyl-m e r c u r i e s [51-56, 58], adducts formed between mercur ic salts and unsaturated systems [57, 59-61], a r y l m e r c u r i e s [56, 62-71] and the mercury derivatives of heterocycl ic compounds [72].

Kimura and Mil ler [73] have reported on the separation of the vapors of volatile organomercury compounds and metall ic mercury .

Kanazawa et al. [74] have determined the Rf values in the paper-chromatographic separation of some organomercury compounds.

Brodersen and Schlenker [75] resolved mixtures of compounds of the type RHgBr ( R = B r , CH3, C2H5, C3H7, C4H9, p-CH3OC6H4, p -BrC6H4) by paper chromatography with a developer containing NH4OH (see also [76]). Successful attempts separation was also achieved [75] gas-chromatographical ly on a s i l icone-oi l column at 190-220°C with a hydrogen c a r r i e r .

B e c k e r and Ehinger [77] have separated on paper and visualized with K B r complexes formed by dithizone with mercury salts , C6H5HgNO; and C6H5HgOCOCH3.

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Chem. Abstr . , 150, 10,613 (1956). 65. V. Voj i r , Chemicke Listy, 46, 129 (1952). 66. W. Z. Wuggatzer and J. M. C r o s s , J. A m . pharm. A s s . , 41,

80 (1952). 67. V. Voj i r , Colin czech. chem. Commun., 16, 488 (1951). 68. R. Benesch and R. E. Benesch, Arch. Biochem. Biophys.,

38, 425 (1952). 69. R. Benesch and R. E. Benesch, J. Am. chem. Soc., 73, 3391

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648 (1952).


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52, 12,649 (1958). 75. K. Brodersen and U. Schlenker, Z. analyt. Chem., 182, 421

(1961). 76. J. N. Bartlett and G. W. Curt is , Analyt. Chem., 34, 80 (1962). 77. A. B e c k e r and F. Ehinger, Z. analyt. Chem., 187, 110 (1962).

Author Index

Abderhalden, E. vi Adams, R. 309, 511 Ananchenko, S. N. 259 Angel, T . H, 17, 19

Bamberger E. 401 Barrett , A. W. 152 Baur, R. 81 Bayer, A. 401 Becker, A. 512 Belshinskii, S. V. 339 Biginelli1 P. 149, 204 Biilman. E. 189 Biltz, H. 152, 204, 206 Birckenbach, L. 466 Boedecker, F. 88 Boetius, M. 511 Borisov, A. E. 146, 149, 150, 204, 328,

340, 379, 406, 415 Bradley, D. C. 469 Brandt, G. A. R. 470 Brodersen, K. 512 Brown, R. E. 16 Buckton, G. B. 319

Calingaert 1 G. 298 Chamberlin, E. 46 Charm an, H. B. 305 Chatt, J. v Chiu, D. D. K. 192 Coates, G. E. vi, 287 Curtius, T . 468

Das Gupta, H. N. 13 Dennstedt, 507 Dessy, R. E. 306, 340, 342, 407 Dimroth, O. 57, 71, 87, 105, 107, 110 Dittmar, P. 43 Drehman, U. 25 Dupont, G. vi Duppa, B. F. 49, 399, 507

Eberhartinger, R. 115 Ehinger, F . 512 Emeleus, H. J. 12, 470

Falkov, M. 507 Fedorowa, A. M. 262 Fischer , E. 239, 477, 490 FitzGibbon, M. 62 Foss 1 V. L . 157 Frankland, E. 11, 41, 45, 49, 399, 404,

507 Freidlina, R. Kh. 145, 149

Garzuly, R. vi Gaudemar, M. 41 Gel'man, N. E. 507, 512 Gilman, H. 16, 361, 390, 391 Giral , F. 46 Glushkova, V. P. 265, 363 Goddard, A. E. v Goddard, D. v Gould, V. L. 16, 17 Grdenic, D. 419 Grignard, V. v Grim, S. O. 239 Grosse, A. v Griittner, G. 16, 289, 404

Hantzsch, A. 66, 324, 468 Haszeldine, R. N. 12, 470 Hein, F . 309 Hellerman, 238 Hernler, F . 512 Hilpert, S. 16, 43, 289, 391, 404 Hinkel, L. E. 17, 19 Hofmann, K. A. 57, 62, 63, 142, 160, 206,

339, 507 Holmberg, B. 476 Houben, J. vi Hughes, E. D. 305 Hurd, D. T . v

516

AUTHOR INDEX 517

Ingold, C. 305 Ioffe, S. T . v Irwin, F. J. 246 Ivanova, N. L . 157

Jackson, C. L . 486 Jacobi, K. R. 16 Jenkins, W. J. 149 Juracek, M. 511

Kanazawa, J, 512 Karasch, M. S. 98, 259, 261, 289, 292,

340, 342, 365, 486 Kimura, I. 512 KIapproth, W. J. 78 Klarmann-Bloomfield, E. vi Klebanskii, A. L. 204 Knunyants, I. L. 404 Kobe, K. A. 321 Kocheshkov, K. A. v, 265, 363, 368, 384

390, 396 Kochetkov, N. K. 158 Kolb, H. 466 Korshak, V. V. 204 Korshun, M. O. 507, 511 Koton, M. M. 290, 297, 298, 343 Kraus, C. A. 287 Krause, E. v Kravtsov, D. N, 298 Kucherov, M. G. 152, 203

Leuck, G. J. 90 Levina, R, Ya. 211 Lewis, H. F. 46 Lewis, R. N. v Liebig, J. 506 Logan, T . Y. 292 Lohr, P. 391 Loquin, E. vi Loseva, A. S. 240 Loudon, J. D. 257 Lovtsova, A. N. 295 Lucas, H. J. 147, 148 Lutsenko, I. F . 64, 147, 155, 157, 180, 259

McCleland, N. P. 115 McClure, F . T . 246 McCutchan, R. T . 321 McNelley, K. H. 172 Makarova, L . G. v, 246, 257 Manchot, W. 152, 464 Marker, C. 481 Marvel , C. S. 16, 17, 146 Maschmann, E. 89, 98 Maynard, I. L. 12 Michaelis, A. 46, 52, 361, 371 Mil ler, V. L . 512 Moore, L . O. 361 Mumm, O. 152, 204, 206

Myddleton, W. W. 152

Nad', M. M. 368 Nesmeyanov, A. N. v, 64, 145, 146, 147,

149, 150, 154, 155, 158, 180, 204, 228, 240, 246, 257, 259, 292, 298, 303, 304, 306, 328, 340, 379, 384, 396, 406, 415

Newman, - . 238 Newton Friend, - . v Nogina, O. V. 149

Ogata, Y. 78, 104, 106 Ol'dekop, Yu. A. 276 Otto, R. 46

Panov, E. M. 265 Paolini, V. 8 8 , 1 1 1 Peaks, R. W. Pesci , L . 57, 105, 260 Petrovich, P. I. 77 Pfeiffer, P. 16, 146 Prilezhaeva, E. N. 475, 476

Raiziss, G. W. 98, 507 Razuvaev, G. A. 276, 295, 381, 411, 415 Renaud, P. 22 Reutov, O. A. 148, 230, 240, 295, 303, 304,

305, 306, 344, 405 Reynolds, G. F. 26 Robs on, J. H, 350 Rochow, E. G. v Rodionow, W. M. 262 Roman, F. L . 309 Rumpf, P. 17 Rupp, E. 88

Sachs, G. 115 Sakurai, I. 11 Sand, J. 142, 160, 172, 347 Sandin, R. B. 246 Schlenk. W. vi Schlenker, U. 512 Schoeller, W. 153, 160, 202 Schorygin, P. P. 388 Schmidt, J. v Schrauth, W. 152, 160, 202 Seyferth, D. 239, 295 Sheveleva, N. S. 507, 512 Sheverdina, N. I. v Shilov, E. A. 149 Slotta, K. H. 16, 17 Smirnov-Zamkov, I. V. 149 Sobatzki, R. J. 316 Sokolik, R. A. v Sokolov, V. 1. 148 Sowa, F. J. 88 Speier, J. L. 21 Sperry, W. N. 309

518 AUTHOR INDEX

Staveley, F . W. 259 Swaney, M. W. 115

Titov, V. D. 204 Tray lor , T . G. 340 Tsuchida, M. 78, 104, 106

Ukai, T . 88 Usubakunov, M. 339

Vecchiotti, L . 51 Verdino, A. 510 Vereshchagina, N. I, 180

Volhard, J. 110

Wagler, K. 309 Weil, V. vi Westheimer, F . H. 78 Whitmore, F. C. v, 90, 316 Wilson, S. H. 115 Winstein, S. 147, 148, 340, 407 Wittig, G. 30, 51 Wright, G. F. 146, 148, 172, 192, 304, 350

