Interaction of organolead(IV) derivatives with formyl- and acetylferrocene thiosemicarbazones: Coordination versus dephenylation or reductive elimination processes

Article abstract of DOI:10.1016/j.jorganchem.2007.01.049

The reaction of Ph₂PbCl₂ with formylferrocene and acetylferrocene thiosemicarbazones (HTSCs) in methanol afforded the corresponding adduct [Ph₂PbCl₂(HTSC)₂] or, in one case, the complex [Ph₂PbCl(TSC)]. X-ray crystallography of four of the adducts showed them to be all-trans octahedral complexes with the HTSC ligand S-bound to the metal. The IR spectrum of [Ph₂PbCl(TSC)] suggests that the TSC^- ligand is N,S-coordinated. The reaction of Ph₂Pb(OAc)₂ with HTSCs in methanol gave either [Ph₂Pb(OAc)₂(HTSC)₂] or [Ph₂Pb(OAc)(TSC)], which was also obtained from Ph₃Pb(OAc) via a spontaneous dephenylation process. In the former complexes the HTSC ligand is S-coordinated in the solid state. X-ray crystallography of two of the four [Ph₂Pb(OAc)(TSC)] complexes showed that the thiosemicarbazonate anion is N,S-coordinated and the acetate is anisobidentate. Cyclic voltammetry of one [Ph₂PbCl₂(HTSC)₂] adduct and the corresponding [Ph₂Pb(OAc)(TSC)] complex showed that the inductive effect of coordination to lead is transmitted to the ferrocenyl group. Surprisingly, the reaction of Me₂Pb(OAc)₂ with HTSCs afforded only [Pb(TSC)₂] complexes, possibly via redistribution and reductive elimination processes.

Full text of DOI:10.1016/j.jorganchem.2007.01.049

Journal of Organometallic Chemistry 692 (2007) 2234–2244
www.elsevier.com/locate/jorganchem
Interaction of organolead(IV) derivatives with formyl- and
acetylferrocene thiosemicarbazones: Coordination versus
dephenylation or reductive elimination processes
a,
a,
a
b
*
J.S. Casas *, M.V. Castano , M.C. Cifuentes , J.C. Garcıa-Monteagudo ,
´
˜
a
a
a
´
A. Sanchez , J. Sordo , A. Touceda
a
Departamento de Quı´mica Inorga´nica, Facultade de Farmacia, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain
b
Departamento de Quı´mica Fı´sica, Facultade de Farmacia, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain
Received 11 January 2007; received in revised form 26 January 2007; accepted 26 January 2007
Available online 3 February 2007
Abstract
The reaction of Ph2PbCl2 with formylferrocene and acetylferrocene thiosemicarbazones (HTSCs) in methanol afforded the corre-
sponding adduct [Ph2PbCl2(HTSC)2] or, in one case, the complex [Ph2PbCl(TSC)]. X-ray crystallography of four of the adducts showed
them to be all-trans octahedral complexes with the HTSC ligand S-bound to the metal. The IR spectrum of [Ph2PbCl(TSC)] suggests that
the TSCꢀ ligand is N,S-coordinated. The reaction of Ph2Pb(OAc)2 with HTSCs in methanol gave either [Ph2Pb(OAc)2(HTSC)2] or
[Ph2Pb(OAc)(TSC)], which was also obtained from Ph3Pb(OAc) via a spontaneous dephenylation process. In the former complexes
the HTSC ligand is S-coordinated in the solid state. X-ray crystallography of two of the four [Ph2Pb(OAc)(TSC)] complexes showed
that the thiosemicarbazonate anion is N,S-coordinated and the acetate is anisobidentate. Cyclic voltammetry of one [Ph2PbCl2(HTSC)2]
adduct and the corresponding [Ph2Pb(OAc)(TSC)] complex showed that the inductive effect of coordination to lead is transmitted to the
ferrocenyl group. Surprisingly, the reaction of Me2Pb(OAc)2 with HTSCs afforded only [Pb(TSC)2] complexes, possibly via redistribu-
