Cyclometallated platinum complexes with thienyl imines. X-ray crystal structure of [PtMe{3-(PhCH2NCH)C4H2S}PPh3]

Article abstract of DOI:10.1016/S0022-328X(00)00017-6

The reaction of [Pt₂Me₄(μ-SMe₂)₂] with ligands 3-(Me₂NCH₂CH₂NCH)C₄H₃S (2a) and 3-(PhCH₂NCH)C₄H₃S (2b) produced cyclometallation at the α-position of the thiophene ring to give the platinum(II) complexes [PtMe{3-(Me₂NCH₂CH₂NCH)C₄H ₂S}] (4a) and [PtMe{3-(PhCH₂NCH)C₄H₂S}SMe₂] (4b), containing [C,N,N′] or [C,N] ligands, respectively. The reaction of these compounds with triphenylphosphine produced [PtMe{3-(Me₂NCH₂CH₂NCH)C₄H ₂S}PPh₃] (5a) and [PtMe{3-(PhCH₂NCH)C₄H₂S}PPh₃] (5b). Compound 5b was structurally characterized. Attempts to achieve the cyclometallation of the ligands 2-(Me₂NCH₂CH₂NCH)C₄H₃S (2c) and 2-(PhCH₂NCH)C₄H₃S (2d) were unsuccessful and only compounds [PtMe₂{2-(Me₂NCH₂CH₂NCH)C ₄H₃S}] (3c) and [PtMe₂{2-(PhCH₂NCH)C₄H₃S}SMe ₂] (3d), in which the imine behaves as a [N,N′] or [N]-donor ligand, respectively, could be obtained. The electrochemical properties of the compounds based on cyclic voltammetry or square-wave voltammetry were studied at various temperatures. Reversible one-electron reductions, assigned to ligand-centered processes, were observed at room temperature for 5b and at lower temperatures for 4a, 4b and 5a. The reversibility varies with the ligand trans to the thienyl moiety. The one-electron oxidations always occurred in an irreversible manner and were assigned to oxidation at the platinum center. Oxidative addition of methyl iodide to 4a yielded [PtMe₂I{3-(Me₂NCH₂CH₂NCH)C ₄H₂S}] (6a), while the reactions of methyl iodide with 4b and 5b each gave mixtures of isomers, arising from oxidative addition with trans stereochemistry followed by isomerization of the resulting platinum(IV) compounds. The reaction of methyl iodide with compound 5a yielded a complex mixture of compounds.

Full text of DOI:10.1016/S0022-328X(00)00017-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 601 (2000) 22–33
Cyclometallated platinum complexes with thienyl imines. X-ray
crystal structure of [PtMe{3-(PhCH2NCH)C4H2S}PPh3]
Craig Anderson a,b, Margarita Crespo b,*, Merce` Font-Bard´ıa c, Axel Klein d,
Xavier Solans c
a Research and De6elopment Di6ision, CRG Lab, PO Box 301, Succ.R, Montreal, Que´bec, Canada H2S 3K9
b Departament de Qu´ımica Inorga`nica, Facultat de Qu´ımica, Uni6ersitat de Barcelona, Diagonal 647, E-08028 Barcelona, Spain
c Departament de Cristal.lografia, Mineralogia i Dipo`sits Minerals, Uni6ersitat de Barcelona, Mart´ı i Franque`s s/n, E-08028 Barcelona, Spain
d Institut fu¨r Anorganische Chemie der Uni6ersita¨t Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
Received 15 November 1999; accepted 7 January 2000
Abstract
The reaction of [Pt2Me4(m-SMe2)2] with ligands 3-(Me2NCH2CH2NCH)C4H3S (2a) and 3-(PhCH2NCH)C4H3S (2b) produced
cyclometallation at the a-position of the thiophene ring to give the platinum(II) complexes [PtMe{3-(Me2NCH2CH2NCH)C4H2S}]
(4a) and [PtMe{3-(PhCH2NCH)C4H2S}SMe2] (4b), containing [C,N,N%] or [C,N] ligands, respectively. The reaction of these
compounds
with
triphenylphosphine
produced
[PtMe{3-(Me2NCH2CH2NCH)C4H2S}PPh3]
(5a)
and
[PtMe{3-
(PhCH2NCH)C4H2S}PPh3] (5b). Compound 5b was structurally characterized. Attempts to achieve the cyclometallation of the
ligands 2-(Me2NCH2CH2NCH)C4H3S (2c) and 2-(PhCH2NCH)C4H3S (2d) were unsuccessful and only compounds [PtMe2{2-
(Me2NCH2CH2NCH)C4H3S}] (3c) and [PtMe2{2-(PhCH2NCH)C4H3S}SMe2] (3d), in which the imine behaves as a [N,N%] or
[N]-donor ligand, respectively, could be obtained. The electrochemical properties of the compounds based on cyclic voltammetry
or square-wave voltammetry were studied at various temperatures. Reversible one-electron reductions, assigned to ligand-centered
processes, were observed at room temperature for 5b and at lower temperatures for 4a, 4b and 5a. The reversibility varies with
the ligand trans to the thienyl moiety. The one-electron oxidations always occurred in an irreversible manner and were assigned
to oxidation at the platinum center. Oxidative addition of methyl iodide to 4a yielded [PtMe2I{3-(Me2NCH2CH2NCH)C4H2S}]
(6a), while the reactions of methyl iodide with 4b and 5b each gave mixtures of isomers, arising from oxidative addition with trans
stereochemistry followed by isomerization of the resulting platinum(IV) compounds. The reaction of methyl iodide with
compound 5a yielded a complex mixture of compounds. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Platinum; Thienylimines; Cyclometallation; Crystal structure; Electrochemistry; Oxidative addition
The binding modes of thiophenes to metal centers
[18–20] and the coordination behavior of thiophene-
1. Introduction
based macrocycles [21,22], ketimines [23] or phosphines
[24–28] have also been analyzed. Ligand 2-(2%-
thienyl)pyridine [29–31] acts as a monodentate N-
donor in gold, palladium or platinum species, as a
Hydrodesulfurization of heterocycles such as thio-
phenes has been the subject of much research [1,2].
Models for this process and studies of the related CꢀH
or CꢀS bond activation by transition-metal complexes
cyclometallated [C,N] ligand in palladium [32] and plat-
have been reported [3–14]. Moreover, thiophene-based
inum compounds [33–35] or as a bidentate [N,S] in
chromophores [15] and bimetallic materials with olig-
othiophene systems [16,17] have been studied in rela-
tion to their nonlinear optical properties.
ruthenium chemistry. Several bonding modes, such as
bidentate [N,N%], terdentate [N,N%,S] or terdentate cy-
clometallated [N,N%,C] have also been reported for
ligand 6-(2%%-thienyl)2,2%-bipyridine in ruthenium and
rhodium complexes [36,37], while the reactions with
* Corresponding author. Tel.: +34-93-4021273; fax: +34-93-
gold compounds give dimers in which this ligand acts
as a bridge [38].
