Aryldiplatinum(II) complexes containing dimethyl sulfide and bis(diphenylphosphino)methane as bridging ligands

Article abstract of DOI:10.1021/om990784t

A versatile and yet simple approach to synthesize a series of uncommon symmetrical and unsymmetrical diplatinum(II) complexes cis,cis-[Ar₂Pt(μ-SMe₂)(μ-dppm)PtAr′₂], 3, in which Ar or Ar′ = Ph, p-MeC₆H₄, m-MeC₆H₄, or p-MeOC₆H₄, has been developed by the reaction of either cis-[PtAr₂(SMe₂)₂], 1, with [PtAr′₂(dppm)], 2, or cis-[PtAr′₂(SMe₂)₂] with [PtAr₂(dppm)].

Full text of DOI:10.1021/om990784t

Organometallics 2000, 19, 2751-2755
2751
Ar yld ip la tin u m (II) Com p lexes Con ta in in g Dim eth yl
Su lfid e a n d Bis(d ip h en ylp h osp h in o)m eth a n e a s Br id gin g
Liga n d s
Mehdi Rashidi,* Majid Hashemi, and Mozhgan Khorasani-Motlagh
Chemistry Department, College of Sciences, Shiraz University, Shiraz, Iran, 71454
Richard J . Puddephatt
Chemistry Department, The University of Western Ontario,
London, Ontario, N6A 5B7, Canada
Received October 4, 1999
A versatile and yet simple approach to synthesize a series of uncommon symmetrical and
unsymmetrical diplatinum(II) complexes cis,cis-[Ar2Pt(µ-SMe2)(µ-dppm)PtAr′2], 3, in which
Ar or Ar′ ) Ph, p-MeC6H4, m-MeC6H4, or p-MeOC6H4, has been developed by the reaction of
either cis-[PtAr2(SMe2)2], 1, with [PtAr′2(dppm)], 2, or cis-[PtAr′2(SMe2)2] with [PtAr2(dppm)].
In tr od u ction
CH2CH2)(µ-dppm)}2] have been synthesized.7,8 A ver-
satile approach to bis (dppm-bridged) platinum(II)
species uses the η1-dppm intermediates, [PtR2(η1-
dppm)2].9 Thus, the dimeric complex cis,cis-[(o-MeC6H4)2-
Pt(µ-dppm)2PtMe2] has been synthesized and structur-
ally characterized.9
In this study, we observed that the bis (dppm-bridged)
diplatinum(II) complexes with aryl ligands on both
metal centers were not easily formed, most probably due
to steric overcrowding. However, using a general ap-
proach, we have synthesized a series of symmetrical and
unsymmetrical diplatinum(II) complexes of the type cis,-
cis-[Ar2Pt(µ-SMe2)(µ-dppm)PtAr′2], 3, in which Ar and
Ar′ are identical or different aryl ligands. The lower
steric requirements and the ability of SMe2 to act as a
bridging ligand appear to be responsible for the forma-
tion of this uncommon type of complex.
