Platinum(II) complexes of chelating and monodentate thiourea monoanions incorporating chiral, fluorescent or chromophoric groups

Article abstract of DOI:10.1016/S0020-1693(01)00473-X

The reaction of cis-[PtCl₂(PPh₃)₂] with trisubstituted thioureas [R¹R²NC(=S)NHR³] in refluxing methanol with triethylamine base, followed by addition of NaBPh₄ gives the salts [Pt{SC(=NR¹R²)NR³}(PPh₃) ₂]BPh₄ in high yield; a range of thiourea substituents, including chiral, fluorescent and chromophoric groups can be incorporated. The azo dye-derived complex [Pt{SC(=N(CH₂CH₂)₂O)NC₆H ₄N=NC₆H₄NMe₂}(PPh₃) ₂]BPh₄ has been characterised by a single-crystal X-ray diffraction study. The formation of a fluorescein-derivatised platinum-thiourea complex is also described. Reaction of cis-[PtCl₂(PPh₃)₂] with PhNHC(S)NHPh or EtNHC(S)NHEt, triethylamine and NaBPh₄ gives, respectively, [Pt{SC(=NHPh)NPh}(PPh₃)₂]⁺ and the known cation [Pt{SC(=NHEt)NEt}(PPh₃)₂]⁺, isolated as tetraphenylborate salts. Reaction of cis-[PtCl₂(PPh₃)₂] with an excess of Na[MeNHC(S)NCN] in methanol gives the bis(thiourea monoanion) complex trans-[Pt{SC(=N-CN)NHMe}₂(PPh₃)₂], characterised by NMR spectroscopy and an X-ray crystal structure determination. When cis-[PtCl₂(PPh₃)₂] is reacted with 1 equiv. of Na[MeNHC(S)N-CN] in methanol, with added NaBPh₄, a mixture of isomers of the [Pt{SC(=NHCN)NMe}(PPh₃)₂]⁺ cation is obtained.

Full text of DOI:10.1016/S0020-1693(01)00473-X

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Inorganica Chimica Acta 320 (2001) 101–109
Platinum(II) complexes of chelating and monodentate thiourea
monoanions incorporating chiral, fluorescent or chromophoric
groups
William Henderson a,*, Brian K. Nicholson a, Clifton E.F. Rickard b
a Department of Chemistry, Uni6ersity of Waikato, Pri6ate Bag 3105, Hamilton, New Zealand
b Department of Chemistry, Uni6ersity of Auckland, Pri6ate Bag 92019, Auckland, New Zealand
Received 14 March 2001; accepted 27 April 2001
Abstract
The reaction of cis-[PtCl2(PPh3)2] with trisubstituted thioureas [R1R2NC(ꢀS)NHR3] in refluxing methanol with triethylamine
base, followed by addition of NaBPh4 gives the salts [Pt{SC(ꢀNR1R2)NR3}(PPh3)2]BPh4 in high yield; a range of thiourea
substituents, including chiral, fluorescent and chromophoric groups can be incorporated. The azo dye-derived complex
[Pt{SC(ꢀN(CH2CH2)2O)NC6H4NꢀNC6H4NMe2}(PPh3)2]BPh4 has been characterised by a single-crystal X-ray diffraction study.
The formation of a fluorescein-derivatised platinum–thiourea complex is also described. Reaction of cis-[PtCl2(PPh3)2] with
PhNHC(S)NHPh or EtNHC(S)NHEt, triethylamine and NaBPh4 gives, respectively, [Pt{SC(ꢀNHPh)NPh}(PPh3)2]+ and the
known cation [Pt{SC(ꢀNHEt)NEt}(PPh3)2]+, isolated as tetraphenylborate salts. Reaction of cis-[PtCl2(PPh3)2] with an excess of
Na[MeNHC(S)NCN] in methanol gives the bis(thiourea monoanion) complex trans-[Pt{SC(ꢀNꢁCN)NHMe}2(PPh3)2], character-
ised by NMR spectroscopy and an X-ray crystal structure determination. When cis-[PtCl2(PPh3)2] is reacted with 1 equiv. of
Na[MeNHC(S)NꢁCN] in methanol, with added NaBPh4, a mixture of isomers of the [Pt{SC(ꢀNHCN)NMe}(PPh3)2]+ cation is
obtained. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Platinum complexes; Thiourea complexes
1. Introduction
tracted interest for their biological activity [8]. Metal
cluster complexes with coordinated thiourea monoan-
ions are also well-known [9]. However, there are rela-
tively few examples of mononuclear metal complexes of
simple alkyl- or aryl-substituted thiourea monoanions,
containing N,S-chelated ligands; examples include com-
plexes of chromium(III) [10], rhodium(III) [11], tech-
netium(III) [12], rhenium(V) [13,14], aluminium [15],
ruthenium [16,17], osmium [17] and iridium [17]. For
platinum(II), the topic of this paper, the reaction of the
thiourea dianion complex [Pt{SC(ꢀNEt)NEt}(PPh3)2]
with p-toluenesulfonic acid (TsOH·H2O) gave the
thiourea monoanion complex [Pt{SC(ꢀNHEt)NEt}-
(PPh3)2]OTs [18]. The complex was also prepared by
reaction of [Pt(hfac)(PPh3)2](hfac) [hfac=CF3C(O)-
CHC(O)CF3] with 1,3-diethylthiourea [18]. Palladium
complexes containing monodentate and N,S-chelating
thiourea monoanions have also been described [19].
Thioureas are versatile ligands, able to coordinate to
metal centres either as neutral ligands, as monoanions,
or as dianions [1–4]. An attractive feature of their
chemistry is their ease of synthesis, and the ready
modification of the substituents on nitrogen and hence
their physical and chemical properties. There have been
many studies of benzoyl-substituted thioureas and re-
lated ligands coordinated to platinum(II) [5], and other
metals [6], where the ligand typically bonds as a
monoanion through S and O, giving a six-membered
ring system, though complexes with neutral ligands are
also known [7]. Platinum–thiourea complexes have at-
* Corresponding author. Tel.: +64-7-838-4656; fax: +64-7-838-
4219.
