Platinum(II) complexes with the tridentate phosphino-thioether ligand bis(2-diphenylphosphinoethyl)sulfide, (PPh2CH2CH2)2S. X-ray crystal structures of [Pt {(PPh2CH2CH2)2S}Cl]ClO4 and [Pt {(PPh2CH2CH2)2S} I]I

Article abstract of DOI:10.1016/S0020-1693(99)00345-X

A series of new four coordinate Pt(II) complexes with the potentially tridentate chelate ligand bis(2-diphenylphosphinoethyl)sulfide (PSP) have been synthesized and characterized and the X-ray crystal stuctures of [Pt(PSP)Cl]ClO₄ and [Pt(PSP)I]I were determined. The spectroscopic data are consistent with the general formula [Pt(PSP)X]ⁿ⁺ with X = C1^-, Br^-, I^-, SCN^-, CN^-, thiourea or PPh₃ where all the three donor atoms in PSP are coordinated to platinum in all the complexes. Both the crystal structures show that the coordination sphere of the tridentate chelate system is strongly tetrahedrally distorted from a square planar geometry. The larger iodide ligand appears to cause a greater distortion. The potentially larger trans influence of iodide shows no effect on the structure of the, apparently, rigid Pt(PSP) moiety, whereas the trans influence of the chelating sulfur donor appears to be large which is reflected in unusually long platinum-halogen distances.

Full text of DOI:10.1016/S0020-1693(99)00345-X

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 295 (1999) 153–163
Platinum(II) complexes with the tridentate phosphino–thioether
ligand bis(2-diphenylphosphinoethyl)sulfide, (PPh2CH2CH2)2S.
X-ray crystal structures of [Pt{(PPh2CH2CH2)2S}Cl]ClO4 and
[Pt{(PPh2CH2CH2)2S}I]I
Lars V. Andreasen, Ole Simonsen, Ole Wernberg *
Department of Chemistry, Odense Uni6ersity, DK-5230 Odense M, Denmark
Received 14 April 1999; accepted 26 July 1999
Abstract
A series of new four coordinate Pt(II) complexes with the potentially tridentate chelate ligand bis(2-diphenylphosphino-
ethyl)sulfide (PSP) have been synthesized and characterized and the X-ray crystal stuctures of [Pt(PSP)Cl]ClO4 and [Pt(PSP)I]I
were determined. The spectroscopic data are consistent with the general formula [Pt(PSP)X]n+ with X=Cl−, Br−, I−, SCN−,
CN−, thiourea or PPh3 where all the three donor atoms in PSP are coordinated to platinum in all the complexes. Both the crystal
structures show that the coordination sphere of the tridentate chelate system is strongly tetrahedrally distorted from a square
planar geometry. The larger iodide ligand appears to cause a greater distortion. The potentially larger trans influence of iodide
shows no effect on the structure of the, apparently, rigid Pt(PSP) moiety, whereas the trans influence of the chelating sulfur donor
appears to be large which is reflected in unusually long platinum–halogen distances. © 1999 Elsevier Science S.A. All rights
reserved.
Keywords: Platinum(II) phosphine complexes; Phosphathia chelate ligand; Crystal structures; Trans influence
Prior to this work on Pt(II) complexes with the
potentially tridentate phosphino–thioether ligand bis(2-
1. Introduction
diphenylphosphinoethyl)sulfide (PSP), a series of transi-
The coordination chemistry of acyclic and macro-
tion metal complexes with this ligand have been
cyclic chelate ligands containing both phosphorus and
reported in the literature [1,2,12,13], including X-ray
sulfur donor atoms have received a considerable inter-
crystal structures of Ni(II) [14], Ag(I) [15,16] and Hg(II)
est and the platinum metal complexes of these phos-
[17] PSP complexes. In all the reported PSP complexes
phathia ligands have been investigated by several
with Ni(II), Pd(II) and Pt(II) the ligand is found to act
research groups. Thus, the dependence of the redox
properties of the complexes and the coordinating abili-
ties of the ligands on the geometrical arrangement of P
as a tridentate chelating ligand. Pt(II) and Pd(II) com-
plexes with the closely related chelate ligand PꢀS(O)ꢀP1
have also been synthesized and characterized recently
and S donor groups have been the subject of a series of
[3,4].
investigations [1–10]. Recently, improved catalysts for
As a part of our studies on rates and equilibria of
carbonylation of methanol using rhodium complexes
Pt(II) complexes containing tridentate chelate ligands
with chelating phosphathia ligands have also been re-
we have synthesized and characterized a series of
[Pt(PSP)X]n+ complexes with X=Cl−, Br−, I−, SCN−,
CN−, thiourea (tu) or PPh3 and determined the X-ray
crystal structures of [Pt(PSP)Cl]ClO4 and [Pt(PSP)I]I.
ported [11].
* Corresponding author. Tel.: +45-66-158 600; fax: +45-66-158
780.
E-mail address: owe@chem.ou.dk (O. Wernberg)
1 PꢀS(O)ꢀP is (PPh2CH2CH2)2SO.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00345-X

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L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
2. Experimental
2.1.2. [Pt(PSP)Cl]ClO4 (1a)
[Pt(PSP)Cl]Cl (1) (1.29 g, 1.78 mmol) was dissolved
in 15 ml CH2Cl2 and 75 ml methanol. A saturated
methanolic solution of LiClO4 was added drop-
wise until precipitation started and the cloudy solution
was added dropwise to 200 ml diethyl ether with rapid
stirring. The white microcrystals were collected, re-
dissolved in 500 ml methanol followed by addition of
a saturated LiClO4 methanolic solution until cloudi-
ness. Addition of an equivolume of water caused pre-
cipitation of the product which was isolated, washed
with ice cold water and dried in vacuo. Yield: 1.10 g,
85%.
Anal. Calc. for [Pt(PSP)Cl]ClO4, C28H28PtCl2O4P2S:
C, 42.65; H, 3.58; Cl, 8.99; S, 4.07. Found: C, 42.47; H,
3.54; Cl, 9.63; S, 3.90%. UV–Vis (20% v/v methanol/
water): umax (log m): 254 (4.31); 293 (3.97) nm. FAB MS:
m/z 689 [Pt(PSP)Cl]+ (100%).
The ligand bis(2-diphenylphosphinoethyl)sulfide
(PSP) was purchased from Argus Chemicals, Italy and
used as received. K2PtCl4 was obtained from Chempur
and K13CN (90 atom% 13C) from Merck, Sharp &
Dohme Isotopes, Montreal, Canada. All other reagents
were AR grade. Doubly distilled water was used
throughout and all other solvents were HPLC grade.
