Chloro and acetato complexes of platinum(II) with functionalized thioethers

Article abstract of DOI:10.1016/j.ica.2004.10.014

The chloro complexes [PtCl₂(RSR′)₂] (1-10) (RSR′ = MeSCH₂C(O)OMe, 1; MeSCH₂C(O)OEt, 2; MeSCH₂C(O)Omenthyl(-), 3; MeSCH₂CH₂C(O)OMe, 4;, 5; EtSCH₂C(O)Me, 6; MeSCH(Me)C(O)Me, 7; MeSPh, 8; MeS-o-C ₆H₄Me, 9; and MeS-o-C₆H₄Et, 10) are obtained in high yield (63-90%) by reaction of [PtCl₂(PhCN) ₂] with the proper thioether in 1/2 molar ratio, in anhydrous chloroform, at reflux under argon for ca. 10 h. The X-ray crystal structure of [PtCl₂(MeS-o-C₆H₄Me)₂] (9) shows an almost regular trans square planar geometry (triclinic, space group P1?, a 6.806(1), b 7.789(2), c 10.085(3) ?, α 101.80(2)°, β 69.55(2)°, γ 115.27(2)°, R(F_o) 0.023, R _w(F_o²)0.065). The dichloro complexes react with silver acetate in a complex manner, which depends on the nature of the thioether, and only with RSR′ = MeSPh the simple diacetato complex [Pt(OAc)₂(RSR′)₂] is obtained as the major product.

Full text of DOI:10.1016/j.ica.2004.10.014

Inorganica Chimica Acta 358 (2005) 659–666
www.elsevier.com/locate/ica
Chloro and acetato complexes of platinum(II) with
functionalized thioethers
a,
Marino Basato , Annarita Cardinale , Sandra Salvo ,
a
a
*
`
a
Cristina Tubaro , Franco Benetollo
b
a
`
Dipartimento di Scienze Chimiche, Universita di Padova, and ISTM-CNR, Via Marzolo 1, I-35131 Padua, Italy
b
ICIS-CNR, Corso Stati Unii 4, I-35127 Padua, Italy
Received 5 August 2004; accepted 4 October 2004
Available online 10 December 2004
Abstract
The chloro complexes [PtCl2(RSR0)2] (1–10) (RSR0 = MeSCH2C(O)OMe, 1; MeSCH2C(O)OEt, 2; MeSCH2C(O)Omenthyl(ꢀ),
3; MeSCH2CH2C(O)OMe, 4;
, 5; EtSCH2C(O)Me, 6; MeSCH(Me)C(O)Me, 7; MeSPh, 8; MeS-o-C6H4Me, 9;
and MeS-o-C6H4Et, 10) are obtained in high yield (63–90%) by reaction of [PtCl2(PhCN)2] with the proper thioether in 1/2 molar
ratio, in anhydrous chloroform, at reflux under argon for ca. 10 h. The X-ray crystal structure of [PtCl2(MeS-o-C6H4Me)2] (9) shows
˚
ꢀ
an almost regular trans square planar geometry (triclinic, space group P1, a 6.806(1), b 7.789(2), c 10.085(3) A, a 101.80(2)°, b
69.55(2)°, c 115.27(2)°, R(Fo) 0.023, RwðF 2oÞ 0:065). The dichloro complexes react with silver acetate in a complex manner, which
depends on the nature of the thioether, and only with RSR0 = MeSPh the simple diacetato complex [Pt(OAc)2(RSR0)2] is obtained
as the major product.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Platinum complexes; Thioether complexes; Chloro complexes; Acetato complexes; b-Oxothioethers
1. Introduction
particular synthetic procedure, so that the same com-
pounds are obtained by reacting the monomeric chloro
complexes [PdCl2(RSCH2C(O)R0)2] with two equiva-
lents of silver acetate, without any evidence for the
formation of the expected substitution products
[Pd(OAc)2(RSCH2C(O)R0)2] [5].
For all the outlined aspects, the coordinating proper-
ties of the oxothioether ligands towards the palla-
dium(II) centre appear rather peculiar, so it seemed
worthwhile to investigate if they are general or depend
on the particular metal involved.
We report here the results on the reaction of
[PtCl2(PhCN)2] and [Pt4(OAc)8] with a fairly large series
of thioether ligands (RSR0, Scheme 1) and on the reac-
tivity of the chloro complexes [PtCl2(RSR0)2] towards
silver acetate. The ligand set includes aryl thioethers,
which in principle can give o-metalation [6,7].
We have recently found that thioether ligands bearing
an oxo substituent in a-position react with [Pd(OAc)2]
to give trimeric complexes of the type [Pd3(l-OAc)3(l-
RSCHC(O)R0-C,S)3 [1,2]. This reaction has many inter-
esting aspects, for example: (i) the exchange reaction ap-
plies only to half of the acetato groups; (ii) the bidentate
anionic thioether is coordinated via chiral sulfur and
methine carbon atoms; (iii) the oxo group is not in-
volved in a chelate five-member coordination, in con-
trast to what is observed with b-ketophoshines or
b-ketoamines [3,4]. Furthermore, it has been proved that
the formation of these trimers does not depend on the
*
Corresponding author. Tel.: +39 49 8275216; fax: +39 49 8275223.
E-mail address: marino.basato@unipd.it (M. Basato).
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.10.014

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M. Basato et al. / Inorganica Chimica Acta 358 (2005) 659–666
O
O
O
MeS
EtS
C
O
Menthyl(1R,2S,5R)
MeS
MeS
MeS
C
O
Me
MeS
C
O
Et
O
O
S
Me
C
Me
C
C
O
CH
OEt
O
Me
SMe
R
Me
C
O
R= H,Me, Et
Scheme 1.