E-mail address: w.henderson@waikato.ac.nz (W. Henderson).
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00473-X

102
W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
In this paper, we report the synthesis of a series of
platinum(II) complexes containing thiourea monoan-
ions, bonded in either N,S-chelating mode (with four-
membered PtꢁNꢁCꢁS rings) or in an S-bonded
monodentate mode. These complexes contrast with
those of trisubstituted thioureas containing benzoyl
substituents, which commonly bond as monoanions to
platinum(II) through S and O giving six-membered
rings [5]. The ease of synthesis of thioureas allows the
synthesis of derivatives containing various chiral,
fluorescent or chromophoric groups, and in this paper
we demonstrate the simplicity of using thioureas to
incorporate such functionalities into platinum
complexes.
2. Results and discussion
2.1. Synthesis and characterisation of complexes of
trisubstituted thiourea monoanions
The thioureas 1a–1f were readily synthesised in good
yields by addition of the appropriate amine to PhNCS
in diethyl ether solution, or by addition of morpholine
to either 4-[(4-isothiocyanatophenyl)azo]-N,N-dimethy-
laniline or fluorescein isothiocyanate, isomer I. Reac-
tions of the complex cis-[PtCl2(PPh3)2] with the
trisubstituted thioureas 1a–1e in refluxing methanol,
with added triethylamine base gives clear solutions
containing cationic platinum–thiourea monoanion
complexes. Addition of NaBPh4 to the hot solutions
results in precipitation of the tetraphenylborate salts in
good to high yields, giving complexes 2a–2e, respec-
tively. Using this general method, a range of function-
alised thiourea complexes can easily be prepared,
including derivatives containing chiral (2c), fluorescent
(2d) or chromophoric (2e) labels.
The formation of the expected platinum–thiourea
cations is readily confirmed by positive-ion electrospray
ionisation mass spectrometry (ESMS) in methanol solu-
tion, which in all cases gives an intense, single M+ ion
for the cation, at the expected m/z values. The 31P{1H}
NMR spectra of complexes 2a–2e show the expected
AB doublet of doublets for two inequivalent PPh3
ligands, with coupling to 195Pt in the ranges 3241–3265
Hz (PPh3 ligands trans to S) and 3401–3444 Hz (PPh3
ligands trans to N). It is noteworthy that for the
complexes 2c and 2d, where two possible isomers could
be formed, only a single set of 31P NMR resonances
was seen, suggesting the formation of a single isomer,
presumably with the bulkiest substituent cis to sulfur.
Satisfactory microanalytical data were observed for all
complexes. The UV–Vis spectrum of the anthracenyl
complex 2d shows similar absorptions as the parent
thiourea 1d, while for the azo dye derivative 2e, the
absorption maximum (430 nm) is shifted from 420 nm
in the free thiourea 1e, presumably due to conjugation
of the azo chromophore and platinum centres. In 2d,
the anthracenyl moiety is remote and not conjugated to
the platinum centre.
When the fluorescein-derived thiourea 1f is reacted
under analogous conditions, the corresponding cation
2f is formed, as shown by ESMS (m/z 1195), but the
attempted precipitation using NaBPh4 was not success-
ful, presumably because the complex is zwitterionic
(with a deprotonated carboxylic acid or phenol group)

W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
103
in the basic reaction medium. In a separate preparation
(without added NaBPh4), addition of water, and pro-
longed standing, resulted in formation of a bright or-
ange solid 2g. The observation of a single m/z 1195 ion
in the positive-ion ES mass spectrum, together with
very similar 31P{1H} NMR coupling constants (3241
and 3453 Hz) to the other complexes 2, suggests that
the complex 2g also contains an N,S-chelated thiourea
monoanion ligand, though satisfactory microanalytical
data could not be obtained for this complex.
The N,S-chelate binding of the thiourea monoanion
to the platinum(II) centre appears to be strong, since
the addition of excess PPh3 to a CDCl3 solution of
complex 2a resulted in no reaction after standing for 24
h.
Fig. 1. Molecular structure and numbering scheme of the cation of
[Pt{SC(ꢀN(CH2CH2)2O)NC6H4NꢀNC6H4NMe2}(PPh3)2]BPh4 (2e),
containing an N,S-chelated thiourea monoanion incorporating an azo
dye.
Table 1
,
Selected bond lengths (A) and bond angles (°) for 2e
PtꢁN(1)
PtꢁP(2)
SꢁC(1)
N(1)ꢁC(6)
N(2)ꢁC(2)
N(3)ꢁN(4)
N(4)ꢁC(12)
2.135(2)
2.2595(7)
1.758(3)
1.432(4)
1.473(4)
1.255(4)
1.426(4)
PtꢁP(1)
PtꢁS
N(1)ꢁC(1)
N(2)ꢁC(1)
N(2)ꢁC(5)
N(3)ꢁC(9)
2.2897(7)
2.3439(7)
1.328(4)
1.339(4)
1.476(4)
1.436(4)
N(1)ꢁPtꢁP(2)
P(2)ꢁPtꢁP(1)
P(2)ꢁPtꢁS
C(1)ꢁSꢁPt
N(1)ꢁC(1)ꢁS
163.02(7)
97.42(3)
95.14(3)
81.22(10)
109.5(2)
N(1)ꢁPtꢁP(1)
N(1)ꢁPtꢁS
P(1)ꢁPtꢁS
98.05(7)
68.68(7)
165.47(3)
100.20(18)
C(1)ꢁN(1)ꢁPt
diphenylthiourea
analogue
[Pt{SC(ꢀNHPh)NPh}-
1
(PPh3)2]BPh4 (3a) shows similar J(PtP) coupling con-
stants of 3198 and 3490 Hz. By comparison, the 1J(PtP)
coupling constants for the thiourea dianion analogues
[Pt{SC(ꢀNPh)NPh}(PPh3)2] (4a) (3103 and 3261 Hz) [3]
and [Pt{SC(ꢀNEt)NEt}(PPh3)2] (4b) (3164 and 3152
Hz) [18] and are slightly smaller, reflecting the slightly
higher trans-influence for the dianionic ligands. For
both complexes 3a and 3b a single set of resonances was
observed in the 31P{1H} NMR spectra, and the com-
plexes are assigned as the isomer with the substituent
on the imine nitrogen cis to the sulfur atom, which is
the expected isomer on steric grounds, and is observed
in other complexes of chelated thiourea monoanions
[15] and dianions [3,18]. Complex 3a is stable in CDCl3
solution in the presence of added pyridine; no conver-
sion to the dianion complex 4a was observed after 24 h.
