A comparison of binuclear dimethylplatinum(II) complexes with the bridging ligands X(PPh2)2, X = CH2 or NH

Article abstract of DOI:10.1039/b301419c

The reaction of [Pt2Me4(μ-SMe2)2], 1, with dppa = Ph2PNHPPh2 gave the complex [Pt2Me4(μ-SMe2)(μ-dppa)] and, with more dppa, a mixture of the binuclear complex [Pt2Me4(μ-dppa)2] and the mononuclear complex [PtMe2(dppa)]. In contrast, reaction of [Pt2Me4(μ-

Full text of DOI:10.1039/b301419c

View Article Online / Journal Homepage / Table of Contents for this issue
A comparison of binuclear dimethylplatinum(II) complexes with the
bridging ligands X(PPh2)2, X ؍ CH2 or NH
Sirous Jamali,a Mehdi Rashidi,a Michael C. Jenningsb and Richard J. Puddephatt*b
a Department of Chemistry, Shiraz University, Shiraz, Iran
b Department of Chemistry, University of Western Ontario, London, Canada N6A 5B7.
E-mail: pudd@uwo.ca
Received 5th February 2003, Accepted 26th March 2003
First published as an Advance Article on the web 28th April 2003
The reaction of [Pt2Me4(µ-SMe2)2], 1, with dppa = Ph2PNHPPh2 gave the complex [Pt2Me4(µ-SMe2)(µ-dppa)] and,
with more dppa, a mixture of the binuclear complex [Pt2Me4(µ-dppa)2] and the mononuclear complex [PtMe2(dppa)].
In contrast, reaction of [Pt2Me4(µ-SMe2)(µ-dppa)] with dppm = Ph2CH2PPh2 or of [Pt2Me4(µ-SMe2)(µ-dppm)] with
dppa gave only the binuclear complex [Pt2Me4(µ-dppm)(µ-dppa)]. This unusual complex, which has both bridging
dppm and dppa ligands in equivalent positions in an organometallic complex, is more inert to rearrangement to
mononuclear complexes, [PtMe2(dppm)] and [PtMe2(dppa)], than either symmetrical complex [Pt2Me4(µ-dppm)2] or
[Pt2Me4(µ-dppa)2]. A combination of structural and NMR evidence indicates that all binuclear dimethylplatinum()
complexes adopt a twist boat conformation, and the activation energy for fluxionality via a boat intermediate follows
the series [Pt2Me4(µ-dppm)2] >> [Pt2Me4(µ-dppm)(µ-dppa)] > [Pt2Me4(µ-dppa)2].
Introduction
The ligands X(PPh2)2 with X = CH2 (dppm), or NH (dppa) are
commonly used in stabilizing the types of binuclear organo-
transition metal complexes that have given insights into several
binuclear bond activation processes. These ligands are easy to
obtain and to use and, since their chelate complexes contain
strained 4-membered rings, they have a strong tendency to act
as bridging ligands. There are several reviews of the appli-
cations of both dppm1 and dppa2 in binuclear organometallic
and coordination chemistry, and the relative abilities of
these ligands to stabilize binuclear versus mononuclear com-
plexes has been much debated.3 Two ways to gain insight into
this subtle issue are to examine complexes in which there is an
equilibrium between monomer and dimer, and to compare
structures of pairs of complexes with the two ligands so that
the relative strain energies can be assessed. There are many
structures of complexes with bridging dppm and dppa ligands,
but there appear to be none in which there are bridging
dppm and dppa ligands in the same complex and in equivalent
bonding sites, though there are several complexes containing
Scheme 1
both ligands in inequivalent sites.1–3 For example, there is an
complex [Pt2Me4(µ-SMe2)2], 1,9 to the dppm bridged dimer
[Pt2Me4(µ-SMe2)(µ-dppm)], 2, was carried out as reported
earlier,10,11 and the analogous procedure using dppa gave the
complex [Pt2Me4(µ-SMe2)(µ-dppa)], 3. Complex 3 was fully
interesting cluster complex [Pd4(µ-Cl)2(µ-dppm)2(µ-dppa)2]2ϩ
,
having a rectangle of palladium atoms, in which the dppa
ligands span shorter edges with Pd–Pd = 2.61 Å, while dppm
ligands span the longer edges with Pd–Pd = 3.72 Å.3 The angles
PNP = 113.5Њ for dppa and PCP = 118.9Њ for dppm are
correspondingly smaller and larger, respectively, compared to
the free ligands, with free dppa having PNP = 118.9(2)Њ and
dppm having PCP = 106.2(3)Њ.4,5 This case is an exception to
the general rule that the angle PXP is greater in dppa (PNP)
than in dppm (PCP) complexes, with typical angles in the
region of 119 and 107Њ, close to the ideal trigonal and tetra-
hedral angles, respectively.1–8 This article reports new binuclear
dimethylplatinum() complexes with bridging dppa ligands,
including the complex [Pt2Me4(µ-dppm)(µ-dppa)], in which a
direct comparison of dppm and dppa in equivalent positions is
possible.
