Synthesis and characterization of the iodo-bridged Pt(II) complexes {Pt(R2SO)I}2(μ-I)2 and of trans-Pt(R2SO)(pyrimidine)I2

Article abstract of DOI:10.1016/S0020-1693(02)01394-4

The reactions of K₂[PtI₄] with sulfoxides produce the iodo-bridged dinuclear species (R₂SO)IPt(μ-I)₂Pt(R₂SO)I, which have shown two resonances in ¹⁹⁵Pt NMR spectroscopy at average values of -4933 and -4827 ppm. The signals have been assigned to the presence of cis and trans dimeric isomers in solution. The compounds with di-n-propylsulfoxide and dibenzylsulfoxide were studied by X-ray diffraction methods and the results have shown that the two sulfoxide ligands are in trans positions. The reactions of these dimers with pyrimidine (pm) gave the compounds trans-Pt(R₂SO)(pm)I₂. The ¹⁹⁵Pt chemical shifts of these complexes vary between -4387 and -4438 ppm. The ¹⁹⁵Pt coupling constants with the atoms of pyrimidine ³J(¹⁹⁵Pt-¹H₂), ³J(¹⁹⁵Pt-¹H₆) and ³J(¹⁹⁵Pt-¹³C₅) are (ave.) 22, 32 and 28 Hz, respectively, suggesting a trans configuration. A few ¹⁹⁵Pt coupling constants with the sulfoxide atoms were observed. The ²J vary between 56 and 71 Hz, while the ³J are between 15 and 27 Hz. The crystal structures of the compounds with dimethylsulfoxide, di-n-propylsulfoxide and tetramethylenesulfoxide were determined, confirming the trans geometry.

Full text of DOI:10.1016/S0020-1693(02)01394-4

Inorganica Chimica Acta 346 (2003) 197Á206
/
www.elsevier.com/locate/ica
Synthesis and characterization of the iodo-bridged Pt(II) complexes
{Pt(R2SO)I}2(m-I)2 and of trans-Pt(R2SO)(pyrimidine)I2
Fernande D. Rochon *, Gassan Masserweh, Nicolas Ne´de´lec
De´partement de Chimie, Universite´ du Que´bec a` Montre´al, C.P. 8888, Succ. Centre-ville, Montre´al, Que´bec, Canada H3C 3P8
Received 20 August 2002; accepted 8 October 2002
Abstract
The reactions of K2[PtI4] with sulfoxides produce the iodo-bridged dinuclear species (R2SO)IPt(m-I)2Pt(R2SO)I, which have
shown two resonances in 195Pt NMR spectroscopy at average values of ꢀ
/
4933 and ꢀ4827 ppm. The signals have been assigned to
/
the presence of cis and trans dimeric isomers in solution. The compounds with di-n-propylsulfoxide and dibenzylsulfoxide were
studied by X-ray diffraction methods and the results have shown that the two sulfoxide ligands are in trans positions. The reactions
of these dimers with pyrimidine (pm) gave the compounds trans-Pt(R2SO)(pm)I2. The 195Pt chemical shifts of these complexes vary
3
3
between ꢀ
/
4387 and ꢀ
/
4438 ppm. The 195Pt coupling constants with the atoms of pyrimidine J(195Ptꢀ
/
1H2), J(195Ptꢀ
/
1H6) and
3J(195Ptꢀ
/
13C5) are (ave.) 22, 32 and 28 Hz, respectively, suggesting a trans configuration. A few 195Pt coupling constants with the
sulfoxide atoms were observed. The 2J vary between 56 and 71 Hz, while the 3J are between 15 and 27 Hz. The crystal structures of
the compounds with dimethylsulfoxide, di-n-propylsulfoxide and tetramethylenesulfoxide were determined, confirming the trans
geometry.
# 2002 Published by Elsevier Science B.V.
Keywords: Platinum compounds; Sulfoxide; Pyrimidine; Crystal structures; NMR
1. Introduction
acterization of the compounds cis- and trans-
Pt(R2SO)(pm)Cl2 [4]. The reaction of K[Pt(R2SO)Cl3]
with pm in a 1:1 ratio produces trans-Pt(R2SO)(pm)Cl2,
which isomerize to the cis complex, except for bulky
ligands like diphenylsulfoxide. The isomerization is
quite slow in water especially with more bulky ligands,
but much faster in an organic solvent. When the Pt:pm
ratio was 2:1, trans-pyrimidine-bridged dimers,
Pt(R2SO)Cl2(m-pm)Pt(R2SO)Cl2 were isolated [5]. With
a few sulfoxides, the latter isomerized to the cis dimers.
These compounds were characterized by multinuclear
magnetic resonance spectroscopy and several by crystal-
lographic methods. The geometry of the isomer can be
Although many studies have been reported on Pt(II)
compounds with pyrimidine derivatives, there are only a
few papers with non-substituted pyrimidine (pm). Ro-
chon and coworkers [1] reported the synthesis of cis-
and trans-Pt(pm)2X2 (XꢁCl and Br) and determined
/
the crystal structures of the two trans isomers. Faza-
kerley and Koch [2] synthesized and characterized cis-
[Pt(NH3)2(pm)2](ClO4)2 by 13C NMR spectroscopy,
while Kaufmann et al. characterized trans-
Pt(PEt3)(pm)Cl2 by H and 31P NMR, although they
1
were not able to isolate the compound [3]. The latter
authors have also prepared the pyrimidine-bridged
dimer {PtCl2(PR3)}2(m-pm).
We have recently started a study on mixed-ligands
chloro Pt(II) complexes containing sulfoxides and
pyrimidine. We have reported the synthesis and char-
determined by the coupling constants J(195Ptꢀ
J(195Ptꢀ13C). The cis compounds have larger coupling
constants than the trans complexes.
/
1H) and
/
Sulfoxide molecules have interesting behaviors as
ligands, since they can accept p electron density from
the metallic center. Most of the published studies on PtÁ
/
sulfoxide complexes were done with the most common
ligand, DMSO. The aqueous reaction of K2[PtCl4] with
an excess of sulfoxide produces trans-Pt(R2SO)2Cl2,
* Corresponding author. Tel.: ꢂ
987 4054.
E-mail address: rochon.fernande@uqam.ca (F.D. Rochon).
/
1-514-987 3000/4896; fax: ꢂ1-514-
/
0020-1693/03/$ - see front matter # 2002 Published by Elsevier Science B.V.
doi:10.1016/S0020-1693(02)01394-4

198
F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á206
/
which rapidly isomerizes to the cis isomer, unless the
ligand is very sterically demanding. The greater stability
of the cis-disubstituted complexes has been explained by
The crystals selected for crystallographic studies were
examined under a polarizing microscope for homogene-
ity. The X-ray diffraction measurements were done on a
the enhanced (dÁ
the cis configuration than in the trans geometry [6]. In
the PtÁamine system, where p bonding is absent, the
/
d)p-bonding, which is more effective in
Siemens P4 diffractometer using graphite-monochroma-
˚
0.71073 A) radiation, except for I,
tized Mo Ka (lꢁ
/
˚
1.54178 A)
/
which was measured with Cu Ka (lꢁ
/
trans isomers are more stable than the cis compounds.