The attempted synthesis of the cyanothiourea ana-
When PhNHC(S)NHPh is reacted with cis-
[PtCl2(PPh3)2] and excess triethylamine in refluxing
methanol, a clear, pale yellow solution is formed, and
addition of NaBPh4 results in precipitation of the salt
[Pt{SC(ꢀNHPh)NPh}(PPh3)2]BPh4 (3a) as a pale yellow
solid on cooling. Similarly, the reaction with EtNHC-
(S)NHEt gives the analogous complex [Pt{SC(ꢀNHEt)-
NEt}(PPh3)2]BPh4 (3b) as a white solid. The cation
[Pt{SC(ꢀNHEt)NEt}(PPh3)2]+ has been isolated previ-
ously as its hfac salt [18]. The 31P{1H} NMR spectrum
of complex 3b shows two resonances at l 16.2 and 11.1
1
with J(PtP) values of 3233 and 3352 Hz, which com-
pare with the literature values of l 15.7 and 10.4 with
1J(PtP) 3226 and 3318 Hz, respectively [18]. The
logue [Pt{SC(ꢀNHCN)NMe}(PPh3)2]BPh4 gave
a

104
W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
,
2e [1.758(3) A] is shorter than in the thiourea dianion
product which yielded a single intense ion at m/z 865 in
the positive-ion ESMS spectrum, and gave good ele-
mental microanalytical data, but which 31P{1H} NMR
showed to be a mixture of isomers in a 4:1 ratio. The
1J(PtP) coupling constants for both isomers are very
similar (major isomer 5a 3032 and 3205 Hz, minor
isomer 5b 3031 and 3182 Hz) and in the 1H NMR
spectrum the NMe groups of both isomers show phos-
phorus coupling of approximately 5 Hz, indicating that
the NMe group in both isomers is coordinated to
platinum. By comparison, the thiourea dianion complex
,
,
complexes 4a [1.782(5) A] and 4b [1.77(2) A], while CꢁS
bond lengths in the thiourea derivatives 6 [20] and 7
[21], containing, respectively, single and double CꢁS
,
bonds, are 1.801(3) and 1.691(3) A. In comparison, the
,
average CꢀS bond length in thioureas is around 1.681 A
[22]. Likewise, the exocyclic C(1)ꢁN(2) bond in 2e
,
[1.339(4) A] is longer than the exocyclic CꢁN bond of
,
,
4a [1.277(6) A], while that of 4b is similar [1.31(3) A].
Comparison of the metallacyclic CꢁN bonds reveals the
,
opposite trend, with that of 2e [1.328(4) A] being
1
,
,
shorter than those of 4a [1.348(7) A] and 4b [1.42(4) A].
In the isothiourea 6, the double and single CꢁN bond
[Pt{SC(ꢀNꢁCN)NMe}(PPh3)2] shows J(PtP) values of
3171 and 3308 Hz, and an NMe resonance at l 2.16 in
1
,
lengths are 1.267(3) and 1.355(3) A. Taken together,
the H NMR spectrum, showing coupling to phospho-
these data suggest that in complex 2e, there is partial
double bond character in both the CꢁS and CꢁN
bonds. A similar electron delocalisation and double
bond character has been described for the structure of
complex 8, which contains two thiourea monoanions
also bonded in an N,S-chelating mode [17]. In complex
rus of 4 Hz [2]. On the basis of the spectroscopic
evidence, the two isomers are assigned as 5a and 5b,
with the major isomer tentatively assigned as the isomer
with the larger cyano substituent cis to sulfur. The
observation of two isomers may arise due to the small
size of the thiourea substituents in this complex.
,
8 the two CꢁS bond lengths, 1.736(5) and 1.738(5) A,
are somewhat shorter than the CꢁS bond length in 2e,
while the metallacyclic CꢁN bond lengths of 8 [1.330(6)
2.2. X-ray crystal structure of the azo dye deri6ati6e
[Pt{SC(ꢀN(CH2CH2)2O)NC6H4NꢀNC6H4NMe2}-
(PPh3)2]BPh4 (2e)
,
and 1.314(6) A] are similar to that of 2e.
Confirmation of the nature of thiourea coordination
was obtained by a single-crystal X-ray structure deter-
mination on complex 2e. The molecular structure is
shown in Fig. 1, which also gives the atom numbering
scheme. Selected bond lengths and angles are given in
Table 1. To date, there have been ten structure determi-
nations on compounds containing the R2NꢁC6H4ꢁNꢀ
NꢁC6H4ꢁN fragment, but the structure of 2e is the first
of a metal derivative of such an azo dye.
