Quantifying the trans influence of triphenylarsine. Crystal and molecular structures of cis-[PtCl2(SMe2)(AsPh3)] and cis-[PtCl2(AsPh3)2]·CHCl3

Article abstract of DOI:10.1016/S0020-1693(01)00785-X

Reaction between a mixture of cis-trans-[PtCl₂(SMe₂)₂] and 1 equiv. AsPh₃ in chloroform gives cis-[PtCl₂(SMe₂)(AsPh₃)] crystallizing in P2₁/n with a = 10.397(2), b = 14.876(3), c = 13.956(3) ?, β = 90.86(3)° and Z = 4. Selected geometrical parameters are Pt-As 2.3531(10), Pt-S 2.262(2), Pt-Cl (trans to S) 2.301(2), Pt-Cl (trans to As) 2.328(2) ? and S-Pt-As 88.85(6), S-Pt-Cl(2) 90.77(8), As-Pt-Cl(1) 91.07(6) and Cl-Pt-Cl 89.42(7)°. cis-[PtCl₂(AsPh₃)₂]·CHCl₃ crystallizes in P2₁/c with a = 20.557(4), b = 9.5951(19), c = 20.147(4) ?, β = 96.77(3)° and Z = 4. Selected geometrical parameters are Pt-As(1) 2.3599(9), Pt-As(2) 2.3770(9), Pt-Cl(1) (trans to As(1)) 2.3515(18), Pt-Cl(2) (trans to As(2)) 2.3251(18) ? and As-Pt-As 97.87(3), As(1)-Pt-Cl(2) 88.67(5), As(2)-Pt-Cl(1) 84.30(5) and Cl-Pt-Cl 89.32(7)°. By comparison with related structures from the literature the following trans influence series was established PMe₂Ph > PPh₃ > AsPh₃ ≈ SbPh₃ > Me₂SO ≈ SMe₂ ≈ SPh₂ > NH₃ ≈ olefin > Cl^- > MeCN.

Full text of DOI:10.1016/S0020-1693(01)00785-X

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Inorganica Chimica Acta 329 (2002) 135–140
Note
Quantifying the trans influence of triphenylarsine. Crystal and
molecular structures of cis-[PtCl2(SMe2)(AsPh3)] and
cis-[PtCl2(AsPh3)2]·CHCl3
Stefanus Otto 1*, Maria H. Johansson
Inorganic Chemistry 1, Center for Chemistry and Chemical Engineering, Lund Uni6ersity, PO Box 124, S-221 00 Lund, Sweden
Received 20 July 2001; accepted 5 October 2001
Abstract
Reaction between a mixture of cis–trans-[PtCl2(SMe2)2] and 1 equiv. AsPh3 in chloroform gives cis-[PtCl2(SMe2)(AsPh3)]
,
crystallizing in P21/n with a=10.397(2), b=14.876(3), c=13.956(3) A, i=90.86(3)° and Z=4. Selected geometrical parameters
,
are PtꢀAs 2.3531(10), PtꢀS 2.262(2), PtꢀCl (trans to S) 2.301(2), PtꢀCl (trans to As) 2.328(2) A and SꢀPtꢀAs 88.85(6), SꢀPtꢀCl(2)
90.77(8), AsꢀPtꢀCl(1) 91.07(6) and ClꢀPtꢀCl 89.42(7)°. cis-[PtCl2(AsPh3)2]·CHCl3 crystallizes in P21/c with a=20.557(4),
,
b=9.5951(19), c=20.147(4) A, i=96.77(3)° and Z=4. Selected geometrical parameters are PtꢀAs(1) 2.3599(9), PtꢀAs(2)
,
2.3770(9), PtꢀCl(1) (trans to As(1)) 2.3515(18), PtꢀCl(2) (trans to As(2)) 2.3251(18) A and AsꢀPtꢀAs 97.87(3), As(1)ꢀPtꢀCl(2)
88.67(5), As(2)ꢀPtꢀCl(1) 84.30(5) and ClꢀPtꢀCl 89.32(7)°. By comparison with related structures from the literature the following
trans influence series was established PMe2Ph\PPh3\AsPh3:SbPh3\Me2SO:SMe2:SPh2\NH3:olefin\Cl−\MeCN.