Pyrimidine also contains empty p antibonding orbitals,
which could accept electron density from Pt. Our recent
work [4,5] seem to indicate that p-bonding also exists in
radiation. The cell dimensions were determined at
room temperature, from a least-squares refinement of
the angles 2u, v and x obtained for well-centered
reflections. The data collections were made by the 2u/v
scan technique using the XSCANS [8] program. The
coordinates of the Pt atoms were determined by direct
methods or from Patterson map calculations. All the
other non-hydrogen atoms were found by the usual
Fourier methods. The refinement of the structures was
done on F2 by full-matrix least-squares analysis. The
hydrogen atom positions were fixed in their calculated
PtÁ/pyrimidine compounds, but to a much smaller extent
that in PtÁ
/
sulfoxide complexes.
It appeared interesting to compare the results ob-
served in the dichloro system with similar compounds
containing iodo ligands. The aqueous reaction of
K2[PtI4]
with
sulfoxides
does
not
produce
K[Pt(R2SO)I3] or Pt(R2SO)2I2 as observed in the chloro
system. The product is a brown insoluble compound,
which forms quite rapidly. An earlier low field 1H NMR
study by our group [7] has suggested that the iodo-
bridged dimer {Pt(R2SO)I}2(m-I)2 is formed. We have
restudied these reactions with several sulfoxide ligands
in order to confirm the structures of the dimers. We
have now characterized mainly by multinuclear NMR
spectroscopy several of these compounds. We were
successful in obtaining crystals with a few ligands, and
these were studied by crystallographic methods.
position with Ueqꢁ1.2 Ueq (or 1.5 for methyl groups) of
/
the carbon to which they are bonded. Corrections were
made for absorption (Gaussian integration except for V
(empirical C scan)), Lorentz and polarization effects. In
crystal I, the terminal C atoms on both propyl chains
were found to be disordered on two positions. In crystal
III, the atoms Pt, I1, I2, S, O and N1 are all located on a
mirror. Therefore, N3 is disordered on both sides of the
mirror plane. The residual peaks were located in the
close environment of the platinum atoms. The calcula-
tions were done using the Siemens SHELXTL system [8].
The pertinent data are summarized in Table 1.
The reactions of these iodo-bridged dinuclear species
with pyrimidine were then studied and the results were
compared with those obtained in the chloro system.
2.1. I(R2SO)Pt(m-I)2Pt(R2SO)I
2. Experimental
These compounds were synthesized according to the
published method [7] with slight modifications. One
mmole of K2[PtCl4] dissolved in water was added to a
K2[PtCl4] was obtained from Johnson Matthey Inc.
and it was purified by recrystallization in water before
use. The sulfoxide ligands, CD2Cl2 and pyrimidine were
purchased from Aldrich except di-n-propylsulfoxide,
which was bought from Phillips Petroleum. CDCl3 was
obtained from CDN Isotopes.
solution containing Â8 mmol of KI dissolved in a
/
minimum quantity of water. The mixture was stirred for
20 min and the solution was filtered directly on the
sulfoxide (Â2.5 mmol) dissolved in water. The mixture
/
was stirred for about 1 h, and then filtered. The
precipitate was washed with water, dried, and washed
with ether.
The melting and decomposition points were measured
on a FisherÁ/Johns instrument and were not corrected.
The IR spectra were recorded in the solid state (KBr
pellets) on a PerkinÁ
/
Elmer 783 spectrometer between
2.1.1. I(DMSO)Pt(m-I)2Pt(DMSO)I
4000 and 280 cmꢀ1. All the NMR spectra were
measured in CDCl3 or CD2Cl2 on a Varian Gemini
300BB spectrometer operating at 300.075, 75.462 and
Yield, 28%; m. p. 109Á202 8C dec. Anal. C, 4.32%
/
(Calc. 4.56); H, 0.75% (Calc. 1.15%); S, 5.62% (Calc.
6.08). IR (cmꢀ1): 2992m, 2903w, 1412m, 1311m,
64.400 or 64.335 MHz for H, 13C and 195Pt, respec-
1291sh, 1263w, n(Sꢀ
685m, (nPtꢀS) 431s, 369m. H NMR (ppm in CDCl3):
Ha 3.619s 3J(195Ptꢀ1H)ꢁ26 Hz, 3.614s. 13C NMR
(ppm): Ca 48.29, 47.79.
/
O) 1126s, 1020s, 970m, 728w,
1
1
tively. The residual chloroform or dichloromethane
peaks were used as an internal standard for the 1H
(7.24 or 5.32 ppm) and 13C (77.00 or 53.80 ppm) NMR
spectra. For 195Pt, the external references were
/
/
/
K[Pt(DMSO)Cl3] (in D2O, adjusted at ꢀ
from Na2[PtCl6]), cis-Pt(TMSO)2Cl2 (in CDCl3 adjusted
at ꢀ3450 ppm from Na2[PtCl6]) or K2[Pt(CN)4] (in D2O
adjusted at ꢀ4705 ppm from Na2[PtCl6]).
/
2998 ppm
2.1.2. I(TMSO)Pt(m-I)2Pt(TMSO)I
Yield, 30%; m. p. 146Á174 8C dec. Anal. C, 8.06%
(Calc. 8.69); H, 0.95% (Calc. 1.46%); S, 5.44% (Calc.
/
/
/
5.80). IR (cmꢀ1): 2970w, 2935w, 1439w, 1402m. 1305w,

F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á
/206
199
Table 1
Experimental details and crystal data of the compounds I(R2SO)Pt(m-I)2PtI(R2SO) (Rꢁn-Pr (I) and Bz (II)) and compounds trans-Pt(R2SO)(pm)I2
/
(Rꢁ
/
Me (III), n-Pr (IV) and R2ꢁ
/
C4H8 (V)
I
II
III
IV
C10H18I2N2OSPt
663.21
V
Formula
Formula weight
Space group
C
12H28I4O2S2Pt2
C28H28I4O2S2Pt2
1358.40
I4/m
C6H10I2N2OSPt
607.11
Pnma
C8H12I2N2OSPt
633.15
P21/n
1166.24
P21/n
¯
P/
1
˚
a (A)
9.043(2)
15.405(6)
10.169(2)
14.155(2)
14.155(2)
17.454(4)
13.1910(10)
8.6630(10)
11.1530(10)
5.7244(7)
9.9312(12)
14.7647(17)
90.51(1)
95.21(1)
100.46(1)
821.75(17)
2
12.027(2)
8.915(2)
13.995(4)
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
Volume (A )
104.60(2)
110.55(2)
3
˚
1370.9(7)
2
1032
3497.2(9)
4
2448
1274.5(2)
4
1072
1405.2(5)
4
1128
Z
F(000)
rcalc (Mg mꢀ3
m (Mo Ka) (mmꢀ1
Reflections collected
Independent reflections (Rint
600
2.680
)
2.825
55.621(Cu Ka)
2008
2.580
11.665
8826
3.164
15.987
2145
2.993
14.507
3381
)
12.410
5219
)
1652 (0.1502)
855
2080 (0.0583)
1674
1971 (0.045)
1461
4775 (0.0215)
3889
0.0364
3233 (0.0533)
2653
Observed reflections (I ꢀ
R1 (I ꢀ2s(I))
wR2 (all data)
S
/
2s(I))
/
0.0696
0.1524
1.071
0.0350
0.0748
1.061
0.0437
0.1237
1.051
0.0473
0.0987
1.038
0.0953
1.018
R1ꢁ
/
a(jFoꢀ
/
Fcj)/ajFoj; wR2ꢁ
/
[a(w(Fo2ꢀ
/
Fc2)2)/a(wFo2)2]1/2
.