3
2. Experimental
2.1. Reagents and apparatus
CH3CH2, JHH = 7.6 Hz), 2.01 (cm, 4H, 2CH2 in the
ring), 2.87 (cm, 2H, SCH2), 3.92 (q, 2H, CH3CH2,
3JHH = 7.6 Hz).
The reagents (Aldrich-Chemie) were high purity
products and generally used as received. Solvents were
dried before use and the reaction apparatus carefully
deoxygenated. Reactions were performed under argon
and all operations were carried out under an inert atmo-
sphere. The solution 1H and 13C{1H} NMR spectra
were recorded on a Jeol FX90Q spectrometer (89.55
2.2.3. MeS-o-C6H4R (R = Me or Et)
They were prepared by reaction of the proper thiol
with MeI in ethanol, in the presence of one equivalent
1
of NaOH. MeS-o-C6H4Me (yield 92%): H NMR (in
CDCl3): d = 2.31 and 2.40 (2s, 6H, CH3Ph and CH3S),
7.00–7.28 (m, 4H, C6H4). MeS-o-C6H4Et (yield 90%):
1H NMR (in CD2Cl2): d = 1.38 (t, 3H, CH3CH2), 2.53
(s, 3H, CH3S), 2.87 (q, 2H, CH3CH2), 7.10–7.32 (m,
4H, C6H4). 13C NMR (in CD2Cl2): d = 14.6 (CH3CH2),
15.8 (CH3S), 27.1 (CH3CH2), 125.4–142.2 (C6H4).
1
MHz for H and 22.63 MHz for 13C) or on a Bruker
1
DRX 400 (400.13 MHz for H and 100.63 MHz for
13C). The solution spectra were recorded at room tem-
perature dissolving the samples in CDCl3. The chemical
shifts are reported versus tetramethylsilane and were
determined by reference to the residual solvent peaks,
using tetramethylsilane as internal standard. The FT
IR spectra were recorded on a Biorad FT S7 PC spectro-
photometer at 2 cmꢀ1 resolution in KBr disks or on a
Nicolet 20 F in Nujol mull for the far infrared.
2.2.4. EtSCH2C(O)Me
It was prepared by reaction in ethanol of
ClCH2C(O)Me with the sodium salt EtSNa, prepared
in situ from the thiol and sodium ethoxide [8].
2.3. Synthesis of the complexes
2.2. Synthesis of the ligands
2.3.1. Synthesis of the platinum(II) chlorocomplexes
[PtCl2(RSR0)2] (1–10)
2.2.1. MeSCH2C(O)Omenthyl(ꢀ)
Complexes 1–10 were obtained by reaction of
[PtCl2(PhCN)2] with the appropriate thioether in 1/2 mo-
lar ratio, in anhydrous chloroform, at reflux under argon.
[PtCl2(MeSCH2C(O)OMe)2] (1). In this prototype
reaction, [PtCl2(PhCN)2] (0.59 g, 1.25 mmol) was dis-
solved in chloroform (20 ml) and the resulting solution
was additioned with MeSCH2C(O)OMe (0.27 ml, 0.30
g, 2.5 mmol). The reaction mixture was heated at reflux
under stirring for 10 h, cooled to room temperature and
evaporated to small volume under reduced pressure.
Treatment with diethylether afforded a white solid,
This chiral ester was synthesized by reacting
(1R,2S,5R)-(ꢀ)-menthol with MeSCH2C(O)Cl as previ-
ously reported [1]
2.2.2.
This cyclic thioether was prepared from 2-cyanotetra-
hydrothiophene by its hydrolysis in HCl solution to tet-
rahydrothiophene carboxylic acid, followed by
esterification in ethanol to ethyl 2-tetrahydrothiophene
carboxylate. 1H NMR (in CDCl3): d = 1.19 (t, 3H,

M. Basato et al. / Inorganica Chimica Acta 358 (2005) 659–666
661
3
which was left under stirring for one day, filtered and
dried under vacuum (0.46 g, 73%); m.p. 90 °C. Anal.
Calc. for C8H16Cl2O4PtS2, MW = 506.73: C, 18.96; H,
3.18; S, 12.65. Found: C, 19.14; H, 3.08; S, 12.95%. H
NMR (in CDCl3): d = 2.58 (s, 3H, CH3S,
3JPtH(trans) = 43.0 Hz), 3.79 (s, 3H, CH3O), 3.85 (s,
3
CH2S, JPtH(trans) = 28.1 Hz), plus low intensity peaks
CH3S, JPtH(cis) = 49.7 Hz), 3.52 (cm, 2H, CH2CH2),
3.74 (s, 3H, OCH3). 13C NMR (in CDCl3): d = 20.1
(CH3S), 32.0 and 32.8 (SCH2CH2), 52.1 (OCH3), 170.9
(C(O)O). FTIR [cmꢀ1, KBr]: 1730 [m(C@O)].
1
(5). Pale yellow solid,
S(CH ) CHC(O)OEt
)2]
[PtCl2(
2 3
yield 66%, m.p. 88 °C. Anal. Calc. for C14H24Cl2O4PtS2,
MW = 586.46: C, 28.67; H, 4.12; S, 10.93. Found: C,
27.46; H, 3.98; S, 10.56%. 1H NMR (in CDCl3):
(approximate ratio 1/20) at: 2.67 (s, CH3S,
3JPtH(cis) = 49.2 Hz) and 4.13 (s, CH2S). The spectrum
changes with time, so that the intensity of the two sets
of peaks is roughly the same after two weeks at
room temperature or by heating the solution for 1 h
at 50 °C. 13C NMR (in CDCl3): d = 20.62 (CH3,
3
d = 1.30 (t, 3H, CH3CH2, JHH = 7.0 Hz), 2.22, 2.32
and 2.44 (3 cm, 4H, 2 CH2 in the ring), 3.08 and 3.75
3
(brs, 2H, SCH2), 4.21 (q, 2H, CH2CH3, JHH = 7.0
Hz), 4.95 (t, 1H, SCH, JHH = 5.4 Hz). 13C NMR (in
3
CDCl3): d = 14.0 (CH3CH2), 30.0, 33.2 and 39.6 (CH2
in the ring), 52.8 (SCH), 62.2 (CH2CH3), 170.2
(C(O)O). FTIR [cmꢀ1, KBr or Nujol (in the far infra-
red)]: 1730 [m(C@O)], 370, 358, 346, 294.