characterized by its H, 13C, 31P and 195Pt NMR spectra. The
1
presence of a single bridging diphosphine ligand was demon-
strated most simply by the 195Pt NMR spectrum, which
appeared as a doublet of doublets due to the couplings 1J(PtP)
= 2088 Hz and J(PtP) = 31 Hz. The presence of a bridging
dimethylsulfide ligand was shown by the appearance of the
3
1
MeS resonance in the H NMR spectra as a 1 : 8 : 18 : 8 : 1
quintet due to coupling to two adjacent 195Pt atoms with
3J(PtH) = 20 Hz.10 The two methylsulfur groups are effectively
equivalent by NMR. Finally there were two equal intensity
methylplatinum resonances in each of the H and 13C NMR
1
1
spectra; the coupling J(PtC) = 729 Hz for the methyl group
trans to sulfur was greater than the value 1J(PtC) = 640 Hz for
the methyl group trans to phosphorus, and the same trend was
observed for the proton resonances (see Experimental). These
couplings are strongly influenced by the trans ligand with trans-
influence of P > S. The detailed geometry was confirmed by a
structure determination, as shown in Fig. 1 and with selected
bond distances and angles in Table 1.
Results
Tetramethyldiplatinum complex chemistry
The synthetic chemistry for tetramethyldiplatinum() com-
plexes is outlined in Scheme 1. The conversion of the precursor
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 2 3 1 3 – 2 3 1 7
2313

View Article Online
Table 1 Selected bond distances (Å) and angles (Њ) for complex 3
Table 2 Selected bond distances (Å) and angles (Њ) for complex
4ؒCH2Cl2
Pt(1)–C(12)
Pt(1)–C(11)
Pt(1)–P(1)
Pt(1)–S(3)
P(1)–N(1)
2.073(6)
2.086(5)
2.276(1)
2.318(2)
1.706(5)
Pt(2)–C(22)
Pt(2)–C(21)
Pt(2)–P(2)
Pt(2)–S(3)
P(2)–N(1)
2.048(6)
2.094(5)
2.274(1)
2.341(1)
1.708(4)
Pt(1)–C(12)
Pt(1)–P(1)
Pt(2)–C(21)
Pt(2)–P(2)
P(1)–N(1)
P(3)–C(2)
2.09(1)
2.273(2)
2.11(1)
2.270(3)
1.727(8)
1.800(8)
Pt(1)–C(11)
Pt(1)–P(3)
Pt(2)–C(22)
Pt(2)–P(4)
P(2)–N(1)
P(4)–C(2)
2.107(9)
2.290(2)
2.11(1)
2.291(2)
1.731(8)
1.816(8)
C(12)–Pt(1)–C(11)
C(12)–Pt(1)–P(1)
C(11)–Pt(1)–P(1)
C(12)–Pt(1)–S(3)
C(11)–Pt(1)–S(3)
P(1)–Pt(1)–S(3)
N(1)–P(1)–Pt(1)
Pt(1)–S(3)–Pt(2)
83.4(2)
88.8(2)
172.1(2)
175.1(2)
92.9(2)
94.82(5)
121.5(1)
99.87(5)
C(22)–Pt(2)–C(21)
C(22)–Pt(2)–P(2)
C(21)–Pt(2)–P(2)
C(22)–Pt(2)–S(3)
C(21)–Pt(2)–S(3)
P(2)–Pt(2)–S(3)
N(1)–P(2)–Pt(2)
P(1)–N(1)–P(2)
84.8(3)
93.4(2)
177.7(2)
172.1(2)
88.9(2)
92.74(5)
112.3(2)
127.4(3)
C(12)–Pt(1)–C(11)
C(11)–Pt(1)–P(3)
C(21)–Pt(2)–C(22)
C(21)–Pt(2)–P(4)
N(1)–P(1)–Pt(1)
N(1)–P(2)–Pt(2)
P(1)–N(1)–P(2)
83.2(4)
87.8(3)
81.1(4)
91.9(3)
115.0(3)
123.0(3)
126.6(5)
C(12)–Pt(1)–P(1)
P(1)–Pt(1)–P(3)
C(22)–Pt(2)–P(2)
P(2)–Pt(2)–P(4)
C(2)–P(3)–Pt(1)
C(2)–P(4)–Pt(2)
P(3)–C(2)–P(4)
90.0(3)
99.21(8)
88.4(3)
98.35(9)
121.5(3)
120.7(3)
123.5(5)
Fig. 2 A view of the structure of complex 4, emphasizing the twist-
boat conformation. Only the ipso-carbon atoms of the phenyl rings are
shown, for clarity.
