Platinum thiosemicarbazide and thiourea complexes: The crystal structure of [PtCl(dppe){SC(NHMe)NHNMe2-S}](PF6) and the influence of intramolecular hydrogen bonding on ligand co-ordination mode

Article abstract of DOI:10.1016/S0277-5387(99)00167-9

The reaction of [PtCl₂(dppe)] [dppe=1,2-bis(diphenylphosphino)ethane] with two equivalents of the thioureas NHRC(S)NHR (R=H, Me, Et) in the presence of NH₄PF₆ led to substitution of both chlorides and formation of the complexes [Pt(dppe){SC(NHR)₂}₂](PF₆)₂ (1a, R=H; 1b, R=Me; 1c, R=Et). In contrast, the reaction of [PtCl₂(dppe)] with one equivalent of the potentially bidentate thiosemicarbazides NHRC(S)NHNR′₂ (R=Me, R′=H; R=Et, R′=H; R=Ph, R′=H; R=Me, R′=Me) in the presence of NH₄PF₆ led to substitution of only one chloride and formation of the complexes [PtCl(dppe){SC(NHR)NHNR₂′-S}](PF₆) (2a, R=Me, R′=H; 2b, R=Et, R′=H; 2c, R=Ph, R′=H; 2d, R=Me, R′=Me). An X-ray analysis of complex 2d revealed that an intramolecular N-HCl hydrogen bond [N(2)Cl(1)=3.29(2) A] helps to stabilise the monodentate co-ordination mode. The chloride ligand can be abstracted from complex 2d by treatment with TlPF₆, and this reaction led to formation of [Pt(dppe){SC(NHMe)NHNMe₂-S,N}](PF₆)₂ 3d. Reaction of [PtCl₂(dppe)] with unsubstituted thiosemicarbazide NH₂C(S)NHNH₂ in the presence of NH₄PF₆ resulted in a mixture of products containing mono- and bidentate co-ordinated ligands, [PtCl(dppe){SC(NH₂)NHNH₂-S}](PF₆) 2e and [Pt(dppe){SC(NH₂)NHNH₂-S,N}](PF₆)₂ 3e. [PtCl₂(dppe)] also reacts with two equivalents of NHMeC(S)NHNMe₂ in the presence of NH₄PF₆ to yield [Pt(dppe){SC(NHMe)NHNMe₂-S}₂](PF₆)₂ 1d, in which the thiosemicarbazide is acting as an S-donor, directly analogous to the thiourea ligands in complexes 1a-c. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00167-9

Polyhedron 18 (1999) 2665–2671
Platinum thiosemicarbazide and thiourea complexes: the crystal structure of
[PtCl(dppe)hSC(NHMe)NHNMe2-Sj](PF6) and the influence of
intramolecular hydrogen bonding on ligand co-ordination mode
*
Andrew D. Burrows , Marc D. Coleman, Mary F. Mahon
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
Received 29 March 1999; accepted 15 June 1999
Abstract
The reaction of [PtCl2(dppe)] [dppe51,2-bis(diphenylphosphino)ethane] with two equivalents of the thioureas NHRC(S)NHR (R5H,
Me, Et) in the presence of NH4PF6 led to substitution of both chlorides and formation of the complexes [Pt(dppe)hSC(NHR)2j2](PF6)2
(1a, R5H; 1b, R5Me; 1c, R5Et). In contrast, the reaction of [PtCl2(dppe)] with one equivalent of the potentially bidentate
9
thiosemicarbazides NHRC(S)NHNR2 (R5Me, R95H; R5Et, R95H; R5Ph, R95H; R5Me, R95Me) in the presence of NH4PF6 led to
9
substitution of only one chloride and formation of the complexes [PtCl(dppe)hSC(NHR)NHNR2-Sj](PF6) (2a, R5Me, R95H; 2b, R5Et,
R95H; 2c, R5Ph, R95H; 2d, R5Me, R95Me). An X-ray analysis of complex 2d revealed that an intramolecular N–H???Cl hydrogen
˚
bond [N(2)???Cl(1)53.29(2) A] helps to stabilise the monodentate co-ordination mode. The chloride ligand can be abstracted from
complex 2d by treatment with TlPF6, and this reaction led to formation of [Pt(dppe)hSC(NHMe)NHNMe2-S,Nj](PF6)2 3d. Reaction of
[PtCl2(dppe)] with unsubstituted thiosemicarbazide NH2C(S)NHNH2 in the presence of NH4PF6 resulted in a mixture of products
containing mono- and bidentate co-ordinated ligands, [PtCl(dppe)hSC(NH2)NHNH2-Sj](PF6) 2e and [Pt(dppe)hSC(NH2)NHNH2-
S,Nj](PF6)2 3e. [PtCl2(dppe)] also reacts with two equivalents of NHMeC(S)NHNMe2 in the presence of NH4PF6 to yield
[Pt(dppe)hSC(NHMe)NHNMe2-Sj2](PF6)2 1d, in which the thiosemicarbazide is acting as an S-donor, directly analogous to the thiourea
ligands in complexes 1a–c.