[PtCl2(EtSCH2C(O)Me)2] (6). Two days at reflux,
white solid, yield 61%, m.p. 213 °C. Anal. Calc. for
C10H20Cl2O2PtS2, MW = 502.38: C, 23.91; H, 4.01; S,
2
2JPtC(trans) = 11.72 Hz), 38.96 (CH2, JPtC(trans) = ca. 9
Hz), 40.23 (CH2), 52.81 (CH3O), 166.38 (C(O)O,
3
3JPtC(trans) = 43.2 Hz), 166.74 (C(O)O, JPtC(cis) = 30.8
Hz). FTIR [cmꢀ1, KBr or Nujol (in the far infrared)]:
1738 [m(C@O)], 346 [m(Pt–Cl)] and 322 cmꢀ1 [m(Pt–S)].
[PtCl2(MeSCH2C(O)OEt)2] (2). White solid, yield
91%, m.p. 104 °C. Anal. Calc. for C10H20Cl2O4PtS2,
MW = 534.36: C, 22.48; H, 3.77; S, 12.0. Found: C,
22.74; H, 3.74; S, 12.33%. 1H NMR (in CDCl3):
1
12.76. Found: C, 23.89; H, 3.90; S, 13.05%. H NMR
3
(in CDCl3): d = 1.43 (t, 3H, CH3CH2, JHH = 7.3 Hz),
2.31 (s, 3H, CH3), 2.94 (cq, CH2CH3, JHH = 7.3 Hz),
3
3
3
d = 1.32 (t, 3H, CH3CH2 JHH = 7.3 Hz), 2.60 (s, 3H,
CH3S, JPtH(trans) = 42.5 Hz), 3.85 (s, 2H, SCH2,
3.89 (s, CH2S, JPtH = 32.7 Hz). 13C NMR (in CDCl3):
3
3
d = 12.82 (CH3CH2 JPtC = 22.8 Hz), 29.43 (CH3C(O)),
31.28 (CH3CH2, JPtC = 11.0 Hz), 44.81 (CH2S,
3
2
3JPtH(trans) = 25.4 Hz), 4.25 (q, 2H, CH2CH3, JHH
=
7.3 Hz). The solution after two days shows an additional
2JPtC = 8.2 Hz), 199.71 (CH3C(O), JPtC = 30.6 Hz).
3
peak at 2.67 (s, 3H, CH3S, JPtH(cis) = 48.8 Hz). 13C
FTIR [cmꢀ1, KBr or Nujol (in the far infrared)]: 1717
3
NMR (in CDCl3): d = 13.99 (CH3CH2), 20.78 (CH3S,
[m(C@O)], 340 [m(Pt–Cl)] and 305 cmꢀ1 [m(Pt–S)].
2JPtC(trans) = 12.2 Hz), 39.35 (SCH2 JPtC(trans) = 7.4
[PtCl2(MeSCH(Me)C(O)Me)2] (7). Yellow solid,
yield 66%, m.p. 109 °C. Anal. Calc. for C10H20Cl2O2PtS2,
MW = 502.38: C, 23.91; H, 4.01; S, 12.76. Found: C,
22.85; H, 3.80; S, 13.73%. 1H NMR (in CDCl3):
d = 1.65 (d, 3H, SCH(CH3), JHH = 6.8 Hz), 2.34 (s,
3H, CH3S, JPtH = 41.7 Hz), 2.44 (s, 3H, C(O)CH3),
4.39 (q, 1H, SCH(CH3), JHH = 6.8 Hz). 13C NMR (in
CDCl3): d = 14.9 (SCH(CH3)), 28.5 (CH3S and
CH3C(O)), 52.6 (SCH(CH3)), 202.9 (CH3C(O)). FTIR
[cmꢀ1, KBr or Nujol (in the far infrared)]: 1711
[m(C@O)], 335 [m(Pt–Cl)] and 298 cmꢀ1 [m(Pt–S)].
2
Hz), 40.76 (low intensity, SCH2), 62.20 (CH2CH3),
166.03 (C(O)O, 3JPtC(trans) = 44.7 Hz), 166.42 (low inten-
2
sity, C(O)O, JPtC(cis) = 33.7 Hz). FTIR [cmꢀ1, KBr or
3
Nujol (in the far infrared)]: 1722 [m(C@O)], 335 [m(Pt–
Cl)], 302 [m(Pt–S)].