1H, 13C{1H} and 31P{1H} NMR spectra were
recorded on a Varian 300 MHz Gemini spectrometer at
1
300, 75.46 and 121.49 MHz, respectively. H and 13C
chemical shifts are referenced to TMS and positive 31P
chemical shifts are downfield from 85% H3PO4 external
standard. IR spectra were measured both as KBr discs
and Nujol mulls using a Perkin–Elmer 1720 (FT-IR)
spectrometer at 1 cm−1 resolution. Within the experi-
mental accuracy both methods gave identical results for
each sample. FAB mass spectra were recorded on a
Kratos MS 50 TC. UV–Vis spectra were recorded on a
Shimadzu UV-3100. Elemental analyses were per-
formed by the Microanalytical Laboratory of the H.C.
Ørsted Institute, Copenhagen University and by At-
lantic Microlab, Norcross, GA, USA.
2.1.3. [Pt(PSP)Br]Br (2)
[Pt(PSP)Cl]Cl (1) (310 mg, 0.43 mmol) was dissolved
in 120 ml methanol and 40 ml water. KBr (540 mg, 4.50
mmol) in 20 ml 50% v/v methanol/water was added
dropwise and the mixture was left for 24 h. The volume
was reduced to 70 ml and after cooling the concen-
trated solution to 0°C the crude product of 2 was
collected by filtration and washed with water. Yield:
238 mg, 68%.
Caution: Those of the complexes isolated as perchlo-
rate salts were treated as potential explosives.
2.1. Syntheses
A portion of the crude product of 2 (136 mg, 0.17
mmol) was redissolved in 100 ml methanol and 2.5 ml
2.0 M KBr in 50% v/v methanol/water mixture was
added, followed by 50 ml of water. The volume was
reduced to 50 ml and the white product was collected
by filtration, washed with water followed by diethyl
ether and dried in vacuo. Yield: 83 mg, 61%.
Anal. Calc. for [Pt(PSP)Br]Br·2H2O, C28H28PtBr2P2S·
2H2O: C, 39.59; H, 3.80; Br, 18.81; S, 3.77. Found: C,
39.79; H, 3.59; Br, 19.07; S, 3.64%. UV–Vis (20% v/v
methanol/water): umax (log m): 260 (4.29); 305 (3.78) nm.
FAB MS: m/z 733 [Pt(PSP)Br]+ (100%).
2.1.1. [Pt(PSP)Cl]Cl (1)
The procedure for synthesizing [Pt(PSP)Cl]Cl is a
modification of the literature method [1]. To K2PtCl4
(1.81 g, 4.36 mmol) in 20 ml water were added 20 ml
CH3CN. The solution was heated to 70°C for 15 min.
A suspension of the PSP ligand (2.00 g, 4.36 mmol) in
50 ml CH3CN was added dropwise to the warm solu-
tion and the mixture was refluxed for 15 min. After
evaporation of all the solvent, the crude, bright yellow
product [Pt(PSP)Cl]Cl was redissolved in 80 ml CH2Cl2,
leaving some KCl which was filtered off before remov-
ing the solvent under reduced pressure. Yield: 2.87 g,
91%.
A portion of the crude [Pt(PSP)Cl]Cl (1.13 g, 1.56
mmol) was dissolved in 5 ml CHCl3 and added 15 ml
methanol. This solution was added dropwise to 500 ml
diethyl ether with rapid stirring. The resulting white
product was collected by filtration, washed with diethyl
ether and dried in vacuo (B10−3 atm.). Yield: 1.03 g,
91%. FAB MS: m/z 689 [Pt(PSP)Cl]+ (100%).
The recrystallized [Pt(PSP)Cl]Cl (1) gives FAB MS
and 31P{1H} NMR spectra identical to those of the
purified product 1a described below. Several batches of
1 were made, since [Pt(PSP)Cl]Cl was used as the
starting material in the syntheses of 1a–7.
2.1.4. [Pt(PSP)I]I (3)
After dissolving [Pt(PSP)Cl]Cl (1) (158 mg, 0.22
mmol) in 70 ml methanol, 35 ml water were added,
followed by dropwise addition of NaI (92 mg, 0.61
mmol) dissolved in 30 ml 50% v/v methanol/water.
Precipitation of the yellow product started before all
the NaI solution had been added. After 24 h, the
volume was reduced to 40 ml and the product was
collected by filtration, washed with water and dried in
vacuo. Yield: 174 mg, 88%.
Anal. Calc. for [Pt(PSP)I]I, C28H28PtI2P2S: C, 37.06;
H, 3.11; I, 27.97; S, 3.53. Found: C, 37.02; H, 3.12; I,
27.69; S, 3.56%. UV–Vis (20% v/v methanol/water):
umax (log m): 268 (4.18); 340 (3.47) nm. FAB MS: m/z
780 [Pt(PSP)I]+ (100%).

L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
155
2.1.5. [Pt(PSP)(CNS)]SCN (4)2
2.1.8. [Pt(PSP)(PPh3)](ClO4)2 (7)
[Pt(PSP)Cl]Cl (1) (371 mg, 0.51 mmol) was dissolved
in 180 ml methanol and 60 ml water. NH4SCN (191
mg, 2.51 mmol) in 25 ml 75% v/v methanol/water was
added and the mixture was left for 1 h. The volume was
reduced to 75 ml and the yellow precipitate was after-
wards collected by filtration, washed with water fol-
lowed by diethyl ether and dried in vacuo. Yield: 270
mg, 68%.
[Pt(PSP)Cl]Cl (1) (301 mg, 0.42 mmol) was dissolved
in 5 ml CH2Cl2 and 15 ml methanol and added PPh3
(548 mg, 2.09 mmol) in 10 ml acetone. After 24 h, the
volume was reduced to 5 ml under reduced pressure
and to the concentrated solution were added 2 ml of a
saturated methanolic LiClO4 solution, which caused
precipitation of white microcrystals. The crude product
of 7 was collected by filtration, redissolved in 200 ml
methanol and to the mixture were added 10 ml satu-
rated methanolic LiClO4 solution. The final white
product was collected by filtration, washed with water
followed by diethyl ether and dried in vacuo. Yield: 275
mg, 59%.
Anal. Calc. for [Pt(PSP)(PPh3)](ClO4)2, C46H43PtCl2-
P3SO8: C, 49.56; H, 3.89; Cl, 6.36; S, 2.88. Found: C,
49.54; H, 3.85; Cl, 6.40; S, 2.85%. UV–Vis (20% v/v
methanol/water): umax (log m): 258 (4.38); 276 (sh) nm.
