New cyclometallated platinum(II) compounds with thiosemicarbazones: Crystal and molecular structure of [Pt{4-MeC6H3C(Me)=NN=C(S)NH2}(PPh3)]

Article abstract of DOI:10.1016/S0022-328X(99)00624-5

Treatment of the thiosemicarbazones 3-CH₃(CH₂)₅OC₆H ₄C(Me)=NN(H)C(=S)NH₂ (a), 4-MeC₆H₄C(Me)=NN(H)=C(S)NH₂ (b), C₆H₅C(Et)=NN(H)=C(S)NH₂ (c), C₆H₅C{CH₃(CH₂) ₁₀}=NN(H)=C(S)NH₂ (d) and 4-MeC₆H₄C(Me)=NN(H)=C(S)NHMe (e) with K₂[PtCl₄] gives tetranuclear platinum(II) compounds 1a-1e with deprotonation of the -NH- group and with the ligand acting as a terdentate [C,N,S] moiety. Reaction of 1a-1e with PPh₃ and of 1a with P(4-MeOC₆H₄)₃ yielded mononuclear species 2a-2e and 3a, respectively. Treatment of 1a with the diphosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp), Ph₂P(CH₂)₄PPh₂ (dppb), Ph₂P(CH₂)₅PPh₂ (dpppe), Ph₂P(CH₂)₆PPh₂ (dpph), and 1,1′-ferrocenebis(diphenylphosphine) (dppf) gives dinuclear compounds 4a-10a. In all cases the Pd-S_chelating bond is strong enough to withstand reaction with the phosphorus ligands without bond cleavage. The molecular structure of 2b has been determined by X-ray crystallography. Mononuclear units are held together by hydrogen bonding, forming dimers in the solid state.

Full text of DOI:10.1016/S0022-328X(99)00624-5

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Journal of Organometallic Chemistry 595 (2000) 199–207
New cyclometallated platinum(II) compounds with
thiosemicarbazones: crystal and molecular structure of
[Pt{4-MeC6H3C(Me)ꢀNNꢀC(S)NH2}(PPh3)]
Digna Va´zquez-Garc´ıa a, Alberto Ferna´ndez a, Jesu´s J. Ferna´ndez a,
Margarita Lo´pez-Torres a, Antonio Sua´rez a, Juan M. Ortigueira b, Jose´ M. Vila b,*,
Harry Adams c
a Departamento de Qu´ımica Fundamental e Industrial, Uni6ersidad de La Corun˜a, E-15071 La Corun˜a, Spain
b Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain
c Department of Chemistry, The Uni6ersity, Sheffield S3 7HF, UK
Received 5 August 1999; accepted 5 October 1999
Abstract
Treatment of the thiosemicarbazones 3-CH3(CH2)5OC6H4C(Me)ꢀNN(H)C(ꢀS)NH2 (a), 4-MeC6H4C(Me)ꢀNN(H)ꢀC(S)NH2 (b),
C6H5C(Et)ꢀNN(H)ꢀC(S)NH2 (c), C6H5C{CH3(CH2)10}ꢀNN(H)ꢀC(S)NH2 (d) and 4-MeC6H4C(Me)ꢀNN(H)ꢀC(S)NHMe (e) with
K2[PtCl4] gives tetranuclear platinum(II) compounds 1a–1e with deprotonation of the ꢁNHꢁ group and with the ligand acting as
a terdentate [C,N,S] moiety. Reaction of 1a–1e with PPh3 and of 1a with P(4-MeOC6H4)3 yielded mononuclear species 2a–2e and
3a, respectively. Treatment of 1a with the diphosphines Ph2PCH2PPh2 (dppm), Ph2P(CH2)2PPh2 (dppe), Ph2P(CH2)3PPh2 (dppp),
Ph2P(CH2)4PPh2 (dppb), Ph2P(CH2)5PPh2 (dpppe), Ph2P(CH2)6PPh2 (dpph), and 1,1%-ferrocenebis(diphenylphosphine) (dppf)
gives dinuclear compounds 4a–10a. In all cases the PdꢁSchelating bond is strong enough to withstand reaction with the phosphorus
ligands without bond cleavage. The molecular structure of 2b has been determined by X-ray crystallography. Mononuclear units
are held together by hydrogen bonding, forming dimers in the solid state. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Cyclometallated; Thiosemicarbazone; Platinum; Schiff bases
1. Introduction
When [C,N,O] and [C,N,N] derivatives are treated
with neutral ligands, such as tertiary phosphines, break-
age of the oxygen–metal or nitrogen–metal bonds oc-
curs prior to ring-opening of the five-membered
metalcycle upon continued reaction with the corre-
sponding phosphine. If the cyclometallated compound
is treated with a silver(I) salt previous to treatment with
the phosphine, the chloride ligand is removed from the
coordination sphere of palladium as silver chloride and
its position occupied by the phosphine.
In the present work, we describe the synthesis of the
first cyclometallated platinum(II) compounds derived
from thiosemicarbazone terdentate ligands. These cy-
clometallated compounds present a tetranuclear struc-
ture similar to that found in analogous palladium(II)
complexes [13], having PtꢁSchelating and PtꢁSbridging
bonds.