3
3
[PtCl2(MeSCH2C(O)Omenthyl(ꢀ))2] (3). Pale
yellow solid, yield 76%, m.p. 149 °C. Anal. Calc. for
C26H48Cl2O4PtS2, MW = 754.78: C, 41.37; H, 6.41; S,
1
8.49. Found: C, 41.17; H, 6.18; S, 9.09%. H NMR (in
CDCl3, menthyl ¼ CHð1ÞCHð2Þ½CHð3ÞðCH3Þ ð4;5ÞꢁCH2
6
2
CH2ð7ÞCHð8ÞðCH3ð9ÞÞCH2ð10Þ): d = 0.78 to 2.18 (18H, al-
[PtCl2(MeSPh)2] (8). Pale yellow solid [9], yield
1
kyl protons of the menthyl group), 2.59 (s, 3H, CH3S,
3JPtH = 39.0 Hz), 3.79 and 3.90 (unresolved AB quartet,
2H, SCH2), 4.78 (td, 1H, OCH menthyl, JHH = 10.9 and
4.3 Hz). 13C NMR (in CDCl3): d = 16.1 (4), 20.7 (5),
20.9 (CH3S), 21.9 (9), 23.2 (6), 26.1 (3), 31.3 (8), 34.0
(7), 39.6 (SCH2), 40.6 (10), 46.8 (2), 76.8 (1), 165.7
(C(O)O). FTIR [cmꢀ1, KBr or Nujol (in the far infra-
red)]: 1729 [m(C@O)], 351 [m(Pt–Cl)], 303 [m(Pt–S)].
[PtCl2(MeSCH2CH2C(O)OMe)2] (4). Yellow so-
lid, yield 63%, m.p. 67 °C. Anal. Calc. for
C10H20Cl2O4PtS2, MW = 534.36: C, 22.48; H, 3.77; S,
77%, m.p. 123 °C. H NMR (in CDCl3): d = 2.67 and
2.77 (2s, 1.7 + 1.3H, CH3S, JPtH(trans) = 42.4 Hz and
3
3JPtH(cis) = 47.0 Hz), 7.34–7.83 (m, 5H, Ph). 13C NMR
(in CDCl3): d = 22.6 (CH3S(trans)), 23.5 (CH3S(cis)),
129.8, 129.9, 130.6, 131.1, 131.6 (Ph). FTIR [cmꢀ1
,
KBr or Nujol (in the far infrared)]: 1576 [m(CC ring)],
340 [m(Pt–Cl)] and 327 cmꢀ1 [m(Pt–S)].
[PtCl2(MeS-o-C6H4Me)2] (9). Pale yellow solid [9],
1
yield 80%, m.p. 149 °C. H NMR (in CDCl3): d = 2.60
(s, 3H, CH3Ph), 2.65 (s, 3H, CH3S, JPtH(trans) = 43.0
Hz), 2.70 (s, 3H, CH3S, JPtH(cis) = 47.8 Hz), 7.26–7.95
(m, 4H, C6H4). 13C NMR (in CDCl3): d = 21.0 and 21.8
(CH3S and CH3Ph), 127.0, 130.0, 130.7, 130.8, 132.2,
139.1 (C6H4). FTIR [cmꢀ1, KBr or Nujol (in the far infra-
red)]: 1588 [m(CC ring)], 333 [m(Pt–Cl)] and 297 cmꢀ1
[m(Pt–S)].
3
3
1
12.00. Found: C, 21.38; H, 3.52; S, 12.60%. H NMR
3
(in CDCl3): d = 2.47 (s, 3H, CH3S, JPtH(trans) = 40.6
Hz), 2.92 (t, 2H, SCH2CH2, JHH = ca. 7.0 Hz), 3.15
(bm, 2H, SCH2CH2), 3.73 (s, 3H, OCH3). The solution
after two months shows additional peaks at 2.60 (s, 3H,

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M. Basato et al. / Inorganica Chimica Acta 358 (2005) 659–666
[PtCl2(MeS-o-C6H4Et)2] (10). Pale yellow solid,
ature for 1 week. The formed silver chloride was filtered
off and the solution evaporated to small volume under re-
duced pressure. Treatment with diethylether afforded the
pale yellow complex [Pt(OAc)2(MeSPh)2] (13), which was
filtered and dried under vacuum (0.27 g, 80%), m.p.
104 °C. Anal. Found: C, 38.32; H, 3.79; S, 11.18%. Calc.
for C18H22O4PtS2, MW = 561.58: C, 38.50; H, 3.95; S,
11.42%. 1H NMR (in C2D2Cl4): d = 2.01 (s, 3H,
yield 79%, m.p. 118 °C. Anal. Calc. for C18H24Cl2PtS2,
MW = 570.51: C, 37.89; H, 4.25; S, 11.24. Found: C,
36.26; H, 4.04; S, 10.50%. 1H NMR (in CDCl3):
3
d = 1.28 (t, 3H, CH2CH3 JHH = 7.4 Hz), 2.64 (s, 3H,
CH3S, JPtH(trans) = 41.4 Hz), 2.72 (s, 3H, CH3S,
3
3
3JPtH(cis) = 49.5 Hz), 2.97 (q, 2H, CH2CH3, JHH = 7.4
Hz), 7.13–8.05 (m, 4H, C6H4). 13C NMR (in CDCl3):
3
d = 15.5 (CH3CH2), 22.8 (CH3S), 27.2 (CH3CH2),
CH3COOꢀ), 2.48 (s, 3H, CH3S, JPtH(trans) = 44.0 Hz),
127.1, 129.2, 130.4, 133.2, 145.1 (C6H4). FTIR [cmꢀ1
,
7.27–7.70 (m, 5H, Ph). 13C NMR (in C2D2Cl4): d = 22.9
and 23.1 (CH3COOꢀ and CH3S), 129.3, 130.7 and 130.9
(Ph), 177.1 (CH3COOꢀ). NMR in CDCl3 of the isomer-
KBr or Nujol (in the far infrared)]: 1592 [m(CC ring)],
347 [m(Pt–Cl)] and 320 cmꢀ1 [m(Pt–S)].
1
ised complex ca. 1/1 cis/trans ratio, H: d = 2.04 (s, 6H,
2.4. Reaction of the chloro complexes with silver acetate
CH3COOꢀ), 2.49 (s, 3H, CH3S), 2.53 (s, 3H, CH3S),
7.20–7.90 (m, 10H, Ph); 195Pt: d = ꢀ2925 (s), ꢀ2942 (s)
vs. d ([PtCl6]2ꢀ) = 0 ppm. FTIR [cmꢀ1, KBr]: 1579 and
1408 ½mðCO2ꢀÞꢁ.