© 2001 Elsevier Science B.V. All rights reserved.
Keywords: Triphenylarsine; Platinum; Trans influence; Crystal structures
1. Introduction
Ligands exerting a high trans effect due to their p
bonding properties only show a moderate trans influ-
ence while ground state labilization is directly linked to
a large trans influence and is thus in essence a measure
of the s bonding properties of a ligand.
Several ways of quantifying the trans influence of
ligands are used today, amongst others IR- and NMR
spectroscopy and X-ray crystallography. Probably the
most generally accepted criterium is comparison of
bond distances obtained from a series of related crystal
structure determinations.
Although the chemistry of phosphine ligands have
been extensively studied, including numerous crystallo-
graphic investigations to aid in our understanding of
their chemical properties, the solid state chemistry of
arsine and stibine ligands have received very limited
interest. In order to determine the trans influence of a
ligand the bond distances trans to these ligands, typi-
cally to a chloride, is compared for a related series of
complexes such as [PtCl3(L)]− or cis-[PtCl2(L)2] (L=
neutral ligand). The cis influence could in principle be
determined from complexes such as trans-[PtCl2(L)2],
It is important to distinguish between the terms trans
effect and trans influence. The trans effect is defined as
the ability of a certain ligand to labilize the substitution
of the ligand trans to itself, i.e. it is concerned with the
reactivity of the complex and is thus a kinetic effect
dependant on the energy difference between the
ground- and transition states. The trans influence on
the other hand is a measure of the extent to which a
ligand is able to weaken the coordinating ability of the
ligand trans to itself and is thus only concerned with the
ground state of the complex. Furthermore the high
trans effect of certain ligands can be attributed to either
ground state labilization as in the case of s binding
ligands [1] such as H− and CH−3 , or by transition state
stabilization for p bonding ligands [2] such as C2H4.
* Corresponding author. Tel.: +46-46-2228 116; fax: +46-46-
2224 439.
E-mail address: stefanus.otto@inorg.lu.se (S. Otto).
1 On leave from the Department of Chemistry, University of the
Free State, Bloemfontein 9300, South Africa.
0020-1693/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00785-X

136
S. Otto, M.H. Johansson / Inorganica Chimica Acta 329 (2002) 135–140
but as it is much less pronounced than the trans influ-
ence crystallographically determined bond distances are
normally not discriminative enough to make clear-cut
conclusions possible.
2. Experimental
2.1. Preparation of complexes
The first crystal structures of cis- and trans-platinu-
m(II)bisstibine complexes were only reported [3–5] re-
cently, while the known platinum(II)bisarsine com-
plexes are limited to complexes with a trans geometry
[6]. In this paper we report the crystal structures of
cis-[PtCl2(SMe2)(AsPh3)] (1) and cis-[PtCl2(AsPh3)2]·
CHCl3 (2) in order to quantify the trans influence of
AsPh3.
All solvents and chemicals used for the preparation
of the complexes were of reagent grade and were used
without further purification. All preparations were car-
ried out under aerobic conditions and no special pre-
cautions were taken to exclude atmospheric moisture.
The starting complex cis–trans-[PtCl2(SMe2)2] and cis-
[PtCl2(AsPh3)2] were prepared according to literature
procedures [7,8], spectroscopic data were consistent
with that reported. White plates of 2, were grown by
slow evaporation of a chloroform solution of cis-
[PtCl2(AsPh3)2].