Cyclometallation has become a relevant part of
organometallic chemistry and several reviews covering
the subject have appeared [1–5]. Cyclometallated com-
pounds show significant applications, such as their use
in regiospecific organic and organometallic synthesis
[6], in insertion reactions [7], in the synthesis of new
metal mesogenic compounds [8] and in catalytic materi-
als [9]. In previous work we have shown that potentially
terdentate ligands such as Schiff bases I [10,11], semi-
carbazones II [12] and thiosemicarbazones III [13] un-
dergo facile metallation with palladium(0), palladium-
(II) and platinum(II) to give compounds with two
five-membered fused rings at the metal centre (Fig. 1).
* Corresponding author. Fax: +34-81-595012.
E-mail address: qideport@usc.es (Jose´ M. Vila)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00624-5

200
D. Va´zquez-Garc´ıa et al. / Journal of Organometallic Chemistry 595 (2000) 199–207
isotopic patterns are in agreement with a tetranuclear
formulation. Related cyclometallated tetranuclear com-
plexes of palladium(II) have been reported by us [13].
1
The absence of the ꢁNHꢁ signal in the H-NMR spec-
tra was indicative of deprotonation of thiosemicarba-
zone ligands. This behaviour has been observed in
coordination compounds of related ligands [14a]. The
importance of the deprotonation of the ꢁNHꢁ groups is
put forward in the reaction between similar 2-methyl-3-
thiosemicarbazones and potassium tetracholoroplati-
nate, which does not take place under similar
conditions to those for ligands a–e. The NH2 protons
Fig. 1.
When the cyclometallated complexes are reacted with
the tertiary monophosphine PPh3, the PtꢁSbridging bond
is cleaved and mononuclear complexes, in which the
platinum atom is bonded to the thiosemicarbazone
ligand, through the carbon, nitrogen and sulfur atoms
and to the monophosphine through the phosphorus,
are obtained. The crystal structure of one of these
compounds is described. The reaction of the cy-
clometallated complexes with the tertiary diphosphines
Ph2P(CH2)6PPh2 (dpph), Ph2P(CH2)5PPh2 (dpppe),
Ph2P(CH2)4PPh2 (dppb), Ph2P(CH2)3PPh2 (dppp),
Ph2P(CH2)2PPh2 (dppe), Ph2PCH2PPh2 (dppm) and
1,1%-ferrocenebis(diphenylphosphine) (dppf) results in
novel dinuclear complexes with the diphosphine bridg-
ing two palladium centres. The potentially beneficial
biological activity of thiosemicarbazones and of their
metal complexes has been discussed [14], a feature we
are studying at present, in order to develop compounds
of pharmaceutical importance.
1
gave rise to a broad signal in the H-NMR spectra,
shifted to higher field by ca. 1.5 ppm as observed in
similar palladium(II) cyclometallated complexes [13].
1
The H-NMR spectra shows that metallation has taken
place and the metallated carbon is the C6 in all cases.
1
In the H-NMR spectra the H5 signal shows the cou-
3
pling to 195Pt with JPtH in the range 45.9–61.5Hz (a
value in agreement with those reported for platinum(II)
cyclometallated compounds [15]).
In compounds 1c and 1d the 1H-NMR spectra
showed the ꢁCH2CH3 and ꢁCH2(CH2)9CH3 resonances
as a doublet of quartets and as a doublet of triplets,
respectively, instead of the expected quartet and triplet
patterns. This is probably due to restricted rotation
around the CꢁEt and CꢁCH2(CH2)9CH3 bonds as a
consequence of the tetrameric structure of the com-
pounds, which brings these groups and a neighbouring
metallated phenyl ring of the tetramer sufficiently close
1
together to give steric hindrance. In the H-NMR of
2. Results and discussion
compounds 1a, 1b and 1e the NꢀCꢁCH3 protons reso-
nance is shifted to lower frequency by ca. 0.5 ppm.
Probably due to the tetrameric structure of the com-
plexes, the methyl groups lie in the shielding area of a
metallated phenyl ring that belongs to an adjacent
metallated thiosemicarbazone ligand.
The thiosemicarbazones a, b, c, d and e were pre-
pared by reaction of thiosemicarbazide or 4-methyl-3-
thiosemicarbazide with the appropriate ketone (see
Section 3 and Table 1). The NH2 protons (a, b, c and d)
gave two characteristic broad resonances in the 1H-
NMR spectra due to the restricted rotation about the
CꢁNH2 bond, which was attributed to the formation of
hydrogen bonding between the CꢀN nitrogen and one
of the NH2 hydrogen atoms. The NH proton showed a
broad signal ca. l 8.8–9. The reaction of the thiosemi-
carbazones with potassium tetrachloroplatinate in
ethanol–water at 60°C gave the cyclometallated
complexes, [Pt{3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)-
NH2}]4 (1a), [Pt{4-MeC6H3C(Me)ꢀNNꢀC(S)NH2}]4
(1b), [Pt{C6H4C(Et)ꢀNNꢀC(S)NH2}]4 (1c), [Pt{C6H4C-
(CH3(CH2)10)ꢀNNꢀC(S)NH2}]4 (1d) and [Pt{4-MeC6-
H3C(Me)ꢀNNꢀC(S)NHMe}]4 (1e), as orange air-stable
solids (see Scheme 1). Preparative details, characterising
microanalytical and IR data are discussed in Section 3.
31P-{1H}- and 1H-NMR data are in Table 1. The
products were characterised by elemental analysis (C,
H, N and S) and the mass (FAB) spectra showed peaks
at m/z 1947 (a), 1600 (b, c), 2106 (d) and 1657 (e) whose
The w(CꢀN) bands are neither shifted or only slightly
shifted to lower wavenumbers upon complex formation
[16], a trend that is opposed to the one observed in
other thiosemicarbazone complexes where this shift is
towards higher wavenumbers [17]. In the present com-
plexes, we suggest this could be attributed to the CꢀN
moiety being part of a five-membered metallacycle, as
has been found by us and others [18,19]. The bands
involving the CꢀS group are often difficult to assign.