2.4.1. Reaction of [PtCl2(MeSCH2C(O)OEt)2] (2)
with Ag(OAc): synthesis of [Pt(OAc)(O2CCH2SMe)-
(MeSCH2C(O)OEt)] (11) and of [Pt(O2CCH2-
SMe)2] (12)
2.4.3. Reaction of [PtCl2(MeS-o-C6H4Me)2] (9) with
Ag(OAc)
[PtCl2(MeSCH2C(O)OEt)2] (2) (0.50 g, 0.94 mmol)
was dissolved in dichloromethane (20 ml) and the result-
ing solution was additioned with Ag(OAc) (0.31 g, 1.88
mmol). The suspension was left under stirring in the dark
at room temperature for 1 d. The formed silver chloride
was filtered off and the solution evaporated to small vol-
ume under reduced pressure. Treatment with n-hexane
afforded the white complex [Pt(OAc)(O2CCH2SMe)(-
MeSCH2C(O)OEt)] (11), which was filtered and dried un-
der vacuum (0.14 g, 32%). Anal. Calc. for C10H18O6PtS2,
MW = 461.15: C, 24.34; H, 3.68; S, 13.00. Found: C,
23.56; H, 3.45; S, 13.60%. 1H NMR (in DMSO-d6):
[PtCl2(MeS-o-C6H4Me)2] (9) (0.20 g., 0.36 mmol) was
dissolved in dichloromethane (20 ml) and the resulting
solution was additioned with Ag(OAc) (0.12 g, 0.72
mmol). The suspension was left under stirring in the dark
atroom temperaturefor1week. Theformedsilverchloride
(0.3 mmol) was filtered off and the solution evaporated to
small volume under reduced pressure. Treatment with
diethylether afforded an orange solid, which was filtered
and dried under vacuum (0.02 g), m.p. 122 °C. Anal.
Found: C, 32.89; H, 3.64; S, 6.16, Pt, 35.84 %. 1H NMR
(in C2D2Cl4): d = 1.9–2.8 (very broad band with many
3
d = 1.18 (t, 3H, CH3CH2, JHH = 7.2 Hz), 1.85 (s, 3H,
merging peaks, methyls), 7.0-8.2 (Ar, approximate Halif/
Harom ratio 2). 13C NMR (in C2D2Cl4): d = 14–24 (meth-
yls), 126–132 (Ar). 195Pt NMR (in CDCl3): d = ꢀ2900
CH3SCH2COOꢀ), 2.11 (s, 3H, CH3COOꢀ), 2.59 (s, ca.
3
3H, CH3SCH2COOEt, JPtH = 53.2 Hz), 3.26, 3.64 and
3.84 (ca. 4H, SCH2), 4.09 (q, 2H, CH3CH2, 3JHꢀH = 7.08
Hz). 13C NMR (in DMSO-d6): d = 14.10 and 15.53
(CH3CH2), 23.01 and 23.69 (CH3SCH2COOꢀ,
CH3SCH2COOEt and CH3COOꢀ), 60.66 (CH3CH2),
170.01 (C(O)OEt), 175.72 (CH3SCH2COOꢀ), 178.92
(CH3COOꢀ). FTIR [cmꢀ1, KBr]: 1732 [m(C@O), ester],
1665, 1626, 1576 and 1412 ½mðCO2ꢀÞꢁ.
(s), ꢀ2934 (s) vs. d([PtCl6]2ꢀ) = 0 ppm. FTIR [cmꢀ1
,
KBr]: 1632, 1612 and 1421 ½mðCO2ꢀÞꢁ. The ESI mass spec-
trum shows a base peak at 470.1 m/z. Its isotopic pattern is
consistent with that of the ion [Pt(MeS-o-C6H4Me)(MeS-
o-C6H4Me(–H))]+. This ion in MS2 conditions undergoes
successive losses of CH3 (455.1 and 440.2 m/z). In the
ESI spectrum is present also a peak at 558.8 attributable
to [Pt(OAc)2(MeS-o-C6H4Me(–Me))2]+ and the related
peak at 499.0 m/z resulting from the loss of one molecule
of acetic acid.
Complex 11 (125 mg) was suspended in dichlorome-
thane under stirring for one day. The unreacted 11 (85
mg) was filtered off and the solution reduced to small
volume to give the white insoluble complex
[Pt(O2CCH2SMe)2] (12) (35 mg), m.p. 258 °C. Anal.
Calc. for C6H10O4PtS2, MW = 405.44: C, 17.77; H,
2.49; S, 15.81. Found: C, 17.54; H, 2.27; S, 16.29%.
FTIR [cmꢀ1, KBr]: 1662 and 1418 ½mðCO2ꢀÞꢁ.
The solution resulting from the filtration of the orange
solid slowly produced a precipitate, which on treatment
with acetone gave an insoluble yellow solid, which was
identified as cis-[Pt(OAc)2(MeS-o-C6H4Me)2] on the basis
1
of its H NMR spectrum (in CD2Cl2): d = 1.49 (s, 3H,
3
CH3COOꢀ), 2.59 (s, 3H, CH3S, JPtH(cis) = 53.0Hz),
2.63 (s, 3H, CH3C6H4), 7.1–7.9 (m, 4H, Ar).