1999 Elsevier Science Ltd. All rights reserved.
Keywords: Platinum; Thiosemicarbazide; Thiourea; Hydrogen bonding; X-ray crystal structure; Phosphine
1. Introduction
thiosemicarbazides and thioureas in the presence of the
metathesising agent NH4PF6. The thioureas and
thiosemicarbazides used were of the general formulae
Thiourea has a long history as a ligand in co-ordination
chemistry being able to co-ordinate to a metal via either
sulphur or nitrogen. Our original interest in thioureas and
the related thiosemicarbazides arose as these ligands allow
the retention of a hydrogen-bonding surface [1] within a
complex following co-ordination. We have previously
reported the use of the two parallel N–H hydrogen bond
donor groups present in co-ordinated thiosemicarbazides
together with the two parallel hydrogen bond acceptors in
carboxylates as part of our crystal engineering studies of
nickel [2,3] and zinc [4] complexes. Similar hydrogen
bonds have been exploited as the basis of carboxylate
receptors [5,6] and for the effect they have on C–N bond
rotation [7]. In this paper we report the reactions of the
platinum complex [PtCl2(dppe)] with substituted
9
NHRC(S)NHR and NHRC(S)NHNR2, respectively, in
order to retain the required hydrogen bonding surface on
complexation.
2. Results and discussion
Addition of an ethanol solution containing two equiva-
lents of the thiourea NHRC(S)NHR (R5H, Me, Et) to a
dichloromethane solution of [PtCl2(dppe)], followed by an
excess of NH4PF6 in ethanol gave the complexes
[Pt(dppe)hSC(NHR)2j2](PF6)2 (1a, R5H; 1b, R5Me; 1c,
R5Et) in high yield. The symmetrical nature of complexes
1a–c was confirmed by the 31Ph1Hj NMR spectra which
showed one dppe-based phosphorus resonance, with
1J(P,Pt) satellites between 3028 and 3059 Hz, and a septet
arising from the hexafluorophosphate counter ion. The
*Corresponding author. Fax: 144-1225-826-231.
E-mail address: a.d.burrows@bath.ac.uk (A.D. Burrows)
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00167-9
1999 Elsevier Science Ltd. All rights reserved.

2666
A.D. Burrows et al. / Polyhedron 18 (1999) 2665–2671
proposed formulae were confirmed by microanalyses and
FAB mass spectra. In the FAB mass spectra, the two most
intense peaks in each case were assigned to [M1PF6]1
and [M–SC(NHR)2]1, respectively, where
M
is
[Pt(dppe)hSC(NHR)2j2].
The
related
compound
[Pt(PPh3)2hSC(NHEt)2j2](hfac)2 (hfac51,1,1,5,5,5-hexa-
fluoro-2,4-pentanedionate) has been prepared previously
[8] from [Pt(hfac)(PPh3)2](hfac) and 1,3-diethylthiourea,
Fig. 1. Possible structural isomers for complexes 2a–d.
1
and the considerably lower J(P,Pt) coupling constant for
this complex (2436 Hz) may be consistent with the ligands
adopting a trans geometry which is not accessible for
complexes 1a–c because of the chelating phosphine lig-
and. Complexes 1a–c contain four hydrogen bond donor
groups, and hydrogen bonding studies are currently in
progress.
9
PtCl(dppe)hNHRC(S)NHNR2j(PF6). This formulation was
also more consistent with the 31Ph1Hj NMR spectra than
the structure originally proposed: not only does it contain
the two inequivalent phosphine phosphorus atoms neces-
sary to explain the observed coupling pattern, but integra-
tion over the phosphine and PF26 chemical shift ranges
suggest a dppe:PF26 ratio of 1:1 as opposed to 1:2 in the
originally proposed structure.
The reaction of [PtCl2(dppe)] with one equivalent of a
9
thiosemicarbazide NHRC(S)NHNR2 (R5Me, R95H; R5
Et, R95H; R5Ph, R95H; R5Me, R95Me) in the presence
of NH4PF6 was expected to lead to the complex
There are two possible structural isomers for
9
9
[Pt(dppe)hSC(NHR)NHNR2-S,Nj](PF6)2, containing two
PtCl(dppe)hNHRC(S)NHNR2j(PF6) consistent with the
parallel hydrogen bond donor groups. The reactions,
carried out under similar conditions to those that gave rise
to complexes 1a–c, yielded only one product in each case
(complex 2a for R5Me, R95H; 2b for R5Et, R95H; 2c
for R5Ph, R95H; 2d for R5Me, R95Me). Although the
presence of two dppe-based phosphorus signals in the
spectroscopic data. The thiosemicarbazide could be mono-
dentate, with a chloride still bound to the metal (A in Fig.