Coordination by sulfur induces changes in the position
and intensity of these bands, although the degree of
w(CꢀS) in each band and the proximity of phenyl ring
bands in the IR spectra (especially in complexes with
phosphine ligands) makes a clear assignation of the
vibration modes difficult. Nevertheless, in our opinion
the w(CꢀS) mode in the free ligands may be assigned to
the band at 820–845 cm−1 (Section 3), even if the
bands observed at ca. 1100–1000 cm−1 also contribute
to the CꢀS stretching mode. This band disappears in

D. Va´zquez-Garc´ıa et al. / Journal of Organometallic Chemistry 595 (2000) 199–207
201
Table 1
31P- a and 1H-NMR b data c,d,e
Compound
31P
Aromatic
Others
a
7.28[m, 3H, H2, H5, H6]
8.7[br, 1H, NH]
7.4[s, 1H, NH2]
6.95[dt, 1H, H4, 7.3 f, 2.9 i]
6.4[s, 1H, NH2]
3.99[t, 2H, ꢁCH2O n]
0.92[t, 3H, CH3ꢁ p]
2.26[s, 3H, Me]
5.3[br, 2H, NH2]
3.89[t, 2H, ꢁCH2O n]
0.86[t, 3H, CH3ꢁ p]
1.87[s, 3H, Me]
5.0[br, 2H, NH2]
3.79[t, 2H, ꢁCH2O n]
0.90[t, 3H, CH3ꢁ p]
2.41[s, 3H, Me]
1a
2a
3a
7.44[d, 1H, H5 8.3 f, 46.4 k]
6.66[dd, 1H, H4, 8.3 f, 2.9 i]
6.33[d, 1H, H2, 2.9 i]
22.7 s, 3880 r
17.6 s, 3869 r
6.63[d, 1H, H2 2.4 i]
6.21[dd, 1H, H5, 8.3 f, 43.5 k, 1.9 g]
6.11[dd, 1H, H4, 8.3 f, 2.4 i]
6.61[d, 1H, H2 2.4 i]
5.1[br, 2H, NH2]
3.79[t, 2H, ꢁCH2O n]
0.88[t, 3H, CH3ꢁ p]
2.38[s, 3H, Me]
6.24[dd, 1H, H5, 8.3 f, 44.4 k, 1.9 g]
6.14[dd, 1H, H4, 8.3 f, 2.4 i]
7.57 q[dd, 2H, 11.2 g, 8.8 f]
6.88 q[dd, 2H, 1.7 g 8.8 f]
3.80[s, 3H, MeOphosphine
5.2[br, 2H, NH2]
3.70[t, 2H, ꢁCH2O n]
0.89[t, 3H, CH3ꢁ p]
2.31[s, 3H, Me]
5.1[br, 2H, NH2]
3.80[t, 2H, ꢁCH2O n]
0.89[t, 3H, CH3ꢁ p]
2.41[s, 3H, Me]
5.0[br, 2H, NH2]
3.79[t, 2H, ꢁCH2O n]
0.89[t, 3H, CH3ꢁ p]
2.38[s, 3H, Me]
5.0[br, 2H, NH2]
3.79[t, 2H, ꢁCH2O n]
0.88[t, 3H, CH3ꢁ p]
2.38[s, 3H, Me]
5.2[br, 2H, NH2]
3.77[t, 2H, ꢁCH2O n]
0.87[t, 3H, CH3ꢁ p]
2.36[s, 3H, Me]
5.0[br, 2H, NH2]
3.79[t, 2H, ꢁCH2O n]
0.88[t, 3H, CH3ꢁ p]
2.37[s, 3H, Me]
5.1[br, 2H, NH2]
3.80[t, 2H, ꢁCH2O n]
0.89[t, 3H, CH3ꢁ p]
2.41[s, 3H, Me]
]
4a l
5a
11.6 s, 3943 r
17.7 s, 3843 r
13.3 s, 3941 r
15.2 s, 3813 r
15.4 s, 3819 r
15.2 s, 3815 r
13.4 s, 3870 r
6.41[d, 1H, H2 2.4 i]
6.24[d, 1H, H5, 8.3 f, 56.4 k]
6.14[dd, 1H, H4, 8.3 f, 2.4 i]
6.64[d, 1H, H2 2.6 i]
6.22[dd, 1H, H5, 8.3 f, 43.9 k, 1.9 g]
6.13[dd, 1H, H4, 8.3 f, 2.6 i]
6a
6.61[d, 1H, H2 2.4 i]
6.27[dd, 1H, H5, 8.3 f, 39.6 k, 1.5 g]
6.16[dd, 1H, H4, 8.3 f, 2.4 i]
7a
6.61[d, 1H, H2 2.4 i]
6.27[dd, 1H, H5, 8.3 f, 45.8 k, 1.5 g]
6.18[dd, 1H, H4, 8.3 f, 2.4 i]
8a
6.60[d, 1H, H2 2.4 i]
6.29[dd, 1H, H5, 8.3 f, 45.4 k, 1.9 g]
6.18[dd, 1H, H4, 8.3 f, 2.4 i]
9a
6.60[d, 1H, H2 2.4 i]
6.29[dd, 1H, H5, 8.3 f, 45.7 k, 1.7 g]
