Alkylthio bridged 44 eve triangular platinum clusters: Synthesis, oxidation, degradation, ligand substitution, and quantum chemical calculations

Published on Web 03/23/2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters:

Synthesis, Oxidation, Degradation, Ligand Substitution, and

Quantum Chemical Calculations

Christian Albrecht,^†Sebastian Schwieger,^†Clemens Bruhn,^‡Christoph Wagner,^†

Ralph Kluge,^†Harry Schmidt,^†and Dirk Steinborn*^,†

Contribution from the Institut fu¨r Anorganische Chemie, Martin-Luther-UniVersita¨t

Halle-Wittenberg, Kurt-Mothes-Straâe 2, D-06120 Halle, Germany, and Institut fu¨r Chemie,

UniVersita¨t Kassel, Heinrich-Plett-Straâe 40, D-34132 Kassel, Germany

Received November 27, 2006; E-mail: steinborn@chemie.uni-halle.de

Abstract: Acetylplatinum(II) complexes trans-[Pt(COMe)Cl(L)₂] (L ) PPh₃, 2a; P(4-FC₆H₄)₃, 2b) were found

to react with dialkyldisulfides R₂S₂(R ) Me, Et, Pr, Bu; Pr ) n-propyl, Bu ) n-butyl), yielding trinuclear 44

cve (cluster valence electrons) platinum clusters [(PtL)₃(µ-SR)₃]Cl (4). The analogous reaction of 2a-b

with Ph₂S₂gave SPh bridged dinuclear complexes trans-[{PtCl(L)}₂(µ-SPh)₂] (5), whereas the addition of

Bn₂S₂(Bn ) benzyl) to 2a ended up in the formation of [{Pt(PPh₃)}₃(µ₃-S)(µ-SBn)₃]Cl (6). Theoretical studies

based on the AIM theory revealed that type 4 complexes must be regarded as triangular platinum clusters

with Pt-Pt bonds whereas complex 6 must be treated as a sulfur capped 48 ve (valence electrons) trinuclear

platinum(II) complex without Pt-Pt bonding interactions. Phosphine ligands with a lower donor capability

in clusters 4 proved to be subject to substitution by stronger donating monodentate phosphine ligands (L′

) PMePh₂, PMe₂Ph, PBu₃) yielding clusters [(PtL′)₃(µ-SR)₃]Cl (9). In case of the reaction of clusters 4 and

9 with PPh₂CH₂PPh₂(dppm), a fragmentation reaction occurred, and the complexes [(PtL)₂(µ-SMe)(µ-

dppm)]Cl (12) and [Pt(µ-SMe)₂(dppm)] (13) were isolated. Furthermore, oxidation reactions of cluster [{Pt-

(PPh₃)}₃(µ-SMe)₃]Cl (4a) using halogens (Br₂, I₂) gave dimeric platinum(II) complexes cis-[{PtX(PPh₃)}₂(µ-

SMe)₂] (14, X ) Br, I) whereas oxidation reactions using sulfur and selenium afforded chalcogen capped

trinuclear 48 ve complexes [{Pt(PPh₃)}₃(µ₃-E)(µ-SMe)₃] (15, E ) S, Se). All compounds were fully

characterized by means of NMR and IR spectroscopy, microanalyses, and ESI mass spectrometry.

Furthermore, X-ray diffraction analyses were performed for the triangular cluster 4a, the trinuclear complex

6, as well as for the dinuclear complexes trans-[{Pt(AsPh₃)}₂(µ-SPh)₂] (5c), [{Pt(PPh₃)}₂(µ-SMe)(µ-dppm)]-

Cl (12a), and [{{PtBr(PPh₃)}₂(µ-SMe)₂] (14a).

Introduction

variable M₃clusters may build a bridge between molecular

chemistry, solid-state chemistry, and nano science. Hence, the

The research of metal clusters is a recognizable discipline in

the field of inorganic chemistry that gains continuously in

importance because of the special electrical, magnetical, chemi-

cal, and especially catalytical properties of these compounds.¹

Over several decades, a plethora of large polyhedral clusters

were synthesized that reach deep into the nano scale.²According

to the definition of a metal cluster, “a finite group of metal

atoms that are held together mainly or at least to a significant

extent, by bonds directly between the metal atoms, even though

some non-metal atoms may also be intimately associated with

the cluster”,³the triangular M₃unit represents the smallest

cluster of all. Furthermore, M₃units can be regarded as the

smallest section of metal surfaces or crystallites. This demon-

strates that the chemistry of naked and ligand-stabilized electron

detailed research of the electronic situation and the structural

variety of triangular clusters, especially of the late transition

metal clusters, are of major and fundamental importance.

Triangular platinum clusters from 42 up to 46 cluster valence

electrons (cve) have been prepared with the 42 cve clusters being

the most prevalent ones. All of these clusters possess bridging

ligands that may be µ₂ligands like CO, SO₂, H, CNR as

represented by [{Pt(PR₃)}₃(µ-CO)₃],⁴[{Pt(PR₃)}₃(µ-SO₂)₃],⁵

[{PtH(PR₃)}₃(µ-H)₃],⁶and [{Pt(CNR)}₃(µ-CNR)₃],⁷bidentate

ligands like bis(diphenylphosphino)methane (dppm) in [Pt₃-

(CNR)₂(µ-dppm)₃](PF₆)₂,⁸or µ₃ligands like CO, H in [Pt₃Cl-

(µ₃-CO)(µ-dppm)₃]Cl,⁹and [{Pt(µ-dppm)}₃(µ₃-H)](PF₆).¹⁰Ob-

(4) Moor, A.; Pregosin, P. S.; Venanzi, L. M. Inorg. Chim. Acta 1981, 48,

153.

^†Martin-Luther-Universita¨t Halle-Wittenberg.

^‡Universita¨t Kassel.

(1) Moskovits, M. Metal Clusters; John Wiley & Sons: New York, 1986.

(2) Braunstein, P.; Oro, L. A.; Raithby, P. R. Metal Clusters in Chemistry;

Wiley-VCH: Weinheim, 1999.

(3) Shriver, D. F.; Kaesz, H. D.; Adams, R. D. The Chemistry of Metal Cluster

Complexes; VCH Publishers, Inc.: New York, 1990.

(5) Ros, R.; Tassan, A.; Laurenczy, G.; Roulet, R. Inorg. Chim. Acta 2000,

303, 94.

(6) Dahmen, K. H.; Imhof, D.; Venanzi, L. M. HelV. Chim. Acta 1994, 77,

1029.

(7) Haggit, J. L.; Mingos, D. M. P. J. Organomet. Chem. 1993, 462, 365.

(8) Bradford, A. M.; Payne, N. C.; Puddephatt, R. J.; Yang, D. S.; Marder, T.

B. J. Chem. Soc. Chem. Commun. 1990, 1462.

9

J. AM. CHEM. SOC. 2007, 129, 4551-4566

4551

A R T I C L E S

Albrecht et al.

Scheme 1. General Method for the Synthesis of Acetylplatinum(II)

Complexes 2 and Methylplatinum(II) Complexes 3 Starting from

Platina-â-diketone 1

viously, such bridging ligands are important for the stability,

as has been demonstrated by quantum chemical calculations.¹¹

Furthermore, the presence of bridging ligands has consequences

in terms of the symmetry. Whereas D_3hsymmetry was found

in most of the 42 cve triangular platinum clusters or, at least,

in the cluster cores like in [{Pt(PR₃)}₃(µ-CO)₃], the electronic

and steric effects of the bridging ligands in the 44 cve clusters,

8

such as [Pt₃(CNR)₂(µ-dppm)₃](PF₆)₂or [Pt₃Cl(µ₃-CO)(µ-

dppm)₃]Cl,⁹give rise to a wide variety of geometrical confor-

mations and complex structures. Thus, higher symmetrical 44

cve triangular platinum clusters having C_3Vor D_3hsymmetry

are relatively rare and all are cationic clusters containing

bridging three electron donor µ-PR₂ligands. Such clusters can

be described with the simplified formula [(PtL)₃(µ-PR₂)₃]⁺(L

) PR₃, CO, CNR) or as 3:3:3-type clusters.^12,13Noteworthy,

up to now, no higher symmetrical triangular platinum cluster

containing other bridging three electron donor ligands are

known.

In this paper, we report the syntheses and spectroscopic and

structural characterization of novel C_3Vsymmetrical 44 cve

triangular platinum clusters [(PtL)₃(µ-SR)₃]Cl (4, L ) PR₃, R

) Me-Bu; 8, L ) AsPh₃, R ) Me). Taking advantage of the

robust nature of the Pt-S-Pt bridges,¹⁴the reactivity of these

clusters toward halogens, chalcogens, and phosphines yielding

dinuclear platinum(II) complexes cis-[{PtX(L)}₂(µ-SR)₂] (14,

X ) Br, I), trinuclear chalcogen capped platinum(II) complexes

[(PtL)₃(µ₃-E)(µ-SR)₃]Cl (15, E ) S, Se), and dinuclear platinum-

(I) complexes [(PtL)₂(µ-SR)(µ-dppm)]Cl (12) will be discussed.

Quantum chemical calculations were performed to gain a deeper

understanding of the bonding models in such platinum clusters.

containing the monodendate phosphine ligands PPh₃(2a) and

P(4-FC₆H₄)₃(2b) in boiling chloroform within 2 days. The

addition of Me₂S₂to acetylplatinum(II) complexes containing

the monodendate phosphine ligand PMePh₂(2d) resulted in a

decarbonylation reaction of the acetyl ligand giving the methyl-

(chloro)platinum(II) complex trans-[Pt(Me)Cl(PMePh₂)₂] (3d),

which was also observed in absence of Me₂S₂(Scheme 1, path

b). On the other hand, 2e and 2f, having PMe₂Ph and PBu₃as

ligands, did not react at all. This different reactivity may be

due to the higher donor capability of PMePh₂, PMe₂Ph, and

PBu₃(Tolman’s electronic parameter: PMePh₂, 2067.0 cm^-1

;

PMe₂Ph, 2065.3 cm^-1; PBu₃, 2060.3 cm^-1) compared to PPh₃

and P(4-FC₆H₄)₃(Tolman’s electronic parameter: PPh₃, 2068.9

cm^-1; P(4-FC₆H₄)₃, 2071.3 cm^-1).¹⁶

2. Results and Discussion

In contrast to this, the analogous reaction of 2a-2c with

diphenyldisulfide resulted in the formation of dinuclear plati-

num(II) complexes [{PtCl(L)}₂(µ-SPh)₂] (5) having the ligands

PPh₃(5a), P(4-FC₆H₄)₃(5b), and AsPh₃(5c) in mutual trans

position (Scheme 2, path b). The reaction of 2a with diben-

zyldisulfide yielded after 48 h reaction time the cationic

trinuclear platinum(II) complex [{Pt(PPh₃)}₃(µ₃-S)(µ-SBn)₃]Cl

(6) (Scheme 2, path c). It was proven by ESI-MS measurements

that in the course of the reaction the trinuclear cluster [{Pt-

(PPh₃)}₃(µ-SBn)₃]Cl was also formed to a minor extend. The

complexes 5a-c and 6 were obtained after chromatographic

purification and recrystallization from methylene chloride/n-

pentane (5a), chloroform/n-pentane (5b, 5c), and acetone/n-

pentane (6) as yellow, air-stable crystals in moderate yields (16-

44%).

The treatment of the acetylplatinum(II) complex 2c (L )

AsPh₃) with Me₂S₂showed yet another reactivity yielding the

dinuclear compound [{PtCl(AsPh₃)}₂(µ-SMe)₂] (7) (yield: 44%).

The reaction of Me₂S₂with the mixed triphenylphosphine-

triphenylarsine complex 2g (prepared as shown in Scheme 1,

path c) gave four different triangular platinum clusters, [{Pt-

(PPh₃)}₃(µ-SMe)₃]Cl (4a), [{Pt(AsPh₃)}{Pt(PPh₃)}₂(µ-SMe)₃]-

Cl (8a), [{Pt(AsPh₃)}₂{Pt(PPh₃)}(µ-SMe)₃]Cl (8b), and [{Pt-

(AsPh₃)}₃(µ-SMe)₃]Cl (8c), in the ratio 43% (4a):39% (8a):

15% (8b):3% (8c) (Scheme 3). The identities of clusters 4 as

well as complexes 5, 6, and 7 were confirmed by microanalyses,

¹H, ¹³C, ³¹P NMR spectroscopy, and ESI-MS spectrometry.

The clusters 8 were investigated by means of ¹H and ³¹P NMR

2.1. Reactivity of Acetylplatinum(II) Complexes toward

Diorganodisulfides. We reported earlier that reactions of the

dinuclear platina-â-diketone [Pt₂{(COMe)₂H}₂(µ-Cl)₂] (1) with

phosphine and arsine ligands are very convenient routes for the

preparation of acetylplatinum(II) complexes trans-[PtCl(COMe)-

(L)₂] (2) (Scheme 1, path a).¹⁵

Acetylplatinum(II) complexes 2a/b were found to react with

an excess of dialkyldisulfides (Me₂S₂, Et₂S₂, Pr₂S₂, Bu₂S₂),

yielding novel 44 cve cationic triangular platinum clusters

[(PtL)₃(µ-SR)₃]Cl (4) (Scheme 2, path a). The clusters (4a-e)

were obtained after chromatographic purification and recrys-

tallization from chloroform/n-pentane as yellow, air-stable

crystals in moderate yields (36-56%). In the reaction of 2a

with Me₂S₂, the formation of methyl chloride, S-methylthioac-

etate, and triphenylphosphine sulfide as side products were

confirmed by GC/MS analyses as well as by NMR spectroscopy.

These reactions proceeded with acetylplatinum(II) complexes

(9) Jennings, M. C.; Schoettel, G.; Roy, S.; Puddephatt, R. J.; Douglas, G.;

Manojlovic-Muir, L.; Muir, K. W. Organometallics 1991, 10, 580.

(10) Ramachandran, R.; Payne, N. C.; Puddephatt, R. J. J. Chem. Soc. Chem.

Commun. 1989, 128.

(11) Mingos, D. M. P.; Slee, T. J. Organomet. Chem. 1990, 394, 679.

(12) (a) Falvello, L. R.; Fornie´s, J.; Fortuno, C.; Dura´n, F.; Martin, A.

Organometallics 2002, 21, 2226. (b) Bender, R.; Braunstein, P.; Dedieu,

A.; Ellis, P. D.; Huggins, B.; Harvey, P. D.; Sappa, E.; Tiripicchio, A.

Inorg. Chem. 1996, 35, 1223. (c) Leoni, P.; Marchetti, F.; Pasquali, M.;

Marchetti, L.; Albinati, A. Organometallics 2002, 21, 2176.

(13) Imhof, D.; Venanzi, L. M. Chem. Soc. ReV. 1994, 185.

(14) (a) Hadj-Bagheri, N.; Browning, J.; Dehghan, K.; Dixon, K. R.; Meanwell,

N. J.; Vefghi, R. J. Organomet. Chem. 1990, 396, C47. (b) Mingos, D. M.

P.; Williams, I. D.; Watson, M. J. J. Chem. Soc. Dalton. Trans. 1988, 1509.

(15) Albrecht, C.; Wagner, C.; Merzweiler, K.; Lis, T.; Steinborn, D. Appl.

Organomet. Chem. 2005, 19, 1155.

(16) Tolman C. A. Chem. ReV. 1977, 77, 313.

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4552 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters

A R T I C L E S

Scheme 2. Reactivity of Acetylplatinum(II) Complexes 2 toward Diorganodisulfides; Synthesis of Alkylthio Bridged 44 cve Triangular

Platinum Clusters 4, Dinuclear Arylthio Bridged Platinum(II) Complexes 5, and the Trinuclear Benzylthio Bridged Platinum(II) Complex 6

Scheme 3. Reactivity of Acetylplatinum(II) Complexes 2c and 2g

toward Dimethyldisulfide

2.291(2) Å) are in the common range for platinum complexes

with bridging S-alkyl groups (median 2.327 Å; lower/upper

quartile 2.297/2.363 Å; n ) 16). The Pt-S-Pt angles (78.2-

(1)-79.2(1)°) are remarkably small (other platinum complexes

having bridging S-alkyl groups: Pt-S-Pt median 91.9°; lower/

upper quartile 83.4/95.7°, n ) 24), which indicates a higher

ring strain in the Pt-S-Pt ring in 4a. The methyl groups bonded

to the sulfur atoms are arranged on the same side of the Pt₃-

plane.

spectroscopy as well as by ESI-MS spectrometry. Furthermore,

single-crystal X-ray diffraction analyses were performed for the

compounds 4a, 5c, and 6.