Table 1
2.1.1. cis-[PtCl2(SMe2)(AsPh3)] (1)
Experimental details, crystal data and refinement parameters for 1
and 2
AsPh3 (40 mg, 0.131 mmol) in chloroform was added
to a chloroform solution of cis–trans-[PtCl2(SMe2)2]
(50 mg, 0.128 mmol). Slow evaporation of the reaction
mixture yielded yellow crystals of 1 suitable for X-ray
analysis.
a
1
2 b
Chemical formula
PtCl2[S(CH3)2]-
[As(C6H5)3]
634.34
monoclinic
P21/n
PtCl2[As(C6H5)3]2·
CHCl3
997.80
monoclinic
P21/c
1H NMR (CDCl3): 2.45 (6H, t, JPtꢀH=48); 7.4–7.5
3
Chemical formula weight
Crystal system
Space group
(9H, m); 7.6–7.7 (6H, m).
,
a (A)
10.397(2)
14.876(3)
13.956(3)
90.86(3)
2158.3(8)
4
20.557(4)
9.5951(19)
20.147(4)
96.77(3)
3946.2(14)
4
2.2. X-ray measurements and structure determinations
,
b (A)
,
c (A)
i (°)
V (A )
The data collections were performed at 293(1) K on
a Bruker Smart diffractometer equipped with a rotating
3
,
Z
,
anode, Mo Ka (u=0.71073 A) radiation. The intensi-
Dx (g cm−3
)
1.952
1.679
ties were merged and integrated using SAINT [9] and
corrected for Lorentz polarization (Lp) and absorption
effects with SADABS [10]. The structures were solved by
Patterson and difference Fourier methods and refined
by full-matrix least-squares calculations using the
SHELXS97 and SHELXL97 programs [11] with S(Fo2−
Fc2)2 being minimized. All non-hydrogen atoms were
refined anisotropically and the hydrogen atom positions
were calculated as riding on the adjacent carbon atom
Number of reflections for
cell parameters
4773
5629
q Range (°)
2.38–25.07
8.368
1208
0.19×0.30×0.42 0.10×0.15×0.20
0.085/0.160
23686
2.5–25.01
5.583
1928
v (mm−1
F(000)
)
Crystal size (mm)
min/Tmax
T
0.420/0.525
31929
12002 (0.0572)
8316
Collected reflections
Unique reflections (Rint
Observed reflections
(I\2|(I))
)
6734 (0.0947)
3546
,
,
(aromatic CꢀH=0.93 A, methyl CꢀH=0.96 A) and
refined with an overall thermal parameter. The graphics
were done with DIAMOND 2.0 [12].
Range of h, k, l
−14“h“15
−21“k“20
−13“l“20
2.00–31.86
0.0499
0.0966
0.1271
0.1146
0.922
−29“h“29
−13“k“9
−25“l“28
2.00–31.56
0.0573
0.1103
0.0979
0.1277
1.135
q Range (°)
R1 [F2\2|(F2)] c
wR2 (F2) d
R1 (all data)
wR2 (all data)
S
3. Results and discussion
3.1. Crystallography
Data/restraints/parameters 6734/0/229
Extinction coefficient
12002/1/470
0.00097(8)
0.003
(D/|)max
Dzmax/Dzmin (e A
0.000
2.36/−1.45
Details of the data collection and refinement parame-
ters are summarized in Table 1. The thermal displace-
ment ellipsoids and numbering schemes for 1 and 2 are
given in Figs. 1 and 3, packing diagrams in Figs. 2 and
4 and selected geometrical parameters in Tables 2 and
3, respectively.
−3
,
)
2.52/−1.37
a cis-[PtCl2(SMe2)(AsPh3)].
b cis-[PtCl2(AsPh3)2]·CHCl3.
c R1=[(S DF)/(S Fo)].
d wR2=S[w(Fo2−Fc2)2]/S[w(Fo2)2]1/2
.

S. Otto, M.H. Johansson / Inorganica Chimica Acta 329 (2002) 135–140
137
3.1.1. Crystal structure of cis-[PtCl2(SMe2)(AsPh3)]
The compound crystallizes as mononuclear com-
plexes with a pseudo square planar coordination ge-
ometry with the chloride atoms in a cis configuration.