Fig. 1 A view of the structure of complex 3.
The platinum atoms are present in a 6-membered ring defined
by the atoms Pt(1)S(3)Pt(2)P(2)N(1)P(1), of which all but the
sulfur atom are roughly coplanar. Each platinum atom has
distorted square planar stereochemistry with cis-PtMe2PS
coordination. The geometry of the bridging dimethylsulfide
ligand in 3 [PtS = 2.318(2), 2.341(1) Å, PtSPt = 99.87(5)Њ] is
similar to that in [Pt2Me4(µ-SMe2)2], 1 [PtS = 2.354(3) Å, PtSPt
= 100.3(1)Њ], and the non-bonding Pt ؒ ؒ ؒ Pt distances are also
similar [3.566 and 3.615 Å in 3 and 1, respectively].9 For the
dppa ligand in 3, the bite separation P1 ؒ ؒ ؒ P2 = 3.06 Å is
shorter than the separation Pt1 ؒ ؒ ؒ Pt2 = 3.566 Å, and the
angles PNP = 127.4(3) and NPPt = 121.5(1), 112.3(2)Њ are all
greater than tetrahedral in order to accommodate this differ-
ence. The distances P–N = 1.706(5), 1.708(4) Å are similar to
the distance in the free ligand [1.692(2) Å].4
The complex [Pt2Me4(µ-dppm)(µ-dppa)], 4, was prepared in
good yield either by reaction of complex 3 with dppm or by
reaction of 2 with dppa (Scheme 1). The complex is thermally
stable in solution even in boiling benzene and it does not dis-
proportionate to give the symmetrical complexes [Pt2Me4-
(µ-dppm)2] and [Pt2Me4(µ-dppa)2]. The complex [Pt2Me4-
(µ-dppm)2] is known to rearrange quantitatively to give the
monomer [PtMe2(dppm)] on heating to 60 ЊC in benzene
solution, containing dimethylsulfide as catalyst, for two days.7
Under the same conditions, complex 4 showed no detect-
able reaction, though on heating to 100 ЊC in a sealed NMR
tube about 5% conversion to a mixture of the monomers
[PtMe2(dppm)] and [PtMe2(dppa)] occurred in two hours.
Complex 4 is thus more inert to rearrangement to the mono-
mers than is the symmetrical complex [Pt2Me4(µ-dppm)2]. The
structure of complex 4 was determined and is shown in Fig. 2,
with selected bond parameters listed in Table 2. The conform-
ation of the complex can be described as a twist-boat, in which
two square planar cis-dimethylplatinum() units are bridged
by the dppm and dppa ligands. This conformation is similar
to that found in [Pt2Me4(µ-dppm)2], but different from the
extended chair conformation found in [Pt2Me4(µ-dmpm)2],
dmpm = dppm = Me2CH2PMe2.7 The conformation can be
defined by the torsion angles in the 8-membered ring. For the
twist-boat conformation of cyclooctane there are two torsion
angles of 38 and 65Њ, while for [Pt2Me4(µ-dppm)2] the torsion
angles cluster around values of 22(1) and 73(1)Њ.7 The corre-
sponding torsion angles for complex 4 are 18(3) and 74(4)Њ, but
with a considerably greater range of torsion angles than in
[Pt2Me4(µ-dppm)2], as a result of the different bridging ligands.