Structural Characterization. Suitable crystals for X-ray

diffraction analysis of the triangular platinum cluster 4a have

been obtained from chloroform/n-pentane solutions as 4a‚

4CHCl₃(space group: P2₁/n). Crystals consist of discrete

cations and anions without unusual intermolecular contacts. The

structure of 4a‚4CHCl₃is shown in Figure 1. Selected bond

lengths and angles are given in the Figure caption.

The Pt₃S₃P₃-skeleton is essentially planar. The largest devia-

tion from the Pt₃plane amounts to 0.145(1) Å (S1). The

arrangement of the platinum atoms approximate to an equilateral

Figure 1. Molecular structure of [{Pt(PPh₃)}₃(µ-SMe)₃]⁺in crystals of

4a‚4CHCl₃with ellipsoids at the 30% probability level and stick model

viewed along the Pt₃S₃plane. H atoms are omitted for clarity. Selected

distances (Å) and angles (deg): Pt1-Pt2 2.901(1), Pt1-Pt3 2.907(1), Pt2-

Pt3 2.887(1), Pt1-P1 2.267(2), Pt2-P2 2.256(2), Pt3-P3 2.253(2), Pt1-

S1 2.288(1), Pt1-S3 2.275(2), Pt2-S1 2.288(1), Pt2-S2 2.291(1), Pt3-

S2 2.287(2), Pt3-S3 2.289(2), S1-C1 1.842(6), S2-C2 1.832(6), S3-C3

1.812(7), Pt1-Pt2-Pt3 60.3(1), Pt1-Pt3-Pt2 60.1(1), Pt2-Pt1-Pt3 59.6-

(1), Pt1-S1-Pt2 78.7(1), Pt1-S3-Pt3 79.1(1), Pt2-S2-Pt3 78.2(1).

triangle (Pt-Pt-Pt 59.6(1)-60.3(1)°) with Pt-Pt distances

between 2.887(1) and 2.907(1) Å. These distances are signifi-

cantly longer than those in other higher symmetrical triangular

platinum clusters (median 2.684 Å; lower/upper quartile 2.619/

2.713 Å; n ) 18).¹⁷The Pt-S bond lengths (Pt-S 2.288(1)-

(17) Cambridge Structural Database (CSD), University Chemical Laboratory,

Cambridge.

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J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007 4553

A R T I C L E S

Albrecht et al.

Figure 2. Molecular structure of [{PtCl(AsPh₃)}₂(µ-SPh)₂] in crystals of

5c‚2CHCl₃with ellipsoids at the 30% probability level. H atoms are omitted

for clarity. Selected distances (Å) and angles (deg): Pt-As 2.378(1), Pt-S

2.349(1), Pt-S′ 2.285(1), Cl-Pt 2.325(1), Cl-Pt-S 91.1(1), S-Pt-S′ 83.7-

(1), S-Pt-As 96.9(1), Cl-Pt-As 88.4(1), Pt-S-Pt 96.3(1).

Figure 3. Molecular structure of [{Pt(PPh₃)}₃(µ₃-S)(µ-SBn)₃]⁺in crystals

of 6‚Me₂CO with ellipsoids at the 30% probability level and stick model

viewed along the Pt₃plane. Phenyl rings of the phosphine ligands and H

atoms are omitted for clarity. Selected distances (Å) and angles (deg): P1-

Pt1 2.262(2), P2-Pt2 2.259(2), P3-Pt3 2.271(2), Pt1-S1 2.343(2), Pt1-

S3 2.350(2), Pt1-S4 2.391(2), Pt2-S1 2.351(2), Pt2-S2 2.356(2), Pt2-

S4 2.394(2), Pt3-S2 2.345(2), Pt3-S3 2.346(2), Pt3-S4 2.390(2), Pt3-

Pt1-Pt2 60.2(1), Pt3-Pt2-Pt1 59.6(1), Pt1-Pt3-Pt2 60.2(1), Pt1-S1-

Pt2 81.4(1), Pt3-S2-Pt2 81.2(1), Pt3-S3-Pt1 80.8(1), Pt3-S4-Pt1

79.1(1), Pt3-S4-Pt2 79.5(1), Pt1-S4-Pt2 79.5(1).

The dinuclear complex 5c crystallized from chloroform/

diethyl ether as 5c‚2CHCl₃in well-shaped yellow crystals that

were suitable for single-crystal X-ray diffraction analysis (space

group: P2₁/n). The crystal consists of discrete centrosymmetric

molecules and is also without unusual intermolecular contacts.

The structure of 5c‚2CHCl₃is shown in Figure 2. Selected bond

lengths and angles are given in the Figure caption.

The Pt₂S₂As₂Cl₂core is approximately planar (largest devia-

tion from the Pt₂S₂-plane: 0.029(1) Å for Cl). The Pt-S bond

length trans to As (Pt-S 2.349(1) Å) reflects the lower trans

influence of the AsPh₃ligand compared to the PPh₃ligand in

5a‚2CHCl₃(Pt-S 2.370(2) Å).¹⁶The internal angles of the

Pt₂S₂-ring (S-Pt-S′ 83.7(1)°, Pt-S-Pt′ 96.3(1)°) are compa-

rable with those found in other dinuclear S-phenyl bridged

platinum(II) complexes (S-Pt-S: median 82.7°; lower/upper

quartile 81.3/82.9°; Pt-S-Pt: median 97.3°; lower/upper

quartile 97.1/97.9°, n ) 8).¹⁸The phenyl rings are situated nearly

perpendicular to the planar Pt₂S₂skeleton (angle between the

Pt₂S₂plane and the S-C1 vector 67.9(2)°) and were found to

be in an anti position relative to the Pt₂S₂frame.

The trinuclear complex 6 crystallized from acetone/n-pentane

solutions as 6‚Me₂CO in well-shaped yellow crystals which were

suitable for single-crystal X-ray diffraction analysis (space

group: P2₁/n). The crystal consists of discrete molecules without

unusual intermolecular contacts. The structure of 6‚Me₂CO is

shown in Figure 3. Selected bond lengths and angles are given

in the Figure caption.

The three platinum atoms span an equilateral triangle (Pt-

Pt-Pt 59.6(1)-60.2(1)°) but the Pt‚‚‚Pt distances in 6‚Me₂CO

are significantly longer (3.044(1)-3.061(1) Å) than in the

corresponding cluster 4a by ca. 0.15 Å. This indicates a different

type of Pt‚‚‚Pt interaction in 6‚Me₂CO compared to clusters 4

as also confirmed by quantum chemical calculations (quod vide

2.4.). The planar Pt₃S₃skeleton (largest deviation: 0.034(1) Å

for Pt1) is capped by a sulfur atom (S4-CP 1.639(2) Å, Pt-

S4-Pt 79.1(1)-79.5(1)°; CP ) Pt₃S₃plane). The Pt-S4 bond

lengths are identical within the 3σ criterion (Pt-S4 2.390(2)-

2.394(2) Å). Furthermore, the triphenylphosphine ligands are

arranged below the Pt₃S₃plane (P-CP 1.284(2)-1.457(2) Å,

S4-Pt1-P1 176.7(1)°, S4-Pt2-P2 172.5(1)°), S4-Pt3-P3

177.1(1)°), whereas the benzyl groups are arranged above this

plane (C1-CP 1.687(9) Å, C8-CP 1.692(9) Å, C15-CP 1.716-

(9) Å). The Pt-S bond lengths of the S-Bn groups (Pt-S

2.343(2)-2.356(2) Å) are longer and the Pt-S-Pt angles (Pt-

S-Pt 80.8(1)-81.4(1)°) are larger than those in cluster 4a (78.2-

(1)-79.2(1)°).

Spectroscopic Characterization. The ³¹P NMR spectra and

their simulation gave clear evidence of the constitution of the

triangular platinum clusters [(PtL)₃(µ-SR)₃]Cl (L ) PPh₃, R )

Me-Bu, 4a-4d; L ) P(4-FC₆H₄)₃, R ) Me, 4e). Due to the

natural abundance of the NMR active platinum isotope (¹⁹⁵Pt,

33.8%, I ) ¹/₂), the ³¹P NMR spectra have to be analyzed as a

superposition of the four spin systems A₃, A₂BX, ABB′XX′,

and AA′A′′XX′X′′ (A, B ) ³¹P; X ) ¹⁹⁵Pt) with central singlet

resonances between -0.4 and 2.8 ppm (4a-4e). The measured

³¹P NMR spectrum and the simulation of each spin system for

the cluster 4a are shown in Figure 4.

The trinuclear clusters 4 have several Pt-Pt, Pt-P, and P-P

2

coupling pathways (e.g., for Pt-Pt: ¹J(Pt-Pt), J(Pt-S-Pt),

n

²J(Pt-Pt-Pt)...; J(Pt,Pt) ) ∑J(Pt,Pt)). Due to the lack of

knowledge concerning the signs as well as the exact determi-

nation of these magnitudes in the following, only the shortest

coupling pathway is given. These coupling constants, illustrated

in Table 1, were obtained by calculation using the PERCH

program package.¹⁹Within the homologous series 4a-4d, a

dependency of the magnitude of the ¹J(Pt,Pt) coupling constant

(18) (a) Rivera, G.; Berne`s, S.; Rodriguez de Barbarin, C.; Torrens, H. Inorg.

Chem. 2001, 40, 5574. (b) Bruhn, C.; Becke, S.; Steinborn, D. Acta

Crystallogr. Sect. C 1998, 1102. (c) Jain, V. K.; Kannan, S.; Butcher, R.

J.; Jasinski, J. P. J. Organomet. Chem. 1994, 468, 285.

(19) (a) Annibale, G.; Bergamini, P.; Bertolasi, V.; Cattabriga, M.; Lazzaro,

A.; Marchi, A.; Vertuani, G. J. Chem. Soc. Dalton Trans. 1999, 3877. (b)

Ma, E.; Semelhago, G.; Walker, A.; Farrar, D. H.; Gukathasan, R. R. J.

Chem. Soc. Dalton Trans. 1985, 2595.

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4554 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters

A R T I C L E S

Figure 4. Observed and simulated ³¹P NMR spectra of [{Pt(PPh₃)}₃(µ-SMe)₃]Cl (4a) along with the spin systems (A, B ) ³¹P; X ) ¹⁹⁵Pt).

Table 1. Selected NMR Data (δ in ppm, J in Hz) for Triangular

Platinum Clusters [(PtL)₃(µ-SR)₃]Cl (4a-4e, 9a-9d)

central singlet resonances at 3.0 ppm (4a), 3.6 ppm (8a), and

4.5 ppm (8b) were obtained. The ¹H NMR spectrum of clusters

8 showed two broad multiplets at 0.86 (superposition of 4a,

8a, 8b) and 1.05 ppm (superposition of 8a, 8b, 8c) in the area

of the methyl protons.

L

R

δ(

³¹P) ¹J(¹⁹⁵Pt,³¹P) ¹J(¹⁹⁵Pt,¹⁹⁵Pt) ²J(¹⁹⁵Pt,³¹P) ³J(³¹P,³¹P)

PPh₃(4a)

PPh₃(4b)

PPh₃(4c)

PPh₃(4d)

Me

Et

Pr

2.8

1.4

1.5

1.4

4220

4240

4235

4280

4096

3956

3930

3942

2100

1950

1930

2250

96

95

97

100

80

81

80

The chemical equivalence of the phosphine ligands in 5a and

5b is evident from the ³¹P NMR spectra showing multiplets

with central singlet resonances at 19.3 ppm for 5a and 15.8

ppm for 5b. The Pt-Pt, Pt-P, and P-P coupling constants

Bu

P(4-FC₆H₄)₃(4e) Me -0.4

PMePh₂(9a)

PMe₂Ph (9b)

PBu₃(9c)

Me -16.4

Me -28.9

Me -7.2

1900

85

75

a

1855

1810

65

67

71

2

3

(¹J(Pt,P) ) 3395/3303 Hz, J(Pt,Pt) ) 920/1230 Hz, J(Pt,P)

) -24/-39 Hz, ⁴J(P,P) ) 12/14 Hz; 5a/5b) were obtained by

calculation of the ABX and AA′XX′ (A, B ) ³¹P; ¹⁹⁵X ) Pt)

spin systems. The magnitudes of the ²J(Pt,Pt) coupling constants

were found to be positive, whereas the ³J(Pt,P) coupling

constants were found to be negative, as expected. In general,

PBu₃(9d)

Et

-8.1

^aFor intensity reasons, these coupling constants could not be obtained.

on the nature of the bridging sulfur ligand was found (¹J(Pt,-

Pt): 2100 (4a, µ-SMe)-1930 Hz (4d, µ-SBu)). The signals for

the SCH₃protons of 4a and 4e should also be treated as the

superposition of four spin systems. Temperature-dependent

NMR measurements up to -50 °C gave no indication for an

inversion of methyl groups at sulfur in complex 4a.

The Pt-H coupling constants (³J(Pt,H) ) 43.6/42.7 Hz; 4a/

4e) are comparable with those found in S-methyl bridged

dinuclear platinum complexes.^20,21The carbon resonances of

the methyl groups in 4a and 4e were found at 17.5 ppm (4a)

and 18.4 ppm (4e) whereas the R-CH₂groups in 4b-4d resonate

between 30.6 and 37.2 ppm.

To characterize the mixture of clusters [{Pt(AsPh₃)}{Pt-

(PPh₃)}₂(µ-SMe)₃] (8a), [{Pt(AsPh₃)}₂{Pt(PPh₃)}(µ-SMe)₃] (8b),

and [{Pt(AsPh₃)}₃(µ-SMe)₃]Cl (8c) (Scheme 3), ESI-MS, ¹H,

and ³¹P NMR measurements were performed. The ESI-MS

spectrum in the region of the isotopic patterns of the molecular

cations indicated the presence of four clusters having mass

differences of ∆m ) 44 amu (difference of the most intensive

mass peaks [M]⁺). This shows clearly the formation of 4a

(43%), 8a (39%), 8b (15%), and 8c (3%), see Figure 5.

In the ³¹P NMR spectrum, three multiplets (superposition of

³¹P/¹⁹⁵Pt spin systems, analogous to that described above) with

2

the sign of the J(Pt,Pt) is mostly but not necessarily always

3

positive whereas the sign of the J(Pt,P) is negative.^22,23The

trans arrangement of the arsine ligands in 5c and 7 follows from

the ¹³C NMR spectra especially from the isochronism of the

carbon atoms of the two SPh groups in 5c (δ_C) 128.5, m-CH;

130.5, p-CH; 131.0, i-C; 134.4, o-CH ppm) and of the two SCH₃

groups in 7 (δ_C) 19.0 ppm).

In the case of the sulfur capped trinuclear complex 6, the

identity was not only proven by a single-crystal X-ray diffraction

measurement but also by NMR spectroscopic investigations. The

³¹P NMR spectrum of 6 is treated as a superposition of four

spin systems (A₃, A₂BX, ABB′XX′, AA′A′′XX′X′′; A, B )

³¹P; ¹⁹⁵X ) Pt) with a central singlet at 8.3 ppm. Coupling

constants (¹J(Pt,P) ) 3800 Hz, ²J(Pt,Pt) ) 458 Hz, ³J(Pt,P) )

-38 Hz, ⁴J(P,P) ) 6 Hz) were obtained by calculation.

Remarkably, the magnitude of the Pt-Pt coupling constant (458

Hz) is much smaller than those in clusters 4 (1930-2250 Hz).

This reflects clearly the different electronic nature as well as

the bonding situation in compound 6 compared to clusters 4.

