Moderating the nucleophilicity of the sulfide ligands in the dinuclear {Pt2S2} metalloligand system using triphenylarsine

Article abstract of DOI:10.1016/j.jorganchem.2006.02.020

Reaction of cis-[PtCl₂(AsPh₃)₂] with excess sodium sulfide in benzene gave the triphenylarsine analogue of the well-known metalloligand [Pt₂(μ-S)₂(PPh₃)₄] as an orange solid.The compound was characterised by detailed mass spectrometry studies, and by conversion to various alkylated and metallated derivatives.The sulfide ligands in [Pt₂(μ-S)₂(AsPh₃)₄] are less basic than the triphenylphosphine analogue, and the complex gives a relatively weak [M+H]⁺ ion in the positive-ion electrospray (ESI) mass spectrum, compared with the phosphine analogue.Methylation of an equimolar mixture of [Pt₂(μ-S)₂(PPh₃)₄] and [Pt₂(μ-S)₂(AsPh₃)₄] with MeI gave the species [Pt₂(μ-S)(μ-SMe)(AsPh₃)₄]⁺ and [Pt₂(μ-SMe)₂(PPh₃)₃I]⁺, indicating a reduced tendency for the sulfide of [Pt₂(μ-S)(μ-SMe)(AsPh₃)₄]⁺ to undergo alkylation.The lability of the arsine ligands is confirmed by the reaction of an equimolar mixture of [Pt₂(μ-S)₂(PPh₃)₄] and [Pt₂(μ-S)₂(AsPh₃)₄] with n-butyl chloride, giving [Pt₂(μ-S)(μ-SBu)(EPh₃)₄]⁺ (E = P, As), which with Me₂SO₄ gave a mixture of [Pt₂(μ-SMe)(μ-SBu)(PPh₃)₄]²⁺ and [Pt₂(μ-SMe)(μ-SBu)(AsPh₃)₃Cl]⁺.Reactivity towards 1,2-dichloroethane follows a similar pattern.The formation and ESI MS detection of mixed phosphine-arsine {Pt₂S₂} species of the type[Pt₂(μ-S)₂(AsPh₃)_n(PPh₃)_4-n] is also discussed. Coordination chemistry of [Pt₂(μ-S)₂(AsPh₃)₄] towards a range of metal-chloride substrates, forming sulfide-bridged trinuclear aggregates, has also been probed using ESI MS, and found to be similar to the phosphine analogue. The X-ray crystal structure of [Pt₂(μ-S)₂(AsPh₃)₄Pt(cod)](PF₆)₂ (cod = 1,5-cyclo-octadiene) has been determined for comparison with the (previously reported) triphenylphosphine analogue. ESI MS is a powerful tool in exploring the chemistry of this system; in some cases the derivatising agent p-bromobenzyl bromide is used to convert sparingly soluble and/or poorly ionising {Pt₂S₂} species into soluble, charged derivatives for MS analysis.

Full text of DOI:10.1016/j.jorganchem.2006.02.020

Journal of Organometallic Chemistry 691 (2006) 2827–2838
www.elsevier.com/locate/jorganchem
Moderating the nucleophilicity of the sulfide ligands in the
dinuclear {Pt2S2} metalloligand system using triphenylarsine
a
a,
a
,b
*
Sunita Jeram , William Henderson *, Brian K. Nicholson , T.S. Andy Hor
a
Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
b
Received 14 June 2005; received in revised form 9 February 2006; accepted 9 February 2006
Available online 6 March 2006
Abstract
Reaction of cis-[PtCl2(AsPh3)2] with excess sodium sulfide in benzene gave the triphenylarsine analogue of the well-known metallo-
ligand [Pt2(l-S)2(PPh3)4] as an orange solid. The compound was characterised by detailed mass spectrometry studies, and by conversion
to various alkylated and metallated derivatives. The sulfide ligands in [Pt2(l-S)2(AsPh3)4] are less basic than the triphenylphosphine ana-
logue, and the complex gives a relatively weak [M+H]+ ion in the positive-ion electrospray (ESI) mass spectrum, compared with the
phosphine analogue. Methylation of an equimolar mixture of [Pt2(l-S)2(PPh3)4] and [Pt2(l-S)2(AsPh3)4] with MeI gave the species
[Pt2(l-S)(l-SMe)(AsPh3)4]+ and [Pt2(l-SMe)2(PPh3)3I]+, indicating a reduced tendency for the sulfide of [Pt2(l-S)(l-SMe)(AsPh3)4]+
to undergo alkylation. The lability of the arsine ligands is confirmed by the reaction of an equimolar mixture of [Pt2(l-S)2(PPh3)4]
and [Pt2(l-S)2(AsPh3)4] with n-butyl chloride, giving [Pt2(l-S)(l-SBu)(EPh3)4]+ (E = P, As), which with Me2SO4 gave a mixture of
[Pt2(l-SMe)(l-SBu)(PPh3)4]2+ and [Pt2(l-SMe)(l-SBu)(AsPh3)3Cl]+. Reactivity towards 1,2-dichloroethane follows a similar pat-
tern.The formation and ESI MS detection of mixed phosphine–arsine {Pt2S2} species of the type [Pt2(l-S)2(AsPh3)n(PPh3)4ꢀn] is also
discussed. Coordination chemistry of [Pt2(l-S)2(AsPh3)4] towards a range of metal-chloride substrates, forming sulfide-bridged trinu-
clear aggregates, has also been probed using ESI MS, and found to be similar to the phosphine analogue. The X-ray crystal structure
of [Pt2(l-S)2(AsPh3)4Pt(cod)](PF6)2 (cod = 1,5-cyclo-octadiene) has been determined for comparison with the (previously reported) tri-
phenylphosphine analogue. ESI MS is a powerful tool in exploring the chemistry of this system; in some cases the derivatising agent
p-bromobenzyl bromide is used to convert sparingly soluble and/or poorly ionising {Pt2S2} species into soluble, charged derivatives
for MS analysis.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Arsine ligands; Sulfide ligands; Platinum complexes; Electrospray mass spectrometry
1. Introduction
most widely studied complex of this type is the triphenyl-
phosphine derivative [Pt2(l-S)2(PPh3)4] (1), probably
because of its accessibility from air-stable starting materi-
als, and its tendency to produce crystalline derivatives.
However, recent studies have shown that the chemistry of
the {Pt2S2} core can be modified by changing the ancillary
phosphine ligands from PPh3 to a diphosphine such as
Ph2P(CH2)nPPh2 (n = 2,3) [4,5]. Other studies have
focused on derivatives containing phosphines such as
PhPMe2 [6,7] and P(C6H4Me)3 [8] (which provide greater
solubility in organic solvents), chiral phosphines such as
DIOP (to investigate the applicability of {Pt2S2} complexes
Complexes containing the {Pt2S2} core have a rich and
diverse chemistry. The sulfide ligands are highly nucleo-
philic, and can undergo protonation and alkylation, as well
as acting as donor ligands towards a range of main group,
transition metal and actinide centres. The chemistry of this
system has been the subject of several reviews [1–3]. The
*
Corresponding authors. Tel.: +64 7 856 2889; fax: +64 7 838 4219.
E-mail address: w.henderson@waikato.ac.nz (W. Henderson).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.02.020