1), or bidentate with a chloride strongly hydrogen bonded
to the two hydrogen bond donors on the thiosemicarbazide
(B in Fig. 1). There is precedent for the bonding mode in
B in the halide sensors developed by Beer et al. [9].
In order to determine whether A or B was the observed
structure, a single crystal X-ray analysis was undertaken.
Suitable crystals of the NHMeC(S)NHNMe2 adduct 2d
were grown from the diffusion of diethyl ether into an
acetone solution of the complex. The crystal structure (Fig.
2) confirmed structure A. The co-ordination sphere around
1
31Ph1Hj NMR spectrum, both with J(P,Pt) satellites, was
consistent with the formulation above, the microanalysis
results were not accordant with this proposed structure.
Moreover the FAB mass spectra demonstrated that the
metathesis reactions had only replaced one of the two
chlorides,
suggesting
the
empirical
formula
Fig. 2. Solid-state structure of the cationic complex present in 2d. Thermal ellipsoids are illustrated at 30% probability.

A.D. Burrows et al. / Polyhedron 18 (1999) 2665–2671
2667
the platinum atom is distorted square planar consisting of
two phosphorus atoms, a chloride and a sulphur atom from
a monodentate thiosemicarbazide ligand. Selected bond
lengths and angles are given in Table 1. The cis angles
range from 86.9(2) to 93.4(2)8, and the distortion from
planarity is such that the chloride lies slightly above the
molecular ion peak is observed at [M13H]1, where M is
9
[PtCl(dppe)hSC(NHR)NHNR2-Sj], though there is prece-
dence for observing multiple protonation using FAB-MS
[11,12].
Although one chloride is retained in the thiosemicar-
bazide complexes following metathesis with NH4PF6, it is
possible that the co-ordination mode of the thiosemicar-
bazide ligand may be changed from mono- to bidentate by
˚
plane defined by Pt(1), P(1) and P(2) [0.241(7) A]
˚
whereas the sulphur atom lies slightly below [0.266(7) A].
9
the reaction of [PtCl(dppe)hSC(NHR)NHNR2-Sj](PF6)
The C=S, C–N and N–N bond lengths are unexceptional
with respect to comparative parameters for substituted
thiosemicarbazides.
with a halide abstracting agent. In order to test this
premise, a dichloromethane solution of 2d was stirred with
TlPF6 at room temperature for 18 h. After this time, the
31Ph1Hj NMR spectrum of the reaction mixture showed the
disappearance of the peaks for 2d and the presence of
signals for a new complex, 3d. Two sets of doublets with
1J(P,Pt) satellites showed that, like 2d, complex 3d con-
tains inequivalent phosphorus environments, and both the
integration of dppe:PF26 signals and the microanalysis
were consistent with the abstraction of chloride, co-ordina-
tion of the NMe2 nitrogen atom and formation of
[Pt(dppe)hSC(NHMe)NHNMe2-S,Nj](PF6)2.
Although a tertiary amine group (NHNMe2) would be
expected to be a poorer ligand than a primary amine group
(NHNH2) the gain in entropy on chelate formation might
still be expected to favour the bidentate co-ordination
mode. Indeed bidentate nickel(II) complexes of
NHMeC(S)NHNMe2 have been crystallographically char-
acterised and have not been observed to be labile even in
competitive solvents [3]. However, in the platinum com-
plex, monodentate co-ordination of the thiosemicarbazide
is stabilised by formation of a weak intramolecular N–H???
˚
In contrast to the reaction of the substituted thiosemicar-
bazides with [PtCl2(dppe)] which gave only one product,
the reaction with unsubstituted thiosemicarbazide,
NH2C(S)NHNH2, gave rise to two complexes, as observed
in the 31Ph1Hj NMR spectrum. Each complex has two
Cl hydrogen bond [N(2)???Cl(1) 3.29(2) A, H(2A)???Cl(1)
˚
2.40(7) A, N(2)–H(2A)???Cl(1) 151(11)8], giving rise to
an S(6) ring. There is precedence for N–H???Cl hydrogen
bond formation in platinum complexes: the complex cis-
bis(N-benzoyl-N9-propylthiourea)dichloroplatinum(II) con-
1
˚
signals in the dppe region with J(P,Pt) satellites confirm-
tains N???Cl distances of 3.2 A [10], although in this case
ing the presence of inequivalent phosphorus atoms. One of
these complexes had chemical shifts and J(P,Pt) coupling
the hydrogen atoms were not located crystallographically.