However, it has to be mentioned that the magnitudes of the

(22) (a) Kennedy, J. D.; McFarlane, W.; Puddephatt, R. J. J. Chem. Soc. Dalton

Trans. 1976, 745. (b) Kennedy, J. D.; Colquhoun, I. J.; McFarlane, W.;

Puddephatt, R. J. J. Organomet. Chem. 1979, 172, 479.

(23) Pregosin, P. S. Studies in Inorganic Chemistry 13, Transition Metal Nuclear

Magnetic Resonance; Elsevier: New York, 1991.

(20) PERCH-NMR-Software, 1993-2000 University of Kuopio, Version 1/2000.

(21) (a) Briant, C. E.; Gardner, C. J.; Hor, A. T. S.; Howells, T. S. N. G.; Mingos,

D. M. P. J. Chem. Soc. Dalton Trans. 1984, 2645. (b) Brown, M. P.;

Puddephatt, R. J.; Upton, C. E. E. J. Chem. Soc. Dalton Trans. 1976, 2490.

9

J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007 4555

A R T I C L E S

Albrecht et al.

Figure 5. ESI-mass spectrum in MeOH from the reaction mixture of [Pt(COMe)Cl(AsPh₃)(PPh₃)] (2g) with Me₂S₂in the area of [M]⁺(formation of

[{Pt(AsPh₃)}{Pt(PPh₃)}₂(µ-SMe)₃] (8a), [{Pt(AsPh₃)}₂{Pt(PPh₃)}(µ-SMe)₃] (8b), [{Pt(AsPh₃)}₃(µ-SMe)₃]Cl (8c), and [{Pt(PPh₃)}₃(µ-SMe)₃]Cl (4a)) as well

as measured and calculated isotopic patterns of the cation of 4a in the [M]⁺region (* ) impurity).

Scheme 4. Substitution and Degradation Processes of Alkylthio Bridged 44 cve Triangular Platinum Clusters 4 in the Reactions with

Phosphines

Pt-Pt coupling constants cannot be considered as an argument

for a bond between the platinum atoms and in any event they

do not correlate well with Pt-Pt distances.²³

tation from methylene chloride/n-pentane as a yellow powdery

substance in moderate yields (48%, 9c; 62% 9d; 60%, 10c).

When the ligand substitution reaction is performed with a

deficiency of PMePh₂(4a: PMePh₂) 1:1), some of the starting

cluster 4a remained in solution whereas both the partially

substituted clusters 11a and 11b as well as the fully substituted

cluster 9a were formed (Scheme 4, path b). The constitutions

of all clusters (9, 11) as well as the dinuclear complexes 10

were revealed by NMR spectroscopy (¹H, ¹³C, ³¹P) and ESI-

MS spectrometry.

2.2. Reactivity of Triangular Platinum Clusters toward

Phosphine Ligands. Triangular platinum clusters containing

the monodentate phosphines PMePh₂, PMe₂Ph, and PBu₃could

not be prepared using the standard reaction procedure according

to Scheme 2, path a. Therefore, we investigated whether clusters

4 are prone to ligand substitution. In fact, triangular platinum

clusters [{Pt(PPh₃)}₃(µ-SR)₃]Cl (R ) Me, 4a; R ) Et, 4b) were

found to react with three equivalents of PMePh₂, PMe₂Ph, and

PBu₃in chloroform at -70 °C, yielding a dark-red solution that

changed color immediately to yellow upon warming to room

temperature. ¹H and ³¹P NMR measurements showed a complete

substitution of the PPh₃ligands yielding clusters [(PtL′)₃(µ-SR)₃]-

Cl (R ) Me, L′ ) PMePh₂, 9a; PMe₂Ph, 9b; PBu₃, 9c; R ) Et,

L ) PBu₃, 9d) (Scheme 4, path a).

These ligand substitution reactions are accompanied by partial

degradation of the trinuclear clusters yielding dinuclear com-

plexes [(PtL₂)₂(µ-SMe)₂]Cl₂(L ) PMePh₂, 10a; PMe₂Ph, 10b;

PBu₃, 10c). The formation of the fully substituted clusters 9a

and 9b as well as the formation of dinuclear complexes 10a

and 10b was proved by NMR spectroscopy, whereas clusters

9c and 9d were isolated as yellow oils after chromatographic

purification, and the complex 10c was obtained after reprecipi-

In contrast to this, the addition of the bidentate phosphine

ligand PPh₂CH₂PPh₂(dppm) to a solution of clusters 4 and 9

in methylene chloride at -70 °C resulted in a fragmentation

reaction yielding the cationic dinuclear platinum(I) complexes

[(PtL)₂(µ-SMe)(µ-dppm)]Cl (12) (L ) PPh₃, 12a; P(4-FC₆H₄)₃,

12b; PBu₃, 12c), and the Pt(II) complex [Pt(SMe)₂(dppm)] (13)

(Scheme 4, path c). These complexes were obtained after

chromatographic purification as yellow crystals (12a, 12b),

yellow oil (12c), and light-yellow crystals (13), respectively.

1

The identities of 12 and 13 were proven by H, ¹³C, and ³¹P

NMR spectroscopy as well as single-crystal X-ray diffraction

analysis in the case of 12a.

Structural and Spectroscopic Characterization. The ³¹P

NMR spectra of the fully substituted triangular platinum clusters

[(PtL′)₃(µ-SR)₃]Cl (R ) Me, L′ ) PMePh₂, 9a; PMe₂Ph, 9b;

9

4556 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters

A R T I C L E S

Figure 6. ESI-mass spectrum in CH₂Cl₂from the reaction mixture of

[{Pt(PPh₃)}(µ-SMe)₃]Cl (4a) and 1 equiv PMePh₂in the [M]⁺region

(measured 1 min after starting). The partially substituted clusters [{Pt-

(PMePh₂)}{Pt(PPh₃)}₂(µ-SMe)₃] (11a), [{Pt(PMePh₂)}₂{Pt(PPh₃)}(µ-

SMe)₃] (11b), and the fully substituted cluster [{Pt(PMePh₂)}₃(µ-SMe)₃]Cl

(9a) were formed.

Figure 7. Molecular structure of [{Pt(PPh₃)}₂(µ-SMe)(µ-dppm)]⁺in

crystals of 12a with ellipsoids at the 30% probability level and stick model

viewed along the Pt₂P₄S plane. H atoms are omitted for clarity. Selected

distances (Å) and angles (deg): Pt1-Pt2 2.633(1), Pt1-P1 2.298(2), Pt1-

P3 2.245(2), Pt2-P2 2.289(2), Pt2-P4 2.243(2), Pt1-S 2.297(2), Pt2-S

2.315(2), S-C1 1.802(8), P3-C2 1.821(8), P4-C2 1.840(8), P3-C2-P4

111.6(4), Pt1-S-Pt2 69.6(1).

PBu₃, 9c; R ) Et, L ) PBu₃, 9d) are quite similar to those of

clusters 4. Central singlet resonances were found between -28.9

and -7.2 ppm (9a-9e). Magnitudes of Pt-Pt, Pt-P, and P-P

coupling constants, which were obtained by calculation of the

A₃, A₂BX, ABB′XX′, and AA′A′′XX′X′′ (A, B ) ³¹P; X )

¹⁹⁵Pt) spin systems, are also given in Table 1. To characterize

the products in the reaction of 4a with one equivalent PMePh₂,

³¹P NMR spectroscopy and ESI-MS measurements were

performed. In the ³¹P NMR spectrum, two central singlet

resonances at -16.8 (9a, 11) and 3.0 (4a, 11) ppm were

obtained. The ESI-MS spectrum of the reaction mixture in the

region of the isotopic patterns of the molecular cations is shown

in Figure 6. This indicates clearly that during the course of the

reaction three clusters in the ratio 38% (11a):17% (11b):3%

(9a) were formed (∆m ) 62 amu), whereas 42% of the starting

material 4a remained in solution.

quartile 2.580/2.707 Å).²⁴The Pt-S-Pt-angle in 12a is

significantly smaller than those in 4a (69.6(1)°, 12a; 78.2(1)-

79.2(1)°, 4a). The P-C-P-angle of the dppm in 12a (111.6-

(4)°) is enlarged by the bridging coordination mode compared

to that of the uncoordinated dppm (106.2(1)°).²⁵

Furthermore, NMR spectroscopic measurements provided

clear evidence of the constitution of the dinuclear platinum(I)

complexes 12. The ³¹P NMR spectra of 12 are treated as a

superposition of the three spin systems AA′MM′, ABMNX, and

AA′MM′XX′ (A, B, M, N ) ³¹P; X ) ¹⁹⁵Pt). The ³¹P NMR

spectrum of the dinuclear platinum(I) complex 12c as well as

the simulation of these spin systems are shown in Figure 8.

Magnitudes of the Pt-Pt, Pt-P, and P-P coupling constants

were obtained by calculation. Selected NMR data for all

dinuclear platinum(I) complexes 12 are given in Table 2.

The identities of the dinuclear complexes [(PtL₂)₂(µ-SMe)₂]-

Cl₂(L ) PMePh₂, 10a; PMe₂Ph, 10b; PBu₃, 10c) follow from

the chemical equivalence of the phosphine ligands in the ³¹P

NMR spectra (centered singlet resonances between -9.7 and

7.5 ppm) and from the resonances of the SCH₃group in the ¹H

NMR spectra.

2

3

Remarkably, all magnitudes of the J(Pt,P*) and J(P,P^#) cou-

pling constants (P^*) dppm, P^#) L) are negative (²J(Pt,P*) )

-90 to -85 Hz; J(P,P^#) ) -21 to -16 Hz), whereas the

3

magnitudes of the geminal-cis ²J(P*,P^#) and the ²J(P*,P*)

coupling constants are positive (²J(P*,P^#) ) 10-13 Hz;

²J(P*,P*) ) 25-40 Hz). The Pt-Pt coupling constants (¹J(Pt,-

Pt) ) 2380-2850 Hz) are larger than those obtained in clusters

4 and 9 with R ) Me (¹J(Pt,Pt) ) 1810-2250 Hz). The

assignment of the resonances is based on the fact that for all

three complexes (12a-12c) the chemical shifts of the dppm

signals (δ_P: -5.7 to -3.7 ppm) lie in a very narrow range

whereas the resonances of the monodentate phosphine ligands

were found between 3.5 and 21.9 ppm depending on the type

of ligands. This is further confirmed by the magnitudes of the

¹J(Pt,P) coupling constants being between 3875 and 3925 Hz

Unambiguous proof of the constitution of the dinuclear

platinum(I) complexes [(PtL)₂(µ-SMe)(µ-dppm)]Cl (12) (L )

PPh₃, 12a; P(4-FC₆H₄)₃, 12b; PBu₃12c) was acquired by NMR

spectroscopy and X-ray diffraction measurements. Suitable

crystals for X-ray diffraction analysis of 12a have been obtained

from chloroform/n-pentane solutions (space group: P2₁/n). The

crystal structure of the cation of 12a is shown in Figure 7.

Selected bond lengths and angles are given in the Figure caption.

This crystal consists of discrete [{Pt(PPh₃)}₂(µ-SMe)(µ-

dppm)]⁺cations and chloro anions without unusual intermo-

lecular contacts. The Pt₂P₄S skeleton is in good approximation

to a planar arrangement. The largest deviation from the Pt₂P₄S

plane (CP) amounts to 0.099(2) Å (P2). The carbon atoms C1

and C2 are arranged on the same side of this plane (C1-CP

1.574(8) Å, C2-CP 0.721(9) Å). The Pt-Pt bond in 12a (2.633-

(1) Å) is shorter than those in 4a (2.887(1)-2.907(1) Å) but

comparable with Pt-Pt distances in other dppm bridged

platinum(I) complexes (Pt-Pt: median 2.648 Å, lower/upper

(24) (a) Yip, H. K.; Che, C. M.; Peng, S. M. J. Chem. Soc. Dalton Trans. 1993,

179. (b) Hong, X.; Yip, H. K.; Cheung, K. K.; Che, C. M. J. Chem. Soc.

Dalton Trans. 1993, 815. (c) Khan, M. N. I.; King, C.; Wang, J. C.; Wang,

S.; Fackler, J. P., Jr. Inorg. Chem. 1989, 28, 4656. (d) Blau, R. J.; Espenson,

J. H.; Kim, S.; Jacobson, R. A. Inorg. Chem. 1986, 25, 757. (e) Manojlovic-

Muir, L.; Muir, K. W.; Solomun, T. Acta Crystallogr. B 1979, 35, 1237.

(f) Manojlovic-Muir, L.; Muir, K. W.; Solomun, T. J. Organomet. Chem.

1979, 179, 479. (g) Brown, M. P.; Fisher, J. R.; Manojlovic-Muir, L.; Muir,

K. W.; Puddephatt, R. J.; Thomson, M. A.; Seddon, K. R. Chem. Commun.

1979, 931.

(25) Schmidbaur, H.; Reber, G.; Schier, A.; Wagner, F. E.; Mu¨ller, G. Inorg.

Chim. Acta 1988, 147, 143.

9

J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007 4557

A R T I C L E S

Albrecht et al.

Figure 8. Observed and simulated ³¹P NMR spectra of [{Pt(PBu₃)}₂(µ-SMe)(µ-dppm)]Cl (12c) along with the spin systems (A, B, M, N ) ³¹P; X ) ¹⁹⁵Pt).

Table 2. Selected NMR Data (δ in ppm, J in Hz) for Dinuclear

Platinum(I) Complexes [(PtL)₂(µ-SMe)(µ-dppm)]Cl (12) (P* )

dppm, P^#) L)

Scheme 5. Reactivity of Alkylthio Bridged 44 cve Triangular

Platinum Clusters 4 toward Halogens and Chalcogens

δ(

³¹P)

L

δ

(

³¹P)

dppm ¹J(Pt,Pt) ¹J(Pt,P^#) ¹J(Pt,P^*) ²J(P^*,P^#) ²J(P^*,P^*) ³J(P^#,P^#)

L

PPh₃(12a) 21.9 -3.9 2770

P(4-FC₆H₄)₃19.9 -3.7 2850

(12b)

3010

3055

3880

3875

10

13

40

30

160

170

PBu₃(12c)

7.3 -5.7 2380

2948

3925

10

25

150

for dppm (for comparison [{Pt(PPh₃)}₂(µ-SMe)(µ-dppm)]I:

3896 Hz) as well as between 2948 and 3055 Hz for the terminal

P-ligands ([{Pt(PPh₃)}₂(µ-SMe)(µ-dppm)]I: 3040 Hz).²⁶

The resonances of the SCH₃groups of 12 (δ_H: 1.31-2.66

ppm, δ_C: 22.1-23.9 ppm) as well as the magnitudes of the

³J(Pt,H) coupling constants (41.5-43.6 Hz) lie within the

narrow range found for other S-methyl bridged dinuclear

platinum complexes.^19,21

2.3. Oxidation Reactions of Triangular Platinum Clusters

with Halogens and Chalcogens. To investigate the reactivity

of the triangular platinum clusters 4 toward halogens and

chalcogens the cluster 4a was treated with bromine, iodine,

sulfur, and selenium, respectively. The subsequent purification

using preparative centrifugal thin layer chromatography re-

vealed, in the case of halogens (X₂) Br₂, I₂), the formation of

the dinuclear platinum(II) complexes [{PtX(PPh₃)}₂(µ-SMe)₂]

(14) (Scheme 5, path a) and, in the case of chalcogens (E ) S,

Se), the trinuclear platinum(II) complexes [{Pt(PPh₃)}₃(µ₃-E)-

(µ-SMe)₃]Cl (15) (Scheme 5, path b). The oxidation of 4a with

halogens proceeded in methylene chloride at -70 °C by slowly

adding a solution of the requisite halogen in methylene chloride,

whereas the oxidation with chalcogens required higher temper-

atures. These reactions were performed in benzene at 70 °C

over a period of 2 days. The constitution of all complexes was

unambiguously proved by NMR (¹H, ¹³C, and ³¹P) and IR

spectroscopy, microanalyses, and for 15 also by ESI-MS

1

In the H NMR spectra of the complexes 12, broad singlet

resonances between 2.27 and 2.38 ppm were found in the area

of the PPh₂CH₂PPh₂groups. Due to the chemical inequivalence

of these protons and the superposition of three highly complex

spin systems (ABMM′OO′, ABMNOPX, ABMM′OO′XX′; A,

1

B ) H, M, N, O, P ) ³¹P, X ) ¹⁹⁵Pt), the coupling constants

could not be obtained.