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S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
in enantioselective reactions) [9], redox active 1,10-bis(diph-
enylphosphino)ferrocene (dppf) [10] and the pyridyl phos-
phine Ph2Ppy [11] (which can be used to assemble large
multimetallic sulfide aggregates) [12].
2. Results and discussion
2.1. Synthesis and initial characterisation of [Pt2(l-S)2-
(AsPh3)4]
The reaction of cis-[PtCl2(AsPh3)2] with solid sodium
sulfide hydrate, using analogous conditions used to prepare
[Pt2(l-S)2(PPh3)4], gave a bright orange suspension, from
which the arsine analogue [Pt2(l-S)2(AsPh3)4] (2) was iso-
lated as an orange solid by filtration, followed by washing
with benzene and water. The yield of product was typically
rather low (ca. 20%), and the reaction filtrate was an
orange-brown colour, indicating that significant material
remained in solution. An ESI mass spectrum of the reac-
tion filtrate showed a major unidentified platinum-contain-
ing species at m/z 1963, together with ions assigned as
[Ph3AsO+Na]+ (m/z 345), [Ph3AsO+K]+ (m/z 361) and
[2Ph3AsO+Na]+ (m/z 667); no ions were observed in nega-
tive-ion mode.
The reaction appears to proceed more slowly than the
analogous synthesis of [Pt2(l-S)2(PPh3)4]; an improved
yield and higher purity product (as evidenced by micro-
analysis) was obtained when the reaction time was
increased from 24 to 48 h. However, the product could
not be obtained analytically pure; analysis of three inde-
pendently prepared samples all showed low carbon and
hydrogen percentages. SEM-EDAX analysis of samples
prepared with 24 and 48 h reaction times showed similar
heavy element compositions, but the shorter reaction time
sample showed greater traces of sodium and chlorine.
Suspecting that the lability of triphenylarsine was the
key cause of the low yield in the synthesis, addition of free
AsPh3 ligand to the reaction mixture gave a nominally
improved yield (62%) of [Pt2(l-S)2(AsPh3)4] after a 48 h
reaction period, though the elemental microanalytical data
for this material still showed an impure material with low
carbon and hydrogen percentages. It is noteworthy that
the recent synthesis of the analogous bidentate-arsine com-
plex [Pt2(l-S)2(Ph2AsCH2CH2AsPh2)2] was not plagued by
such problems, and a good yield of 80% was obtained for
this complex, which could be recrystallised from benzene
[13]. In contrast, complex 2 appeared to be essentially
insoluble in benzene.
S
Ph3E
Ph3E
EPh3
EPh3
Pt
Pt
S
1, E = P
2, E = As
In contrast to the abundance of studies that use ancillary
phosphine ligands on the {Pt2S2} core, systems with other
ancillary ligands are scarcely known. In very early work,
Chatt and Mingos attempted the preparation of derivatives
containing thioether ligands (SEt2 or EtSC2H4SEt) but
obtained brown, insoluble polymeric products that ana-
lysed as [Pt4S3(SEt2)3]n and [Pt2S2(EtSC2H4SEt)]n [7].
Arsine ligands attracted our attention, because of their
overall similarity, but generally poorer ligand properties,
when compared to the corresponding phosphines. During
´
the course of this work, Gonzalez-Duarte and co-workers
reported a detailed study on the synthesis of the arsine
complex [Pt2(l-S)2(Ph2AsCH2CH2AsPh2)2], including an
X-ray structure on the parent complex, and the synthesis
and characterisation of a number of trinuclear sulfide-
bridged aggregates containing {Pt2MS2} cores (M = Pt,
Cu, Zn, Cd, Hg) [13]. In this work, it was found, from
X-ray crystallographic and electrochemical studies that
the more weakly electron-donating and lower trans-influ-
ence [14] arsine ligand moderates the basicity of the sulfides
of the {Pt2S2} core.
Some other arsine-containing platinum-sulfide species
are also known; trinuclear sulfido derivatives [Pt3(l-
S)2(PMe2Ph)4(AsMe2Ph)2]2+ were reported in early work
by Chatt and Mingos, by reaction of [Pt2(l-S)2(PMe2Ph)4]
with cis-[PtCl2(AsMe2Ph)2] [7] and compounds containing
dinuclear thiolate-bridged cores {Pt2(l-SMe)2} with ancil-
lary AsMe3 ligands have been prepared [15].
Our recent methodology, employing electrospray ionisa-
tion mass spectrometry (ESI MS) as a powerful tool for
monitoring reaction chemistry of {Pt2S2} systems [2,16–
18] is ideal for studying the chemistry of Ph3As derivatives.
Here NMR spectroscopy will be of little use compared to
the related triphenylphosphine system, or the system con-
taining Ph2As(CH2)nAsPh2 ligands, where the CH2 reso-
nances are readily accessible, and permit reaction
monitoring [13]. In this paper, we describe the synthesis
of the triphenylarsine analogue [Pt2(l-S)2(AsPh3)4],
together with a preliminary investigation into its properties
in comparison with the phosphine analogue [Pt2(l-
S)2(PPh3)4], using ESI MS to further define the characteris-
tics of the arsine-substituted {Pt2S2} core.
The [Pt2(l-S)2(AsPh3)4] was analysed by detailed mass
spectrometry studies described hereafter, and subsequently
converted to alkylated and metal complex derivatives
which have been characterised by NMR spectroscopy, ele-
mental analysis and in one case by an X-ray crystal struc-
ture determination.
2.2. Protonation and alkylation reactions of
[Pt2(l-S)2(AsPh3)4]
[Pt2(l-S)2(AsPh3)4] qualitatively shows a lower solubility
in methanol compared to [Pt2(l-S)2(PPh3)4]. Thus, when a
small quantity of [Pt2(l-S)2(PPh3)4] is added to methanol, a
clear pale yellow solution is obtained; such solutions have