,
The PtꢀS bond distance of 2.262(2) A is within the
normal range for a bond of this nature [14,19]. No
crystallographic data are available for PtꢀAs bonds
trans to a chloro ligand, but the distance of 2.3531(10)
,
A obtained during this study is slightly shorter than the
sum of the covalent radii of As and Pt, 1.210 and 1.370
,
A, respectively, [10]. The difference in the PtꢀCl dis-
,
tances of 2.301(2) and 2.328(2) A trans to S and As,
respectively, is indicative of the difference in the trans
influences of these ligands, with that of AsPh3 being
larger than for SMe2.
All angles within the platinum coordination sphere
are close to 90°, ranging from 88.85(6) for AsꢀPꢀS to
91.07(6)° for AsꢀPtꢀCl(1). One would expect the angle
between the two most bulky ligands, i.e. AsꢀPtꢀS, to be
the largest within the coordination sphere, the opposite
was surprisingly observed. This may be the result of the
two methyl substituents on the dimethylsulfide ligands
directed away from the bulky arsine ligand towards
Cl(2), resulting in a SꢀPtꢀCl(2) angle of 90.77(8)°. The
Cl(2)ꢀPtꢀSꢀC(1) and Cl(2)ꢀPtꢀSꢀC(2) torsion angles of
−53.3(4) and 52.1(4)° indicate an almost perfect stag-
gered orientation of the methyl groups with respect to
the coordination plane. On the other hand the small
Cl(1)ꢀPtꢀAsꢀC(31) torsion angle of −26.1(3)° indicate
that phenyl ring 3 is directed towards Cl(1) resulting in
the slightly larger AsꢀPtꢀCl(1) angle of 91.07(6)°. An
almost identical coordination geometry was observed in
cis-[PtCl2(SMe2)(PMe2Ph)] [14].
Fig. 1. DIAMOND drawing showing the numbering scheme and ther-
mal ellipsoids (30% probability) for 1. Hydrogen atoms are of arbi-
trary size.
The CꢀAsꢀC angles range between 101.3(3) and
105.5(3)° while the CꢀAsꢀPt angles range from 111.5(2)
to 121.2(2)°. The compression of the CꢀAsꢀC angles
(L=Group 15 atom) is normal for this type of ligands
[13].
Fig. 2. Packing diagram of 1.
The packing within the unit cell (Fig. 2) seems to be
governed by van der Waals forces alone, with no strong
intermolecular interactions detected between the indi-
vidual molecules. The only possible intermolecular in-
teractions present are p–p stacking between phenyl ring
3 in the arsine ligand with the same ring in two adjacent
molecules. Ring 3 (symmetry x, y, z) has a distance of
,
5.315 and 5.550 A to ring 3 (1−x, 1−y, −z) and ring
3 (−x, 1−y, −z) respectively. Both have an angle of
0.02° with respect to the first ring.
3.1.2. Crystal structure of cis-[PtCl2(AsPh3)2]·CHCl3
The compound crystallizes as mononuclear com-
plexes with a pseudo square planar coordination ge-
ometry with the chloride atoms in a cis configuration.
Each platinum complex is accompanied by a severely
disordered chloroform solvent molecule.
Fig. 3. DIAMOND drawing showing the numbering scheme and ther-
mal ellipsoids (30% probability) for 2. Hydrogen atoms and the
chloroform solvent molecule are omitted for clarity.

138
S. Otto, M.H. Johansson / Inorganica Chimica Acta 329 (2002) 135–140
Fig. 4. Packing diagram of 2.
The Pt atom is situated on a general position in the
Cl(2)ꢀPtꢀAs(1) angle of 89.32(7)°, indicative of larger
steric strain in the latter.
unit cell resulting in the arsine- and chloro ligands,
which are chemically equivalent, to be crystallographi-
cally different. The individual PtꢀAs and PtꢀCl dis-
The tetrahedral angles around the two arsine atoms
in 2 are very similar ranging from 100.4(3) to 109.5(3)°
for CꢀAs(1)ꢀC and 97.7(3)–105.8(4)° for CꢀAs(2)ꢀC.