4907725.
E-mail address: mcrespo@kripto.qui.ub.es (M. Crespo)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00017-6

C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
23
Intramolecular CꢀH bond activation of benzene rings
has been achieved at platinum [39,40], therefore we
decided to study the activation of such bonds in thio-
phenes using a similar strategy. This will allow us to
compare the reactivity and aromatic characteristics of
thiophene with those of benzene. The reactions of
[Pt2Me4(m-SMe2)2] with imine ligands derived from 2-
or 3-thiophenecarboxaldehyde and benzylamine or
N,N-dimethylethylenediamine are reported, as well as
the reactivity and properties of the corresponding re-
sulting compounds. Cyclic voltammetry experiments
were carried out on the platinum complexes in order to
gain insight into their electronic properties and to es-
tablish a comparison with analogous phenyl derivatives
[41,42].
as single isomers arising from intramolecular activation
of a CꢀH bond of the thiophene ring, followed by
methane elimination, in a similar process to that re-
ported for other aryl systems [39,40,43].
As observed for the activation of CꢀH bonds in
benzene groups [40], the strong tendency to form metal-
lacycles containing the imine group (endocycles) pre-
cludes the formation of an exocycle, which could in
principle be formed by the activation of a CꢀH bond of
the benzyl group in ligand 2b.
Moreover, ligands 2a and 2b could in principle afford
two different metallacycles arising from activation of
either of the two non-equivalent CꢀH bonds ortho to
the imine (a and b to the sulfur atom). The value of the
coupling constant J(HꢀH) for the remaining two hy-
drogens in the thienyl group is a valuable tool to
elucidate the activated position. Coupling constants in
the range 4.90–5.80 Hz have been reported for adjacent
hydrogens, while smaller values (3.20–3.65 Hz) are
expected for the coupling between two a hydrogens
[13,44]. From the value obtained for the mutual cou-
pling of the thienyl hydrogens in compounds 4a and 4b
(J(HꢀH)=5 Hz), it can be concluded that exclusive
activation of the a CꢀH bond takes place. This fact is
not unexpected, since it is well established that the
predominant reactivity of thiophene occurs at the car-
bon atom adjacent to, and activated by, the sulfur atom
to yield regiospecifically 2-thienyl derivatives [11,45,46].
The cyclometallated compounds 4a and 4b have been
2. Results and discussion
2.1. Ligands deri6ed from 3-thiophenecarboxaldehyde
The ligands 3-(Me2NCH2CH2NCH)C4H3S (2a) and
3-(PhCH2NCH)C4H3S (2b) were prepared from the
condensation reactions of 3-thiophenecarboxaldehyde
and N,N-dimethylethylenediamine or benzylamine car-
ried out in refluxing ethanol. The resulting imines were
1
characterized by H- and 13C-NMR spectra and their
reactions with [Pt2Me4(m-SMe2)2] (1), shown in Scheme
1, were carried out in acetone.
1
characterized by elemental analyses, and H- and 13C-
The reactions produce cyclometallated compounds
[PtMe{3-(Me2NCH2CH2NCH)C4H2S}] (4a) and [PtMe-
{3-(PhCH2NCH)C4H2S}SMe2] (4b) in which the imine
ligand acts as a tridentate [C,N,N%] or as a bidentate
[C,N] ligand, respectively. Both compounds are formed
NMR spectra. All spectral parameters are in good
agreement with the results obtained for analogous aryl
cyclometallated compounds [39,40]. A downfield shift
of the methyl–platinum resonance could be tentatively
Scheme 1. (i), (ii) and (iii) Reactions with [Pt2Me4(SMe2)2] (1) in acetone, (i) 15 min; (ii) 16 h, ꢀCH4; (iii) 1 h, ꢀCH4. (iv) Reaction with PPh3 in
acetone, 2 h.

24
C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
Fig. 1. Molecular structure of compound 5b.
explained by an interaction of the methyl group with
the sulfur atom of the thiophene ring, since an
analogous shift has been reported for methyl groups
displaying a through-space interaction with fluorine or
chlorine substituents on the aryl rings [47].
5a and 5b (J(PꢀPt)=2594 and 2593 Hz) are larger than
those obtained for analogous phenyl compounds such
as [PtMe{(2-ClC6H4CH2NCH)C6H4}PPh3] (J(PꢀPt)=
2175 Hz) [48]. A smaller trans influence of the thienyl
group, which may be related to the inductive effect of
the sulfur atom, is deduced.
When the reaction of [Pt2Me4(m-SMe2)2] with ligand
1
2a was monitored by H-NMR, compound [PtMe2{3-
(Me2NCH2CH2NCH)C4H3S}] (3a) was detected as an
intermediate that yielded 4a in a further step. A similar
experiment for ligand 2b showed the straightforward
formation of 4b. Previous results [39,40] indicate that
coordination of the imine ligand to platinum is a pre-
ceding step to the cyclometallation process, and that
the corresponding coordination compounds are easily
detected for chelate dinitrogen ligands. For imines con-
taining one single nitrogen, such compounds could only
be observed when the metallation step is either hindered
as for the ligand PhCH2NCH(2,4,6-C6H2Me3) [40], or
hampered by bulky groups as for PhCH2NCH(3,5-
C6H2Cl2) [47]. Since an increased reactivity is expected
for thiophene when compared with benzene [45], the
cyclometallation step is probably even faster for the
ligand 2b than for previously studied phenyl deriva-
tives, thus preventing the detection of a coordination
compound. At no stage in the reactions of [Pt2Me4(m-
SMe2)2] with ligands 2a and 2b was coordination of the
thiophene sulfur atom to platinum(II) detected.
2.2. Crystal structure of compound 5b
Suitable crystals were grown from acetone solution.
The crystal structure is composed of discrete molecules
separated by van der Waals interactions. There are two
molecules in the asymmetric unit that are related by a
non-crystallographic pseudo-center of symmetry. In-
spection of these two molecules shows that there are no
major differences between them, and the bond lengths
and bond angles are very similar and are within experi-
mental error (3|). A view of one of these molecules is
shown in Fig. 1. Selected bond lengths and angles are
given in Table 1.
Table 1
,
Selected bond lengths (A) and bond angles (°) for compound 5b, with
estimated S.D.