Although dinuclear platinum complexes have been
known for many years, their number and variety have
increased tremendously through the use of bridging
bidentate phosphine ligands, notably bis(diphenylphos-
phino)methane (dppm ) Ph2PCH2PPh2), with a bite size
more suitable for bridging than chelation.1 Most plati-
num complexes that contain dppm acting as bridging
ligand contain M2(µ-dppm)2 units, and in many cases
metal-metal bonds are present as well.2,3 Recently,
anionic dinuclear platinum(II) complexes of general
formula [NBu4][(C6F5)2Pt(µ-X)(µ-dppm)Pt(C6F5)2] each
with two very different bridging ligands, a dppm and a
halide ligand (X), have been synthesized and structur-
ally characterized,4 and the reactivity of this type of
complex toward Lewis acids such as AgClO4 has been
studied.5 However, dinuclear complexes with such dif-
ferent ligands bridging the metal centers at the same
time are unusual.2,3
Resu lts a n d Discu ssion
In the binuclear complexes [Pt2Me4(µ-R2PCH2PR2)2]
in which R ) Me, Et, or Ph, steric effects influence the
stability and the reactivity to a major extent. Thus, the
bulk of the substituents R in the bidentate ligands has
a significant effect on the stability of mononuclear
[PtMe2(R2PCH2PR2)] vs dinuclear [Pt2Me4(µ-R2PCH2-
PR2)2], and for R ) Ph (i.e., dppm ligand), both com-
plexes could be isolated, although the mononuclear form
was more stable.6 For the metallacyclic analogues of the
above dppm complexes, again both mononuclear [Pt-
(CH2CH2CH2CH2)(dppm)] and dinuclear [{Pt(CH2CH2-
Syn th esis of th e Com p lexes. The synthetic route
to the diplatinum(II) complex cis,cis-[Ph2Pt(µ-SMe2)(µ-
dppm)PtPh2], 3a , as well as some of its reactions, is
depicted in Scheme 1. Reaction of cis-[PtPh2(SMe2)2],
1a , with 0.5 equiv of dppm in CH2Cl2 or CHCl3 gave
after 8 h the dimeric complex 3a in good yield. This
reaction was monitored by 1H NMR spectroscopy in
CDCl3, and it was found that [PtPh2(dppm)], 2a , was
formed first. This then slowly reacted with 1a to give
the diplatinum(II) complex 3a , probably via a transient
intermediate 4. The complex 3a reacted slowly (over 48
h) with excess SMe2 in C6D6 at 50 °C and was converted
to the monomeric complex 2a , as monitored by 31P NMR
spectroscopy. An equivalent amount of cis-[PtPh2-
(1) Anderson, G. K. Adv. Organomet. Chem. 1993, 35, 1.
(2) Puddephatt, R. J . Chem. Soc. Rev. 1983, 99.
(3) Chaudret, B.; Delavaux, B.; Poilblanc, R. Coord. Chem. Rev.
1988, 86, 191.
(4) Casas, J . M.; Falvello, L. R.; Fornies, J .; Martin, A.; Tomas, M.
J . Chem. Soc., Dalton Trans. 1993, 1107.
(5) Casas, J . M.; Falvello, L. R.; Fornies, J .; Martin, A. Inorg. Chem.
1996, 35, 7867.
(6) Muir, L. M.; Muir, K. W.; Frew, A. A.; Ling, S. S. M.; Thompson,
M. A.; Puddephatt, R. J . Organometallics 1984, 3, 1637.
(7) Pringle, P. G.; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1984,
849.
(8) Rashidi, M.; Esmaeilbeig, A. R.; Shahabadi, N.; Tangestaninejad,
S.; Puddephatt, R. J . J . Organomet. Chem. 1998, 53, 568.
(9) Hutton, A. T.; Pringle, P. G.; Shaw. B. L. J . Chem. Soc., Dalton
Trans. 1985, 1677.
10.1021/om990784t CCC: $19.00 © 2000 American Chemical Society
Publication on Web 06/14/2000

2752 Organometallics, Vol. 19, No. 14, 2000
Rashidi et al.
Ta ble 1. Ch a r a cter iza tion Da ta for Com p lexes
Sch em e 1
cis,cis-[Ar 2P t(µ-SMe2)(µ-d p p m )P tAr ′2], 3
elemental analysisc (%)
complexa
yield (%) mpb (°C)
C
H
3a ‚CH2Cl2
96
79
86
69
91
81
73
82
90
86
141
147
132
132
136
134
132
126
137
135
50.5
(50.8)
54.4
(54.4)
53.7
(53.6)
51.5
(52.2)
52.2
(52.2)
53.7
(53.7)
49.8
(50.3)
53.4
(53.6)
53.0
4.0
(4.1)
4.9
(4.6)
4.7
(4.6)
4.5
(4.3)
4.6
(4.3)
4.5
(4.4)
4.2
(4.2)
4.8
(4.6)
4.5
3b‚0.2CH2Cl2
3c‚0.5CH2Cl2
3d
3e‚3/4CH2Cl2
3f‚0.2CH2Cl2
3g‚CH2Cl2
3h ‚0.5CH2Cl2
3i‚0.1CH2Cl2
3j‚0.5CH2Cl2
(53.3)
52.4
(52.2)
(4.5)
4.6
(4.5)
a
The solids tenaciously retain fractional amounts of solvent as
confirmed by 1H NMR spectroscopy. b Decomposed. c Found (calcd).