The identity of [Pt(SMe)₂(dppm)] (13) follows from the

singlet resonances in the ³¹P NMR spectrum at -47.0 ppm and

from the triplet pattern of the SCH₃protons (⁴J(P,H) ) 5.0 Hz)

1

in the H NMR spectrum, respectively. The resonance of the

PPh₂CH₂PPh₂group in 13 exhibited a triplet pattern at 4.28

ppm (²J(P,H) ) 10.4 Hz), which indicates the chemical

equivalence of these protons in solution.

(26) Hunt, C. T.; Matson, G. B.; Balch, A. L. Inorg. Chem. 1981, 20, 2270.

9

4558 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters

A R T I C L E S

Figure 10. Calculated structures of the cations [{Pt(PPh₃)}₃(µ-SMe)₃]⁺

(4a′) and [{Pt(PPh₃)}₃(µ₃-S)(µ-SMe)₃]⁺(15a′). Selected distances (Å) and

angles (deg) for 4a′/15a′: Pt-Pt′ 2.933/3.134, Pt-S1 2.314/2.383, Pt-S1′

2.325/2.387, Pt1-S2 -/2.402, Pt-P 2.276/2.281, S-C 1.830/1.826, Pt-

Pt′-Pt′′ 60.0/60.0, Pt-S1-Pt′ 78.4/82.1, Pt-S2-Pt′ -/81.4, S1-Pt-Pt′

50.6/49.0, Pt′′-Pt-S1′′ 50.9/48.9, S1-Pt-S2 -/83.2, S2-Pt-S1′′ -/83.1,

S1′′-Pt-P 100.0/96.0, P-Pt-S1 98.5/99.0.

Figure 9. Molecular structure of [{PtBr(PPh₃)}₂(µ-SMe)₂] in crystals of

14a‚CH₂Cl₂with ellipsoids at the 30% probability level and stick model

viewed along the S1‚‚‚S2 axis. H atoms are omitted for clarity. Selected

distances (Å) and angles (deg): Pt1-P1 2.267(2), Pt2-P2 2.267(2), Pt1-

Br1 2.460(1), Pt2-Br2 2.429(1), Pt1-S1 2.295(2), Pt1-S2 2.372(2), Pt2-

S1 2.288(2), Pt2-S2 2.374(2), S1-C1 1.913(9), S2-C2 1.809(9), P1-

Pt1-Br1 92.0(1), P2-Pt2-Br2 96.3(1), S1-Pt1-S2 79.1(1), S1-Pt2-

S2 79.2(1), Pt1-S1-Pt2 90.2(1), Pt1-S2-Pt2 86.3(1).

Table 3. Selected NMR Data (δ in ppm, J in Hz) for Trinuclear

Platinum Complexes [{Pt(PPh₃)}₃(µ₃-E)(µ-SR)₃]Cl (6, 15a, and

15b)

E

R

δ(

³¹P)

¹J(¹⁹⁵Pt,³¹P)

²J(¹⁹⁵Pt, ¹⁹⁵Pt)

³J(¹⁹⁵Pt,³¹P)

³J(³¹P,³¹P)

S (6)

S (15a)

Se (15b) Me

Bn

Me

8.3

8.7

5.9

3800

3808

3937

458

480

400

-40

-38

6

5

spectrometry. Furthermore, for the compound 14b a single-

crystal X-ray diffraction analysis was performed.

4

the J(P,P) in 14 compared to those found in 5 clearly show

the cis arrangement of the phosphine ligands in 14.

Structural and Spectroscopic Characterization. Suitable

crystals for X-ray diffraction analysis of 14a have been obtained

from methylene chloride/n-pentane solutions as 14a‚CH₂Cl₂

(space group: P1h). This crystal consists of discrete molecules

without unusual intermolecular contacts. The structure of the

dinuclear complex 14a‚CH₂Cl₂revealed a hinged square-planar

geometry (Figure 9). Selected bond lengths and angles are given

in the Figure caption.

The coordination geometry about each platinum center is in

good approximation with a square planar arrangement (sum of

angles: Pt1 360.1°, Pt2 360.0°; angles between neighbored

ligands: Pt1 79.1(1)-95.8(1), Pt2 79.2(1)-96.3(1)°). The Pt-

Br bond lengths (Pt1-Br1 2.460(1), Pt2-Br2 2.429(1) Å) are

as long as those in other platinum complexes having sulfur

ligands in mutually trans positions (median 2.452 Å; lower/

upper quartile 2.426/2.470 Å; n ) 62). The Pt1-S1‚‚‚S2-Pt2

dihedral angle (129.2(1)°) is a measure of the hinge distortion.

In similar dinuclear complexes, the hinge distortions were found

between 124 and 148°.²⁷The bridging sulfur atoms in 14a‚

CH₂Cl₂are tetrahedral; the methyl groups have an anti type

geometry.

Selected NMR data of complexes 15 are shown in Table 3.

The ³¹P NMR spectra of 15 must be analyzed as a superposition

of four spin systems (A₃, A₂BX, ABB′XX′, AA′A′′XX′X′′; A,

B ) ³¹P; X ) ¹⁹⁵Pt) with centered signals at 8.7 (15a) and 5.9

ppm (15b). The obtained coupling constants (¹J(Pt,P) ) 3808/

3937 Hz, J(Pt,Pt) ) 480/400 Hz, J(Pt,P) ) -40/-38 Hz,

⁴J(P,P) ) 6/5 Hz; 15a/15b) are quite similar to those obtained

for complex 6.

2

3

2.4. Theoretical Calculations. The cations of complexes 4a

([{Pt(PPh₃)}₃(µ-SMe)₃]⁺, 4a′) and 15a ([{Pt(PPh₃)}₃(µ₃-S)(µ-

SMe)₃]⁺, 15a′) have been calculated on the DFT level of theory

to understand the nature of bonding in the two different Pt₃

complexes. The calculated structures of 4a′ and 15a′ are shown

in Figure 10. Selected bond lengths and angles are given in the

Figure caption.

In the case of complex 4a, structural data was available as a

starting point and for comparison of the final structural

parameters to judge the quality of calculations. The calculated

and experimental structures were found to be in good agreement

(largest deviation from Pt-Pt: 0.046 Å; Pt-S: 0.037 Å; Pt-

P: 0.023 Å). In the case of compound 15a, no crystal structure

was available for direct comparison, but the similar trinuclear

complex [{Pt(PPh₃)}₃(µ₃-S)(µ-SBn)₃]⁺(6) has been structurally

characterized. Nevertheless, bond lengths and angles of the core

of both structures are in good agreement.

Furthermore, the constitution and the geometry of complexes

14 is evident from the two resonances of the SCH₃group in

1

the H NMR (d_H: 2.67, 2.77 ppm, 14a; 2.75, 3.06 ppm, 14b)

as well as in the ¹³C NMR spectra (δ_C: 14.4, 19.1 ppm, 14a;

10.1, 19.0 ppm, 14b). The chemical equivalence of the phos-

phine ligands is evident from the centered singlet resonances

in the ³¹P NMR spectrum (14.8/14.9 ppm 14a/14b). Magnitudes

of the Pt-P and P-P coupling constants (¹J(Pt,P) ) 3298/3239

Hz, ²J(Pt,Pt) ) 820/960 Hz, ³J(Pt,P) ) -2 Hz/-2 Hz, ⁴J(P,P)

) 7/8 Hz; 14a/14b) were obtained by calculation of the ABX

and AA′XX′ (A, B ) ³¹P; X ) ¹⁹⁵Pt) spin systems using the

PERCH program package. Remarkably, the smaller values of

The topological analysis of the electronic charge density F(r)

using the quantum theory of atoms in molecules (QTAIM)

revealed a distinct difference regarding the Pt‚‚‚Pt interaction

in the two cations 4a′ and 15a′. The trajetories of F(r) of the

molecules including bond paths, bond critical points (bcp’s),

and ring critical points (rcp’s) are shown in Figure 11. In

complex 4a′ (Figure 11, left) bcp’s could be found between the

metal centers. In addition, there were found rcp’s in each of

the Pt-Pt′-S rings and in the central Pt-Pt′-Pt′′ ring. In sharp

(27) (a) Chong, S. H.; Tjindrawan, A.; Hor, T. S. A. J. Mol. Catal. A 2003,

204, 267. (b) Mas-Balleste, R.; Capdevila, M.; Champkin, P. A.; Clegg,

W.; Coxall, R. A.; Lledos, A.; Megret, C.; Gonzalez-Duarte, P. Inorg. Chem.

2002, 41, 3218. (c) Jones, W. D.; Reynolds, K. A.; Sperry, C. K.; Lachicotte,

R. J.; Godleski, S. A.; Valente, R. R. Organometallics 2000, 19, 1661.

9

J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007 4559

A R T I C L E S

Albrecht et al.

Scheme 6. Survey Summary of the Synthesis and Reactivity of Alkyl-/Arylthio Bridged Di- and Trinuclear Platinum Complexes and Clusters

contrast, no bcp between the Pt atoms could be found in 15a′

(Figure 11, right).

reactions. The platinum atoms in 4 exhibit the mean oxidation

state +4/3; thus, they can be regarded formally in the oxidation

state 1 × Pt^II+ 2 × Pt^I. In reactions of the acetyl complexes

2 with Ph₂S₂, the dinuclear arylthio bridged platinum(II)

complexes 5 and S-phenylthioacetate as side products were

received (Scheme 6, path b). Alternatively, Bn₂S₂was found

to react directly yielding the trinuclear sulfur capped platinum-

(II) complex 6 (Scheme 6, path c).

The values found at the bond critical points show typical

behavior for bonds incorporating heavy atoms.²⁸The electron

density is small, the Laplacian positive and small, G/F < 1,

and H/F < 0. The high bond ellipticity (ꢀ ) 4.252) at the Pt-

Pt bcp’s in 4a′ with the major axis parallel to the ring system

suggests a strong delocalization of electron density in the plane

of the ring system. The fact that the rcp’s of the Pt-Pt′-S rings

are in close vicinity to the Pt-Pt bond critical point indicates

that the structure is close to a bifurcation catastrophe point

(coalescence of bcp and rcp).²⁹

Although the mechanism of these reactions has not yet been

investigated, a tentative path of formation can be given (Scheme

7).

Formation of Complexes 5 (Scheme 6, path b). The first

step in the formation of 5 is probably the associative substitution

of a phosphine ligand L by the disulfide R₂S₂(2 f 17). In

accordance with this, complexes 2 containing stronger donating

phosphine ligands L like PMePh₂, PMe₂Ph, and PBu₃do not

react at all, most likely because the ligand substitution (2 f

17) is hampered. The second step, an oxidative S-S addition

of the disulfide could take place resulting in a platinum(IV)

intermediate (17 f 18) followed by a reductive C-S elimination

of MeCOSR yielding the dinuclear complexes 5/7 (18 f 5/7).

For all these reactions, examples with other platinum complexes

were described.^30,31

Figure 11. Gradient paths of electron density F(r) in the calculated

structures of the cations 4a′ and 15a′ (b bond critical point {3, -1}, O

(grey) ring critical point {3, 1}).

Formation of 44 cve Clusters 4 (Scheme 6, path a). There

are indications that dinuclear complexes of type 5/7 may also

2.5 Discussion. In the scope of the work presented here, the

synthesis of di- and trinuclear alkyl/arylthio bridged platinum

complexes and clusters (Scheme 6, path a-c) and the reactivity

of these clusters toward halogens, chalcogens, and phosphines

(Scheme 6, path d-g) were explored. The triangular 44 cve

platinum clusters 4 were obtained in reactions of 2 with

dialkyldisulfides (Scheme 6, path a). Alkyl chloride, S-alkyl-

thioacetate, dialkyl sulfide, and triphenylphosphine sulfide (in

the case of 2a) were identified as side products in all of these

(30) (a) Treichel, P. M.; Rosenhein, L. D. Inorg. Chem. 1984, 23, 4018. (b)

Berg, J. M.; Spira, D. J.; Hodgson, K. O.; Bruce, A. E.; Miller, K. F.;

Corbin, J. L.; Stiefel, E. I. Inorg. Chem. 1984, 23, 3412. (c) Treichel, P.

M.; Rosenhein, L. D.; Schmidt, M. S. Inorg. Chem. 1983, 22, 3960. (d)

Treichel, P. M.; Rosenhein, L. D. J. Am. Chem. Soc. 1981, 103, 691. (e)

Stiefel, E. I.; Miller, K. F.; Bruce, A. E.; Corbin, J. L.; Berg, J. M.; Hodgson,

K. O. J. Am. Chem. Soc. 1980, 102, 3624. (f) Sigel, H.; Scheller, K. H.;

Rheinberger, V. M.; Fischer, B. E. J. Chem. Soc. Dalton Trans. 1980, 1022.

(31) (a) McKarns, P. J.; Heeg, M. J.; Winter, C. H. Inorg. Chem. 1998, 37,

4743. (b) Lewkebandara, T. S.; McKarns, P. J.; Haggerty, B. S.; Yap, G.

P. A.; Rheingold, A. L.; Winter, C. A. Polyhedron 1998, 17, 1. (c) Boorman,

P. M.; Merrit, C. L.; Nandana, W. A. S.; Richardson, J. F. J. Chem. Soc.

Dalton Trans. 1986, 1251. (d) Roesky, H. W.; Gries, T.; Jones, P. G.;

Weber, K.-L.; Sheldrick, G. M. J. Chem. Soc. Dalton Trans. 1984, 1781.

(e) Boorman, P. M.; Kerr, K. A.; Kydd, R. A.; Moynihan, K. J.; Valentine,

K. A. J. Chem. Soc. Dalton Trans. 1982, 1401.

(28) Macchi, P.; Sironi, A. Coord. Chem. ReV. 2003, 238-239, 383.

(29) Bader, R. F. W. Chem. ReV. 1991, 91, 893.

9

4560 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters

A R T I C L E S

Scheme 7. Proposed Mechanism for the Formation of Dinuclear Alkyl-/Arylthio Bridged Complexes 5/7, Triangular Clusters 4, and

Trinuclear Complexes 6/15

be intermediates in the formation of triangular clusters 4: It

was shown that in the reaction of the dinuclear alkylthio bridged

complex 7 (R ) Me, L ) AsPh₃) with PPh₃and Me₂S₂samong

other complexessthe triangular cluster 4a (R ) Me, L ) PPh₃)

was also formed. Furthermore, MeCOSR is also yielded in the

formation of complexes 4. The side product RCl could be

formed in a reduction step 5/7 (2 × Pt^II) f 4 (1 × Pt^II+ 2 ×

Pt^I).

Whereas 4a was found to react with chalcogens in an

oxidation reaction preserving the Pt₃S₃core [4a (1 × Pt^II+ 2

× Pt^I) f 15 (3 × Pt^II)] (Scheme 6, path d), halogens were found

to react with 4a by oxidation coupled with degradation yielding

the dinuclear platinum(II) complexes 14 (Scheme 6, path g).

The structure of 14a showed a hinge distortion of the central

Pt₂S₂ring (dihedral angle: 129.2(1)°). In contrast to the planar

dinuclear Pt^IIcomplexes 5, complex 14a might be stabilized

by an intramolecular closed shell Pt ‚‚‚Pt (d_z-d_z) interactions

(Pt‚‚‚Pt 3.271(1) Å). Lledo´s and Alvarez showed by means of

quantum chemical calculations with similar dinuclear platinum

complexes that depending on the electronic and steric properties

of the terminal ligands such closed shell interactions occur.³⁴

Formation of the Trinuclear Complexes 6/15 (Scheme 6,

path c, d). It is conceivable that the formation of complex [{Pt-

(PPh₃)}₃(µ₃-S)(µ-SBn)₃]Cl (6) in the reaction of 2a with Bn₂S₂

(Scheme 6, path c) proceeds via oxidation of the corresponding

cluster [{Pt(PPh₃)}₃(µ-SBn)₃]Cl (4f) by sulfur followed by the

well-known disproportionation of the disulfide (Scheme 7, 4

f 6/15).³²In accordance with this, clusters 4 were found to be

oxidized by sulfur and selenium yielding type 6/15 complexes

(Scheme 6, path d). Furthermore, ESI-MS measurements

showed that in the course of the reaction of 2a with Bn₂S₂the

triangular platinum cluster 4f and the sulfur capped trinuclear

complex 6 were formed after 24 h in molar ratio 1:1.