2.4.2. Reaction of [PtCl2(MeSPh)2] (8) with Ag(OAc):
synthesis of [Pt(OAc)2(MeSPh)2] (13)
[PtCl2(MeSPh)2] (8) (0.30 g., 0.60 mmol) was dissolved
in dichloromethane (20 ml) and the resulting solution was
additioned with Ag(OAc) (0.20 g, 1.20 mmol). The sus-
pension was left under stirring in the dark at room temper-
2.5. Reaction of [Pt4(OAc)8] with thioethers
The reactions of [Pt4(OAc)8] with MeSCH2C(O)OEt,
MeSPh, MeS-o-C6H4Me, and MeSCH2SMe were con-

M. Basato et al. / Inorganica Chimica Acta 358 (2005) 659–666
663
ducted in dichloromethane or acetic acid, using variable
3. Results and discussion
Pt/thioether ratios (1/1–1/2), temperatures (from room
to boiling acetic acid), and times (hours to days). In
all these cases, no definite complexes could be isolated
from the reaction mixtures, whose thioether content
simply increases with more forcing experimental condi-
tions, without reaching a fixed stoichiometry.
The employed sulfur ligands RSR0 have generally
shown good coordinating properties towards
platinum(II); the nature and stability of the resulting
complexes strongly depend on the type of starting
platinum(II) compound. Both classes of investigated
thioethers are characterized by the presence of C–H
acidic carbon atoms: in the first one, the presence of
electron withdrawing groups as esters or ketones
increases the acidity of the methylene in alfa position;
in the second one, the coordination of the sulfur
atom to the metal centre should favour the o-
metalation of the aromatic ring or of its alkyl
substituent.
2.6. X-ray measurements and structure determination of
[PtCl2(MeS-o-C6H4Me)2]
Single crystals suitable for X-ray analysis were ob-
tained by slow precipitation from a CDCl3 solution in
a NMR tube. The intensities data of [PtCl2(MeS-o-
C6H4Me)2] were collected at room temperature using a
Philips PW1100 single-crystal diffractometer (FEBO sys-
tem) using a graphite-monochromated (Mo Ka) radia-
tion, following the standard procedures. There were no
significant fluctuations of intensities other than those ex-
pected from Poisson statistics. All intensities were cor-
rected for Lorentz polarization and absorption [10].
The structure was solved by heavy atom method [11].
Refinement was carried out by full-matrix least-squares
procedures (based on F 2o) using anisotropic temperature
factors for all non-hydrogen atoms. The H-atoms were
placed in calculated positions with fixed, isotropic ther-
mal parameters (1.2Uequiv of the parent carbon atom).
The calculations were performed with the SHELXL-97
program [12], implemented in the WinGX package
[13], drawings were produced using ORTEP3 [14]. Crys-
tallographic and experimental details for the structure
are summarized in Table 1.
The thioether ligands react with [PtCl2(PhCN)2] to
give always almost quantitative formation of the substi-
tution products [PtCl2(RSR0)2], whereas the reaction
with [Pt4(OAc)8] generally produces mixtures of prod-
ucts with variable degree of ligand exchange.
The chloro complexes [PtCl2(RSR0)2] (1–10)
(RSR0 = MeSCH2C(O)OMe, 1; MeSCH2C(O)OEt, 2;
MeSCH2C(O)Omenthyl(ꢀ), 3; MeSCH2CH2C(O)OMe,
4;
, 5; EtSCH2C(O)Me, 6; MeSCH-
(Me)C(O)Me, 7; MeSPh, 8; MeS-o-C6H4Me, 9; and
MeS-o-C6H4Et, 10) are obtained by reaction of
[PtCl2(PhCN)2] with the proper thioether in 1/2 molar
ratio, in anhydrous chloroform, at reflux under argon
for ca. 10 h. The complexes are isolated by volume
reduction and treatment with diethyl ether (yields 63–
90%).
1
The H and 13C NMR spectra are consistent with
the coordination of the thioether ligand and the
occurrence of two geometric isomers. The resonances
of the methyl protons are in a narrow range of chem-
ical shift (2.34–2.77 ppm) and at lower fields with re-
spect to the free ligand, as the consequence of a
reduced electron density on the coordinated sulfur.
The coupling with 195Pt (I = 1/2, ca. 33% isotopic
abundance) gives rise to the typical satellites. One un-
ique set of signals is observed at room temperature for
Table 1
Crystal data of [PtCl2(MeS-o-C6H4Me)2]
Compound
[PtCl2(MeS-o-C6H4Me)2]
C16H20Cl2PtS2
542.43
Chemical formula
Formula weight
Crystal system
triclinic
ꢀ
Space group
Unit cell dimensions
P1
˚
a (A)
6.806(1)
7.789(2)
10.085(3)
101.80(2)
69.55(2)
115.27(2)
452.6(2)
1
solutions in CDCl3 of the complexes 3, 5,
6
˚
b (A)
(3JPtH(trans) = 39.0–43.0 Hz), whereas for the other
complexes a second set of signals with higher coupling
constants (3JPtH(cis) = 47.1–49.5 Hz) is slowly emerging
with time (days) as the result of a trans–cis conversion
[9].
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
The proton NMR spectrum is more complicated in 3,
due to the presence of the chiral menthyl substituent.
The resonance of the methylene protons appears as a
singlet at 3.84 ppm with the two satellites (90 MHz,
3JPtH = 24.0 Hz), so this part of the spectrum is similar
to that observed for the non-chiral [PtCl2(MeSCH2-
C(O)OR)2] (R = Me (1) or Et (2)). If the same spectrum
is recorded at 400 MHz, the two more intense signals of
an AB quartet (centred at 3.845 ppm) are observed. The
T (°C)
293(2)
1.990
260
Dcalc (g cmꢀ3
F(000)
)
l(Mo Ka) (mmꢀ1
Number of reflections collected
Number of observed [I P 2r(I)]
R(Fo)
)
8.27
2770
2626
0.023
RwðF 2oÞ
0.065
1.111
Goodness-of-fit
P
P
P
P
2
2
1=2
R ¼ jF oj ꢀ jF cj= jF oj; Rw ¼ f ½wðF 2o ꢀ F c2Þ ꢁ= ½wðF o2Þ ꢁg
.