gave the dimeric complex cis,cis-[(p-MeC6H4)2Pt(µ-SMe2)-
(µ-dppm)Pt(p-MeC6H4)2], 3b. Again, 3b further reacted
with 1 equiv of dppm to yield the mononuclear complex
[Pt(p-MeC6H4)2(dppm)], 2b.
(SMe2)2], 1a , was also present in the solution, and on
evaporation of the solvent and excess SMe2, the dimer
3a was re-formed along with trace amounts of 1a and
The above results directed us to develop the general
approach shown in Scheme 2 to allow the synthesis of
a series of symmetrical and unsymmetrical diplatinum-
(II) complexes of the type cis,cis-[Ar2Pt(µ-SMe2)(µ-
dppm)PtAr′2], 3. Thus, the reaction of either cis-[PtAr2-
(SMe2)2], 1, with [PtAr′2(dppm)], 2, or cis-[PtAr′2(SMe2)2]
with [PtAr2(dppm)] at room temperature yielded the
corresponding unsymmetrical complexes 3.
1
2a , as confirmed by H and 31P NMR spectra. Hence
the reaction of 1a and 2a to give 3a and SMe2 is shown
to be reversible. Reaction of 3a with 1 equiv of dppm in
CDCl3 and at room temperature gave, after 30 h, [PtPh2-
(dppm)], 2a , and free SMe2 in a 2:1 mol ratio as checked
1
by 31P and H NMR spectroscopy. It was not possible to
convert 2a to the dimer 3a by reaction with SMe2. The
reaction of the dimeric complex [Pt2Ph4(µ-SMe2)2] with
1 equiv of dppm in CDCl3 similarly gave the dinuclear
complex 3a . Similarly the complex cis-[Pt(p-MeC6H4)2-
(SMe2)2], 1b, was reacted with 0.5 equiv of dppm and
Ch a r a cter iza tion of th e Com p lexes. The com-
plexes 3 were fully characterized using microanalysis
1
(Table 1) and 31P (Table 2), H (Table 3) and 13C (Table
Sch em e 2

Aryldiplatinum(II) Complexes
Organometallics, Vol. 19, No. 14, 2000 2753
Ta ble 2. 31P NMR Da ta for Com p lexes
cis,cis-[Ar 2P t(µ-SMe2)(µ-d p p m )P tAr ′2], 3, in CDCl3
complex
δ(PA)
1J PtPA
δ(PB)
1J PtPB
3J PtP
2J PP
3a
3b
3c
3d
3e
3f
3g
3h
3i
15.16
15.40
16.11
15.66
15.40
15.46
15.58
15.17
15.31
14.52
1808
1805
1797
1822
1806
1803
1814
1805
1805
1821
22
22
18
21
b
b
b
b
b
40.5
41.0
41.0
40.5
40.3
42.6
41.3
42.5
41.1
42.0
15.51
16.34
15.72
16.16
15.55
15.29
1806a
1801
1814a
1798
1805a
1797
3j
b
a
b
Short-range satellites for PA and PB were overlapped. Not
resolved.