The thiourea is bonded in N,S-chelating mode, form-
ing a four-membered PtꢁSꢁCꢁN ring system. The ge-
ometry about platinum is the expected square-planar,
with two different PtꢁP bond lengths: PtꢁP(1) 2.2897(7)
,
and PtꢁP(2) 2.2595(7) A. This indicates that the sulfur
donor atom has the slightly higher trans influence,
consistent with the 31P NMR assignments. The same
trend is seen in the related platinum(II) thiourea dian-
ion complex [Pt{SC(ꢀNPh)NPh}(PPh3)2] (4a) [PtꢁP
,
2.308(1) and 2.247(1) A] [3], but not in the diethylth-
iourea analogue [Pt{SC(ꢀNEt)NEt}(PPh3)2] (4b) [PtꢁP
,
2.274(6) and 2.269(6) A] [18]. The PtꢁS and PtꢁN bond
,
lengths of 2e [2.3439(7) and 2.135(2) A, respectively] are
longer than the corresponding bond lengths in 4a
,
[2.331(1) and 2.054(3) A] and 4b [2.332(8) and 2.05(3)
,
A], reflecting tighter binding of the dianionic ligand in
the complexes 4.
The geometry of the azo dye part of the molecule
appears normal, with the NꢀN bond distance [1.255(4)
A] similar to that in related azo compounds, such as 9
The thiourea core of the ligand, defined by the atoms
,
N(1), C(1), N(2) and S, is planar to within 0.01 A.
,
Examination of the SꢁC and CꢁN bond lengths of 2e
strongly suggests considerable electronic delocalisation
in the thiourea ligand. Thus, the CꢁS bond distance in
,
[1.263(7) A] [23]. The phenyl ring C(6)ꢁC(11), which is
,
planar to 90.01 A, is inclined at an angle of 60.9° to
the N(1)ꢁC(1)ꢁN(2)ꢁS thiourea plane. The two azo

W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
105
to 195Pt of 2627 Hz, suggesting that the complex is the
trans isomer. In comparison, the thiourea dianion com-
plex [Pt{SC(ꢀNCN)NMe}(PPh3)2], with PPh3 trans to
Table 2
Selected bond lengths (A) and bond angles (°) for molecule 1 of 10a
,
PtꢁP(1)
PtꢁS(1)
2.333(1)
2.338(1)
1.757(5)
1.326(7)
1.159(7)
1.455(6)
1.320(6)
1.430(7)
PtꢁP(2)
PtꢁS(2)
2.340(1)
2.337(1)
1.756(5)
1.334(6)
1.321(6)
1.308(7)
1.159(7)
1.458(7)
1
S, shows J(PtP) values of 3171 and 3308 Hz [2]. A
S(1)ꢁC(1)
N(1)ꢁC(2)
N(2)ꢁC(2)
N(3)ꢁC(3)
N(4)ꢁC(4)
N(6)ꢁC(4)
S(2)ꢁC(4)
N(1)ꢁC(1)
N(3)ꢁC(1)
N(4)ꢁC(5)
N(5)ꢁC(5)
N(6)ꢁC(6)
small resonance at l 17.1 was observed in one prepara-
1
tion of 10a, showing a similar J(PtP) to 10a, 2648 Hz,
and is therefore tentatively assigned to a monosubsti-
tuted
derivative
trans-[PtCl{SC(ꢀNCN)NHMe}-
(PPh3)2]. Complex 10b showed a single 31P resonance at
l 21.6. The presence of NH protons was indicated by a
P(1)ꢁPtꢁS(1)
S(2)ꢁPtꢁS(1)
C(1)ꢁS(1)ꢁPt
86.55(4)
173.13(4)
108.3(2)
P(1)ꢁPtꢁS(2)
P(2)ꢁPtꢁP(1)
C(4)ꢁS(2)ꢁPt
92.55(4)
169.49(4)
109.7(2)
1
broad resonance in the H NMR spectrum (e.g. at l
6.35 for 10a), which disappeared on shaking the solu-
tion with D2O.
Single crystals of complex 10a were obtained by
diffusion of diethyl ether into a dichloromethane solu-
tion of the complex, and an X-ray diffraction study was
carried out. The complex crystallises with two indepen-
dent molecules, and the bond lengths and angles are
similar for both. Selected bond lengths and angles for
molecule 1 are given in Table 2, and the molecular
structure and atom numbering scheme are given in Fig.
2. The structure confirms the trans geometry of the
complex with two S-bonded thiourea monoanions. The
Fig. 2. Molecular structure of one of the two independent molecules
(molecule 1) of trans-[Pt{SC(ꢀN(CN)NHMe}2(PPh3)2] (10a) showing
the atom numbering scheme.
,
PtꢁP [2.333(1) and 2.340(1) A] and PtꢁS [2.337(1) and
,
2.338(1) A] bond lengths are as expected, when com-
pared to the related structure of trans-[Pt(pyridine-2-
,
thiolate)2(PPh3)2] [PtꢁP 2.315(1), PtꢁS 2.343(2) A] [24],
phenyl rings are not coplanar, the angle between the
planes defined by C(6)ꢁC(11) and C(12)ꢁC(17) being
24.4°, due to a twisting of the phenyl rings, combined
with bending of the azo moiety, primarily at N(3)
and are longer than the PtꢁP bond lengths in 2e. The
PtꢁS bond lengths in the dianion complex
[Pt{SC(ꢀNꢁCN)NMe}(cod)] (cod=cyclo-octa-1,5-di-
,
ene) are 2.318(3) and 2.303(3) A (for two independent
,
which lies 0.54 A out of the C(12)ꢁC(17) phenyl plane
molecules) [2]. As with this structure, the cyano sub-
stituent is directed towards the S atom (rather than the
NHMe group). The CꢁS bond lengths of 10a [molecule
1, 1.757(5); molecule 2, 1.751(6) A] are very comparable
with 2e [1.758(3) A], consistent with the bonding as a
,
[N(4) lies 0.18 A out of the same plane].
,
2.3. Synthesis and characterisation of bis(thiourea
monoanion) complexes
,
thiourea monoanion.