Bond lengths
PtꢀC(1)
PtꢀN
SꢀC(1)
NꢀC(5)
C(1)ꢀC(2)
C(3)ꢀC(4)
2.021(9)
2.168(7)
1.702(9)
1.311(11)
1.363(14)
1.34(2)
PtꢀC(31)
PtꢀP
SꢀC(4)
NꢀC(6)
C(2)ꢀC(5)
C(2)ꢀC(3)
2.032(10)
2.294(2)
1.737(14)
1.462(10)
1.462(10)
1.431(13)
The reactions of compounds 4a and 4b with PPh3
were also carried out and produced compounds
[PtMe{3-(Me2NCH2CH2NCH)C4H2S}PPh3] (5a) and
[PtMe{3-(PhCH2NCH)C4H2S}PPh3] (5b), which were
1
characterized by elemental analysis, and H- and 31P-
Bond angles
C(1)ꢀPtꢀC(31)
C(31)ꢀPtꢀN
C(31)ꢀPtꢀP
91.3(4)
168.5(4)
92.8(3)
C(1)ꢀPtꢀN
C(1)ꢀPtꢀP
NꢀPtꢀP
78.0(4)
175.3(3)
98.2(0)
NMR. The phosphine replaces either the SMe2 ligand
or the NMe2 moiety of the tridentate ligand, and even
with an excess of PPh3 the metallacycles are not
cleaved. The values obtained for J(PꢀPt) in compounds
C(5)ꢀNꢀC(6)
117.1(8)

C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
25
As expected from spectroscopic characterization, the
methyl group is trans to the nitrogen atom, the CꢁN
group is endo to the cycle and the imine adopts an E
configuration. The platinum atom displays a tetrahe-
dral distorted planar coordination and the following
lysis and 1H-NMR spectra. Spectral data were fully
consistent with coordination through both nitrogen
atoms. Ligand 2d reacted with [Pt2Me4(m-SMe2)2] (1) to
yield unstable compound [PtMe2{2-(PhCH2NCH)-
C4H3S}SMe2] (3d), which could not be isolated in a
pure form and could only be characterized in solution
,
displacements (A) are observed from the least-squares
1
plane of the coordination sphere (molecule A): Pt,
−0.0099; P(1), −0.0469; N(1), 0.0618; C(1), −0.0656;
and C(31), 0.0607. The metallacycle is approximately
planar; the largest deviation from the mean plane deter-
by H-NMR. Spectral parameters are consistent with
coordination through the imine nitrogen atom only. In
contrast to dialkylsulfides SR2, thiophene is a very
weak sulfur-donor ligand, and few S-bound thiophene
complexes are actually known [18]. For instance, it has
been shown that imines [(SC4H3)CRꢁN]2C2H4 coordi-
nate to soft metals such as Ag(I) or Cu(I) through
nitrogen atoms without any evidence of interaction of
the sulfur atom [23]. Further evidence of the low nucle-
ophility of thiophene is the fact that no sulfonium salt
is produced upon reaction of thiophene with methyl
iodide [44].
Attempts to achieve the cyclometallation of ligands
2c and 2d in a range of solvents and conditions were
unsuccessful and led to decomposition with formation
of metallic platinum. Since cycloplatination of ligand
2-(2%-thienyl)pyridine [29] has been described, the failure
to obtain cyclometallated compounds from ligands 2c
and 2d cannot only be explained by the lower reactivity
of the b-positions of thiophene; other factors such as
the design of the ligands and the nucleophilic character
of the platinum substrate [Pt2Me4(m-SMe2)2] (1) should
be taken into account.
,
mined by the five atoms is −0.0103 A for Pt. The
metallacycle is nearly coplanar with the coordination
plane, the dihedral angle being 2.97°. The angles be-
tween adjacent atoms in the coordination sphere of
platinum lie in the range 78.0–98.0°, the smallest angle
corresponding to the metallacycle. Bond lengths in the
coordination sphere of the platinum and in the thio-
phene are in the usual range for analogous compounds
[29,30,43,49]. In particular, the PtꢀP bond length is
within the range obtained for compounds with substi-
tuted phenyl groups in spite of the lower trans influence
of the thienyl group.
2.3. Ligands deri6ed from 2-thiophenecarboxaldehyde
The ligands 2-(Me2NCH2CH2NCH)C4H3S (2c) and
2-(PhCH2NCH)C4H3S (2d) were prepared from the
condensation reactions of 2-thiophenecarboxaldehyde
and N,N-dimethylethylenediamine or benzylamine car-
ried out in refluxing ethanol and they were character-
2.4. Electrochemical measurements
1
ized by H-NMR spectra.
Interest in these ligands arises from the fact that they
might display several modes of coordination to plat-
inum, as reported in the literature for ligands 2-
(2%-thienyl)pyridine and 6-(2%%-thienyl)2,2%-bipyridine.
However, activation of the CꢀH bond in these ligands
would only be possible at the less reactive b position of
the thiophene.
Electrochemical data are summarized in Table 3,
together with those for previously reported compounds
2i and 4i (see Chart 1) [50].
The reaction of [Pt2Me4(m-SMe2)2] (1) with ligand 2c
under the same conditions used for the cyclometallation
of ligand 2a, produced compound [PtMe2{2-(Me2-
NCH2CH2NCH)C4H3S}] (3c) as shown in Scheme 2.
This compound was characterized using elemental ana-
(Chart 1)
In the cyclic voltammogram of the non-cyclometal-
lated complex 3c, measured at ambient temperature in
THF solution, one reduction wave and one oxidation
wave were observed. The reduction potential is lower
compared with that of the free ligand. Although a
reoxidation wave is discernible and allows us to calcu-
late a half-wave potential, the ratio of the peak currents
Ipa/Ipc=0.19 indicates that the reduction wave is not
reversible. The ratio Ipa/Ipc grows with decreasing tem-
perature up to 0.46 at 268 K. The oxidation wave was
observed at a rather low potential and is irreversible,
even at temperatures down to 248 K and at high scan
rates (5000 mV s−1).
Scheme 2. (i) and (ii) Reactions with [Pt2Me4(SMe2)2] (1) in acetone,
(i) 16 h; (ii) 15 min.

26
C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
Both of the cyclometallated complexes 4a and 4b
4b the potential changes by only 240 mV. If we at-
tribute the stabilizing effect to the enlargement of the
heterocyclic ring system to a 10-electron p-system [41],
platinaisoindole in 4i is more favored than thieno[2,3]-
platinapyrrole in 4b. The reason might be related to the
lower aromaticity of the thiophene system.
exhibit one reduction wave and two oxidation waves.
An additional second reduction process was observed
for 4b. The potential of the first reduction is also
lowered compared with the free ligands. The potentials
are in the same range, but under identical conditions 4a
(with the terdentate [C,N,N%] ligand) showed a higher
degree of reversibility than 4b. They are both reversible
at 268 K (Ipa/Ipc=1). Both showed two irreversible
oxidation processes, 4b at a higher potential than 4a.
The triphenylphosphine complexes 5a and 5b exhib-
ited very similar electrochemical behavior compared
with their analogues 4a and 4b. The oxidation and
reduction potentials were in the same range as those for
4a and 4b, but the degree of reversibility of the reduc-
tion reactions was generally higher.
The first reduction process for all the platinum com-
pounds contains one electron, which was checked by
comparative measurement of a weighed sample of fer-
rocene. The currents for the first oxidation wave were
of comparable size.