Ta ble 3. 1H NMR Da ta for Com p lexes
cis,cis-[Ar 2P t(µ-SMe2)(µ-d p p m )P tAr ′2], 3, in CDCl3
a
SMe2
dppm
CH3 on Ar CH3 on Ar′
complex δ(Me) (3J PtH
)
δ(CH2) (2J PH
)
δ(CH3)
δ(CH3)
3a
3b
3c
3d
3e
3f
3g
3h
3i
1.43
(20.1)
1.40
(20.0)
1.42
(19.3)
1.43
(19.3)
1.45
(20.0)
1.41
(19.6)
1.47
(19.2)
1.40
(19.7)
1.43
3.29
(7.5)
3.26
(7.3)
3.34
(7.4)
3.30
(7.5)
3.30
(7.3)
3.30
(7.5)
3.34
(7.4)
3.29
(7.4)
3.29
(7.2)
3.30
(7.4)
1.99
2.02
1.86
2.09
3.55
3.59
1.99
2.02
1.86
2.09
3.55
3.59
2.02
2.05
1.82
2.05
3.59
3.61
1.82
2.05
3.56
3.59
3.56
3.60
F igu r e 1. 31P NMR spectra (202.5 MHz) of (a) cis,cis-[(m-
MeC6H4)2Pt(µ-SMe2)(µ-dppm)Pt(m-MeC6H4)2], 3c, and (b)
cis,cis-[(p-MeC6H4)2Pt(µ-SMe2)(µ-dppm)Pt(m-MeC6H4)2], 3h .
1.99
2.03
2.00
2.04
1.83
2.06
(19.2)
1.41
(19.2)
is characteristic of SMe2 acting as a bridging ligand
between platinum centers, but with the unusual chemi-
cal shift δ ) 1.42.10 A similar characteristic quintet was
3j
a
Appeared as a quintet with relative intensity 1:8:18:8:1.
1
observed in the H NMR spectrum of each of the other
symmetrical or unsymmetrical dimers 3. Also, in the
case of methyl-substituted aryl ligands attached to the
same platinum center, two Me resonances were ob-
served, which confirmed the inequivalency of the aryl
ligands at each platinum center.
4) NMR spectroscopy. The complex 3a was further
characterized by 195Pt NMR spectroscopy (see below).
In the 31P NMR spectra of the symmetrical complexes
3a -3d (Figure 1a), the two equivalent phosphorus
atoms resonated as a singlet around 15 ppm and showed
platinum satellites. When one platinum center is 195Pt,
the two phosphorus atoms are no longer equivalent and
appeared as two sets of satellites, one set due to the
phosphorus atom attached directly to the 195Pt atom
(1J PtP around 1800 Hz) and the other set due to the
phosphorus atom further away from 195Pt (3J PtP around
20 Hz). The splitting in the satellites corresponds to a
2J PP value of around 40 Hz.
The 13C NMR spectra of complexes 3 were also useful
for structure determination. In particular, the aryl
carbon atoms attached directly to the platinum centers
appeared further downfield from the other aromatic
carbons and showed that the two aryl groups on each
platinum center are inequivalent. Thus, the carbon
2
atoms trans or cis to phosphorus gave J PC(trans) around
2
120 Hz and J PC(cis) around 6 Hz, respectively. Also, the
1J PtC for the carbon atom trans to the phosphorus atom
is about 140 Hz lower than the 1J PtC for the carbon atom
trans to SMe2 due to the higher trans-influence of
phosphorus over sulfur.
As expected in the light of the above data, the 195Pt
NMR spectrum of 3a contained a doublet of doublets at
1
3
δ ) -4558, with J PtP and J PtP values (1809 and 25
1
3
Hz, respectively) close to the J PtP and J PtP couplings
obtained from the 31P spectrum. The 195Pt NMR data
are particularly useful since it clearly confirms the
presence of only one dppm bridging two platinum atoms.
In the 31P NMR spectra of the unsymmetrical com-
plexes 3e-3j (Figure 1b), the two phosphorus atoms are
inequivalent, appeared as an AB pattern, and showed
short-range coupling platinum satellites, while the long-
range coupling satellites were not resolved.
On the basis of the above results, the core given in
Figure 2 with a twisted skeleton is suggested for the
dimers 3. As can be seen, each dimer is formed by two
cis-Pt(aryl)2 fragments joined by a bidentate dppm and
a SMe2 acting as bridging ligands. This results in two
equivalent phosphorus atoms in the 31P NMR spectra
of symmetrical dimers 3a -3d , while the aryl ligands
1
on each platinum center are inequivalent in the H and
In the 1H NMR spectrum of complex 3a , a quintet
with relative intensity 1:8:18:8:1 was observed, which
(10) Rashidi, M.; Fakhroeian, Z.; Puddephatt, R. J . J . Organomet.