1260w, n(Sꢀ
875w, 776w, 650w, 557m, 364w. 1H NMR (ppm in
CDCl3): Ha 4.289ddd, Jꢁ14.1, 7.4, 6.8; 4.267ddd, Jꢁ
/
O) 1131s, 1070m, 1020w, 995w, 951w,
2.1.5. I(DBzSO)Pt(m-I)2Pt(DBzSO)I
Yield 70%. IR (cmꢀ1): 3062w, 3032m, 2964w, 2915w,
1493s, 1452s, 1409m, 1170m, n(SꢀO) 1112s 1073m,
1031s, 916m, 886w, 773s, 695s, 477s, 410w. H NMR
(ppm in CD2Cl2): CH2 4.68dd Jꢁ12.9, 3.0 Hz, 5.12dd
Jꢁ
12.6, 4.8 Hz, Ph 7.5m. 13C NMR (ppm): CH2 62.23,
/
/
/
1
13.3, 6.9, 6.2; 3.589ddd, Jꢁ
/
12.4, 6.9, 5.9; 3.568ddd, Jꢁ
/
12.5, 7.0, 6.6; Hb 2.377m, 2.183m. 13C NMR (ppm): Ca
61.75, 61.54, Cb 26.22, 26.08.
/
/
62.61, Cphenyl 129.21, 129.26, 129.85, 129.90, 132.12,
132.19.
2.1.3. I(DPrSO)Pt(m-I)2Pt(DPrSO)I
2.1.6. I(MeBzSO)Pt(m-I)2Pt(MeBzSO)I
Yield 70%. IR (cmꢀ1): 3003m, 2912m, 1492m, 1451s,
Yield, 58%; m. p.146Á
2925sh, 2866sh, 1458m, 1403m, 1382sh, 1344w, 1297w,
1250m, 1217w, n(SꢀO) 1135s, 1129s, 1122s, 1066m,
860w, 750m, 651w, 497w, 444m. 1H NMR (ppm in
CDCl3): Ha 3.860ddd Jꢁ12.7, 11.0, 5.5 Hz, 3.842ddd
Jꢁ12.8, 11.2, 5.6 Hz, 3.399ddd Jꢁ11.7, 10.5, 5.3 Hz,
3.356ddd Jꢁ11.6, 10.4, 5.2 Hz, Hb 2.279m, 2.030m, Hg
1.193t Jꢁ7.5 Hz, 1.184t Jꢁ
7.5 Hz. 13C NMR (ppm):
/
190 8C dec. IR (cmꢀ1): 2957m,
1398s, 1297m, 1150s, n(Sꢀ
/
O) 1115s 1070w, 1026w, 963s,
1
866w, 763s, 644s, 586w, 481s, 445m, 420m, 390w. H
/
3
NMR (ppm in CD2Cl2): CH3 3.493s J(195Ptꢀ
/
1H)ꢁ
25 Hz, CH2 5.026m, 4.809m,
/
25
/
3
Hz, 3.484s J(195Ptꢀ
/
1H)ꢁ
/
/
/
Ph 7.49m. 13C NMR (ppm): CH3 47.50, 45.11, CH2
67.6, 65.3, Cphenyl 132.0, 129.6, 129.2, 120.08.
/
/
/
Ca 59.75, 59.33, Cb 17.25, 17.22, Cg 12.88.
2.2. trans-Pt(R2SO)(pm)I2
The iodo-bridged dimers I(R2SO)Pt(m-I)2Pt(R2SO)I
were dissolved in a minimum quantity of CH2Cl2. A
slight excess of pyrimidine (dissolved in a minimum
quantity of CH2Cl2) was slowly added to the dimer
solution and the mixture was stirred between 15 and 60
min. The solution was then evaporated to dryness and
the residue washed with ether and dried.
2.1.4. I(DBuSO)Pt(m-I)2Pt(DBuSO)I
Yield, 53%; m. p.132Á
2928s, 2864m, 1464s, 1400s, 1360w, 1344w, 1314w,
1280w, 1237m, 2101w, 1183sh, n(SꢀO) 1126s, 1091sh.
1078m, 969w, 788w, 737w, 660w, 499w, 454m, 405w. 1H
NMR (ppm in CDCl3): Ha 3.894ddd Jꢁ12.1, 12.1, 5.8,
3.876ddd Jꢁ12.1, 12.1, 5.9 Hz, 3.417ddd Jꢁ11.8, 11.6,
4.8 Hz, 3.378ddd Jꢁ12.0, 11.8, 4.8 Hz, Hb 2.234m,
1.959m, Hg 1.604sextuplet Jꢁ7.3 Hz, 1.598sextuplet
Jꢁ7.4 Hz, Hd 1.033t Jꢁ7.4 Hz, 1.021t Jꢁ
7.5 Hz. 13C
/
184 8C dec. IR (cmꢀ1): 2956s,
/
/
/
/
/
/
2.2.1. trans-Pt(DMSO)(pm)I2
Yield 60%. M.p. 143Á
214 8C dec. IR (cmꢀ1): pm
(vibration number [9,10]): 3080w (8), 3048w (2), 1591s,
/
/
/
/
NMR (ppm): Ca 57.97, 57.55, Cb 25.22, Cg 21.75, Cd
13.79.
1555w (9,10), 1467w (22), 1408s (23), 1226w (3), 1172w

200
F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á206
/
(17), 1070w, 1055w (14), 1026m (1), 976w (5), 820w (12),
729w (13), 695w (4), 638w (6), n(SꢀO) 1120s, n(PtꢀS)
437w. 1H NMR (ppm in CD2Cl2): H2 9.441s
3J(195Ptꢀ1H)ꢁ
21 Hz, H4 8.773dd Jꢁ5.0, 2.3, H5
7.470ddd Jꢁ6.0, 4.8, 1.2 Hz, H6 8.982ddd Jꢁ5.7,
2.2.5. trans-Pt(DBzSO)(pm)I2
Yield 65%. IR (cmꢀ1): 3060w, 3032w, 2970w, 2920w,
1588s, 1503m, 1491m, 1451m, 1404s, 1375m, 1330m,
/
/
/
/
/
1170m, n(Sꢀ
(ppm in CDCl3): CH2 4.58d Jꢁ
Hz, 5.20d Jꢁ12.9 Hz, 5.48d Jꢁ
9.677s, H4 8.70m, H5 7.66m, H6 9.19m. 13C NMR
13C)ꢁ
/
O) 1129s, 872m, 695s, 479m. 1H NMR
/
/
/
12.6 Hz, 5.00d Jꢁ
/12.9
2.3, 0.9 Hz, 3J(195Ptꢀ
/
1H)ꢁ
/
30 Hz, Ha 3.860s
/
/12.3 Hz, Ph 7.45m, H2
3J(195Ptꢀ
/
1H)ꢁ
/
23 Hz. 13C NMR (ppm): C2 161.94, C4
159.17, C5 122.61 J(195Ptꢀ
3
/
13C)ꢁ
/
27 Hz, C6 160.54, Ca
(ppm): C2 163.49, C4 157.60, C5 121.80 3J(195Ptꢀ
/
/
51.83 J(195Ptꢀ
/
13C)ꢁ
/69 Hz.
