Diverse evolution of [{Ph2P(CH2)n PPh2}Pt(μ-S)2Pt {Ph2P(CH2)nPPh2}] (n = 2, 3) metalloligands in CH2Cl2

Article abstract of DOI:10.1021/ic0107173

The nucleophilicity of the {Pt₂S₂} core in [{Ph₂P(CH₂)_n PPh₂}Pt(μ-S)₂Pt{Ph₂ P(CH₂)_nPPh₂}] (n = 3, dppp (1); n = 2, dppe (2)) metalloli

Full text of DOI:10.1021/ic0107173

Inorg. Chem. 2002, 41, 3218−3229
Diverse Evolution of [{Ph2P(CH ) PPh2}Pt(µ-S)2Pt{Ph2P(CH ) PPh2}]
2 n
2 n
(n ) 2, 3) Metalloligands in CH Cl2
2
Rube´n Mas-Balleste´,† Merce` Capdevila,† Paul A. Champkin,‡ William Clegg,‡ Robert A. Coxall,‡
,†
Agust´ı Lledo´s,† Claire Me´gret,† and Pilar Gonza´lez-Duarte*
Departament de Qu´ımica, UniVersitat Auto`noma de Barcelona, E-08193 Bellaterra,
Barcelona, Spain, and Department of Chemistry, UniVersity of Newcastle,
Newcastle upon Tyne NE1 7RU, U.K.
Received July 6, 2001
The nucleophilicity of the {Pt2S } core in [{Ph2P(CH ) PPh2}Pt(µ-S)2Pt{Ph2P(CH ) PPh2}] (n ) 3, dppp (1); n )
2
2 n
2 n
2, dppe (2)) metalloligands toward the CH Cl2 solvent has been thoroughly studied. Complex 1, which has been
2
obtained and characterized by X-ray diffraction, is structurally related to 2 and consists of dinuclear molecules with
a hinged {Pt2S } central ring. The reaction of 1 and 2 with CH Cl2 has been followed by means of 31P, 1H, and
2
2
13C NMR, electrospray ionization mass spectrometry, and X-ray data. Although both reactions proceed at different
rates, the first steps are common and lead to a mixture of the corresponding mononuclear complexes [Pt{Ph2P-
(CH ) PPh2}(S CH )], n ) 3 (7), 2 (8), and [Pt{Ph2P(CH ) PPh2}Cl2], n ) 3 (9), 2 (10). Theoretical calculations
2 n
2
2
2 n
give support to the proposed pathway for the disintegration process of the {Pt2S } ring. Only in the case of 1, the
2
reaction proceeds further yielding [Pt2(dppp)2{µ-(SCH SCH S)-S,S′}]Cl2 (11). To confirm the sequence of the reactions
2
2
leading from 1 and 2 to the final products 9 and 11 or 8 and 10, respectively, complexes 7, 8, and 11 have been
synthesized and structurally characterized. Additional experiments have allowed elucidation of the reaction mechanism
involved from 7 to 11, and thus, the origin of the CH groups that participate in the expansion of the (SCH S)2-
2
2
ligand in 7 to afford the bridging (SCH SCH S)2- ligand in 11 has been established. The X-ray structure of 11 is
2
2
totally unprecedented and consists of a hinged {(dppp)Pt(µ-S)2Pt(dppp)} core capped by a CH SCH fragment.
2
2
Introduction
on the {Pt2S2} core and the varied coordination geometries
about the heterometal in complexes containing the [L2Pt-
(µ-S)2PtL2] metalloligand.4
Evolution of the chemistry of [L2Pt(µ-S)2PtL2] as a
metalloligand precursor to higher nuclearity aggregates has
proceeded so rapidly since the first report of [Pt2(PMe2Ph)4-
(µ-S)2] by Chatt and Mingos in 19701 that it appears difficult
to further extend the present knowledge of the synthesis and
structural aspects of the corresponding homo- and hetero-
metallic derivatives. The recent developments in the syn-
thesis, structures, and reactivities of sulfide-bridged aggre-
gates with the {Pt2S2} core have been excellently reviewed
by Fong and Hor,2 who have made important contributions
to this field.3 The high nucleophilicity of the bridging sulfur
atoms together with the flexible hinge angle between the two
PtIIS2 planes explains the large family of derivatives based
Despite the formidable body of structural and related data
on this family of compounds, several points remained open
to consideration. On one hand, the synthetic routes reported
for complexes of formula [L2Pt(µ-S)2PtL2] were not straight-
forward, reports on their crystal structures were scarce, and
most of the sulfide-bridged aggregates containing the {Pt2S2}
core had been achieved with PPh3 as terminal ligand.2,3 These
observations led us to report a convenient synthesis (90%
yield), monitored by means of 31P NMR, for [(dppe)Pt(µ-
(3) Selected recent references: (a) Li, Z.; Loh, Z.-H.; Mok, K. F.; Hor,
T. S. A. Inorg. Chem. 2000, 39, 5299. (b) Li, Z.; Xu, X.; Khoo, S. B.;
Mok, K. F.; Hor, T. S. A. J. Chem. Soc., Dalton Trans. 2000, 2901.
(c) Liu, H.; Jiang, C.; Yeo, J. S. L.; Mok, K. F.; Liu, L. K.; Hor, T.
S. A.; Yan, Y. K. J. Organomet. Chem. 2000, 595, 276. (d) Fong,
S.-W. A.; Vittal, J. J.; Henderson, W.; Hor, T. S. A.; Oliver, A. G.;
Rickard, C. E. F. Chem. Commun. 2001, 421.
* Corresponding author. E-mail: Pilar.Gonzalez.Duarte@uab.es.
† Universitat Auto`noma de Barcelona.
‡ University of Newcastle.
(1) Chatt, J.; Mingos, D. M. P. J. Chem. Soc. A 1970, 1243.
(2) Fong, S.-W. A.; Hor, T. S. A. J. Chem. Soc., Dalton Trans. 1999,
639.
(4) (a) Capdevila, M.; Clegg, W.; Gonza´lez-Duarte, P.; Jarid, A.; Lledo´s,
A. Inorg. Chem. 1996, 35, 490. (b) Aullo´n, G.; Ujaque, G.; Lledo´s,
A.; Alvarez, S.; Alemany, P. Inorg. Chem. 1998, 37, 804.
3218 Inorganic Chemistry, Vol. 41, No. 12, 2002
10.1021/ic0107173 CCC: $22.00 © 2002 American Chemical Society
Published on Web 05/17/2002