FAB MS: m/z 1015 {[Pt(PSP)(PPh3)](ClO4)}+ (74%),
915 {[Pt(PSP)(PPh3)]}+ (52%), 653 {[Pt(PSP)]}+
(100%).
Anal. Calc. for [Pt(PSP)(CNS)]SCN·0.5H2O, C30H28-
PtP2S3N2·0.5H2O: C, 46.27; H, 3.75; N, 3.60. Found: C,
46.09; H, 3.60; N, 3.65%. UV–Vis (20% v/v methanol/
water): umax (log m): 275 (4.18); 345 (3.31) nm. FAB MS:
m/z 711 [Pt(PSP)(CNS)]+ (100%). IR: w(CN); 2124 (s),
2097 (s), 2054 (s) cm−1
.
2.1.6. [Pt(PSP)CN]ClO4 (5)
[Pt(PSP)Cl]Cl (1) (197 mg, 0.27 mmol) was dissolved
in 150 ml methanol and added 150 ml water. Over 5 h,
a solution of KCN (19 mg, 0.29 mmol) in 100 ml 50%
v/v methanol/water was added dropwise. The reaction
mixture was filtered to remove traces of insoluble by-
products before reducing the volume to 150 ml. Addi-
tion of 25 ml saturated aqueous LiClO4 solution caused
slow precipitation of the white microcrystals, which
were collected by filtration after cooling to 0°C. The
isolated product was washed with ice cold water fol-
lowed by diethyl ether and dried in vacuo. Yield: 105
mg, 50%.
2.2. Crystal structure determinations
Crystals of [Pt(PSP)Cl]ClO4 and [Pt(PSP)I]I were
grown by slow diffusion of diethyl ether into solutions
of 1a or 3 in 30% v/v chloroform/methanol. The crys-
tals of 1a were colourless and of suitable size for X-ray
analysis, whereas 3 crystallized as bright yellow needles,
which had to be cut to obtain a suitable size.
Anal. Calc. for [Pt(PSP)CN]ClO4·0.5H2O, C29H28-
PtClP2SNO4·0.5H2O: C, 44.20; H, 3.71; N, 1.78.
Found: C, 44.15; H, 3.54; N, 1.67%. UV–Vis (20% v/v
methanol/water): umax (log m): 247 (4.42); 269 (sh), 276
(sh) nm. FAB MS: m/z 679 [Pt(PSP)CN]+ (100%). IR:
X-ray diffraction data were collected on a Siemens
SMART CCD diffractometer at 120 K using Mo Ka
radiation. Data were corrected for Lorentz and polar-
ization effects and absorption (empirically) using SAINT
and SADABS in SMART software [18]. For both com-
plexes 1a and 3 the unit cell parameters were deter-
mined from 4096 reflections. Crystal data and details
on data collections and refinements are presented in
Table 1. The structures were determined and refined by
use of the programs included in the Xtal 3.2 system
[19]. The coordinates of the platinum atoms in the
structures of 1a and 3 were deduced from the Patterson
function and all the remaining non-hydrogen atoms
were localized from successive difference Fourier maps.
The structure of 1a was refined by full-matrix least-
squares calculations (CRYLSQ) [20] with anisotropic
displacement parameters for all non-hydrogen atoms.
w(CN); 2144 (s) cm−1
.
2.1.7. [Pt(PSP)(tu)](ClO4)2 (6)
[Pt(PSP)Cl]Cl (1) (218 mg, 0.30 mmol) was dissolved
in 100 ml methanol and added 50 ml water. Thiourea
(tu) (68 mg, 0.90 mmol) in 10 ml water was added,
causing a colour change from colourless to yellow.
After 30 min, 10 ml saturated aqueous LiClO4 solution
were added and the mixture was left at 5°C for 24 h
during which bright yellow microcrystals separated out.
These were collected by filtration and washed with ice
cold water followed by diethyl ether and dried in vacuo.
Yield: 180 mg, 64%.
Anal. Calc. for [Pt(PSP)(tu)](ClO4)2·0.5H2O, C29H32-
PtCl2P2S2O8N2·0.5H2O: C, 37.15; H, 3.55; N, 2.99; Cl,
7.56; S, 6.84. Found: C, 37.22; H, 3.59; N, 2.87;
Cl, 7.55; S, 6.87%. UV–Vis (20% v/v methanol/water):
umax (log m): 268 (4.16); 335 (3.58) nm. FAB MS: m/z
829 {[Pt(PSP)(tu)](ClO4)}+ (34%), 728 {[Pt(PSP)(tu)-
(–H)3]}+ (100%), 653 {[Pt(PSP)]}+ (33%).
For the hydrogen atoms a fixed isotropic temperature
2
,
factor (Uiso=0.035 A ) was used and only the coordi-
nates were allowed to vary. The structure of 3 was
refined by full-matrix least-squares calculations
(CRYLSQ) with anisotropic displacement parameters
2 With the nomenclature ‘CNS’ we do not specify the coordination
mode of thiocyanate.
3 (–H) is defined as one proton abstracted from the complex.

156
L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
platinum and the iodide counter anion, indicate that
the residual electron density in 3 is artificial.
for the platinum, phosphorus, sulfur and iodine atoms.
The hydrogen atoms were included in the calculations
but the coordinates were not allowed to vary. Atomic
scattering factors were taken from International Tables
for X-ray Crystallography, Vol. IV, 1974.
3. Results and discussion
The thermal vibrations of the perchlorate counter
anion in 1a were moderate and allowed a good determi-
nation of positions for all the atoms in the anions. The
final R value for 1a was 0.038. In 3 the thermal
3.1. Syntheses
The chloro complexes 1 and 1a were synthesized by a
modified literature method [1]. Substitution of Cl−
from [Pt(PSP)Cl]+ with the appropriate nucleophile X−
in aqueous methanolic solution gave the desired prod-
ucts 2–4 [Pt(PSP)X]X, X=Br−, I− or SCN− and 5–6
[Pt(PSP)Y](ClO4)n with Y=CN− (n=1) or tu (n=2).
Due to the low solubility of PPh3 in water/methanol
mixtures the preparation of 7 was performed in organic
solvents. To the best of our knowledge, only three
Pt(II) complexes with PSP have previously been synthe-
sized [1], namely [Pt(PSP)Cl]ClO4, [Pt(PSP)I]I and
[Pt(PSP)I]ClO4. We extended the characterization of
the first two compounds by NMR, FAB MS and X-ray
analysis.
parameter Uiso for the iodide counter anion was large
2
,
(Uiso=0.099 A ) and we find that this probably con-
tributes to the rather large final R value 0.116 for 3.