The structure for 4 is thus more distorted. The bite distances of
the diphosphine ligands [3.088 Å for dppa, 3.186 Å for dppm]
and the Pt ؒ ؒ ؒ Pt separation [4.440 Å] in 4 are also similar
to those in [Pt2Me4(µ-dppm)2], which has P ؒ ؒ ؒ P = 3.18 and
3.20 Å and Pt ؒ ؒ ؒ Pt = 4.198 Å.7 In the structure of 4 there was
disorder of some of the phenyl groups that was resolved. Dis-
order of the dppm and dppa ligands might be expected, given
their similar steric profiles. The bridging N and C atoms were
placed based on the better fit with the electron densities, and no
disorder was resolved, but it is possible that some unresolved
disorder might be present. With the assignment given, the dis-
tances in the PNP group with P–N = 1.727(8) and 1.731(8) Å
are shorter than the distances in the PCP group of dppm with
P–C = 1.800(8) and 1.816(8) Å, consistent with the trend in the
free ligands dppa and dppm in which have mean P–N = 1.692(2)
Å and P–C = 1.858(5) Å, respectively.4 The angle PNP =
126.6(5)Њ is slightly greater than the angle PCP = 123.5(5)Њ, as
D a l t o n T r a n s . , 2 0 0 3 , 2 3 1 3 – 2 3 1 7
2314

View Article Online
expected, but the PCP angle is greater than those for [Pt2Me4-
(µ-dppm)2] of 120(2) and 117(2)Њ.7 The two angles NPPt =
115.0(3) and 123.0(3) of dppa are significantly different
whereas the analogous angles CPPt = 121.5(3) and 120.7(3)Њ are
similar, but all of these angles at phosphorus are greater than
the ideal tetrahedral angle. These angles are an indication of
strain in the complex, perhaps arising from the different pre-
ferred geometries of the two bridging ligands. There was no
evidence of strong intermolecular interactions in the lattice that
might affect the conformation.
Complex 4 was fluxional, as shown by the variable temper-
ature NMR spectra. At room temperature, there was a single
resonance in the 31P NMR spectrum for each of the dppm and
dppa ligands, but the resonance for the dppa phosphorus atoms
was broad (Fig. 3). At lower temperature, the dppa resonance
broadened further then split into two resonances at δ(31P) = 45.8
[1J(PtP) = 2078 Hz] and 69.0 [1J(PtP) = 2064 Hz], and then the
dppm resonance also broadened and split into two resonances
at δ(31P) = 10.4 [1J(PtP) = 1940 Hz] and 12.1 [1J(PtP) = 1742 Hz].
These spectra are readily interpreted in terms of the fluxional
process shown in eqn. (1), in which two twist-boat conformers
equilibrate through an intermediate boat conformer. In addi-
tion, since 31P chemical shifts are strongly influenced by distor-
tions of the angles at phosphorus,12 the larger difference in 31P
chemical shifts for the dppa phosphorus atoms is fully consist-
ent with the solid state structure discussed above, showing
greater differences in angles at the two phosphorus atoms of
dppa, and suggests that this structure is a good approximation
of the ground state solution structure. The activation energy
for the fluxional process of eqn. (1) was calculated to be ∆G* =
the mixture did not change in solution at room temperature but
different syntheses gave varying ratios of products 5 and 6. It
was not possible to separate the mixture by recrystallization
and so the compounds were characterized as the isomeric mix-
ture. When a mixture of 5 and 6 in C6D6 was heated to 70 ЊC for
one hour in the presence of dimethylsulfide as catalyst, com-
plete conversion to the monomer 6 was observed, as monitored
by NMR, and so it is clear that 6 is the thermodynamically
stable form. Each complex 5 and 6 gave a single methylplatinum
resonance and a single NH resonance in the 1H NMR spectrum
(Fig. 4). There was a particularly large difference in chemical
shifts and coupling constants to the platinum of the NH reson-
ances as seen in Fig. 4. This resonance for complex 5 appeared
as a 1 : 8 : 18 : 8 : 1 quintet, at δ = 3.11 with 3J(PtH) = 21 Hz, as a
result of coupling to two platinum centers. For complex 6, the
NH resonance was at δ = 5.56 with a much larger coupling
constant 3J(PtH) = 63 Hz; it appeared as a triplet as a result of
2
coupling to phosphorus with J(PH) = 9 Hz and the pattern
arising from coupling to 195Pt was a 1 : 4 : 1 triplet as expected
for coupling to a single platinum atom. Fig. 5 illustrates the
single resonance for each complex in the 31P NMR spectrum at
room temperature. The spectra for 5 are broader than for 6, as a
result of fluxionality similar to that described above for the
binuclear complexes 4 and [Pt2Me4(µ-dppm)2], and the reson-
ance is split in the spectrum shown at Ϫ70 ЊC (Fig. 5). The
activation energy for fluxionality was ∆G* = 40.7(2) kJ molϪ1
which is slightly lower than that for complex 4 of 42.1(1) kJ
molϪ1
,
.