Zamyatina, V. A. 204 Zeiss , H. v

Subject Index Numbers in i tal ics r e f e r to pages on which a preparation i s described in detail.

p-Acetaminophenylmercury acetate 96,101 Acetanilide, reaction with mercur ic chloride

488 Acetone, e lectrolys is 285 bis-y-Acetopropylmercury 311 1 - Acetoxy - 2 - acetoxymercuricyclohexane

170 /3-Acetoxyethylmercury chloride 163 Acetoxymercuriacetaldehyde monoethyl

acetal acetate 184 m-Acetoxymercuri -p -aminobenzoic acid,

ethyl ester IOS 1-Acetoxymercuribenzanthrone 105 3-Acetoxymercuribenzidine 101 2-Acetoxymercuribiphenylene, reaction with

chlorine 355 4-Acetoxymercuri-2-bromoanil ine 3SO 2-Acetoxymercuricyclohexanol 170 1 - (Acetoxymercuri)cyclohex-1 -ene 24,1 2-Acetoxymercuri-1,4-dichlorobenzene 80 2-Acetoxymercuribiphenylene 75, 79 a -Acetoxymercuri-/3,2-dimethoxydihydro-

cinnamic acid 197 Acetoxymercuri formic acid, ethyl es ter S03

methyl ester SOS a-Acetoxymercuri-^S-methoxyethane 162 9 - Acetoxymercuri - 10 - methoxy palmitic

acid 190 a -Acetoxymercur i - /3 -methoxy- /3 -phenyl-

propiophenone 185 3-Acetoxymercuri-2-methoxysulfolan 200 1-Acetoxymercurimethyl-1,2-dihydrobenzo-

furan 179 2,6-bi s - (Acetoxymercurimethyl)- p - oxathi-

ane 353 bis- l-Acetoxymercurinaphthyl-2-amine 95 p-Acetoxymercur i -m-ni tramline 100 2,4 - bis - Acetoxymercur i -3-ni tro- l -naph-

thylamine 101 2-Acetoxymercuri-3-nitro-l-naphthylamine

101 4-Acetoxymercuri-6-nitro-l-naphthylamine

101 6-Acetoxymercuri-2-nitrophenol 82, 84 4-Acetoxymercuri-2-nitrophenol 82, 84 2-Acetoxymercuriphenylglycine, ethyl ester

101 a-Acetoxymercuri- /3-phenyl-/3- methoxv-

propionic acid, methyl ester 1 9 4 Acetoxymercuripropyl acetate 189 8-Acetoxymercuripurine 120 TO-Acetoxymercurisulfanilamide 102 wj-Acetoxyphenylmercury chloride 4&8 3 -Acetylamino-4- hydroxy-5- hydroxymer-

curiphenylarsonic acid 102 Acetylferrocene 376 Acetylguanine, chloromercuri derivative

492 Acetylpropionylmethane 206 Alkanolmercury salts, /3 -elimination of

olefins 144 Alkyldichlorophosphines 369 Alkylmercury &>-mercaptoundecanate 422 Al ly lmercury chloride 41

iodide 12, 41, 319 Allylphenylmercury 18, 403 Aluminum isopropoxide 456 Amides of aromatic acids, mercury deriva-

tives 488 2- Amino-5-chlorophenylmercury acetate

100 p-Aminophenylmercury acetate 99 p-Aminophenylmercury acetate, symme-

trization 320 o-Aminophenylmercury chloride 100 Amylsodium 387 Aniline, reaction with mercuric chloride

486 p-Anisy lmercury acetate 87

chloride 266 P-Anisyithaliium di-isobutyrate 364 p-Anisylthallium di-isobutyrate, reaction

with m e r c u r i c chloride 265 Arylboronic acids 249 Aryldiazonium chloride, double salt with

mercuric chloride 230 Arylhydrazine, reactions with mercury salts

239

Benzene, hydroxy nitration 72 Benzene, kinetics of mercuration 71 3,4-Benzodiphenylenemercury 35 Benzophenone 376 6 - Benzoyl,2,3,4,5- tetra- acety l-dl-D-glu-

cose 478

519


Benzylamine, reaction with mercur ic chlo-ride 484

Benzylchloromethylmercury 294 Benzylmercury bromide 41

double salt with mercur ic chloride 25 labelled with Hg2O3 303 reaction with DI I 2 and I 2 351

Benzylmercury chloride 21 demercuration 346 Teact ionwithN 2 O 3 402 symmetrization with copper 310

Benzylmercury hydroxide 420 iodide, symmetrization 313 nitrate ^HO

oxidation with mercuric nitrate 350 Benzylphenylmercury 290 Benzylsodium 387 Biferrocenyl 386 Biphenylene 385, 386, 386 bis-Biphenylenylethylene 380 0-Biphenylylmercury chloride 311, Bromoacetaldehyde, diethyl acetal 356 Bromoferrocene 358 5-Bromo-2- fury lmercury chloride 263 Bromomercuriacet ic acid, methylester 186 Bromomercuriacetone, reaction with keten

186 OT-Bromomercuribenzoic acid, methy les ter

329 3~Bromomercuri - 3 - benzylcamphor, ex-

change with 203Hg 407 3-Bromomercuricamphor 406

exchange with 203Hg 407 symmetrization 304, 314, 326

a - B r o m o m e r c u r i c y clohexanone, exchange with 203Hg 407

2-Bromomercur i - 3-phenylpropionic acid 353

a-Bromomercuriphenylacetic acid, ethyl ester, symmetrization 303, 326

reactions with acetyl chloride 378 reactions with Cd I and I2 351

a-Bromomercuri-/3-phenyl-/3-methoxyhy-dracryl ic acid, Z-menthyl ester 146

Bromomercuripropylene glycol 175 a - Bromomercuristi lbene, symmetrization

318 Bromomethylmercury bromide, reaction

with alkalis 349 1 - B r o m o - o c t - l - y n e 355 m-Bromophenylmercury chloride 235 1- trans -2'-Bromovinyl-2,2'-bromoethynyl-

benzene 355 bis~(l- trans -2 '-Bromovinyl-2-ethynyl-2)

mercury 355 Butadiene 172 n-Butylcarbomethoxymercury 298 n-Butylmercury bromide 20

chloride symmetrization 314 s-Butylmercury bromide 20, 304

electrolysis 288 symmetrization 304, 311 tartrate and ^-phenylglycollate, resolution

into optical i somers 328

t -Buty lmercury chloride 20

Camphor-10-mercury chloride 255, 313 Camphor, monomercurated 65 4-Camphylmercury iodide 353 P-Carbethoxyphenylmercury chloride 233,

235 bis-Carbomethoxymercury 326 Carbomethoxymercury chloride 298, 326 Carbomethoxy - p - methoxyphenylmercury

298 Carbon monoxide, reaction with mercury

salts 153, 202 N- (/3-Carboxypropionyl)-N - (2-methoxy-3-

halogenomercuripropyl)urea 199 n-Cetylmercury 20 3-Chlorocamphor- 10-mercury chloride 255 2-Chloro-3-chloromercuripropen-2-ol 207 2-Chlorodiphenylene 355 l - ( l ' -ChIoroferrocenyl)mercury chloride

251 1,2-Chloroiodoethylene 356,356 1 - C h l o r o - l ' - i o d o f e r r o c e n e 358 Chloromercuriacetic acid 186

methyl ester 309 Chloromercuriacetone 180, 323, 377, 4,57 Chloromercuriacetaldehyde 180, 181, 356,

373, 377, 456 Chloromercurianiline 4,86 1,8-di-Chloromercurianthraquinone 257 o-bis-Chloromercuribenzene 328 m-Chloromercuribenzoic acid 4^9 p-Chloromercuribenzoic acid e s t e r s 310 0-Chloromercuribenzoic acid, methylester

108 o -Chloromercuribenzophenone 105 o, o '-bis-Chloromercuribiphenyl 254 l ,4-bis-Chloromercuri-2,3-butandiol 354 2-Chloromercuricamphane 23 a -Chloromercuri-/?-chloroacryl ic acid 209 2 - C h l o r o m e r c u r i - p - c r e s o l 83 3-Chloromercuricyclohexan-1,4-diol 178 Qiloromercuricyclopentadienyltricarbonyl-

manganese 121, 257, 321, 358 2-Chloromercuridibenzofuran 257 0 -Chloromercuridiphenyl sulfone 94 N-(/3-Chloromercuriethyl)piperidine 163 1 - (Chloromer curi)ethyltrimethy lsilane 21 Chloromercuriferrocene 257, 257, 309, 388 Chloromercurifumaric acid, methyl ester