30 Hz, C6 162.00, Cphenyl 128.36, 128.95, 130.11, 131.7.
2
2.2.6. trans-Pt(MeBzSO)(pm)I2
Yield 65%. IR (cmꢀ1): 3052w, 3002w, 2970w, 2922w,
1590s, 1553m, 1495w, 1465w, 1451w, 1405s, 1150m,
2.2.2. trans-Pt(TMSO)(pm)I2
Yield 61%. M. p. 121Á
209 8C dec. IR (cmꢀ1): pm:
3060w (2), 1593s, 1557m (9,10), 1468m (22), 1408s (23),
/
n(Sꢀ
/
O) 1110s, 1067w, 973m, 962m, 871w, 766m, 696s,
S) 446m. 1H NMR (ppm in CD2Cl2):
CH3 3.59s J(195Ptꢀ1H)ꢁ
23 Hz, CH2 5.07dd Jꢁ13.8,
1.2 Hz, (second peak hidden by solvent), Ph 7.49m, H2
1225w (3), 1171w (17), 1073s, 1052sh (14), 1025w (1),
636w, 478m, n(Ptꢀ
/
813w (12), 698m (4), 639m (6), n(Sꢀ
444w. 1H NMR (ppm in CD2Cl2): H2 9.468s
3J(195Ptꢀ1H)ꢁ
22 Hz, H4 8.783dd Jꢁ5.0, 2.3 Hz, H5
7.474ddd Jꢁ5.9, 4.7, 1.3 Hz, H6 9.021ddd Jꢁ6.0, 2.1,
14.1,
/
O) 1142s, n(Ptꢀ
/
S)
3
/
/
/
/
/
/
9.34s J(195Ptꢀ
/
1H)ꢁ
5.1, 2.4 Hz, H6 8.96ddd Jꢁ
1H)ꢁ34 Hz. 13C NMR (ppm): CH3 47.57
13C)ꢁ70.7 Hz, CH2 67.61 2J(195Ptꢀ13C)ꢁ
63.6 Hz, Ph 129.08, 129.18, 129.63, 131.89, C2 161.67
2J(195Ptꢀ13C)ꢁ
15 Hz, C4 158.96, C5 122.45
3J(195Ptꢀ13C)ꢁ33 Hz, C6 160.30 2J(195Ptꢀ13C)ꢁ
15
Hz.
/
22 Hz, H4 8.69dd, Jꢁ/5.1, 2.4 Hz,
3
/
/
1.1 Hz, 3J(195Ptꢀ
/
1H)ꢁ
/
30 Hz, Ha 4.067ddd Jꢁ
/
H5 7.50dd Jꢁ
/
/5.7, 2.1, 0.9
3
Hz, J(195Ptꢀ
/
/
7.1, 7.1, 3.911m, Hb 2.306m, 2.161m. 13C NMR (ppm):
2J(195Ptꢀ
/
/
/
/
C2 161.95, C4 159.14, C5 122.64 J(195Ptꢀ
/
13C)ꢁ
/
30 Hz,
3
C6 160.52, Ca 64.23 2J(195Ptꢀ
3J(195Ptꢀ13C)ꢁ
27 Hz.
/
13C)ꢁ
/
70 Hz, Cb 25.43
/
/
/
/
/
/
/
/
2.2.3. trans-Pt(DPrSO)(pm)I2
Yield 75%. M.p. 112 8C. IR (cmꢀ1): pm: 3084w (8),
3046m (2), 1593s, 1557m (9,10), 1464m (22), 1409m (23),
1223w (3), 1170w (17), 1074m, 1055w (14), 1024w (1),
2.2.7. trans-Pt(MePhSO)(pm)I2
Yield 65%. IR (cmꢀ1): 3082m, 3062m, 3020m, 3000m,
2915w, 1585s, 1548s, 1463m, 1438m, 1398s, 1302w,
814w (12), 738w (13), 699m (4), 637m (6), n(Sꢀ
n(PtꢀN) 512m, n(Ptꢀ
S) 453m. 1H NMR (ppm in
CD2Cl2): H2 9.449s J(195Ptꢀ
Jꢁ5.1, 2.1 Hz, H5 7.459ddd Jꢁ
8.990ddd Jꢁ
4.050ddd Jꢁ
5.1 Hz, Hb 2.261dddq Jꢁ
2.082dddq Jꢁ
7.4Hz. 13C NMR (ppm): C2 161.89, C4 159.04, C5
122.49 3J(195Ptꢀ13C)ꢁ
26 Hz, C6 160.53, Ca 61.71
2J(195Ptꢀ13C)ꢁ
56 Hz, Cb 17.57, Cg 12.90.
/O) 1127s,
1225w, 1170m, n(Sꢀ
/
O) 1135s, 1084m, 1062m, 1053m,
/
/
1022s, 957s, 820s, 757m, 723m, 698s, 640s, 517s, 488m,
412w, 363w. 1H NMR (ppm in CDCl3): CH3 4.11
3
/
1H)ꢁ
6.0, 4.9, 1.3 Hz, H6
1H)ꢁ
32 Hz, Ha
12.8, 11.1, 5.3 Hz, 3.592ddd Jꢁ
/
21 Hz, H4 8.764dd
3J(195Ptꢀ
3J(195Ptꢀ
7.64m, H6 9.04ddd Jꢁ
/
1H)ꢁ
/
24 Hz, Ph 7.45m, H2 9.52s
24 Hz, H4 8.78dd, Jꢁ4.9, 2.1 Hz, H5
/
/
3
1H)ꢁ
/
/
/
5.9, 2.3, 1.1 Hz J(195Ptꢀ
/
/
/
3
6.2, 2.0, 1.0 Hz, J(195Ptꢀ
/
1H)ꢁ
/
/
/12.8, 11.1,
/
33 Hz. 13C NMR (ppm): CH3 55.49, Ph 125.38, 129.31,
129.93, 133.0, C2 161.98, C4 158.78, C5 122.22, C6
160.44.