664
M. Basato et al. / Inorganica Chimica Acta 358 (2005) 659–666
˚
the coordination plane. The Pt–Cl (2.307(1) A) and the
˚
Pt–S (2.307(1) A) bond lengths compare well with those
found in trans-dichloro-bis(1,4-thioxane)platinum(II)
˚
[15] (Pt–Cl 2.300(2) and Pt–S 2.298(2) A), and reported
in trans-dichloro-bis-(tetrahydrothiophene)platinum(II)
˚
[16] (Pt–Cl 2.309(2), Pt–S 2.305(2) A). There is also a rel-
presence of a quartet is expected, as the chiral menthyl
substituent makes the two methylene protons diastereo-
topic, but one quartet is experimentally observable only
at this higher frequency, when the inversion of configu-
ration of the coordinated sulfur becomes comparatively
slow, and, as the consequence, also the sulfur atom be-
haves as a chiral centre. In fact, as noted in the case of
the corresponding palladium complex [5], the effect of
the chirality of the menthyl group is limited and pro-
duces only very small differences in the chemical shifts
of the two diastereoisomers (+ꢀ) and (ꢀꢀ). Therefore,
the two large signals centred at 3.845 ppm are attribut-
able to the two more intense peaks of AB quartets (and
related 195Pt satellites) of the possible stereoisomers,
having chemical shifts practically coincident.
The 13C NMR spectra are consistent with the pro-
tonic ones; in particular, they show two sets of signals
in the presence of a trans/cis mixture and an almost
invariant value of the chemical shift for the ester or keto
carbon atom with respect to the free ligand.
The NMR data indicate that the complexes, which
are isolated as trans isomers with our synthetic proce-
dure, slowly evolve in CDCl3 solution to a cis form in
equilibrium with the initial trans.
The whole of these data is confirmed by the X-rays
structure of [PtCl2(MeS-o-C6H4Me)2] (9). Its structure
consists of discrete molecule with the platinum atom ly-
ing on a centre of symmetry. The asymmetric unit is
formed by half molecule of [PtCl2(MeS-o-C6H4Me)2]
complex. A perspective view of the molecule is reported
in Fig. 1 with the significant geometrical parameters.
The metal coordination is trans–planar (for the sake of
crystallographic symmetry) with different angles for S–
Pt–Cl and S0–Pt–Cl of 94.85(5)° and 85.15(5)°, respec-
tively. This may arise from the greater steric repulsion
of the chloride atoms towards the methyl group on
C(8) compared with the aryl ring. This last one, in fact,
in order to minimize its steric hindrance towards both
the chloride atoms and the methyl C(8) group, adopts
a pseudoaxial position forming an angle of 87.6(1)° with
atively short intermolecular contact between00Cl and the
˚
proton of the methyl H(7C)–Cl 2.865(2) A, Cl ꢂ ꢂ ꢂH(7C)–
C(7) 171.1(3)°) (00 at x,y,1 ꢀ z) with the formation of
chain running in the c-axis direction (Fig. 2).
The reactivity of the chloro complexes [PtCl2(RSR0)2]
with Ag(OAc) depends markedly on the type of coordi-
nated ligands.
A different behaviour is shown by complexes with li-
gands having ester or keto substituents compared with
the aryl ones. For example, [PtCl2(MeSCH2C(O)OEt)2]
(2) gives as final product [Pt(O2CCH2SMe)2], in which
the ligand has undergone hydrolysis of the ester group
(Scheme 1). The compound is very insoluble and proba-
bly has an oligomeric structure in which both oxygen
and sulfur atoms can coordinate the metal centre.
Complex 7, whose ligand MeSCH(Me)C(O)Me has a
keto function, is less reactive towards silver acetate;
however, prolonged reaction times give mixtures of
complexes, whose low C/S ratio (3.7) only suggests ex-
tended fragmentation of the thioether ligand.
The reaction of [PtCl2(MeSAr)2] complexes gives,
when Ar = Ph, the simple exchange product [Pt(OAc)2-
(MeSPh)2] (13). The compound is stable in the solid
state and in solution. The 1H NMR spectrum in
C2D2Cl4 solution shows only the trans species
(3JPtH = 44.0 Hz), which slowly evolves to a cis–trans
mixture. Moreover, there are no evidences of ortho-
metalation, which should be favoured by the presence
of the coordinated acetato.
The same reaction with the closely related complex 9
(Ar = o-C6H4Me) affords the simple Clꢀ/OAcꢀ ex-
change compound [Pt(OAc)2(MeS-o-C6H4Me)2] only
in very low yield. The major product is an orange solid,
whose composition cannot be safely defined in spite of
˚
Fig. 1. ORTEP view of [PtCl2(MeS-o-C6H4Me)2] (9) with 50% thermal ellipsoids probability. Relevant bond lengths (A) and angles (°): Pt–Cl
2.307(1), Pt–S 2.305(1), S–C(1) 1.790(4), S–C(8) 1.809(7); Cl–Pt–S 94.85(5), Cl–Pt–S0 85.15(5), Pt–S–C(1) 104.5(2), Pt–S–C(8) 112.3(2), C(1)–S–C(8)
101.0(3) (0 at ꢀx,ꢀy,ꢀz).