In both molecules of 10a, the cyano substituent
[C(5)ꢁN(5)] of one thiourea lies over the platinum, and
accepts a hydrogen bond from the N(3)ꢁH(3) group of
the second thiourea monoanion, with N(3)−H(3)=
Reaction of cis-[PtCl2(PPh3)2] with a large excess of
Na[MeNHC(S)NCN] in methanol at room temperature
affords a very pale yellow solution, from which the
complex trans-[Pt{SC(ꢀNCN)NHMe}2(PPh3)2] (10a)
can be isolated as an off-white solid in high yield by
precipitation with water. The bright yellow palladium
complex 10b can be prepared in analogous fashion.
31P{1H} NMR spectroscopy of 10a showed 2 equiv.
phosphine ligands at l 15.5, showing a small coupling
,
,
0.880 A, N(5)···H(3)=2.065 A, and N(3)−H(3A)···
N(5)=151.19°. There are also intermolecular hydrogen
bonds involving the cyano and NH groups not involved
in intramolecular hydrogen bonding [N(6%)−H(6%)=
,
,
0.880 A, H(6%)···N(2)=2.084 A, N(6%)−H(6%)···N(2)=

106
W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
,
,
163.7°; N(6)−H(6)=0.880 A, H(6)−N(2%)=2.073 A,
N(6)−H(6)···N(2%)=154.4°].
in high yields by addition of the appropriate secondary
amine to a solution of either PhNCS (BDH), 4-
[(4-isothiocyanatophenyl)azo]-N,N-dimethylaniline
The electrospray mass spectrum of a freshly prepared
(Aldrich) or fluorescein isothiocyanate, isomer
(Aldrich).
I
MeOH solution of 10a showed major peaks at m/z 833
[M−MeNHC(S)NCN]+,
865
[M−MeNHC(S)-
NCN+MeOH]+, together with lower intensity ions at
m/z 948 [M+H]+ and m/z 1050 [M+Et3NH]+,
formed from adventitious Et3NH+ ions in the spec-
trometer. After standing for 30 min the m/z 865 ion
was the base peak, with a small m/z 833 ion only, while
after several hours, the m/z 865 ion was the only one
observed, suggesting that solvolysis was occurring. 31P
NMR analysis, however, indicates that complex 10a
was stable in CDCl3 solution for 24 h in the presence of
added methanol. Interestingly, compound 10a melts to
a yellow liquid at 160–162 °C, which then resolidifies
and melts again at 210–214 °C. However, the 31P NMR
spectrum of a sample of 10a heated to 180 °C for 5 min
showed predominantly 10a.
PhNHC(S)N(CH2CH2)2O (1a) [21,29] from PhNCS
and morpholine (BDH) in diethyl ether, colourless crys-
tals, (m.p. lit. 132 °C), ESMS; m/z: 223 [MH]+.
PhNHC(S)NBz2 (1b) from PhNCS and dibenzyl-
amine (BDH) in diethyl ether, m.p. 138–140 °C. ESMS;
m/z: 333 [MH]+.
PhNHC(S)N(Bz)CHMePh (1c) from PhNCS and
(R)-(+)-benzyl a-methylbenzylamine (Aldrich) in di-
ethyl ether, m.p. 186–188 °C. ESMS; m/z: 347 [MH]+.
PhNHC(S)N(Me)CH2Anth (1d) from PhNCS and
9-(methylaminomethyl)anthracene
(AnthCH2NHMe,
Aldrich) in diethyl ether, pale yellow crystals, yield
93%, m.p. 166–168 °C. UV–Vis: umax (nm): 350, 368,
388.
Me2NC6H4NꢀNC6H4NHC(S)N(CH2CH2)2O
(1e)
from 4-[(4-isothiocyanatophenyl)azo]-N,N-dimethylani-
line and morpholine in 5:1 diethyl ether–tetrahydro-
furan, orange microcrystals, yield 84%, m.p.
192–194 °C. ESMS; m/z: 370 [MH]+. UV–Vis: umax
(nm): 420.
3. Experimental
3.1. General experimental procedures
FluorNHC(S)N(CH2CH2)2O (1f) from fluorescein
isothiocyanate, isomer I (FluorNCS) and morpholine in
1:1 tetrahydrofuran–diethyl ether, red powder, yield
87%, m.p. 226–230 °C. ESMS; m/z: 477 [MH]+. UV–
Vis: umax (nm): 456, 482.
31P{1H}, 1H and 13C{1H} NMR spectra were
recorded on a Bruker AC300P instrument in CDCl3
solution (unless otherwise stated), at 121.51, 300.133 or
75.47 MHz, respectively, with chemical shifts relative to
external 85% H3PO4 (31P) or external SiMe4 (1H, 13C).
Electrospray (ES) mass spectra were recorded in posi-
tive-ion mode on a VG Platform II instrument, in
methanol solvent (unless otherwise stated); further de-
tails of the instrumentation have been given previously
[2]. Isotope patterns were calculated using the Isotope
program [25]. Melting points were recorded on a Re-
ichert Jung hotstage apparatus and are uncorrected.
UV–Vis spectra were recorded in methanol solution on
a Perkin–Elmer Lambda 11 spectrophotometer.
Reactions were carried out in LR grade methanol as
the solvent, without prior purification. Dichloro-
methane and diethyl ether were purified by distillation
from calcium hydride and sodium-benzophenone ketyl,
respectively.
3.3. Synthesis of [Pt{SC(ꢀN(CH2CH2)2O)NPh}-
(PPh3)2]BPh4 (2a)
The complex cis-[PtCl2(PPh3)2] (200 mg, 253 mmol),
PhNHC(S)N(CH2CH2)2O (1a) (62 mg, 279 mmol) and
triethylamine (1 ml, excess) were refluxed in methanol
(25 ml) for 5 min to give a colourless solution. NaBPh4
(88 mg, 257 mmol) was added giving a white precipi-
tate. The reaction mixture was cooled in ice, the
product filtered and washed with water (5 ml),
methanol (5 ml) and diethyl ether (5 ml) and dried to
give 285 mg (90%) of 2a as a white powder. M.p.