From comparison with previous studies on such cy-
clometallated complexes [41,42], it is reasonable to as-
sume that the reduction reactions take place in
essentially ligand-centered orbitals. The oxidation reac-
tion on the other hand is metal centered and leads to
very unstable platinum(III) species.
Electrochemical oxidation and reduction of thio-
phenes is generally followed by fast chemical reactions.
Polythiophenes are formed after oxidation and poly-
meric, often paramagnetic, material after reduction [51].
The cyclovoltammetric responses are therefore irre-
versible. Coordination of the ligand to a platinum
fragment as in 3c leads to a lower reduction potential
compared with the free ligand and to some degree a
re-oxidation wave can be observed. Therefore the de-
composition reactions that follow the electron uptake
are still present but slowed down. The effect can be
increased with lower temperature. The cyclometallation
reaction yielding the complexes 4a, 4b, 5a or 5b does
not give rise to further lowering of the reduction poten-
tials, but markedly enhances the stability of the mono-
reduced state. We assume that the cyclometallation
hinders some of the decomposition pathways. An in-
crease in stability, in the series 4bB4aB5aB5b can be
derived from the Ipa/Ipc ratio. Obviously PPh3 has the
strongest stabilizing effect, most probably due to its
p-acceptor properties. Moreover, the NMe2-chelate lig-
and in 4a gives better stabilization than SMe2 in 4b. It
is also worth noting that the lowering of the reduction
potential and the stabilizing effect on the radical an-
ionic species is less pronounced for these thiophene
complexes than for the analogues that contain a phenyl
moiety. The cyclometallated complex 4i showed a re-
versible reduction wave at −2.59 V that is 380 mV
lower than for the free ligand while on going from 2b to
2.5. Oxidati6e addition reactions
It is generally accepted that the oxidative addition of
alkyl halides to platinum(II) compounds gives trans
stereochemistry. Compounds with cis stereochemistry
may be formed in a subsequent isomerization process
[52,53]. In order to assess the influence of different
ligands trans to the thienyl carbon, the study of the
oxidative addition of methyl iodide to cyclometallated
compounds 4a, 4b and 5b was undertaken (Scheme 3).
Valuable information concerning the electronic struc-
ture of these compounds can be obtained from 195Pt-
NMR and UV–vis spectroscopies. In agreement with
the reported trends [54], the chemical shift l(195Pt)
moves to higher fields in the order 4aB4bB5b, indi-
cating an increased shielding of the platinum nucleus as
the covalency increases from N-donor (4a) to S-donor
(4b) to P-donor (5b). The reactivity of square-planar
complexes with respect to oxidative addition has been
found to be related to the energies of the lowest-energy
electronic transitions in the UV–vis spectra [55]. For
the compounds under study, the band at lowest energy,
assigned to a metal-to-ligand charge transfer (MLCT)
transition, increases its energy in the order 4aB4bB5b
as the electron density at the metal center decreases.
Therefore, we can anticipate that the reactivity with
respect to oxidative addition should follow the order
4a\4b\5b. This trend is fully consistent with the
electrochemical studies, which show that the oxidation
potential increase in the order 4aB4bB5b.
The reaction of [PtMe{3-(Me2NCH2CH2NCH)-
C4H2S}] (4a) with methyl iodide in acetone at room
temperature gave the platinum(IV) compound [PtMe2-
I{3-(Me2NCH2CH2NCH)C4H2S}] (6a) arising from
trans-oxidative addition of the alkyl halide. The reac-
tion of 6a with PPh3 produced the displacement of the
NMe2 group for the phosphine ligand according to
Reaction (1) in which 8a is formed. Both J(MeꢀPt) and
J(PꢀPt) values suggest a trans arrangement of the phos-
phine and the methyl group [39], which indicates that
an isomerization process takes place.
(1)

C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
27
of SMe2 for PPh3 yielded only isomer 7b% in which the
triphenylphosphine is trans to a methyl group, as
shown in Reaction (2).
The reaction of [PtMe{3-(PhCH2NCH)C4H2S}SMe2]
(4b) with methyl iodide in acetone at room temperature
gave a mixture of two isomers of the cyclometallated
platinum(IV)
compound
[PtMe2I{3-(PhCH2NCH)
-C4H2S}SMe2] (6b and 6b%) as evidenced from the pres-
ence of two sets of signals in a 2:1 ratio in the 1H-NMR
spectrum. From the 2J(HꢀPt) values for the methyl
groups, a fac-PtC3 structure is assigned to both the
isomers, which differ only in having a methyl group
trans to iodide or trans to SMe2. When the reaction was
1
monitored by H-NMR, the 2:1 ratio of products was
seen immediately and remained constant.
When the reaction of [PtMe{3-(PhCH2NCH)-
C4H2S}PPh3] (5b) with methyl iodide was monitored by
1H- and 31P-NMR spectra, resonances assigned to plat-
inum(IV) compound [PtMe2I{3-(PhCH2NCH)C4H2S}-
PPh3] (7b) appeared in the early stages of the reaction
together with signals due to unreacted platinum(II)
compound 5b. As the reaction proceeded, the intensity
of the latter decreased, while resonances due to a
second platinum(IV) isomer 7b% appeared. Within 24 h,
the spectra showed that the isomerization of 7b to 7b%
was complete. A reduced coupling to platinum is ob-
served for the axial methyl in 7b%, which suggests a trans
arrangement of the axial methyl and the PPh3. The
J(PꢀPt) values are in the range expected for platin-
um(IV) compounds, which is considerably reduced
from that of the platinum(II) compound, but for 7b, the
value is greater than for the phenyl analogue due to the
low trans influence of the thienyl group.
(2)
The results obtained for 4b and 5b indicate that: (1)
the oxidative addition takes place with trans stereo-
chemistry and is followed by isomerization of the re-
sulting platinum(IV) compound; (2) the oxidative
addition is slower for the phosphine derivative 5b than
for the SMe2 derivative 4b, as expected from consider-
ing both steric and electronic factors and (3) while
isomers 6b and 6b% have a similar stability, isomer 7b%
with the PPh3 trans to methyl is more stable than 7b.
The latter result can be related with the greater bulk of
the phosphine ligand.
The reaction of the analogous platinum(II) phenyl
metallated complex [PtMe{(PhCH2NCH)C6H4}PPh3]
(5i) [48] with methyl iodide was monitored by NMR for
Furthermore, when the mixture of isomers 6b/6b% was
treated with PPh3 in acetone, the substitution reaction
Scheme 3. (i) Reactions with MeI in acetone, r.t.