210 a - l -Chloromercuri-2-hydroxycyclohexane

457 a-Chloromercuri- isobutyr ic acid, methyl

ester 188 4 - Chloromercuri - 5 - methoxy- 1 ,2-dicar-

bamylhexahydropyridazine 201 Chloromercurimethoxyphenylbutene 173 1-Chloromercuri-5-methoxytr icyclene 1 7 4 Chloromercurimethylbenzylcarbinol 171 1 - Chloromercurimethyl-1,2-dihydrobenzo-

furan 179, 309 2-Chloromercurimethyltetrahydrofuran 17 5

SUBJECT INDEX 521

4-Chloromercuri-2-nitrotoluene 322 Chloromercuriphenylacetaldehyde 181 4-Chloromereuri -1 -phenylpyrazole 119 1-Chloromereuripropanol 147 4-Chloromercuriresorcinol 85 3 - Chloromercurisal icyl ic acid, methyl

ester 89 3-Chloromercuri-2,5-thioxene 308 a-Chloromercurist i lbene 309 m-Chloromereuritoluene 1/.59 p-Chloromercuritriphenylcarbinol 234 Chloromethylmercury chloride 239 P-Chlorophenylbenzylmercury 293 p-Chlorophenylmercury chloride 233, 256,

310 2-amino-5- Chlorophenylmercury acetate

100 p-Chlorophenylphenylmercury 293 p-Chlorophenylthallium di-isobutyrate 364 bis - (1 - C h l o r o - 1,2,2,2- tetraf luoroethyl)-

mercury 399 trans -/3-Chlorovinyl iodide chloride 375 trans -/3-Chloroviny lmercury chloride 204,

251, 266, 323, 326, 375, 416 cis-0-Chlorovinylmercury chloride 204,

266, 323, 329, 355, 356 Cinnamylmercury bromide 1 3 Copper powder, preparation for the diazo

method 231 Crotylmercury acetate, solvolysis 346 trans -Croty lmercury bromide 22 Cyclohexane-1/3,4a-diol 382 Cyclohexylmercury acetate 345, 346

bromide 22, 23, 25 chloride 23 iodide 50 nitrate 350

Cyclomercuripentamethylene 309 Cyclopentadienylmercury chloride 65, 323,

400 bis-Cyclopentadienylmercury, reaction with

maleic anhydride 65 Cyclopentadienylthallium 266 Cyclopentamethylenemercury 35

Demercuration 344 Desoxymercuration 146, 348 Diacetonylmercury 183, 323 1.3-Diacetoxy - 2 - chloromercuribut-2-ene

208 2.4-Diacetoxymercurianiline 100 m-Diacetoxymercuribenzene 402 o -Diacetoxymercuribenzene 78 Diacetoxymercurichloroacetic acid, ethyl

ester 187 reaction with alkalis 349

Diacetoxymercuridimethyloxybutane 173 9,10 - Diacetoxymercuriketoundecenic acid,

ethyl ester 210 Diacetoxymercurimalonic acid, ethyl ester

69 3,4-Di(acetoxymercuri)-2-methyl-5-ethyl-

thiophene 118

2,6-Di(acetoxymercurimethyl)-l,4-thioxane 180

2,4-Diacetoxymercuri-l-naphthylamine 100 4,6-Diacetoxymercuri-2-nitrophenol 84 Di-o - acetoxyphenylthallium bromide 363 Dialkylmercury 388 2,3 - Diaikoxy - 1 , 4 - diacetoxymercuributane

172 Dialkoxyphosphinylmercury 493 Diallylmereury 28, 312 Di-p-amino-o-bromophenylmercury 320 Di-p-aminophenylmercury 320 Di-n-amylmercury 49 Di- t -amylmercury 26

oxidation 338 Dianisylmercury 52, 53, 406 a, a -Dianthraquinonylmercury 237

Diarylchlorophosphines 370 Diaryl-Iead diacetate 368 Diarylmercury, reactions with bromosuc-

cinimide 416 reactions with nitrogen oxides 401 reactions with nitrosyl bromide 401

Diaryl selenides 273 Diazoaminobenzene, N-mercury salt 490 Diazomethane, reactions with mercury salts

238 3-Dibenzofurylmercury chloride 24 Dibenzyimercury 18, 27, 32, 35. 310, 313

oxidation 337 pyrolysis 410 reactions with nitrogen oxides 402

chlorides of Fe, Co, Cu 414 stannous chloride 397

Dibenzyltin chloride 397 Di-o-biphenylmercury 318 23-Dibromo-5-chloromercurithiophene 264 1,1-Dibromocyclopropane 366 1 ,1 ' -Dibromoferrocene 358 1,4-Dibromomercuribenzene 23 Dibromomercuridiethyl ether 313 Di-p-bromophenylmercury 236, 311 1,1-Dibromotetrachlorocyclopropane 365 Dibutenylmercury 29 Di-n-butylmercury 26, 31, 35, 48, 314

reactions with GeI2 and I2 394 nitrogen oxides 402 photolysis 411

Di-S-butylmercury 26, 285, 286 Di-t-butylmercury 26 Di-p-s-buty lphenylmercury 18 Di-a-camphenylonylmercury 321 Di-o-ehlorobenzylmercury 27 1,1-Dichlorocyclopropane 366 2,3-Dichloro-4,5-dichloromercurithiophene

263 Dichloromercuriacetic acid, ethyl ester 187 1.3-Dichloromercuribenzene 256 2,2'-Dichloromercuribiphenyl 317 1.4-Dichloromercuributane 313 Dichloromercuricyclopentadienyltricarbon-

ylmanganese 121 l , l ' - D i c h l o r o m e r c u r i f e r r o c e n e 257, 317 2,6-Dichloromercurimethyldioxan 179


2,6-Dichloromercurimethylmorpholine 1 8 4 4,6-Dichloromercuriresorcinol 85 2,5-Dichloromercurithiophene 317, 319 Di-jp -chlorophenylmercury 29, 267, 310 1,1 -Dichloro-2-trimethylsi lylcyclopropane

367 Di-/3-chlorovlnylboron chloride 361 Di-/3-chlorovinyliodonium chloride 375 Di-S-chlorovinylmercury 268, 323

exchange with 203 Hg 407 pyrolysis 4 1 0 reactions with Cl 2 355

HgCl2 329 SnCl2 396 TlCl 3 155

trans, trans -Di-/3-chlorovinylmercury, conversion into cis 1^16

Di- cis -/3-chlorovinylthallium 268 trans, trans -Di-/3-chlorovinyltindichlo-

ride 397

reaction with mercur ic chloride 266 Dicyclohexenylmercury 33 Dicyclohexylmercury 29 50, 286

oxidation 337 photolysis 412 pyrolysis 410

Dicyclopentadienylmercury 4,0, 65, 71, 266 reaction with bromine 357

Dicyclopentenylmercury 33, 33, 286 ' Dicyclopropylmercury 18, 29, 379, 457 Di-(3-dimethylamino-4-methylphenyl)mer-

cury 53 Di-p-dimethylaminophenylmercury 33, 310 Di- o-diphenylmercury 254 bis-(Diethoxyphosphinyl)mercury 494 Diethoxyphosphinylmercury chloride 494 Diethyldiphenyltin 399 Diethyl ether, mercury derivatives 162 Diethylmagnesium 390 Diethylmercury, photolysis 411

preparation 48 by e lectro lys is 43 through the organometallic derivatives

of Al 42; B 253, 286; Mg 25, 31; Zn 41

reactions with Al 391 allyl iodide 380 arsenobenzene 384 A s C l 3 371 Be 389 benzoyl peroxide 379 Bi 399 Cd 391 Ga 393 iodoform 378 Li 387 mercuric succinate 329 Mg 390 Na 388 pentaethyldisilane 426, 483 tr i - o-thymotide 426 triethylgermane 482 triethylsilane 426, 483 U 400

Diethylzinc 390 Diferrocenyl disulfide 373 Diferrocenylmercury 309, 314

pyrolysis 410 reactions with butyl-lithium 388, 405

C C l 4 379 CuCl 414 SeBr4 373 SnCl2 384 triphenylchloromethane 376

Diferrocenylselenium 373 Di-ra-fluorophenylmercury 29 D i - a - f u r y l m e r c u r y 314,320 Dihalogenocarbenes, introduced in C-Hg

bonds 295, 365 Di-n-heptylmercury 27 Dihexadecylmercury 18 Di-n-hexylmercury 27 Di - exo -3 hydroxy- e»o-2-norbornylmer-

cury 315 Di-m-hydroxyphenylmercury 320 l , l ' -Di- iodoferrocene 358 2.3-Di-(iodomercurimethyl)-l,4-dioxan 173 Di-p-iodophenylmercury 236 Di-isoamylmercury 31, 49 Di-isobutylmercury Di-isoheptylmercury 404 Di-isopropylmercury 26, 42, 48, 285, 286

oxidation 337 pyrolysis 410 reaction with CHCl3 and C C l 4 290

o-Dilithiobenzene 387 Dimenthylmercury 286 1,6-Dimercuracyclodecane 49, 313 Dimercurimalonic acid, internal salt 69 Dimesitylmercury 50 bis - (Dimethoxyphosphinyl)mercury 494 Di-( l -methyl - 2 - acetoxy- 1 - propen - 1 - y l )

mercury 268, 363 bis-p-Dimethylaminophenylmercury 53 p - Dimethylaminophenylmercury acetate