/15.1, 10.9, 7.4, 5.3 Hz,
/
15.1, 11.0, 7.4, 5.3 Hz, Hg 1.213t Jꢁ
/
/
/
/
/
3. Results and discussion
2.2.4. trans-Pt(DBuSO)(pm)I2
Yield 49%. M.p. 155Á
193 8C dec. IR (cmꢀ1): pm:
3085w (8), 3048w (2), 1594m, 1557w (9,10), 1468m (22),
/
3.1. Complexes I(R2SO)Pt(m-I)2Pt(R2SO)I
1402s (23), 1229w (3), 1169w (17), 1077sh, 1057sh (14)
The aqueous reaction of K2[PtI4] with sulfoxides does
not produce K[Pt(R2SO)I3] or Pt(R2SO)2I2 as in the
analogous chloro system. The reaction was studied with
1024sh (1), 740w (13), 699m (4), 638w (6), n(Sꢀ
n(PtꢀN) 499w, n(Ptꢀ
S) 454m. 1H NMR (ppm in
CD2Cl2): H2 9.440s J(195Ptꢀ
Jꢁ5.1, 2.1 Hz, H5 7.453ddd Jꢁ
8.983ddd Jꢁ
4.064ddd Jꢁ
5.1 Hz, Hb 2.198m, 2.000m, Hg 1.618sextuplet Jꢁ
Hz, Hd 1.027t Jꢁ
7.2 Hz. 13C NMR (ppm): C2 161.88,
C4 159.03, C5 122.48 J(195Ptꢀ
Ca 59.89
2J(195Ptꢀ13C)ꢁ
3J(195Ptꢀ13C)ꢁ
15 Hz, Cg 21.76, Cd 13.85.
/
O) 1130s,
/
/
3
/
1H)ꢁ
5.9, 5.0, 1.1 Hz, H6
5.9, 2.2, 1.0 Hz J(195Ptꢀ1H)ꢁ
30 Hz, Ha
12.7, 11.3, 5.0 Hz, 3.599ddd Jꢁ12.8, 11.1,
7.3
/
20 Hz, H4 8.753dd
R2SOꢁDMSO, tetramethylenesulfoxide (TMSO), di-n-
/
/
/
propylsulfoxide (DPrSO), di-n-butylsulfoxide (DBuSO),
dibenzylsulfoxide (DBzSO) and benzylmethylsulfoxide
(MeBzSO). A few experiments were also done on
methylphenylsulfoxide (MePhSO), although the pro-
ducts were not very stable. The reaction produces a
dark red precipitate which has been characterized by IR
and multinuclear magnetic resonance spectroscopies
and a few by elemental analysis and X-ray diffraction.
3
/
/
/
/
/
/
/
3
/
13C)ꢁ
56 Hz,
/
26 Hz, C6 160.55,
/
/
Cb 25.54
/
/

F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á
/206
201
1
A low field H NMR study of this reaction was done
many years ago by our research group and we had
suggested that the results were consistent with iodo-
bridged dinuclear species [7].
1
In the present study, the 195Pt and H NMR results
have shown that there are two Pt species in solution. The
crystallographic results have shown that one of the
compound is the iodo-bridged dimer I(R2SO)Pt(m-
I)2Pt(R2SO)I, where the two sulfoxide ligands are in
trans position. Only the DPrSO (Fig. 1) and DBzSO
(Fig. 2) compounds gave crystals suitable for crystal-
lographic studies and both crystals were found to have
the trans geometry. The elemental analysis confirmed
the chemical composition. The 195Pt NMR results have
shown the presence of two signals separated by about
106 ppm (Table 2). We suggest at this moment that the
second species is the same dimer but with a cis
configuration of the two sulfoxide ligands.
Fig. 2. Labeled diagram of the dimer (Pt(DBzSO)I)2(m-I)2 (II). The
ellipsoids correspond to 25% probability.
2K2[PtI4]ꢂ2R2SO
0 I(R2SO)Pt(mꢀI)2Pt(R2SO)Iꢂ4KI
The 195Pt NMR spectra have shown the presence of
Table 2
195Pt chemical shifts (ppm) of the complexes (R2SO)IPt(m-
I)2Pt(R2SO)I
two signals at average values of ꢀ
/
4827 and ꢀ4933 ppm,
/
the lower field peak being slightly more intense. There-
fore, we have assigned the higher field signal to the cis
isomer and the lower field one to the trans compound.
Although there are no example in the literature on 195Pt
NMR spectroscopy of such compounds, the chemical
shifts seem to be observed in the expected region. The
R2SO
d (ppm)
Dd (ppm)
4921 106
3J(195Ptꢀ1H) (Hz)
/
DMSO
TMSO
ꢀ
/
4815
4760
4851
4850
4855
4832
ꢀ/
26
ꢀ
/
ꢀ
/
4869 109
4957 106
4957 107
4959 104
4938 106
DPrSO
DBuSO
DBzSO
MeBzSO
ꢀ
/
ꢀ
/
ꢀ
/
ꢀ
/
ꢀ
/
ꢀ
/
chemical shift of K2[PtI4] was reported at ꢀ
[11], while the one of K[Pt(NH3)I3] was found at ꢀ
/
5208 ppm
4255
ꢀ/
ꢀ/
25(Me)
/
ppm [11]. We have not found any report in the literature
on a Pt(II)I3S species. The signals of the TMSO
complexes, which contain a four-membered ring were
observed at slightly lower fields than the others (Table
2).
energy (Â
the ligands are bonded to Pt by the S atom. The n(Ptꢀ
15] were found around 430 cmꢀ1
/
1125 cmꢀ1) than in free sulfoxides, since
S)
/
vibrations [6,12Á
/
.
The 1H and 13C chemical shifts of the sulfoxide
ligands are presented in the Section 2 along with the
coupling constants. Two series of signals were observed
for each product. The more intense series was assigned
to the trans isomers. The multiplicity of the signals and
The IR spectra have shown the expected sulfoxide
vibrations. The n(Sꢀ/O) vibrations absorb at higher
the coupling constants J(1Hꢀ
/
1H) are similar to those
determined in the complexes cis- and trans-
Pt(R2SO)(pm)Cl2 [4] and in the pyrimidine-bridged
1
dimers {Pt(R2SO)Cl2}2(m-pm) [5]. The H spectrum of
the DMSO iodo-bridged dimer showed only one peak
for the methyl groups for each isomer, but for TMSO,
all the geminal methylene protons possess different
chemical environments. Therefore, there are two signals
for each isomer. Each a proton consists of a doublet of
doublets of doublets, with J values of 13.1, 7.1 and 6.4
Hz. For the b protons, the separation between the two
isomers is not well resolved. For the DPrSO and DBuSO
complexes, the geminal methylene protons have also
different chemical environments due to limited rotation
of the two alkyl chains. Each a proton consists again of
Fig. 1. Labeled diagram of the dimer (Pt(DPrSO)I)2(m-I)2 (I). The
ellipsoids correspond to 30% probability. Only the main component is
shown for each terminal C atoms.

