415

Journal of Organometallic Chemistry, 127 (1977) 415-421 0 NIsevieI sequoia S.A., Iausann e -PrInted in The Metheriands

Pentamethylcyclopentadienyl-rhodium and -iridium Complexes. ___________~_______~~~~~~~~~~~~~-~--~-~~---~--~~~~~~~~~~~~

Part XIII. 1 ns-Oxocyclohexadienyl- and na-Phenol-Complexes_ _________~__________~~~_~~__~~~~~~~~~~~~~~~~~~~~~~~~~__~~~~~

COLIN NHITE. STEPHEN J. THOMPSON and PETER M. MlITLIS*

Department of Inorganic Chemistry, The University, Sheffield S3 7HF, England.

(Received December 7th, 1976)

Summary --__--_

The acetone solvent complexes ~~~rts-CsMe,)(Me2CO)31fPF612,

(H = Rh, Ir)-prepared in situ from [M(ns-CSMeS)Cl.& and AgPF6 in

acetone, reacted with phenol to give the hydrogen-bonded dimeric

phenol complexes (II) [<M(n5-CS~leg)~2Cr16-PhO-H--- 0(na-)Ph)7[PF~]~; these

were easily deprotonated with base to the corresponding ns-oxocyclohexa-

dienyl complexes [M(n5-CgMeS)(ns-C6HSO)]PF6. which showed v(C=O) at

1630 (Rh) and 1635 (Ir) cm”. An unstable $-phenol iridium complex,

Dr(C$e,)(PhOH)l~PF612,was obtained on protonation of (II, M = Ir).

Although a number of $-phenol complexes have been prepared [2-71 little

of their chemistry has been reported. It is especially surprising that

deprotonation reactions have not been n-ore exploited in particular as a number

of workers have noted that the acidity of phenol (and substituted phenols) is

considerably enhanced on complexing to a transition metal c2.71.

In continuation of our work on the arene(pentarozthylcyclopentadienyl)-

rhodium and -iridium cations [1.8,9), we here report on cationic complexes of

da-phenol and n5-oxocyclohexadienyl (deprotonated phenol). The latter ligand

does not appear to have been observed previously_

Note added in proof:

Since this ‘paper I& prepared we have no&d that Cole-Hamilton et al - have hlso recently reported n*-oxocyclohexadienyT compTexes of Rh and

‘~Ru; the crystal structure of one of their complexes confirms the ri’- .- _ _ ~oxocyclohexadiinyl formulation (D.3, CoTe-HamiTton. R-J. Ybung. and

;--‘6;~~~‘lk~_~o~,,J;C.S.:Da~_~n~C1976) 1995.1 d.. _ .

416

phenol ~acterf with both the rhodium and iridium acetone solvent

complexes (ra and Ib) [ZO] to give the hydrogen-bonded dimer c~~~nds

(II), which are assigned the structure shown on the basis of analysis, NMR

and particularly the IR spectra.

Complexes containing intermolecular hydmgen bonds show v(OH) as a broad

band in the region 1400-3000 an-1 [ll]; increase of the O-H---O bond strength

is paralleled by a decrease in the frequency of the band and splitting is

also observed- for example, the hydrogen-bonded adducts of Rhydmxyquinoline

with o-nitmphenolate coczplexes of Na, K, Rb and Cs shoiied tno broad bands in

the regions 1800-1900 and 2400-2600 an-’ [JZ].

The iridium comp?ex (IIb) showed similar broad bands at 1830 and 2360 cm’.

the intensities of which were considerably decreased after exchange with D20,

and which are assigned to (O-H---O) by analogy. For the rhodium corcplex (IIa)

only the higher frequency vibration (at 2350 cm-‘) could be observed as a weak

and very broad band; this band disappeared canpletely after exchange with 020.

Hydrogen-banded comp7exes of this type have not been described previously,

but Weiss and HUbel [13] noted the formation of H-bonded adducts between quinol

and complexes the ligands of which contained a ketonic CD, e.g. cyclopenta-

dienone- and tropone-(tricarbonyl)iron. They also noted that cyclopentadienone-

(tricarbonyl)iron readily formed salts with acids, [Fe(C5H40H)(CO)31CX~.

The rhodium hexafluorophosphate complex (IIa) was unstable in acetone and

decomposed slowly (40X in 48h/20°C) to tris-u-difluomphosphato-bis-(penta-

methylcycJopentadienyl)dirhodium hexafluomphosphate. which we have previously

shwn to be generated from [Rb(C5E’e5)(S?e2CO)3j[PF6}2, (Ia), on standing in

acetone EiO].

llte complexes (IIa and IIb) reacted with base (Na2C03-H20) to give the

deprotonated compounds (III), the IR spectra of which new showed two new bands,

a very strong one at 1630 cm-’ (Rh) [and 1635 (Ir)] together with one at

1595 an-’ (Pa) Land 1610 (II-)]. These we assign to coupled v(C=D) and v(C=C)

vibmtions [g(C=C) at 1570 in (IIa) and 1552 cm-l in (IIb) have_nm -~ -_

d+-- S@ez!*_ - _ .-

417

The deprotonated complexes (IIIa and IIIb) may be formulated as containing

either an +phenolate (III') or an $- oxocyclohexadienyl (III) ligand.