6.17[dd, 1H, H4, 8.3 f, 2.4 i]
10a m
6.63[d, 1H, H2 2.4 i]
6.16[m, 2H, H4, H5, 8.3 f, 2.4 i]
b
7.60[d, 2H, H2, H6, 8.2 f]
7.21[d, 2H, H3, H5, 8.2 f]
8.8[br, 1H, NH]
6.8[br, 1H, NH2]
7.4[br, 1H, NH2]
2.38[s, 3H, Me]
2.28[s, 3H, Me]
1b
2b
7.40[s, 1H, H5, 50.7 k]
6.71[d, 1H, H3, 7.6 f]
6.60[d, 1H, H2, 7.6 f]
6.88[d, 1H, H2, 7.6 f]
6.63[d, 1H, H3, 7.6 f]
6.13[s, 1H, H5, 48.4 k]
5.2[br, 2H, NH2]
2.35[s, 3H, Me h]
1.80[s, 3H, Me]
23.0 s, 3854 r
4.9[br, 2H, NH2]
2.39[s, 3H, Me]
1.73[s, 3H, Me h]

202
D. Va´zquez-Garc´ıa et al. / Journal of Organometallic Chemistry 595 (2000) 199–207
Table 1 (Continued)
Compound
31P
Aromatic
Others
c
7.70–7.41 m
8.9[br, 1H, NH]
7.2[br, 1H, NH2]
6.6[br, 1H, NH2]
2.74[q, 2H, CH2CH3, 7.7 f]
1.21[t, 3H, Et, CH2CH3, 7.7 f]
5.3[br, 2H, NH2]
1c
2c
d
7.60[d, 1H, H5, 7.2 f, 61.5 k]
7.02[t, 1H, H3, 7.2 f]
2.62[dq, 1H, CH2CH3, 7.6 f,12.6 j]
1.76[dq, 1H, CH2CH3, 7.6 f,12.6 j]
0.96[t, 3H, CH2CH3, 7.6 f]
4.9[br, 2H, NH2]
6.89[t, 1H, H4, 7.2 f]
6.68[d, 1H, H2, 7.2 f]
22.8 s, 3857 r
7.01[dd, 1H, H2, 7.5 f, 1.2 i]
6.85[dt, 1H, H3, 7.5 f, 1.4 i]
6.52[dt, 1H, H4, 7.5 f, 1.2 i]
6.39[m, 1H, H5, 7.5 f, 1.4 i, 1.4 g, 47.4 k]
7.7-7.1 m
2.86[q, 2H, CH2CH3, 7.6 f]
1.25[t, 3H, CH2CH3, 7.6 f]
9.0[br, 1H, NH]
7.2[br, 1H, NH2]
6.4[br, 1H, NH2]
2.74[q, 2H, ꢁCH2ꢁCiminic, 7.8 f]
5.2[br, 2H, NH2]
1d
2d
e
7.59[d, 1H, H5, 7.3 f, 48.0 k]
7.00[t, 1H, H3, 7.3 f]
2.60[dt, 1H, ꢁCH2ꢁCiminic, 7.8 f, 12.4 j]
1.60[dt, 1H, ꢁCH2ꢁCiminic, 7.8 f, 12.4 j]
6.88[t, 1H, H4, 7.3 f]
6.66[d, 1H, H2, 7.3 f]
21.7 s, 4071 r
6.99[dd, 1H, H2, 7.8 f, 1.5 i]
6.85[dt, 1H, H3, 7.8 f, 1.1 i]
6.52[dt, 1H, H4, 7.8 f, 1.5 i]
6.39[m, 1H, H5, 7.8 f, 1.1 i, 1.7 g, 46.9 k]
7.59[d, 2H, H2, H6, 8.5 f]
7.19[d, 2H, H3, H5, 8.5 f]
4.9[br, 2H, NH2]
2.86[q, 2H, ꢁCH2ꢁCiminic, 7.8 f]
8.7[br, 1H, NH]
7.6[br, 1H, NHCH3]
3.25[d, 3H, NHCH3, 4.9 f]
2.38[s, 3H, Me,]
2.28[s, 3H, Me,]
1e
2e
7.39[s, 1H, H5, 45.9 k]
6.73[m, 2H, H3, H2]
5.2[br, 1H, NHCH3]
2.36[s, 3H, Me h]
1.72[s, 3H, Me]
3.06[d, 3H, NHCH3, 4.9 f]
4.7[br, 1H, NHCH3]
2.44[s, 3H, Me]
21.7 s, 4107 r
6.91[d, 1H, H2, 7.7 f]
6.65[dd, 1H, H3, 7.7 f1.2 i]
6.13[d, 1H, H5, 48.3 k, 1.5 g]
1.75[s, 3H, Me h]
2.96[d, 3H, NHCH3, 4.9 f]
a In CDCl3 unless otherwise stated. Measured at 80.9 MHz (ca.920°C); chemical shifts (l) in ppm (90.1) to high frequency of 85%
H3PO4.
b In CDCl3 unless otherwise stated. Measured at 200 MHz; chemical shifts (l) in ppm (90.01) to high frequency of SiMe4.
c Coupling constants in Hz.
d s, singlet; d, doublet; dd, doublet of doublets; t, triplet; dt doublet of triplets; q, quadruplet; m, multiplet; br, broad.
e in DMSO-d6.
f 3
J
.
HH
g JPH
.
h C(4)ꢁMe.
i 4
J
J
.
.
HH
j 2
HH
k J195
.