The CꢀAs(1)ꢀPt angles range from 111.44(18) to
118.71(17)° and CꢀAs(2)ꢀPt from 112.0(2) to 122.3(5)°.
These values are in agreement with that found in 1
indicating very similar geometries for the three
triphenylarsine ligands in the two studies.
The platinum complexes are packed in two layers
parallel to the y, z-plane in the middle of the unit cell.
On the outside of the platinum complex layers the
chloroform molecules are packed along the y, z-plane.
The two layers are rotated 180° with respect to each
,
tances vary by 0.017(1) and 0.026(3) A, respectively,
suggesting possible solvent interactions. The shortest
distances are comparable to those (Cl trans to As)
found in 1.
The As(1)ꢀPtꢀAs(2) angle of 97.87(3)° deviates sig-
nificantly from 90° indicating steric strain between these
two bulky ligands. Interestingly enough the angles
mainly compensating for this distortion is not the
ClꢀPtꢀCl angle, but in fact the ClꢀPtꢀAs angles. The
phenyl substituents on the two AsPh3 ligands are simi-
larly orientated, one ring above-, one below and one
almost parallel to the coordination plane. Phenyl ring 1
on As(2) is pointing towards As(1), while the corre-
sponding ring of As(1) is directed towards Cl(2). This
results in a Cl(1)ꢀPtꢀAs(2) angle of 84.30(5)° and a
Table 3
,
Selected bond distances (A), angles (°) and torsion angles (°) for 2
Bond distances
PtꢀAs(1)
PtꢀCl(1)
As(1)ꢀC(1)
As(1)ꢀC2
As(1)ꢀC3
2.3599(9)
2.3515(18) PtꢀCl(2)
1.950(7)
1.926(6)
1.932(6)
PtꢀAs(2)
2.3770(9)
2.3251(18)
1.951(7)
1.951(8)
1.938(8)
Table 2
,
Selected bond distances (A), angles (°) and torsion angles (°) for 1
As(2)ꢀC(1)
As(2)ꢀC(2)
As(2)ꢀC(3)
Bond distances
PtꢀAs
PtꢀCl(1)
AsꢀC(11)
AsꢀC(21)
AsꢀC(31)
2.3531(10)
2.301(2)
1.946(7)
1.927(7)
1.936(7)
PtꢀS
2.262(2)
2.328(2)
1.803(9)
1.792(10)
PtꢀCl(2)
SꢀC(1)
SꢀC(2)
Bond angles
Cl(1)ꢀPtꢀCl(2)
Cl(1)ꢀPtꢀAs(1)
Cl(2)ꢀPtꢀAs(1)
C(111)ꢀAs(1)ꢀC(121) 101.8(3)
C(111)ꢀAs(1)ꢀC(131) 100.4(3)
C(121)ꢀAs(1)ꢀC(131) 109.5(3)
C(111)ꢀAs(1)ꢀPt
C(121)ꢀAs(1)ꢀPt
C(131)ꢀAs(1)ꢀPt
89.32(7) As(1)ꢀPtꢀAs(2)
175.75(5) Cl(2)ꢀPtꢀAs(2)
88.67(5) Cl(1)ꢀPtꢀAs(2)
97.87(3)
173.09(5)
84.30(5)
105.0(3)
97.7(3)
105.8(4)
122.3(5)
112.0(2)