tion and reductive elimination processes.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Diphenyllead(IV) complexes; Triphenyllead(IV); Dephenylation; Dimethyllead(IV); Reductive elimination; Formylferrocene thiosemicarbaz-
ones; Acetylferrocene thiosemicarbazones; X-ray structures; Mass spectra; IR spectra; 1H, 13C and 207Pb NMR spectra; Cyclic voltammetry
1. Introduction
followed by reductive elimination of RX from the unstable
monoorganolead derivative:
Pb–C bonds are rather weak, reported energies ranging
from 134 to 142 kJ molꢀ1 (cf. 226 kJ molꢀ1 for Sn–C
bonds) [1]. Consequently, organolead(IV) halides decom-
pose at room temperature, especially when exposes to light,
although aryl derivatives are somewhat more stable than
alkyl derivatives [2]. The decomposition of dialkyllead
dihalides involves a redistribution reaction,
RPbX3 ! PbX2 þ RX
These reactions hinder the synthesis of diorganolead(IV)
complexes with anionic ligands. In particular, since the
rates of the redistribution and reductive elimination reac-
tions increase with the polarizability of the anion [3], reac-
tions with soft anionic ligands very often lead to Pb(II) and
R3Pb(IV) complexes instead of the R2Pb(IV) derivative.
As a continuation of our research into the coordination
chemistry of organolead(IV) cations [4], here we report the
results of reactions between dimethyl-, diphenyl- or triphe-
nyllead(IV) derivatives and formylferrocene or acetylferro-
cene thiosemicarbazones (HTSCs, see Scheme 1). Metal
2R2PbX2 ! R3PbX þ RPbX3
*
Corresponding authors. Tel.: +34 981528073; fax: +34 981597525.
E-mail addresses: qiscasas@usc.es (J.S. Casas), qitoyi@usc.es (M.V.
Castano).
˜
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.01.049

J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
2235
a saturated dissolution of Ph4Pb in CDCl3 (ꢀ178.0 ppm)
as external reference for 207Pb spectra. HMQC and HMBC
experiments were used for the assignment of signals. All the
above physical measurements were performed by the
RIAIDT services of the University of Santiago de Compos-
tela (USC).
Cyclic voltammograms were obtained in dry CH2Cl2
(10ꢀ3 M solutions) with 0.1 M tetrabutylammonium per-
chlorate as supporting electrolyte using a PAR Model
273 potentiostat/galvanostat, a saturated calomel reference
electrode, a Pt wire as counter electrode, and a graphite
disc as working electrode.
R1
H
R2
H
R3
H
HFTSC
HFMeTSC
HFPhTSC
HFEtTSC
H
H
CH3
Ph
H
H
H
H
Et
HFMeMeTSC
HATSC
H
CH3
H
CH3
H
CH3
CH3
CH3
CH3
CH3
HAMeTSC
HAPhTSC
HAEtTSC
HAMeMeTSC
H
CH3
Ph
H
2.2. Materials
H
Et
Thiosemicarbazide and silver acetate (both from Fluka),
formyl- and acetylferrocene, 4-methyl-, 4-phenyl-, 4-ethyl-,
4-methyl- and 4,4-dimethyl-3-thiosemicarbazides, lead(II)
iodide and triphenyllead(IV) chloride (all from Aldrich),
bromine (from Merck), methyllithium (from Ega-Chemie),
diphenyllead(IV) chloride and hydrochloric acid (from
Panreac), iodomethane (from Probus); and acetic acid
(from Analema); were all used as received. Solvents were
of reagent grade. Me2Pb(OAc)2 was prepared as described
in the literature [7], and Ph2Pb(OAc)2 and [Ph3Pb(OAc)] by
stirring di- or triphenyllead(IV) chloride with silver acetate
in methanol for 5 h; all three were characterized by elemen-
CH3
CH3
R2
R3
N
1
S
1
Fe
N
3
N
2
4
3
5
2
H
6
7
R1
Scheme 1. Thiosemicarbazones used in this work [F = formylferrocene;
A = acetylferrocene; Me, Et, Ph = group on N(1)].