For comparison, the thermal parameter for the coordi-
nated iodide was found to be significantly smaller
2
,
,
(Uiso=0.032 A ). The distances (0.77–1.37 A) between
the biggest tops in Dz-map and the nearest atoms,
Table 1
Crystal data and details of structure determinations for
[Pt(PSP)Cl]ClO4 (1a) and [Pt(PSP)I]I (3)
Complex
1a
3
Elemental analyses for 1a–7 all gave satisfactory
results. FAB mass spectra reveal {[Pt(PSP)X]}+ peaks
with the expected isotopic distribution for the com-
plexes 1–5. The two complexes 6 and 7 reveal peaks
with correct isotopic distribution for {[Pt(PSP)X]-
ClO4}+, X=tu or PPh3 and also for the ions formu-
lated as {[Pt(PSP)]}+, {[Pt(PSP)(tu)(–H)]}+ and
{[Pt(PSP)PPh3]}+. UV–Vis spectra of 1a–7 were
recorded with 20% v/v methanol/water solutions at
23.7°C.
Crystal data
Formula
Molecular weight
Crystal system
Space group
C28H28Cl2O4P2PtS C28H28I2P2PtS
788.522
monoclinic
P21/n
907.428
monoclinic
P21/c
,
a (A)
9.2311(2)
8.8196(2)
35.8466(7)
92.609(1)
2915.4(1)
4
18.684(2)
7.231(1)
22.969(1)
106.500(5)
2975.2(2)
4
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
Dcalc (g cm−3
F(000)
)
1.797
1.945
1544
1704
3.2. Crystal and molecular structures
v (mm−1
)
5.218
6.729
Crystal size (mm)
0.24×0.075
×0.035
0.0275×0.147
×0.147
3.2.1. [Pt(PSP)Cl]ClO4 (1a)
The crystal of [Pt(PSP)Cl]ClO4 (1a) which was used
for single crystal X-ray diffraction was found to crystal-
lize in the monoclinic space group P21/n. The molecular
structure of the cation [Pt(PSP)Cl]+ with the atomic
numbering scheme is shown in Fig. 1. Selected bond
distances and bond angles are given in Tables 2 and 3,
respectively.
The molecular structure of 1a confirms that the PSP
ligand acts as a tridentate chelating ligand, coordinat-
ing to platinum through the sulfur and both phospho-
rus atoms and that the chlorine atom occupies the
fourth coordination site.
Data collection
Temperature (K)
Wavelength (Mo Ka)
120
0.71073
120
0.71073
,
(A)
Scan type
Tmin, Tmax
q (°)
ꢀ
ꢀ
0.7444, 0.9265
3–29
0:12, 0:12,
−49:49
20293
0.5968, 0.8716
1–26
0:23, 0:9, −28:27
Data set (hkl)
No. reflections
measured
No. independent
reflections
31341
7676 (Rint=0.027) 5151 (Rint=0.093)
No. observed reflections 6681 [I\2.5|(I)]
4341 [I\2.5|(I)]
,
The PtꢀP bond lengths (PtꢀP(1)=2.317(1) A,
Refinement
No. refined parameters
R
wR
GOF
w
D/|av, D/|max
Dzmax, Dzmin (e A
,
PtꢀP(2)=2.315(1) A) are close to values given in the
427
0.038
0.039
1.50(1)
167
0.116
0.116
2.09(2)
literature for Pt(II) complexes with two mutually trans
ꢀPPh2 moieties [3,21–24]. The Pt–S distance (Pt–S=
2.254(1) A) is also within the range normally observed
for thioether donor groups in Pt(II) complexes with
Cl− in the trans position [25–31]. There is a general
tendency towards slightly shorter PtꢀS bond distances
,
B1/|2 (F)
0.0721, 0.836
1.20, −1.54
B1/|2 (F)
0.00086, 0.0143
4.28, −4.43
−3
,
)

L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
157
least-squares plane and to the same side as the sulfur
and chlorine atoms. The SꢀPtꢀCl(1) angle is 175.85(4)°
which is relatively close to the ideal 180°. In contrast,
the P(1)ꢀPtꢀP(2) angle is found to be only 161.14(4)°,
probably as a result of ring strain in the tridentately
bonding PSP ligand. Further, the small PꢀPtꢀS angles
for the two adjacent five-membered chelate rings
(P(1)ꢀPtꢀS=85.67(4)°, P(2)ꢀPtꢀS=86.44(4)°) also dis-
play the strained coordination geometry of the rings, as
generally observed in five-membered phosphine chelate
rings [3,7,22,23]. The bond distances and angles within
the PSP ligand are all in the ranges normally observed
for thioether and phosphine ligands [14–17,21–23].
It is seen that the span for the PtꢀPꢀC angles is
rather large, 105.5(2)–123.7(2)°, which is not unusual
[14,23]. The bond angles to the aliphatic carbons are at
the lower end of the span (PtꢀP(1)ꢀC(2)=106.0(2)°,
PtꢀP(2)ꢀC(4)=105.5(2)°). From the molecular struc-
ture it is seen that each phosphine group has one
phenyl ring positioned on each side of the least-squares
plane defined by the four donor atoms. The small
P(1)ꢀPtꢀP(2) angle might cause each phosphine group
to display the largest PtꢀPꢀC angle to the phenyl ring
positioned on the same side of the least-squares plane
as the chlorine atom (PtꢀP(1)ꢀC(11)=120.9(2)°,
PtꢀP(2)ꢀC(31)=123.7(2)°), although we cannot exclude
the possibility that the PtꢀPꢀC angles\120° are just
effects of crystal packing demands. If some steric repul-
sion exists between the chlorine atom and two phenyl
rings in close proximity, this could probably also con-
tribute to give the large observed PtꢀPꢀC angles. The
angles to the two phenyl rings on the opposite side of
the least-squares plane are significantly smaller,
107.8(2) and 108.4(2)°, respectively.
Fig. 1. ORTEP plot of [Pt(PSP)Cl]ClO4 (1a) with adopted numbering
scheme.