PtH
l l(PCH2P)=4.09, [t, 2H, 2JCH P=11.2].
m l(CHFerrocene)=5.0 [br, 2H], 24.3 [m, 2H].
n CH3(CH2)4CH2Oꢁ.
p CH3(CH2)5Oꢁ.
q Shifts for phenyl protons of phosphine ligand.
r J195
.
PtP

D. Va´zquez-Garc´ıa et al. / Journal of Organometallic Chemistry 595 (2000) 199–207
203
Scheme 1. (i) K2[PtCl4]/EtOH/H2O; (ii) PR3 (acetone, 4:1 ratio); (iii) diphosphine (acetone 2:1 molar ratio).
the complexes, in accordance with the loss of the dou-
ble bond character upon deprotonation of the NH
group. This is shown in the lengthening of the CꢁS
bond in the structure of 2b. No w(PtꢁCl) band was
found in the IR spectra of the complexes indicating the
absence of a chlorine ligand in the coordination geome-
try of the platinum atom; furthermore, when 1a–1e
where treated with a silver(I) salt, in order to remove
possible existing chlorine bonded to platinum, no pre-
cipitation of silver chloride was observed.
and Cꢁ CH2(CH2)9CH3 bonds consequent upon cleav-
age of the tetranuclear structure in 1a–1e. The C4ꢁMe
resonance was shifted to lower frequency relative to the
free ligands due to shielding of phosphine phenyl ring,
as we have shown before in related complexes [21],
confirming the relative trans disposition of the nitrogen
atom and the phosphine ligand.
Treatment of 1a with tertiary diphosphines in a 2:1
molar ratio afforded dinuclear complexes of formula
[{Pt[3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)NH2]}2(m-L)]
(4a, L=dppm; 5a, L=dppe; 6a, L=dppp; 7a, L=
dppb; 8a, L=dpppe; 9a, L=dpph; 10a, L=dppf) as
pure air stable solids, which were fully characterised
(see Section 3 and Table 1). The 1H- and 31P-{1H}-
NMR spectra of the compounds have been fully as-
signed. They show phosphorus trans to nitrogen
coordination. There was only one set of signals for each
cyclometallated moiety in the 1H-NMR spectra and
only one singlet for the two 31P nuclei in the 31P-1{H}-
NMR spectra, which suggests the compounds to be
centrosymmetric as we have shown before in related
compounds [12].
2.1. Reacti6ity of the complexes
Treatment of the cyclometallated complexes with ter-
tiary monophosphines gave mononuclear species in
which the bond at platinum to the Sbridging atom was
cleaved. The PtꢁSchelating bond of the terdentate
thiosemicarbazone ligand remains, even when large ex-
cess of monophosphine is used. We believe this is due
to the presence of the stronger PtꢁS bond in terms of
Pearson’s concept [20]. This was observed when com-
plexes 1a–1e and 1a were reacted with PPh3 and (4-
MeOC6H4)3P, respectively, in 1:4 molar ratio. The
1H-NMR spectra showed the H5 resonance in com-
pounds 2a, 3a, 2c, 2d and 2e shifted to a lower fre-
quency and coupled to the phosphorus nuclei
(4JPH:1.5 Hz; this coupling was not observable in
complex 2b). This coupling is smaller, considerably,
than the one found in related thiosemicarbazone com-
plexes of palladium(II). The H5 signals also showed
coupling to 195Pt (3JPtH in the range 43.5–48.4 Hz). The
NꢀCꢁMe resonance for 2a, 3a, 2b and 2e is shifted
slightly with respect to the corresponding free ligand,
whilst the ꢁCH2CH3 (2c) and ꢁCH2(CH2)9CH3 (2d)
resonances appear as a quartet and a triplet, respec-
tively, in agreement with free rotation about the CꢁEt
2.2. Molecular structure of complex 2b
The crystal structure has been determined (Figs. 2
and 3) and confirms the geometry predicted from spec-
troscopic studies. Selected bond lengths and angles are
listed in Table 2.
The crystal structure comprises a molecule of com-
plex 2b. The platinum shows an approximately square
planar coordination and is bonded to a terdentate
thiosemicarbazone system through the aryl C(1) car-
bon, the imine N(1) nitrogen and the thioamide S(1)
sulfur atoms, and to a phosphorus atom of the
triphenylphospine. The angles between adjacent atoms

204
D. Va´zquez-Garc´ıa et al. / Journal of Organometallic Chemistry 595 (2000) 199–207
All the bond distances are within the expected range
with allowance for the strong trans influence of the
phosphorus donor ligand.
The Pt(1)ꢁ(C1) distance of 2.02(2) A is similar to
other platinum aryl carbon bond distances [11]. The
,
,
Pt(1)ꢁN(1) bond length of 2.03(2) A is in agreement
with values given earlier [15]. The PtꢁP distance of
,
2.235(5) A is similar to PtꢁP (phosphorus trans to
nitrogen) bond lengths found in related cyclometallated
complexes [15,22,23].
The geometry around the platinum is planar (r.m.s=
,
0.032 A; plane 1). The metallated ring [Pt(1), C(1),
C(2), C(7), N(1)] and the coordination ring [Pt(1), N(1),
,
N(2), C(8), S(1)] are also planar, (r.m.s.=0.022 A;
,
plane 2) and (r.m.s.=0.0017 A; plane 3), respectively.
Angles between planes are as follows: plane 1/plane 2,
3.3°; plane 1/plane 3, 1.6°; plane 2/plane 3, 4.1°.