Like the thiosemicarbazide ligands, the N-benzoyl-N9-pro-
pylthiourea ligand is also potentially bidentate, and the
lack of chelate formation through acyl oxygen co-ordina-
tion was attributed to intramolecular N–H???O hydrogen
bond formation which removes the oxygen atom from the
vicinity of the metal.
Since the thiosemicarbazide complexes 2a–d have many
features in common such as similar 31P chemical shifts and
coupling constants, and similar fragments observed in their
FAB mass spectra, all can be assigned the formulae
1
constants very close to those observed for 2a–d and, as
2
with these complexes, the J(P,P) coupling is too small to
be resolved: this complex was therefore tentatively iden-
tified as [PtCl(dppe)hSC(NH2)NHNH2-Sj](PF6) (2e). The
1
second species had chemical shifts and both J(P,Pt) and
2J(P,P) coupling constants very close to those observed for
3d
and
was
tentatively
identified
as
[Pt(dppe)hSC(NH2)NHNH2-S,Nj](PF6)2 (3e). Hence, in
contrast to the reactions with substituted thiosemicar-
bazides, thiosemicarbazide itself gives a mixture of the
mono- and bidentate thiosemicarbazide complexes.
9
[PtCl(dppe)hSC(NHR)NHNR2-Sj](PF6) (2a R5Me, R95
H; 2b R5Et, R95H; 2c R5Ph, R95H; 2d R5Me,
R95Me). In the FAB mass spectra of complexes 2a–c, the
In the structure of complex 2d, the 1,1,4-tri-
methylthiosemicarbazide ligand can be likened to a thio-
urea ligand since co-ordination occurs only via the sulphur
atom. This suggests that thiosemicarbazides might be able
to act in a similar manner to the thioureas in complexes
1a–c and that bis(thiosemicarbazide) complexes could be
formed. Since the hydrogen bonding observed in the
structure of 2d involves an N–H group bonded to the
carbon, this interaction is also possible in complexes of the
general formula [PtCl(dppe)hSC(NHR)2j]1 which are pre-
Table 1
˚
Selected bond lengths (A) and angles (8) for complex 2d
Pt(1)–P(2)
Pt(1)–P(1)
Pt(1)–Cl(1)
Pt(1)–S(1)
S(1)–C(27)
N(1)–C(27)
N(1)–C(30)
N(2)–C(27)
N(2)–N(3)
N(3)–C(28)
N(3)–C(29)
P(2)–Pt(1)–P(1)
P(2)–Pt(1)–Cl(1)
2.217(4)
2.249(4)
2.361(4)
2.383(4)
1.73(2)
1.31(2)
1.46(3)
1.31(2)
1.42(2)
1.43(3)
1.46(3)
86.9(2)
173.0(2)
P(1)–Pt(1)–Cl(1)
P(2)–Pt(1)–S(1)
P(1)–Pt(1)–S(1)
Cl(1)–Pt(1)–S(1)
C(27)–S(1)–Pt(1)
C(27)–N(1)–C(30)
C(27)–N(2)–N(3)
N(2)–N(3)–C(28)
N(2)–N(3)–C(29)
C(28)–N(3)–C(29)
N(1)–C(27)–N(2)
N(1)–C(27)–S(1)
N(2)–C(27)–S(1)
89.2(2)
91.1(2)
173.3(2)
93.4(2)
106.2(6)
123(2)
121(2)
112(2)
108(2)
113(2)
sumably
intermediates
in
the
formation
of
[Pt(dppe)hSC(NHR)2j2]21 from [PtCl2(dppe)]. In order to
test whether bis(thiosemicarbazide) complexes could be
formed, a dichloromethane solution of [PtCl2(dppe)] was
reacted with two equivalents of NHMeC(S)NHNMe2
followed by an excess of NH4PF6 to give the complex
118(2)
121.1(14)
120.4(13)

2668
A.D. Burrows et al. / Polyhedron 18 (1999) 2665–2671
the phosphorus atoms trans to sulphur atoms of thioureas
and thiosemicarbazides have smaller coupling constants
than those trans to thiosemicarbazide nitrogen atoms,
whereas the largest coupling constants are for those
phosphorus atoms trans to chloride.
The results reported in this paper demonstrate that
thiosemicarbazides are very versatile ligands in platinum
co-ordination chemistry as they are able to bind to the
metal in a number of different modes. They can be
monodentate, bound solely through the sulphur atom as in
1d, they can be bidentate, bound through sulphur and
nitrogen as in 3d–e, or they can be monodentate but
chelating through an intramolecular N–H???Cl hydrogen
bond as in 2a–e. The formation of this intramolecular
hydrogen bond has a considerable effect on the hydrogen
bonding surface presented by the cation.
3. Experimental
Scheme 1.
Interconversion
of
platinum
complexes
of
NHMeC(S)NHNMe2.