Chem. 1991, 261, 406.

2754 Organometallics, Vol. 19, No. 14, 2000
Rashidi et al.
Ta ble 4. 13C NMR Da ta for Com p lexes cis,cis-[Ar 2P t(µ-SMe2)(µ-d p p m )P tAr ′2], 3, in CDCl3
substitution on aryl ligand; C1 of Ara trans
C1 of Ara trans
C1 of Ar′a trans
C1 of Ar′a trans
SMe2
dppm
CH3 or OCH3
to P
to SMe2 (cis to P)
to P
to SMe2 (cis to P)
complex δ(Me) δ(CH2) (1J PC
)
δ(CH3)Ar
δ(CH3)Ar′
δ(C1) (2J PC,1J PtC
)
δ(C1) (2J PC,1J PtC
)
δ(C1) (2J PC,1J PtC
)
δ(C1) (2J PC,1J PtC
)
3a
3b
3c
3d
3e
3f
3g
3h
3i
24.17
24.13
23.96
24.30
24.17
24.16
24.26
24.10
24.28
24.20
24.17
(15.0)
24.23
(14.2)
23.96
(15.1)
24.10
(15.0)
24.22
(14.8)
24.10
(14.1)
24.20
(13.8)
24.10
(14.6)
24.20
(14.3)
24.02
(15.3)
163.8
(116.3, 904.8)
159.9
(118.1, 907.4)
163.8
(116.3, 901.4)
154.0
(120.4, 919.9)
164.0
(116.4, 904.7)
164.1
(116.6, 903.1)
164.0
(117.0, 905.1)
163.8
145.3
(4.3, 1040.4)
141.0
(3.9, 1054.2)
145.1
(3.8, 1049.7)
135.0
(4.0, 1068.0)
145.4
(6.2, 1046.8)
145.5
(7.9, 1048.0)
145.4
(3.8, 1055.5)
140.9
163.8
(116.3, 904.8)
159.9
(118.1, 907.4)
163.8
(116.3, 901.4)
154.0
(120.4, 919.9)
159.9
(118.0, 903.7)
163.8
(116.2, 897.6)
153.9
(121.4, 923.4)
159.8
145.3
(4.3, 1040.4)
141.0
(3.9, 1054.2)
145.1
(3.8, 1049.7)
135.0
(4.0, 1068.0)
140.8
(4.7, 1044.0)
145.1
(7.8, 1036.5)
134.9
(2.7, 1081.5)
145.1
21.16
21.32
21.90
21.92
55.24
55.60
21.16
21.32
21.90
21.92
55.24
55.60
21.10
21.27
22.02
22.02
55.25
55.61
21.97
21.97
55.32
55.68
55.66
55.28
21.13
21.31
21.20
21.37
22.01
22.02
(117.0, 903.2)
159.8
(116.4, 909.5)
163.8
(8.8, 1045.4)
141.0
(6.4, 1051.0)
145.2
(118.2, 909.4)
154.1
(120.4, 919.6)
154.1
(7.5, 1059.2)
135.1
(8.2, 1061.7)
135.1
3j
(113.2, 903.2)
(3.0, 1040.0)
(120.3, 914.0)
(6.9, 1060.5)
a
C1 is the aryl carbon directly connected to Pt.
[PtPh2(dppm)], 2a , and [Pt(p-MeC6H4)2(dppm)], 2b, were
prepared by the literature method.12 The following complexes
were prepared similarly. [Pt(m-MeC6H4)2(dppm)], 2c: yield
79%; mp 222 °C dec. Anal. Calcd for [Pt(m-MeC6H4)2(dppm)]:
C, 61.5; H, 4.7. Found: C, 61.0; H, 4.8. 1H NMR (CDCl3): δ
1
2
2.10 (s, 6 H, ArCH3), 4.42 (t, J PH ) 9.3 Hz, J PtH ) 21.4 Hz, 2
F igu r e 2. Suggested structure and proposed mechanism
of fluxionality of the complexes cis,cis-[Ar2Pt(µ-SMe2)(µ-
dppm)PtAr′2].