However, neither phenol, phenolate ion, nor complexes containing M-OPh show

strong bands in the carbonyl region [14-j. By contrast, a large ntier of

complexed cyclic ligands containing .~&-a .s’-unsaturated ketones

(-CR=CR-CO-CR=CR-) are known which shcr.9 strong bands in the IR between 1550

-1 and 1650 cm . For example, a variety of substituted cyclopentadienone(tri-

-’ carbonyl)iron coinptexer showed v(COj at 1605-1650 cm [15], Fli(duroquinone)2

has v(CO) at 1577 cm-1 1163, [Rh(duroquinone)Cl]n has “(CO) at 16g8 cm-1 1173

(c-f. v(C0) for uncomplexed cyclopentadienones is in the region of 1700 cm-1

and for free duroquinone is 1629 cm-‘).

We therefore conclude that the best representation for the deprotonated

rhodium and iridium compounds is indeed the n5 -0xocyclopentadienyl form (IIIa) _-

or (IIIb)- Support for this suggestion also comas from the lH NMR spectra

which show that in the complexes (III) the ortho-hydrogens are moved

substantially more further upfield [ca. O-6 ppm, by comparison with (IIa or b)]

than are the m- and p-hydrogens [O-Z to 0.35 ppm]. Hydrogens attached to C(2) and

C(6) in 2-6-n-cyclohexadienyl complexes are usually observed at high field

[8,18]; the upfield shift in (III) is somewhat mitigated owing to the proximity

of the carbonyl and also because of the positive charge on the conTriplex.

The iridium complex (IIb) was protonated in hexafluorophosphoric acid to

a complex which showed no v(OH) in the IR spectra attributable to hydrogen-

bonding and only a mediumweak intensity band at 1565 cm-l. Th% complex

was difficult to purify and analyse and reverted to the hydrogen-bonded

complex (Iib) when warmed in vacua (5 mia/54’%). It is fOrmulated as the

q6-phenol complex (IV). Addition of HPF6 to the rhodium cc#i@leX (IIa) did

-not give a clean reaction and no product was isolated.

The interconversions are sumarised in the Scheme.

Tabl

e

Anal

ytt

cal

and

spec

tros

copi

c da

ta

* Co

mpl

ex

Atia

lyse

s (c

alcu

late

d fig

ures

in

pa

rent

hese

s)

lH

n,m

,r,

(6)a

In

frar

edb

(cm

”)

C’ H

C5M

e5

ring

pr

oton

s

” ~!

Rh(CgMeg)(C6H50))2Hl(PFg)3

UIa)

34,8

3,

9 2,

30(s

) o-

H,6.

32(m

) w

(O-H

e0)2

350(

v,br

) ./

,

<I

,>(

,I ,‘.

.,[(lr

(c~

Me,

)(C

gH50

))2H

I(P

F6)

J

(35,

O)

(3*8

) III

-,p-H

,7,0

5(m

) ,:,

./I

v(

C=C)

1570

(m)

(IIb

) 30

.1 3*

1 2,

42(s

) 0-

11,6

.30(

m)

v(O-

H-*0

)236

0(br

),l83

0(br

) I. (

II,

‘I j.

(30,

4)

(3~

) m

- ,p

-H,6

,5O(

m)

u(C=

C)l5

52(m

),151

2(w

)

,! tt

i(C5~

e5)(C

5H50

)1PF5

(II

Ia)

40,2

46

4 2.

22(s

) o-

H ,5

. ?O

d[J(

H-H)

n7]

v(C=

O,C~

C)16

3O(v

s),l5

95(s

) ,I

‘,/

‘8

I’,,

.,,P

’, (4

0,4)

(4

,2)

m-H

,p-H

,6

.62(

m)

s, i’

%

~Ir

(Cgk

,5)(

CgH

50)3

PF

s 34

,2

3,7

,I;

(IIIb

) 2,

34(s

) o-

H,5.

76dd

v(

C=O)

1635

(vs)

,16

10(s

)

,‘,

,, : ,

,1*/

(3

4.0)

\3

.6)

[i(

l-H-m

-H)=

7;

_,

’ “(1

>I

‘,

, ,,

’ ‘11

1 .,

J( o-

H-p-

H)=2

Hr]

‘,,

1 ‘.

, ’

~:‘~

jr;(e

,ns6

)‘(C6

H50H

)~(P

F6)2

mH,

p-H,

6.60

(m)

(IV)

2,a7

c 3.

1 2.

48(s

) o-

H,6.

54(m

) v(

C=C)

1565

(m)

,,,

/ ,,

<a

; ,I

(270

0)

(3.0

) m

-H,p

-H,7

.07(

m)

,! /

m ,/, s

“,

s:

. >

‘/ ‘( ‘

I /,

, .’

4,

In

acet

one-

d5.

,$b”

. ,, 8

1 ,,,

,: :;

.I .“

!,a

/ ” b

,‘is

Nujo

l m

ulls

, !,‘

11_,

,’ :,,I '

8'

',

,J,:.