[{Ph2P(CH2)nPPh2}Pt(µ-S)2Pt{Ph2P(CH2)nPPh2}]
Scheme 1
S)2Pt(dppe)], its X-ray crystal structure,5 and the synthesis
and full structural characterization in the solid phase as well
as in solution by multinuclear NMR of a series of penta-
nuclear complexes of formula [M{Pt2(dppe)2(µ3-S)2}2],
(MII ) Zn, Cd, Hg, Cu).5,6 These constituted the first
examples structurally characterized by X-ray diffraction
where the heterometal is tetrahedrally coordinated to two
[L2Pt(µ-S)2PtL2] metalloligands.
Table 1. Complexes Obtained upon Exposure of [L2Pt(µ-S)2PtL2]
Metalloligands in CH2Cl2
Another question there has been insufficient information
to address is the reaction pathway by which the [L2Pt-
(µ-S)2PtL2] metalloligands react with organic electrophilic
agents, such as PhCH2Br1 and CH3I,7 as a consequence of
the nucleophilicity of the sulfide bridges. A particular case
of this well-established reaction is the surprising progression
of [L2Pt(µ-S)2PtL2] compounds when they are dissolved in
CH2Cl2.2 Thus, in recent years, several different species have
been characterized as a result of this reaction (Table 1). The
apparent dispersion of the compounds obtained, the lack of
a systematic study of the reactions involved and the possible
relationship between the nucleophilic character of the {Pt2S2}
core and the nature of the terminal ligands suggested to us
that this whole question deserves further analysis.
a dppf ) [FeC5H4PPh2)2]. b dppy ) PPh2(C5H5N).
Here we report a detailed study of the multistage pathway
followed in the reaction of the [(P∩P)Pt(µ-S)2Pt(P∩P)]
metalloligands, where P∩P ) dppe or dppp, with CH2Cl2,
Scheme 1. On the basis of multinuclear NMR, electrospray
ionization mass spectrometry (ESI MS), and X-ray crystal-
lographic data, we show that both reactions proceed at
different rates and eventually afford different products.
Overall, the complexity of the reaction of the [(P∩P)Pt-
(µ-S)2Pt(P∩P)] metalloligands with CH2Cl2 explains the
diversity of the compounds reported in closely related
systems, Table 1, and evidences the influence of the terminal
ligands on the reactivity of the {Pt(µ-S)2Pt} core.
(5) Capdevila, M.; Carrasco, Y.; Clegg, W.; Gonza´lez-Duarte, P.; Lledo´s,
A.; Sola, J.; Ujaque, G. J. Chem. Soc., Chem. Commun. 1998, 597.
(6) Capdevila, M.; Carrasco, Y.; Clegg, W.; Coxall, R. A.; Gonza´lez-
Duarte, P.; Lledo´s, A.; Ram´ırez, J. A. J. Chem. Soc., Dalton Trans.
1999, 3103.
(7) (a) Ugo, R.; La Monica, G.; Cenini, S.; Segre, A.; Conti, F. J. Chem.
Soc. A 1971, 522. (b) Briant, C. E.; Gardner, C. J.; Hor, T. S. A.;
Howells, N. D.; Mingos, D. M. P. J. Chem. Soc., Dalton Trans. 1984,
2645.
Inorganic Chemistry, Vol. 41, No. 12, 2002 3219

Mas-Balleste´ et al.
Table 2. Crystal Data, Data Collection, and Refinement for Complexes
1, 7, and 11
Experimental Section
Materials and Methods. All the manipulations were carried out
at room temperature under an atmosphere of pure dinitrogen, and
conventionally dried and degassed solvents were used throughout.
These were Purex Analytical Grade from SDS. Metal complexes
of formula [PtCl2(P∩P)], P∩P ) dppe or dppp, were prepared
according to published methods.13 The synthesis of [(dppe)Pt-
(µ-S)2Pt(dppe)] (2) has already been reported.5
1‚Me2CO
7‚MeCN
11‚1.5PhMe
formula
fw
C57H58OP4Pt2S2 C30H35NP2PtS2 C66.5H68Cl2P4Pt2S3
1337.2
730.7
1548.4
cryst size, mm3 0.7 × 0.3 × 0.2 0.4 × 0.3 × 0.2 0.24 × 0.18 × 0.08
space group
a, Å
b, Å
P21/c
P21/c
P21/c
22.025(8)
14.753(5)
16.502(5)
101.470(14)
5255(3)
4
1.690
55.6
0.0305
9.8365(5)
16.6498(9)
17.7108(9)
100.589(1)
2851.2(3)
4
1.702
52.0
0.0226
13.8539(5)
13.0377(5)
34.1386(13)
91.7764(6)
6163.3(4)
4
1.669
48.7
0.0464
c, Å
Elemental analyses were performed on a Carlo-Erba CHNS EA-
1108 analyzer. The microanalytical data for crystals of 11 have
been omitted because they are unsatisfactory, as already found in
some related phosphine platinum complexes.14 1H, 13C{1H}, and
31P{1H} NMR spectra of the complexes 1, 2, and 7-11 and the
31P{1H} NMR spectrum of 11′ (E + E′ in Scheme 2) were recorded
from samples in (CD3)2SO solution at room temperature using a
Bruker AC250 spectrometer. 13C and 1H chemical shifts are relative
to SiMe4, and 31P chemical shifts, to external 85% H3PO4. The 2H
NMR spectrum of 11′ was recorded from (CH3)2SO solution using
â, deg
V, Å3
Z
F
calcd, g cm-3
µ, cm-1
R(F)a
(F2 > 2σ(F2))
Rw(F2)b
(all data)
0.0543
0.0532
0.0982
2
2
a R(F) ) ∑||Fo| - |Fc||/|∑|Fo|. b Rw(F2) ) [∑[w(Fo - Fc )2]/
∑[w(Fo)2]]1/2
.
1
a Bruker AM400 spectrometer, and the H NMR spectrum was
recorded from (CD3)2SO solution using a Bruker Avance500. The
31P{1H} NMR spectra of 1, 2, and 3 were simulated on a Pentium-
200 computer using the gNMR V4.0.1 program by P. H. M.
Budzelaar from Cherwell Scientific Publishing.15
50.83; H, 4.29; S, 5.12. X-ray quality crystals of this compound
were obtained by slow evaporation of a solution of 1 in acetone.