3.1. General
[Pt(dppe)hSC(NHMe)NHNMe2-Sj2](PF6)2 (1d) in high
yield. The symmetrical nature of complex 1d was con-
firmed by the 31Ph1Hj NMR spectrum which showed one
Reactions were routinely carried out using Schlenk-line
techniques under pure dry dinitrogen using dioxygen-free
solvents, but no special precautions were taken to exclude
oxygen during workup procedures. Microanalyses (C, H
and N) were carried out by Mr. Alan Carver (University of
Bath Microanalytical Service). Infrared spectra were re-
corded on a Nicolet 510P spectrometer as KBr pellets or
1
dppe-based phosphorus resonance, with a J(P,Pt) coupling
constant of 3097 Hz, and a septet from the hexafluoro-
phosphate counter ion. The proposed formula was con-
firmed by a FAB mass spectrum in which the two most
intense peaks, as with complexes 1a–c, could be assigned
to [M1PF6]1 and [M–SC(NHMe)NHNMe2]1 where M is
[Pt(dppe)hSC(NHMe)NHNMe2j2]. The reactions of
[PtCl2(dppe)] with 1,1,4-trimethylthiosemicarbazide are
summarised in Scheme 1, and the 31Ph1Hj-NMR data for
the compounds 1a–d, 2a–e and 3d–e are given in Table 2.
1
nujol mulls. H and 31Ph1Hj NMR spectra were recorded
on a JEOL JNM-EX270 spectrometer operating at 270
MHz referenced to TMS and 109.4 MHz referenced to
H3PO4, respectively. 31Ph1Hj NMR data are given in Table
2. FAB mass spectra were recorded on a VG AutoSpec-Q
spectrometer using 3-nitrobenzyl alcohol as the matrix.
[PtCl2(cod)] (cod5cycloocta-1,5-diene) was prepared by
the standard literature method [13]. Thioureas and
thiosemicarbazides were purchased from Aldrich Chemical
and used without purification, with the exception of 1,1,4-
1
The magnitude of the J(P,Pt) coupling constants clearly
reflects the nature of the donor atom trans to the phosphor-
us atom, with those atoms having the largest trans
influence showing the smallest coupling constants. Hence,
Table 2
31Ph1Hj-NMR data for complexes 1a–d, 2a–e and 3d–e
Complexes [Pt(dppe)X2]
[PtCl2(dppe)]c
[Pt(dppe)hSC(NH2)2j2](PF6)2
[Pt(dppe)hSC(NHMe)2j2](PF6)2
[Pt(dppe)hSC(NHEt)2j2](PF6)2
d(P)a
1J(P,Pt)b
3622
3030
3028
3059
3097
41.9
49.6
49.3
50.4
49.0
d,f
1a
1b
1c
1d
d,f
d,f
c,f
[Pt(dppe)hSC(NHMe)NHNMe2-Sj2](PF6)2
Complexes [Pt(dppe)XY]
d(Pa)a
49.9
48.2
48.1
47.9
48.5
49.4
47.0
d(Pb)a
47.6
46.2
45.6
45.5
45.2
37.6
39.9
1J(Pa,Pt)b
3149
3126
3129
3149
3119
3075
2911
1J(Pb,Pt)b
3528
3551
3548
3541
3558
3122
3266
2J(Pa,Pb)b
e
[PtCl(dppe)hSC(NHMe)NHNH2-Sj](PF6)d,f
[PtCl(dppe)hSC(NHEt)NHNH2-Sj](PF6)c,f
[PtCl(dppe)hSC(NHPh)NHNH2-Sj](PF6)c,f
[PtCl(dppe)hSC(NHMe)NHNMe2-Sj](PF6)c,f
[PtCl(dppe)hSC(NH2)NHNH2-Sj](PF6)c,f
2a
2b
2c
2d
2e
3d
3e
e
e
e
e
c,f
[Pt(dppe)hSC(NHMe)NHNMe2-S,Nj](PF6)2
[Pt(dppe)hSC(NH2)NHNH2-S,Nj](PF6)2
7
8
c,f
a a, ppm; b, Hz; c, CDCl3; d, d6-acetone; e, not resolved; f, PF26 also observed [d(P)–143.0, septet, 1J(P,F) 712 Hz].

A.D. Burrows et al. / Polyhedron 18 (1999) 2665–2671
2669
trimethylthiosemicarbazide which was prepared by the
[PtCl2(cod)] (0.100 g, 0.269 mmol) in dichloromethane
(20 cm3) to generate [PtCl2(dppe)] in situ. After stirring
for 10 min, a solution of 4-methylthiosemicarbazide (0.029
g, 0.276 mmol) in dichloromethane (10 cm3) was added,
and the reaction mixture was stirred for 24 h. After this
time, a solution of NH4PF6 (0.175 g, 1.074 mmol) in
acetone (10 cm3) was added. After an additional 30 min
stirring, the solvent was removed under reduced pressure.