The molecular units are stacked in dimers held
together by intramolecular hydrogen bonding be-
tween one thioamide hydrogen atom and the sulfur
Fig. 2. X-ray crystal structure of 2b (hydrogens have been omitted for
clarity).
,
,
atom, N(3)···S(1) 3.44 A, H(3A)···S(1) 2.57 A,
,
N(3)ꢁH(3A)···S(1) 167.2 A, which forms dimers (Fig.
3).
Table 2
,
Selected bond lengths [A] and angles [°] for 2b.
Bond lengths
3. Experimental
Pt(1)ꢁC(1)
Pt(1)ꢁP(1)
S(1)ꢁC(8)
N(1)ꢁC(7)
N(2)ꢁC(8)
2.02(2)
2.235(5)
1.78(2)
1.22(3)
1.25(3)
Pt(1)ꢁN(1)
Pt(1)ꢁS(1)
N(1)ꢁN(2)
N(3)ꢁC(8)
2.03(2)
2.335(5)
1.45(2)
1.36(3)
3.1. Materials and instrumentation
Solvents were purified by standard methods [24].
Chemicals were reagent grade. Potassium tetrachloro-
platinate(II) was purchased from Alfa Products. The
phosphines (4-MeOC6H4)3P, Ph2PCH2PPh2 (dppm),
Ph2P(CH2)2PPh2 (dppe), Ph2P(CH2)3PPh2 (dppp), Ph2P-
(CH2)4PPh2 (dppb), Ph2P(CH2)5PPh2 (dpppe), Ph2P-
(CH2)6PPh2 (dpph), and 1,1%-ferrocenebis(diphenylphos-
phine) (dppf) were purchased from Aldrich-Chemie.
Microanalyses were carried out at the Servicio de Ana´l-
isis Elemental at the University of Santiago using a
Carlo Erba Elemental Analyser, model 1108. NMR
spectra were obtained as CDCl3 or DMSO-d6 solutions
and referenced to SiMe4 (1H) or 85% H3PO4 (31P-{1H})
and were recorded on a Bruker AaC-2005 spectrometer.
All chemical shifts were reported downfield from stan-
dards.
Bond angles
C(1)ꢁPt(1)ꢁN(1)
N(1)ꢁPt(1)ꢁP(1)
N(1)ꢁPt(1)ꢁS(1)
C(8)ꢁS(1)ꢁPt(1)
77.9(6)
176.0(4)
83.7(4)
95.3(7)
C(1)ꢁPt(1)ꢁP(1)
C(1)ꢁPt(1)ꢁS(1)
P(1)ꢁPt(1)ꢁS(1)
C(9)ꢁP(1)ꢁC(15)
98.6(5)
161.4(5)
99.9(2)
102.5(8)
3.2. Preparations
Fig. 3. Hydrogen bonding in 2b X-ray structure.
3.2.1. Preparation of 3-CH3(CH2)5OC6H4C(Me)ꢀ
NN(H)C(ꢀS)NH2 (a)
in the coordination sphere are close to the expected
value of 90°. The most noticeable distortion corre-
sponds to angle C(1)ꢁPt(1)ꢁN(1) 77.9(6)° consequent
upon chelation. The N(1)ꢁPt(1)ꢁS(1) angle of 83.7(4)° is
also less than 90°; the angles C(1)ꢁPt(1)ꢁP(1) and
P(1)ꢁPt(1)ꢁS(1) are thus greater than 90°. The sum of
angles around platinum is 360.1°.
A mixture of thiosemicarbazide (1.00 g, 10.97 mmol)
and hexyloxyacetophenone (2.417 g, 10.97 mmol) and
0.1 cm3 of acetic acid in 50 cm3 of ethanol was heated
under reflux for 5 h. The mixture was then cooled to
−10°C and the white crystalline solid that precipitated
was washed with small portions of cold ethanol and

D. Va´zquez-Garc´ıa et al. / Journal of Organometallic Chemistry 595 (2000) 199–207
205
dried in air. Yield 85%. Anal. Found: C, 61.0; H, 7.7;
N, 14.4; S 11.7. C15H23N3OS Anal. Calc.: C, 61.4; H,
7.9; N, 14.3; S, 11.9%. IR: w(CꢀS) 845 m cm−1; w(CꢀN)
3.2.9. [Pt{C6H4C(CH3(CH2)10)ꢀNNꢀC(S)NH2}]4 (1d)
Yield 60%. Anal. Found: C, 43.4; H, 5.4; N, 7.7; S,
6.1. C76H116N12S4Pt4 Anal. Calc.: C, 43.3; H, 5.5; N,
1620 s cm−1
.
8.0; S 6.1%. IR: w(CꢀN) 1610 s cm−1
.
Thiosemicarbazones b–e were prepared following a
similar procedure.
3.2.10. [Pt{4-MeC6H3C(Me)ꢀNNꢀC(S)NHMe}]4 (1e)
Yield 50%. Anal. Found: C, 31.9; H, 3.1; N, 10.2; S,
7.6. C44H52N12S4Pt4 Anal. Calc.: C, 31.9; H, 3.2; N,
10.1; S 7.7%. IR: w(CꢀN) 1615 s cm−1
.
3.2.2. 4-MeC6H4C(Me)ꢀNN(H)ꢀC(S)NH2 (b)
Yield 80%. Anal. Found: C, 58.3; H, 6.3; N, 20.3; S
15.6. C10H13N3S Anal. Calc.: C, 57.9; H, 6.3; N, 20.3; S,
15.5%. IR: w(CꢀS) 820 m cm−1; w(CꢀN) 1615 sh, s
3.2.11. Preparation of [Pt{3-CH3(CH2)5OC6H3C-
(Me)ꢀNNꢀC(S)NH2}(PPh3)] (2a)
cm−1
.