Table 2
,
Selected bond distances (A) for [Pt(PSP)Cl]ClO4 (1a)
PtꢀP(1)
PtꢀS
P(1)ꢀC(2)
P(1)ꢀC(11)
P(1)ꢀC(21)
SꢀC(1)
2.317(1)
2.254(1)
1.860(5)
1.815(5)
1.820(5)
1.837(6)
PtꢀP(2)
2.315(1)
2.347(1)
1.836(5)
1.821(5)
1.822(5)
1.834(5)
PtꢀCl(1)
P(2)ꢀC(4)
P(2)ꢀC(31)
P(2)ꢀC(41)
SꢀC(3)
Table 3
Selected bond angles (°) for [Pt(PSP)Cl]ClO4 (1a)
P(1)ꢀPtꢀP(2)
P(1)ꢀPtꢀS
161.14(4)
85.67(4)
93.11(4)
106.0(2)
120.9(2)
107.8(2)
106.0(2)
108.4(2)
SꢀPtꢀCl(1)
P(2)ꢀPtꢀS
175.85(4)
86.44(4)
95.88(4)
105.5(2)
123.7(2)
108.4(2)
106.2(2)
105.6(2)
P(1)ꢀPtꢀCl(1)
PtꢀP(1)ꢀC(2)
PtꢀP(1)ꢀC(11)
PtꢀP(1)ꢀC(21)
C(2)ꢀP(1)ꢀC(11)
C(2)ꢀP(1)ꢀC(21)
P(2)ꢀPtꢀCl(1)
PtꢀP(2)ꢀC(4)
PtꢀP(2)ꢀC(31)
PtꢀP(2)ꢀC(41)
C(4)ꢀP(2)ꢀC(31)
C(4)ꢀP(2)ꢀC(41)
3.2.2. [Pt(PSP)I]I (3)
The crystals of [Pt(PSP)I]I (3) are monoclinic belong-
ing to the space group P21/c. The molecular structure
of the cation [Pt(PSP)I]+ with the atomic numbering
scheme is shown in Fig. 2. Selected bond distances are
given in Table 4 and selected bond angles in Table 5.
The [Pt(PSP)I]+ cation is four coordinate, with one
iodine, I(1), coordinated to the metal center and with
PSP acting as a tridentate ligand. The iodide counter
anion, I(2), is positioned at a non-bonding distance
C(11)ꢀP(1)ꢀC(21) 107.3(2)
C(1)ꢀSꢀC(3) 103.6(2)
C(31)ꢀP(2)ꢀC(41) 106.2(2)
in complexes where the thioether group is part of a
chelate ring compared with complexes having mono-
dentate thioether ligands [25], and accordingly the PtꢀS
distance in 1a is in the lower end of the platinum–
thioether range. In contrast to the PtꢀP and PtꢀS
distances, which appear in the normal ranges, the
,
(4.040(3) A) from the nearest platinum atom.
,
The PtꢀP bond distances (PtꢀP(1)=2.294(7) A,
,
PtꢀCl(1) bond in 1a (PtꢀCl(1)=2.347(1) A) is longer
,
PtꢀP(2)=2.276(8) A) are shorter than those found in
than most PtꢀCl bond distances found for chloride
trans to a thioether in Pt(II) complexes [25–31].
The coordination sphere for platinum is tetrahedrally
distorted from planar geometry, with two phosphorus
1a, but still within the normal range for Pt(II) com-
plexes with two ꢀPPh2 moieties in a trans position
[3,21–24].
Although iodide is known to exert a larger trans
influence on PtꢀS bonds than chloride [8,25,26], the two
,
atoms on one side (0.21/0.20 A) of the least-squares
plane defined by (P(1),P(2),S,Cl(1)) and with the sulfur
,
PtꢀS bond distances in 1a (PtꢀS=2.254(1) A) and 3
,
,
,
(−0.21 A) and chlorine (−0.21 A) atoms on the
(PtꢀS=2.258(6) A) are nearly identical. That the PtꢀS
,
opposite side. Platinum is displaced 0.13 A from the
bond in 3 is rather short is seen from comparison with

158
L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
Table 5
the range for PtꢀS bonds in other Pt(II) complexes having
Selected bond angles (°) for [Pt(PSP)I]I (3)
,
the trans iodide–thioether motif (2.262(2)–2.280(5) A
[25,26]. A comparison of the PtꢀI bond length in 3
P(1)ꢀPtꢀP(2)
P(1)ꢀPtꢀS
P(1)ꢀPtꢀI(1)
PtꢀP(1)ꢀC(2)
PtꢀP(1)ꢀC(11)
PtꢀP(1)ꢀC(21)
C(2)ꢀP(1)ꢀC(11)
C(2)ꢀP(1)ꢀC(21)
C(11)ꢀP(1)ꢀC(21) 106(1)
C(1)ꢀSꢀC(3) 105(1)
156.6(2)
86.6(2)
97.7(2)
105.8(9)
125.2(9)
107.2(8)
106(1)
SꢀPtꢀI(1)
P(2)ꢀPtꢀS
P(2)ꢀPtꢀI(1)
PtꢀP(2)ꢀC(4)
PtꢀP(2)ꢀC(31)
PtꢀP(2)ꢀC(41)
C(4)ꢀP(2)ꢀC(31)
C(4)ꢀP(2)ꢀC(41)
C(31)ꢀP(2)ꢀC(41)
170.3(2)
86.6(2)
92.6(2)
105.4(9)
109(1)
124(1)
103(1)
106(1)
108(1)
,
(PtꢀI(1)=2.613(2) A) with data for the above-mentioned
complexes reveals that, as found in 1a, the plat-
inumꢀhalogen bond is significantly longer than in other
104(1)
complexes having thioethers trans to iodide (2.601(1)–
,
2.602(2) A) [25,26].
The structure of 3 shows an increased distortion
relative to 1a, which seems to reflect the larger steric
demands of the iodide. Thus, the deviations from the
least-squares plane defined by (P(1), P(2), S, I(1)) are:
,
,
,
,
P(1), 0.33 A; P(2), 0.44 A; S, −0.40 A; I(1), −0.02 A and
,
Pt, −0.03A from which it is seen that 3 is also tetrahe-
drally distorted from planar geometry. The larger distor-
tion in 3 is also evident from the smaller angles for the
trans donors, with SꢀPtꢀI(1)=170.3(2)° and P(1)ꢀPtꢀ
P(2) only 156.6(2)°. As expected, the PꢀPtꢀS angles of the
five-membered chelate rings are smaller than 90°
(P(1)ꢀPtꢀS=86.6(2)°, P(2)ꢀPtꢀS=86.6(2)°), while the
two PꢀPtꢀI(1) angles are 97.7(2) and 92.6(2)°. The
distances and angles within the coordinated PSP ligand in
3 are close to those found in 1a.
Like in 1a the two phenyl rings in each phosphine
group are on either side of the least-squares plane. The
small P(1)ꢀPtꢀP(2) angle in 3 results in even larger PtꢀPꢀ
C angles to the two phenyl rings closest to the iodine
atom (PtꢀP(1)ꢀC(11)=125.2(9)°, PtꢀP(2)ꢀC(41)=124-
(1)°) when compared to the corresponding angles in 1a.