202
F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á206
/
I(R2SO)Pt(mꢀI)2Pt(R2SO)Iꢂ2pm
0 2 trans-Pt(R2SO)(pm)I2
a doublet of doublets of doublets, with J values of 12.1,
10.9 and 5.4 Hz. The separation between the signals of
the geminal protons decreases as the distance from the
coordination site increases. The signals of the Hg
protons in the DBuSO complex consists of a sextuplet
for each isomer (the two Hb are felt as equivalent). The
DBzSO and MeBzSO complexes decompose in CDCl3
producing I2. The deuterated solvent was purified by
neutralizing, but the dimers still decompose very
rapidly. They were measured in CD2Cl2 but there was
also some decomposition, although it was slower. For
these two compounds, free sulfoxide could be detected
The products were characterized by IR and multi-
nuclear NMR spectrocopies. The DBzSO complex was
quite unstable in CDCl3 and CD2Cl2. The IR spectrum
of pyrimidine has been reported and our assignments
(Section 2) are based on these studies [9,10]. The
vibrations of coordinated pyrimidine were observed at
higher or energies similar to those of the free ligand. The
n(Sꢀ
free sulfoxides, since the ligands are bonded to Pt by the
S atom. The n(SꢀO) energies are identical to those
/
O) vibrations absorb at higher energy than in the
1
in H and 13C NMR spectroscopy.
/
The sulfoxide proton signals are often multiplets and
consequently, the 195Pt satellites are weak and overlap
with the other signals, except for DMSO and MeBzSO.
observed in the dimeric species described above and in
the cis and trans analogous chloro compounds [4]. One
absorption band observed around 450 cmꢀ1 was
3J(195Ptꢀ
/
1Ha) values of 26 Hz (DMSO) and 25 Hz
assigned to a n(Ptꢀ
literature [6,12Á
15], while a band around 500 cmꢀ1
observed in a few complexes was assigned to the n(Ptꢀ
/S) vibration as suggested in the
(MeBzSO) were measured.
The 13C NMR chemical shifts are in agreement with
/
/
those reported for Pt(II)Á
We have suggested in the past the presence of inverse
polarization of the p-electrons in the SꢁO bond in
/sulfoxide [4,5,16] complexes.
N) vibration, based also on published results [19,20].
The 195Pt NMR spectra of the complexes trans-
Pt(R2SO)(pm)I2 were measured in CDCl3 or CD2Cl2
/
complexes of the types K[Pt(R2SO)Cl3] [16], Pt(R2SO)-
(pm)Cl2 [4] and {Pt(R2SO)Cl2}2(m-pm) [5]. Bonding of
the sulfoxide ligand to the metal atom would reduce the
p-electron density on the O atom and increase it on the S
atom and its neighboring atoms, including the Pt atom.
This explanation has been suggested in the literature to
and showed only one signal betweem ꢀ
/
4387 and ꢀ4438
/
ppm. These values are at much higher fields than the
corresponding chloro analogues trans-Pt(R2SO)(pm)Cl2
(about ꢀ
summarized in Table 3 and they are close to the one
4405 ppm [21]).
/
3060 ppm) [4]. The 195Pt chemical shifts are
reported for cis-Pt(DMSO)(NH3)I2 (ꢀ
/
explain the 13C NMR spectra of PtÁ
/
CO [17] and PtÁ
/
The 195Pt NMR chemical shifts do not seem to vary very
much with the substituents on the sulfoxide ligand.
The pyrimidine signals of the complexes will first be
discussed. The chemical shifts are shown in Section 2.
The coupling constants with 195Pt are listed in Table 3.
Free pyrimidine is a symmetric molecule (C2v symmetry)
carboxylate complexes [18]. The chemical shifts in 13C
NMR spectroscopy are particularly dependent on such
mesomeric
effects.
3
The
coupling
constants
2J(195Ptꢀ13Ca) and J(195Ptꢀ
/
/
13Cb) could not be deter-
mined, probably because of overlap of the signals due to
the presence of two isomers in solution, and in some
cases, the presence of free ligand (when decomposition
occurred in the NMR solvent).
1
which shows three signals in H and 13C NMR. The
most deshielded signal is H2, then H4, while H5 is the
most shielded. The values have already been reported in
CD2Cl2 [4] and other solvents [22,23]. The shielding
order is the same in 13C NMR.
The crystal structures of the two dimers (Rꢁn-Pr and
/
Bz) will be discussed below.
When pyrimidine is bonded to Pt(II), it is no longer
symmetric (Scheme 1) and four different signals will be
observed. The deshielding order is now H2, H6, H4 and
H5. All protons should couple to each other, but the
couplings on H2 are not observed, since H2 couples with
the two neighboring 14N nuclei, which possess a large
3.2. Complexes trans-Pt(R2SO)(pm)I2
The reactions of the iodo-bridged dimeric species with
a slight excess of pyrimidine in dichloromethane pro-
duced monomers identified as trans-Pt(R2SO)(pm)I2.
Table 3
195Pt NMR chemical shifts (ppm) of the complexes trans-Pt(R2SO)(pm)I2, J(195Ptꢀ
/
1H) and J(195Ptꢀ
3J(195Ptꢀ
C5)
/
13C) coupling constants (Hz)
2J(195Ptꢀ 3J(195Ptꢀ
Cb)
R2SO
d(Pt)
3J(195Ptꢀ
/Ha)
3J(195Ptꢀ
/H2)
3J(195Ptꢀ
/
H6)
/
/
Ca)
/
DMSO
TMSO
ꢀ
/
4387
4427
4404
4399
4413
4438
23
21
22
21
20
22
24
30
30
32
30
34
33
27
30
26
26
33
69
70
56
56
ꢀ
/
27
15
DPrSO
DBuSO
MeBzSO
MePhSO
ꢀ
/
ꢀ
/
ꢀ
/
23(Me)
24
71(Me), 64
ꢀ/

F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á
/206
203
between 56 and 70 Hz (Table 3), about 7Á/10 Hz larger
than those of the chloro analogues. A few coupling
3
constants J(195Ptꢀ13Cb) were observed between 15 and
27 Hz, in agreement with the values reported for the
K[Pt(R2SO)Cl3] complexes [16].
/
3.3. Crystal structures
The crystal structures of the DPrSO (I) and DBzSO
(II) iodo-bridged dinuclear species were determined
(Figs. 1 and 2). Selected bond distances and angles for
the two structures are shown in Table 4. The results are
more precise for the DBzSO compound, since crystal I
was measured with Cu Ka radiation and it was lost
before it could be remeasured with Mo Ka radiation.
No other adequate crystal could be prepared. The
Scheme 1.
quadripolar moment, leading to the broadening of the
signal.
The pyrimidine proton signals are shifted towards
lower field upon coordination, but the shifts are slightly
smaller than in the corresponding chloro complexes [4].