The product was extracted with dichloromethane before
recrystallisation from acetone–diethyl ether to give a pale
orange solid. (Found: N, 4.34; C, 40.9; H, 3.95.
C28H31ClF6N3P3SPt?2CH3COCH3 requires N, 4.22; C,
literature method [14]. hdH(CDCl3) 7.32 [s, 1H, NH, (br)],
3
7.05 [s, 1H, NH, (br)] 3.12 [d, J(HH) 6 Hz, 3H, CH3],
2.53 [s, 6H, CH3]j. With the exception of the reaction
between [PtCl2(dppe)], thiosemicarbazide and NH4PF6
(see below) the products were the only compounds ob-
served in the NMR spectra, and were recovered after
recrystallisation in 65–80% yield.
3.2. Syntheses of complexes
3.2.1. Synthesis of [Pt(dppe)hSC(NH2 )2-Sj2 ](PF6 )2 , 1a
Dppe (0.107 g, 0.269 mmol) was added to a solution of
[PtCl2(cod)] (0.100 g, 0.269 mmol) in dichloromethane
(20 cm3) to generate [PtCl2(dppe)] in situ. After stirring
for 10 min, a solution of thiourea (0.041 g, 0.539 mmol) in
ethanol (10 cm3) was added, and the reaction mixture was
stirred for 1 h. After this time, a solution of NH4PF6
(0.175 g, 1.074 mmol) in acetone (10 cm3) was added.
After an additional 30 min stirring, the solvent was
removed under reduced pressure. The product was ex-
tracted with dichloromethane, and recrystallised from
acetone–diethyl ether to give a colourless solid. (Found:
N, 5.41; C, 32.4; H, 3.40. C28H32F12N4P4S2Pt requires N,
5.41; C, 32.5; H, 3.11%); nmax /cm–1(NH) 3457m, 3364m,
41.0; H, 4.35%); nmax /cm–1(NH) 3360m (br), nmax
cm–1(amide) 1586m, nmax /cm21(PF6) 839vs, nmax
/
/
cm–1(CS) 691s; dH(CDCl3) 10.5 [s, NH (br)], 8.0–7.4 [m,
20H, Ar], 2.79 [d, 3J(HH) 5, 3H, CH3], 2.6 [m, 4H, CH2];
m/z 737 [M 1 3H]1, 629 [M–hSC(NHMe)NHNH2j]1.
3.2.5. Synthesis of [PtCl(dppe)hSC(NHEt)NHNH2-
Sj](PF6 ), 2b
Synthesis as for complex 2a using 4-ethylthiosemicar-
bazide (0.032 g, 0.269 mmol) instead of 4-
methylthiosemicarbazide. The crude product was extracted
with dichloromethane before recrystallisation from ace-
tone–diethyl ether to give a colourless solid. (Found: N,
4.26; C, 41.4; H, 4.07. C29H33ClF6N3P3SPt–
1.5CH3COCH3 requires N, 4.16; C, 41.7; H, 4.49%);
nmax /cm–1(NH) 3365m (br), nmax /cm–1(amide) 1576m,
nmax /cm21(PF6) 835vs, nmax /cm–1(CS) 691s; dH(CDCl3)
10.4 [s, NH (br)], 8.0–7.4 [m, 20H, Ar], 3.21 [m, 3J(HH)
7, 2H, CH2Me], 2.6 [m, 4H, CH2], 1.06 [t, 3J(HH) 7, 3H,
dmax /cm–1(NH2) 1634m, nmax /cm–1(PF6) 835vs, nmax
/
cm–1(CS) 691m; dH(d6-acetone) 8.0–7.4 [m, 20H, Ar], 2.7
[m, 4H, CH2]; m/z 890 [M 1 PF6]1, 668 [M–
hSC(NH2)2j]1.
3.2.2. Synthesis of [Pt(dppe)hSC(NHMe)2-Sj2 ](PF6 )2 , 1b
Synthesis as for complex 1a using 1,3-dimethylthiourea
(0.056 g, 0.538 mmol) instead of thiourea. (Found: N,
5.00; C, 37.3; H, 4.03. C32H40F12N4P4S2Pt–
1.5CH3COCH3 requires N, 4.75; C, 37.2; H, 4.19%);
nmax /cm–1(NH) 3386m (br), nmax /cm–1(amide) 1613m,
1510s, nmax /cm–1(PF6) 839vs, nmax /cm–1(CS) 693m;
dH(d6-acetone) 7.9–7.4 [m, 20H, Ar], 2.6 [m, 4H, CH2];
2.80 [s, 12H, CH3]; m/z 946 [M 1 PF6]1, 696 [M–
hSC(NHMe)2j]1.