[Pt(dppp)(S2CH2)] (7). To a suspension of Na2S‚9H2O (0.35 g,
1.6 mmol) in benzene (50 mL) were added solid [PtCl2(dppp)] (0.10
g, 0.15 mmol) and CH2Cl2 (0.5 mL, 7.8 mmol) with stirring. After
24 h, the excess Na2S‚9H2O and the white solid formed, NaCl,
were filtered off. The filtrate was concentrated to dryness, giving
a yellow solid. Recrystallization in acetonitrile afforded a yellow
crystalline solid. Yield 43%. Anal. Calcd for C28H28P2PtS2‚CH3-
CN: C, 49.58; H, 4.30; N, 1.93; S, 8.82. Found: C, 48.79; H, 4.20;
N, 2.22; S, 8.90. A single crystal was chosen for X-ray diffrac-
tion.
[Pt(dppe)(S2CH2)] (8). Using the same procedure as that
indicated for complex 7, a yellow solid was obtained from the
reaction of [PtCl2(dppe) (0.085 g, 0.1 mmol) with Na2S‚9H2O
(0.175 g, 0.8 mmol) and CH2Cl2 (0.5 mL, 7.8 mmol) in a benzene
solution (25 mL). Yield 67%. Anal. Calcd for C27H26P2PtS2: C,
48.28; H, 3.90; S, 9.55. Found: C, 48.03; H, 4.10; S, 10.15.
Recrystallization of 8 in acetone allowed isolation of yellow crystals.
Unfortunately, the diffraction data were very weak and of inferior
quality compared to those of 7, allowing only a qualitative structure
analysis.
To analyze the course of the reaction of 1 or 2 in CH2Cl2, a
solution of 50 mg of the corresponding pure compound in 25 mL
of solvent was prepared at room temperature. At different times,
aliquots were taken from the solution, they were evaporated to
dryness, and the 1H, 13C, and 31P NMR spectra of a fraction of the
solid residue dissolved in d6-DMSO were recorded. Another fraction
was used in order to determine the mass of the species present by
means of ESI MS measurements. These were performed on a VG
Quattro Micromass Instrument. Experimental conditions were as
follows: 10 µL of sample was injected at 15 µL/min; capillary-
counter electrode voltage, 4.5 kV; lens-counter electrode voltage,
1.0 kV; cone potential, 55 V; source temperature, 90 °C; m/z range,
300-1600. The carrier was acetonitrile for the spectra recorded
during the reaction of 1, 2, or 7 with CH2Cl2 or a 1:1 mixture of
acetonitrile and water containing 1% formic acid in the case of the
pure 1, 2, 7, 8, and 11 complexes. ESI MS data provided evidence
for the formation of 3, 4, and 5.
[Pt2(dppp)2(µ-S)2] (1). [PtCl2(dppp)] (0.20 g, 0.3 mmol) was
added to a benzene solution (75 mL) of Na2S‚9H2O (0.35 g, 1.6
mmol) and the mixture stirred at room temperature for 8 h. These
[Pt2(dppp)2{µ-(SCH2SCH2S)-S,S′}]Cl2 (11). A pure solid sample
of 7 (0.05 g, 0.07 mmol) was added to CH2Cl2 (5 mL) with stirring.
After several days, the solution was concentrated to dryness
affording a pale yellow solid. The residue was redissolved in
toluene, and the filtered solution was concentrated to yield the
expected product as a pale yellow solid, which was filtered and
dried. Recrystallization of 11 from toluene gave colorless crystals
suitable for X-ray diffraction.
reaction conditions were fixed after monitoring the reaction by 31
P
NMR, as already reported for the dppe analogue.6 The excess Na2S‚
9H2O, the formed NaCl, and the [PtCl2(dppp)] which did not react
were filtered off. The solvent was removed under vacuum from
the filtrate to yield the product as an orange solid. Yield 84%. Anal.
Calcd for C54H52P4Pt2S2: C, 50.70; H, 4.10; S, 5.01. Found: C,
To carry out the study of the mechanism involved in the reaction
from 7 to 11, 30 mg of 7 were dissolved in 1 mL of CD2Cl2. By
a similar procedure as that followed for 11, 15 mg (50% yield) of
11′ were obtained. Characterization of this solid was made by
multinuclear NMR spectroscopy.
(8) Gukathasan, R. R.; Morris, R. H.; Walker, A. Can. J. Chem. 1983,
61, 2490.
(9) Zhou, M.; Lam, C. F.; Mok, K. F.; Leung, P.-H.; Hor, T. S. A. J.
Organomet. Chem. 1994, 476, C32.
(10) Shaver, A.; Lai, R. D.; Bird, P. H.; Wickramasinghe, W. Can. J. Chem.
1985, 63, 2555.
X-ray Crystallographic Characterization of Complexes 1, 7,
and 11. A summary of crystal data, data collection, and refinement
parameters for the three structural analyses is given in Table 2.
Crystals were examined on a Bruker AXS SMART CCD area-
detector diffractometer with graphite-monochromated Mo KR
radiation (λ ) 0.71073 Å); measurements were made at 160 K.
Cell parameters were obtained from a least-squares fit on the
observed setting angles of all significant intensity reflections.
(11) Yam, V. W.-W.; Kok-Yan, P.; Cheung, K.-K. J. Chem. Soc., Chem.
Commun. 1995, 267.
(12) Zhou, M.; Leung, P.-H.; Mok, K. F.; Hor, T. S. A. Polyhedron 1996,
15, 1737.
(13) Brown, M. P.; Puddephatt, R. J.; Rashidi, M.; Seddon, K. R. J. Chem.
Soc., Dalton Trans. 1977, 951.
(14) Capdevila, M.; Gonza´lez-Duarte, P.; Foces-Foces, C.; Hernandez-Cano,
F.; Mart´ınez-Ripoll, M. J. Chem. Soc., Dalton Trans. 1990, 143.
(15) Budzelaar, P. H. M. gNMR V4.01; Cherwell Scientific Publishing
Ltd.: Oxford, UK, 1997.
3220 Inorganic Chemistry, Vol. 41, No. 12, 2002