The protons H2 and H6 are the most affected by
coordination as expected. The pyrimidine 13C signals
were observed at lower fields than the corresponding
chloro analogues [4], probably due to the greater
polarizability of iodide.
bridging Ptꢀ
/
I bond in trans position to the R2SO ligand
˚
(2.626(3) for I and 2.6216(7) A for II) is slightly longer
than the one in trans position to the terminal iodo
˚
ligand (2.596(3), and 2.6011(7) A). The large trans
influence of sulfoxides is well known. The terminal
˚
S
Ptꢀ
/
I bonds are 2.586(3) and 2.6110(7) A, while the Ptꢀ
/
In H and 13C NMR, satellites arising from coupling
1
˚
bonds are 2.199(9) and 2.224(2) A for I and II,
respectively.
with the 195Pt nucleus are observed for H2, H6 and C5
(3J) of the pyrimidine ligand (Table 3). The
The DPrSO dimer (I) contains an inversion center,
while in the DBzSO crystal (II), the atoms Pt, I1, I2, S
and O (and their symmetric atoms) are all on a mirror
plane. Therefore, except for the C and H atoms, all the
atoms in II are in a plane. The coordination around the
Pt atom is square planar although there are some
3J(195Ptꢀ
3J(195Ptꢀ
couplings 3J(195Ptꢀ
/
1H2) are smaller (20ꢀ
1H6) coupling constants (30ꢀ
13C5) are between 26 and 33 Hz.
/
24 Hz) than the
/
/
34 Hz). The
/
These values are similar to those observed in trans-
Pt(R2SO)(pm)Cl2 [4]. Furthermore, in the MeBzSO
13C6) coupling
complex, 2J(195Ptꢀ
constants of 15 Hz could be well observed.
/
13C2) and 2J(195Ptꢀ
/
deviations in the angles. The I2ꢀ
/
Ptꢀ
/
I2A angles are
reduced to 85.04(8) for I and to 83.65(2)o for II, because
The chemical shifts of the sulfoxide ligands are
presented in Section 2. The multiplicity of the signals
and the coupling constants J(1Hꢀ
/
1H) are identical to
Table 4
˚
Selected bond distances (A) and angles (8) in crystals I to II
those determined in the complexes cis- and trans-
Pt(R2SO)(pm)Cl2 [4]. For TMSO, all the geminal
methylene protons possess different chemical environ-
ments. For the other complexes (except DMSO), the
geminal methylene protons have also different chemical
environments due to limited rotation. The separation
between the signals of the geminal protons decreases as
the distance from the coordination site increases. The a
protons are more deshielded than in the corresponding
chloro compounds. The sulfoxide 13C signals were
observed at much lower fields than the corresponding
chloro analogues [4]. The inversed polarization of the
Crystal
I
II
Bond lengths
Ptꢀ
Ptꢀ
Ptꢀ
Ptꢀ
Sꢀ
/
I1 (terminal)
2.586(3)
2.596(3)
2.626(3)
2.199(9)
1.43(2)
2.6110(7)
2.6011(7)
2.6216(7)
2.224(2)
1.471(7)
/I2 (bridging, trans to I)
/I2A (bridging, trans to R2SO)
/S
/
O
Bond angles
I1ꢀ
I1ꢀ
I2ꢀ
SꢀPtꢀ
SꢀPtꢀ
SꢀPtꢀ
Ptꢀ
Ptꢀ
Ptꢀ
CꢀSꢀ
OꢀSꢀ
SꢀCꢀ
/
Ptꢀ
Ptꢀ
Ptꢀ
/
I2
173.79(10)
88.76(9)
85.04(8)
173.94(2)
90.29(2)
83.65(2)
93.34(6)
92.72(6)
176.37(6)
96.35(2)
115.4(3)
111.9(2)
100.9(4)
107.8(3)
112.6(4)
/
/
I2A
/
/
I2A
/
/
I1
94.1(2)
Sꢁ
/
O bond seems to be much less important in the iodo
compounds, probably since the electronegativity of
/
/I2
92.1(2)
/
/I2A
176.8(2)
/
I2ꢀ
/
PtA
94.96(8)
iodide is much smaller than the one of chloride.
/
Sꢀ
Sꢀ
/
O
117.5(10)
113(2), 118(2)
96(3)
The sulfoxide proton signals are often multiplets and
consequently, the 195Pt satellites overlap with the other
signals, except for DMSO, MeBzSO and MePhSO.
/
/C
/
/
C
/
/C
102(2), 108(2)
111(3), 115(4)
3J(195Ptꢀ
/
1Ha) values of 23Á
/
24 Hz were measured. In
13Ca) are
/
/
C
13C NMR, the coupling constants 2J(195Ptꢀ
/

204
F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á206
/
of the strain inside the four membered ring. The Ptꢀ
/
I2ꢀ
/
PtA angle is 94.96(8) for I and 96.35(2)o for II. In crystal
I, the O atom is not far from the coordination plane
˚
0.120 A), while it is in the crystallographic
(deviationꢁ
/
plane in crystal II. This is common for PtÁsulfoxide
/
structures (especially the more hindered ones), since this
conformation reduces the steric hindrance caused by the
R groups on the sulfoxides.
The crystal structures of three compounds of the type
trans-Pt(R2SO)(pm)I2 were determined. The sulfoxides
are DMSO (III), DPrSO (IV) and TMSO (V). Labeled
diagrams of the structures are shown in Figs. 3Á
/5.
Selected bond distances and angles are listed in Table 5.
˚
I bonds are between 2.5940(11) and 2.6135(7) A.
The Ptꢀ
/
They seem slightly larger for the di-n-propylsulfoxide
complex (IV), where the steric hindrance is the largest.
Fig. 4. Labeled diagram of trans-Pt(DPrSO)(pm)I2 (IV). The ellip-
soids correspond to 30% probability.
The Ptꢀ
/
S bond seems also slightly larger for the DPrSO
˚
compound (2.2312(13) A) than for the others (2.215(3)
˚
and 2.216(3) A). The Ptꢀ
/
N located in trans position to
˚
the sulfoxides are between 2.042(9) and 2.067(5) A.
These distances are similar to those observed in the
˚
corresponding trans TMSO chloro complex (2.063(5) A
[4], and larger than those observed in the corresponding
cis isomers, where the Ptꢀ
/
N bond is in trans position to
˚
a chloro ligand (ave. 2.028 A [4]). It is much larger than
˚
the value reported for trans-Pt(pm)2X2 (ave. 2.011(6) A)
[1], where the PtꢀN bonds are in trans position to
pyrimidine.
The angles around the Pt atoms are close to the values
expected for square-planar coordination, but there are
/
Fig. 5. Labeled diagram of trans-Pt(TMSO)(pm)I2 (V). The ellipsoids
correspond to 30% probability.
slight deformations due to the bulky sulfoxide. The Sꢀ
PtꢀI angles are slightly larger (ave. 93.218), while the
NꢀPtꢀI are the smallest (ave. 86.888). The best planes
were calculated through the Pt coordination plane and
through the pyrimidine ligand. The dihedral angles
between the Pt and the pyrimidine planes are 88.6(6)8
for III, 75.2(2)8 for IV, and 84.6(3)8 for V.
In the DMSO complex (III), the oxygen atom of the
sulfoxide ligand is in the crystallographic mirror co-
ordination plane, while in the DPrSO crystal (IV) it is
˚
located 0.622(5) A out of the coordination plane. In the
TMSO compound, where the steric hindrance is the
/
smallest (angle Cꢀ
/
Sꢀ
/
Cꢁ92.9(6)8), the deviation of the
/
/
O atom from the coordination plane is much greater
/
/
˚
(1.378(10) A).