To investigate the reactivity of these clusters, the parent

cluster 4a was treated with chalcogens (Scheme 6, path d),

phosphine ligands (Scheme 6, path e, f), and halogens (Scheme

6, path g), resulting in oxidation, substitution, and degradation

processes, respectively. Reactions of 4a with monodentate

phosphines L′ that are stronger donors than the leaving ligand

L (L ) PPh₃) gave rise to partial and/or full ligand substitution

accompanied in all cases by a degradation yielding dinuclear

complexes 10 (Scheme 6, path e). In the case of the bidentate

phosphine ligand dppm, a degradation reaction took place

yielding the dinuclear complex 12 and [Pt(SMe)₂(dppm)] (13)

(Scheme 6, path f). In this reaction, the mean oxidation state of

Pt is preserved: 4 (1 × Pt^II+ 2 × Pt^I) f 12 (2 × Pt^I) + 13 (1

× Pt^II). The observation of Chatt and Chini that the addition of

phosphines L′ to the 42 cve clusters [{PtL}₃(µ-CO)₃] gives rise

to the formation of red-colored 44 cve clusters [Pt₃L₃L′(µ-

CO)₃]³³might indicate that the ligand substitution in our system

(Scheme 6, path e, f) proceeds also via an addition elimination

mechanism having 46 cve clusters [Pt₃L₃L′(µ-SMe)₃]Cl as

intermediates.

II

2

To understand the nature of bonding in complexes of type 4

and 6/15, quantum chemical calculations of the cations of the

parent complexes 4a and 15a (L ) PPh₃, R ) Me) were

performed. The existence of a bond path in the charge densitys

as found in 4a′ along the Pt-Pt vectorshas been stated to be

a necessary and sufficient requirement for the existence of a

bond.³⁵Thus, type 4 complexes have to be regarded as triangular

44 cve platinum clusters with Pt-Pt bonds whereas type 6/15

complexes are chalcogen-bridged trinuclear 48 ve complexes

without Pt-Pt bonding interactions. Complexes 6/15 can be

regarded as containing three square-planar platinum(II) moieties

sharing one common monodentately bound ligand (µ₃-S). The

sulfur atom in the trigonal-pyramidal Pt₃S unit is located 1.639-

(2) Å above the Pt₃plane. With the planar five coordinated

platinum centers in the non-oxidized clusters 4 in mind, the

“capping” (4 f 6/15) results not only in the reduction of the

coordination number (5 versus 4) but also in a severe change

of the complex geometry. Thus, this oxidation reaction may be

interpreted as a molecular switch of the complex geometry from

planar to trigonal-pyramidal, whereas the coordination geometry

of the platinum atoms remains planar in both cases.

(34) (a) Conza´lez-Duarte, P.; Lledo´s, A.; Mas-Balleste´, R. Eur. J. Inorg. Chem.

2004, 3585. (b) Mas-Balleste´, R.; Capdevila, M.; Champkin, P. A.; Glegg,

W.; Coxall, R. A.; Lledo´s, A.; Me´gret, C.; Conza´lez-Duarte, P. Inorg. Chem.

2002, 41, 3218. (c) Aullo´n, G.; Ujaque, G.; Lledo´s, A.; Alvarez, S. Chem.-

Eur. J. 1999, 5, 1391. (d) Aullo´n, G.; Ujaque, G.; Lledo´s, A.; Alvarez, S.;

Alemany, P. Inorg. Chem. 1998, 37, 804. (e) Capdevila, M.; Clegg, W.;

Conza´lez-Duarte, P.; Jarid, A.; Lledo´s, A. Inorg. Chem. 1996, 35, 490.

(35) (a) Bader, R. F. W. Atoms in Molecules: A Quantum Theory; Clarendon

Press: Oxford, U.K., 1990. (b) Bader, R. W. F. Acc. Chem. Res. 1985, 18,

9.

(32) De´marcq, M. C. J. Chem. Res. 1993, 3046.

(33) (a) Chatt, J.; Chini, P. J. Chem. Soc. A 1970, 1538. (b) Albinati, A.; Carturan,

G.; Musco, A. Inorg. Chim. Acta 1976, L2. (c) Browning, C. S.; Farrar, D.

H.; Gukathasan R. R.; Morris S. A. Organometallics 1985, 4, 1750.

9

J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007 4561

A R T I C L E S

Albrecht et al.

) 81 Hz). IR: ν 3049(w), 2953(w), 2913(w), 2849(w), 1634(m), 1478-

3. Experimental Section

(m), 1433(s), 1249(w), 1094(s), 747(m), 693(s), 532(s), 509(m) cm^-1

.

3.1. General Comments. All reactions and manipulations were

carried out under argon using standard Schlenk techniques. Solvents

were dried prior to use: CHCl₃, CH₂Cl₂over CaH₂, diethyl ether,

pentane over Na benzophenone, and acetone over molecular sieve A4.

The NMR spectra (¹H, ¹³C, ¹⁹F, ³¹P, ¹⁹⁵Pt) were recorded at 27 °C on

VARIAN Gemini 200, VXR 400, and Unity 500 spectrometers.

Chemical shifts are relative to solvent signals (CDCl₃, δ_H7.24, δ_C77.0;

CD₂Cl₂, δ_H5.32, δ_C53.8) as internal references; δ(³¹P), δ(¹⁹F), and

δ(¹⁹⁵Pt) are relative to external H₃PO₄(85% in D₂O), trifluorotoluene,

and H₂[PtCl₆] in D₂O, respectively. The coupling constants in higher

order spin systems were calculated using the program PERCH 2000.²⁰

Microanalyses (C, H, S, Cl) were performed by the University of Halle

microanalytical laboratory using for C, H, S a CHNS-932 (LECO) as

well as a VARIO EL (Elementaranalysensysteme) elemental analyzers

and for Cl by volumetric analysis (Scho¨ninger). GC-MS analyses were

carried out using a Hewlett-Packard (GC HP 5890 Series II, MS HP

5972) spectrometer equipped with mass selective detector (70 eV). IR

spectra were recorded on a Galaxy FT-IR spectrometer Mattson 5000

using KBr pellets. ESI spectra were recorded on a Finnigan Mat

spectrometer LCQ using the following conditions: carrier gas: N₂, flow

rate: 8 µL/min, spray voltage: 4.1 kV, temperature of the capillary:

150 °C, voltage of the capillary: 34 kV. The preparative centrifugal

thin layer chromatography was made by using a Chromatotron (Harrison

Research). Hexachloroplatinic acid (Degussa) and phosphines (Aldrich,

Fluka, Merck) were commercially available.

3.2. Reactivity of Platinum Acetyl Complexes toward Diorga-

nodisulfides. 3.2.1. Preparation of Triangular Platinum Clusters

[(PtL)₃(µ-SR)₃]Cl (4). To a solution of trans-[Pt(COMe)Cl(L)₂] (2)

(0.50 mmol) in chloroform (7 mL) was added dialkyldisulfide (5.00

mmol). The reaction mixture was heated under reflux. After 48 h, the

solvent and the excess of dialkyldisulfide were removed under vacuo.

The residue was purified by preparative centrifugal thin layer chro-

matography using at first n-pentane/diethyl ether (5/1), then chloroform/

diethyl ether (2/1), and finally chloroform/acetone (1/1) to elute the

disulfide, phoshine sulfide, S-alkylthioacetate, alkyl chloride, and the

complexes [(PtL)₃(µ-SR)₃]Cl (4), respectively. The latter complexes

were dissolved in chloroform (3 mL) and reprecipitated with n-pentane

(6 mL). After 2 days, the yellow, air-stable crystals were filtered off,

washed with n-pentane (10 mL), and dried in vacuo.

[{Pt(PPh₃)}₃(µ-SPr)₃]Cl (4c). Yield: 113 mg (36%). T_dec: 142 °C.

Found: C, 41.77; H, 3.96; S, 4.97. C₆₃H₆₆S₃P₃ClPt₃‚2CHCl₃(1871.76)

requires C, 41.71; H, 3.66; S, 5.14. H NMR (500 MHz, CDCl₃): δ

1

0.22 (s(br), 9H, CH₃), 0.77 (s(br), 6H, â-CH₂), 1.13 (s(br), 6H, R-CH₂),

7.43 (m, 45H, Ph). ¹³C NMR (125 MHz, CDCl₃): δ 13.0 (s, CH₃),

29.2 (s(br), â-CH₂), 37.2 (s(br), R-CH₂), 128.6 (s(br), m-CH), 131.3

(s(br), p-CH), 131.6 (m, i-C), 133.8 (s(br), o-CH). ³¹P NMR (81 MHz,

1

2

CDCl₃): δ 1.5 (m, J(Pt,P) ) 4240 Hz, J(Pt,Pt) ) 1950 Hz, J(Pt,P)

) 95 Hz, ³J(P,P) ) 80 Hz). ESI-MS: m/z (obsd/calcd for [{Pt(PPh₃)}₃-

(µ-SPr)₃]⁺, %) 1592 (2/2), 1593 (10/11), 1594 (39/35), 1595 (73/71),

1596 (95/96), 1597 (100/100), 1598 (81/85), 1599 (62/64), 1600 (41/

42), 1601 (24/25), 1602 (11/13), 1603 (5/6), 1604 (2/3). IR: ν 3048-

(w), 2957(w), 2915(w), 2867(w), 1478(m), 1433(s), 1227(w), 1094(s),

745(m), 692(s), 532(s), 510(m) cm^-1

.

[{Pt(PPh₃)}₃(µ-SBu)₃]Cl (4d). Yield: 120 mg (42%). T_dec: 140 °C.

Found: C, 45.61; H, 4.43; S, 5.73. C₆₆H₇₂S₃P₃ClPt₃‚0.5 CHCl₃

1

(1717.05) requires C, 46.52; H, 4.26; S, 5.60. H NMR (500 MHz,

CDCl₃): δ 0.51 (s(br), 9H, CH₃), 0.59 (s(br), 6H, γ-CH₂), 0.88 (s(br),

6H, â-CH₂), 1.13 (s(br), 6H, R-CH₂), 7.44 (m, 45H, Ph). ¹³C NMR

(125 MHz, CDCl₃): δ 13.8 (s, CH₃), 21.9 (s, γ-CH₂), 29.6 (s, â-CH₂),

35.2 (s(br), R-CH₂), 128.5 (s(br), m-CH), 131.3 (s(br), p-CH, 131.4

(s(br), i-C), 133.7 (s(br), o-CH). ³¹P NMR (81 MHz, CDCl₃): δ 1.4

(m,¹J(Pt,P) ) 4235 Hz, ¹J(Pt,Pt) ) 1930 Hz, ²J(Pt,P) ) 97 Hz, ³J(P,P)

) 80 Hz). ESI-MS: m/z (obsd/calcd for [{Pt(PPh₃)}₃(µ-SBu)₃]⁺, %)

1634 (2/2), 1635 (9/11), 1636 (39/34), 1637 (75/70), 1638 (98/95), 1639

(100/100), 1640 (88/85), 1641 (66/65), 1642 (43/43), 1643 (24/25),

1644 (11/13), 1645 (5/7), 1646 (2/3). IR: ν 3050(w), 2953(w), 2920-

(w), 2868(w), 1479(m), 1434(s), 1214(w), 1094(s), 745(m), 692(s), 532-

(s), 509(m) cm^-1

.

[{Pt{P(4-FC₆H₄)₃}}₃(µ-SMe)₃]Cl (4e). Yield: 120 mg (42%).

T

_dec: 183 °C. Found: C, 39.64; H, 2.19. C₅₇H₄₅S₃P₃F₉ClPt₃(1710.76)

1

requires C, 40.02; H, 2.65. H NMR (200 MHz, CDCl₃): δ 1.08 (m,

³J(Pt,H) ) 42.7 Hz, 9H, CH₃), 7.15 (m, 18H, Ph), 7.46 (m, 18H, Ph).

¹³C NMR (125 MHz, CDCl₃): δ 18.4 (s(br), CH₃), 115.5 (d′t′, ²J(C,F)

) 20.2 Hz, N ) 10.2 Hz, m-CH), 125.6 (′t′, N ) 55.2 Hz, i-C), 137.0

(d′t′, ³J(C,F) ) 7.4 Hz, N ) 16.6 Hz, o-CH), 165.5 (d, ¹J(C,F) ) 254.1

Hz, CF). ³¹P NMR (81 MHz, CDCl₃): δ -0.4 (m, J(Pt,P) ) 4280

1

Hz, J(Pt,Pt) ) 2250 Hz, J(Pt,P) ) 100 Hz, J(P,P) ) 80 Hz). ¹⁹F

NMR (188 MHz, CDCl₃): δ -106.9 (s(br)). IR: ν 3009(w), 2978(w),

2359(m), 2338(m), 1588(s), 1495(s), 1393(m), 1235(s), 1161(s), 1094-

1

2

3

[{Pt(PPh₃)}₃(µ-SMe)₃]Cl (4a). Yield: 150 mg (56%). Fp.: 123 °C,

T_dec: 152 °C. Found: C, 42.30; H, 3.68; S, 6.19; Cl, 5.50. C₅₇H₅₄S₃P₃-

(m), 827(m), 533(s) cm^-1

.

ClPt₃‚0.5CHCl₃(1608.53) requires C, 42.93; H, 3.41; S, 5.98; Cl, 5.51.

¹H NMR (200 MHz, CDCl₃): δ 0.86 (m,³J(Pt,H) ) 43.6 Hz, 9H, CH₃),

7.41 (s(br), 45H, o-, m-, p-CH). ¹³C NMR (125 MHz, CDCl₃): δ 17.5

(s(br), CH₃), 128.6 (m, m-CH), 131.0 (m, i-C), 131.3 (s, p-CH), 133.9

(m, o-CH). ³¹P NMR (202 MHz, CDCl₃): δ 2.8 (m,¹J(Pt,P) ) 4220

Hz,¹J(Pt,Pt) ) 2100 Hz,²J(Pt,P) ) 96 Hz,³J(P,P) ) 80 Hz). ¹⁹⁵Pt NMR

(107 MHz, CDCl₃): δ -5767 (m). ESI-MS: m/z (obsd/calcd for [{Pt-

(PPh₃)}₃(µ-SMe)₃]⁺, %) 1508 (1/1), 1509 (16/11), 1510 (38/36), 1511

(85/73), 1512 (98/97), 1513 (100/100), 1514 (85/83), 1515 (59/62),

1516 (39/40), 1517 (20/23), 1518 (10/11), 1519 (4/5) 1520 (2/2). IR:

ν 3074(w), 3052(w), 2914(w), 1624(m), 1480(m), 1434(s), 1300(w),

1096(s), 746(m), 694(s), 534(s), 510(m) cm^-1. GC-MS of the reaction

mixture: m/z (MeCl, %) 50 (100) (M⁺), 47 (10), 40 (3), 37 (1), 35 (3).

m/z (S-methylthioacetate, %) 90 (45) (M⁺), 75 (5), 43 (100), 28 (13).

m/z (Me₂S₂, %) 94 (100) (M⁺), 79 (60), 64 (15), 61 (17), 45 (40), 33

(6), 28 (9).