222–224 °C. Anal. Found: C, 67.4; H, 5.0; N, 2.3. Calc.
for C71H63N2BOP2PtS: C, 67.7; H, 5.0; N, 2.2%. ESMS;
1
m/z (cone voltage 20 V): 940 [M]+. H NMR: l=7.6–
6.1 (m, Ph), 3.4 (m, CH2O), 3.0 (m, CH2N); 31P{1H}
3.2. Materials
1
2
NMR: l=15.5 (d, J(PtP)=3241 Hz, J(PP)=23 Hz,
P trans S), 10.0 (d, 1J(PtP)=3431 Hz, P trans N);
13C{1H} NMR: l=178.5 (t, J(PC)=3 Hz, J(PtC)=99
Hz, CꢀN), 164.5 (m, ipso C of BPh4), 144.1–121.7 (m,
Ph), 65.8 (s, CH2O), 46.6 (s, CH2N).
The complex cis-[PtCl2(PPh3)2] was prepared by lig-
and displacement of the labile 1,5-cyclo-octadiene (cod)
ligand of [PtCl2(cod)] [26] with 2 equiv. of PPh3 in
dichloromethane [27]. The complex [PdCl2(PPh3)2] was
prepared similarly from [PdCl2(cod)] [28]. EtNHC(S)-
NHEt (1,3-diethylthiourea), PhNHC(S)NHPh (1,3-
diphenylthiourea), and the sodium salt Na[MeN-
HC(S)NCN] were used as supplied by Aldrich, and
NaBPh4 was from BDH. Other thioureas were prepared
3.4. Synthesis of [Pt{SC(ꢀNBz2)NPh}(PPh3)2]BPh4 (2b)
The complex cis-[PtCl2(PPh3)2] (300 mg, 379 mmol),
PhNHC(S)NBz2 (1b) (126.5 mg, 380 mmol) and triethyl-

W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
107
amine (1 ml, excess) were refluxed in methanol (20 ml)
for 5 min to give a colourless solution. NaBPh4 (130
mg, 381 mmol) was added giving a white precipitate.
The reaction mixture was cooled in ice, the product
filtered and washed with methanol (5 ml), water (5 ml),
methanol (5 ml) and diethyl ether (5 ml) and dried to
give 380 mg (73%) of 2b as a white powder. M.p.
120–122 °C. Anal. Found: C, 70.5; H, 5.1; N, 2.2. Calc.
for C81H69N2BP2PtS: C, 71.0; H, 5.1; N, 2.0%. ESMS;
Me2NC6H4NꢀNC6H4NHC(S)N(CH2CH2)2O (1e) (96
mg, 260 mmol) and triethylamine (1 ml, excess) were
refluxed in methanol (25 ml) for 5 min to give a bright
orange solution. NaBPh4 (95 mg, 278 mmol) was added
giving an orange precipitate. The reaction mixture was
cooled in ice, the product filtered and washed with
water (10 ml), methanol (5 ml) and diethyl ether (10 ml)
and dried to give 330 mg (93%) of 2e as an orange
powder. M.p. 236–238 °C. Anal. Found: C, 66.8; H,
5.2; N, 5.2. Calc. for C79H72N5BOP2PtS: C, 67.4; H,
5.2; N, 5.0%. ESMS; m/z (cone voltage 20 V): 1088
[M]+. 1H NMR: l=7.9–6.2 (m, Ph), 3.4 (m, br,
CH2O), 3.1 (m, br, CH2N), 3.08 (s, NMe2); 31P{1H}
1
m/z (cone voltage 20 V): 1051, [M]+. H NMR: l=
7.5–5.9 (m, Ph); 4.04 (s, br, CH2); 31P{1H} NMR:
1
2
l=15.5 (d, J(PtP)=3241 Hz, J(PP)=23 Hz, P trans
1
S), 10.0 (d, J(PtP)=3420 Hz, P trans N).
1
2
NMR: l=15.5 (d, J(PtP)=3243 Hz, J(PP)=23 Hz,
P trans S), 10.0 (d, 1J(PtP)=3444 Hz, P trans N).
UV–Vis: umax (nm): 430. X-ray quality crystals of the
complex were grown by diffusion of diethyl ether into a
dichloromethane solution at room temperature (r.t.).
3.5. Synthesis of [Pt{SC(ꢀNBz(CHMePh))NPh}-
(PPh3)2]BPh4 (2c)
The complex cis-[PtCl2(PPh3)2] (200 mg, 253 mmol),
PhNHC(S)NBz(CHMePh) (1c) (87.5 mg, 253 mmol)
and triethylamine (1 ml, excess) were refluxed in
methanol (25 ml) for 5 min to give a colourless solu-
tion. NaBPh4 (88 mg, 257 mmol) was added giving a
white precipitate. The reaction mixture was cooled in
ice, the product filtered and washed with water (5 ml),
methanol (5 ml) and diethyl ether (5 ml) and dried to
give 250 mg (72%) of 2c as a white powder. M.p.
132–134 °C. Anal. Found: C, 70.6; H, 5.2; N, 2.2. Calc.
for C82H71N2BP2PtS: C, 71.1; H, 5.2; N, 2.0%. ESMS;
m/z (cone voltage 20 V): 1065 [M]+. 31P{1H} NMR:
3.8. Synthesis of the fluorescein complex (2g)
The complex cis-[PtCl2(PPh3)2] (100 mg, 126 mmol),
thiourea 1f (60 mg, 0.126 mmol) and triethylamine (1
ml, excess) in methanol (20 ml) was refluxed for 5 min
to give a clear, fluorescent orange solution. Water (60
ml) was added, and the mixture evaporated to dryness.
Water (60 ml) was added and the orange precipitate
filtered, washed with water (2×20 ml) and diethyl
ether (2×20 ml) and dried to give 152 mg of 2g,
m.p.\300 °C. Satisfactory microanalytical data could
not be obtained. Anal. Found: C, 58.5; H, 4.4; N, 2.3.