A stereo view of the unit cell (see Fig. 3) reveals that the
large thermal vibrations of the counter anion, I(2),
Fig. 2. ORTEP plot of [Pt(PSP)I]I (3) with adopted numbering
scheme.
Table 4
,
Selected bond distances (A) for [Pt(PSP)I]I (3)
PtꢀP(1)
PtꢀS
P(1)ꢀC(2)
P(1)ꢀC(11)
P(1)ꢀC(21)
SꢀC(1)
2.294(7)
2.258(6)
1.86(2)
1.75(3)
1.87(2)
1.84(3)
PtꢀP(2)
PtꢀI(1)
P(2)ꢀC(4)
P(2)ꢀC(31)
P(2)ꢀC(41)
SꢀC(3)
2.276(8)
2.613(2)
1.87(2)
1.82(3)
1.83(3)
1.85(3)
Fig. 3. Stereo view of the unit cell in [Pt(PSP)I]I (3).

L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
159
Table 6
31P{1H} NMR data a
Compound
l
31P{1H} (ppm)
1J(PtP) (Hz)
Z (ppm)
PSP b
ꢀ16.4
38.9
38.7
39.0
39.0
40.5
44.1
39.7
38.9
44.5
10.0
[Pt(PSP)Cl]Cl (1)
[Pt(PSP)Cl]ClO4 (1a)
[Pt(PSP)Br]Br (2)
[Pt(PSP)I]I (3)
2547
2538
2519
2473
2459
2515
2417
2551
2402
3270
55.3
55.1
55.4
55.4
56.9
60.5
56.1
55.3
60.9
[Pt(PSP)(CNS)]SCN (4)
[Pt(PSP)CN]ClO4 (5)
[Pt(PSP)(tu)](ClO4)2 (6)
[Pt(PSP)(PPh3)](ClO4)2 (7)
c
c
a In CDCl3 solution at 293 K, unless otherwise stated.
b In agreement with l −16.4 in CD3CN [2].
c In DMSO-d6 solution at 293 K, due to the low solubility in CDCl3.
are mainly directed towards one of the phenyl rings,
(C(41)ꢀC(46)), resulting in larger thermal vibrations of
C(45) (see Fig. 2).
to a thioether group [26]. No coupling of PPh3 with
PSP is observed in the spectrum, which might indicate
that J(ꢀPPh2,PPh3) is B2 Hz.
2
In the 31P{1H} spectrum of [Pt(PSP)(CNS)]SCN (4)
two 31P resonances with 195Pt satellites are observed at
l 44.1 and 40.5 in a ca. 6:1 intensity ratio, thus indicat-
ing the presence of two different complexes in solution.
From Z data, it is evident that in both complexes PSP
is tridentately coordinated. More conclusive evidence
comes from the IR spectra of crystalline [Pt(PSP)-
(CNS)]SCN (4), where three bands are observed in the
w(CN) region, the lowest frequency at 2054 cm−1 being
close to the reported value for salts containing the
SCN− ion [33,35,36]. At higher frequencies a sharp
band at 2124 cm−1, assigned to the ꢀSCN isomer, is
3.3. NMR and IR spectra
In the 31P{1H} NMR spectra of the platinum com-
plexes 1–7, all 31P resonances are singlets with satellites
of 17% intensity, corresponding to the natural abun-
dance of the 195Pt isotope, and hence in accordance
with the two PSP phosphine groups in each complex
being chemically equivalent and both coordinated to
platinum. The spectra of 1–3 and 5–6 show just one
31P resonance, while two singlets are observed in the
1
spectra of 4 and 7 (see discussion below). The J(PtP)
observed along with a broader band at 2097 cm−1
,
range for 1–7 (see Table 6) is in good agreement with
literature data for Pt(II) complexes having two mutu-
ally trans ꢀPPh2 moieties [3,21,32,33] and is support for
the trans ꢀPPh2 configuration observed in the crystal
structures of 1a and 3.
The range of the coordination chemical shift Z is
found to be 55.1–60.9 ppm for 1–7, where Z is defined
as the difference in 31P chemical shift between the
complex and the free PSP ligand. The observed range
of Z is indicative of phosphines being part of a five-
membered chelate ring [6,10,34], thus consistent with
the PSP ligand binding tridentately to platinum in all
the prepared complexes.
assigned to the ꢀNCS isomer. This assignment is made
from the general observation that S-bonded thio-
cyanate results in higher w(CN) and sharper bands than
does N-bonded thiocyanate [35,37]. Thus, IR reveals
that the solid sample of 4 contains both the N- and
S-bonded thiocyanate with the values of 4 being close
to literature data for Pt(II) and Pd(II) thiocyanato
complexes [33,37–41]. Consistent with these IR results,
the 31P{1H} data of 4 can be explained by the presence
of both N- and S-bonded thiocyanato complexes in
solution. In our case, it is not possible to specifically
assign the 31P resonances to the two linkage isomers,
since chemical shifts alone do not indicate the coordina-
tion mode of thiocyanate [41]. Though, data from the
sterically comparable complex [Pt(triphos4)(CNS)]+
show that S-bonded thiocyanate results in a larger
chemical shift for the ꢀPPh2 group than does N-bonded
thiocyanate [32,42].
As mentioned above, the spectrum of 7 shows two
31P singlets, both having 195Pt satellites, and with a
relative intensity 2:1 for the two resonances at l 44.5
and 10.0, respectively. From this intensity ratio and the
observed l 31P range of 1–6, the downfield resonance
at l 44.5 is easily assigned to the PSP ligand and the l
10.0 resonance to the coordinated PPh3 group. Both the
1
chemical shift and the J(PtP) (3270 Hz) of the PPh3
ligand are similar to data for Pt(II) having PPh3 trans
4 Triphos is bis(2-diphenylphosphinoethyl)phenylphosphine.

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L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
The kinetics and thermodynamics of linkage iso-
and pairwise identical to the proton equally positioned
in the other chelate ring. This ‘frozen’ l–u conformation
may arise from the strained geometry of the coordinated
PSP ligand, which probably does not allow free l–u
conformational interconversions. A similar pattern of
multiplets for protons in a five-membered ꢀPCH2CH2Sꢀ
chelate ring is observed in [Pd(PꢀS(O)ꢀP)Cl]ClO4 [4],
where it is assumed that a conformational ‘interlocking’
of the l–u ring conformation exists due to steric repul-
sion between the SꢁO group and ꢀSCH2ꢀ protons. In the
present case, we cannot exclude the possibility that a
simultaneous l–u conformational exchange process for
both rings could occur on the NMR time scale. However,
a fast change from l–u to either l–l or u–u is unlikely,
since this would average out the resonances of protons
attached to the same carbon atoms, resulting in only two
aliphatic multiplets.
merism in [Pt(PSP)(CNS)]+ are currently under investi-
gation in this group to clarify how, e.g., steric, electronic
and medium effects influence the coordination mode of
the thiocyanate ligand in Pt(II) complexes having the
trans thioether-CNS donor group motif.