S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
2829
been found by ESI MS to yield the [M+H]+ ion [18], and
this species is much more soluble than neutral [Pt2(l-
S)2(PPh3)4] in methanol. However, for [Pt2(l-S)2(AsPh3)4]
little dissolution appears to take place and the complex
gives a weak [M+H]+ ion at m/z 1679 in the positive-ion
ESI mass spectrum. The mass spectrum of a dilute equimo-
lar mixture of [Pt2(l-S)2(AsPh3)4] and [Pt2(l-S)2(PPh3)4] in
methanol is thus dominated by the protonated ion of the
phosphine complex, with some undissolved solid (presum-
ably the arsine complex) remaining. The phosphine com-
plex is expected to have a greater basicity than the arsine
complex, as a result of the better electron-donating proper-
ties of the phosphines, which makes the sulfide ligands
more electron-rich [13]. This will effect a higher degree of
protonation, producing a more soluble [M+H]+ complex
and concomitantly a more intense signal thereof in the
ESI mass spectrum. These observations are in accord with
results from alkylation studies discussed hereafter, as well
as results from the Ph2AsCH2CH2AsPh2–{Pt2S2} system
[13].
expected [M]+ ion in the positive-ion ESI mass spectrum
at a cone voltage of 20 V, and successive loss of two AsPh3
ligands as the cone voltage is raised to 70 V. The 1H NMR
spectrum of the arsine complex 3b showed the CH2 protons
as a single resonance at d 3.99; three-bond coupling to 195Pt
effected broadening of the peak baseline, but could not be
resolved. By comparison, the analogous phosphine com-
plex showed a CH2 resonance at d 3.70. These chemical
shifts are consistent with reduced electron density at the
sulfur centres in the arsine system.
S
S
+
Ph3As
Ph3As
AsPh3
AsPh3
Pt
Pt
Alkylation reactions of [Pt2(l-S)2(AsPh3)4] have also
been studied in order to provide comparative data with
[Pt2(l-S)2(PPh3)4], which is known to undergo both mono-
and dialkylation reactions, depending on the nature of the
alkylating agent. We have recently carried out an extensive
mass spectrometry-based survey of alkylation reactions of
[Pt2(l-S)2(PPh3)4] [19], which provide a benchmark for
the present study. Several alkylation systems have been
studied using ESI MS, in order to build up a picture of
reactivity of the arsine complex.
The reaction with an excess of a simple alkylating agent,
benzyl chloride, was initially studied. This reagent was cho-
sen because benzyl halides give selective and rapid mono-
alkylation with [Pt2(l-S)2(PPh3)4], as reported previously
[7,19,20]. By using an equimolar mixture of [Pt2(l-S)2-
(PPh3)4] and [Pt2(l-S)2(AsPh3)4], information on the purity
of the latter can be obtained, together with the relative rates
of product formation. Although the starting [Pt2(l-
S)2(AsPh3)4] gives only a weak ion in the ESI mass spectrum,
the product species [Pt2(l-S)(l-SCH2Ph)(EPh3)4]+ (E = P,
As) are cationic and would be expected to have high ionisa-
tion efficiencies. The mono-benzylated derivatives [Pt2-
(l-S)(l-SCH2Ph)(PPh3)4]+ (m/z 1593) and [Pt2(l-S)(l-
SCH2Ph)(AsPh3)4]+ (m/z 1770) are formed at approximately
the same rate, and at the conclusion of the reaction, the
[M+H]+ ion of [Pt2(l-S)2(PPh3)4] had disappeared, giving
the two benzylated products in equal proportions. Similar
results were observed in the analogous reaction with excess
butyl chloride (refer Fig. 2a). These observations indicate
that the [Pt2(l-S)2(AsPh3)4], which does not give a satisfac-
tory elemental microanalysis, is of sufficient purity to enable
further comparative studies by MS.
R
3a, R = Br
3b, R = H
In an experiment to investigate possible exchange reac-
tions between alkylated phosphine and arsine systems, an
equimolar solution of [Pt2(l-S)(l-SCH2C6H4Br)(AsPh3)4]+
and [Pt2(l-S)(l-SCH2Ph)(PPh3)4]+ in dichloromethane was
analysed by ESI MS. The expected parent ions were
observed, but on allowing the solution to stand for several
days, there was a gradual loss in intensity of the [Pt2(l-
S)(l-SCH2C6H4Br)(AsPh3)4]+ ion (which disappeared after
1 week), and formation of a low intensity, unidentified ion
at m/z 2307. These observations again suggest different
behaviour for the arsine system, where even a monoalky-
lated derivative appears to be unstable in dichloromethane.
Attempts at growing crystals of the parent alkylated deriv-
ative or decomposition product(s) suitable for an X-ray
crystallographic study were unsuccessful.
In order to access dialkylation and subsequent reactions,
an equimolar mixture of [Pt2(l-S)2(AsPh3)4] and [Pt2(l-
S)2(PPh3)4] was reacted with excess MeI. Spectra recorded
after reaction times of 15 min and 2.5 h are shown in Fig. 1.
Rapid monomethylation of both complexes occurs, giving
the monocationic derivatives [Pt2(l-S)(l-SMe)(EPh3)4]+
(E = P, m/z 1518; E = As, m/z 1694), Fig. 1a. Upon further
reaction, the pathways for the two complexes diverge. With
[Pt2(l-S)2(PPh3)4], as we have described previously [19],
monomethylation is followed by dimethylation, with the
resulting [Pt2(l-SMe)2(PPh3)4]2+ cation being subject to
nucleophilic attack by the generated iodide, giving [Pt2(l-
SMe)2(PPh3)3I]+ (m/z 1397) as the major phosphine species
after 2.5 h, Fig. 1b. In contrast, however, the arsine com-
plex remains predominantly as the monomethylated deriv-
ative, indicating a significantly lower tendency to undergo
Reaction of [Pt2(l-S)2(AsPh3)4] with excess 4-bromo-
benzyl bromide or benzyl bromide in methanol on the mac-
roscopic scale gave [Pt2(l-S)(l-SCH2C6H4Br)(AsPh3)4]+ 3a
and [Pt2(l-S)(l-SCH2C6H5)(AsPh3)4]+ 3b, isolated as their
PFꢀ6 salts as yellow solids. The complexes show the