3.2.2. Preparation of Dinuclear Platinum Complexes [{PtCl(L)}₂-

(µ-SPh)₂] (5). To a solution of (2) (0.50 mmol) in chloroform (7 mL)

was added diphenyldisulfide (5.00 mmol). The reaction mixture was

heated under reflux for 48 h. The solvent was then removed under

vacuo. The residue was washed with n-pentane (5 × 10 mL) and

purified by preparative centrifugal thin layer chromatography using at

first n-pentane and finally diethyl ether/n-pentane (2/1) to elute Ph₂S₂,

the phosphine ligand, and 5, respectively. The last fraction was

recrystallized from methylene chloride/n-pentane (1/10 mL) (5a) or

chloroform/diethyl ether (1/10 mL) (5b, 5c). After 2 days, the yellow,

air-stable crystals were filtered off, washed with n-pentane (10 mL),

and dried in vacuo.

[{PtCl(PPh₃)}₂(µ-SPh)₂] (5a). Yield: 47 mg (16%). T_dec: 196 °C.

Found: C, 47.32; H, 3.35; S, 4.79; Cl, 5.13. C₄₈H₄₀S₂P₂Cl₂Pt₂(1203.99)

requires C, 47.88; H, 3.69; S, 4.79; Cl, 5.89. ¹H NMR (200 MHz,

CDCl₃): δ 7.30 (m, Ph). ³¹P NMR (81 MHz, CDCl₃): δ 19.3 (s+m,

¹J(Pt,P) ) 3395 Hz, ²J(Pt,Pt) ) 920 Hz, ³J(Pt,P) ) -24 Hz, ⁴J(P,P) )

12 Hz). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ -4021 (m). IR: ν 3054(m),

1638(m), 1576(s), 1472(m), 1436(s), 1098(s), 1024(m), 738(m), 692-

[{Pt(PPh₃)}₃(µ-SEt)₃]Cl (4b). Yield: 135 mg (49%). T_dec: 143 °C.

Found: C, 43.97; H, 4.00; S, 5.53. C₆₀H₆₀S₃P₃ClPt₃‚0.5CHCl₃(1650.63)

1

requires C, 44.03; H, 3.69; S, 5.83. H NMR (200 MHz, CDCl₃): δ

0.42 (m(br),³J(H,H) ) 7.15 Hz, 9H, CH₃), 1.19 (m, 6H, CH₂), 7.43

(m, 45H, Ph). ¹³C NMR (125 MHz, CDCl₃): δ 21.1 (s+d,³J(Pt,C) )

44.5 Hz, CH₃), 30.6 (s(br), CH₂), 128.8 (m, m-CH), 131.3 (s, p-CH),

131.5 (m, i-C), 134.0 (m, o-CH). ³¹P NMR (202 MHz, CDCl₃): δ 1.4

(m,¹J(Pt,P) ) 4220 Hz,¹J(Pt,Pt) ) 1950 Hz,²J(Pt,P) ) 96 Hz,³J(P,P)

(s), 536(s), 514(m) cm^-1

.

[{PtCl{P(4-FC₆H₄)₃}}₂(µ-SPh)₂] (5b). Yield: 148 mg (45%).

1

T

_dec: 284-288 °C. H NMR (200 MHz, CDCl₃): δ 6.93 (m, 18H,

Ph), 7.40 (m, 12H, Ph), 7.64 (m, 4H, Ph). ¹³C NMR (50 MHz,

9

4562 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters

A R T I C L E S

CDCl₃): δ 115.5 (m, m-CH), 123.5 (m, SPh), 126.5 (s, SPh), 127.3

(m, i-C), 132.5 (s, SPh), 133.6 (m, SPh), 136.6 (m, o-CH), 164.2

(d,¹J(C,F) ) 254.1 Hz, CF). ¹⁹F NMR (188 MHz, CDCl₃): δ -108.1

(m), 2339(m), 1481(m), 1435(s), 1079(m), 1024(w), 998(w), 956(w),

738(s), 692(s) cm^-1

.

3.2.5. Reactivity of [Pt(COMe)Cl(AsPh₃)(PPh₃)] toward Me₂S₂.

To a solution of trans-[Pt(COMe)Cl(AsPh₃)(PPh₃)] (2g) (200 mg, 0.24

mmol) in chloroform (7 mL) was added dimethyldisulfide (236 mg,

2.50 mmol). The reaction mixture was heated under reflux for 48 h.

The solvent was then removed under vacuo. The residue was purified

by preparative centrifugal thin layer chromatography using at first

n-pentane, then chloroform/acetone (1/1), and finally chloroform/

acetone/methanol (1/1/1) to elute the disulfide, phoshine sulfide,

S-alkylthioacetate, alkyl chloride, and the complexes [(PtL)₃(µ-SMe)₃]-

Cl (4a, 8), respectively. The trinuclear clusters 4a, 8 were reprecipitated

from chloroform/n-pentane solutions (2/15 mL). After 1 h, the yellow,

air-stable powder was filtered off, washed with n-pentane (10 mL),

1

(s). ³¹P NMR (81 MHz, CDCl₃): δ 15.8 (s+m, J(Pt,P) ) 3303 Hz,

3

4

²J(Pt,Pt) ) 1230 Hz, J(Pt,P) ) -39 Hz, J(P,P) ) 14 Hz). IR: ν

3060(w), 2962(w), 1585(s), 1495(s), 1469(m), 1394(m), 1232(s), 1161-

(s), 1095(s), 1016(m), 825(s), 744(m), 688(w), 528(s) cm^-1

.

[{PtCl(AsPh₃)}₂(µ-SPh)₂] (5c). Yield: 47 mg (21%). T_dec: 252 °C.

Found: C, 46.86; H, 3.72 C₄₈H₄₀S₂As₂Cl₂Pt₂‚Et₂O (1365.99) requires

1

C, 46.26; H, 3.73. H NMR (400 MHz, CDCl₃): δ 7.16 (m, 8H, Ph),

7.30 (m, 12H, Ph), 7.41 (m, 14H, Ph), 7.70 (m, 6H, Ph). ¹³C NMR

(100 MHz, CDCl₃): δ 128.5 (s, m-CH, SPh), 128.6 (s, m-CH, AsPh₃),

130.2 (s, i-C, AsPh₃), 130.3 (s, p-CH, AsPh₃), 130.5 (s, p-CH, SPh),

131.0 (s, i-C, SPh), 133.7 (s, o-CH, AsPh₃), 134.4 (s, o-CH, SPh). IR:

ν 3051(w), 2919(w), 2850(w), 1481(m), 1436(s), 1079(m), 1023(w),

1

and dried in vacuo. Yield: 74 mg. H NMR (200 MHz, CDCl₃): δ

0.86 (m, 3.9 H (43%), CH₃(4a, 8)), δ 1.05 (m, 3.5H (39%), CH₃(8)),

7.43 (s(br), 45H, Ph). ³¹P NMR (81 MHz, CDCl₃): δ 3.0 (m, 4a), 3.6

(m, 8a), 4.5 (m, 8b). ESI-MS: m/z (obsd/calcd for [Pt₃(PPh₃)₂(AsPh₃)-

(µ-SMe)₃]⁺(cation of 8a), %) 1552 (2/2), 1553 (11/12), 1554 (41/37),

1555 (75/73), 1556 (98/97), 1557 (100/100), 1558 (82/83), 1559 (61/

62), 1560 (39/40), 1561 (22/24), 1562 (10/12), 1563 (5/6), 1564 (1/2);

(obsd/calcd for [Pt₃(PPh₃)(AsPh₃)₂(µ-SMe)₃]⁺(cation of 8b), %) 1597

(11/12), 1598 (35/37), 1599 (74/73), 1600 (90/97), 1601 (100/100),

1602 (79/83), 1603 (58/62), 1604 (36/40), 1605 (19/24), 1606 (7/6),

1607 (2/2); (obsd/calcd for [{Pt(AsPh₃)}₃(µ-SMe)₃]⁺(cation of 8c),

%) 1639 (1/1), 1640 (2/2), 1641 (9/11), 1642 (35/37), 1643 (78/73),

1644 (100/97), 1645 (97/100), 1646 (83/83), 1647 (55/62), 1648 (41/

42), 1649 (10/12), 1650 (6/6). Ratio calculated from ESI-MS

spectrum: 4a, 43%; 8a, 39%; 8b, 15%; 8c, 3%.

999(w), 738(s), 691(s) cm^-1

.

3.2.3. Preparation of Trinuclear Complex [{Pt(PPh₃)}₃(µ₃-S)(µ-

SBn)₃]Cl (6). To a solution of trans-[Pt(COMe)Cl(PPh₃)₂] (2a) (400

mg, 0.50 mmol) in chloroform (7 mL) was added dibenzyldisulfide

(1.23 g, 5.00 mmol). The reaction mixture was heated under reflux.

After 48 h, the solvent and the excess of dibenzyldisulfide were removed

under vacuo. The residue was purified by preparative centrifugal thin

layer chromatography using at first n-pentane/diethyl ether (5/1), then

chloroform/diethyl ether (2/1), and finally chloroform/acetone/methanol

(3/3/1) to elute Bn₂S₂, PPh₃S, and 6, respectively. The latter complex

was recrystallized from acetone/n-pentane solutions (3/6 mL). After 2

days, the light-yellow, air-stable crystals were filtered off, washed with

n-pentane (10 mL), and dried in vacuo. Yield: 48 mg (16%). T_dec: 83

°C. Found: C, 48.52; H, 3.80. C₇₅H₆₆S₄P₃ClPt₃(1809.20) requires C,

49.80; H, 3.68. ¹H NMR (500 MHz, CDCl₃): δ 1.24 (s(br), 6H, CH₂),

7.16 (m, 60H, Ph). ³¹P NMR (81 MHz, CDCl₃): δ 8.3 (s+m, ¹J(Pt,P)

) 3800 Hz, ²J(Pt,Pt) ) 458 Hz, ³J(Pt,P) ) -40 Hz, ⁴J(P,P) ) 6 Hz).

¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ -3893 (m). ESI-MS: m/z (obsd/

calcd for [{Pt(PPh₃)}₃(µ₃-S)(µ-SBn)₃]⁺, %) 1768 (2/2), 1769 (12/10),

1770 (35/31), 1771 (70/65), 1772 (92/92), 1773 (100/100), 1774 (88/

88), 1775 (68/70), 1776 (46/48), 1777 (28/30), 1778 (15/16), 1779 (10/

8), 1780 (4/4). IR: ν 3052(w), 2924(w), 1479(m), 1434(s), 1096(s),

747(m), 694(s), 533(s), 512(m) cm^-1. ESI-MS of the reaction mixture

after 24 h reaction time: m/z (obsd/calcd for [{Pt(PPh₃)}₃(µ-SBn)₃]⁺,

%) 1736 (2/2), 1737 (8/10), 1738 (32/32), 1739 (68/67), 1740 (92/93),

1741 (100/100), 1742 (86/87), 1743 (65/67), 1744 (47/45), 1745 (26/

27), 1746 (13/14), 1747 (7/7), 1748 (3/3); (obsd/calcd for [{Pt(PPh₃)}₃-

(µ₃-S)(µ-SBn)₃]⁺, %) 1768 (2/2), 1769 (12/10), 1770 (35/31), 1771 (70/

65), 1772 (92/92), 1773 (100/100), 1774 (88/88), 1775 (68/70), 1776

(46/48), 1777 (28/30), 1778 (15/16), 1779 (10/8), 1780 (4/4). Relative

ratio after 24 h reaction time calculated from ESI-MS spectrum: [{Pt-

(PPh₃)}₃(µ-SBn)₃]Cl : [{Pt(PPh₃)}₃(µ₃-S)(µ-SBn)₃]Cl, 1:1.

3.3. Reactivity of Triangular Platinum Clusters [{Pt(PPh₃)}₃(µ-

SR)₃]Cl (4). 3.3.1. Reactivity toward Monodendate Phosphine

Ligands. Reaction of 4a with PMePh₂. To a solution of 4a (100 mg,

0.065 mmol) in deuterated chloroform (0.7 mL) was added PMePh₂

(39 mg, 0.195 mmol) at -70 °C. Directly after the addition of the

phosphine, a dark-red solution was formed. After warming up to room

temperature, the color of the reaction mixture changed to yellow. This

solution was investigated by NMR spectroscopy. ¹H NMR (200 MHz,

3

CDCl₃): δ 1.33 (m, J(Pt,H) ) 44.8 Hz, CH₃S (9a)), 1.74 (s(br)+d,

³J(Pt,H) ) 36.5 Hz, SCH₃(10a), 2.04 (m(br), CH₃P (10a)), 2.65 (m(br),

CH₃P (9a)), 7.33 (m(br), Ph), 7.52 (m(br), Ph). ³¹P NMR (81 MHz,

CDCl₃): δ -16.4 (m,¹J(Pt,P) ) 4096 Hz,¹J(Pt,Pt) ) 1900 Hz, ²J(Pt,P)

3

1

) 85 Hz, J(P,P) ) 75 Hz, 9a), -4.3 (s, PPh₃), 4.5 (s+m, J(Pt,P) )

3

4

3012 Hz, J(Pt,P) ) -11 Hz, J(P,P) ) 15 Hz, 10a). ESI-MS: m/z

(obsd/calcd for [{Pt(PMePh₂)}₃(µ-SMe)₃]⁺(cation of 9a), %) 1323 (7/

14), 1324 (37/40), 1325 (75/78), 1326 (92/100), 1327 (100/99), 1328

(80/80), 1329 (84/59), 1330 (83/36), 1331 (37/21), 1332 (26/10), 1333

(6/5).

Reaction of 4a with PMePh₂in a Stoichiometric Ratio of 1:1

(Using 0.065 mmol of 4a and PMePh₂). ¹H NMR (200 MHz,

CDCl₃): δ 0.86 (m(br), CH₃(4a, 11)), 1.33 (m(br), CH₃S (9a, 11)),

2.65 (m(br), CH₃P (9a,11)), 7.33 (m(br), Ph), 7.30 (s(br), Ph), 7.52

(m(br), Ph). ³¹P NMR (81 MHz, CDCl₃): δ -16.8 (m(br), 9a, 11),

-4.3 (s, PPh₃), 3.0 (m(br), 4a, 11), 4.5 (s, 10a). ESI-MS: m/z (obsd/

calcd for [Pt₃(PPh₃)₂(PMePh₂)(µ-SMe)₃]⁺(cation of 11a), %) 1446 (1/

2), 1447 (10/12), 1448 (34/38), 1449 (68/75), 1450 (90/98), 1451 (100/

100), 1452 (80/82), 1453 (57/61), 1454 (37/39), 1455 (21/23), 1456

(12/11), 1457 (6/6), 1458 (2/2); (obsd/calcd for [Pt₃(PPh₃)(PMePh₂)₂-

(µ-SMe)₃]⁺(cation of 11b), %) 1384 (1/2), 1385 (6/13), 1386 (29/39),

1387 (71/77), 1388 (99/99), 1389 (100/100), 1390 (84/81), 1391 (63/

60), 1392 (41/38), 1393 (27/22), 1394 (13/11), 1395 (7/5), 1396 (3/2).

Reaction of 4a with PMe₂Ph. To a solution of 4a (100 mg, 0.065

mmol) in deuterated chloroform (0.7 mL) was added PMe₂Ph (27 mg,

0.20 mmol) at -70 °C. Directly after the addition of the phosphine, a

dark-red solution was formed, which changed color within 10 min to

yellow. After warming up to room temperature, the solution was

3.2.4. Preparation of Dinuclear Platinum Complex [{PtCl-

(AsPh₃)}₂(µ-SMe)₂] (7). To a solution of trans-[Pt(COMe)Cl(AsPh₃)₂]

(2c) (220 mg, 0.25 mmol) in chloroform (7 mL) was added dimeth-

yldisulfide (236 mg, 2.50 mmol). The reaction mixture was heated under

reflux for 48 h. The solvent was then removed under vacuo. The residue

was purified by preparative centrifugal thin layer chromatography using

at first n-pentane, then chloroform/acetone (1/1), and finally chloroform/

acetone/methanol (1/1/1) to elute Ph₂S₂, AsPh₃, and 7, respectively.

From the last fraction, the solvent was removed in vacuo. The light-

yellow powder was recrystallized from chloroform/n-pentane (10/10

mL) solutions. After 2 days, the light-yellow, air-stable crystals were

filtered off, washed with n-pentane (10 mL), and dried in vacuo.