Calc. for C61H48N2O6P2PtS: C, 61.4; H, 4.1; N, 2.4%.
ESMS; m/z (cone voltage 20 V): 1195 [M]+, 598
[MH]2+. UV–Vis: umax (nm): 456, 482. 31P{1H} NMR
1
2
l=15.8 (d, J(PtP)=3265 Hz, J(PP)=23 Hz, P trans
1
S), 10.0 (d, J(PtP)=3415 Hz, P trans N).
3.6. Synthesis of [Pt{SC(ꢀNPh)N(Me)(CH2Anth)}-
(PPh3)2]BPh4 (2d)
1
(CDCl3 with 10% ethanol): l=14.5 (d, J(PtP)=3241
The complex cis-[PtCl2(PPh3)2] (300 mg, 379 mmol),
PhNHC(S)N(Me)(CH2Anth) (1d) (135 mg, 379 mmol)
and triethylamine (1 ml, excess) were refluxed in
methanol (30 ml) for 5 min to give a pale yellow
solution. NaBPh4 (140 mg, 409 mmol) was added giv-
ing a pale yellow precipitate. The reaction mixture was
cooled in ice, the product filtered and washed with
water (10 ml), methanol (5 ml) and diethyl ether (5 ml)
and dried to give 485 mg (92%) of 2d as a pale yellow
powder. M.p. 230–232 °C. Anal. Found: C, 71.4; H,
5.0; N, 2.1. Calc. for C83H69N2BP2PtS: C, 71.5; H, 5.0;
N, 2.0%. ESMS; m/z (cone voltage 20 V): 1075 [M]+.
1H NMR: l=8.4–6.2 (m, aryl), 2.01 (s, NMe), 1.51 (s,
2
1
Hz, J(PP) 23 Hz, P trans S), 10.1 (d, J(PtP)=3453
Hz, P trans N).
3.9. Synthesis of [Pt{SC(ꢀNHPh)NPh}(PPh3)2]BPh4
(3a)
The complex cis-[PtCl2(PPh3)2] (300 mg, 379 mmol),
PhNHC(S)NHPh (87 mg, 382 mmol) and triethylamine
(1 ml, excess) were refluxed in methanol (20 ml) for 5
min to give a pale yellow solution. NaBPh4 (130 mg,
380 mmol) was added. On cooling in ice, a pale yellow
solid was precipitated, which was filtered and washed
with water (5 ml), methanol (5 ml) and diethyl ether
(5 ml) and dried to give 210 mg (44%) of 3a as a pale
yellow powder. M.p. 133–135 °C. Anal. Found: C,
68.2; H, 5.0; N, 2.5. Calc. for C73H61N2BP2PtS: C, 69.3;
H, 4.9; N, 2.2%. ESMS; m/z (cone voltage 20 V): 946
1
NCH2); 31P{1H} NMR: l=15.7 (d, J(PtP)=3250 Hz,
1
2J(PP)=23 Hz, P trans S), 10.1 (d, J(PtP)=3401 Hz,
P trans N). UV–Vis: umax (nm): 352, 368, 388.
3.7. Synthesis of [Pt{SC(ꢀN(CH2CH2)2O)-
NC6H4NꢀNC6H4NMe2}(PPh3)2]BPh4 (2e)
1
[M]+. H NMR: l=7.3–6.2 (m, Ph); 31P{1H} NMR:
1
2
l=14.1 (d, J(PtP)=3198 Hz, J(PP)=22 Hz, P trans
1
The complex cis-[PtCl2(PPh3)2] (200 mg, 253 mmol),
S), 9.8 (d, J(PtP)=3490 Hz, P trans N).

108
W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
3.10. Synthesis of [Pt{SC(ꢀNHEt)NEt}(PPh3)2]BPh4
(3b)
MeOH]+, 948 (40%) [M+H]+, 1050 (40%)
1
[M+Et3NH]+. 31P{1H} NMR: l=16.4 (s, J(PtP)=
1
2624 Hz); H NMR: l=7.73–7.38 (m, Ph), 6.35 (s, br,
The complex cis-[PtCl2(PPh3)2] (300 mg, 379 mmol),
EtNHC(S)NHEt (50 mg, 379 mmol) and triethylamine
(1 ml, excess) were refluxed in methanol (20 ml) for 5
min to give a pale yellow solution. NaBPh4 (130 mg,
380 mmol) was added. On cooling in ice, a white solid
was precipitated, which was filtered and washed with
water (10 ml), methanol (5 ml) and diethyl ether (10 ml)
and dried to give 320 mg (72%) of 3b as a white
powder. M.p. softens\120 °C, melting 214–216 °C.
Anal. Found: C, 65.9; H, 5.3; N, 2.5. Calc. for
C65H61N2BP2PtS: C, 66.7; H, 5.3; N, 2.4%. ESMS; m/z
(cone voltage 20 V): 850 [M]+. 31P{1H} NMR: l=16.2
NH), 2.20 (s, br, Me). NH proton disappears on shak-
ing with D2O. 13C{1H} NMR: l=173.2 (s, br, CꢀN,
J(PtC)=approximately 35), 135.0–128.0 (m, Ph), 122
(s, CꢂN), 30.4 (s, NMe). Crystals for an X-ray diffrac-
tion study were obtained by diffusion of diethyl ether
into a dichloromethane solution.
3.13. Synthesis of trans-[Pd{SC(ꢀN-CN)NHMe}2-
(PPh3)2] (10b)
Following the procedure for 10b, [PdCl2(PPh3)2] (350
mg, 0.499 mmol) with Na[MeNHC(S)NCN] (500 mg,
3.65 mmol) in methanol (20 ml) gave a bright yellow
suspension which was stirred for 24 h. The product was
filtered, washed with water (10 ml) and diethyl ether (10
ml) and dried in vacuo to give 390 mg (91%) of 10b,
m.p. 158–160 °C. Anal. Found: C, 57.7; H, 4.7; N, 9.8.
