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Inorganic Chemistry Communications 7 (2004) 868–870

Syntheses and structures of silver(I) clusters uniquely exhibitingthree distinct binding modes, two of which are novel,

for a dithiophosphate ligand q

C.W. Liu *, Ben-Jie Liaw, Lin-Shu Liou

Department of Chemistry, Chung Yuan Christian University, Chung-Li 320, Taiwan, ROC

Received 22 April 2004; accepted 8 May 2004

Available online 8 June 2004

Abstract

An unprecedented, triply bridging sulfur atom of the dithiophosphate ligand was observed in the new silver cluster cation, Ag4(l-dppm)2[S2P(OEt)2]

þ3 , where the coordination geometry for the trifurcated sulfur atom exhibited distorted seesaw.

� 2004 Elsevier B.V. All rights reserved.

Keywords: Clusters; Silver; Dithiophosphates; Bonding modes; Seesaw geometry

1 1a: UV–Vis (CH2Cl2) k, nm (e, dm3 mol�1 cm�1): 270 (43,200), 310

(14,800), 338 (8800); 31P{1H} NMR (CDCl3), d 106.9 [S; 3p], 0.04 [br;

4p]; 1H NMR (CDCl3), d 1.25 (t; 18H, CH2CH3), 3.32 (br; 4H), 4.12

(m; 12H, CH2CH3), 6.88–7.68 (m; 40H); positive FAB-MS

(m/z): 1754.9(Mþ), 1370.9 (Mþ-dppm); Anal. Calcd. for

Dialkyl dithio-phosphates (phosphinates or phos-

phonates) are versatile ligands and displaying a variety

of coordination patterns which lead to a great diversity

of molecular and supramolecular structures [1]. Their

metal complexes have important industrial applications

and academic interests, e.g., lubricant additives [2], sol-vent extraction reagents for metals [3], potential lumi-

nescent sensors [4], agricultural insecticides derivatives

[5], precursors for use in metal-organic chemical vapor

depositions [6], and model compounds for metal-con-

taining enzymes [7]. Thus the understanding of the

chemistry of their metal derivatives especially the inter-

action of metal–sulfur bonding is important in relation

with these uses [1b].Of the various bonding modes revealed in the phos-

phor-1,1-dithioato (dtp) ligands, two sulfur atoms

bridging across the triangular plane comprised of three

metal atoms deserved further exploring. Only type I,

trimetallic triconnective (l3:S2, S) bridging pattern, is

known in several homo and/or heterometallic clusters

containing group 11 metals [8] (Sketch 1). Both type II

(l3:S2, S2) and type III (l3:S3, S) bonding modes of

qSupplementary data associated with this article can be found, in the

online version, at doi:10.1016/j.inoche.2004.05.011.* Corresponding author. Tel.: +886-3-2653321; fax: +886-3-2653399.

E-mail address: chenwei@cycu.edu.tw (C.W. Liu).

1387-7003/$ - see front matter � 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.inoche.2004.05.011

which the latter exhibited a trifurcated sulfur atom and

the former has each sulfur atom bridged two metal

atoms have never been identified in any phosphor-1,1-

dithioato metal complexes. Herein we report the syn-

thesis and structures of tetranuclear silver(I) complexes

uniquely exhibiting three distinct binding modes, two(types II and III) of which are novel, for a dithiophos-

phate ligand.

Clusters 1 formulated as Ag4(l-dppm)2[S2P(OEt)2]þ3

were prepared from the reaction of Ag(NCCH3)4X

(X¼BF4, 1a; PF6, 1b), dppm, and dtp ligands in a ratio

of 4:2:3 in CH2Cl2 solution at ambient temperature in

�75% yield. The resultant, analytically pure colorless

crystals were spectroscopically characterized, and satis-factory elemental analyses were obtained. 1

Ag4P7S6O6C62H74BF4: C, 40.41; H, 4.05; S, 10.44, Found: C, 40.33;

H, 4.23; S, 11.05; 1b: 31P{1H} NMR (CDCl3), d 106.9 [S; 3p], 1.32

[br; 4p]; 1H NMR (CDCl3), d 1.20(t; 18H, CH2CH3), 3.37(br; 4H),

4.04(m; 12H,CH2CH3), 7.11–7.65 (m; 40H); Anal. Calcd. for

Ag4P8S6O6C62H74F6: C, 39.17; H, 3.92; S, 10.12, Found: C, 39.22;

H, 4.14; S, 10.32%.