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S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
Fig. 1. Positive-ion ESI mass spectra comparing the reactivity of [Pt2(l-S)2(PPh3)4] and [Pt2(l-S)2(AsPh3)4] with MeI in methanol solution (cone voltage
20 V), (a) recorded after 15 min and (b) after ca. 2.5 h.
the second methylation step. After standing the reaction
mixture for 24 h, the major peak in the spectrum was due
to [Pt2(l-SMe)2(PPh3)3I]+, with small amounts of other
unidentified species at m/z 1442 and 1478; no arsine species
were positively identified. This again appears to indicate
that alkylated triphenylarsine {Pt2S2} derivatives are
unstable compared to their phosphine counterparts.
explored [19,21], and gives the dialkylated product [Pt2(l-
SCH2CH2S)(PPh3)4]2+. The relative reactivities of [Pt2(l-
S)2(AsPh3)4] and [Pt2(l-S)2(PPh3)4] were again explored by
means of ESI MS of an equimolar mixture. Spectra recorded
after 40 and 90 min are shown in Fig. 3, and demonstrate the
differing reactivities of the two complexes. After 40 min, the
arsine complex has formed predominantly monoalkylated
[Pt2(l-S)(l-SCH2CH2Cl)(AsPh3)4]+ (m/z 1742), while the
phosphine complex formed the expected [Pt2(l-SCH2CH2S)-
(PPh3)4]2+ (m/z 765). Only a trace of the arsine analogue
[Pt2(l-SCH2CH2S)(AsPh3)4]2+ (m/z 853.5) is seen, confirm-
ing the lesser reactivity of the arsine complex. Furthermore,
an ion at m/z 1436 is assigned as the arsine-displaced species
[Pt2(l-SCH2CH2S)(AsPh3)3Cl]+, formed by dissociation of
a more weakly bound arsine ligand and replacement by
chloride. On standing the reaction mixture further (spec-
trum b), the total intensity of ions from the arsine system
has decreased, especially for [Pt2(l-S)(l-SCH2CH2Cl)-
(AsPh3)4]+, presumably again due to dialkylation and the
subsequent instability of arsine-containing products in the
presence of chlorinated solvents.
To investigate the dialkylation step as an isolated pro-
cess, it was necessary to avoid the presence of good nucleo-
philes, which attack the dications [Pt2(l-SR)2(EPh3)4]2+
.
Therefore, an equimolar mixture of [Pt2(l-S)2(AsPh3)4]
and [Pt2(l-S)2(PPh3)4] was reacted with excess n-butyl chlo-
ride, giving [Pt2(l-S)(l-SBu)(EPh3)4]+ (E = P, m/z 1560;
E = As, m/z 1737) as their chloride salts. The positive-ion
ESI mass spectrum, Fig. 2(a) shows predominantly the
two ions in equal intensities. Upon addition of dimethyl sul-
fate (a potent methylating agent which does not furnish a
good nucleophilic anion), the ESI mass spectrum after 1 h,
Fig. 2(b), showed two main species, [Pt2(l-SMe)(l-SBu)-
(PPh3)4]2+ (m/z 787.5), and [Pt2(l-SMe)(l-SBu)(AsPh3)3-
Cl]+ (m/z 1480). In the phosphine case, simple methylation
of the second sulfur occurs, with formation of a stable dica-
tion, as we have reported previously [19]. However, the
arsine ligand is more labile, and can be displaced by the chlo-
ride ion. Palladium(II) analogues also represent labile sys-
tems that show loss of even a coordinated phosphine
ligand, for example reaction of [Pt2(l-S)2(PPh3)4] with
[PdCl2(PPh3)2] gives [Pt2(l-S)2(PPh3)4PdCl(PPh3)]+ [17].
Alternatively, the rate of dialkylation can be explored
using the reaction with ClCH2CH2Cl. The reactivity of
[Pt2(l-S)2(PPh3)4] towards this reagent has been previously
The results of the investigations into the alkylation
chemistry of [Pt2(l-S)2(AsPh3)4] with three different alkyl-
ating systems (MeI, BuCl + Me2SO4, ClCH2CH2Cl) are
in overall agreement. The second alkylation step is consid-
erably slower for the arsine system, and the resulting dica-
tion is prone to displacement of an arsine ligand by even a
weak nucleophilic anion (generated from the alkylating
agent), such as chloride.
Overall, the initial data from ESI MS monitored alkyl-
ation of [Pt2(l-S)2(AsPh3)4] confirm the conclusions of

S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
2831
Fig. 2. Successive alkylation of an equimolar mixture of [Pt2(l-S)2(PPh3)4] and [Pt2(l-S)2(AsPh3)4] in methanol; positive-ion ESI mass spectra recorded at
a cone voltage of 20 V; (a) with excess n-butyl chloride after 1 week, showing formation of the monobutyl derivatives [Pt2(l-S)(l-SBu)(EPh3)4]+ and (b) 1 h
after subsequent addition of excess dimethyl sulfate. The spectra clearly show the different reaction pathways for the phosphine and arsine systems.
Fig. 3. Parallel reaction of equimolar quantities of [Pt2(l-S)2(PPh3)4] and [Pt2(l-S)2(AsPh3)4] with excess ClCH2CH2Cl in methanol: (a) after ca. 40 min
and (b) after ca. 90 min, showing the divergent reactions of the two complexes.