1
tal analysis and H and 13C NMR spectroscopy. The acet-
complexes of HTSCs are of interest because the delocalised
p electron system of the thiosemicarbazone chain can
transmit the electronic effects of the ferrocenyl radical
[5,6], which may allow the use of the ferrocenylthiosemicar-
bazones as a chemical sensor. The reactions carried out in
this work, which in some cases involved dephenylation or
demethylation, led to the isolation of several new com-
plexes of the starting organolead(IV) cations. These prod-
ucts were characterized structurally, and the redox
behaviour was investigated.
ylferrocene ligands were obtained by the method of
Jayasree and Aravindakshan [8], and the formylferrocene
ligands by the method of Wiles and Suprunchuk [9]. Some
physical and spectroscopic properties of these compounds
have been published elsewhere [5,10].
2.3. Synthesis of the complexes
Complexes derived from Ph2PbCl2 or Ph2Pb(OAc)2
were synthesized by mixing a suspension of one of these
compound in methanol with a solution of the correspond-
ing thiosemicarbazone in the same solvent. Metal:ligand
mole ratio (1:1 or 1:2) did not influence the identity of
the product; Table 1 lists the mole ratio giving the better
yield, together with other experimental conditions and
some physical properties of the complexes.
2. Experimental
2.1. Instrumentation
Elemental analyses were performed on
a Fisons
EA1108CHNS-O microanalyser. Melting points (m.p.)
were determined with a Buchi apparatus. Mass spectra
¨
Reaction of Ph3Pb(OAc) lead to its dephenylation and
the formation of the corresponding diphenyllead(IV) com-
plexes (see below).
The reaction of HTSCs with Me2Pb(OAc)2 afforded
Pb(II) complexes (Table 2), suggesting the occurrence of
redistribution and reductive elimination.
Some syntheses are described below in detail as exam-
ples. Analogous information for the remaining complexes
is included in Section 2.3S (here and hereafter, the suffix
‘‘S’’ indicates text, figures or tables included in the Sup-
porting Information).
were recorded in a Hewlett–Packard model 1100 MSD
(ESI, methanolic or chloroform solution) or in a Micro-
mass AUTOSPEC spectrometer (LSIMS, NBA matrix);
the m/z values of metallated fragments are given for the
isotopes 56Fe, 208Pb and 35Cl. IR spectra were obtained
using KBr discs on a Bruker IFS66V FT-IR spectropho-
1
tometer and are reported in cmꢀ1. The H, 13C and 207Pb
NMR spectra of DMSO-d6 solutions were recorded on
Bruker DPX 250, AMX 300 or AMX 500 spectrometers;
chemical shifts in ppm were referred to tetramethylsilane
Caution! Lead is a highly toxic cumulative poison, and
its compounds should be handled carefully [11].
1
using the solvent signal for H and 13C spectra and using

2236
J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
Table 1
Reaction conditions for the synthesis of complexes derived from Ph2PbCl2 and Ph2Pb(OAc)2
Organolead(IV) Compound
Ph2PbCl2
Complex
Mole ratio M:La
Reflux time (h)
Yield (%)
Colour
M.p. (ꢁC)
[Ph2PbCl2(HFTSC)2]
[Ph2PbCl2(HFMeTSC)2]
[Ph2PbCl2(HFPhTSC)2]
[Ph2PbCl2(HFEtTSC)2]
[Ph2PbCl(FMeMeTSC)]
[Ph2PbCl2(HATSC)2]
[Ph2PbCl2(HAMeTSC)2]
[Ph2PbCl2(HAPhTSC)2]
1:2
1:2
1:2
1:2
1:1
1:2
1:2
1:2
1:2
1:2
1:2
1:1
1:1
1:1
1:2
1:2
1:2
1:1
.
65
57
40
54
83
67
72
41
49
58
71
72
46
69
38
33
39
58
Red
177
197
176
179
>250
175
168
153
183
169
138
139
120
214
113
143
105
148
8
12
.
8
.
.
12
.
.
.
8
16
10
.