CH3];
m/z
751
[M 1 3H]1,
629
[M–
hSC(NHEt)NHNH2j]1.
3.2.6. Synthesis of [PtCl(dppe)hSC(NHPh)NHNH2-
Sj](PF6 ), 2c
Synthesis as for complex 2a using 4-phenylthiosemicar-
bazide (0.045 g, 0.269 mmol) instead of 4-
methylthiosemicarbazide. The crude product was extracted
with dichloromethane before recrystallisation from ace-
tone–diethyl ether to give a cream coloured solid. (Found:
N, 4.03; C, 44.6; H, 4.07. C33H33ClF6N3P3SPt–
3.2.3. Synthesis of [Pt(dppe)hSC(NHEt)2-Sj2 ](PF6 )2 , 1c
Synthesis as for complex 1a using 1,3-diethylthiourea
(0.071 g, 0.538 mmol) instead of thiourea. (Found: N,
4.87; C, 37.4; H, 4.28. C36H48F12N4P4S2Pt requires N,
4.88; C, 37.7; H, 4.21%); nmax /cm–1(NH) 3446w, 3368m,
nmax /cm–1(amide) 1607m, 1509s nmax /cm–1(PF6) 839vs,
nmax /cm–1(CS) 694m; dH(d6-acetone) 8.0–7.4 [m, 20H,
Ar], 3.45 [m, 8H, CH2Me], 2.8 [m, 4H, CH2P]; 1.13 [t,
12H, CH3]; m/z 1003 [M 1 PF6]1, 724 [M–
hSC(NHEt)2j]1.
2CH3COCH3 requires N, 3.97; C, 44.3; H, 4.29%); nmax
/
cm–1(NH) 3260m, 3150w (br), nmax /cm–1(amide) 1557s,
1499m, nmax /cm21(PF6) 839vs, nmax /cm–1(CS) 691m; m/
z
799 [M 1 3H]1, 759 [M–Cl]1, 629 [M–
hSC(NHPh)NHNH2j]1.
3.2.7. Synthesis of [PtCl(dppe)hSC(NHMe)NHNMe2-
Sj](PF6 ), 2d
Dppe (0.107 g, 0.269 mmol) was added to a solution of
[PtCl2(cod)] (0.100 g, 0.269 mmol) in dichloromethane
(20 cm3) to generate [PtCl2(dppe)] in situ. After stirring
for 10 min, a solution of 1,1,4-trimethylthiosemicarbazide
(0.036 g, 0.271 mmol) in dichloromethane (10 cm3) was
3.2.4. Synthesis of [PtCl(dppe)hSC(NHMe)NHNH2-
Sj](PF6 ), 2a
Dppe (0.107 g, 0.269 mmol) was added to a solution of

2670
A.D. Burrows et al. / Polyhedron 18 (1999) 2665–2671
added, and the reaction mixture was stirred for 24 h. After
this time, a solution of NH4PF6 (0.175 g, 1.074 mmol) in
acetone (10 cm3) was added. After an additional 30 min
stirring, the solvent was removed under reduced pressure.
The product was extracted with acetone, and recrystallised
by addition of diethyl ether to give colourless crystals.
(Found: N, 4.89; C, 39.3; H, 3.99. C30H35ClF6N3P3SPt
requires N, 4.63; C, 39.7; H, 3.86%); nmax /cm–1(NH)
(0.025 g, 0.270 mmol) instead of 4-methylthiosemicar-
bazide. The 31Ph1Hj NMR spectrum showed the presence
of two complexes 2e and 3e, in a 70:30 ratio, identified as
[PtCl(dppe)hSC(NH2)NHNH2-Sj](PF6)
[Pt(dppe)hSC(NH2)NHNH2-S,Nj](PF6)2, respectively.
and
3.3. Crystallography
3314m, 3142w, nmax /cm–1(amide) 1590m, 1402m, nmax
/
cm21(PF6) 837vs, nmax /cm–1(CS) 693m; dH(d6-acetone)
8.6 [1 H, s, NH, (br)], 8.3 [1 H, s, NH, (br)], 7.6–7.3 [20
H, m, Ph], 2.55 [3 H, d, Me, 3J(HH) 5], 2.4 [4 H, m, CH2]
and 2.18 [6 H, s, Me]; m/z 761 [M]1, 725 [M–Cl]1, 629
Single crystals of complex 2d suitable for analysis by
X-ray crystallography were grown by diffusion of diethyl
ether into an acetone solution of 2d.
[M–hSC(NHMe)NHNMe2j]1,
hSC(NHMe)NHNMe2j]1.