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S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
´
Gonzalez-Duarte and co-workers that the {As4Pt2S2} sys-
tem contains less reactive sulfide groups compared to phos-
phine analogues [13].
impurity material present in the [Pt2(l-S)2(AsPh3)4]. The
complexes were isolated as their hexafluorophosphate salts
by addition of excess NH4PF6 to the filtered reaction
solutions.
2.3. Formation of trinuclear metal complexes from
[Pt2(l-S)2(AsPh3)4]
2+
Ph3As
S
We wished to extend the comparison of triphenylphos-
phine and triphenylarsine {Pt2S2} systems to the formation
Ph3As
Ph3As
Pt
Pt
Pt
-
2PF6
´
of metal derivatives. In their study, Gonzalez-Duarte et al.
prepared a number of trinuclear adducts containing
{Pt2MS2} cores, and by means of X-ray structure determi-
nations showed that the M–S bond distances were longer
than in the corresponding phosphine analogues, indicating
that the {As4Pt2S2} system has reduced coordinating abil-
ity [13]. [Pt2(l-S)2(PPh3)4] is known to form adducts with
a diverse range of metal substrates, including examples
from main group, transition and actinide metals [1–3,16–
18].
Reactions of [Pt2(l-S)2(AsPh3)4] with a range of metal–
halide complexes were carried out, using ESI MS to screen
products of reaction, following the methodology that we
have previously developed [16–18]. A summary of the
major observed ions is given in Table 1. In these examples,
the cationic metal fragment formed by halide loss is coor-
dinated to the {Pt2S2} moiety, giving mono- or di-cationic
product species. In all cases, excellent agreement was
observed between experimental and calculated isotope dis-
tribution patterns, with the dications showing the expected
0.5 m/z separation of adjacent peaks. The species observed
correlate very closely with those previously reported for the
corresponding [Pt2(l-S)2(PPh3)4] systems [16–18]. As an
illustrative example, reaction with [RhCl2Cp*]2 (Cp* =
g5-C5Me5) gave exclusively the adduct [Pt2(l-S)2(AsPh3)4-
RhCp*]2+ as illustrated in Fig. 4.
S
Ph3As
4
2+
Ph3As
S
N
N
Ph3As
Ph3As
Pt
Pt
-
Pd
2PF6
S
Ph3As
5
A positive-ion ESI mass spectral study on the palladium
complex was carried out, and show ions highly dependent
on the cone voltage. At a low cone voltage (5 V), the parent
dication [Pt2(l-S)2(AsPh3)4Pd(bipy)]2+ (m/z 970) dominates
the spectrum, while at 80 V, the ion pair [Pt2(l-S)2(AsPh3)4-
Pd(bipy)+PF6]+ (m/z 2086) was the base peak. It is note-
worthy that ion pair formation allows the complex cation
to remain intact at elevated cone voltages; other derivatives
such as the alkylated complexes [Pt2(l-S)(l-SR)(AsPh3)4]+
(R = nBu, CH2Ph) undergo loss of AsPh3 at these higher
cone voltages. The platinum–cod complex also shows a
dominant [Pt2(l-S)2(AsPh3)4Pt(cod)]2+ ion at m/z 991,
together with a minor ion-pair [Pt2(l-S)2(AsPh3)4Pt(cod)+
PF6]+ ion at m/z 2127.
In order to examine the effect of the arsine donor ligands
on the steric and electronic properties of the {Pt2S2} core,
and to fully characterise one derivative of the {Pt2S2As4}
core, an X-ray structure determination was carried out on
the platinum(II)-cyclo-octadiene (cod) derivative 4. The
cation (illustrated in Fig. 5) has a very similar conformation
to that of the Ph3P analogue, although only 4 has crystallo-
graphically imposed C2 symmetry. In each case the Pt(cod)
group is coordinated to the {Pt2S2} metalloligand via the S
atoms with the cod group in the usual twisted boat form.
Several other Pt(cod) derivatives of [Pt2(l-E)2(PPh3)4]
compounds have been structurally characterised previ-
ously, namely the phosphine analogue of 4, [Pt2(l-S)2-
(PPh3)4Pt(cod)]2+ [17], as well as the selenide derivatives
[Pt2(l-Se)2(PPh3)4Pt(cod)]2+ and [Pt(l-Se)2(PPh3)2{Pt-
(cod)}2]2+ [22]. Deprotonation of a coordinated cod ligand
The syntheses of two metal complex derivatives, [Pt2(l-
S)2(AsPh3)4Pt(cod)](PF6)2
4 and [Pt2(l-S)2(AsPh3)4Pd-
(bipy)](PF6)2 5, were carried out on the macroscopic scale
by reaction of [Pt2(l-S)2(AsPh3)4] with [PtCl2(cod)] and
[PdCl2(bipy)], respectively. The reactions proceed by disso-
lution of the starting materials, giving slightly cloudy solu-
tions. Some dark orange insoluble matter is probably
Table 1
Major ions observed in the positive-ion ESI MS spectra (cone voltage
20 V) for reactions of [Pt2(l-S)2(AsPh3)4] with a selection of metal–halide
complexesa
Substrate
Observed ions (m/z)
[RhCl(cod)]2
[IrCl(cod)]2
[PtCl2(cod)]
[PdCl2(bipy)]
[RhCl2Cp*]2
[IrCl2Cp*]2
[RuCl2(g6-p-cymene)]2
PhHgCl
[Pt2(l-S)2(AsPh3)4Rh(cod)]+ (1890)
[Pt2(l-S)2(AsPh3)4Ir(cod)]+ (1979)
[Pt2(l-S)2(AsPh3)4Pt(cod)]2+ (991)
[Pt2(l-S)2(AsPh3)4Pd(bipy)]2+ (974)
[Pt2(l-S)2(AsPh3)4RhCp*]2+ (958)
[Pt2(l-S)2(AsPh3)4IrCp*]2+ (1003)
[Pt2(l-S)2(AsPh3)4Ru(g6-p-cymene)]2+ (957)
[Pt2(l-S)2(AsPh3)4HgPh]+ (1957)
a
Abbreviations used: cod = 1,5-cyclo-octadiene; bipy = 2,20-bipyridine;
Cp* = g5-C5Me5.

S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
2833
Fig. 4. Positive-ion ESI mass spectrum of the micro scale reaction mixture of [Pt2(l-S)2(AsPh3)4] and [RhCl2Cp*]2 in methanol at a cone voltage of 20 V,
showing exclusive formation of [Pt2(l-S)2(AsPh3)4RhCp*]2+. The inset shows a comparison of the observed (left) and calculated (right) isotope
distribution patterns for the parent dication.
in the derivative [Pt2(l-S)2(dppp)2Pt(cod)]2+ [dppp = Ph2P-
(CH2)3PPh2] has also been described [23]. Detailed bond
parameters for 4 are compared with those of the Ph3P ana-
logue in Table 2, and show some significant differences. All
of the Pt–S bond lengths of 4 are significantly longer, sug-
gesting a less tightly bound Pt3S2 core. While this might
have been expected for the bonds to the Pt(cod) moiety
as a consequence of the reduced basicity of the S-donor
atoms, it is surprising for the Pt–S bonds trans to the Ph3As
groups since these should have a lesser trans influence
than PPh3 groups. In this case, it may arise from the
wider fold angle between the two As2PtS2 groups (138.8ꢁ)
compared with that between the two P2PtS2 planes
(133.9ꢁ), which in turn is presumably allowed by lesser
interactions between the Ph3As groups and the Pt(cod) unit
as a consequence of longer Pt–As and As–C bonds. The
Pt–S bonds of 4 are significantly longer than those of a
series of {Pt2S2M} derivatives containing Ph2AsCH2-
2.4. Generation of mixed phosphine–arsine complexes
[Pt2(l-S)2(AsPh3)n(PPh3)4ꢀn
]
Having demonstrated the utility of ESI MS in probing the
chemistry of the arsine complex [Pt2(l-S)2(AsPh3)4], the
methodology has been extended to an investigation into
the synthesis of mixed phosphine–arsine derivatives of
the {Pt2S2} core. Reaction of equimolar quantities of
cis-[PtCl2(PPh3)2] and cis-[PtCl2(AsPh3)2] with excess
Na2S Æ 9H2O for 24 h in the usual manner gave an orange
solid in low yield. Because of the significantly different ioni-
sation efficiencies of [Pt2(l-S)2(PPh3)4] and [Pt2(l-
S)2(AsPh3)4], small samples of product were derivatised
using an alkylating agent, either n-butyl chloride or 4-bro-
mobenzyl bromide, in order to form soluble, cationic deriv-
atives and thus obtain an accurate product distribution.
4-Bromobenzyl bromide was the reagent of choice, because
it is a good (but not too powerful) alkylating agent that rap-
idly and selectively forms a monoalkylated product, is a con-
veniently handled solid, and avoids ion overlaps which
would occur with PhCH2Br itself. The resulting cationic ben-
zylated species are soluble in methanol, and the peak inten-
sity should closely reflect the abundance of the {Pt2S2}
species in the isolated product. Comparable results were
obtained for both alkylation methods, though the reaction
with n-butyl chloride was expectedly much slower, and
showed some underivatised [Pt2(l-S)2(PPh3)4] as its proton-
ated ion at m/z 1503.
´
CH2AsPh2 ligands recently described by Gonzalez-Duarte
et al. [13].
Interestingly, few structures of platinum complexes
containing tertiary arsine ligands trans to sulfur donor
ligands have been carried out, however, As–Pt bond dis-
˚
˚
tances of 2.361(1) A and 2.3293(6) A are observed in the
complexes [Pt{S2P(OEt)2}2{Ph2P(S)CH2CH2AsPh2}] and
[Pt{S2P(OiPr)2}(CH3)(AsPh3)], respectively, where the
arsine ligands are trans to a chelated dithiophosphate
ligand [24].