100 chloride 34

symmetrization 310 Dimethylberyllium 389 Dimethylcyclohexylmercury 286 Dimethyl diselenide 481 Di-5-methylhexyl-2-mercury 27 Dimethylmercury, reactions with Al 391

Alkyl-Iithium 387 Be 389 Cd 390 cyanogen iodide 380 dimethylmagnesium 405 Ga 393 In 393 Mg 390 nitrogen oxides 401 Sb 399 SbCl3 372 Zn 389

bis-(Di -/3- methyl -/3- phenylethyl)mercury 27

2.4-Dimethylphenylmercury 79

SUBJECT INDEX 523

Di-^-methyl-^-phenylpropyimercury 18 Di-,S-naphthylmercury 50

reactions with mercuric chloride 329 Di-a-naphthylmercury 50,235, 311

reactions with T e 400 Di- a-naphthyltellurium 400 Dineopentylmercury 27 Di-o-nitrophenylmercury 315 Di-3-nitro-4-tolylmercury 322 Di-n-nonylmercury 27 Dioctadecylmercury 18 Di-n-octylmercury 27, 49 Di-s-octy lmercury 27 Di- (oct - l -ynyl ) -mercury 28 1,7-Dioxa-4,10-dimercuracyclododecane

313

Dipentafluorophenyimercury 314 Dipentamethylphenyi 50 Diperfluoroethylmercury 411 Diperfluoroisopropylmercury 410 Diperfluoromethyl diselenide 481 Diphenylantimony chloride 372 Diphenylberyllium 390 Diphenylcadmium 391 Diphenylchloroarsine 371 Diphenylchlorophosphine 370 Diphenyldiazomethane, reaction with m e r -

curic chloride 238 Di-/3-phenylethylmercury 18, 28 Diphenylindium chloride 362 Diphenyliodonium chloride 246, 374 Diphenyl-Iead diacetate 267 Diphenylmercury 50, 53

exchange with 203 Hg 406 photolysis 411 preparation 13, 50, 53, 308,310,321,\3S5

from phenyldiazonium 236 from phenylhydrazine 240 through organometallic derivatives of

Al 42; Li 35; Mg 17, 30, 31; Sn 267 pyrolysis 410 reactions with Al 391

BCl 3 362 Be 389 Bi 399 B i B r 3 372 carbon disulfide 424 C C l 4 378,415 Cd 391 CHI3 378 ethyl-lithium 388 Ga 393 GeI2 394 In 393 LiAlH4 382, 392 metal chlorides 373, 374, 396, 414 nitrogen oxides 401 Pd 384 S 399 SbCl , 372 Se 399 Sn 344, 405 T l C l 3 363 Zn 390

2,5-Diphenyl-4-methylfuryl-3-mercury 208 Di-y-phenylpropylmercury 18, 27 Diphenylselenium 400 Diphenylthallium chloride 363 2,4 -DiphenylthienylphenyImercury 296 Diphenylzinc 390 Dipropenylmercury 32, 155, 290 trans, irans-Dipropenylmercury, reaction

with T l B r 3 , 363 trans, trans -Dipropenylthallium bromide

363 Di - n - propoxyphosphinylmercury halides

494 Dipropylene oxide dimercury sulfate 175 Di-n-propylmercury, 18, 25, 42, 48, 316

photolysis 412 pyrolysis 410 reactions with Al 391

Be 389 T l C l 3 362 Zn 390

Di-n-propylphenylmercury 50 Di-n-propyl phosphonate 4 9 3 Dipseudocumylmercury 50 Di-3-pyrenylmercury 35 Di-a-st i lbenylmercury 33 Di-ii>-styrylmercury 33 Ditetradecylmercury 18 Di-a-thienylmercury 318 Di-p-tolylmercuricrotonaldehyde 297 Ditolylmercury 33, 50, 252, 314, 318, 325 Di- 0 - toly lmercury 50, 236

reaction with sulfur 400 bis-(Ditrifluoromethylamino)mercury 484 Di-(trimethylsilyl)methylmercury 24 Di-n-undecylmercury 27 Divinylmercury 19, 28, 312, 313

photolysis 411 pyrolysis 410 reactions with BBr 3 361

B f 3 361 gallium 392 LiAlH 4 391 methylene iodide 457

Di-ra-xylylmercury 50 D i - p - x y l y l m e r c u r y 50 I-Dodecylmercury chloride 255 n-Dodecylmercury hydroxide 21

Ethanoxyhexamercarbide 68 Ethanolmercury bromide 143, 145, 161 Ethanolmercury chloride 451 /J-Ethoxyethylthiomercury chloride 476 p-Ethoxyphenylmercury bromide 25 p-Ethoxyphenylmercury chloride 232 Ethylaminomercury nitrate 484 Ethylbutylmercury 290 3-Ethyl-3-chloromercuripentan-2-one 260 Ethylmercaptomercury chloride 476 Ethylmercurithiosalicylic acid 423 Ethylmercury alkoxides 421

bromide 20 chloride 23, 41, 42,


Ethylmercury alkoxides (continued) iodide 25, 280 mercaptides 421 phenoxides 421 phosphate 421 succinate 316, 329 thiophenoxides 421

bis-Ethylmercury sulfide 420 Ethyl- 2,4,6- trinitrophenylmercury 292

Ferrocene 400 FerrocenyI-Iithium 383 F e r r o c e n y l m e r c u r y c h l o r i d e 261, 314, 321,

358, 405 p-Fluorophenylmercury acetate 76 4-Fluorylmercury chloride 357 2-Formylphenylmercury 250 Furylmercury chloride 262, 263, 267, 320

Hammett's equation 72, 74, 87, 303, 342

Heptafluoro-2-iodopropane 357 n-Heptylmercury 20 Hexabromocyclopentadiene 357 Hexachlorocyclopropane 365 n-Hexadienylmercury chloride 21 Hexaethyldistannane 398 2 , 2 ' , 4 , 4 ' , 6 , 6 ' - Hexanitrodiphenylmercury

261 n-Hexylmercury bromide 20, 24 4- Hydroxy • 5 - chloromercuri - 3,6 - endo -

hexahydrophthalic acid, dimethyl ester 193, 354

2a-Hydroxybicyclo-(2,2, l)-heptan-6,a-car-boxylic acid, lactone 382

4-Hydroxycyclohexylmercury 350 /3-Hydroxyethylmercury iodide, benzoyla-

tion 456 ,8-Hydroxyethyl-p-tolylmercury 293 p-Hydroxymercurianthranilic acid, internal

salts 102 o-Hydroxymercuribenzoic acid 261 p-Hydroxymercuribenzoic acid, internal

salt 107 4-Hydroxymercuri-2,7 -dibromofluorescein

92 4-Hydroxymercuri- 3 -hydroxy-2-naphthoic

acid, internal salt 90 2-Hydroxymercuri-isophthalic acid, inter-

nal salt 261 8-Hydroxymercuri-1-naphthoic acid 108 Hydroxymercuration 165 o-Hydroxymercuriphenol, internal phen-

oxide 83 Hydroxymercuripropionic acid, internal

salt 70 o-Hydroxymercurisal icy l ic acid 88 3-Hydroxymercurisal icyl ic acid, anhydride

88 2-Hydroxymercuriterephthalic acid, inter-

nal anhydride 108 5-HydroxymercurivaniUin 88

2-Hydroxy-l-naphthylmercury acetate 83, RIL

exo - cis -3-Hydroxy-2-norbornylmercury chloride, symmetrization 315

5-Hydroxypentylmercury chloride 21 o -Hydroxyphenylmercurisuccinimide 424 m-Hydroxyphenylmercury chloride 250,

320, 458 p-Hydroxyphenylmercury chloride 83, 233 3 - Hydroxy- 2 , 2 , 3 - trimethylbutylmercury

211

Imidodihydroxamic acid 401 Indenylmercury bromide 34 Iodocyclopentadienyltricarbonylm anganese

358 Iodoferrocene 358 Iodomercuriacetone 70 2-Iodomercuriethyl benzoate 456 2,3-bis-Iodomercurimethyl-l ,4-dioxan 173 bis-lodomethylmercury 238, 458 bis -o -Iodophenylmercury 327, 410, 416 Iodonium compounds 246 o -Iodophenylmercury iodide 234, 327, 416 Isatin-/?-hydrazone 468 Isatin, mercury derivative 491 Isobutyl acetoacetate 378 Isobutylmercury chloride 25 Isopropenyl acetate 377 Isopropenylmercury bromide 32 Isopropylmercury bromide 25, 25, 42