RO

P

OR

S S

M MM

RO

P

OR

S S

M MM

RO

P

OR

S S

M MM

I II III

PS

EtO

OEt

S

Ag

Ag P

PAg

S

Ag

P

PS

PS

EtO

EtO

P

SOEt

OEt

1

Sketch 1.

Fig. 1. The thermal ellipsoid drawing (40% probability) of 1a. The

phenyl groups have been omitted for clarity. Selected bond lengths (�A)

and angles (�): S(1)–Ag(2) 2.668(2), S(1)–Ag(4) 2.706(2), S(1)–Ag(1)

2.624(2), S(2)–Ag(4) 2.711(2), S(3)–Ag(2) 2.723(2), S(3)–Ag(3) 2.560(2),

S(4)–Ag(2) 2.801(2), S(4)–Ag(4) 2.606(2), S(5)–Ag(1) 2.746(2), S(5)–

Ag(3) 2.587(2), S(6)–Ag(1) 2.632(3), Ag(1)–Ag(2) 3.140(1), Ag(1)–P(1)

2.387(2), Ag(2)–P(2) 2.404(2), Ag(3)–P(3) 2.410(2), Ag(4)–P(4)

2.400(2), S–P 1.949(3)–2.019(3); Ag(4)–S(1)–Ag(1) 155.66(9), Ag(2)–

S(1)–Ag(1) 72.79(5), Ag(2)–S(1)–Ag(4) 85.78(6), P(5)–S(1)–Ag(2)

101.85(10).

C.W. Liu et al. / Inorganic Chemistry Communications 7 (2004) 868–870 869

Compound 1 crystallizes in the monoclinic space

group P21=n with four molecules per unit cell. 2 The

cationic cluster consists of four AgI atoms connected by

two dppm units and three dithiophosphate (dtp) ligands

in a tetrahedral arrangement (Fig. 1). The shortest Ag–

Ag distance in 1 is 3.140(1) �A. While each dppm moiety

acts as a simple bridging unit, the coordination pattern

for three dtp ligands exhibits differently. One is bime-tallic triconnective (l2:S2, S), the other is trimetallic

tetraconnective (l3:S2, S2), another is also trimetallic

tetraconnective (l3:S3, S), but one of the sulfur atoms

shows a l3 bridging linking three silver atoms (Ag(1),

Ag(2) and Ag(4)). The Ag–S distances are in the range

of 2.560(2)–2.801(2) �A with the longest existing between

the Ag(2) and S(4). Consequently all the silver atoms but

Ag(3) are tetragonally coordinated by three sulfur atomsof two different dtp ligands and one phosphorus atom of

the dppm moiety. The coordination environment of

Ag(3) is trigonal with a PS2 chromophore. Alternatively,

the structure can be described as a distorted, tetrahedral

Ag4 unit where four of the six edges were bridged by the

sulfur atoms of three different dtp ligands with the re-

2 Crystal data for 1a: C62H74Ag4BF4O6P7S6, M ¼ 1842:65, mono-

clinic, space group P21=n, a ¼ 23:735ð3Þ, b ¼ 11:414ð2Þ, c ¼ 28:781ð4Þ�A, b ¼ 103:74ð1Þ�, V ¼ 7573:7ð18Þ �A3, Z ¼ 4, lðMo KaÞ ¼ 1:387

mm�1, Dc ¼ 1:616 g cm�3. The structure, refined on F 2, converged

for 9831 unique reflections ðRint ¼ 0:0367Þ and 7997 observed reflec-

tions with I > 2rðIÞ to give R1 ¼ 0:0500 and wR2 ¼ 0:1313 and a

goodness-of-fit¼ 1.122. Crystal data for 1b: C62H74Ag4F6O6P8S6,

M ¼ 1900:81, monoclinic, space group P21=n, a ¼ 23:724ð2Þ,b ¼ 11:519ð1Þ, c ¼ 28:842ð2Þ �A, b ¼ 103:09ð1Þ�, V ¼ 7677:1ð10Þ �A3,