Orange
Brown
Orange
Brown
Orange
Orange
Brown
Orange
Red
Orange
Red
Orange
Red
[Ph2PbCl2(HAEtTSC)2]
[Ph2PbCl2(HAMeMeTSC)2]
[Ph2Pb(OAc)2(HFTSC)2]
[Ph2Pb(FMeTSC)(OAc)] Æ MeOH
[Ph2Pb(FEtTSC)(OAc)] Æ MeOH
[Ph2Pb(FMeMeTSC)(OAc)]
[Ph2Pb(OAc)2(HATSC)2] Æ (CH3CH2)2O
[Ph2Pb(OAc)2(HAMeTSC)2]
[Ph2Pb(OAc)2(HAEtTSC)2]
[Ph2Pb(AMeMeTSC)(OAc)]
Ph2Pb(OAc)2
Orange
Orange
Orange
Red
.
8
8
a
All the reactions were performed in both 1:1 and 1:2 mole ratio; only ratio giving the better yield is listed.
[Ph2PbCl(FMeMeTSC)]. A solution of HFMeMeTSC
(0.15 g, 0.48 mmol) in 40 mL of hot methanol was added
dropwise, with stirring, to a room-temperature suspension
of Ph2PbCl2 (0.16 g, 0.48 mmol) in 15 mL of methanol. The
mixture was refluxed for 8 h, stirred for a further 12 h, con-
centrated under reduced pressure until cloudy, and kept
uncovered for 12 h. The brown solid obtained was filtered
off and dried under vacuum. Yield 83%; m.p. >250 ꢁC.
Anal. Calc. for C26H26N3SClFePb: C, 43.9; H, 3.7; N,
5.9. Found: C, 44.7; H, 3.7; N, 6.4%. MS (electrospray),
m/z (%): 712 (2) [M+H], 676 (11) [MꢀCl], 512 (100)
[PbCl(FMeMeTSC-HNMe2)], 314 (7) [FMeMeTSC]. IR:
1588s, m(C@N); 822m, m(C@S). 1H NMR (predominant
isomer): d[N(1)CH3] 3.28s(6); d[C(2)H] 7.48s(1); d[Ph2Pb]
7.95d(2) Ho, 7.58t(2) Hm, 7.42t(1) Hp; [3J(H–Pb)]
183.89 Hz. 13C NMR: d[C(1)] 169.7; d[C(2)] 150.2; d[C(3)]
74.3; d[N(1)CH3] 38.7; d[Ph2Pb] 165.8 Ci, 133.6 Co, 130.0
Cm, 129.3 Cp. 207Pb NMR: ꢀ509.0, ꢀ285.0.
Table 2
Complexes derived from Me2Pb(OAc)2
Complex
Yield (%)
Colour
M.p. (ꢁC)
[Pb(FTSC)2]
36
30
61
39
74
21
33
35
42
38
Orange
Yellow
Orange
Yellow
Orange
Orange
Yellow
Orange
Yellow
Orange
205
205
176
204
>250
210
222
142
218
186
[Pb(FMeTSC)2]
[Pb(FPhTSC)2]
[Pb(FEtTSC)2]
[Pb(FMeMeTSC)2]
[Pb(ATSC)2]
[Pb(AMeTSC)2]
[Pb(APhTSC)2]
[Pb(AEtTSC)2]
[Pb(AMeMeTSC)2]
2.3.1. Complexes derived from [Ph2PbCl2]
[Ph2PbCl2(HATSC)2]. A suspension of Ph2PbCl2 (0.11 g,
0.25 mmol) in 15 mL of methanol was added dropwise, with
stirring, to a solution of HATSC (0.15 g, 0.50 mmol) in
15 mL of the same solvent. The resulting solution was stir-
red for 12 h and then concentrated under reduce pressure
until cloudy. After a further 12 h uncovered, the remaining
solution afforded an orange solid that was filtered out and
dried under reduced pressure. Yield 67%; m.p. 175 ꢁC. Anal.
Calc. for C38H40N6S2Cl2Fe2Pb: C, 44.1; H, 3.9; N, 8.1.