28
C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
Interestingly, the analogous platinum(II) compound
[PtMe{3-(Me2NCH2CH2NCH)C6H4}(PPh3)] (5j) [39]
containing a phenyl instead of a thienyl group gave
initially only one product when reacted with methyl
iodide, a platinum(IV) compound 7j. After several
hours the reaction yielded [PPh3Me]I and a platinu-
m(II) compound 7j% exclusively, as shown in Reaction
(5).
comparison with 5b (Reaction (3)). Compound 5i gave
a single isomer of [PtMe2I{(PhCH2NCH)C6H4}PPh3]
with PPh3 trans to the axial methyl group, based on
NMR data. The higher rate of the isomerization pro-
cess can be attributed to the higher trans influence of
the phenyl when compared with the thienyl group.
(3)
The reaction of methyl iodide with compound
[PtMe{3-(Me2NCH2CH2NCH)C4H2S}(PPh3)] (5a), in
which the NMe2 fragment is not coordinated to the
1
platinum is more complex (Reaction (4)). The H- and
31P-NMR spectra show the presence of several com-
pounds. [PtMeI{3-(Me3NCH2CH2NCH)C4H2S} (7a)
1
was detected in the H-NMR spectrum by the presence
(5)
of a methylplatinum group appearing as a singlet,
indicating dissociation of the PPh3 ligand, and a corre-
sponding resonance integrating nine hydrogens as-
signed to an NMe3 moiety. The 31P-NMR spectrum
showed the presence of a platinum(II) compound con-
taining two non-equivalent PPh3 ligands trans to C-
donors, for which the structure [PtMe{3-(Me2NCH2-
CH2NCH)C4H2S}(PPh3)2] (7a%) was assigned. In the
31P-NMR, a minor resonance at l= −9.93 [J(PꢀPt)=
1031 Hz] corresponding to a platinum(IV) compound
was tentatively assigned to 7a%%, since the J(PPt) value is
in the same range, but not identical to that of com-
pound 8a.
Although the reactions of 5a and 5j with methyl
iodide are not entirely similar, in both cases the addi-
tion of methyl iodide to the dangling NMe2 moiety
competes with addition at the metal center.
In conclusion, while intramolecular CꢀH activation
at the less reactive b position of the thiophene ring
could not be achieved, activation at the a position
allows the preparation of new cyclometallated platinum
compounds containing two or three fused five-mem-
bered rings. The electrochemical properties and the
reactivity of these compounds appear to be modulated
by the ligands in the coordination sphere of the plat-
inum center.
3. Experimental
3.1. Instrumentation
1H-, 13C-, 31P-{1H} and 195Pt-NMR spectra were
recorded by using Varian Gemini 200 (1H, 200 MHz),
Varian 300 (13C, 75 MHz) and Bruker 250 (31P, 101.25
MHz; 195Pt, 54 MHz) spectrometers, and referenced to
SiMe4 (1H, 13C), H2PtCl6 in D2O (195Pt), and H3PO4
(31P). l values are given in ppm and J values in Hz. IR
spectra were recorded as KBr disks on a Nicolet 520
FT-IR spectrometer. Microanalyses and mass spectra
(CI and FAB) were performed by the Serveis Cient´ıfico-
Te`cnics de la Universitat de Barcelona. UV–vis spectra
were recorded in a Shimadzu UV-160A spectro-
photometer.
(4)
After several hours in solution, the only compounds
detected were 7a, characterized as above, and
[PPh3Me]I, for which H- and 31P-NMR data are con-
1
sistent with the values given in the literature [56,57].

C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
29
Cyclic voltammetry and square-wave voltammetry
experiments were carried out using a three-electrode
configuration (glassy carbon working electrode, plat-
inum counter electrode, Ag ꢀ AgCl reference) and a PAR
273 potentiostat and function generator with PAR
M270/250 software. As internal standard the ferro-
cene ꢀ ferrocenium couple (FeCp2+/0) was used. Fer-
rocene was added in equimolar amount so as to estimate
the electrochemical reversibility and the effects of un-
compensated resistance. The temperature was adjusted
using a FRYKA FT08-64 cryostat, temperature toler-
ance was 91°C. The electrochemical experiments were
carried out under an argon atmosphere in dried and
deaerated solvents using tetrabutylammoniumhex-
afluorophosphate (Bu4NPF6) as the supporting
electrolyte.
3.2.2. Synthetic procedure for compounds 3
Compound 3c was obtained by adding a solution of
3.5×10−4 mol of the imine in acetone (10 ml) to a
solution of 100 mg (1.74×10−4 mol) of compound 1 in
acetone (10 ml). The mixture was stirred for 16 h and,
upon cooling, orange crystals were formed. These were
filtered, washed with hexane and dried in vacuum.
3.2.2.1. [PtMe2{2-(Me2NCH2CH2NCH)C4H3S}] (3c).
Yield 100 mg (70%). 1H-NMR (200 MHz, CDCl3):
2
2
l=0.48 [s, J(PtꢀH)=91, Mea]; 0.64 [s, J(PtꢀH)=84
Meb]; 2.64 [m, Hd]; 2.81 [s, J(HꢀPt)=21, Hc]; 4.05 [m,
3
He]; {7.03 [dd, J(HꢀH)=5; 4]; 7.62 [dd, J(HꢀH)=5;2];
8.06 [dt, J(HꢀH)=4;2], aromatics}; 8.96 [s, 3J(PtꢀH)=
47, Hf]. Anal. Found: C, 32.4; H, 5.0; N, 7.0. Calc. for
C11H20N2SPt: C, 32.27; H, 4.92; N, 7.33%.
Compounds 3a and 3d were characterized by the
following procedure: a 20.0 mg (0.035 mmol) amount of
complex 1 and 0.07 mmol of the corresponding imine
were dissolved in 0.6 ml of acetone-d6, and the 1H-NMR
spectrum was recorded within a period of 15 min.
3.2. Preparation of the compounds
The complex [Pt2Me4(m-SMe2)2] was prepared as re-
ported [58].
3.2.1. Synthetic procedure for compounds 2
3.2.2.2. [PtMe2{3-(Me2NCH2CH2NCH)C4H3S}] (3a).
1H-NMR (200 MHz, acetone-d6): l=0.20 [s,
Compounds 2 were prepared by the reaction of 0.5 g
(4.4 mmol) of the corresponding aldehyde (2- or 3-thio-
phenecarboxaldehyde) with an equimolar amount of
N,N-dimethylethylenediamine (0.39 g), or N-benzy-
lamine (0.48 g) in refluxing ethanol. After 4 h, the solvent
was removed in a rotary evaporator to yield yellow or
red oils. Yield 80–85%.
2
2J(PtꢀH)=92, Mea]; 0.41 [s, J(PtꢀH)=85 Meb]; 2.66
3
[m, Hd]; 2.71 [s, J(HꢀPt)=22, Hc]; 4.01 [m, He]; {7.79
[dd, J(HꢀH)=2; 1]; 8.28 [dd, J(HꢀH)=5; 1]; 8.58 [m],
3
aromatics}; 9.02 [s, J(PtꢀH)=49, Hf].