H, CH2P2). 31P NMR (CDCl3): δ - 37.01 (s, J PtP ) 1385 Hz).
[Pt(p-MeOC6H4)2(dppm)], 2d : yield 81%; mp 222 °C dec. Anal.
Calcd for [Pt(p-MeOC6H4)2(dppm)]: C, 59.0; H, 4.5. Found: C,
1
13C NMR spectra. The phosphorus atoms of dppm are
inequivalent in the unsymmetrical dimers 3e-3j since
the metal centers are attached to different aryl ligands.
This structural type was originally determined by
single-crystal X-ray diffraction studies5 for cis,cis-[(C6F5)2-
Pt(µ-SC4H8)(µ-dppm)Pt(C6F5)2]. Note, however, that the
static structure shown in Figure 2 should give two MeS
and CHP2 resonances when Ar * Ar′. Since only one
was observed, the complexes must be fluxional, as
indicated in Figure 2. The Pt2C4S(P2C) atoms are then
effectively coplanar.
1
59.0; H, 4.7. H NMR (CDCl3): δ 3.68 (s, 6 H, ArOCH3), 4.44
(t, 2J PH ) 9.3 Hz, 2 H, CH2P2). 31P NMR (CDCl3): δ -38.00 (s,
1J PtP ) 1418 Hz).
cis,cis-[P h 2P t(µ-SMe2)(µ-d p p m )P tP h 2], 3a . (i) To a solu-
tion of cis-[PtPh2(SMe2)2] (200 mg, 0.42 mmol) in CH2Cl2 (10
mL) was added dppm (81 mg, 0.21 mmol). The reaction
mixture was stirred for 8 h at room temperature. The solvent
was removed, and residue was washed twice with acetone (2
mL). The white solid was dried in vacuo.
A similar procedure using [Pt2Ph4(µ-SMe2)2] (200 mg, 0.24
mmol) and dppm (94 mg, 0.24 mmol) gave the same product.
(ii) A mixture of cis-[PtPh2(SMe2)2] (65 mg, 0.14 mmol) and
[PtPh2(dppm)] (100 mg, 0.14 mmol) in CH2Cl2 (10 mL) was
stirred at room temperature for 8 h. The solvent was removed,
and the residue was washed twice with acetone (2 mL). The
white solid was dried in vacuo.
The other symmetrical dimers, 3b, 3c, and 3d , were
prepared similarly by method (ii) using the appropriate
monomeric precursors. The complex 3b was also prepared by
method (i) using cis-[Pt(p-MeC6H4)2(SMe2)2].
cis,cis-[P h 2P t(µ-SMe2)(µ-d p p m )P t(p-MeC6H4)2], 3e. A
mixture of cis-[PtPh2(SMe2)2] (62 mg, 0.13 mmol)] and [Pt(p-
MeC6H4)2(dppm)] (100 mg, 0.13 mmol) in CH2Cl2 was stirred
at room temperature for 8 h. The solvent was removed, and
the white residue was washed twice with acetone (2 mL) and
dried in vacuo.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. The 1H and 13C NMR spectra
were recorded on a Bruker Avance DPX 250 MHz spectrom-
eter. 31P NMR spectra were recorded on a Bruker Avance DRX
500 MHz NMR spectrometer. The 195Pt NMR spectrum was
obtained using a Varian XL-300 NMR spectrometer. Refer-
ences were TMS (1H and 13C), H3PO4 (31P), and aqueous
K2[PtCl4] (195Pt), and CDCl3 was used as solvent in all cases.