: "

,',,!

I,,' /' C

I, ‘,

, / ”

I ‘8

‘.R

eadl

ly

depr

oton

ated

In

va

cua.

420

[Ir(C5M~5)(I.Ie2C0)31[FF612- Phenol (0.05 g, 0.53 mmole) was added to this

solution and the mixture stirred for a further 10 min. The solvent was removed

in vacua to give an off-white solid which was washed with chloroform and ether,

and then crystallized from acetone and ether to give pure white crystals of

(IIb) (0.25 g. 78%).

The white rhodium analogue, [CRh(C5Me5)12C(Rh0)2HI][PF6]3 (IIa), was

prepared in 83% yield using the procedure described above.

CIr(C5Neg)(C6H50)IPF6 (IIIb)

The hydrogen-bcnded phenol complex (IIb) (0.2 9, 0.15

acetone (20 ml) containing water (0-l ml) was stirred with

nrmcil) dissolved in

sodium carbonate (0.2 g

for 30 min- The solvent was removed in vacua to leave a yellow solid which was

crystallised from acetone-ether to give [Ir(C5He5)(CgH50)]PF6 (0.15 g. 85%).

CRh(C5Re5)(C6H50)]PFS (IIIa)

The yelled rhodium complex (IIIa) was obtained in 80% yield from (IIa) in

an analogous manner. The 13C {IHi NHR spectrum (in acetone-d6) showed

resonances at 6 9.5 (s,C&). 92-9 [d,Q!e5.A(C-Rh)=4Hr], 89.3 [d,p-C in

C6H50,J=SHzJ. 104.6 [d,o-C in C6H5G, J=6Hz], and 106.3 [d,m-C in C6H50, J_=6Hz];

C(1) in C6H50 could not be observed.

[Ir(C5t~5)(PhOH)l[PF612 (IV)

A solution of the hydrogen-bonded iridium phenol complex (IIb) (0.1 g.

0.08 mmol) in acetone (10 ml) was treated with hexafluorophosphoric

acid (0.3 ml), The solution was stirred for 5 min. and then ether was added

until a white precipitate of [Ir(CSf~eS)(PhOH)l~P~612. (IV), appeared. The

precipitate was filtered off, washed with ether and briefly dried. Yield,

0.05 g. 50%; attempts to purify this material further failed ouing to the ease

with which it decomposed to regenerate (IIb).

He thank- the S-RX. for-support of this work and 1X.1. Ltd;, for a grant . _

&war& *e #za&szre~uf tzkinfmfs* -~- -- ,< _--

421

1

2

3

4

5

6

7

a

9

10

11

12

13

14

15

16

17

18

Part XII, C_ Uhite. 5. J. Thotllpson and P_ M. Maitlis, submitted for

publication.

E. 0. Fischer, K. 6fele. H. Essler, W. FrBhlich. J. P. Mortensen. and

W. Semlinger. Chem. Ber,, 91 (1958). 2763.

G. Natta, F. Calderazzo and E. Santatirogio. Chim. Ind. (Milan), 40,

(1958) 2763.

H. P. Fritz and C. 6. Kreiter, J. Organometal. Chew. 7 (1967) 427.

J. Besan$on and 3. Tirouflet, Rev_ Chim. Min., 5 (1968) 363.

M. Green and T. A. Kuc. J.C.S. Dalton (1972) 832.

A. Wu, E. R. Biehl and P. C. Reeves, J.C.S. Perkin II. (1972) 449.

C. Hhite and P. 14. Maitlis. 3. Chem. Sot. (A).. (1971) 3322.

C. White, S. J. Thompson and P. H. Maitlis, J.C.S. Chern. Comm., (1976) 409.

S. J. Thompson, P. M. Bailey, C. White and P. H. Maitlis. Anger. Chemie

Int. End., 15 (1976) 49B.

H. Ratajczak and W. J. Orville-Thomas, J. Mol. Structure, 1 (1967-68;

449; J. C. Speahan, Structure and Bonding, 12 (1972) 14?_

A. K. Banerjee, A. J. Layton, R. S. r!yholm and M. R. Truter, J. Chem. Sot. !A),

(1970) 292.

E. Weiss, R_ Morenyi and W. HUbel, Chem. Ber., 95 (1962) 1170;

E. Weiss and W. HUbel. i&, 9§ (1962) 1179.

L. J. Bellamy, “The Infra-red Spectra of Complex Nolecules”, Hethuen,

London, 1954. p-83 et seq.; 3. F. Harrod, Canad. 3. Chem., 47 (1969)

637; see also Y. S. Sohn dnd A. L. Balch,J. Amet-_ Chem. Sot.. 94 (1972) 1144.

E. Weiss and W. Hlibel. J. Inorg. Nucl. them., 11 (1959) 42.

G. N. Schrauzer. Adv. Organomtal. Chem., 2 (1964) 19.

S. NcVey and P. M. Haitlis, Can. J. Chem., 44 (1966) 2429-

H. L. Maddox, S_ L_ Stafford and H. 0. Kaesz. Adv. Organometal. Chem.,

3 (1965) 129.