Z ¼ 4, lðMo KaÞ ¼ 1:395 mm�1, Dc ¼ 1:645 g cm�3. The structure,

refined on F 2, converged for 10051 unique reflections ðRint ¼ 0:0344Þand 6231 observed reflections with I > 2rðIÞ to give R1 ¼ 0:0678 and

wR2 ¼ 0:1581 and a goodness-of-fit¼ 1.028.

maining two bridged by dppm units. To our knowledge

this is the first example of which the dtp ligands dis-

played three different connection patterns in one cluster.

The S–P distances are averaged 1.983(3) �A.

While a bimetallic triconnective (l2:S2, S) connectionpattern is not unusual [1], the other two coordination

modes for dtp lignads are extremely rare. Previously

each sulfur atom of the dtp ligand connecting two metalatoms were revealed in two occasions: one is edge-cap-

ped the square face of the cube in several octanuclear

species such as [Cu8(X)(dtp)6]z (X¼ S2�, z ¼ 0; X¼Cl,

Br, z ¼ 1�) [9] and Ag8(S)(dtp)6 [10], the other involved

the Tl� � �S secondary interactions, leading to complex

two-dimensional structures in [Me2Tl{S2P(OR)2}]n [1].

Examples shown hear clearly demonstrated that two

bifurcated sulfur atoms can also be edge-capped a tri-angular face.

The triply bridging sulfur atom of the dtp ligand de-

serves further commenting. Previously the l3-S of the

dithiolato ligands were found in two occasions: one is

{Pt4(C6F5)8[(l3-S)SCOEt]2}2�, reported by Uson et al.

[11], the other is {Ag5(l-dppm)2[S2CC(CN)P(O)-

(OEt)2]2}þ from this group [12]. The l3-S–Ag bond dis-

tances in 1 lie in the range 2.624(2)–2.706(2) �A which are

870 C.W. Liu et al. / Inorganic Chemistry Communications 7 (2004) 868–870

within the reported limits [13] and definitely not belong to

the secondary interactions, and the coordination geome-

try of the triply bridging sulfur atom in 1 is like a ‘‘seesaw’’

which is evident from the angles of Ag(4)–S(1)–Ag(1)

(155.66(9)�) and P(5)–S(1)–Ag(2) (101.85(10)�). More-over, the 1,1-dithiolato-type ligands capped the triangular

faces of the tetrahedron always have the edge-bridging

sulfur atom. Instead the title compound adopts the

asymmetrical, face-bridging pattern for the sulfur atom.

However, structures consist of trifurcated sulfur atom

are not unusual for thiocarboxylato metal complexes.

Notable examples are Cu4(SC{O}Me)4(PPh3)4,Cu4(SC-

{O}Ph)4[PPh3]3, [Cu3(l-dppm)3(SC{O}Me)2]PF6],[Cu3[(l-dppm)3(SC{O}Ph)2][ClO4], and [(AgPPh3)4(l3-SC{O}Ph)2(l-SCOPh)2] [13]. The sulfur atom acts as

a l3-bridge is also known for mercaptopyridine ligands in

the one-dimensional chain structure of [Ag6(l3-SC5H4N)4(l4-SC5H4N)2]1 [14].

In conclusion, the novel bonding modes for the dtp

ligands observed in 1 have the structural studies signif-

icant. Recently the triply bridging sulfur atom of the dtpligand is also found in tricopper clusters, Cu3(l-dppm)2[S2P(OR)2]

þ2 (R¼Et, Pri), and the details will be

reported soon.

Acknowledgements

We thank the National Science Council of Taiwan

(NSC 92-2113-M-033-012) for the support of this work.

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