Ketones, electrolytic reduction on Hganode 286

Kharasch's s e r i e s 340

Lewisite I (/3-chlorovinyldichloroarsine) 371

o-Lithiobiphenyl 387 Lithium aluminum tetravinylate 392

Malachite Green, mercurated 103 Mandelaldehyde, diethyl mercaptal 4 7 4 Mercaptals of sugars, splitting with m e r -

curic chloride 480 Mercaptomercury chloride 470 Mercarbie reactions with S 2 C l 2 372 Mercuracetamide 70, 487 Mercuracyclamides 487 Mercuricycloheptane 49 Mercurating agents 59

diphenylmercury 297 di-p-toly lmercury 297 mercuracetamide 60, 81 mercuric chloride 59, 61, 82 mercuric nitrate 59, 61, 64, 70, 71, 74 mercuric oxide 61, 74 mercur ic perchlorate 59, 72 mercur ic sulfate 59 mercurous cyanide 59, 61

SUBJECT INDEX 525

Mereurating agents (continued) mercury di- isobutyrate 75 mercury hydroxide cyanide 84 mercury laurate 76 mercury monochloroacetate 75 mercury myr is tate 74 mercury sal t of trinitromethane 72, 74,

87, 162

mercury salts of carboxylic acids 60 pentachlorophenoxymercury acetate 74

Mercuration of, acenaphthene 75 acetaldehyde 63, 297 acetamide 63 acetanilide 1 0 1 p-acetanisidine 96 acetic acid 62 acetic anhydride 63 acetoacetic acid 60 p-acetobenzoic acid 67 acetone 64, 70 acetophenone 64, 66, 69, 296 p-acetophenyiarsonic acid 67 acetylacetone 61 2-acetylaminopyridine 116 acetylanthranilic acid, methyl es ter 98 acetylenes 61, 68, 396 acetylenic ethers 61 acetylenyldivinyl 61 acetyl-a-naphthylamine 96 acety lsa l icy l ic acid 88 acridine 117, 296 m-acylaminobenzoic acids 98 alkylanilines 94 alkylbenzenes 74

5-alkyl-2,4-dihydroxybenzoic acids 89 alkylf luoresceins 91 2-alky lfurans 109 alkylphenols 82 alkyiselenophenes 112 alkylthiophenes 112 allyl alcohol 63 allylmalonic acid 61 amines, intermediate products 98 V - aminoacetophenone 97 p-aminobenzoic acid, ethyl es ter 102 p-aminobenzosulfamide 98 2-aminobiphenyls 94 2-aminofluorene 95 aminohydroxyarylarsonic acids 89 p-aminohydroxyphenylsulfonic acid 98 aminophenols 96 77i-aminophenyltrimethylammonium ace-

tate 95 2-aminopyridine 116 anethole 84 aniline 94, 99 anisole 86, 87 anthranilic acid 97, 102 anthraquinone 105 1-anthraquinonesulfonic acid 105

.pyrine 113 aromatic ef fects of substituents s e l e c -

tivity 58, 59 aromatic alcohols 93

arsonic acid, aromatic 105 arylacetylenes 61 2- ary lamino-4-methyl-5- carbethoxythi-

azole 101 2-arylaminothiazoles 95 aryl ethers of glycols 86 aryloxyacetic acid 86 aryloxypropionic acid 86 l - a r y l - 5 - p y r a z o l o n e s 113 3-arylsydnones 115 arylthiourea 96 arylurea 96 aurintricarboxylic acid 91 azoxybenzene 99 azulene 75 benzalacetone 297 benzalacetophenone 297 benzaldehyde 297 benzaurin 90 benzene 71, 74, 78, 79 benzenesulfonic acid 107 benzidine 95, 101 benzo-l ,4-dithiacyclohexa-2,5-diene 115 benzofurans 109 benzoic acid 105, 106, 107 benzonitrile 106 benzophenone 104, 105 N-benzylacetamide 99 benzyl alcohol 93 benzylphenols 82 biphenyl 75 biphenylene 75, 79 p-bromo-m-aminoacetophenone 97 bromobenzene 77 p-bromodimethylaniline 95 5-bromo-2-furancarboxyl ic acid, methyl

es ter 109 1 - b r o m o - l ' - i o d o f e r r o c e n e 358 /S-bromonaphthalene 77 p-bromo-rrt-nitroacetophenone 66 3 - brom 0-2,4,6- trimethylpheny 1 acety 1 ene

61 1 -trans -2-bromovinyl-2-ethynylbenzene

61, 68 butanol 63 butylacetylene 61 s-butylbenzene 74 t-butylbenzene 74 5-n-butyl-2,6-dihydroxybenzoic acid 89 p-t-butylphenol 82 butyraldehyde 297 camphor 65 camphorcarboxylic acid 65 cane sugar 63 carbazole 113 2-carbethoxy - 2 -methyl -1-ethynylcyc lo-

hexylcarbinol 61 carboxylic acids, aromatic 106 4-carboxyphenylarsonic acid 107 carvacrol 82, 85 cellulose 63 chloresterol 62 p-chloroacetophenone 66 p-chloroanil ine 100


Mercurat ion of (continued) chlorobenzene 75 o - c h l o r o b e n z o i c acid 106 chlorophenols 82 4 - c h l o r o r e s o r c i n o l 85 A2-Chromene 1 1 5 coumarin 90 p - c r e s o l 83, 85 cyanacetamide 61 cyanoacet ic acid 296 cyanopropionic acid 60 c y c l o h e p t a t r i e n - l - o l - 2 - o n e 66 cyclohexylphenols 82 cyclopentadiene 65, 71, 295 cyclopentadienyltr icarbonylmanganese

IZl cyclopent adienyltri carbonylrhenium 121 cyclopentanone 64 p - c y m e n e 74 decahydronaphthalene 61 d e c - trans - 3 - e n - l - y n e 61 3,5 - diacetylamino - 4 - hydroxyphenylar-

sonic acid 98 diacetylenic alcohol 61 diazoacet ic acid 60, 70 dibenzoylmethane 297 p-dibromobenzene 77 2 ,7-dibromof luoresce in 92 dibromophenyl ether 85 p-dichlorobenzene 77, 80 cis-dichloroethylene 61 d i - o - c r e s o l 85 diethyl terephthalate 108 2,5-diethylthiophene 111 4 , 4 - d i f l u o r o - 2 - b u t e n - l - y n e 61 2.4-dihydroxybenzaldehyde 87 o, o',p, p ' -dihydroxybiphenyl 85 4,4'-dihydroxydiphenyl sulfide 94 2,7-dihydroxyf luorane 91 dimercaptodibenzyl ether 93 p-dimethylaminophenylacetylene 61 4,4' -bis-dimethylaminotr iphenylacetoni-

t r i l e 103 2.5-dimethylfuran 109 2.6-dimethylpyridine 296 dimethylaniline 1 0 0 dimethy 1-p-to luidine 95 £,,8-dinaphthylamine 94 dinitronaphthols 82 2 ,4-dini troresorc inol 85 diphenylamine 94 diphenyl ether 86 2,4-diphenylselenophene 113 • diphenyl sulfone 93, 94 2,3-dipheny lthiophene 112 dithiosal icyl ic acid 94 N , N ' - d i - p - t o l y l f o r m a m i d i n e 95 durene 74 eosin 92 ethanol 63 a-methoxynaphthalene 86 ethyl e s t e r 61, 69 ethyl resorc inol 85 eugenol 86

f e r r o c e n e 120 f luorene 75, 297 f luorenone 104 f l u o r e s c e i n 91, 92 f luoroacety lene 61 a - f luoroa lkynes 61 f luorobenzene 75 p- f luorobenzoic acid 106 p-f luorophenoi 82 fuchsin base 99 furan 109, 118 fur fura l 109 f u r f u r y l alcohol 109 gal l ic acid, methyl e s t e r s 89 guaiacol 86 halogenoacil ines 100 halogenohydroxyaryl alkyl ketones 88 halogenothiophenols 112 halogenoxylenols 82 n - h e p t a d i e n e - l - y n e 61 hexahydrophenol 65 hexylresorc inol 85 hydroxyaryl alkyl ketones 87 hydroxyary larsonic acids 89 hydroxybenzaldehydes 87 hydroxybenzoic acids 87 hydroxycarboxyl ic acids, aromatic 87 hydroxydiphenyl sulf ide 94 hydroxymercur i acetic acid 69 7 - h y d r o x y - 4 - m e t h y l c o u m a r i n 90 1 , 1 - b i s - (4 ' -hydroxy-6-methylphenyl)cy-

clohexane 82

1-hydroxy-2-naphthoic acid 89 l , l -b is (4 ' -hydroxyphenyl )cyc lohexane 82 hydroxyphenyl methyl ketone 88 indandiole, Na sa l t 66 indene 296 indole 113, 119 iodobenzene 77 iododiphenyl ether 85 2-iodofuran 94 /3-iodosylvan 109 iodothymol 82 is oamylphenol 82 isodurene 74 isoquinoline 117 isovanil l in 87 ketones, aliphatic 64