[{Ph2P(CH2)nPPh2}Pt(µ-S)2Pt{Ph2P(CH2)nPPh2}]
Table 3. ESI MS and NMR Data for Complexes 1-5 and 7-11
δP
1JPt-P
(Hz)
δH(SCH2)
(ppm)
3JPt-H(SCH2)
δC(SCH2)
(ppm)
cmpd
m/z
calcd MWa
(ppm)
(Hz)
1
2
3
1279.7
1251.7
1328.2
1279.13
1251.18
1328.66
-0.08b
40.5c
2615b
2740c
PA: 2.1d
PB: 1.6
PA: 46.2
PB: 45.3
Pt-PA: 2410d
Pt-PB: 3165
Pt-PA: 2678
Pt-PB: 3421
4.19
4.10
28
?
54.6
?
4
1300.0
1300.61
5
7
8
9
10
11
646.7e
686.4
671.9
1293.21
685.68
671.65
-2.25
39.4
-3.7
43.4
2705
2824
3408
3610
2909
5.45
5.93
37
34
38.6
41.9
669.5e
1341.31
-0.14
4.19
37.1
a Only the neutral or cationic complex species is considered. b 31P RMN parameters from the computer simulation for 1: δP ) -0.07 ppm; 1JPt-P ) 2612
2
3
4
d
Hz; JPt-Pt ) 758 Hz; JPt-P ) 28 Hz; JP-P ) 22 Hz. c From ref 6. 31P RMN parameters from the computer simulation for 3: δPA ) 2.0 ppm; δPB
)
1
1
2
3
3
4
4
1.7 ppm; JPt-P(A) ) 2412 Hz; JPt-P(B) ) 3164 Hz; JPt-Pt ) 750 Hz; JPt-P(A) ) 42 Hz; JPt-
4JP(A)-P(B) ) 26 Hz. e M ) m/z (z ) 2).
) 33 Hz; JP(A)-P(A) ) 21 Hz; JP(B)-P(B) ) 23 Hz;
P(B)
Intensities were integrated from a series of 0.3° ω rotation frames
covering at least a hemisphere of reciprocal space and were
corrected for absorption and other effects by semiempirical methods
based on redundant and symmetry-equivalent reflections.16
The structures were solved by direct methods and were refined
by full-matrix least-squares on all unique F2 values, with anisotropic
displacement parameters for non-hydrogen atoms and with isotropic
H atoms constrained with a riding model.17 The largest residual
electron density peaks were close to Pt atoms in each case. One
toluene solvent molecule in the structure of 11 is disordered over
an inversion center.
A 6-31G basis set was used for the C and H atoms.22 Solvent effects
were taken into account by means of PCM calculations23 using
standard options of PCM and cavity keywords.18 Free energies of
solvation were calculated with CH2Cl2 (ꢀ ) 8.93) as sol-
vent, keeping the geometry optimized for the isolated species
(single-point calculations). Very recently, this approach has been
successfully applied to the study of bimetallic polysulfides Cp2-
Fe2S4.24
Results and Discussion
Experimental Study of the Reaction Pathway from 1
to 9 and 11, and from 2 to 8 and 10. The first information
obtained on the reaction of [(dppp)Pt(µ-S)2Pt(dppp)] (1) in
CH2Cl2 (Scheme 1) was the series of 31P NMR spectra
recorded as a function of time (Figure 1). They indicated
that 1 evolved to [(dppp)Pt(µ-S)(µ-SCH2Cl)Pt(dppp)]Cl (3),
which immediately transformed into a mixture of [Pt(dppp)-
(S2CH2)] (7) and [Pt(dppp)Cl2] (9). Then, while the latter
remained unchanged, 7 disappeared to give rise to [Pt2-
(dppp)2{µ-(SCH2SCH2S)-S,S′}]Cl2 (11). However, the ap-
parent complexity of this process together with the simul-
taneous presence of several species throughout the time since
the exposure of 1 to CH2Cl2 made it necessary to obtain 1H
and 13C NMR and ESI MS complementary data. NMR
parameters and ESI-MS mass determinations for compounds
1-11 are shown in Table 3.
The main bond distances and angles for these complexes are
given in Table 5.
Computational Details. Calculations were performed with the
GAUSSIAN 98 series of programs.18 The DFT (density functional
theory) was applied with the B3LYP function.19 Effective core
potentials (ECPs) were used to represent the innermost electrons
of the platinum atom20a as well as the electron core of P, S, and Cl
atoms.20b The basis set for the metal was that associated with the
pseudopotential,20a with a standard double-ú LANL2DZ contrac-
tion.18 The basis set for the P, S, and Cl atoms was that associated
with the pseudopotential,20b with a standard double-ú LANL1DZ
contraction18 supplemented with a set of d-polarization functions.21
(16) Sheldrick, G. M. SADABS; Bruker AXS: Madison, WI, 1997.
(17) Sheldrick, G. M. SHELXTL, Version 5; Bruker AXS: Madison, WI,
1994.
(18) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R.
L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara,
A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B. G.;
Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon, M.; Replogle,
E. S.; Pople, J. A. Gaussian 98, revision A.6; Gaussian, Inc.:
Pittsburgh, PA, 1998.
The 31P NMR spectrum of 1 shows the same features as
that of 2 already reported,6 in good concordance with their
similar structures in the solid phase.5 In 1 and 2, all the 31
P
nuclei show the same chemical shift but are not magnetically
equivalent. Interpretation of these spectra with the aid of
computer simulations requires consideration of second-order
3
effects due to 2JPt-Pt, JPt-P, and 4JP-P couplings. On the basis
1
of H and 13C DEPT135 NMR data, it was reasonable to
assume that the first species formed as a result of the
(19) (a) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. 1988, B37, 785. (b)
Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (c) Stephens, P. J.;
Delvin, F. J.; Chabalowski, C. F.; Frisch, M. J. J. Phys. Chem. 1994,
98, 11623.
(22) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972, 56,
2257.
(20) (a) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299. (b) Wadt,
W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284.
(21) Ho¨llwarth, A.; Bo¨hme, M.; Dapprich, S.; Ehlers, A. W.; Gobbi, A.;
Jonas, V.; Ko¨hler, K. F.; Stegman, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 237.
(23) (a) Tomasi, J.; Persico, M. Chem. ReV. 1994, 94, 2027. (b) Amovilli,
C.; Barone, V.; Cammi, R.; Cance`s, E.; Cossi, M.; Mennucci, B.;
Pomelli, C. S.; Tomasi, J. AdV. Quantum Chem. 1998, 32, 227.
(24) Blasco, S.; Demachy, I.; Jean, Y.; Lledo´s, A. New J. Chem. 2001, 25,
611.
Inorganic Chemistry, Vol. 41, No. 12, 2002 3221