(1)
42.1(1) kJ molϪ1 from the coalescence of the dppm resonances
at 223 K or the dppa resonances at 249 K. The activation
energy is markedly lower than for the similar fluxional process
in [Pt2Me4(µ-dppm)2] for which ∆G* = 54.7(4) kJ molϪ1 at
283 K.7
1
Fig. 4 Characterization of the mixture of complexes 5 and 6 by H
NMR spectroscopy at 20 ЊC. Note the difference in chemical shifts of
the NH protons and the different intensities and coupling constants
associated with the 195Pt satellite spectra.
The mixture of complexes 5 and 6 was thermally stable but
slow hydrolysis occurred in moist solvent. Thus, when a
solution containing a mixture of complexes 5 and 6 in benzene
was exposed to moist air, crystals of the insoluble complex
[PtMe(dppa)(PPh2O)], 7,13 slowly deposited.
Discussion
This work has shown that the ligands dppm and dppa have
similar bridging versus chelating properties in the complexes
[Pt2Me4(µ-dppm)2] and [Pt2Me4(µ-dppa)2], despite the differ-
ences in structure and bonding of the free ligands. Thus both
complexes rearrange to the respective monomers on heating
at 60–80 ЊC in benzene solution with dimethyl sulfide as
catalyst. Curiously, the mixed ligand complex [Pt2Me4(µ-dppm)-
(µ-dppa)] was less reactive to rearrangement to [PtMe2(dppm)]
Fig. 3 Variable temperature 31P NMR spectra of complex 4, showing
that at low temperature all phosphorus atoms are non-equivalent.
The reaction of complex 1 with two equivalents of dppa or
of complex 3 with one equivalent of dppa gave a mixture of the
binuclear complex [Pt2Me4(µ-dppa)2], 5, and the mononuclear
complex [PtMe2(dppa)], 6. Once formed, the composition of
D a l t o n T r a n s . , 2 0 0 3 , 2 3 1 3 – 2 3 1 7
2315

View Article Online
2
3J(PtP) = 31 Hz, J(PP) = 47 Hz, dppa]; δ(195Pt) = Ϫ4388 [dd,
1J(PtP) = 2088 Hz, 3J(PtP) = 31 Hz, Pt].
cis,cis-[Pt2Me4(ꢀ-dppm)(ꢀ-dppa)], 4
A mixture of cis,cis-[Pt2Me4(µ-SMe2)(µ-dppa)], 3, (150 mg,
0.167 mmol) and dppm (65 mg, 0.167 mmol) in C6H6 (20 mL)
was stirred for 1 h. The solvent was removed and the product
was washed with MeOH ( 2 × 2 mL) and dried under vacuum.