1
3.2.2.3. [PtMe2{2-(PhCH2NCH)C4H3S}SMe2] (3d). H-
3.2.1.1. 3-(Me2NCH2CH2NCH)C4H3S (2a). 1H-NMR
(200 MHz, CDCl3: l=2.30 [s, Ha]; 2.62 [t, 3J(Hb–Hc)=
7, Hb]; 3.69 [td, 3J(Hc–Hb)=7, 4J(Hc–Hd)=1, Hc];
{7.30 [dd, J(HꢀH)=5; 3]; 7.51 [dd, J(HꢀH)=5; 1]; 7.59
[dd, J(HꢀH)=3; 1], aromatics}; 8.32 [s, 1H, Hd]. 13C-
NMR (75 MHz, CDCl3: l=45.90 [s, Ca]; {59.90; 60.13,
Cb, Cc}, {125.66; 126.24; 128.24; 140.39, thiophene};
156.08 [s, Cd].
2
NMR (200 MHz, acetone-d6): l=0.31 [s, J(PtꢀH)=
87, Me]; 0.37 [s, 2J(PtꢀH)=83, Me]; 1.75 [s,
3J(HꢀPt)=24, Hc]; 5.10 [m, Hd]; 9.25 [s, 3J(PtꢀH)=52,
He].
3.2.3. Synthetic procedure for compounds 4
Compound 4a was obtained by the reaction of 100 mg
(1.74×10−4 mol) of compound 1 with 64 mg (3.52×
10−4 mol) of compound 2a in acetone (20 ml). After
continuous stirring during 16 h, the solvent was removed
in a rotary evaporator and the resulting orange solid was
filtered, washed with hexane and dried in vacuum.
3.2.1.2. 3-(PhCH2NCH)C4H3S (2b). 1H-NMR (200
MHz, CDCl3: l=4.78 [s, Ha]; {7.32 [m]; 7.57 [dt,
J(HꢀH)=5;1]; 7.64 [dd, J(HꢀH)=3;1], aromatics};
8.40 [s, Hb]. 13C-NMR (75 MHz, CDCl3: l=65.01 [s,
Ca]; {125.77; 126.33; 126.91; 139.09, thiophene};
{127.92; 128.41; 128.56, aromatics}; 156.20 [s, Cb].
3.2.3.1. [PtMe{3-(Me2NCH2CH2NCH)C4H2S}] (4a).
Yield 90 mg (66%). 1H-NMR (200 MHz, CDCl3):
3.2.1.3. 2-(Me2NCH2CH2NCH)C4H3S (2c). 1H-NMR
(200 MHz, CDCl3: l=2.30 [s, Ha]; 2.63 [t, 3J(Hb-Hc)=
7, Hb]; 3.71 [td, 3J(HcꢀHb)=7, 4J(HcꢀHd)=1, Hc]; {7.06
[dd, J(HꢀH)=5; 4]; 7.29 [dd, J(HꢀH)=4;1]; 7.39 [dt,
J(HꢀH)=5; 1], aromatics}; 8.41 [d, 4J(HdꢀHc)=1, Hd].
l=1.05 [s, J(PtꢀH)=78, Mea]; 2.86 [s, J(PtꢀH)=25,
Meb]; 3.19 [t, J(HꢀH)=6, Hc]; 4.00 [t, J(HꢀH)=6, Hd];
{7.01 [d, 4J(PtꢀH)=34, J(HꢀH)=5]; 7.13 [d,
2
3
J(HꢀH)=5], aromatics}; 8.37 [s, J(PtꢀHe)=57, He].
3
13C-NMR (75 MHz, CDCl3): l= −17.74 [J(PtꢀC)=
736, Mea]; 49.18 [Meb]; {51.81 [J(PtꢀC)=27]; 68.67, Cc,
Cd}; {122.79 [J(PtꢀC)=60]; 125.22 [J(PtꢀC)=57];
149.18 [J(PtꢀC)=51]; 153.96 [J(PtꢀC)=1325], thio-
phene}; 160.17 [J(PtꢀC)=76, Ce]. 195Pt-NMR (54
3.2.1.4. 2-(PhCH2NCH)C4H3S (2d). 1H-NMR (200
MHz, CDCl3: l=4.79 [s, Ha]; {7.06 [dd, J(HꢀH)=4;
3.5]; 7.33 [m]; 7.39 [dt, J(HꢀH)=4;1], aromatics}; 8.44
[s, Hb].

30
C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
MHz, acetone-d6): l= −3668.6[s]. UV–vis (acetone):
u=389 nm (m=1122 M−1 cm−1). Anal. Found: C,
30.3; H, 4.2; N, 6.9. Calc. for C10H16N2SPt: C, 30.69;
H, 4.12; N, 7.16%.
An analogous procedure with a reaction time of 1 h
yielded compounds 4b.
3.2.5.1. [PtMe2I{3-(Me2NCH2CH2NCH)C4H2S}] (6a).
1
Yield 50 mg (73%). H-NMR (200 MHz, acetone-d6):
2
2
l=0.78 [s, J(PtꢀH)=71, Meb]; 1.24 [s, J(PtꢀH)=64,
Mea]; {2.66 [s, J(PtꢀH)=19], 3.22 [s, J(PtꢀH)=19],
3
3
Mec}; 4.20 [m, HdꢀHe]; {7.11[m, J(HꢀH)=5], 7.22 [m,
J(HꢀH)=5], aromatics}; 8.47 [s, J(PtꢀHf)=48, Hf].
3
Anal. Found: C, 25.3; H, 4.0; N, 5.2. Calc. for
C11H19IN2SPt: C, 24.77; H, 3.59; N, 5.25%.
3.2.3.2. [PtMe{3-(PhCH2NCH)C4H2S}SMe2] (4b).
Yield 120 mg (73%). 1H-NMR (200 MHz, CDCl3):
2
3
l=1.10 [s, J(PtꢀH)=78, Mea]; 1.98 [s, J(PtꢀH)=32,
3.2.5.2. [PtMe2I{3-(PhCH2NCH)C4H2S}SMe2] (6b/
Meb]; 5.09 [s, J(HcꢀPt)=14, Hc]; {7.18 [d, J(PtꢀH)=
35, J(HꢀH)=5]; 7.30 [m], aromatics}; 8.41 [s,
3J(PtꢀHd)=52, Hd]. 13C-NMR (75 MHz, CDCl3): l=
ꢀ20.18 [J(PtꢀC)=719, Mea]; 19.86 [Meb]; 62.18 [Cc];
{124.75; 125.19; 137.68; 147.45, thiophene}; {127.53;
128.48; 137.25, aromatics};167.69 [J(PtꢀC)=66, Cd].
195Pt NMR (54 MHz, acetone-d6): l= −4040.0 [s].
UV–vis (acetone): u=378 nm (m=3147 M−1 cm−1).