592
[M–Cl–
3.3.1. Crystal data
[C30H35ClN3P2PtS]PF6, M5907.12, triclinic, space
]
group P 1 (No. 2), a59.668(1), b511.211(2), c5
3.2.8. Synthesis of [Pt(dppe)hSC(NHMe)NHNMe2-
Sj2 ](PF6 )2 , 1d
˚
17.346(3) A, a5107.56(1), b596.43(2), g592.656(2)8,
3
–1
˚
U51774.8(5) A , Z52, m54.279 mm , a colourless
Dppe (0.107 g, 0.269 mmol) was added to a solution of
[PtCl2(cod)] (0.100 g, 0.269 mmol) in dichloromethane
(20 cm3) to generate [PtCl2(dppe)] in situ. After stirring
for 10 min, a solution of 1,1,4-trimethylthiosemicarbazide
(0.072 g, 0.541 mmol) in ethanol (10 cm3) was added, and
the reaction mixture was stirred for 1 h. After this time, a
solution of NH4PF6 (0.175 g, 1.074 mmol) in ethanol (10
cm3) was added. After an additional 30 min stirring, the
solvent was removed under reduced pressure. The product
was extracted with dichloromethane, and recrystallised by
addition of diethyl ether to give a colourless solid. (Found:
N, 7.87; C, 34.9; H, 4.09. C34H46F12N6P4S2Pt requires N,
crystal of dimensions 0.330.330.07 mm was used.
3.3.2. Data collection and processing.
Data were collected at 293(2)K on an Enraf-Nonius
CAD4 automatic four-circle diffractometer using graphite
˚
monochromated MoKa radiation (l50.71069 A). 4321
reflections were collected (2.12,u ,21.938, 210#h#10,
211#k#11, 0#l#18) and corrected for Lorentz, polari-
sation and absorption [15]. R(int)50.0313 (pre-DIFABS).
7.31; C, 35.5; H, 4.03%); nmax /cm–1(NH) 3303m, nmax
cm–1(amide) 1617m, 1595s, nmax /cm–1(PF6) 837vs, nmax
/
/
3.3.3. Structure solution and refinement
The solution (SHELX86 [16]) and refinement
(SHELXL93 [17]; full-matrix least squares based on F2)
of the structure converged to a conventional [i.e. based on
3096 with F0 .4s(F0)] R150.0446 and wR250.11751 for
the observed data and 418 parameters. In the final least
squares cycle, all atoms were allowed to vibrate aniso-
tropically. Hydrogen atoms were included at calculated
positions where relevant, except for H(1A) and H(2A)
[attached to N(1) and N(2), respectively] which were
located by examining an electron density map based on
low Bragg angle data, and refined at a fixed distance of
cm–1(CS) 693m; dH(d6-acetone) 7.8–7.3 [20 H, m, Ph],
2.82 [6 H, s, Me], 2.8 [4 H, m, CH2] and 2.51 [3 H, m,
Me];
m/z
1004
[M 1 PF6]1,
725
[M–
hSC(NHMe)NHNMe2j]1.
3.2.9. Reaction of [PtCl(dppe)hSC(NHMe)NHNMe2-
Sj](PF6 ), 2d, with TlPF6: synthesis of
[Pt(dppe)hSC(NHMe)NHNMe2-S,Nj](PF6 )2 , 3d
Complex 2d (0.100 g, 0.11 mmol) was dissolved in
dichloromethane (20 cm3), TlPF6 (0.055 g, 0.16 mmol)
added and the mixture stirred for 18 h. The solution was
filtered, the solvent removed under reduced pressure, and
the crude solid recrystallised from dichloromethane–di-
ethyl ether. (Found: N, 4.03; C, 34.8; H, 3.49.
C30H35F12N3P4PtS?0.5CH2Cl2 requires N, 3.97; C, 34.6;
˚
0.98 A from the relevant parent atoms. The structural
diagram was produced using ORTEX [18].
H, 3.43%); nmax /cm–1(NH) 3398m, 3314m, nmax
cm–1(amide) 1614s, 1524s, nmax /cm–1(PF6) 841vs, nmax
/
/
Supplementary data
cm–1(CS) 700m; dH(d6-acetone) 7.8–7.3 [20 H, m, Ph],
2.96 [12 H, s, Me], 2.7 [4 H, m, CH2] and 2.55 [6 H, s,
Me]; m/z 725 [M]1.
The crystal structure has been deposited at the CCDC.
Supplementary data are available from the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK on request, quoting
the deposition number CCDC 116444.
3.2.10. Reaction of [PtCl2(dppe)] with thiosemicarbazide
and NH4PF6
Synthesis as for complex 2a using thiosemicarbazide
1R15S iFou–uFci/S uFou, wR25[Sw(F2o –Fc2)2 /S w(Fo2)2]1 / 2
.

A.D. Burrows et al. / Polyhedron 18 (1999) 2665–2671
2671
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Acknowledgements
The University of Bath is thanked for financial support.
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