PPh3 (27.0 mg, 0.103 mmol) was added to a suspen-
sion of 1a (50.0 mg, 0.026 mmol) in acetone (15 cm3).
The solution was stirred for 4 h, the solvent removed in
vacuo and the resulting yellow solid recrystallised from
acetone–n-hexane. Yield 75%. Anal. Found: C, 52.9;
H, 4.7; N, 5.7; S, 4.2. C33H36N3OSPtP Anal. Calc.: C,
3.2.3. C6H5C(Et)ꢀNN(H)ꢀC(S)NH2 (c)
Yield 75%. Anal. Found: C, 58.1; H, 6.5; N, 20.3; S
15.6. C10H13N3S Anal. Calc.: C, 57.9; H, 6.3; N, 20.3; S,
15.5%. IR: w(CꢀS) 820 m cm−1; w(CꢀN) 1620 s cm−1
.
52.9; H, 4.8; N, 5.6; S, 4.3%. IR: w(CꢀN) 1620 s cm−1
.
3.2.4. C6H5C{CH3(CH2)10}ꢀNN(H)ꢀC(S)NH2 (d)
3.2.12. [Pt{4-MeC6H3C(Me)ꢀNNꢀC(S)NH2}(PPh3)]
(2b)
Compound 2b was synthesised following a similar
procedure to that for 2a, but after stirring the cy-
clometallated compound–phosphine mixture, an or-
ange precipitate appeared which was filtered off and
dried in vacuo.
Yield 50%. Anal. Found: C, 68.1; H, 9.3; N, 12.8; S,
9.9. C19H31N3S Anal. Calc.: C, 68.4; H, 9.4; N, 12.6; S,
9.6%. IR: w(CꢀS) 825 m cm−1; w(CꢀN) 1620 sh, s
cm−1
.
3.2.5. 4-MeC6H4C(Me)ꢀNN(H)ꢀC(S)NHMe (e)
Yield 85%. Anal. Found: C, 59.5; H, 6.8; N, 18.9; S
14.6. C11H15N3S Anal. Calc.: C, 59.7; H, 6.8; N, 19.0; S,
Yield 80%. Anal. Found: C, 50.5; H, 4.0; N, 6.5; S,
4.7. C28H26N3SPtP Anal. Calc.: C, 50.7; H,3.9; N, 6.3;
S, 4.8%. IR: w(CꢀN) 1605 sh, s cm−1
.
14.5%. IR: w(CꢀS) 825 s cm−1; w(CꢀS) 1620 m cm−1
.
Compounds 3a and 2e were synthesised following a
similar procedure to that for 2a as orange solids.
Compounds 2c and 2d were synthesised following a
similar procedure to that for 2b as orange solids.
3.2.6. Preparation of
[Pt{3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)NH2}]4 (1a)
To a stirred solution of potassium tetrachloroplati-
nate (200 mg, 0.48 mmol) in water (3 cm3), ethanol was
added (27 cm3). The fine yellow suspension of potas-
sium tetrachloroplatinate obtained was treated with
3-CH3(CH2)5OC6H4C(Me)ꢀNN(H)C(ꢀS)NH2 (a) (160
mg, 0.55 mmol). The mixture was stirred for 48 h at
60°C. After cooling to room temperature, the orange
precipitate formed was filtered off, washed with ethanol
and dried in air. Yield 71%. Anal. Found: C, 37.0; H,
4.0; N, 8.4; S 6.5. C60H84N12O4S4Pt4 Anal. Calc.: C,
3.2.13. [Pt{C6H4C(Et)ꢀNNꢀC(S)NH2}(PPh3)] (2c)
Yield 80%. Anal. Found: C, 50.5; H, 4.2; N, 6.6; S,
4.7. C28H26N3SPtP Anal. Calc.: C, 50.7; H, 3.9; N, 6.3;
S, 4.8%. IR: w(CꢀN) 1580 s cm−1
.
3.2.14. [Pt{C6H4C(CH3(CH2)10)ꢀNNꢀC(S)NH2}(PPh3)]
(2d)
Yield 50%. Anal. Found: C, 57.0; H, 4.0; N, 5.4; S,
4.1. C37H34N3SPtP Anal. Calc.: C, 57.1; H, 4.4; N, 5.4;
37.0; H, 4.3; N, 8.6; S, 6.6%. IR: w(CꢀN) 1620 s cm−1
Compounds 1b–1e were obtained following a similar
.
S, 4.1%. IR: w(CꢀN) 1605 s cm−1
.
procedure as orange solids.
3.2.15. [Pt{4-MeC6H3C(Me)ꢀNNꢀC(S)NHMe}(PPh3)]
(2e)
Yield 30%. Anal. Found: C, 51.5; H, 4.2; N, 6.2; S,
3.2.7. [Pt{4-MeC6H3C(Me)ꢀNNꢀC(S)NH2}]4 (1b)
Yield 66%. Anal. Found: C, 30.2; H, 2.9; N, 10.0; S,
8.4. C40H44N12S4Pt4 Anal. Calc.: C, 30.0; H, 2.8; N,
4.6. C29H28N3SPtP Anal. Calc.: C, 51.5; H, 4.2; N, 6.2;
S, 4.7%. IR: w(CꢀN) 1580 s cm−1
.
10.5; S 8.0%. IR: w(CꢀN) 1610 sh, m cm−1
.