a l iphat ic-aromatic 66 aromatic 104

leuco base of methylene blue 117 Malachite G r e e n 99 malonic acid 69, 296 mesi ty lene 74 metanil ic acid 99 7 - o-methoxyphenoxyhepty l - l -yne 61 4-m-methoxyphenylbut- l -yne 61 2-methoxythiophene 118 methylacetylene (fully deuterated) 61 2-methylbenzofuran 109 methylcyclopentadienyltr icarbonylman-

ganese 120 methylenedisa l icy l ic acid 89 methylene-bis -malonic acid 60

SUBJECT INDEX 527

Mercuration of (continued) 2-methyl-5-ethylthiophene 118 2-methyl-4-hydroxydiphenyl sulfide 94 methyl isopropyl ketone 64, 71 methylketole 113 methylmalonic acid 60 2-methylmercaptofuran 109 methyl phenyl sulf ide 93 methylquinolines 117 5-methylresorc inol 85 S - m e t h y l s a l i c y l i c acid 94 monochloroacetylene 61 naphthalene 79 1-naphthoic acid 108 a-naphthol 82, 90 /3-naphthol 82, 84, 86 naphtholsulfonic acid 89 a-naphthylacetylene 61 a-naphthylamine 95, 100 a-naphthylamino-4-sulfonic acid 98 /i-naphthylamino-6-sulfonic acid 98 nitroacetic acid 61 m-nitranil ine 100

nitroanisole 85 nitrobenzene 78, 80 nitrocresol 82 5-nitroguaiacol 86 nitro-m-hydroxybenzaldehyde 87 3-nitro-4-hydroxybiphenyl 82 5-nitro-8-hydroxyquinoline 117 nitronaphthols 82 nitronaphthylamines 97, 100 nitrophenols 81, 84 p-nitrophenylacetylene 61 p-nitrophenyl f e r r o c e n e 120 nitroresorcinol 85 nitrosalicylaldeTiydes 87 nitrosothymol 82 nitrothiophenols 93, 1 1 1 nitrotoluenes 78, 80 nitrotoluidines 97 nona-l ,4-diene 61 o c t - l - y n e 68 parafuchsin 99 pentafluorobutyne 61 pentamethylbenzene 74 1 ,l-pentamethylenebicyclo-(0,1,4)-heptane

65 cis-pent-2-en-4-yne 61 phenanthrene 75 phenatole 85 phenol 81, 83, 85, 86, 87, 90, 297 phenolic aldehydes 88 phenolsulfophthalein 92 phenosafranine 117 phenyl acetic acid 106 phenylacetylene 296 phenyldiacetylene 61 phenyldihydroxydibenzopyran 90 phenylethynylcarbinols 61 pheny!glycine, ethyl e s t e r 97, 101 phenylmercaptoacetylene 61 2-phenyl-a, /3-naphthopyrazole 115 phenyl-/3-naphthylamine 95

-phenylpropanol 93 1-phenylpyrazole 114, 119 3-phenyl-5-pyrazolone 114 N-phenylpyrrole 113 phenylsal icyl ic acid 88 phloroglucinol 84 phloroglucinol aldehyde 87 phthaleins 91 a - p i c o l i n e 116 pinacolin 64 polystyrene 75 propanol 63 propionaldehyde 298 propionic acid 296 pseudocumene 74 purine bases 117 , 119 pyridine 119 3-pyridylsydnone 115 pyroracemic acid (pyruvic acid) 63 pyrrole 113, 118 1-pyrrolidinocyclopentene 65 quinaldine 296 quinoline 116, 119 resorcinol 8 4 , 85 resorcinolsulfonephthalein 92 r e s o r c y l i c acid 88 ruthenocene 120 sa l icy l ic acid 87, 88, 89, 296 salicylsulfonephthalein 92 sal icy lsul fonic acid 88 selenophene 113 skatole 113 sodium propionate 62 sulfanilamide 102 sulfonic acids, aromatic 105 ff. sulfosuccinate 63 sylvan 109, 118 terephthalic acid 108

3-tetrahydropyranyloxyprop- l -yne 68 2,2,5,5-tetra(4-hydroxyphenyl)hexane 82 1,2,3,4-tetramethylbenzene 74 4-tetramethylbutylphenol 82 thiazole 114, 119 thionaphthene 112 thiophene 110, 117, 296 thiophenols 93 thiosal icyl ic acid 94 thymol 82, 85 toluene 72, 74, 79 p-toluenesulfonic acid 107, 109 0-toluic acid 105 toluidines 95 p-to ly lmercaptoacety lene 61 tri alky Ifur an s 109 trichlorobenzene 78 trichloroethylene 62, 68, 296 1 , 1 , 1 - tr i f luoropropyne 61 triphenylmethane 296 1-triphenylmethane 296 trans-undec-7-en-l-yne 61 vanillin 87 xanthone 104 m -xy lene 74, 79 xylenols 81


Mercuribenzamide 106, 488 a -Mercuricamphenilone salts 322 M e r c u r i c chloride 16, 160, 208, 466 Mercuric trif luoroacetate 260 a -Mercuri-di-/3 -phenylanhydrohydracrylic

acid, action of acids 339 8-Mercuri- l-naphthoic acid, internal salt

262 Mercuriphthalimide 106 Mercurisuccinimide 487 Mercuriurea 487 Mercurophene- ^odium-4-hydroxymercu r i -

2-nitrophenoxide) 84 Mercurous salts 13, 464 Mercury-bis-acetaldehyde 182, 383 Mercury-bis-(acet ic acid) 378

butyl ester, reactions with acetyl chloride methyl ester 185

reactions withhexaethyldistannane 398', acetyl chloride 1 5 8 , 5 7 7

t- butyl ester 186 ethyl ester, reaction with Bromine 356 a-propylvinyl ester 187

Mercury-bis-acetodialkylmethane 259 Mercury acetylides 13, 40, 61; 67 Mercury alkyl mercaptides 468

reactions with ammonia, halogens, nitro-gen oxides 469

Mercury alkyl selenides 481 Mercury aryl mercaptides 468 Mercury-b is - (m-benzoic acid), methyl ester

311, 329 Mercury benzyl mercaptide 469 Mercury-bis-m-biphenyl 339 Mercury-bis-bromoacetyl ide 19 Mercury 2-o-(trans-2'-bromovinyl) phenyl-

acetylide 68 10, 10-Mercury-bis-camphor 313 Mercury - bis-(chloromercuriacetic acid),

ethyl ester 349 Mercury-bis-(cyclopentadienyltricarbonyl-

manganese) 321 Mercury-bis-(diazoacetic acid), ethyl ester

70 Mercury dibromoacetylide 404 Mercury difluoroacetylide 62 Mercury di-^-phenylacetylide 28 Mercury ethoxide 464 Mercury ethylmercaptide 468 Mercury fulminate 465, 466 Mercury isocyanate 492 3, 3-Mercury-bis-menthane 50 Mercury mercaptides 481 Mercury methoxide 464 Mercury-bis-(methyl propyl ketone), reac-

tion with ketenes 186 Mercury pentachlorophenoxide 465 Mercury phenoxides 464 a-Mercury-bis-(phenylacetic acid), ethyl

ester 326 Mercury phenylacetylide 68 Mercury phenylmercaptide 479 Mercury picrate 465 Mercury-bis (-/3,/3'-propionic acid) 49

Mercury-bis-(propionic acid), methyl ester 49

Mercury propylmercaptide 469 Mercury salts, addition to 2-acetoxymerc-

uri -3-hydroxytetrahydronaphthalene 170

acetoxymercurimethylphenylcarbinol 170 acetylene 148, 2 04 acetylenedicarboxylic acid,dimethyl ester

209 acetylenic acids 209 acetylenic alcohols 158, 159 acetylenic ketones 158, 159, 209 acetylenic pinacols 208 a-alkoxyacrylonitr i les 157 allene 173 allocinnamic acid 189 allyl acetate 179 allylacetic acid 190 allylacetone oxime 188 allylacetorhamnose 176 allyl alcohol 174, 175 allylamides of a-amino acids 198, 199 o-allylaminobenzoic acid 184 ally lbenzene 167 allylbiuret 198 o-al lyl-p-t-butylphenol 179 allylcyclopentane 166 2- trans -al lyldekalin 167 3 - a l l y l - l , 2, 5, 6-di- isopropylidene-d-

mannitol 176 allyldiphenylacetic acid 191 3-allyloxysulfolane 200 0-al ly lphenol 145, 178, 179 allylphenoxy acetic acid 195 al lylresorcinols 179 allylsuccinimide 198 allylsulfonamide 179 allylurea 198 allylveronal 198 antipyrine 200 1-ary l -5-pyrazolone 201 benzobornene 166 bi allyl 172 bicycloheptadiene 173, 174 bicycloheptenecar boxy lie acid 191 bicyclo-(2,2,2)-octene 166 bipropenyl 171 butenes 164 b u t - l - e n - 4 - o l 175 camphene 165 2,7-carbethoxy-2-heptenoic acid 190 carbomenthene 165 carbon monoxide 202 N-(/3-carboxypropyl)-N'-allylurea 198 chaulmo-ogric acid 191 cinnamic acid, allyl es ters 146, 195 cinnamic alcohol 178 citraconic acid 189 coumaric acid 196 coumarin 196 crotonic acid 189 P-crotylaminophenylacetic acid 184 cyclohexene 165, 170