Yield: 84%; mp 205–208 ЊC. Anal. Calcd. for C53H55NP4Pt2: C,
52.2; H, 4.5; N, 1.1. Found: C, 52.5; H, 4.7; N, 0.7%. The syn-
thesis of 4 was also carried out by reaction of cis,cis-[Pt2Me4-
(µ-SMe2)(µ-dppm)], 2, and dppa in a similar way. NMR in
CD2Cl2 at 20 ЊC: δ(1H) = 0.11 [m, 6H, 2J(PtH) = 69 Hz, 3J(PH) =
17 Hz, Me trans to dppm]; 0.27 [m, 6H, 2J(PtH) = 68 Hz, 3J(PH)
= 16 Hz, Me trans to dppa]; 3.50 [br m, 2H, CH2P2 of dppm];
3
2
3.70 [t, 1H, J(PtH) = 27 Hz, J(PH) = 8 Hz, NH of dppa];
δ(13C) = 9.4 [m, J(PC) = 100 Hz, Me trans to dppm]; 9.7 [m,
2
2J(PC) = 112 Hz, Me trans to dppa]; 26.2 [t, J(PC) = 15 Hz,
1
CH2P2 of dppm]; δ(31P) = 11.9 [m, 1J(PtP) = 1832 Hz, 3J(PtP) =
2
1
38 Hz, J(PP) = 15 Hz, dppm]; 58.7 [br m, J(PtP) = 2070 Hz,
dppa]. NMR in CD2Cl2 at Ϫ70 ЊC: δ(1H) = Ϫ0.4 [m, 3H, Me];
0.0 [m, 3H, Me]; 0.9 [m, 6H, Me]; 2.3 [m, 1H, CH2P2 of dppm];
4.0 [m, 1H, 3J(PtH) = 25 Hz, NH of dppa]; 4.4 [m, 1H, 3J(PtH)
= 36 Hz, J(HH) = 12 Hz, CH2P2 of dppm]; δ(31P) = 10.4 [m,
2
1J(PtP) = 1940 Hz, dppm]; 12.1 [m, 1J(PtP) = 1742 Hz, dppm];
45.8 [m, 1J(PtP) = 2078 Hz, dppa]; 69.0 [m, 1J(PtP) = 2064 Hz,
dppa].
cis,cis-[Pt2Me4(ꢀ-dppa)2], 5, and [PtMe2(dppa)], 6
A mixture of cis,cis-[Pt2Me4(µ-SMe2)(µ-dppa)], 3, (30 mg, 0.033
mmol) and dppa (13 mg, 0.033 mmol) in C6H6 (5 mL) was
stirred for 1 h. The solvent was removed and the product, iden-
tified as a mixture of complexes 5 and 6 in a roughly 1 : 2 molar
ratio, was washed with MeOH ( 2 × 1 mL) and dried under
vacuum. Yield: 86%. Anal. Calcd. for C26H27NP2Pt: C, 51.1; H,
4.4; N, 2.3. Found: C, 51.2; H, 4.4; N, 2.1%. A similar mixture
of “isomers” was obtained by reaction of complex 1 with 2
equivalents of dppa. NMR in CD2Cl2 at 20 ЊC: 5; δ(1H) = 0.08
[m, 12H, 2J(PtH) = 67 Hz, MePt]; 3.11 [s, 2H, 3J(PtH) = 21 Hz,
NH of dppa]; δ(13C) = 9.9 [m, 2J(PC) = 105 Hz, MePt]; δ(31P) =
62.1 [s, 1J(PtP) = 2075 Hz, dppa]; 6; δ(1H) = 0.82 [m, 6H,
Fig. 5 The 31PNMR spectra of a mixture of complexes 5 and 6,
illustrating the fluxionality of the binuclear complex 5: (a) spectrum at
20 ЊC; (b) spectrum at Ϫ70 ЊC.
and [PtMe2(dppa)] than either symmetrical complex; it reacted
only slowly at 100 ЊC. The differences appear to be largely
kinetic in nature and the chelate monomer is the thermo-
dynamically stable form in solution in each case. All three
binuclear complexes adopt a twist-boat conformation and the
activation energy for fluxionality by way of a boat (or saddle)
intermediate followed the series [Pt2Me4(µ-dppm)2] >> [Pt2Me4-
(µ-dppm)(µ-dppa)] > [Pt2Me4(µ-dppa)2], illustrating that there
is a significant difference in conformational mobility between
bridging dppm and dppa ligands.
2
3
2J(PtH) = 74 Hz, MePt]; 5.56 [t, 1H, J(PH) = 9 Hz, J(PtH) =
2
63 Hz, NH of dppa]; δ(13C) = Ϫ2.3 [m, J(PC) = 107, 8 Hz,
1
1J(PtC) = 632 Hz, MePt]; δ(31P) = 30.4 [s, J(PtP) = 1475 Hz,
1
dppa]. NMR at Ϫ70 ЊC: 5; δ(31P) = 53.0 [s, J(PtP) = 2135 Hz,
dppa]; 68.7 [s, 1J(PtP) = 2012 Hz, dppa].