Mas-Balleste´ et al.
Figure 1. (A) Progression of 1 in CH2Cl2 as a function of time monitored by 31P{1H} NMR. Spectra of the different aliquots were recorded in d6-DMSO.
(B) Analysis of the31P{1H} NMR spectra of 3.
nucleophilic attack of 1 to CH2Cl2 solvent involved the
binding of one CH2Cl fragment to a sulfide bridge while
the remaining chloride behaved as a counterion. ESI MS data
clearly confirmed that the new species, 3, could be formu-
lated as [1.CH2Cl]Cl (molecular weight of the cation of 3,
1328.66). Its 31P NMR spectrum consisting of only one signal
with four satellites was indicative of the asymmetry of 3,
thus corroborating the attack of only one CH2Cl2 molecule.
This spectrum, which is comparable to that reported for the
analogue with PPh3 as terminal ligand,8 could be interpreted
by considering that the two chemically nonequivalent 31P
nuclei in 3 show a very close chemical shift but different
1JPt-P values. This difference could be attributed to the
different nature and thus trans influence of the bridging S2-
3222 Inorganic Chemistry, Vol. 41, No. 12, 2002

[{Ph2P(CH2)nPPh2}Pt(µ-S)2Pt{Ph2P(CH2)nPPh2}]
or SCH2Cl- ligands. The chemical shift values δPA and δPB
were taken as the midpoint between the two satellites
corresponding to the 1JPt-P(A) and 1JPt-P(B) couplings, respec-
tively (Figure 1). These δPA, δPB, 1JPt-P(A), and 1JPt-P(B) values
were used for a full computer simulation, which allowed a
good match with the experimental spectrum.
Cl2 (6). While the 31P NMR parameters for 10 coincided
with those of [Pt(dppe)Cl2], already known as a precursor
of 2, complex 8 could be fully characterized as indicated
later. Analogously to complexes 7 and 9, the 31P NMR
spectra of 8 and 10 were consistent with a first-order analysis.
Overall, the first stages of the reaction of 1 or 2 with CH2-
Cl2 proceed at different rates but follow a common pathway,
independent of the diphosphine nature, to give a mixture of
two mononuclear complexes 7 and 9 or 8 and 10. However,
only in the case of dppp, the reaction does not stop at this
point, but there is a second electrophilic attack of CH2Cl2
on the thiolate sulfur of 7 to afford the final unprecedented
complex 11. These results indicate that dppp confers a greater
nucleophilicity to the sulfur atoms and are consistent with
the information obtained by theoretical calculations. The
proposed pathway is corroborated by the X-ray structures
of 1, 7, and 11 (8 only a qualitative analysis), which are in
good concordance with NMR data in solution, and by the
crystal structures of 2 and 12 previously reported.5,6
Theoretical Study of the Pathway from Bimetallic (1,
2) to Mononuclear Complexes (7, 9 and 8, 10). We have
performed DFT calculations in order to determine the
structural features of the intermediates and to obtain an
energetic picture of the process. In the calculations we have
modeled dppp and dppe real ligands by H2P(CH2)3PH2 (dhpp)
and H2P(CH2)2PH2 (dhpe), respectively. Thus, the different
species are labeled with the same number as the parent
compound but with an additional t. Their main geometric
parameters are collected in Table 4. The calculated structures
agree with the analogous products structurally characterized
in this work and with other related complexes reported in
the literature.7b,26-29
The analysis of the NPA (natural population analysis)
charges indicates that the sulfides in the dhpp containing
compounds have a slightly more negative charge than those
with dhpe. This is a consequence of the greater positive
charge supported by the dhpp ligand. Thus, sulfides in 1t
appear to be more nucleophilic than in 2t. The same feature
has been found for all the species from 1t to 7t if compared
with those from 2t to 8t.
The changes in the PPtP angle for both bidentate ligands
along the reaction pathway deserve further analysis. Data in
Table 4 show that the changes on the PPtP angle for the
dhpe ligands are small (from 85.0° in 6t to 88.4° in 10t) but
substantial in the case of dhpp (from 91.4° in 5t to 98.5° in
9t). Moreover, PPtP angles in dhpp are always closer to the
values found for unidentate, unconstrained systems. As a
consequence, dhpp appears to be more flexible, and the
corresponding complexes less strained than those with dhpe.
This fact may be the origin of the observed greater reactivity
ESI MS determinations not only led to the identification
of [(dppp)Pt(µ-S2CH2)Pt(dppp)]Cl2, 5 (molecular weight of
its cation, 1293.21), which was undetected by NMR mea-
surements run in parallel, but also evidenced the coexistence
in solution of 1, 3, 5, and 7. The 31P NMR spectra of the
subsequent species formed, 7 and 9, were consistent with a
first-order analysis and showed only one chemical shift for
each complex. This indicated that all the respective phos-
phorus nuclei were chemically and magnetically equivalent
in solution. Further reaction of 7 affords 11. On the basis of
the whole set of the spectroscopic data obtained for 11 (ESI
MS, 1H, 13C and 31P NMR), it was possible to determine its
structure, which would otherwise involve a second-order 31
P
NMR spectrum. However, in this complex, the second-order
effects appear to be small, and the 31P NMR spectrum allows
a first-order analysis. In addition, the only chemical shift
that is observed in this spectrum at room temperature
indicates a fast flipping of the thioether sulfur atom. 1H and
13C NMR data suggested that 7 and 11 included (SCH2S)2-
or (SCH2SCH2S)2- groups, respectively. The observation that
the 31P NMR parameters for 9 were coincident with those
of the precursor of 1 led to its identification as the
mononuclear [Pt(dppp)Cl2] species.13,25
Analogous to 1, the reaction of [(dppe)Pt(µ-S)2Pt(dppe)]
(2) with CH2Cl2 (Scheme 1) was followed by means of 31P
NMR spectra recorded as a function of time (Figure 2) and
additional 1H and 13C NMR data and ESI MS measurements.
The synthesis, X-ray structure, and NMR parameters of 2
have already been reported.5,6 The subsequent 31P NMR
spectra evidenced that 2 afforded [(dppe)Pt(µ-S)(µ-SCH2-
Cl)Pt(dppe)]Cl (4), which transformed into a mixture of [Pt-
(dppe)(S2CH2)] (8) and [Pt(dppe)Cl2] (10). Complexes 8 and
10 do not react further even if they are mixed at a 1:2 mole
ratio, which is the appropriate stoichiometric molar ratio to
obtain [Pt3(µ3-S)2(dppe)3]Cl2, 12, already reported.6 This
complex is obtained from a solution of 2 in either CH2Cl2
or CHCl3 containing traces of HCl.
Unlike 3, the 31P NMR spectrum of 4 showed two different
chemical shifts corresponding to two chemically inequivalent
phosphorus atoms, as already reported for a closely related
species containing dppf, [Fe(C5H4PPh2)2], instead of dppe
as terminal ligand.9 The 31P NMR spectrum allowed deter-
mination of the coupling constants involving not only P-Pt
(1JPt-P(A), 1JPt-P(B)) but also P-P (4JP(A)-P(B)) nuclei, as shown
in Table 3. However, at room temperature, the conversion
from 2 to 8 and 10 occurred in 2 h and thus hampered
recording the 13C NMR spectrum of 4 and determining
neither the mass nor the NMR spectral features of the
possible intermediate species [(dppe)Pt(µ-S2CH2)Pt(dppe)]-
(26) Bos, W.; Bour, J. J.; Schlebos, P. P. J.; Hageman, P.; Bosman, W. P.;
Smits, J. M. M.; van Wietmarschen, J. A. C.; Beurskens, P. T. Inorg.
Chim. Acta 1986, 119, 141.
(27) Fornie´s-Ca`mer, J.; Masdeu-Bulto´, A. M.; Claver, C.; Cardir, C. J.
Inorg. Chem. 1998, 37, 2626.
(28) Masdeu-Bulto´, A. M.; Ruiz, A.; Castillo´n S.; Claver, C.; Hitchcook,
P. B.; Chaloner, P. A.; Bo, C.; Poblet, J. M.; Sarasa, P. J. Chem. Soc.,
Dalton Trans. 1993, 2689.
(29) Elduque, A.; Finestra, C.; Lo´pez, J. A.; Lahoz, F. J.; Mercha´n, F.;
Oro, L. A.; Pinillos, M. T. Inorg. Chem. 1998, 37, 824.
(25) (a) Robertson, G. B.; Wickramasinghe, W. A. Acta Crystallogr., Sect.
C 1987, 43, 1694. (b) Farrar, D. H.; Ferguson, G. J. Crystallogr.
Spectrosc. Res. 1982, 12, 465.
Inorganic Chemistry, Vol. 41, No. 12, 2002 3223

Mas-Balleste´ et al.
Figure 2. Progression of 2 in CH2Cl2 as a function of time monitored by 31P{1H} NMR. Spectra of the different aliquots were recorded in d6-DMSO.
Table 4. Most Important Geometric Parametersaof the Optimized
Structures 1t-10t
of the dppe containing species compared to those containing
dppp. The influence of the bite angle of diphosphine ligands
on the stability and catalytic behavior of metal complexes
has been reviewed recently.30
structure Pt-S Pt-P Pt‚‚‚Pt S‚‚‚S Pt-S-Pt S-Pt-S θb P-Pt-P
1t
2t
3t
2.406 2.293 3.286 3.228
2.399 2.299 3.301 3.216
2.392 2.289 3.386 3.226
2.458 2.336
2.400 2.282 3.331 3.087
2.438 2.335
86.1
87.0
90.0
87.1
87.9
86.2
82.3
82.3
84.2
84.2
83.4
147.7
148.9
138.4
95.8
86.6
93.6
Moreover, we have calculated the thermodynamics of the
different steps of the reaction of 1t or 2t with dichloro-
methane by means of the polarizable continuum model
(PCM).23 If taking 1t + CH2Cl2 and 2t + CH2Cl2 as the
zero of energy, the first intermediates, (3t + Cl-) and (4t +
Cl-), are found 0.5 and 1.6 kcal/mol, respectively, above
the corresponding reactants, whereas the second intermedi-
4t
79.3
126.9
86.0
5t
6t
7t
8t
9t
2.476 2.317 3.260 2.840
2.470 2.318 3.251 2.842
70.0
70.2
76.1
76.1
106.9
107.1
91.4
85.0
92.8
85.6
98.5
88.4
2.380 2.313
2.376 2.317
2.257
2.933
2.928
10t
2.253
a Distances in angstroms; angles in degrees. b Dihedral angle between
the two PtS2 planes.
(30) Dierkes, P.; van Leeuwen, P. W. N. M. J. Chem. Soc., Dalton Trans.
1999, 1519.
3224 Inorganic Chemistry, Vol. 41, No. 12, 2002