Yield: 65 mg (44%). T_dec: 102 °C. Found: C, 39.07; H, 3.39; S, 5.39.

1

C₃₈H₃₆S₂As₂Cl₂Pt₂(1167.73) requires C, 39.09; H, 3.11; S, 5.49. H

NMR (400 MHz, CDCl₃): δ 2.51 (s+d, ³J(Pt,H) ) 39.0 Hz, 6H, CH₃),

7.29 (m, 12H, Ph), 7.39 (m, 6H, Ph), 7.52 (m, 12H, Ph). ¹³C NMR

(100 MHz, CDCl₃): δ 19.0 (s(br), CH₃), 128.7 (s, m-CH), 130.4 (s,

p-CH), 131.0 (s, i-C), 133.7 (s, o-CH). IR: ν 3051(w), 2916(w), 2360-

1

investigated by NMR spectroscopy. H NMR (200 MHz, CDCl₃): δ

9

J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007 4563

A R T I C L E S

Albrecht et al.

3

1.77 (′t′+d′t′, N ) 5.0 Hz, J(Pt,H) ) 31.5 Hz, CH₃P; diastereotopic

protons have not been found to split up to -50 °C), 2.41 (quin+dquin,

(SMe)₂(dppm)] (13), respectively. From the last two fractions the

solvent was removed. The yellow platinum(I) complexes 12a/12b and

the white platinum(II) complex 13 were crystallized from chloroform/

n-pentane (2/7 mL) solutions. After 2 days, the air-stable crystals were

filtered off, washed with n-pentane (10 mL), and dried in vacuo. The

dinuclear platinum(I) complex 12c was obtained after chromatographic

purification as a yellow oil.

³J(Pt,H) ) 37.4 Hz, J(P,H) ) 2.5 Hz, CH₃S), 7.40 (m(br), Ph). ³¹P

4

NMR (81 MHz, CDCl₃): δ -28.9 (m, ¹J(Pt,P) ) 3956 Hz, 9b), -9.7

(s+m, ¹J(Pt,P) ) 2996 Hz, ³J(Pt,P) ) -7 Hz, ⁴J(P,P) ) 14 Hz, 10b),

-4.3 (s, PPh₃). From this solution, the solvent was removed under

vacuo, and the residue was purified by reprecipitation from methylene

chloride/n-pentane solutions (2/7 mL). After 5 h, the light-yellow, air-

stable powder of [{Pt(PMe₂Ph)₂}₂(µ-SMe)₂]Cl₂(10b) was filtered off,

washed with n-pentane (10 mL), and dried in vacuo. Yield: 65 mg

[{Pt(PPh₃)}₂(µ-SMe)(µ-dppm)]Cl (12a). Yield: 90 mg (73%).

T

_dec: 161 °C. Found: C, 51.18; H, 4.09. C₆₂H₅₅P₄SClPt₂‚0.5CH₂Cl₂

(1422.17) requires C, 52.74; H, 3.97. ¹H NMR (200 MHz, CDCl₃): δ

1.31 (′t′+d′t′, ³J(Pt,H) ) 41.5 Hz, N ) 10.79 Hz, 3H, CH₃), 2.30 (s(br),

2H, CH₂), 7.13 (m(br), 50H, Ph). ¹³C NMR (50 MHz, CDCl₃): δ 22.1

1

(60%). H NMR (200 MHz, CDCl₃): δ 1.77 (′t′+d′t′, N ) 4.98 Hz,

³J(Pt,H) ) 31.5 Hz, 24H, CH₃P), 2.41 (quin+dquin, J(Pt,H) ) 37.4

3

Hz, J(P,H) ) 2.5 Hz, 6H, CH₃S), 7.40 (m(br), 30H, Ph). ³¹P NMR

4

2

(′t′+d′t′, N ) 3.9 Hz, J(Pt,C) ) 19.8 Hz, SCH₃), 62.3 (s(br), CH₂),

1

3

(81 MHz, CDCl₃): -9.74 (s+m, J(Pt,P) ) 2996 Hz, J(Pt,P) ) -7

128.6 (m(br), 130.6 (s(br), 130.9 (s(br), 133.2 (m(br), 133.6 (m(br).

³¹P NMR (81 MHz, CDCl₃): δ -3.9 (m,¹J(Pt,Pt) ) 2770 Hz,¹J(Pt,P)

) 3880 Hz,²J(Pt,P) ) -90 Hz, ²J(P,P) ) 40 Hz, ²J(P,PPh₃) ) 10 Hz,

³J(P,PPh₃) ) -20 Hz, P(dppm)), 21.9 (m, ¹J(Pt,P) ) 3010 Hz, ²J(Pt,P)

4

Hz, J(P,P) ) 14 Hz).

Reaction of 4a with PBu₃. To a solution of 4a (100 mg, 0.065

mmol) in deuterated chloroform (0.7 mL) was added PBu₃(39 mg,

0.20 mmol) at -70 °C. Directly after the addition of the phosphine, a

dark-red solution was formed. After warming up to room temperature,

the color of the reaction mixture changed to light yellow. This solution

was investigated by NMR spectroscopy. ¹H NMR (200 MHz, CDCl₃):

δ 0.79-0.89 (m, CH₃, 9c, 10c), 1.26-1.48 (m, CH₂, 9c, 10c), 1.69

(s(br), CH₂, 9c), 1.86-2.07 (m, CH₂, CH₃, 9c, 10c), 2.36 (s+m, ³J(Pt,H)

) 47.3 Hz, SCH₃(9c)), 7.30 (s(br), Ph). ³¹P NMR (81 MHz, CDCl₃):

3

) 170 Hz, J(P,P) ) 160 Hz, PPh₃). ¹⁹⁵Pt NMR (107 MHz, CDCl₃):

-5020 (m). IR: ν 3048(w), 2978(w), 1630(s), 1584(s),1478(m), 1433-

(s), 1306(w), 1261(w), 1183(w), 1095(s), 997(w), 740(w), 691(s), 525-

(s), 507(s), 486(s) cm^-1

.

[{Pt{P(4-FC₆H₄)₃}}₂(µ-SMe)(µ-dppm)]Cl (12b). Yield: 84 mg

1

(65%). T_dec: 182 °C. H NMR (200 MHz, CDCl₃): δ 1.63 (′t′+d′t′,

³J(Pt,H) ) 41.5 Hz, N ) 11.62 Hz, 3H, CH₃), 2.28 (s(br), 2H, CH₂),

1

2

6.93 (m(br), 18H, Ph), 7.20 (m(br), 26H, Ph). ¹³C NMR (100 MHz,

δ -7.2 (m, J(Pt,P) ) 3930 Hz, J(Pt,Pt) ) 1855 Hz, J(Pt,P) ) 65

Hz, J(P,P) ) 71 Hz, 9c), -4.3 (s, PPh₃), 7.5 (s+m, J(Pt,P) ) 2565

Hz, J(Pt,P) ) -17 Hz, J(P,P) ) 30 Hz, 10c).

3

1

2

CDCl₃): δ 22.9 (′t′+d′t′, N ) 3.9 Hz, J(Pt,C) ) 19.2 Hz, SCH₃),

3

4

60.0 (s(br), CH₂), 115.9 (m, m-CH), 128.2 (′t′, N ) 10.3 Hz), 128.4

(m), 130.4 (s(br), 133.1 (m), 135.7 (m), 164.1 (d, ¹J(C,F) ) 253.4 Hz,

CF). ¹⁹F NMR (188 MHz, CDCl₃): δ -109.18 (s(br), CF). ³¹P NMR

From this solution, the solvent was removed under vacuo, and the

crude product was purified by preparative centrifugal thin layer

chromatography using at first n-pentane/diethyl ether (5/1), then

chloroform/diethyl ether (2/1), and finally chloroform/acetone/methanol

(3/3/1). From the last fraction, the solvent was removed under vacuo.

The yellow oil was investigated by NMR spectroscopy. Yield: 43 mg

(48%). H NMR (200 MHz, CDCl₃): δ 0.87 (t, J(H,H) ) 7.47 Hz,

27H, CH₃), 1.39 (s(br), 36H, CH₂), 1.69 (s(br), 18H, CH₂), 2.36 (s+m,

³J(Pt,H) ) 47.3 Hz, 9H, SCH₃). ¹³C NMR (50 MHz, CDCl₃) δ 13.7

(s, CH₃), 21.1 (s(br), SCH₃), 24.2 (′t′, N ) 13.7 Hz, γ-CH₂), 26.7 (m,

â-CH₂), 27.7 (m(br), R-CH₂). ³¹P NMR (81 MHz, CDCl₃): δ -7.2

(m, ¹J(Pt,P) ) 3930 Hz, ¹J(Pt,Pt) ) 1855 Hz, ²J(Pt,P) ) 65 Hz, ³J(P,P)

) 71 Hz).

Reaction of 4b with PBu₃. To a solution of 4b (200 mg, 0.123

mmol) in methylene chloride (5 mL) was added PBu₃(75 mg, 0.37

mmol) at -70 °C. Directly after the addition of the phosphine, a dark-

red solution was formed. After warming up to room temperature,

preparative centrifugal thin layer chromatography using at first n-

pentane/ether (5/1), then chloroform/ether (2/1), and finally chloroform/

acetone/methanol (3/3/1) was performed. From the last fraction, the

solvent was removed under vacuo, and the yellow oil was investigated

1

(81 MHz, CDCl₃): δ -3.7 (m, J(Pt,Pt) ) 2850 Hz, J(Pt,P) ) 3875

Hz, ²J(Pt,P) ) -85 Hz, ²J(P,P) ) 30 Hz, ²J(P,P(4-FC₆H₄)₃) ) 13 Hz,

³J(P, P(4-FC₆H₄)₃) ) -16 Hz, P(dppm)), 19.9 (m, J(Pt,P) ) 3055

1

Hz, ²J(Pt,P) ) 188 Hz, J(P,P) ) 170 Hz, P(4-FC₆H₄)₃). IR: ν 3048-

3

1

3

(w), 3013(w), 2914(w), 2851(w), 1622(w), 1585(s), 1493(s), 1434(m),

1392(w), 1302(w), 1224(m), 1159(s), 1095(s), 948(w), 829(m), 814-

(m), 738(m), 692(m), 526(s) cm^-1

.

[{Pt(PBu₃)}₂(µ-SMe)(µ-dppm)]Cl (12c). Yield: 77 mg (71%). ¹H

3

NMR (400 MHz, CDCl₃): δ 0.76 (t, J(H,H) ) 7.06 Hz, 18H, CH₃),

1.73 (m, 24H, â-, γ-CH₂), 1.38 (m, 12H, R-CH₂), 2.27 (s(br), 2H, CH₂),

3

2.66 (′t′+d′t′, J(Pt,H) ) 43.6 Hz, N ) 11.21 Hz, 3H, SCH₃), 7.26

(m(br), 20H, Ph). ¹³C NMR (100 MHz, CDCl₃): δ 13.7 (s, CH₃), 23.9

(′t′+d′t′, N ) 3.7 Hz,²J(Pt,C) ) 20.6 Hz, SCH₃), 24.2 (′t′, N ) 13.3

Hz, γ-CH₂), 26.4 (′t′, N ) 16.9 Hz, â-CH₂), 27.1 (′quin′, N ) 51.6 Hz,

R-CH₂), 63.9 (s(br), CH₂), 128.3 (m(br), 128.6 (′t′, N ) 11.8 Hz), 131.2

1

(s(br), 133.0 (m(br). ³¹P NMR (81 MHz, CDCl₃): δ -5.7 (m, J(Pt,-

Pt) ) 2380 Hz, ¹J(Pt,P) ) 3925 Hz, ²J(Pt,P) ) -86 Hz, ²J(P,P) ) 25

2

3

Hz, J(P,PBu₃) ) 10 Hz, J(P,PBu₃) ) -21 Hz, P(dppm)), 7.3 (m,

¹J(Pt,P) ) 2948 Hz, J(Pt,P) ) 70 Hz, J(P,P) ) 150 Hz, PBu₃).

[Pt(SMe)₂(dppm)] (13). Yield: 22 mg (75%). T_dec: 142 °C. ¹H NMR

(200 MHz, CDCl₃): δ 2.19 (t+dt, J(Pt,H) ) 49.0 Hz, J(P,H) ) 5.0

Hz, 6H, CH₃), 4.28 (t+dt, ²J(P,H) ) 10.4 Hz, ³J(Pt,H) ) 44.2 Hz, 2H,

CH₂), 7.42 (m, 12H, Ph), 7.83 (m, 8H, Ph). ¹³C NMR (100 MHz,

2

3

1

by NMR spectroscopy. Yield: 110 mg (62%). H NMR (200 MHz,

3

4

CD₂Cl₂): δ 0.72 (m, 36H, CH₃(SEt), CH₃(Bu)), 1.05 (m, 9H, SCH₂),

1.28(m, 36H, â-, γ-CH₂), 2.08 (m, 18H, R-CH₂). ¹³C NMR (50 MHz,

CD₂Cl₂): δ 13.6 (s, CH₃), 21.8 (s+d, ³J(Pt,C) ) 49.1 Hz, CH₃(SEt)),

24.3 (m, γ-CH₂), 26.6 (m, â-CH₂), 29.0 (m, R-CH₂), 33.1 (s(br), CH₂

(SEt)). ³¹P NMR (81 MHz, CD₂Cl₂): δ -8.1 (m, ¹J(Pt,P) ) 3942 Hz,

2

3

CDCl₃): δ 12.2 (t+dt, J(Pt,C) ) 22.0 Hz, J(P,C) ) 2.3 Hz, CH₃),

2

1

48.7 (t+dt, J(Pt,C) ) 36.7 Hz, J(P,C) ) 30.2 Hz, CH₂), 128.1 (′d′,

N ) 25.0 Hz), 128.5 (′d′, N ) 6.9 Hz), 128.7 (s(br)), 129.0 (′t′, N )

5.6 Hz), 131.6 (s(br), 132.8 (′d′, N ) 20.3 Hz), 133.3 (′t′, N ) 6.1

Hz), 133.7 (′d′, N ) 19.5 Hz). ³¹P NMR (81 MHz, CDCl₃): δ -47.0

(s+d,¹J(Pt,P) ) 2362 Hz). IR: ν 3046(w), 2914(w), 2358(m), 1479-

¹J(Pt,Pt) ) 1810 Hz, J(Pt,P) ) 67 Hz, J(P,P) ) 71 Hz).

2

3

3.3.2. Reactivity toward dppm. To a solution of 4 (0.13 mmol) in

methylene chloride (5 mL) was added a solution of dppm (150 mg,

0.78 mmol) in methylene chloride (2 mL) dropwise with stirring at

-70 °C. During the addition of the ligand, the color of the reaction

mixture changed to dark-red. After warming up to room temperature,

the color changed to light-yellow. The solvent was removed under

vacuo, and the residue was washed with n-pentane/diethyl ether (3/1

mL). This residue was purified by preparative centrifugal thin layer

chromatography using at first using n-pentane/diethyl ether (5/1), then

chloroform/acetone (2/1), and finally chloroform/acetone/methanol (6/

6/1) to elute the phosphines, [(PtL)₂(µ-SMe)(µ-dppm)]Cl (12), and ([Pt-

(m), 1434(s), 1096(s), 743(m), 693(s), 528(s) cm^-1

.

3.3.3. Reactivity toward Br₂and I₂. To a solution of 4a (200 mg,

0.13 mmol) in methylene chloride (5 mL) cooled down to -70 °C

was slowly added a solution of the requisite halogen (0.13 mmol) in

methylene chloride (5 mL) with rigorous stirring to avoid a local

overdose. After each drop, the color of the mixture changed from yellow

to brown and back to yellow. The solution was allowed to warm to

room temperature, and the solvent was removed under vacuo. The

9

4564 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Alkylthio Bridged 44 cve Triangular Platinum Clusters

A R T I C L E S

Table 4. Crystallographic and Data Collection Parameters for

Complexes 4a‚4CHCl₃, 5c‚2CHCl₃, and 6‚Me₂CO

residue was purified by preparative centrifugal thin layer chromatog-

raphy using chloroform/acetone/methanol (1/1/1) followed by recrys-

tallization from methylene chloride/diethyl ether (5/2 mL) ([{PtBr-

(PPh₃)}₂(µ-SMe)₂] (14a)) or chloroform/diethyl ether solutions (5/2 mL)

([{PtI(PPh₃)}₂(µ-SMe)₂] (14b)). After 2 days, yellow, air-stable crystals

were filtered off, washed with pentane (10 mL), and dried in vacuo.