Experimental
When a mixture of 5 and 6 (15 mg) in C6D6 (0.4 mL) was
heated in a sealed NMR tube at 70 ЊC for 1 h, complete conver-
sion to 6 occurred as determined by NMR spectroscopy.
1H, 13C and 31P NMR spectra were recorded as solutions in
CD2Cl2 by using Varian Mercury 400 or Inova 400 spectro-
meters, while the 195Pt NMR spectrum was recorded using a
Bruker Avance DRX 500 MHz spectrometer. The spectra are
referenced with respect to TMS (1H, 13C), H3PO4 (31P) or aque-
ous K2[PtCl4] (195Pt). The complexes [Pt2Me4(µ-SMe2)2] and
cis,cis-[Pt2Me4(µ-SMe2)(µ-dppm)] were prepared by the liter-
ature methods.9,10
[PtMe(dppa)(PPh2O)], 7
A solution containing a mixture of complexes 5 and 6 in ben-
zene was allowed to evaporate slowly. Decomposition occurred
slowly to give crystals of the product 7. Yield: ca. 20%; mp 208–
210 ЊC (decomp.). Anal. Calcd. for C37H34NOP3Pt: C, 55.8; H,
4.3; N, 1.8. Found: C, 55.1; H, 4.4; N, 1.9%. The complex was
insufficiently soluble to allow NMR characterization.
cis,cis-[Pt2Me4(ꢀ-SMe2)(ꢀ-dppa)], 3
A solution of [Pt2Me4(µ-SMe2)2] (1.00 g, 1.73 mmol) and dppa
(0.700 g, 1.73 mmol) in C6H6 (100 mL) was stirred for 1 h. The
solvent was removed and the product was washed with MeOH
(2 × 5 mL) and dried under vacuum. Yield: 90%; mp 166–168
ЊC. Anal. Calcd. for C30H39NP2Pt2S: C, 40.1; H, 4.3; N, 1.6.
Found: C, 39.7; H, 4.6; N, 1.5%. NMR in CD2Cl2: δ(1H) = 0.11
[m, 6H, 2J(PtH) = 85 Hz, 3J(PH) = 10 Hz, Me trans to S]; 0.26
[m, 6H, 2J(PtH) = 57 Hz, 3J(PH) = 8 Hz, Me trans to P]; 2.56 [s,
Structure determinations
Crystals were grown from CH2Cl2/hexane, and were mounted
on glass fibres. Data were collected by using a Nonius Kappa-
CCD diffractometer with COLLECT (Nonius B.V., 1998). The
unit cell parameters were calculated and refined from the full
data set. Crystal cell refinement and data reduction were carried
out using DENZO (Nonius B.V., 1998). The data were scaled
using SCALEPACK (Nonius B.V., 1998). The SHELXTL-NT
V5.1 (Sheldrick, G.M.) suite of programs was used to solve the
structure by direct methods.14 The non-hydrogen atoms were
3
3
6H, J(PtH) = 20 Hz, SMe2]; 3.10 [m, 1H, J(PtH) = 28 Hz,
2J(PH) = 8 Hz, NH]; δ(13C) = 0.0 [s, 1J(PtC) = 729 Hz, Me trans
to S]; 11.5 [d, 1J(PtC) = 640 Hz, 2J(PC) = 111 Hz, Me trans to P];
31.2 [s, 2J(PtC) = 6 Hz, MeS]; δ(31P) = 63.9 [s, 1J(PtP) = 2088 Hz,
D a l t o n T r a n s . , 2 0 0 3 , 2 3 1 3 – 2 3 1 7
2316

View Article Online
Table 3 Crystal data and structure refinement
MR thanks the Iranian Ministry of Science, Research and
Technology (Motemarkez Grant No. 80-SC-2-RM) for
financial support.