Table 7 presents 1H NMR data of the free PSP ligand
and the complexes 1a–7. The spectrum of the free PSP
ligand in CDCl3 shows a multiplet in the aromatic region
for the phenyl ring protons, l 7.25–7.45 (m, 20H) and
two multiplets in the aliphatic region due to the two
different methylene groups; l 2.20–2.35 (m, PCH2, 4H),
l 2.50–2.65 (m, SCH2, 4H).
Common for all the 1H NMR spectra of the complexes
1a–7 is the presence of four groups of multiplets in the
aliphatic region, each integrating to 2H (see Fig. 4). This
suggests that the eight aliphatic protons are pairwise
equivalent. If the l–u conformation of the two five-mem-
bered chelate rings observed in both crystal structures of
1a and 3 persists in solution, the symmetry would allow
the four protons in each chelate ring to be distinguishable
1
In the aromatic region of the H NMR spectra for
1a–5 two multiplets are seen, one around l 7.45–7.70 (m,
12H) and one l 7.70–7.90 (m, 8H). For 6 only one
multiplet is observed, l 7.50–7.80 (m, 20H), along with
Table 7
1H NMR data a
Compound
l Aliphatic protons (ppm)
l Aromatic protons (ppm)
PSP
1a
2.20–2.35 (m, 4H)
2.55–2.70 (m, 2H)
3.05–3.20 (m, 2H)
2.65–2.80 (m, 2H)
3.20–3.35 (m, 2H)
2.60–2.80 (m, 2H)
3.15–3.35 (m, 2H)
2.70–2.90 (m, 2H)
3.40–3.80 (m, 4H)
2.65–2.80 (m, 2H)
3.00–3.20 (m, 2H)
2.90–3.10 (m, 2H)
3.35–3.55 (m, 2H)
2.95–3.15 (m, 2H)
3.20–3.40 (m, 2H)
2.50–2.65 (m, 4H)
7.25–7.45 (m, 20H)
7.45–7.60 (m, 12H)
7.75–7.90 (m, 8H)
7.45–7.60 (m, 12H)
7.75–7.90 (m, 8H)
7.45–7.60 (m, 12H)
7.70–7.85 (m, 8H)
7.45–7.65 (m, 12H)
7.70–7.80 (m, 8H)
7.45–7.60 (m, 12H)
7.70–7.90 (m, 8H)
7.50–7.80 (m, 20H)
(7.90–8.20 (tu)) c
3.30–3.60 (m, 2H)
4.00–4.30 (m, 2H)
3.40–3.60 (m, 2H)
4.30–4.80 (m, 2H)
3.40–3.65 (m, 2H)
3.75–4.25 (m, 2H)
4.00–4.40 (m, 2H)
2
3
4
5
3.60–3.90 (m, 2H)
3.95–4.35 (m, 2H)
3.60–4.10 (m, 4H)
6 b
7 b
3.65–3.85 (m, 2H)
3.95–4.15 (m, 2H)
6.90–7.80 (m, 35H)
a In CDCl3 solution at 293 K, unless otherwise stated. m=multiplet.
b In DMSO-d6 solution at 293 K, due to the low solubility in CDCl3.
c Broad resonance from the coordinated thiourea ligand.
Fig. 4. 1H NMR spectrum of [Pt(PSP)I]I (3) in CDCl3, showing the resonances in the aliphatic region of the spectrum.

L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
161
Table 8
13C{1H} NMR data a
Compound
ppm
Hz
l Cipso
l Cortho
l Cmeta
l Cpara
l PCH2
l SCH2
(1J(PC)) b
(2J(PC)) b
(3J(PC)) b
(1J(PC)) b
PSP
137.9 d (13)
128.3 t (57)
127.6 t (57)
51 Hz
127.4 t (59)
127.0 t (59)
28 Hz
127.4 t (60)
127.4 t (60)
0 Hz
125.6 t (59)
125.2 t (59)
29 Hz
127.3 t (61)
126.2 t (61)
84 Hz
127.9 t (58)
127.2 t (58)
53 Hz
132.7 d (19)
133.5 t (13)
133.2 t (13)
22 Hz
133.6 t (13)
133.5 t (13)
3 Hz
134.0 t (13)
133.7 t (13)
24 Hz
133.8 t (14)
133.3 t (14)
33 Hz
133.3 t (14)
133.1 t (14)
17 Hz
133.3 t (13)
133.1 t (13)
15 Hz
128.6 d (7)
129.4 t (11)
129.3 t (11)
11 Hz
129.4 t (11)
129.4 t (11)
2 Hz
129.4 t (11)
129.3 t (11)
3 Hz
129.7 t (11)
129.7 t (11)
5 Hz
130.0 t (12)
129.9 t (12)
7 Hz
129.4 t (11)
129.2 t (11)
15 Hz
128.8 s
132.4 s
132.3 s
12 Hz
132.5 s
132.4 s
10 Hz
132.6 s
132.4 s
12 Hz
133.1 s
132.9 s
13 Hz
133.0 s
132.9 s
15 Hz
132.6 s
132.3 s
22 Hz
28.3 d (15)
31.3 t (36)
28.0 d (22)
36.8 s
(1) c
(2) c
(1)–(2) c
(1)
(2)
(1)–(2)
(1)
(2)
(1)–(2)
(1)
(2)
(1)–(2)
(1)
1a
33.7 t (36)
35.4 t (36)
35.6 t (38)
33.7 t (38)
33.1 t (36)
39.0 s
38.0 s
37.7 s
36.5 s
36.4 s
34.7 s
2
3
4
5
(2)
(1)–(2)
(1)
(2)
(1)–(2)
6 d
7 d
e
125.6 d (86)
134.2 d (12)
128.5 d (11)
132.2 s
–
a In CDCl3 solution at 293 K, unless otherwise stated. s=singlet, d=doublet, t=virtual 1:2:1 triplet.
n
b These coupling constants are for 1a–6 the sum ꢀ J(PC)+n+2J(P%C)ꢀ, though for n\1, the n+2J(P%C) is usually very small [44].
c (1) and (2) denotes first and second virtual 1:2:1 triplet/singlet, respectively, and (1)–(2) denotes the difference in chemical shift in Hz between
(1) and (2).
d In DMSO-d6 solution at 293 K, due to the low solubility in CDCl3.
e Not observed, probably masked by the DMSO-d6 resonance.
a broad resonance l 7.90–8.20 from the protons on the
coordinated thiourea ligand. The spectrum of 7 is more
complex with four overlapping multiplets, l 6.90–7.80
(m, 35H), arising from the phenyl group protons from
both PSP and PPh3.
and Cmeta are seen as doublets while Cpara show up as a
singlet and the PPh3 phenyl rings only give rise to broad
resonances.