All the chemical shifts and coupling constants are in ppm and
Hz, respectively. cis-[PtPh2(SMe2)2], 1a , and the corresponding
dimeric complex [Pt2Ph4(SMe2)2] were made by the known
method.10 The following complexes were made similarly, except
that in each case the residue, before the final washing with
ether, was treated with SMe2 in CH2Cl2 in order to convert
the coexisting dimeric species into the monomer. cis-[Pt(m-
MeC6H4)2(SMe2)2], 1c: yield 68%; mp 152 °C dec. Anal. Calcd
for [Pt(m-MeC6H4)2(SMe2)2]: C, 43.1; H, 5.2. Found: C, 43.2;
A similar procedure using an equimolar mixture of [PtPh2-
(dppm)] and cis-[Pt(p-MeC6H4)2(SMe2)2] gave the same product.
The other unsymmetrical dimers, 3f-3j, were made simi-
larly using the appropriate mononuclear complexes.
Rea ction of cis,cis-[P h 2P t(µ-SMe2)(µ-d p p m )P tP h 2], 3a ,
w ith d p p m a n d SMe2. (i) A small sample (8 mg, 0.0065
3
H, 4.8. 1H NMR (CDCl3): δ 2.12 (s, J PtH ) 23.5 Hz, 12 H,
SMe2), 2.20 (s, 6 H, ArCH3). cis-[Pt(p-MeOC6H4)2(SMe2)2], 1d :
yield 58%; mp 143 °C dec. Anal. Calcd for [Pt(p-MeOC6H4)2-
(SMe2)2]: C, 40.5; H, 4.9. Found: C, 40.5; H, 4.9. 1H NMR
(11) Puddephatt, R. J .; Thomson, M. A. J . Organomet. Chem. 1982,
238, 231.
(12) Hassan, F. S.; McEwan, D. M.; Pringle, P. G.; Shaw, B. L. J .
Chem. Soc., Dalton Trans. 1985, 1501.
3
(CDCl3): δ 2.10 (s, J PtH ) 23.1 Hz, 12 H, SMe2), 3.68 (s, 6 H,
ArOCH3). cis-[Pt(p-MeC6H4)2(SMe2)2], 1b, was made by the
literature method.11

Aryldiplatinum(II) Complexes
Organometallics, Vol. 19, No. 14, 2000 2755
mmol) of 3a was dissolved in CDCl3 (0.3 mL) in a sealed NMR
tube, and dppm (2.5 mg, 0.0065 mmol) was added. Quantita-
tive conversion to [PtPh2(dppm)] and free SMe2 took place after
30 h at room temperature as checked by 31P and 1H NMR
spectroscopy. Evaporation of the solvent (even in the presence
of excess SMe2 in another run) gave [PtPh2(dppm)].
(ii) A small sample (ca. 5 mg) of 3a was dissolved in C6D6
(0.3 mL) in a sealed NMR tube, and a relatively large excess
of SMe2 was added. The sample gave an unchanged 31P NMR
spectrum after 24 h at room temperature. However, after the
sample was heated for 48 h at 50 °C, conversion to [PtPh2-
(dppm)] took place according to the 31P NMR spectrum. After
the solvent and the excess SMe2 were completely evaporated,
3a was re-formed along with trace amounts of [PtPh2(dppm)]
and cis-[PtPh2(SMe2)2].
mmol) of cis-[PtPh2(SMe2)2], 1a , was dissolved in CDCl3 (0.3
mL) in a sealed NMR tube, and dppm (4 mg, 0.011 mmol) was
added. An equimolar mixture of [PtPh2(dppm)] and cis-[PtPh2-
(SMe2)2] along with 2 equiv of SMe2 were immediately observed
in the 1H NMR spectrum. This mixture was gradually con-
verted to 3a in the solution. [Pt2Ph4(µ-SMe2)2] on reaction with
1 equiv of dppm behaved similarly.
Ack n ow led gm en t. We thank the Shiraz University
Research Council, Iran (Grant No. 73-SC-847-492) and
NSERC (Canada) for financial support and Professors
Banihashemi and Firouzabadi for their great help in
purchasing the 250 MHz NMR instrument for the
Shiraz University.
Rea ction of cis-[P tP h 2(SMe2)2] or [P t2P h 4(µ-SMe2)2]
w ith d p p m in a n NMR Tu be. A small sample (10 mg, 0.021
OM990784T