Complex
3
4ؒCH2Cl2
Formula
C30H39NP2Pt2S
897.80
200(2)
Orthorhombic
Pbca
21.9630(2)
17.7423(2)
15.5770(1)
90
C54H57Cl2NP4Pt2
1304.97
200(2)
Monoclinic
P21/c
14.0637(2)
16.9276(2)
22.1155(3)
105.437(1)
5075.0(1)
4
Formula weight
Temperature/K
Crystal system
Space group
a/Å
b/Å
c/Å
References
1 (a) R. J. Puddephatt, Chem. Soc. Rev., 1983, 99; (b) B. Chaudret,
B. Delavaux and R. Poilblanc, Coord. Chem. Rev., 1988, 86, 191.
2 (a) M. Witt and H. W. Roesky, Chem. Rev., 1994, 94, 1163;
(b) M. S. Balakrishna, S. V. Reddy, S. S. Krishnamurthy, J. F. Nixon
and J. C. T. R. Burkett St Laurent, Coord. Chem. Rev., 1994, 129, 1;
(c) P. Bhattacharyya and D. J. Woollins, Polyhedron, 1995, 14, 3367.
3 I. Bachert, P. Braunstein, M. K. McCart, F. Fabrizi de Biani,
F. Laschi, P. Zanello, G. Kickelbick and U. Schubert, J. Organomet.
Chem., 1999, 573, 47.
β/Њ
Volume/Å3
Z
6069.9(1)
8
9.403
µ/mmϪ1
5.775
4 H. Noth and E. Meinel, Z. Anorg. Allg. Chem., 1967, 349, 744.
5 I. Bachert, P. Braunstein, E. Guillon, C. Massera, J. Rose,
A. DeCian and J. Fischer, J. Cluster Sci., 1999, 10, 445.
6 (a) C. S. Browning, R. A. Burrow, D. H. Farrar and H. A. Mirza,
Inorg. Chim. Acta, 1998, 271, 112; (b) C. S. Browning and
D. H. Farrar, J. Chem. Soc., Dalton Trans., 1995, 521.
7 Lj. Manojlovic-Muir, K. W. Muir, A. A. Frew, S. S. M. Ling,
M. A. Thomson and R. J. Puddephatt, Organometallics, 1984, 3,
1637.
8 J. Geicke, I. P. Lorenz, M. Engel and K. Polborn, Inorg. Chim. Acta,
1998, 269, 157.
9 (a) D. Song and S. Wang, J. Organomet. Chem., 2001, 648, 302;
(b) J. D. Scott and R. J. Puddephatt, Organometallics, 1983, 2,
1643; (c) G. S. Hill, M. J. Irwin, C. J. Levy, L. M. Rendina and
R. J. Puddephatt, Inorg. Synth., 1998, 32, 149.
10 M. Rashidi, S. Jamali and M. Hashemi, J. Organomet. Chem., 2001,
633, 105.
11 M. Rashidi, M. Hashemi, M. Khorasani-Motlagh and R. J.
Puddephatt, Organometallics, 2000, 19, 2751.
12 A. J. Carty, in Catalytic Aspects of Metal Phosphine Complexes,
Am. Chem. Soc. Adv. Chem. Ser., ed. E. C. Alyea and D. W. Meek,
ACS, Washington, 1982, vol. 196, p. 163.
13 M. Rashidi, M. C. Jennings and R. J. Puddephatt, CrystEngComm,
2003, 5, 65.
Data/restr./param.
R1 [I > 2σ(I )]
wR2 [I > 2σ(I )]
8875/0/277
0.0415
0.0887
11636/0/268
0.0601
0.1127
refined with anisotropic thermal parameters, with the exception
of the phenyl carbon atoms for complex 4, some of which
were disordered. The hydrogen atom positions were calculated
geometrically and were included as riding on their respective
carbon atoms.
Complex 4 contained a well-ordered solvate molecule of
CH2Cl2, but there was disorder in three of the phenyl rings and
they were modeled as 50/50, 60/40 and 60/40 mixtures. Details
of the crystal data and structure refinement for the complexes
are given in Table 3.
CCDC reference numbers 203234–203235.
See http://www.rsc.org/suppdata/dt/b3/b301419c/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
RJP thanks the NSERC (Canada) for financial support and
the Government of Canada for a Canada Research Chair.
14 (a) G. M. Sheldrick, Universität Göttingen, 1998; (b) B. V. Nonius,
Eindhoven, 1998.
D a l t o n T r a n s . , 2 0 0 3 , 2 3 1 3 – 2 3 1 7
2317