Found: C, 43.5; H, 3.8; N, 7.5%. MS (electrospray), m/z
(%): 698 (90) [MꢀHATSCꢀCl], 662 (100) [MꢀATSCꢀ2Cl],
508 (31) [Pb(ATSC)], 301 (14) [HATSC]. IR: 3410s, 3284s,
3165w, m(N–H); 1583vs, m(C@N); 820m, m(C@S). 1H
NMR: d[N(2)H] 9.95s(1); d[N(1)H2] 8.09s(1), 7.65s(1);
d[C(20)H] 2.18s(3); d[Ph2Pb] (8.11d(2) Ho, 7.60t(2) Hm,
7.43t(1) Hp); [3J(H–Pb)] 204.92 Hz. 13C NMR: d[C(1)]
177.6; d[C(2)] 150.3; d[C(3)] 83.0; d[C(20)] 15.1; d[Ph2Pb]
(170.1 Ci, 133.3 Co, 129.4 Cm, 129.3 Cp); [2J(Co–Pb)]
127.0 Hz; [3J(Cm–Pb)] 200.9 Hz. 207Pb NMR: ꢀ506.9.
Single crystals suitable for X-ray study were obtained by
recrystallization from acetone.
2.3.2. Complexes derived from [Ph2Pb(OAc)2] and
[Ph3Pb(OAc)]
[Ph2Pb(OAc)2(HFTSC)2]. A freshly prepared solution of
Ph2Pb(OAc)2 (0.26 mmol) in methanol (15 mL) was added
dropwise, with stirring, to a solution of HFTSC (0.15 g,
0.52 mmol) in the same solvent (15 mL). After 12 h, half
the solvent was removed under vacuum, and the remaining
solution was left uncovered for 12 h. The resulting oil was
broken under reduced pressure, affording an orange solid.
Yield 71%; m.p. 138 ꢁC. Anal. Calc. for C40H42N6O4S2-
Fe2Pb: C, 45.6; H, 4.0; N, 8.0. Found: C, 46.1; H, 4.0; N,
9.1%. MS (FAB, nitrobenzyl alcohol), m/z (%): 934 (2)
[Ph2Pb(FTSC)2], 648 (100) [Ph2Pb(FTSC)], 494 (65)
[Pb(FTSC)], 287 (40) [HFTSC], 212 (22) [HFTSC-
NHC(S)NH2]. IR: 3419m, 3247m,br, 3155m,br, m(N–H);
1599s, m(C@N); 832sh, m(C@S). 1H NMR: d[N(2)H]
11.18s(1); d[N(1)H2] 8.03s(1), 7.61s(1); d[C(2)H] 7.87s(1);

J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
2237
d[Ph2Pb] (7.94d(2) Ho, 7.53t(2) Hm, 7.38t(1) Hp); d[OAc]
1.84s(3); [3J(H–Pb)] 197.42 Hz. 13C NMR: d[C(1)] 176.6;
d[C(2)] 143.2; d[C(3)] 78.9; d[Ph2Pb] (167.6 Ci, 132.2 Co,
129.6 Cm, 129.1Cp); d[OAc] (171.2 C@O, 23.0 CH3);
[2J(Co–Pb)] 122.1 Hz; [3J(Cm–Pb)] 183.1 Hz. 207Pb NMR:
ꢀ659.6.
(0.15 g, 0.50 mmol) in 25 mL of methanol. After stirring
for 12 h, the orange solid obtained was filtered out and
dried under reduced pressure. Yield 21%; m.p. 210 ꢁC.
Anal. Calc. for C26H28N6S2Fe2Pb requires: C, 38.7; H,
3.5; N, 10.4. Found: C, 38.8; H, 3.8; N, 10.4%. MS (electro-
spray), m/z (%): 1316 (9) [Pb2(ATSC)3], 809 (100) [M+H],
508 (57) [MꢀATSC], 302 (6) [HATSC+H], 301 (2)
[HATSC]. IR: 3483s, 3415s, 3364m, 3282m, m(N–H);
[Ph2Pb(FEtTSC)(OAc)] Æ MeOH. A freshly prepared
solution of Ph2Pb(OAc)2 (0.48 mmol) in methanol
(15 mL) was added dropwise, with stirring, to a solution
of HFEtTSC (0.15 g, 0.48 mmol) in 10 mL of the same sol-
vent. The mixture was refluxed for 16 h, and then stirred
for a further 12 h. The remaining solution was left uncov-
ered for 12 h, and the orange solid obtained was filtered
off and dried under vacuum. Yield 46%; m.p. 120 ꢁC. Anal.