[{PtBr(PPh₃)}₂(µ-SMe)₂] (14a). Yield: 130 mg (57%). T_dec: 194

°C. Found: C, 39.34; H, 3.52; S, 5.60. C₃₈H₃₆P₂S₂Br₂Pt₂(1165.94)

4a·4CHCl₃

5c·2CHCl₃

6·Me₂CO

empirical formula

C₆₁H₅₈Cl₁₃P₃- C₅₀H₄₂As₂Cl₈- C₇₈H₇₂ClOP₃-

Pt₃S₃

Pt₂S₂

Pt₃S₄

M_r/g·mol^-1

crystal size (mm)

2026.28

1530.58

1867.23

0.61 × 0.32 × 0.22 × 0.18 × 0.22 × 0.15 ×

0.10

monoclinic

P2₁/n

0.16

monoclinic

P2₁/n

0.15

monoclinic

P2₁/n

crystal system

space group

a/Å

b/Å

c/Å

1

requires C, 39.11; H, 3.11; S, 5.48. H NMR (200 MHz, CD₂Cl₂): δ

14.483(2)

26.555(5)

18.961(3)

95.12(2)

7263(2)

4

9.194(2)

17.693(3)

16.586(4)

99.37(3)

2662.1(1)

2

28.655(7)

15.065(2)

18.692(5)

88.07(3)

2662.1(1)

4

3

4

2.67 (t+dt, J(Pt,H) ) 33.2 Hz, J(P,H) ) 5.8 Hz, 3H, CH₃), 2.77

(t+dt, ³J(Pt,H) ) 34.9 Hz, ⁴J(Pt,H) ) 5.8 Hz, 3H, CH₃), 7.31 (m, 18H,

Ph), 7.57 (m, 12H, Ph). ¹³C NMR (50 MHz, CD₂Cl₂): δ 14.4 (s(br),

â/deg

V/Å³

Z

3

CH₃), 19.1 (t, J(P,C) ) 16.8 Hz, CH₃), 128.3 (m, m-CH), 130.1 (′t′,

N ) 116.7 Hz, i-C), 131.0 (s, p-CH), 134.7 (m, o-CH). ³¹P NMR (81

D

_calc/g·cm^-1

1.853

1.909

1.538

1

2

MHz, CD₂Cl₂): δ 14.8 (s+m, J(Pt,P) ) 3298 Hz, J(Pt,Pt) ) 820

Hz, ³J(Pt,P) -2 Hz, ⁴J(P,P) ) 7.0 Hz). IR: ν 3051(w), 2914(w), 2019-

(w), 1480(m), 1434(s), 1303(w), 1183(w), 1158(w), 1096(s), 1027-

µ(Mo K_R)/mm^-1

F(000)

6.431

6.997

5.427

3888

1464

3632

θ range/deg

2.00-25.00

2.30-25.00

1.96-25.00

(w), 998(w), 957(m), 744(s), 706(s), 692(s), 535(s), 513(s), 498(s) cm^-1

.

refln. collected

refln. observed

[I > 2σ(I)]

49731

18554

57386

12113

4667

14180

[{PtI(PPh₃)}₂(µ-SMe)₂] (14b). Yield: 110 mg (45%). T_dec: 237 °C.

Found: C, 36.22; H, 3.00; S, 4.91. C₃₈H₃₆P₂S₂I₂Pt₂(1261.91) requires

C, 36.14; H, 2.88; S, 4.91. ¹H NMR (200 MHz, CD₂Cl₂): δ 2.75 (t+dt,

³J(Pt,H) ) 36.4 Hz, ⁴J(P,H) ) 5.3 Hz, 3H, CH₃), 3.06 (t+dt, ³J(Pt,H)

refln. independent

9797

3799

10264

data/parameters/restraints 12113/748/0

4667/289/0

0.984

14180/813/0

0.956

goodness-of-fit on F²

R1 (∑)/R1 (I > 2σ(I))

1.026

0.0410/0.0291 0.0395/0.0286 0.0679/0.0436

4

) 38.4 Hz, J(P,H) ) 5.6 Hz, 3H, CH₃), 7.31 (m, 18H, Ph), 7.60 (m,

wR2 (∑)/wR2 (I > 2σ(I)) 0.0747/0.0673 0.0709/0.0673 0.1231/0.1116

12H, Ph). ¹³C NMR (50 MHz, CD₂Cl₂): δ 10.1 (s(br), CH₃), 19.0 (s(br),

CH₃), 128.2 (m, m-CH), 130.9 (s, p-C), 131.3 (s(br), i-C), 134.8 (m,

largest diff. peak

1.379/-1.531 0.806/-0.827 2.469/-1.152

and hole/e·Å^-3

T_min/T_max

0.111/0.566 0.370/0.500 0.383/0.501

1

o-CH). ³¹P NMR (81 MHz, CD₂Cl₂): δ 14.9 (s+m, J(Pt,P) ) 3239

Hz, ²J(Pt,Pt) ) 960 Hz, ³J(Pt,P) -2 Hz, ⁴J(P,P) ) 8 Hz). IR: ν 3048-

(w), 2962(w), 1479(m), 1433(s), 1302(w), 1184(w), 1096(s), 997(w),

Table 5. Crystallographic and Data Collection Parameters for

Complexes 12b‚2H₂O and 14b‚CHCl₃

954(m), 744(m), 707(m), 691(s), 536(s), 511(s), 494(s) cm^-1

.

3.3.4. Reactivity toward Chalcogens. A solution of 4a (400 mg,

0.26 mmol) and sulfur (8 mg, 0.25 mmol) in benzene (7 mL) and a

suspension of 4a (400 mg, 0.26 mmol) and selenium (20 mg, 0.25

mmol) in benzene (7 mL), respectively, were heated up to 70 °C for

48 h. The color of the solution changed from yellow to brown. After

cooling to room temperature, the solvent was removed under vacuum.

The crude product was purified by preparative centrifugal thin layer

chromatography using chloroform/acetone (1/1) followed by reprecipi-

tation from chloroform/n-pentane solutions (2/5 mL). After 2 days,

brown, air-stable powders were filtered, washed with pentane (10 mL),

and dried in vacuo.

12a

14a·CH₂Cl₂

empirical formula

M_r/g·mol^-1

crystal size (mm)

crystal system

space group

a/Å

C

₆₂H₅₅ClP₄Pt₂S

C₃₉H₃₈Br₂Cl₂P₂Pt₂S₂

1253.65

1381.63

0.28 × 0.23 × 0.20

monoclinic

P2₁/n

11.293(1)

29.191(5)

16.471(2)

90.00

91.44(2)

90.00

5428.1(1)

4

0.75 × 0.37 × 0.37

triclinic

P1h

11.350(2)

13.561(3)

14.212(3)

98.75(2)

112.40(2)

92.88(3)

1984.6(7)

2

b/Å

c/Å

R/deg

â/deg

γ/deg

V/Å³

[{Pt(PPh₃)}₃(µ₃-S)(µ-SMe)₃]Cl (15a). Yield: 200 mg (47%).

Found: C, 39.55; H, 3.67; S, 8.40. C₅₇H₅₄S₄P₃ClPt₃‚CH₂Cl₂(1663.05)

Z

D

_calc/g·cm^-1

1.691

5.394

2704

2.098

9.403

µ(Mo K_R)/mm^-1

1

requires C, 41.85; H, 3.39; S, 7.69. H NMR (200 MHz, CDCl₃): δ

F(000)

1188

2.10 (s+d,³J(Pt,H) ) 50.6 Hz, CH₃), 7.34 (m(br), 45H, Ph). ¹³C NMR

(100 MHz, CDCl₃): δ 20.5 (s(br), SCH₃), 128.6 (m, m-CH), 130.7

(m, i-C), 131.4 (s, p-CH), 133.6 (m, o-CH). ³¹P NMR (81 MHz,

CDCl₃): δ 8.7 (s+m, ¹J(Pt,P) ) 3808 Hz, ²J(Pt,Pt) ) 480 Hz, ³J(Pt,P)

) -40 Hz, ⁴J(P,P) ) 6 Hz). ESI-MS: m/z (obsd/calcd for [{Pt-

(PPh₃)}₃(µ₃-S)(µ-SMe)₃]⁺, %) 1540 (4/2), 1541 (12/11), 1542 (32/35),

1543 (76/71), 1544 (90/95), 1545 (100/100), 1546 (79/85), 1547 (62/

65), 1548 (42/43), 1549 (23/26), 1550 (14/13), 1551 (6/7). IR: ν 3048-

(w), 2911(w), 2362(m), 2337(m), 1480(m), 1434(s), 1383(w), 1096(s),

θ range/deg

refln. collected

2.16-25.00

1.97-25.91

15269

23191

9301

7344

refln. observed [I > 2σ(I)]

refln. independent

data/parameters/restraints

goodness-of-fit on F²

R1 (∑)/R1 (I > 2σ(I))

wR2 (∑)/wR2 (I > 2σ(I))

largest diff. peak

and hole/e·Å^-3

7082

6397

9301/632/0

1.036

0.0593/0.0439

0.1223/0.1080

1.185/-2.792

7082/443/0

1.077

0.0478/0.0423

0.1218/0.1148

1.888/-3.218

T_min/T_max

0.335/0.444

0.031/0.113

747(m), 693(s), 534(s) cm^-1

.

[{Pt(PPh₃)}₃(µ₃-Se)(µ-SMe)₃]Cl (15b). Yield: 160 mg (38%).

1

T

_dec: 152 °C. H NMR (200 MHz, CDCl₃): δ 2.03 (s+d³J(Pt,H) )

3.4. X-ray Crystal Structure Determinations. Intensity data were

collected on Stoe-IPDS and Stoe-IPDS-2 diffractometers using graphite

monochromatized Mo K_Rradiation (λ ) 0.71073 Å) at 220(2) K (4a‚

4CHCl₃, 5c‚2CHCl₃, 6‚Me₂CO, 14b‚CHCl₃) and 153 K (12b‚2H₂O),

respectively. A summary of the crystallographic data, the data collection

parameters, and the refinement parameters are given in Tables 4 and

5. Absorption corrections were applied numerically. The structures were

solved by direct methods with SHELXS-97 and refined using full-matrix

least-squares routines against F²with SHELXL-97.³⁶All non-hydrogen

52.3 Hz, CH₃), 7.30 (m(br), 45H, Ph). ¹³C NMR (100 MHz, CDCl₃):

δ 22.3 (s(br), SCH₃), 128.6 (m, m-CH), 131.1 (m, i-C), 131.6 (s, p-CH),

133.8 (m, o-CH). ³¹P NMR (81 MHz, CDCl₃): δ 5.9 (s+m, ¹J(Pt,P) )

3937 Hz, J(Pt,Pt) ) 400 Hz, J(Pt,P) ) -38 Hz, J(P,P) ) 5 Hz).

ESI-MS: m/z (obsd/calcd for [{Pt(PPh₃)}₃(µ₃-Se)(µ-SMe)₃]⁺, %) 1585

(2/3), 1586 (8/7), 1587 (19/17), 1588 (32/31), 1589 (60/51), 1590 (80/

72), 1591 (92/92), 1592 (100/100), 1593 (90/95), 1594 (76/78), 1595

(56/59), 1596 (38/39), 1597 (22/24), 1598 (12/13), 1599 (6/7). IR: ν

3053(w), 2959(w), 2911(w), 1549(m), 1530(m), 1480(m), 1434(s),

1302(w), 1185(w), 1096(s), 998(w), 951(w), 748(m), 693(s), 534(s)

2

3

4

(36) Sheldrick, G. M. SHELXS-97, SHELXL-97, Programs for Crystal Structure

Determination, University of Go¨ttingen: Go¨ttingen, 1990/1997.

cm^-1

.

9

J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007 4565

A R T I C L E S

Albrecht et al.

atoms were refined with anisotropic displacement parameters. H atoms

were included to the models in calculated positions using the riding

model. Crystallographic data (excluding structure factors) for the

structures reported in this paper have been deposited at the Cambridge

Crystallographic Data Center (CCDC) as Supplementary Publication

No. CCDC-635203 (4a‚4CHCl₃), CCDC-635204 (5c‚2CHCl₃), CCDC-

635205 (6‚Me₂CO), CCDC-635206 (12b‚2H₂O), and CCDC-635207

(14b‚CHCl₃). Copies of the data can be obtained free of charge on

application to the CCDC, 12 Union Road, Cambridge, CB2 1EZ, U.K.

(fax, +44-1223-336033; E-mail, deposit@ccdc.cam.ac.uk).

3.5. Computational Details. All DFT calculations were performed

by employing the Gaussian98 program package³⁷using the

MPW1PW91³⁸functional. A triple-ú valence basis set was used for Pt

with a polarization function added (TZVP) as provided by Ahlrichs

and co-workers.³⁹For its core orbitals, an effective core potential with

consideration of relativistic effects has been used.⁴⁰For all other atoms,

a split-valence basis set with polarization functions (P, S atoms:

6-31G*) and without polarization functions (C, H atoms: 3-21G) were

used. The appropriateness of the functional in combination with the

basis sets and effective core potential used for reliable interpretation

of the electron density and structural aspects has been demonstrated.⁴¹

The AIM analysis as well as the visualization were performed using

the program package AIMPAC as provided by Bader et al.⁴²All systems

have been optimized in C₃symmetry. The resulting geometries were

characterized as equilibrium structures by the analysis of the force

constants of normal vibrations.

Acknowledgment. Financial support from the Deutsche

Forschungsgemeinschaft and gifts of chemicals from Merck

(Darmstadt) are gratefully acknowledged.

Supporting Information Available: Energies and Cartesian

coordinates of atom positions of the calculated cations [{Pt-

(PPh₃)}₃(µ-SMe)₃]⁺(4a′) and [{Pt(PPh₃)}₃(µ₃-S)(µ-SMe)₃]⁺

(15a′). Crystallographic information files (cif) of the structures

of [{Pt(PPh₃)}₃(µ-SMe)₃]Cl‚4CHCl₃(4a‚4CHCl₃), [{PtCl-

(AsPh₃)}₂(µ-SPh)₂]‚2CHCl₃(5c‚2CHCl₃), [{Pt(PPh₃)}₃(µ₃-S)-

(µ-SBn)₃]Cl‚Me₂CO (6‚Me₂CO), [{Pt(PPh₃)}₂(µ-SMe)(µ-dppm)]-

Cl (12a), and [{PtBr(PPh₃)}₂(µ-SMe)₂]‚CH₂Cl₂(14a‚CH₂Cl₂).

(37) Frisch, M. J.; et al. Gaussian98, revision A.9; Gaussian Inc.: Pittsburgh,

PA, 1998.

(38) Adamo, C.; Barone, V. Chem. Phys. Lett. 1997, 274, 242.

(39) Schaefer, A.; Huber, C.; Ahlrichs, R. J. Chem. Phys. 1994, 100(8), 5829.

(40) Andrae, D.; Haeussermann, U.; Dolg, M.; Stoll, H.; Preuss, H. Theor. Chim.

Acta 1990, 77, 123.

JA068476R

(41) Schwieger, S.; Wagner, C.; Bruhn, C.; Schmidt, H.; Steinborn, D. Z. Allg.

Anorg. Chem. 2005, 631, 2696.

(42) http://www.chemistry.mcmaster.ca/aimpac/, 2000. The program was slightly

changed to allow the appropriate number of basis functions.

9

4566 J. AM. CHEM. SOC. VOL. 129, NO. 15, 2007

Article Doi

Alkylthio bridged 44 eve triangular platinum clusters: Synthesis, oxidation, degradation, ligand substitution, and quantum chemical calculations

DOI: 10.1021/ja068476r

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