2834
S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
C(4)
C(1)
C(2)
C(3)
Pt(1)
S(1_2)
Pt(2)
As(2)
As(1)
S(1)
Pt(2_2)
Fig. 5. X-ray structure of the cation [Pt2(l-S)2(AsPh3)4Pt(cod)]2+, with selected atom labels. The PFꢀ6 counter ions and dichloromethane of crystallisation
are not shown.
(AsPh3)]+ and the tris-arsine [Pt2(l-S)(l-SCH2C6H4Br)-
Table 2
Selected bond parameters for [Pt2(l-S)2(EPh3)4Pt(cod)]2+ (E = As, P)
(PPh3)(AsPh3)3]+, respectively, indicating that the isolated
E = As (4)
E = Pa,b
product is actually a mixture of all possible [Pt2(l-S)2-
(AsPh3)n(PPh3)4ꢀn] species. No attempt was made to
increase the amounts of mixed species formed in this reac-
tion. Exchange of phosphine and arsine ligands was not
observed when an equimolar mixture of [Pt2(l-S)2(PPh3)4]
and [Pt2(l-S)2(AsPh3)4] was refluxed in methanol for 6 h,
and the reaction mixture analysed after 4-bromobenzyl
bromide derivatisation.
˚
Bond lengths (A)
Pt(1)–S(1)
Pt(2)–S(1)
Pt(2)–S(1)0
Pt(2)–E(1)
Pt(2)–E(2)
Pt(2)ꢁ ꢁ ꢁPt(2)0
Pt(1)ꢁ ꢁ ꢁPt(2)
2.418(3)
2.424(3)
2.427(3)
2.467(2)
2.486(2)
3.406(2)
3.101(2)
2.336(2)
2.368(2)
2.367(2)
2.299(2)
2.283(2)
3.323(2)
3.053(2)
Mixed phosphine–arsine species are also accessible from
ligand substitution reactions that utilise the lability of
AsPh3. A mixture of [Pt2(l-S)2(AsPh3)4] and excess PPh3
in methanol was stirred at room temperature, and aliquots
of the reaction mixture derivatised with 4-bromobenzyl
bromide for analysis by ESI MS, as above. Slow ligand
substitution was found to occur, giving a mixture of
[Pt2(l-S)2(AsPh3)n(PPh3)4ꢀn] species as their bromobenzyl
derivatives, as illustrated in Fig. 7. It is worth commenting
that the intensity of the [Pt2(l-S)2(PPh3)4] species was
greater than those of [Pt2(l-S)2(AsPh3)n(PPh3)4ꢀn] (n = 1–
3), possibly because substitution of one arsine ligand pro-
duces a derivative that is more basic and more soluble,
which then undergoes further substitution steps more read-
ily. Solubility of the final product is not a factor in the ESI
MS analysis, because the derivatisation step employed pro-
duces a soluble, charged species. Such ligand substitution
might provide an alternative pathway to new phosphine-
containing {Pt2S2} systems.
Bond angles (ꢁ)
S(1)–Pt(1)–S(1)0
S(1)–Pt(2)–S(1)0
E(1)–Pt(2)–E(2)
80.3(2)
80.0(2)
96.7(1)
79.9(1)
78.7(1)
98.6(1)
Dihedral angles (ꢁ)
E2Ptð2ÞS2=E02Ptð2Þ0S2
E2Pt(2)S2/Pt(1)S2
a
138.8
110.5
133.9
113.1
From Ref. [17], renumbered to correspond to that of 4.
Averaged over chemically equivalent bonds where appropriate.
b
The spectrum for the 4-bromobenzyl bromide system is
illustrated in Fig. 6; no dialkylated species were observed
in the reaction timescale used (20 min). The main species
are [Pt2(l-S)(l-SCH2C6H4Br)(PPh3)4]+ (m/z 1674), [Pt2(l-
S)(l-SCH2C6H4Br)(AsPh3)4]+ (m/z 1849), and the expected
mixed phosphine–arsine derivative [Pt2(l-S)(l-SCH2C6H4-
Br)(PPh3)2(AsPh3)2]+ (m/z 1761). In addition to these spe-
cies, low intensity ions at m/z 1717 and 1805 are attributed
to the tris-phosphine [Pt2(l-S)(l-SCH2C6H4Br)(PPh3)3-