[{Ph2P(CH2)nPPh2}Pt(µ-S)2Pt{Ph2P(CH2)nPPh2}]
ates, (5t + 2Cl-) and (6t + 2Cl-), lie 43.7 and 44.4 kcal/
mol, respectively, above the reactants. Monometallic com-
plexes are considerably stabilized: 27.2 kcal/mol (7t + 9t)
and 26.5 kcal/mol (8t + 10t) below the reactants. ∆G values
obtained for the second intermediates (more than 40 kcl/
mol) are hardly compatible with their experimental detection
at room temperature. However, the numerical values of the
relative energies in solution of species differently charged
(0 for the reactants, +1 and -1 for the first intermediate,
and +2 and -2 for the second one) can only be given a
semiquantitative significance. Calculations with inclusion of
solvent effects cannot be given the same accuracy as those
in the gas phase. When using the continuum model for the
solvent, as in the PCM method, energies are dependent on
the atomic radii used to define the cavity. This is especially
important for charged species of small size as the Cl- anion.
Even though this model hinders a quantitative determination
of the energies of the charged species, the reaction profile
obtained allows the following conclusions: (i) The driving
force for the reaction is the greater stability of the two
mononuclear compounds, 7t and 9t or 8t and 10t, with
respect to the corresponding reactants, 1t or 2t, by more than
25 kcal/mol. (ii) The stabilities of the two intermediates in
each of both reaction pathways are manifestly different.
Whereas the first intermediate has almost the same free
energy as the initial species, the second one appears as
significantly more unstable. Thus, the formation of the second
intermediate must be the rate-limiting step for the process.
Study of the Reaction Mechanism from 7 to 11. The
synthesis of 11 from 7 allowed characterization of the former
by X-ray, mass measurements, and corresponding NMR
parameters in solution (Table 3). The stoichiometric molar
ratio of 7 to CH2Cl2 in the reaction leading to 11 is 2:1.
This fully confirmed that the molar ratio of 9 to 11 in the
final solution obtained upon exposure of 1 in CH2Cl2 is 2:1,
as observed by NMR data. Complex 7 is stable in acetonitrile,
acetone, and methanol solvents even under open atmosphere.
However, upon exposure of 7 to CH2Cl2, it converts to the
final complex, 11. On one hand, the complete characteriza-
tion of 7 allowed confirmation of its existence as an
intermediate species in the reaction of 1 with CH2Cl2 to give
9 and 11 (Scheme 1). On the other, the direct synthesis of
11 by reacting 7 with CH2Cl2 evidenced its involvement in
this reaction. This finding, and comparison of the structures
of 7 and 11, raises the question of the source of the CH2
groups that participate in the expansion of the (SCH2S)2-
ligand in 7 to afford the bridging (SCH2SCH2S)2- ligand in
11. On the basis of all these data, we thought that replacement
of CH2Cl2 by CD2Cl2 in the synthesis of 11 from 7 could
cast light on the origin of these CH2 groups as well as the
mechanism involved in this reaction.
11′ and 11 indicated that the signal at 4.2 ppm, which is
due to the protons of the (SCH2SCH2S)2- ligand, decreased
by about 25% if the synthesis was run in CD2Cl2 instead of
CH2Cl2. Also, in the 2H NMR spectrum, there was only one
signal at 4.3 ppm, thus indicating the insertion of the CD2
group in the bridging ligand. These data showed that one-
fourth of the protons in the (SCH2SCH2S)2- ligand had been
replaced by deuterium. This allows the conclusion that for
each pair of 11 formed, one species contains (SCH2SCH2S)2-
and the other (SCH2SCD2S)2- as bridging ligands. Or, when
the reaction is run in CH2Cl2 to give [Pt2(dppp)2{µ-(SCH2-
SCH2S)-S,S′}]Cl2 (11), one-fourth of the CH2 groups of the
bridging ligand comes from the CH2Cl2 solvent and three-
fourths from the starting material, [Pt(dppp)(S2CH2)] (7). All
these observations are consistent with the reaction mechanism
proposed in Scheme 2.
Accordingly, the first step in the reaction of 7 with CD2-
Cl2 to give 11′, which comprises species E and E′, involves
the electrophilic attack of a CD2Cl2 molecule on one sulfur
atom of the dithiolate (SCH2S)2- ligand in 7. Then, cleavage
of the {PtS2C} ring in the intermediate species A yields a
mononuclear species B. This includes two (SCX2Cl)-
terminal ligands, one with X ) H and the other with X )
D. Although B has not been detected in this work, analogues
9
with PPh3 and dppf12 have been reported previously. Both
(SCX2Cl)- (X ) H or D) groups in B are capable of carrying
out an electrophilic attack on a second molecule of 7, but
only if this is done by (SCD2Cl)- will the CD2 fragment
from the initial CD2Cl2 molecule be inserted into the final
complex. Thus, the attack of B on 7 gives rise to the
intermediate species C and C′ where the formation of the
(SCH2SCX2S)2- (X ) H, D) ligand is already apparent. The
loss of the SCX2 fragment, which can afford possible
oligomeric forms,31 triggers formation of the intermediate
D and D′ species. The former was detected by ESI MS in
the reaction of 7 with the CH2Cl2 solvent. An internal
rearrangement of the Pt-S bonds in D and D′ yields the
final species E and E′, where the (SCH2SCX2S)2- ligand
bridges two {Pt(dppp)} units. Overall, the proposed mech-
anism (Scheme 2) accounts for the inherent ability of 7 to
react with the CH2Cl2 solvent and gives an insight into the
source of the CH2 groups, which give rise to the (SCH2S-
CH2S)2- ligand in the unprecedented complex 11.
The fact that none of the intermediate species involved in
the reaction mechanism is observed by 31P NMR suggests
that the evolution from 7 to A is the rate determining step.
To confirm this assumption, the reaction of 7 at different
concentrations in CH2Cl2 was monitored by 31P NMR. These
data were in good agreement with a pseudo-first-order rate
law, and the calculated rate constant (9.8 × 10-3 h-1) was
independent of the initial concentration of 7.
The reaction of 7 with CD2Cl2 was carried out by an
analogous procedure to that followed for the synthesis of
11, and the solid obtained, 11′, was analyzed by means of
Molecular Structures. The crystal structure of complex
1 consists of neutral dinuclear [(dppp)Pt(µ-S)2Pt(dppp)]
species devoid of crystallographic symmetry elements, and
acetone solvent molecules. Both types of molecules have only
1
2
the corresponding H, H, and 31P NMR spectra. The 31P
NMR parameters for 11′ were coincident with those of 11
(Table 3), thus confirming that the same reaction had taken
(31) Schmidt, M.; Weissflog, E. Angew. Chem., Int. Ed. Engl. 1977, 17,
1
place. However, the comparison of the H NMR spectra of
51.
Inorganic Chemistry, Vol. 41, No. 12, 2002 3225