A special feature in the 13C{1H} spectra of the com-
plexes 1a–6 compared to other trans bis-phosphine Pt(II)
complexes is that two 1:2:1 triplets are found in a 1:1 ratio
for Cipso, Cortho and Cmeta along with two broadened
singlets for the Cpara (see Fig. 5). This is not observed for
the methylene carbons, which just show one 1:2:1 triplet
from PCH2 and a broadened singlet from SCH2. When
the integrals of the aromatic 13C resonances are com-
pared with those of the methylene groups, it is seen that
each of the two 1:2:1 triplets from Cortho and Cmeta
integrates to four carbon nuclei. Among the plausible
explanations for the presence of two virtual triplets for
Cipso, Cortho and Cmeta instead of just the expected one, and
likewise two singlets for Cpara, we tend to believe that
each of the triplets/singlets results from the pair of phenyl
rings positioned on the same side of the least-squares
donor atom plane. Thus, the two phenyl rings on each
phosphine could be chemically non-equivalent due to
variations in the close environment resulting from one of
the phenyl rings being in the close proximity of the
monodentate ligand occupying the fourth coordination
site. The spectra of [Pt(PSP)Cl]ClO4 (1a) in DMSO-d6 at
20, 50 and 80°C all show the same pattern of virtual 1:2:1
triplets and broadened singlet, therefore suggesting a
13C{1H} NMR spectra of the free PSP ligand and the
complexes 1a–7 have been recorded and the results are
presented in Table 8. In the spectrum of the free ligand
all the carbon resonances appear as doublets due to
coupling with 31P, except that of the phenyl ring Cpara
which is seen as a singlet.
,
In all the complexes, except [Pt(PSP)(PPh3)](ClO4)2
(7), the 13C{1H} resonances of PCH2 and the phenyl ring
carbons Cipso, Cortho and Cmeta are seen as 1:2:1 triplets
and SCH2 and Cpara as single lines, broadened due to
unresolved couplings. We believe that the most probable
explanation for this splitting of the 13C{1H} resonances
is the virtual coupling of the trans phosphine system. The
observation of 13C{1H} 1:2:1 triplets in platinum and
palladium bis-phosphine complexes is known to indicate
that the two identical phosphines are in trans position
n
[21,43,44]. The magnitude of the ꢀ J(PC)+n+2J(P%C)ꢀ
coupling constants are in accordance with those reported
for other 13C virtual triplets in Pt(II) trans phosphine
complexes [44,45]. Due to the presence of one more
I=1/2 nucleus a similar 1:2:1 pattern is not observed in
the spectrum of complex 7. The resonances of Cipso, Cortho

162
L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
Fig. 5. 13C{1H} NMR spectrum of [Pt(PSP)Cl]ClO4 (1a) in CDCl3, showing the resonances in the aromatic region of the spectrum.
consistent with these crystal data and show that for all
the complexes, including those containing the very trans
labilizing CN− and PPh3, all three donor atoms of PSP
are bonded to platinum. Furthermore, the data strongly
indicate that the conformations of the fused chelate
rings also persist in solution, and this may be caused by
a significant ring strain in the five-membered chelate
due to the presence of the bulky donor atoms. Such
ring strain is further reflected in the small bite angles of
the PSP ligand and in the large distortion from square
planar geometry, which is seen to be further enhanced
when chloride is replaced by iodide.
Ring strain may also be responsible for the observa-
tion that when comparing the chloro with the iodo
complex the larger trans influence of the iodide is not
reflected in an increased PtꢀS bond distance. In con-
trast, the structural data of the two complexes show
unexpectedly long Pt-halogen distances, which suggest
that the trans influence of the PSP sulfur donor is larger
than that of a monodentate thioether.
rigid conformation of the chelate rings in solution, as
was suggested from the H NMR data above.
1
In [Pt(PSP)(tu)](ClO4)2 (6) the 13C{1H} resonance
from the thiourea carbon is observed as a low intensity
singlet at l 171.8, compared with l 183.4 of the uncoor-
dinated thiourea in DMSO-d6. This deshielding (10–15
ppm) of the 13C nucleus upon coordination agrees with
data from sulfur-bonded Pt(II) thiourea complexes [46],
so our NMR data show no indication of N-bonded
thiourea. Unfortunately, the use of IR for studying the
bonding mode of thiourea in 6 was limited due to
masking from the PSP ligand of w(CS) stretching
frequencies.
In the 13C{1H} NMR spectra of 4 and 5 no reso-
nances from the coordinated SCN− or CN− ligands
were observed due to the well-known relaxation phe-
nomena [47]. 13C{1H} NMR spectra of a sample of 5
prepared as in section 2.1.5 using 90 atom% enriched
2
13C cyanide showed the 13CN triplet at l 115.0, J(PC)
1
24 Hz, and with corresponding 195Pt satellites, J(PtC)
1303 Hz, typical for cyanide coordinated to Pt(II) [47].
These observations are in accordance with IR data,
where the spectrum of [Pt(PSP)CN]ClO4 (5) showed
one w(CN) stretching frequency at 2144 cm−1, corre-
sponding to the formula and with the value found in
the normal range for cyanide coordinating to Pt(II)
[10,32,35,38].
5. Supplementary material
Atomic coordinates, bond lengths and angles and
thermal parameters for 1a and 3 have been deposited at
the Cambridge Crystallographic Data Center, deposi-
tion numbers CCDC 133384 for 1a and 133383 for 3.
4. Conclusions
Acknowledgements
The X-ray crystal structures of 1a and 3 show that
both complexes are four coordinate with the PSP ligand
tridentately coordinating through the sulfur and the
two phosphorus atoms. The spectroscopic data are
The authors wish to thank Niels Thorup, Depart-
ment of Chemistry, The Technical University of Den-
mark, who collected the X-ray data and performed the
data reduction.

L.V. Andreasen et al. / Inorganica Chimica Acta 295 (1999) 153–163
163
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Inorganic Mechanisms Discussion Group, December 1996, Uni-
versity of York, UK. To be published.
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