3.2.16. [Pt{3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)NH2}-
(P(4-MeOC6H4)3)] (3a)
Yield 60%. Anal. Found: C, 51.5; H, 5.2; N, 5.2; S,
3.2.8. [Pt{C6H4C(Et)ꢀNNꢀC(S)NH2}]4 (1c)
Yield 70%. Anal. Found: C, 30.4; H,3.0; N, 10.0; S,
8.2. C40H44N12S4Pt4 Anal. Calc.: C, 30.0; H, 2.8; N,
3.9. C36H42N3O4SPtP Anal. Calc.: C, 51.5; H, 5.0; N,
10.5; S 8.0%. IR: w(CꢀN) 1610 sh, s cm−1
.
5.0; S, 3.8%. IR: w(CꢀN) 1615 s cm−1
.

206
D. Va´zquez-Garc´ıa et al. / Journal of Organometallic Chemistry 595 (2000) 199–207
−1
,
3.2.17. Preparation of [{Pt[3-CH3(CH2)5OC6H3C(Me)ꢀ
NNꢀC(S)NH2]}2(v-Ph2PCH2PPh2)] (4a)
radiation u=0.71073 A, v(Mo–Ka)=5.775 mm
F(000)=648.
,
Ph2PCH2PPh2 (20.0 mg, 0.052 mmol) was added to a
suspension of 1a (50.0 mg, 0.026 mmol) in acetone (15
cm3). The solution was stirred for 4 h and the resulting
orange solid filtered off and dried in air. Yield 70%.
Anal. Found: C, 48.5; H, 4.7; N, 6.0; S, 4.9.
C55H64N6O2S2Pt2P2 Anal. Calc.: C, 48.7; H, 4.7; N, 6.2;
Three-dimensional, room-temperature X-ray data
were collected in the range 3.5B2qB45° on a Siemens
P4 diffractometer by the omega scan method. Of the
3430 reflections measured, all of which were corrected
for Lorentz and polarisation effects, 2652 independent
reflections exceeded the significance level ꢀFꢀ/|(ꢀFꢀ)\
4.0. The structure was solved by direct methods and
refined by full-matrix least-squares on F2. Hydrogen
atoms were included in calculated positions and refined
in riding mode. Refinement converged at a final R=
0.0957 (wR2=0.2550 for all 2930 unique data, 168
parameters, mean and maximum l/| 0.000, 0.000),
with allowance for the thermal anisotropy of Pt1, S1,
S, 4.7%. IR: w(CꢀN) 1620 sh, s cm−1
.
Compounds 5a–10a were obtained as orange air-sta-
ble solids following a similar procedure.
3.2.18. [{Pt[3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)-
NH2]}2(v-Ph2P(CH2)2PPh2)] (5a)
Yield 62%. Anal. Found: C, 48.7; H, 4.7; N, 6.6; S,
4.6. C56H66N6O2S2Pt2P2 Anal. Calc.: C, 49.0; H, 4.8; N,
P1 and N1 to N3 only. Minimum and maximum final
−3
6.1; S, 4.7%. IR: w(CꢀN) 1620 sh, m cm−1
.
electron density 3.900 and −5.851 e A
(0.932 A to
,
,
Pt1). A weighting scheme w=1/[|2(Fo2)+(0.2201P)2+
1.1386P] where P=(Fo2 +2F2c)/3 was used in the latter
stages of refinement. Complex scattering factors were
taken from the program package SHELXL-93 [25] as
implemented on the Viglen 486dx computer.
3.2.19. [{Pt[3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)-
NH2]}2(v-Ph2P(CH2)3PPh2)] (6a)
Yield 62%. Anal. Found: C, 49.4; H, 4.7; N, 6.2; S,
4.5. C57H68N6O2S2Pt2P2 Anal. Calc.: C, 49.4; H, 4.9; N,
6.1; S, 4.5%. IR: w(CꢀN) 1620 s cm−1
.
3.2.20. [{Pt[3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)-
NH2]}2(v-Ph2P(CH2)4PPh2)] (7a)
4. Supplementary information
Yield 40%. Anal. Found: C, 50.0; H, 5.3; N, 6.0; S,
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 132969 for compound 2b.
4.7. C58H70N6O2S2Pt2P2 Anal. Calc.: C, 49.8; H, 5.0; N,
6.0; S, 4.6%. IR: w(CꢀN) 1620 sh, s cm−1
.
3.2.21. [{Pt[3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)-
NH2]}2(v-Ph2P(CH2)5PPh2)] (8a)
Yield 70%. Anal. Found: C, 49.9; H, 5.1; N, 5.9; S,
Acknowledgements
4.7. C59H72N6O2S2Pt2P2 Anal. Calc.: C, 50.1; H, 5.1; N,
We thank the Xunta de Galicia (Proyecto
XUGA20913B96) and the Universidad de la Corun˜a
(Spain) for financial support
5.9; S, 4.5%. IR: w(CꢀN) 1620 sh, s cm−1
.
3.2.22. [{Pt[3-CH3(CH2)5OC6H3C(Me)ꢀNNꢀC(S)-
NH2]}2(v-Ph2P(CH2)6PPh2)] (9a)
Yield 45%. Anal. Found: C, 50.2; H, 5.1; N, 6.1; S,
4.5. C60H74N6O2S2Pt2P2 Anal. Calc.: C, 50.5; H, 5.2; N,
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5.9; S, 4.5%. IR: w(CꢀN) 1620 sh, s cm−1
.
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