112.1(3)
C(211)ꢀAs(2)ꢀC(221)
C(211)ꢀAs(2)ꢀC(231)
C(221)ꢀAs(2)ꢀC(231)
Bond angles
Cl(1)ꢀPtꢀCl(2)
Cl(1)ꢀPtꢀAs
89.42(7) AsꢀPtꢀS
91.07(6) Cl(1)ꢀPtꢀS
178.03(6) Cl(2)ꢀPtꢀS
105.5(3)
101.3(3)
103.7(3)
111.5(2)
112.1(2)
88.85(6)
176.73(8)
90.77(8)
99.5(5)
106.4(3)
106.6(4)
121.2(2)
118.71(17) C(211)ꢀAs(2)ꢀPt
111.44(18) C(221)ꢀAs(2)ꢀPt
113.8(2)
Cl(2)ꢀPtꢀAs
C(11)ꢀAsꢀC(21)
C(11)ꢀAsꢀC(31)
C(21)ꢀAsꢀC(31)
C(11)ꢀAsꢀPt
C(21)ꢀAsꢀPt
C(1)ꢀSꢀC(2)
C(1)ꢀSꢀPt
C(2)ꢀSꢀPt
C(231)ꢀAs(2)ꢀPt
Torsion angles
Cl(1)ꢀPtꢀAs(2)ꢀ
C(211)
Cl(1)ꢀPtꢀAs(2)ꢀ
C(221)
C(31)ꢀAsꢀPt
172.6(3)
61.6(3)
Cl(2)ꢀPtꢀAs(1)ꢀ
C(111)
Cl(2)ꢀPtꢀAs(1)ꢀ
C(121)
Cl(2)ꢀPtꢀAs(1)ꢀ
C(131)
−14.0(2)
−131.7(2)
103.9(2)
Torsion angles
Cl(1)ꢀPtꢀAsꢀC(11)
Cl(1)ꢀPtꢀAsꢀC(21)
Cl(1)ꢀPtꢀAsꢀC(31)
−145.1(2)
96.9(2)
−26.1(3)
Cl(2)ꢀPtꢀSꢀC(1)
Cl(2)ꢀPtꢀSꢀC(2)
−53.3(4)
52.1(4)
Cl(1)ꢀPtꢀAs(2)ꢀ
C(231)
−57.2(3)

S. Otto, M.H. Johansson / Inorganica Chimica Acta 329 (2002) 135–140
139
Table 4
Geometrical parameters for cis-[Pt(Cl)2(L1)(L2)] complexes (Cln trans to Ln, n=1 or 2)
a
,
,
,
,
,
Complex
PtꢀL1 (A)
PtꢀCl1 (A)
PtꢀL2 (A)
PtꢀCl2 (A)
PtꢀClavg (A)
References
cis-[PtCl2(Sme2)(Me2SO)]
cis-[PtCl2(Sme2)(AsPh3)]
cis-[PtCl2(Sme2)(PMe2Ph)]
(NH4)2[PtCl4]
2.294(3)
2.262(2)
2.270(3)
2.305(5)
1.978(5)
2.00(2)
2.172(6)
2.154(5)
2.2801(19)
2.269(1)
2.251(3)
2.491(1)
2.497(1)
2.3599(9)
2.267(3)
2.245(1)
2.299(3)
2.301(2)
2.299(3)
2.211(4)
2.3531(10)
2.224(3)
2.320(4)
2.328(2)
2.367(3)
[14]
TW b
[14]
[15]
[16]
[17]
[18]
2.305(5)
2.269(4)
2.310(7)
2.312(4)
cis-[PtCl2(MeCN)2]
cis-[PtCl2(NH3)2]
2.266(2)
2.315(7)
2.315(1)
1.969(5)
2.08(2)
2.271(2)
2.306(7)
2.309(1)
cis-[PtCl2(COD)] c
2.176(6)
2.178(6)
2.2832(18)
2.272(1)
2.238(3)
2.510(1)
2.512(1)
2.3770(9)
2.244(3)
2.242(1)
cis-[Pt(Cl)2(SPh2)2]
cis-[Pt(Cl)2(SMe2)2]
cis-[Pt(Cl)2(Me2SO)2]
cis-[Pt(Cl)2(SbPh3)2]
2.319(2)
2.319(1)
2.313(3)
2.354(3)
2.337(4)
2.3515(18)
2.329(3)
2.355(1)
2.295(2)
2.315(1)
2.319(4)
2.326(4)
2.333(3)
2.3251(18)
2.360(3)
2.359(1)
2.307(17)
2.317(3)
2.316(4)
2.338(12)
[19]
[20]
[21]
[4]
cis-[Pt(Cl)2(AsPh3)2]
cis-[Pt(Cl)2(PPh3)2]
cis-[Pt(Cl)2(PMe2Ph)2]
2.338(19)
2.35(2)
2.357(3)
TW
[22]
[23]
2
a The error in PtꢀClavg is calculated as: ꢀꢁn(dn−d) /(n−1).