SUBJECT INDEX 529

Mercury salts (continued) c y c l o h e x - 3 - e n - l - o l 176 cyclopentene 165, 169 /3-cyclopentylacrylic acid 189 diallylacetic acid 191 di allyl ether 179 diallylmalonic acid 191 diallylamine 184 di allyl sulfide 179, 180 di allyl sulfone 180 1, 6-diazobicyclo - (4, 4, 0)-3-decen-7,10-

diol 201 dibenzalacetone 185 1.4-dichlorobut-2-yne 205 dicyclopentadiene 166 2-diethylaminomethyl-3-vinylquinuclidine

200 dihydronaphthalene 167, 170 2,3-dihydropyran 200 dimethallyl sulfide 180 dimethylacetylene 205 1,1-dimethylcyclopropane 211 2.5-dimethyldec-3-en-7,10-dione 201 2.6-dimethylhept-5-en-2-ol 175 dimethy lphenylphenylacetylenylethylene

glycol 208 dimethyl phosphonate 4-94 diphenylacetylene 206 1,1-diphenylcyclopropane 211 1,1-diphenylethylene 167 dipropylene oxide 174 divinylbutyral 183 di vinyl ether 180 erucic acid 190 ethylcyclopropane 211 ethylene 160, 161 ethyl thioacetate 469 eugenolacetic acid 195 glutaconic acid 195 hept-l-yne 206 hexa-l ,5-diene 172 hexafluoropropylene 171 h e x - l - e n - 5 - o l 175 isobutylene (isobutene) 164 isolaurolene 165 isoprene 172 isopropenyl acetate 182 isopropenyl n-butyl ether 180 isopropyl ethyl ether 183 itaconic acid 189 maleic acid 189 ketene 157, 185 methacrylic acid 189 1 - methyl-2-acetoxy-2-prop- l -enylmer-

cury chloride 205 methylacetylene 206 3-methylcyclohexene 143 2-methyl - l , 4 - dichloromercuri - 2, 3-di-

hydroxybutane 173 1,4 -methylene-A - cy clohexen- 2- c arboxy-

Iic acid 191 5-methylhept- l -en-5-o l 175 methylheptenone oxime 188 nitrocinnamic acid 195

nopinene 168 norbornen- endio - cis-2,3-dicarboxylic

acid 192 norbornylene (norbornene) 165 octadec-9-enylamine 184 oct - l -yne 206 oleic acid 190

exo, cis -3,6- endo -oxo- A 4 - t e t r a h y -drophthalic acid, dimethyl es ter 193

2,7-pentadecene 164 pent- l -en-5-ol 175 phenylacetylene 206 phenylbutadiene 173 phenylcyclopropane 211 phenylethynyl methyl ketone 209 phenylmethyldiacetylene 207 5-phenyl-2-pentenoic acid 190 phenyl vinylethyl ether 181 pinene 168 piperylene 172 polyfluoroalkenes 164 potassium arylazocarboxylate 237 propargyl alcohol 207 propenylbenzene 167 propiolic acid 209 a -propoxyacrylonitrile 189 a-propylcrotonic acid 189 propylene 163 sorbitol, o -a l ly l ether 176 stilbene 167 styrene 167, 170 sulfol-3-ene 200 a-terpineol 178

1,2,3,6-tetrahydropyridazine 201 tetramethylcyclopropane 211 1,1 ,5,5-tetr amethy lpenten-1 - ol 175 thionaphthene sulfone 199 trifluoroethylene 171 1.1.1-trif iuoropropylene 171 2,3,3- trimethy Ibut-1 -ene 164 1.1.2-trimethylcyclopropane 211 trimethylsilylethylene 164 undecene 164 vinyl acetate 182 vinyl butyl ether 180, 182 N-vinylcarbazole 200 vinylcyclohexene 172 vinyl ethers and esters 155 vinyl ethylene glycol, monomethyl ether

175 vinylglucose 176 vinylphthalimide 198

Mercury stearate 169 cis -a-Mercury-bis-(st i lbene) , conversion

into trans 417 a-Mercury-bis-(st i lbene) 309, 318, 325

reactions with bromine 351 SnCl2 397

Mercury thionaphthene mercaptide 473 Mercury tolymercuripentachlorophenoxide

74 Mercury trifluoromethyl mercaptide 470 2-Methoxycyclohexylmercury 304 2-Methoxycyclohexylmercury chloride 407


cis - 2 - Methoxycyclohexylneophylmercury 290, 407

a-2-Methoxycyclopentylmercury chloride 170

/3-Methoxyethylmercury acetate 203 /3 - (p-Methoxyphenyl)ethy lmercury iodide

169, 346 2-Methoxy-5-thienylmercury chloride 118 I-Methyl- 2- acetoxy-1 -prop-1 -eny Imer cury

chloride 205, 459 cis- 1 - Methyl - 2 - a c e t o x y - l - p r o p - l - e n y i -

thallium dichloride 363 Methylaminomercury nitrate 484 Methyl - 2 - chloromercuri-2-desoxy-3,4,6-

tr i-o-acetyl-/3, D-glucoside, reac-tion with bromine 354

Methyl a-chloromercur i - i sopropyl ketone 259

3-Methyl-3-chloromercuripentan-2-one 259 4-Methylcyclohexylmercury 23, 24, 304,

311, 353, 354 1 -Methyl-1 - cyclohexylmercury acetate, ox-

idation 350 Methylmercury acetate 13, 277, 315, 420

benzoate 14 bromide 19, 23 chloride 24, 254, 265, 282, 419 hydroxide 41% iodide 14, 19, 25,280, 311

bis-I-Methyl-1,2-dihydrobenzofury lmercury 309

Methyl ethyl ketone, e lectrolysis 286 Methyl-lithium 388 Methylmercury ethylmercury sulfide 4%0 Methylmercury n-propy lmercurysulf ide 420 Methylmercury sulfide 419 4 - Methyl -3-nitrophenylmercury chloride

250 Methylpentafluorophenylmercury 298 Methylphenylmercury 293 Methylsodium 387

bis-Naphthylethynylmercury 61 a-Naphthylmercury bromide 23 a -Naphthylmercury chloride 233, 235 a-Naphthylmercury iodide 308 a-Naphthylmercury nitrate 418 a-NaphthyImercury sulfide 473 Neopentylmercury chloride 20, 353 o -Nitrobenzal dimercuroxide 81 Nitrobenzoic acids 312 o -Nitrobenzylmercury 80 3 - Nitro - 5 - carbomethoxyphenylmercury

chloride 250 4-Nitro- l -naphthol-o-mercury acetate 465 b is-o -Nitrophenylmercury 310 OT-Nitrophenylmercury chloride 234, 255 o-Nitrophenylmercury chloride 80, 234,

310, 315 p-Nitrophenylmercury chloride 234, 255,

258 Nitrosomethylurethane 239 n-Nonylmercury bromide 23

Norbornylmercury acetate 346 Nortr icyc ly lmercury chloride 23, 251, 346

s-Octylmercury bromide 23 chloride 21, 251

Organomercury compounds.acidolysis, kin-etics 339

amalgams of cadmium 307, 312 amalgams of sodium 46, 307 amalgams of copper 312 ammonia 306, 322 asymmetrical , disproportionation 303 butyl-lithium 325 calcium chloride 320 copper 306, 309 di-p-aminopheny lmercury 297 diphenylmercury 325 ferrous hydroxide 312 gas chromatography 512 hydrazine 314 hydroxylamine 314 magnesium 311 oxidation 350 ozonization 459 paper chromatography 512 potassium cyanide 319 potassium iodide 307, 316 potassium thiocyanate 319 precautions in work with 5 reactions with acid chlorides 369

acids 338 alkalis 349 bromine 352 N-bromoimides 359 butyl-lithium 403 chlorine 351 diazomethane 294 dichlorocarbene 278 dioxan dibromide 351 Fenton's reagent 350 halogenated-hydrocarbons 377 halogens 351 hydrogen sulfide 349 iodine 351 ketens 402

lead tetra-acetate 368 lithium 386 LiAIH 4 (lithium tetrahydroaluminate)

382 metal carbonyls 351 nitric acid 401 nitrosyl chloride 359 oxygen 337 phosphorus trichloride 369 phthalimide 424 sodium 386 sodium tetrahydroborate 382 thiocyanogen 358 thionyl chloride 372

sodium hydrosulfate, alkalis 321, 322 carbon disulfide 321 cyanide 307, 319 iodide 316

SUBJECT INDEX 531

Organomercury compounds (continued) phenylhydrazine 314 semicarbazide 314 si lver 312 stannite 306, 312 tertiary phosphines 326 tin-sodium alloy 309 triethanolamine 324 thiosulfate 307, 320 zinc 311

symmetrization 303 symmetrization reagents 315

aluminum oxide 327 toxicity 5 vinyl ethyl ether 325

exo , cis -3,6- endo - oxo - A4-tetrahydro-phthalic acid, dimethyl ester 354

Palladium, metall ic 384 Pentacetylglucophranosylguanine 4-91 Pentafluoroiodobenzene 358 bis - Pentafluorophenylmercury, reaction

with iodine 53, 358 bis - Pentafluorophenylmercury, reaction

with conc. H2SO4 339 Pentaphenylantimony, reaction with Hg 268 Pentaphenylphosphorus, reaction with Hg.