Anal. Found: C, 38.1; H, 4.1; N, 2.9. Calc. for
C15H19NS2Pt: C, 38.13; H, 4.05; N, 2.96%.
3
4
1
6b%). Yield 50 mg (77%). H-NMR (200 MHz, acetone-
d6): 6b: l=0.66 [s, 2J(PtꢀH)=69, Meb]; 1.41 [s,
3
2J(PtꢀH)=67, Mea]; 8.45 [s, J(PtꢀHe)=45, He]; 6b%:
2
2
l=1.21 [s, J(PtꢀH)=70, Meb]; 1.59 [s, J(PtꢀH)=68,
Mea]; 2.06 [s, 3J(PtꢀH)=14 Mec]; 5.37 [m, Hd];
{7.36[m], 7.57 [m], aromatics}; 8.46 [s, J(PtꢀHe)=45,
3
He]. Anal. Found: C, 31.8; H, 3.6; N, 2.3. Calc. for
C16H22INS2Pt: C, 31.28; H, 3.61; N, 2.28%.
3.2.5.3. [PtMe2I{3-(PhCH2NCH)C4H2S}PPh3] (7b/7b%).
1
Yield 45 mg (74%). H-NMR (200 MHz, acetone-d6):
3.2.4. Synthetic procedure for compounds 5
2
3
7b: l=0.35 [s, J(PtꢀH)=67, J(PꢀH)=7, Meb]; 1.50
Compounds 5 were obtained by the reaction of 50
mg of the corresponding compound 4 with the equimo-
lar amount of PPh3 in acetone. After continuous stir-
ring during 2 h, the solvent was removed in a rotary
evaporator and the resulting yellow solid was filtered,
washed with hexane and diethyl ether and dried in
vacuum.
[s, J(PtꢀH)=68, J(PꢀH)=7, Mea]; {4.84 [d], 4.99 [d],
2
3
J(HꢀH)=15, AB pattern, Hc}, 8.19 [s, J(PtꢀHe)=45,
3
Hd]; 31P-NMR (101.26 MHz, acetone-d6): l= −5.45 [s,
J(PtꢀP)=1564]. 7b%: l=1.15 [s, 2J(PtꢀH)=60,
3J(PꢀH)=8, Meb]; 1.69 [s, J(PtꢀH)=68, J(PꢀH)=7,
2
3
Mea]; {4.46 [d], 5.40 [d], J(HꢀH)=15, AB pattern, Hc};
7.92 [s, J(PtꢀHd)=44, Hd]; 31P-NMR (101.26 MHz,
3
3.2.4.1.
[PtMe{3-(Me2NCH2CH2NCH)C4H2S}PPh3]
acetone-d6): l= −10.53 [s, J(PtꢀP)=1016]. Anal.
Found: C, 46.6; H, 4.2; N, 1.7. Calc. for C32H31INSPPt:
C, 47.18; H, 3.84; N, 1.72%.
1
(5a). Yield 70 mg (84%). H-NMR (200 MHz, CDCl3):
l=0.86 [d, J(PtꢀH)=82, J(PꢀH)=8, Mea]; 1.85 [s,
Meb]; 1.77 [t, J(HꢀH)=7, Hc]; 3.15 [t, J(HꢀH)=7,
Hd]; {7.42 [m]; 7.68 [m], aromatics}; 8.40 [s,
3J(PtꢀHe)=52, He]. 31P-NMR (101.26 MHz, CDCl3):
l=30.78 [J(PtꢀP)=2594]. Anal. Found: C, 51.0; H,
4.8; N, 4.2. Calc. for C28H31N2PSPt: C, 51.45; H, 4.78;
N, 4.29%.
2
3
The reactions of these compounds and of 5a, 5i and
5j with methyl iodide were monitored by NMR in the
following way: 10 ml of methyl iodide were added to 20
mg of the corresponding compound dissolved in 0.6 ml
of acetone-d6 in a 5 mm NMR tube and spectra were
taken.
3.2.4.2.
[PtMe{3-(PhCH2NCH)C4H2S}PPh3]
(5b).
Yield 60 mg (84%). 1H-NMR (200 MHz, CDCl3):
3.2.5.4. [PtMe2I{PhCH2NCHC6H5}PPh3] (7i). 1H-
l=0.89 [d, J(PtꢀH)=81, J(PꢀH)=8, Mea]; 4.13 [s,
2
3
2
NMR (200 MHz, acetone-d6): l=1.12 [s, J(PtꢀH)=
J(PtꢀH)=10, Hc]; {6.80 [m]; 7.19 [m], 7.36 [m], 7.67
62, 3J(PꢀH)=8, Meb]; 1.56 [s, 2J(PtꢀH)=70,
3J(PꢀH)=7, Mea]; {4.61 [d], 5.64 [d], J(HꢀH)=16, AB
pattern, Hc}; {6.58 [J(PtꢀH)=43, J(HꢀH)=8], 6.91
[dd, J(HꢀH)=8; 1.5], 7.02 [t, J(HꢀH)=8], 7.32 [m],
[m], aromatics}; 8.09 [s, J(PtꢀHd)=52, Hd]. 31P-NMR
3
(101.26 MHz, CDCl3): l=30.55 [J(PtꢀP)=2593]. 195Pt
NMR (54 MHz, acetone-d6): l= −4328.1[d,
J(PtꢀP)=2614]. UV–vis (acetone): u=373 nm (m=
2546 M−1 cm−1). Anal. Found: C, 55.7; H, 4.2; N, 2.1.
Calc. for C31H28NPSPt: C, 55.35; H, 4.20; N, 2.08%.
3
7.46 [m], aromatics}; 8.13 [s, J(PtꢀHe)=49, Hd]; 31P-
NMR (101.26 MHz, acetone-d6): l= −8.72 [s,
J(PtꢀP)=1017].
3.2.5. Synthetic procedure for compounds 6, 7 and 8
An excess of methyl iodide (0.1 ml) was added to
solutions of 50 mg of the corresponding compounds 4a,
4b and 5b in acetone. The mixtures were stirred for 3 h,
and the solvent was removed under vacuum to yield
light yellow solids.
3.2.5.5. [PtMeI{3-(Me3NCH2CH2NCH)C4H2S}] (7a).
1H-NMR (200 MHz, acetone-d6): l=1.18 [s,
2J(PtꢀH)=72, Mea]; 3.46 [s, Meb]; {4.3[m]; 4.7[m], Hc,
3
Hd}; {7.10[d], 7.21[d], aromatics}; 8.64 [s, J(PtꢀHe)=
40, He].

C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
31
68, J(PꢀH)=8, Mea]; 2.08 [s, Mec]; {2.15[m], 3.90[m],
Table 2
Crystallographic and refinement data for compound 5b
3
Hd, He}; 8.15 [s, J(PtꢀHf)=45, Hf]; 31P-NMR (101.26
MHz, acetone-d6): l=10.38 [J(PtꢀP)=1011]. Anal.