S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
2835
3. Conclusions
Sodium sulfide nonahydrate (Ajax Chemicals, Sydney,
Australia), ammonium hexafluorophosphate (Aldrich),
benzyl chloride (BDH), butyl chloride (Riedel de Ha¨en),
iodomethane (Aldrich), 4-bromobenzyl bromide (Aldrich),
benzyl bromide (BDH), triphenylarsine (Fluka) and phenyl
mercury chloride (Aldrich) were used as supplied.
The complexes [Pt2(l-S)2(PPh3)4] [20], cis-[PtCl2-
(AsPh3)2] [26], cis-[PtCl2(PPh3)2] [27], [RhCl(cod)]2 [28],
[IrCl(cod)]2 [29], [PtCl2(cod)] [30], [PdCl2(bipy)] [31],
[RhCl2Cp*]2 [32], [IrCl2Cp*]2 [32], and [RuCl2(g6-p-cym-
ene)]2 [33] were synthesised by the literature procedures.
The complex [Pt2(l-S)(l-SCH2Ph)(PPh3)4]PF6 was pre-
pared from [Pt2(l-S)2(PPh3)4] and PhCH2Br in methanol
[20], and precipitated by addition of excess NH4PF6.
The triphenylarsine {Pt2S2} system has been synthesised
for the first time, and the reactivity of this complex towards
alkylating agents indicates that the reactivity of the sulfide
ligands has been moderated by the more poorly electron-
donating arsines, which are also more labile than the phos-
phine ligands. The results support the conclusions previ-
´
ously made by Gonzalez-Duarte and co-workers on the
corresponding system with Ph2AsCH2CH2AsPh2 ligands
[13]. The decreased lability of the bidentate arsine ligands
suggests that this is a more workable system than the labile
AsPh3 system. The use of other neutral ancillary ligands on
the {Pt2S2} core could furnish further interesting develop-
ments in the chemistry of this enigmatic system.
4.2. Synthesis of [Pt2(l-S)2(AsPh3)4] (2)
4. Experimental
A suspension of the complex cis-[PtCl2(AsPh3)2] (1.00 g,
1.139 mmol) and powdered Na2S Æ 9H2O (1.60 g,
6.66 mmol) in benzene (40 mL) was stirred vigorously for
48 h, giving an orange suspension. The solid was filtered
off, washed with benzene (2 · 10 mL) and copious quanti-
ties of distilled water, and dried under vacuum to give 2
as an orange solid (220 mg, 21%). The complex could not
be obtained analytically pure: Found: C, 45.9; H, 3.45%;
C72H60As4Pt2S2 requires: C, 51.5; H, 3.6%.
4.1. General methods and materials
General instrumental details were as described in recent
papers from these laboratories [16–18]. Benzene was AR
grade, and used as supplied. Products were recrystallised
from dichloromethane and diethyl ether that were dried
and distilled (from CaH2 and sodium-benzophenone ketyl,
respectively) under a nitrogen atmosphere prior to use.
Petroleum spirits refers to the fraction of boiling range
40–60 ꢁC.
Electrospray mass spectra were recorded using positive-
ion mode on a VG Platform II instrument, using methanol
as the mobile phase and solvent. Assignment of ions was
aided by use of the ISOTOPE simulation program [25].
4.3. Synthesis of [Pt2(l-S)2(AsPh3)4] incorporating free
AsPh3
The method above was repeated, except that tripheny-
larsine (0.50 g, 1.63 mmol) was added to the reaction
Fig. 6. Positive-ion ESI mass spectrum of the reaction mixture cis-[PtCl2(AsPh3)2] + cis-[PtCl2(PPh3)2] + Na2S, after isolation and derivatisation with
4-bromobenzyl bromide, showing a series of mixed phosphine–arsine derivatives [Pt2(l-S)(l-SCH2C6H4Br)(PPh3)n(AsPh3)4ꢀn]+.

2836
S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
Fig. 7. The formation of ligand-exchanged species [Pt2(l-S)2(AsPh3)n(PPh3)4ꢀn] from the reaction of [Pt2(l-S)2(AsPh3)4] and excess PPh3 in methanol
(after derivatisation with 4-bromobenzyl bromide) is shown by the ESI mass spectrum of the reaction mixture at a cone voltage of 20 V.
mixture. [Pt2(l-S)2(AsPh3)4] was isolated as a deep orange
solid (588 mg, 62%). Found: C, 42.2; H, 3.6%.
rapid dissolution of the starting materials and formation
of a cloudy orange solution containing some dark, insoluble
matter. After 15 min the solution was filtered, and the filter
washed with an additional 10 mL of methanol, giving a clear
lemon-yellow solution. Solid NH4PF6 (300 mg, excess) was
added with stirring. After 10 min, water was added dropwise
until the solution turned cloudy, and the mixture was stirred
for 20 min. The yellow solid product was filtered, washed
successively with water (10 mL) and petroleum spirits
(10 mL) and dried under vacuum to give 3a as a yellow solid
(95 mg, 53%). Found: C, 47.2; H, 3.4%. C79H66As4BrF6-
PPt2S2 requires: C, 47.6; H, 3.3%. M.p. 174–178 ꢁC. ESI
MS (CH2Cl2–MeOH), 20 V, m/z 1849, [M]+ (100%).
4.4. Protonation study of [Pt2(l-S)2(AsPh3)4] and
[Pt2(l-S)2(PPh3)4]
An equimolar mixture of the complexes [Pt2(l-
S)2(AsPh3)4] (10 mg) and [Pt2(l-S)2(PPh3)4] (9 mg) in meth-
anol (30 mL) was stirred for 10 min, giving a light yellow
solution and some undissolved solid. An aliquot of this
mixture was taken, centrifuged, and analysed by positive-
ion ESI MS, revealing a major peak due to [Pt2(l-
S)2(PPh3)4+H]+ (m/z 1503).
4.5. Alkylation study of [Pt2(l-S)2(AsPh3)4] and of
[Pt2(l-S)2(AsPh3)4]/[Pt2(l-S)2(PPh3)4] mixtures
4.7. Synthesis of [Pt2(l-S)(l-SCH2C6H5)(AsPh3)4]PF6 (3b)
Following an analogous method for complex 3a, from
[Pt2(l-S)2(AsPh3)4] (100 mg, 0.060 mmol) gave complex
3b as a yellow solid (89 mg, 78%). Found: C, 48.9; H,
3.5%. C79H67As4F6PPt2S2 requires: C, 49.5; H, 3.5%.
M.p. decomp. >250 ꢁC. ESI MS (CH2Cl2–MeOH), 20 V,
[Pt2(l-S)2(AsPh3)4] (10 mg) or an equimolar mixture of
[Pt2(l-S)2(AsPh3)4] and [Pt2(l-S)2(PPh3)4] in methanol
(30 mL) was treated with an excess of the appropriate
alkylating agent (n-butyl chloride or 4-bromobenzyl bro-
mide) with stirring. Aliquots of the reaction mixture were
taken and analysed by ESI MS.
1
m/z 1770, [M]+ (100%). H NMR (CDCl3), d 7.37–6.85
3
(m, Ph), 3.99 [s, CH2, J(PtH) not resolved].
4.6. Synthesis of [Pt2(l-S)(l-SCH2C6H4Br)-
(AsPh3)4]PF6 (3a)
4.8. Complex formation with [Pt2(l-S)2(AsPh3)4],
monitored by ESI MS
4-Bromobenzyl bromide (150 mg, 0.600 mmol) was
added to a stirred suspension of [Pt2(l-S)2(AsPh3)4]
(150 mg, 0.089 mmol) in methanol (30 mL), resulting in
The complex (ca. 0.1 mg) and the metal halide substrate
(ca. 0.1 mg) were suspended in methanol (2 mL) and sha-
ken to effect reaction and formation of a clear solution.