M. Basato et al. / Inorganica Chimica Acta 358 (2005) 659–666
665
Fig. 2. Formation of chain running in the c-axis direction in complex [PtCl2(MeS-o-C6H4Me)2] (9).
extensive characterization by elemental analysis, infra-
RR'S
Cl
Cl
PhCN
Cl
Cl
+ 2RSR'
- 2PhCN
red, NMR and mass spectroscopy. In fact, the 195Pt
NMR spectrum shows two signals of almost identical
intensity at ꢀ2900 and ꢀ2934 ppm, at chemical shift
values very close to those of the related cis- and trans-
Pt
Pt
SRR'
NCPh
+ 2 Ag(OAc)
- 2 AgCl
1
[Pt(OAc)2(MeSPh)2]. By contrast, the H and 13C spec-
tra show a very complex pattern in the methyl region,
thus indicating the presence of a much more complex
structure or of a mixture of compounds. The elemental
analysis data do not help in this regard, since they indi-
cate a Pt/S 1/1 ratio. Complexes with this Pt/S ratio
could result from deprotonation of the ligand in ortho
position or in the methyl substituent, but hypotheses
of this type are not sufficiently supported at this stage.
The whole of the obtained results indicates the reac-
tion series shown in Scheme 2. [PtCl2(PhCN)2] under-
goes a clean PhCN/RSR0 substitution to form stable
dichloro thioether complexes. Their reactivity towards
silver acetate markedly depends on the nature of the thi-
oether ligand.
RR'S
AcO
OAc
+ 2H2O
- 2EtOH
Pt
[Pt(O2CCH2SMe)2]x
SRR'
Scheme 2.
somewhat surprising, leading to a ligand fragmentation.
This behaviour clearly contrasts with that observed in
the corresponding dichloro palladium complexes. In
that case, reaction with silver acetate afforded in a single
step the stable mixed sphere trimers [Pd3(l-OAc)3(l-
RSCHZ-C,S)3] (Z = ester or keto group) [5], resulting
from the deprotonation of the methylene group by a
coordinated acetato ligand.
Also, the reaction of the metal acetates of platinum and
palladium with oxo thioethers shows a different behav-
iour. In fact, [Pd3(OAc)6] affords the trimers [Pd3(l-
OAc)3(l-RSCHZ-C,S)3] [1,2], whereas [Pt4(OAc)8] gives
only untractable mixtures with undefined composition.
In this context, it should be underlined that the rhodium
acetate dimer [Rh2(OAc)4] reacts with oxo thioether to
There is no evidence of a simple bis-acetato com-
plexes with the ester ligand MeSCH2C(O)OEt. The final
product is the carboxylato complex [Pt(O2CH2SMe)2]
(12) resulting from the hydrolysis of the ester group
of the two ligands; however, it was possible to isolate
a
small quantity of the acetato complex [Pt
(OAc)(O2CCH2SMe)(MeSCH2C(O)OEt)] (11), which
can easily be seen as resulting from the hydrolysis of
only one ester group. The reaction of the keto thioether
complex [PtCl2(EtSCH2C(O)Me)2] (6) with Ag(OAc) is

666
M. Basato et al. / Inorganica Chimica Acta 358 (2005) 659–666
[2] M. Basato, A. Grassi, G. Valle, Organometallics 14 (1995) 4439.
[3] X. Morise, M.H.L. Green, P. Braunstein, L.H. Rees, I.C. Vei,
New J. Chem. 27 (2003) 32.
give the simple adducts [Rh2(OAc)4(RSCH2Z)2], again
without any evidence of metalation [17].
[4] P.G. Cozzi, P. Veya, C. Floriani, A. Chiesi-Villa, C. Rizzoli,
Organometallics 13 (1994) 1528.
4. Supplementary material
[5] M. Basato, A. Cardinale, M. Zecca, G. Valle, Inorg. Chim. Acta
303 (2000) 100.
[6] J. Dupont, N. Beydoun, M. Pfeffer, J. Chem. Soc., Dalton Trans.
(1989) 1715.
Crystallographic data (excluding structure factors)
for complex 9 have been deposited with the Cambridge
Crystallographic Data Center, CCDC No. 218068. Cop-
ies of this information may be obtained free of charge
from The Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (fax: +44-1223-336-033; deposit@ccdc.-
cam.ac.uk or http://www.ccdc.cam.ac.uk).
[7] J. Dupont, A.S. Gruber, G.S. Fonseca, A.L. Monteiro, G.
Ebeling, R.A. Burrow, Organometallics 20 (2001) 171.
[8] C.K. Bradsher, F.C. Brown, R.J. Grantham, J. Am. Chem. Soc. 5
(1954) 114.
[9] O.A. Serra, L.R.M. Pitombo, Y. Iamamoto, Inorg. Chim. Acta
31 (1978) 49.
[10] A.T.C. North, D.C. Philips, F.S. Mathews, Acta Crystallogr.,
Sect. A 24 (1968) 351.
[11] G.M. Sheldrick, SHELXS-86, Program for Crystal Structure
Solution, University of Go¨ttingen, Germany, 1986.
[12] G.M. Sheldrick, SHELXL-97, Program for the Refinement of
Crystal Structures, University of Go¨ttingen, Germany, 1997.
[13] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[14] ORTEP3 for Windows L.J. Farrugia, J. Appl. Crystallogr. 30
(1997) 565.
Acknowledgements
This work was partially supported by the Ministero
`
dellÕUniversita e della Ricerca Scientifica e Tecnologica
(MURST-Italy). We thank Mr. A. Ravazzolo for skilled
technical assistance.
˚
[15] Z. Bugarcic, K. Lo¨vqvist, A. Oskarsson, Acta Chem. Scand. 47
(1993) 554.
[16] B. Noren, A Oskarsson, C. Svensson, Acta Chem. Scand. 51
(1997) 289.
˚
References
[17] M. Basato, A. Biffis, G. Martinati, M. Zecca, P. Ganis, F.
Benetollo, L.A. Aronica, A.M. Caporusso, Organometallics 23
(2004) 1947.
[1] M. Basato, D. Tommasi, M. Zecca, J. Organomet. Chem. 571
(1999) 115.