Found: C, 43.8; H, 4.4; N, 3.4. Calc. for
C29H34IN2PSPt: C, 43.78; H, 4.31; N, 3.52%.
Empirical formula
Formula weight
Crystal system
C31H28NPPtS
672.66
Monoclinic
P21/a
Space group
Unit cell dimensions
3.3. X-ray structure analysis
,
a (A)
12.151(10)
24.417(8)
18.286(4)
90
99.42(3)
90
5352(5)
1.670
8
,
b (A)
,
c (A)
3.3.1. Data collection
h (°)
i (°)
k (°)
A prismatic crystal was selected and mounted on an
Enraf–Nonius CAD4 diffractometer. Unit cell parame-
ters were determined from automatic centering of 25
reflections (12°BqB21°) and refined by the least-
squares method. Intensities were collected with graphite
monochromatized Mo–Ka radiation, using the ꢀ/2q
scan technique. 16 102 reflections were measured in the
range 2.01°BqB29.98°, 15 571 of which were non-
equivalent by symmetry. 8727 were assumed as ob-
served applying the condition I\2|(I). Three
reflections were measured every 2 h as orientation and
intensity controls; significant intensity decay was not
observed. Lorentz polarization and absorption correc-
tions were made. Further details are given in Table 2.
3
,
V (A )
Dcalc (g cm−3
)
Z
F(000)
2640
Crystal size (mm3)
0.1×0.1×0.2
0.71069
293(2)
16 102
15 571[Rint=0.0343]
0.0588
0.1295
640
0.00
,
u(Mo–Ka) (A)
Temperature (K)
Reflections collected
Independent reflections
R [I\2|(I)]
Rw (F2)
Number of refined parameters
Max. shift/estimated S.D.
Largest difference peak and hole (e A
−3
,
)
0.626 and −0.521
3.3.2. Structure solution and refinement
The structure was solved by direct methods, using the
SHELXS-97 computer program [59], and refined by the
full-matrix least-squares method, with the SHELXL-97
computer program [59] using 15 445 reflections (very
negative intensities were not assumed). The function
3.2.5.6. [PtMe{3-(Me2NCH2CH2NCH)C4H2S}(PPh3)2]
1
(7a%). H-NMR (200 MHz, acetone-d6): l=0.38 [dd,
2J(PtꢀH)=65, J(PH)=8.6; 6.6, Mea]; 9.09 [s, He];
31P-NMR (101.26 MHz, acetone-d6): l=24.22 [d,
J(PtꢀP)=1839, J(PP)=14]; 26.16 [d, J(PtꢀP)=2279,
J(PꢀP)=14].
2
2 2
minimized was SwꢀꢀFoꢀ −ꢀFcꢀ ꢀ , where w=[|2(I)+
2
2
(0.0725P)2+12.610P]−1, and P=(ꢀFoꢀ +2ꢀFcꢀ )/3. f,
f % and f %% were taken from the International Tables of
X-Ray Crystallography [60]. 2H were located from a
difference synthesis and refined with an overall
isotropic temperature factor using a riding model. Fur-
ther details are given in Table 2.
3.2.5.7. [PtMe2I{3-(Me3NCH2CH2NCH)C4H2S}PPh3]I
(7a%%). 31P-NMR (101.26 MHz, acetone-d6): l= −9.93
[s, J(PtꢀP)=1031].
3.2.5.8. [PtMe2I{Me3NCH2CH2NCHC6H4}PPh3]I (7j).
31P-NMR (101.26 MHz, acetone-d6): l= −8.57 [s,
J(PtꢀP)=1028].
4. Supplementary material
3.2.5.9. [PtMeI{Me3NCH2CH2NCHC6H4}] (7j%). 1H-
2
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC no. 136782 for compound 5b.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44-1223-336033; e-
mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
NMR (200 MHz, acetone-d6): l=1.12 [s, J(PtꢀH)=
74, Mea]; 3.48 [s, Meb]; {4.4[m]; 4.9[m], Hc, Hd};
{7.01[m], 7.18[m], 7.55[m], aromatics}; 9.00 [s,
3J(PtꢀHe)=42, He].
3.2.5.10. [PtMe2I{3-(Me2NCH2CH2NCH)C4H2S}PPh3]
(8a). This was obtained by the reaction of 50 mg of
compound 6a with the equimolar amount of PPh3 in
acetone. After continuous stirring during 2 h, the sol-
vent was removed in a rotary evaporator and the
resulting yellow solid was filtered, washed with hexane
and diethyl ether and dried in vacuum. Yield 60 mg
(80%). 1H-NMR (200 MHz, acetone-d6): l=1.22 [d,
Acknowledgements
We acknowledge financial support from the DGI-
CYT (Ministerio de Educacio´n y Cultura, Spain, pro-
2
2J(PtꢀH)=61, J(PꢀH)=8, Meb]; 1.67 [d, J(PtꢀH)=

32
C. Anderson et al. / Journal of Organometallic Chemistry 601 (2000) 22–33
Table 3
Electrochemical data of free ligands and platinum complexes a
b
Compound
Epa Ox2
1.02
Epa Ox1
E1/2 Red1 (DEpp
)
I
pa/Ipc
Epc Red2
T (°C)
2a
2b
2c
2i
3c
3c
3c
4a
4a
4b
4b
4i
0.47
1.36
0.47
1.24
0.08
0.09
0.10
0.40
0.51
0.56
0.59
0.52
0.65 c
0.68 c
0.64
0.68
−3.03 irr.
−3.00 irr.
−2.83 irr.
−2.97 irr.
−2.56(92)
−2.48(82)
−2.47(72)
−2.74(92)
−2.74(82)
−2.76(91)
−2.71(82)
−2.59(78)
−2.74(82)
−2.74(68)
−2.67(84)
−2.67(84)
298
298
298
298
298
288
268
298
268
298
268
298
298
288
298
288
1.06
0.19
0.21
0.46
0.84
1.00
0.79
1.00
1
0.92
1.00
0.99
1.00
1.07
1.20
1.42
1.45
−3.08 irr.
−3.55 irr.
−3.52 irr.
−3.56 irr.
−3.35 irr.
−3.29 irr.
−3.29 irr.
5a
5a
5b
5b
1.38
1.42
a Data from cyclic voltammetric or square-wave voltammetric experiments in 0.1 M THF–Bu4NPF6 solutions; anodic peak potentials Epa for
irreversible oxidations, cathodic peak potentials Epc for irreversible reductions, half-wave potentials E1/2 (in V), peak potential differences DEpp
in parentheses (in mV).
b The ratio of cathodic peak current Ipc for reduction waves to anodic peak current Ipa for reoxidation waves is used to assign observed waves
as fully reversible (Ipa/Ipc=1.0) or partly reversible (Ipa/IpcB1).
c Followed by a shoulder at +0.83 V.
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