CI2 268 bis-Perchlorovinylmercury 68, 319 Perfluoro-2-azapropene 485 Perfluorovinylboron dichloride 361 Perfluorovinyldichloroarsine 371 Perfluorovinylmercury chloride 266, 291,

326 Phenacylmercury bromide 69 Phenacylmercury chloride 69 bis-Pentafluorophenylmercury 30, 53 bis-Perf luorovinylmercury 28 Phenyl acetyl sulfide, reaction with HgCI2

480 Phenylallylmercury 357 Phenylboronic acid 362 Phenylcarbomethoxymercury 298 1 - Phenyl-I -chloromercuribut- l -en-3-one

209 Phenyldiazonium nitrate 401 Phenyldichlorophosphine 370 o-Phenylenemercury, hexamer 30, 34, 51 Phenyl ferrocenyl sulfone 376 Phenyl- o -hydroxycyclohexylmercury 294 Phenyl-Iead triacetate 267 bis-Phenylmercuribenzene 290 Phenylmercurithioglycolic acid 4®3 Phenylmercury acetate 77, 79, 240, 267,

314, 321, 324 acrylate 425 bromide 23, 2'+7, 258,509,403 chloride 23, 232, 234, 236, 246, 253.

265, 282, 326 dialkyl phosphite 419 fluoride 2,21,421 hydroxide 420 methacrylate 425

phenoxide 425 p-vinylbenzoate 425

^-Phenylmercury bromide 23 1 - Phenyl - 2 -methoxy-2-methylpropylmer-

cury acetate 350 Phenyl-3-propyn-2-ylmercury chloride 41 Phenyl-p -tolylchlorophosphine 370 Phenyltrichloromethylmercury 291, 295 Phenyltrichlorosilane 366 Phenyl- 2,4,6- trinitr ophenylmercury 292 Phenylvinylacetylenylmercury 357 Polyfluoroalkylnitroso compounds 401 Poly-(p-iodostyrene) 358 Propargylmercury bromide 22 di-n-propylmercury 2 5 n-Propylmercury bromide 20, 23, 25

succinate 316 Pyrrole, reaction with mercuric chloride

491

Quinoline-3-mercury acetate 119 8-Quinolylmercury 119

Sodium 1, 3-Mercuridimercaptopropan-2-sulfonate 4^4

Sodium tetraethylborate, e lectrolysis 287 a-Styry lmercury bromide 22, 33 w-Styrylmercury bromide 13, 251 p-Styrylphenylmercury 290 Succinimide 424 Sulfoacetic acid 373

o-Terphenylenemercury 51, 385 Tetra- acetoxymercuridiacetone hydrate 69 Tetra-acetoxymercuripyrrole 118 Tetracarbazole 113 2,2',4,4'-Tetrachloromercuridiphenylamine

, 9 4 a, a , 6, B -Tetrachloromercuridi - iso-

propylether 241 n -Tetradecylmercury chloride 21 Tetraethylsi lane 268 bis- (1,2,2,2-Tetrafluoroethyl)mercury 171 Tetrakis-(trif luoroacetyl)hydrazine 4,86 £52,5 '-Tetramethyl-3,3 '-dithienylmercury

308 Tetramethyltin 265 Tetraphenyltin 394 Thallium tri-isobutyrate 363 a-Thienylmercurybromide 267

chloride 318 a-Thienylthallium di-isobutyrate 267 a-Thionaphthenyimercury acetate 320 bis-Trif luoromethylmercury 34, 311 2,2,3,3-Tetramethyl-1 -butylmercury 21 Tetraphenylmercuracyclopentadiene 33, 49 Tolylmercuryhydroxide 421

chloride 79, 232, 235,325 p-Tolylphenylmercury 291 p-Tolyl tr ichlorosi lane 366 p - T olyl-2,4,6-trinitropheny lmercury 292


a ~ 3 ,5-Tr i acetoxymercuri-/3,2 dimethoxy-dihydrocinnamic acid 19 7

Triacetoxymercuri thiazole 119 1.2.3-Tribromocyclopent-4-ene 357 1 .2.4-Trichloro-3-chloromercuribut-2-ene

206 Trichloromercur iacet ic acid, ethyl ester

187 bis-Trichloromethylmercury 260 cis-Tri- jS-chlorovinylst i lb ine 266 bis-Trideuteromethylmercury 53 bis-I-Thienylethynylmercury 61 Triethylstannylacetic acid, es ters 395,

398 1 ,1 ,1 - T r i f l u o r o - 3-ethoxypropyl - 2 - m e r cury

nitrate 171 Trif luoromethylmercuryiodide 311, 12

trif luoroacetate 260 bis- (OT -Trif luoromethylphenyl)mercury 34 T r i f u r y l a r s i n e 267 Trimercuridiacetone hydrate 68 Trimethylmercurioxonium perchlorate 419 1,2,4-Trimethylphenylenemercury 51 Trimethyls i lane 268 Trimethyls i ly lmethylmercury chloride 21 Trimethylvinyloxysilane 367 1,1,1 - T r i n i t r o-3- chl or omercur ipr opane 162 Trinitromethylphenylmercury 78

bis-(Trinitropropyl)mercury 162 1 ,1 , 1 -Tr in i t ro - 3- (trinitromethylmercuri)-

propane 162 Triphenylmethylacetaldehyde 377 Triphenylmethylferrocene 376 Tripropylgermanylacetic acid, methylester

367

Veratr ic acid 262 Vinyl acetate 377 Vinylboron dibromide 361 Vinyldibromophosphine 369 Vinyl ethyl sulfide, reaction with mercur ic

chloride 475 Vinyl-lithium 387 N-Vinylmercurimides 424 Vinylmercury bromide 22, 22

symmetrization 313 Vinylmercurychloride 22 Vinylmercuryiodide 22 Vinylmercury thiocyanate 422 Vinylmercury xanthate 422 Vinylpotassium 387 Vinyltrichlorogermanium 367

Wilgerodt's Reaction 374

Of related interest:

O . A. REUTOV, Moscow State University, USSR

Fundamentals of Theoretical Organic Chemistry Translated from the Russian under the editorship of

Th. J. Katz. 1967. 601 pages. Hfl. 75.- (150s.)

Professor Reutov presents organic chemistry as a system of

self-consistent principles which fol low from basic phenome-

na rather than a disjointed set of facts. Using numerous

il lustrations of charts, figures and diagrams, emphasis is on

mechanisms, basic theory , electronic phenomena and

kinetics. This is a modern approach to organic chemistry

which will serve as a valuable reference to professional

chemists, t o researchers in o ther fields and t o advanced

students.

C O N T E N T S . The theory of chemical structure. Substitu-

tion on a saturated carbon a tom. Elimination reactions.

Add i t ion to unsaturated compounds . Free radicals. Esteri-

fication and hydrolysis. Subst i tut ion on unsaturated

carbons. Subst i tut ion in aromatic compounds . Molecular

rearrangements. Tautomerism and dual reactivity.

North-Holland

This volume, devoted to the organic compounds of mercury, is based on the monograph 'Synthetic Methods in the Field of Organometallic Compounds of Mercury' by L. G. Makarova and A. N. Nesmeyanov, which was published in 1945. In the following twenty years the chemistry of organometallic compounds developed very rapidly, which meant that an enormous volume of data had to be sorted, and that the size of the book had to be more than doubled, preserv-ing at the same time its highly con-densed treatment of the subject. The book makes exhaustive references to the literature dealing with methods of synthesis involving the organic com-pounds of mercury up till 1 January 1964- and includes the more important work carried out in 1964 and early 1965.

makarova nesmejanov-organic compounds of mercury

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