S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
2837
After centrifugation, the ESI MS spectrum was recorded
using a cone voltage of 20 V.
0.317 mmol) added. The mixture was stirred and after sev-
eral days the ESI mass spectrum of an aliquot, derivatised
with excess 4-bromobenzyl bromide, showed all possible
[Pt2(l-S)2(PPh3)n(AsPh3)4ꢀnCH2C6H4Br]+ ions.
4.9. Synthesis of [Pt2(l-S)2(AsPh3)4Pt(cod)](PF6)2 (4)
[Pt2(l-S)2(AsPh3)2]
(237 mg,
0.141 mmol)
and
4.13. Investigation of exchange between
[Pt2(l-S)2(PPh3)4] and [Pt2(l-S)2(AsPh3)4]
[PtCl2(cod)] (53 mg, 0.142 mmol) were suspended in meth-
anol (30 mL) and stirred for 30 min, giving a cloudy yel-
low solution, which was filtered. To the filtrate was
added, with stirring, NH4PF6 (300 mg, excess), producing
a yellow precipitate. After 20 min, water (20 mL) was
added to assist precipitation of the product, which was fil-
tered, washed successively with water (20 mL) and petro-
leum spirits (20 mL), and dried under vacuum to give 4 as
a yellow solid (110 mg, 34%). Found: C, 41.7; H, 3.2%.
C80H72As4F12P2Pt3S2 requires: C, 42.25; H, 3.2%. M.p.
260–262 ꢁC. The complex was recrystallised by vapour
diffusion of diethyl ether into a dichloromethane solution
of the complex at room temperature. ESI MS (CH2Cl2–
MeOH), 20 V, m/z 991, [M]2+ (100%), m/z 2127,
[Pt2(l-S)2(AsPh3)4] (22 mg, 0.013 mmol) and [Pt2(l-
S)2(PPh3)4] (19 mg, 0.013 mmol) were dissolved in metha-
nol (40 mL) and the mixture refluxed for 6 h. An aliquot
of the reaction mixture was treated with excess 4-bromob-
enzyl bromide, and analysed by positive-ion ESI MS.
4.14. X-ray structure determination of [Pt2(l-
S)2(AsPh3)4Pt(cod)](PF6)2 Æ CH2Cl2 (4 Æ CH2Cl2)
A yellow crystal of moderate quality was obtained from
CH2Cl2/ether. Data were collected on a Siemens SMART
CCD diffractometer using standard procedures and soft-
ware [34]. Icing problems near the end of collection meant
only 85% of the theoretical data were collected, but the set
gave a reasonable refinement. Empirical absorption correc-
tions were applied (SADABS [35]). The structure was solved
by direct methods and developed and refined on F2 using
the SHELX programmes [36].
1
[M+PF6]+ (5%). H NMR, d 7.35–7.19 (m, Ph), 4.70 [s,
Pt–CH, J(PtH) ca. 52] and 2.64 (s, br, CH2).
4.10. Synthesis of [Pt2(l-S)2(AsPh3)4Pd(bipy)](PF6)2 (5)
[Pt2(l-S)2(AsPh3)4]
(200 mg,
0.119 mmol)
and
[PdCl2(bipy)] (60 mg, 0.180 mmol) were suspended in
methanol (30 mL) and stirred for 40 min, giving a cloudy
orange solution, which was filtered. To the stirred filtrate
was added NH4PF6 (300 mg, excess), producing an
orange-brown precipitate. After 20 min, water (15 mL)
was added to assist precipitation of the product, which
was filtered, washed successively with water (10 mL) and
petroleum spirits (10 mL), and dried under vacuum to give
5 as an orange-brown solid (120 mg, 45%). Found: C, 43.3;
H, 3.3; N, 1.35%; C82H68N2As4F12P2PdPt2S2 requires: C,
44.1; H, 3.1; N, 1.3%. M.p. >250 ꢁC. ESI MS (CH2Cl2–
MeOH), 20 V, m/z 970.5, [M]2+ (100%), m/z 2086,
[M+PF6]+ (8%).
Crystal data: C81H74P2F12As4S2Cl2Pt3, Mr 2357.31,
monoclinic, space group C2/c, Z = 4, a = 16.118(16) A,
˚
˚
˚
b = 22.87(2) A, c = 23.15(2) A, b = 91.682(17)ꢁ, V = 8531
(14) A , Dcalc = 1.835 g cmꢀ3, l(Mo-Ka) = 6.66 mmꢀ1
,
3
˚
size 0.90 · 0.38 · 0.36 mm3, Tmax,min = 1.000, 0.392,
F(000) = 4520, T = 93 K. Total data 12832, unique data
6803 (Rint = 0.0446), 3ꢁ < 2h < 51ꢁ, R1 (I > 2r(I)) =
0.0550, wR2 (all data) =ꢀ03.1557, goodness-of-fit = 1.119,
˚
residual De +3.8/ꢀ3.6 e A
.
The atoms of the cations, anions and CH2Cl2 were
refined anisotropically with H atoms included in calculated
positions. The cation and one of the anions lie on twofold
axes, the other anion on an inversion centre, and the sol-
vent molecule is disordered about an inversion centre and
was poorly behaved during refinement.
4.11. Synthesis of mixed [Pt2(l-S)2(PPh3)n(AsPh3)4ꢀn
from cis-[PtCl2(EPh3)2]
]
5. Supplementary information
A
suspension
of
cis-[PtCl2(PPh3)2]
(250 mg,
0.316 mmol), cis-[PtCl2(AsPh3)2] (280 mg, 0.319 mmol)
and powdered Na2S Æ 9H2O (0.8 g, 3.33 mmol) in benzene
(25 mL) was stirred vigorously for 24 h, giving an orange
suspension. Isolation of the product as for [Pt2(l-S)2-
(AsPh3)4] gave an orange solid (90 mg) that was analysed
by ESI MS after derivatisation of an aliquot in methanol
with excess 4-bromobenzyl bromide or n-butyl chloride.
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre, CCDC No.
272628 (4). Copies of this information can be obtained free
of charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44 1223 336 033; e-mail
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
4.12. Synthesis of mixed [Pt2(l-S)2(PPh3)n(AsPh3)4ꢀn
from [Pt2(l-S)2(AsPh3)4] and PPh3
]
Acknowledgements
We thank the University of Waikato (UW) and the Na-
tional University of Singapore (NUS) for financial support
of this work. WH thanks the Asia:NZ Foundation for a
[Pt2(l-S)2(AsPh3)4] (63 mg, 0.038 mmol) was suspended
in methanol (30 mL) and triphenylphosphine (83 mg,

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S. Jeram et al. / Journal of Organometallic Chemistry 691 (2006) 2827–2838
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