Mas-Balleste´ et al.
Scheme 2
normal van der Waals interactions. Main geometric param-
eters for 1 (Figure 3) are given in Table 5. Each molecule
shows a hinged {Pt2S2} central ring, dihedral angle θ )
134.8°, with the two platinum atoms bridged by two sulfide
anions, coordination being completed by chelating dppp
ligands. Ignoring the phenyl rings and the H atoms of the
aliphatic carbon chains, the idealized symmetry of the {C3P2-
Pt(µ-S)2PtP2C3} core is C2V. It can be considered as formed
by three rings, the central {Pt2S2} one fused to two other
PtP2C3, which give rise to a butterfly structural type. Both
PtP2C3 rings show a distorted chair conformation. The
geometries at the individual Pt sites are approximately square
planar, deviations from planarity being less than 0.08 Å, and
the Pt-S and Pt-P bond distances agree well with those
3226 Inorganic Chemistry, Vol. 41, No. 12, 2002

[{Ph2P(CH2)nPPh2}Pt(µ-S)2Pt{Ph2P(CH2)nPPh2}]
Figure 3. Molecular structure of complex 1 with key atoms labeled and
with 50% probability ellipsoids. H atoms, phenyl rings, and the acetone
solvent molecule are omitted.
Table 5. Selected Bond Lengths (Å) and Angles (deg) for Complexes
1, 7, and 11
Complex 1
Pt(1)-S(1)
Pt(1)-S(2)
Pt(1)-P(1)
Pt(1)-P(2)
2.3505(13)
2.3392(14)
2.2704(14)
2.2566(15)
Pt(2)-S(1)
Pt(2)-S(2)
Pt(2)-P(3)
Pt(2)-P(4)
2.3318(14)
2.3379(14)
2.2342(15)
2.2546(15)
Figure 4. Molecular structure of complex 7 with key atoms labeled and
with 50% probability ellipsoids. H atoms and the acetonitrile solvent
molecule are omitted.
CH3CN molecule in each formula unit. The listing of the
main geometric parameters for 7 appears in Table 5. The
structure can be considered as formed by two fused rings
that share a platinum atom. The four-membered PtS2C ring,
which includes the chelating [SCH2S]2- ligand, is essentially
planar, deviations from planarity being less than 0.03 Å. The
C3P2Pt ring includes six atoms and shows a chair conforma-
tion. The platinum atom has square planar coordination,
distorted by a significant reduction of the S-Pt-S angle
(76.8°) from ideal 90°, and by a twist of 5.0° between the
PtS2 and PtP2 planes. The bite angle of the diphosphine
ligand, 92.1°, dictates the values of the remaining P-Pt-S
angles about the platinum atom. The structure of 8, estab-
lished qualitatively from a crystal of inferior quality, is
similar in its major aspects, having one fewer C atom in the
chelate ring.
Complexes of general formula [L2Pt(S2CH2)] with similar
structure to 7 and 8 amount to only two examples, [Pt(PMe2-
Ph)2(S2CH2)]10 and [Pt(dppy)2(S2CH2)],11 both with uniden-
tate phosphine ligands. Comparison of these complexes
shows remarkable similarities, and particularly, the geometric
features of their PtS2C rings are practically identical (Table
6). Obviously, the structures differ in the P-Pt-P angles,
which range from 92.2° to 100.6° (leaving out the smaller
angle in 8), but these differences have no apparent effect on
the structural parameters involving the neighboring PtS2C
ring. Concerning the Pt(P∩P) moieties, their geometric
features are in good concordance with those observed in 1
and 2, respectively, as well as in [Pt(dppp)Cl2] and [Pt(dppe)-
Cl2] complexes known13,25 and related species.30
S(1)-Pt(1)-S(2)
P(1)-Pt(1)-P(2)
Pt(1)-S(1)-Pt(2)
82.80(5)
94.77(5)
87.40(4)
S(1)-Pt(2)-S(2)
P(3)-Pt(2)-P(4)
Pt(1)-S(2)-Pt(2)
83.24(5)
94.59(5)
87.52(4)
Complex 7
Pt(1)-S(1)
Pt(1)-P(1)
S(1)-C(30)
2.3214(8)
2.2596(8)
1.840(4)
Pt(1)-S(2)
Pt(1)-P(2)
S(2)-C(30)
2.3281(8)
2.2558(8)
1.842(4)
S(1)-Pt(1)-S(2)
Pt(1)-S(1)-C(30)
S(1)-C(30)-S(2)
76.85(3)
89.96(12)
103.36(17)
P(1)-Pt(1)-P(2)
Pt(1)-S(2)-C(30)
92.18(3)
89.70(11)
Complex 11
Pt(1)-S(1)
Pt(1)-S(2)
Pt(1)-P(1)
Pt(1)-P(2)
S(1)-C(1)
S(3)-C(1)
2.3693(14)
2.3791(14)
2.2697(16)
2.2710(15)
1.843(6)
Pt(2)-S(1)
Pt(2)-S(2)
Pt(2)-P(3)
Pt(2)-P(4)
S(2)-C(2)
S(3)-C(2)
2.3688(14)
2.3850(14)
2.2738(15)
2.2702(14)
1.854(6)
1.797(7)
1.783(6)
S(1)-Pt(1)-S(2)
P(1)-Pt(1)-P(2)
Pt(1)-S(1)-Pt(2)
Pt(1)-S(1)-C(1)
Pt(1)-S(2)-C(2)
S(1)-C(1)-S(3)
C(1)-S(3)-C(2)
82.56(5)
90.44(6)
86.94(5)
102.0(2)
101.4(2)
117.9(3)
102.0(3)
S(1)-Pt(2)-S(2)
P(3)-Pt(2)-P(4)
Pt(1)-S(2)-Pt(2)
Pt(2)-S(1)-C(1)
Pt(2)-S(2)-C(2)
S(2)-C(2)-S(3)
82.45(5)
92.39(5)
86.35(5)
106.2(2)
106.6(2)
117.2(3)
found in dppe analogue 2.5 Considering the average values
of the angles about the Pt atoms, the more important
deviations from the ideal value correspond to P-Pt-P
(94.6°) and S-Pt-S (83.0°).
The very few structurally characterized examples with a
similar core to that of 1 are the [Pt2(dppy)2(µ-S)2] (dppy )
2-diphenylphosphinopyridine)11 and [Pt2(dppe)2µ-S)2] (2)5
complexes and the incompletely determined X-ray structure
of [Pt2(PMe2Ph)4(µ-S)2].1 Comparison of their main geo-
metric parameters (Table 6) indicates that the most significant
difference lies in the dihedral angle between the two PtS2
planes and that a decrease in this angle entails a concomitant
shortening of the Pt‚‚‚Pt and smaller changes in the S‚‚‚S
distances.
The structure of 11 is totally unprecedented (Figure 5) and
consists of dinuclear [(dppp)Pt(µ-SCH2SCH2S)Pt(dppp)]2+
cations and Cl- counterions, together with toluene solvent
molecules. Selected bond angles and distances are given in
Table 5. The cation has approximate mirror symmetry. It
can be described as formed by a {(dppp)Pt(µ-S)2Pt(dppp)}
core capped by a CH2SCH2 fragment, which lowers the
approximate core symmetry from C2V to Cs. The core shows
a hinged Pt2S2 central ring with the two platinum atoms
bridged by two thiolate sulfurs, coordination being completed
Complexes 7 and 8 are structurally related as they both
consist of mononuclear [Pt(P∩P)(S2CH2)] (P∩P ) dppp (7)
(Figure 4) or dppe (8) discrete molecules devoid of crystal-
lographic symmetry elements. In the case of 7, there is one
Inorganic Chemistry, Vol. 41, No. 12, 2002 3227