The S atom in the sulfoxide ligands is in an
approximate tetrahedral environment. The Cꢀ
angles (101.7(8)8 for DMSO, 101.2(3)8 for DPrSO and
92.9(6)8 for TMSO) are smaller than the other angles as
observed in other Ptꢀ
bond distances and angles of the different sulfoxide
ligands are normal. The SꢀO bond lengths are 1.462(11)
(III), 1.470(4) (IV) and 1.471(9) A (V). The Sꢀ
might depend on the lengths of the alkyl chains. The
/
Sꢀ/C
/R2SO structures [4,5,24]. The
/
˚
/C bond
˚
average values are 1.771(11) A for the DMSO com-
˚
pound, 1.795(6) A for the DPrSO complex and 1.790(13)
˚
A for the TMSO compound. The conformation of the
TMSO ligand in crystal V is of the envelope type.
The pyrimidine bonds and angles agree well with the
values reported for the free ligand [25], for the com-
plexes trans-Pt(pm)2X2 [1], for cis- and trans-
Pt(R2SO)(pm)Cl2 [4] and the pyrimidine-bridged dimers
(Pt(R2SO)Cl2)2(m-pm) [5]. In the DMSO complex, the
pyrimidine N3 atom is equally disordered on two
positions. Therefore, the distances are not given in
Table 5. The angle Nꢀ
/
Cꢀ
/
N is larger (ave. 124.3(9)8)
Fig. 3. Labeled diagram of trans-Pt(DMSO)(pm)I2 (III). The ellip-
soids correspond to 30% probability.
than the other internal angles as reported in the above

F.D. Rochon et al. / Inorganica Chimica Acta 346 (2003) 197Á
/206
205
Table 5
Selected bond distances (A) and angles (8) in crystals III to V
crystals have the trans configuration. Multinuclear
magnetic resonance spectroscopy has shown the pre-
sence of two compounds in CDCl3 or CD2Cl2. The most
intense resonance was assigned to the trans isomer, and
the second signal to the cis dimeric compound. In
chloroform and in dichloromethane, the compounds
decompose producing iodine. It is not soluble in most
other solvents. Several attempts to obtain cis crystals
adequate for crystallographic analysis were not success-
ful. Decomposition probably occurs before crystals can
be obtained.
The reactions of these iodo-bridged dimers with
pyrimidine were studied. Complexes of the type trans-
Pt(R2SO)(pm)I2 were isolated and characterized by
infrared and multi-NMR spectroscopies. Contrary to
the chloro system, these compounds do not isomerize to
the cis isomers. We have made several isomerization
attempts in different solvents. In chloroform and in
dichloromethane, the compounds slowly decompose
and they are very sparingly soluble in most other
solvents.
˚
Crystal
III
IV
V
Bond lengths
Ptꢀ
/
I
2.5956(11)
2.6058(10)
2.215(3)
2.042(9)
1.462(11)
1.771(11)
1.348(10)*
*
2.6135(7)
2.6125(7)
2.2312(13)
2.067(5)
2.5940(11)
2.5990(11)
2.216(3)
2.047(9)
1.471(9)
1.790(13)
1.32(2)
Ptꢀ
/
S
Ptꢀ
/
N
Sꢀ
Sꢀ
Nꢀ
Cꢀ
Cꢀ
/
O
1.470(4)
1.795(6)
/C (ave.)
/C (ave.)
1.341(10)
1.333(11)
1.515(10)
/C (pm, ave.)
1.36 (2)
1.51(2)
/C (R2SO, ave.)
Bond angles
IꢀPtꢀ
SꢀPtꢀ
/
/
I
174.02(4)
93.99(11)
91.99(11)
87.2(3)
86.9(3)
178.9(3)
118.1(5)
110.5(4)
120.6(5)
101.7(8)
107.3(5)
118.6(10)
*
172.09(2)
95.00(4)
92.24(4)
86.8(2)
172.22(4)
96.60(8)
89.44(8)
85.7(2)
/
/I
Nꢀ
/
Ptꢀ/I
85.9(2)
88.8(2)
Nꢀ
Ptꢀ
Ptꢀ
Ptꢀ
CꢀSꢀ
CꢀSꢀ
Cꢀ
Nꢀ
CꢀN3ꢀ
NꢀCꢀ
CꢀCꢀC (pm)
/
Ptꢀ
/
S
178.6(2)
117.5(2)
111.3(2)
121.2(5)
101.2(3)
107.1(3)
117.6(5)
121.6(7)
117.7(7)
122.3(7)
118.3(7)
173.7(2)
112.0(4)
116.5(5)
121.8(9)
92.9(6)
/
Sꢀ
Sꢀ
Nꢀ
/
O
/
/
C (ave.)
/
/
C (ave.)
/
/C
The crystal structures of three complexes trans-
Pt(R2SO)(pm)I2 were studied by crystallographic meth-
ods confirming the NMR results. Sulfoxides have clearly
a larger trans influence than iodides, chlorides or
/
/O (ave.)
108.7(7)
116.4(11)
126.9(14)
116.7(12)
120.3(13)
119.2(13)
/
N1ꢀ
/
C
N
C
/
C2ꢀ
/
/
/
*
pyrimidine. Our results on the Ptꢀ
/
N bonds seem to
indicate that the trans influence of chlorides is slightly
/
/C (ave.)
*
/
/
*
larger than that of pyrimidine.
*, Disorder on N3 and C5.
references. The average Cꢀ
/
N1ꢀC angle is 117.5(9)8. The
/
5. Supplementary material
binding of pyrimidine to the Pt atom does not change
the internal angle at the N1 atom, as it does in the
hydrochlorides of pyrimidine and pyrimidin-2-one
[26,27]. The protonation at N1 in both these compounds
increased the ring angle at the N atom by about 68. This
effect is not observed when Pt is the exocyclic bonded
group. Therefore, contrary to protonation, coordination
to the platinum atom does not affect the structure of the
pyrimidine ligand.
The CIF tables of the five crystal structure determina-
tions have been deposited at the Cambridge Data File
Centre. The deposit numbers are: CCDC 190689-
190693. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (fax: ꢂ44-1223-336-
/
033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
No H-bonding is expected in these types of structures.
The molecules are held together in the crystals by van
der Waals forces.
Acknowledgements
The authors are grateful to the Natural Sciences and
Engineering Research Council of Canada for financial
support of the project.
4. Conclusion
The reaction of K2[PtI4] with sulfoxides produced a
iodo-bridged
dinuclear
complex
I(R2SO)Pt(m-
I)2Pt(R2SO)I. This reaction is very different from the
analogous chloro compounds. The crystal structures of
the di-n-propysulfoxide and the dibenzylsulfoxide com-
plexes were determined by X-ray diffraction. Crystal
structures of this type of iodo-bridged Pt complexes
have not been reported yet in the literature. The results
have shown that the two sulfoxide ligands in the two
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