(
b TW, this work.
c COD, cis,cis-1,5-cyclooctadiene.
other with Cl(2) (short PtꢀCl distance) pointing to-
wards the platinum complexes in the adjacent layer and
Cl(1) (long PtꢀCl bond distance) are facing the solvent
molecules. Since the solvent molecules are disordered
and no hydrogen atom is placed on the chloroform
carbon, no formal hydrogen bonding- or other interac-
tions between Cl(1) and the solvent molecules could be
established, no intermolecular p–p interactions of the
phenyl rings were observed either.
influence of AsPh3 is comparable to that of SbPh3,
larger than that of Cl−, all the Sꢀ, Nꢀ and olefin donor
ligands, but still slightly smaller than that of PPh3 and
PMe2Ph. The overall trans influence series established
is,
PMe2Ph\PPh3\AsPh3:SbPh3\Me2SO:
SMe2:SPh2\NH3:olefin\Cl−\MeCN. It should
be noted that the errors in PtꢀClavg in Table 4 have not
been used to discriminate between the trans influence of
the ligands since these errors mainly reflect the inter-
molecular effect on the PtꢀCl bonds as discussed by
Johansson et al. [6].
3.2. trans Influence series
Table 4 shows a summary of bond distances for
related complexes found in the literature. Both the
average PtꢀAs and PtꢀCl bond distances determined for
2 are slightly longer than the PtꢀAs and PtꢀCl(2) bond
distances found in 1. The lengthening of the PtꢀAs
bonds may be a result of the larger extent of steric
crowding in 2 due to the presence of two bulky AsPh3
ligands in the coordination sphere, as evident also from
the large AsꢀPtꢀAs angle of 97.87(3)°. The long
PtꢀCl(1) distance found in 2 is most probably a result
of interaction with the solvent molecule as it deviates
significantly from the other two PtꢀCl bonds trans to
As in 1 and 2.
From Table 4 it is clear that in the mixed complexes
cis-[PtCl2(SMe2)(L)] (L=SMe2, Me2SO, AsPh3,
PMe2Ph) the trans influence of AsPh3 is slightly larger
than that of SMe2 and Me2SO, but significantly smaller
than that of PMe2Ph. In the series of complexes cis-
[PtCl2(L)2] (L=Cl−, MeCN, NH3, COD, SPh2, SMe2,
Me2SO, SbPh3, AsPh3, PPh3 and PMe2Ph) the trans
4. Supplementary material
Tables of the atomic coordinates, the anisotropic
temperature factors for non-hydrogen atoms, equiva-
lent isotropic temperature factors for the hydrogen
atoms and observed and calculated structure factors for
1 and 2 were deposited at the Cambridge Crystallo-
graphic Database.
Acknowledgements
,
Professor Ake Oskarsson is thanked for valuable
discussion of the work. The South African NRF, the
research fund of the University of the Free State, the
Swedish Natural Science Research Council, the Swedish
International Development Cooperation Agency and
the Crafoord foundation are acknowledged for finan-
cial support.

140
S. Otto, M.H. Johansson / Inorganica Chimica Acta 329 (2002) 135–140
[11] (a) G.M. Sheldrick, SHELXS97; Program for Solving Crystal
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