Mas-Balleste´ et al.
Table 6. Main Geometric Parametersaof the {Pt2S2} and {PtS2C} Fragments in Structurally Characterized Complexes
complex
Pt-S
Pt-P
C-S
S-C-S
Pt‚‚‚Pt
S‚‚‚S
Pt-S-Pt
S-Pt-S
θb
P-Pt-P
ref
[Pt2(dppy)4(µ-S)2]
2.33
2.35
2.34
2.34
2.31
2.30
2.32
2.32
2.28
2.24
2.25
2.26
2.27
2.25
2.26
2.27
3.55
3.29
3.23
3.17
3.01
3.13
3.10
99.6
88.9
87.5
85.5
80.4
83.7
83.0
81.6
76.2
76.1
76.9
76.2
180
102.9
86.2
94.7
11
5
c
[Pt2(dppe)2(µ-S)2] (2)
[Pt2(dppp)2(µ-S)2] (1)
[Pt2(PMe2Ph)4(µ-S)2]d
[Pt(dppy)2(S2CH2)]
[Pt(PMe2Ph)2(S2CH2)]
[Pt(dppp)(S2CH2)] (7)
[Pt(dppe)(S2CH2)] (8)d
140.2
134.8
121
1
1.82
1.83
1.84
1.84
103.0
102.1
103.4
102.0
100.6
94.3
92.2
85.4
11
10
c
c
a Distances in angstroms; angles in degrees. b Dihedral angle between the two PtS2 planes. c This work. d Only preliminary crystallographic data.
complexes of general formula [Rh2(COD)2{µ-(S-S)}], where
S-S ) S(CH2)nS with n ) 2, 3;28 and a Pt3 trinuclear
complex with two bridging S2N2CPh ligands.32
The [SCH2SCH2S]2- ligand in complex 11 resembles
closely the [SCH2CH2CH2S]2- ligand in the previously
reported Pd-Rh complex,27 with the obvious differences in
bond lengths (S-C longer than C-C) and angles (C-S-C
smaller than C-C-C) produced when the central CH2 is
replaced by S.
Concluding Remarks
A detailed study of the reaction of [(P∩P)Pt(µ-S)2Pt(P∩P)],
P∩P ) dppp or dppe, with CH2Cl2 confirms the high
nucleophilicity of the sulfide ligand in the {Pt2S2} core. The
experimental results have allowed us to formulate all the
steps involved from the initial to the final products. In
addition, they show that the nucleophilic behavior is highly
dependent on the diphosphine nature. Thus, the [Pt(dppp)-
(S2CH2)] complex reacts further with CH2Cl2 and itself to
form [Pt2(dppp)2{µ-(SCH2SCH2S)-S,S′}]Cl2 while the dppe
analogue does not. Theoretical calculations are consistent
with the experimental results showing that complexes with
dppp are more nucleophilic than the parent dppe compounds.
This enhanced nucleophilicity can be due to a more efficient
electron donation from the phosphorus lone pairs of dppp,
compared to those from dppe, and it is reasonable to attribute
it to the closeness of the bite angle of the dppp ligand to the
P-Pt-P angle found in complexes with unidentate uncon-
strained phosphines. The bite angle also influences the kinetic
stability of the different species formed along the reaction.
The dppp ligand appears to be more flexible than dppe, and
thus, it can better accommodate to the changes in the bite
angle required along the reaction pathway. As a consequence,
the evolution from [(P∩P)Pt(µ-S)2Pt(P∩P)] to [Pt(P∩P)-
(S2CH2)] and [Pt[(P∩P)Cl2] proceeds faster for dppe than
for dppp containing complexes. Overall, the observed
dependence on the nature of the ligands bound to the {Pt2S2}
core, together with the high number and different nature of
the species characterized in this work, gives a reason for
the diversity of the compounds reported in the literature as
a result of the reaction of [L2Pt(µ-S)2PtL2] with weak
electrophilic agents.
Figure 5. Structure of the cation of complex 11 with key atoms labeled
and with 50% probability ellipsoids. H atoms, chloride anions, phenyl rings,
and toluene solvent molecules are omitted.
by chelating dppp ligands. The dihedral angle between PtS2
planes, θ ) 131.7°, is smaller than that found in the parent
[(dppp)Pt(µ-S)2Pt(dppp)] complex 1 (θ ) 134.8°), this
reduction being less significant than that experienced by the
dppe analogue 2 when acting as a metalloligand.6 The
geometries at the individual Pt sites are essentially square
planar, the main distortions being due to the reduction of
the S-Pt-S angles from ideal 90° (average 82.5°), and by
a twist of 3.6° between the Pt(1)S2 and Pt(1)P2 planes and
of 1.3° between Pt(2)S2 and Pt(2)P2. The bite angle of the
diphosphine ligand involving Pt(1) (90.4°) and Pt(2) (92.4°)
compares well with those found in the parent complex (1).
The capping CH2SCH2 unit can be considered within the
bridging [SCH2SCH2S]2- ligand, which, according to the
angles about S(1) [Pt(1)-S(1)-C(1) 102.0°; Pt(1)-S(2)-
C(2) 101.4°] and S(2) [Pt(2)-S(1)-C(1) 106.2°; Pt(2)-
S(2)-C(2) 106.6°], is slightly tilted toward Pt(1) while the
thioether S(3) atom is clearly oriented toward Pt(2), the
C(1)-S(3)-C(2) angle being 102.0°.
The main novelty of this complex is that no other structure
containing the (SCH2SCH2S)2- species either as a terminal
or bridging ligand has ever been reported. Also, to our
knowledge, no dinuclear homometallic platinum complexes
with S∩S bridging units have been characterized crystallo-
graphically. The closest examples found in the literature are
the heterobimetallic bridged dithiolate platinum-rhodium
complexes of general formula [(P-P)Pt{µ-(S-S)}Rh-
(COD)], where P-P ) (PPh3)2 and S-S ) S(CH2)nS with
n ) 2, 3, or 4; P-P ) dppp and S-S ) S(CH2)4S; P-P )
1,4-bis(diphenylphosphino)butane and S-S ) S(CH2)4S;27
the homobimetallic bridged dithiolate rhodium-rhodium
Acknowledgment. Financial support from the Ministerio
de Ciencia y Tecnolog´ıa of Spain (DGICYT: BQU2001-
(32) Banister, A. J.; Gorrell, I. B.; Lawrence, S. E.; Lehmann, C. W.; May,
I.; Tate, Cr.; Blake, A. J.; Rawson, J. M. Chem. Commun. 1994, 1779.
3228 Inorganic Chemistry, Vol. 41, No. 12, 2002

[{Ph2P(CH2)nPPh2}Pt(µ-S)2Pt{Ph2P(CH2)nPPh2}]
Supporting Information Available: Crystallographic files in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
1976 and PB98-0916-CO2-01) and from EPSRC (U.K.) is
gratefully acknowledged. C.M. thanks the EU and CESCA/
CEPBA for sponsoring her visit to the UAB under the
Improving Human Potential Program, Access to Large Scale
Facilities (HPRI-1999-CT-00071).
IC0107173
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