Calc. for C42H38N6P2PdS: C, 58.7; H, 4.5; N, 9.8%.
1
2
(d, J(PtP)=3233 Hz, J(PP)=21 Hz, P trans S), 11.1
1
(d, J(PtP)=3352 Hz, P trans N).
3.11. Synthesis of [Pt{SC(ꢀNHCN)NMe}(PPh3)2]BPh4
(5a and 5b)
The complex cis-[PtCl2(PPh3)2] (250 mg, 316 mmol)
and Na[MeNHC(S)NCN] (45 mg, 328 mmol) were
refluxed in methanol (20 ml) for 10 min to give a clear,
pale yellow solution. NaBPh4 (112 mg, 327 mmol) was
added, resulting in formation of a white precipitate.
The mixture was cooled in ice, and the product filtered,
washed with methanol (5 ml), water (5 ml), methanol
(5 ml) and diethyl ether (5 ml) and dried to give 320 mg
(86%) of a white powder. Anal. Found: C, 65.6; H, 5.0;
N, 3.5. Calc. for C63H54N3BP2PtS: C, 65.6; H, 4.7; N,
3.7%. ESMS; m/z (cone voltage 20 V): 865 [M]+.
31P{1H} NMR: Major isomer 5a: l=22.2 (d,
1
31P{1H} NMR: l=21.6 (s). H NMR: l=7.69–7.34
(m, Ph), 6.6 (s, br, NH), 2.23 (s, br, Me). 13C{1H}
NMR: l=176.5 (s, br, CꢀN), 134.7–128.1 (m, Ph), 122
(s, CꢂN), 30.4 (s, NMe).
3.14. X-ray crystal structure determination of 2e
Crystal data: C79H72BN5OP2PtS, Mr=1407.32, mon-
,
oclinic, space group C2/c, a=33.0259(4) A,
,
,
b=10.5148(1) A, c=37.5592(5) A, i=96.2750(10)°,
V=12964.7(2) A3, Z=8, Dcalc=1.442 g cm−3, v (Mo
Ka)=2.298 mm−1, T=150(2) K, 63 277 reflections
measured, 14 215 unique with Rint 0.0377, 12 400 ob-
served with I\2|(I). q range 1.56–27.16°. Final
wR2=0.0646, R1=0.0445 (all data).
2
1J(PtP)=3032 Hz, J(PP)=25 Hz, P trans S), 10.7 (d,
1J(PtP)=3205 Hz, P trans N). Minor isomer 5b:
1
2
l=21.2 (d, J(PtP)=3031 Hz, J(PP)=26 Hz, P trans
1
S), 12.4 (d, J(PtP)=3182 Hz, P trans N).
3.12. Synthesis of trans-[Pt{SC(ꢀNꢁCN)NHMe}2-
(PPh3)2] (10a)
3.15. X-ray crystal structure determination of 10a
Crystal data: C43.5H40.5Cl3N6P2PtS2, Mr=1074.82,
To a suspension of cis-[PtCl2(PPh3)2] (222 mg, 0.281
mmol) in methanol (25 ml) was added an excess (255
mg) of Na[MeNHC(S)NCN] dissolved in water (3 ml).
The platinum complex dissolved giving a clear, very
pale yellow solution, which was stirred overnight at r.t.
Concentration to approximately 6 ml on a rotary evap-
orator at approximately 40 °C, followed by addition of
water (50 ml) afforded an off-white precipitate. This
was filtered, washed with water (5 ml) and dried in
vacuo to give complex 10a (205 mg, 77%). M.p. melts
and resolidifies to a yellow solid at 160–162 °C, then
melts 210–214 °C. Anal. Found: C, 52.4; H, 4.2; N, 8.9.
Calc. for C42H38N6P2PtS: C, 53.2; H, 4.0; N, 8.9%.
ESMS; m/z (cone voltage 20 V): 833 (90%) [M−MeN-
HC(S)NCN]+, 865 (100%) [M−MeNHC(S)NCN+
,
monoclinic, space group P21/c, a=22.3802(5) A,
,
,
b=21.6501(4) A, c=21.2258(5) A, i=113.119(1)°,
V=9458.7(4) A3, Z=8, Dcalc=1.510 g cm−3, v (Mo
Ka)=3.329 mm−1, T=150(2) K, 55 286 reflections
measured, 19 142 unique with Rint=0.0279, 16 665 ob-
served with I\2|(I). q range 0.99–26.46°. The asym-
metric unit consists of two independent molecules of
the complex, together with three molecules of
dichloromethane, one of which was not well defined.
Some of the phenyl carbons have rather high thermal
parameters, possibly due to disorder, which was not
modelled. Final residuals wR2=0.0937, R1=0.0499 (all
data).

W. Henderson et al. / Inorganica Chimica Acta 320 (2001) 101–109
109
(c) U. Bierbach, T.W. Hambley, J.D. Roberts, N. Farrell, Inorg.
Chem. 35 (1996) 4865;
4. Supplementary material
(d) U. Bierbach, T.W. Hambley, N. Farrell, Inorg. Chem. 37
(1998) 708;
(e) U. Bierbach, J.D. Roberts, N. Farrell, Inorg. Chem. 37
(1998) 717;
(f) U. Bierbach, J. Reedijk, Angew. Chem., Int. Ed. Engl. 33
(1994) 1632.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 155641 and 155642 for com-
pounds 2e and 10a, respectively. Copies of this infor-
mation 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).
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(d) L. Hoferkamp, G. Rheinwald, H. Stoeckli-Evans, G. Su¨ss-
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Acknowledgements
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We thank the Universities of Waikato and Auckland
for financial support, the New Zealand Lottery Grants
Board for a grant towards the purchase of the mass
spectrometer, and Johnson Matthey plc for a generous
loan of platinum.
[10] U. Bodensieck, Y. Carraux, H. Stoeckli-Evans, G. Su¨ss-Fink,
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