Calc. for C29H33N3O3SFePb: C, 45.4; H, 4.3; N, 5.5.
Found: C, 44.8; H, 4.3; N, 5.6%. MS (FAB, nitrobenzyl
alcohol), m/z (%): 676 (71) [MꢀMeOHꢀOAc], 522 (100)
[Pb(FEtTSC)], 315 (30) [HFEtTSC], 212 (45) [HFEtTSC-
NHC(S)NHEt]. IR: 3356m, m(N–H); 1567sh, m(C@N);
796sh, m(C@S); 1602m, mas(COO); 1410m, ms(COO). 1H
NMR: d[N(1)H] 7.24d(1); d[N(1)CH2] 3.42m(2);
d[N(1)CH3] 1.21t(3); d[C(2)H] 7.46s(1); d[Ph2Pb] (7.93d(2)
Ho, 7.51t(2) Hm, 7.37t(1) Hp); d[OAc] 1.74s(3); [3J(H–Pb)]
189.14 Hz. 13C NMR: d[C(1)] 177.5; d[C(2)] 149.3; d[C(3)]
74.7; d[N(1)CH2] 38.4; d[N(1)CH3] 14.3; d[Ph2Pb] (166.4
Ci, 133.5 Co, 129.6 Cm, 129.1 Cp); d[OAc] (167.8 C@O,
23.4 CH3); [2J(Co–Pb)] 122.6 Hz; [3J(Cm–Pb)] 184.8 Hz.
Single crystals suitable for X-ray study were obtained from
methanol.
1
1563vs, m(C@N); 821m, br, m(C@S). H NMR: d[N(1)H2]
6.93s(2); d[C(20)H] 2.13s(3). 13C NMR: d[C(1)] 170.2;
d[C(2)] 152.9; d[C(3)] 84.3; d[C(20)] 16.1.
2.4. X-ray crystallography
Crystal data were collected at room temperature on a
Bruker SMART CCD 1000 diffractometer [12] using
graphite-monochromated Mo Ka radiation (wavelength
˚
0.71073 A). The structures were solved using direct meth-
ods followed by normal difference Fourier techniques.
The hydrogen atoms were included in the model at ideal
positions. Full-matrix least-squares refinement was per-
formed treating the non-H atoms anisotropically. The
atomic scattering factors used were those provided with
SHELX-97 [13]. Other programs used were ORTEP-3 [14] and
PLATON-98 [15]. Crystal and refinement data for the com-
pounds are listed in Table 3.
3. Results and discussion
The same complex was obtained from Ph3Pb(OAc) as
follows: a solution of triphenyllead(IV) acetate (0.48 mmol)
in 15 mL of methanol was added dropwise to a solution of
HFEtTSC (0.15 g, 0.48 mmol) in 15 mL of the same sol-
vent. After 12 h of stirring, the solution was concentrated
to half volume and the orange solid formed was isolated
and dried under vacuum (yield 15%). Analytical data and
physical and spectroscopic properties indicate that the solid
is [Ph2Pb(FEtTSC)(OAc)].
3.1. Synthesis of the complexes
3.1.1. Reactions of Ph2PbX2 (X = Cl, OAc)
The reactions of Ph2PbX2 (X = Cl, OAc) with HTSCs in
methanol afforded either 1:2 adducts [Ph2PbX2(HTSC)2] or
1:1 complexes in which an Xꢀ ligand had been replaced by
TSCꢀ (Scheme 2).
The stoichiometry of the reaction mixture (all reactions
were performed with both 1:1 and 1:2 metal:HTSC ratios)
had no influence on the identity of the product, which was
generally unique, but it did affect yield, 1:2 adducts being
obtained in greater yield with 1:2 ratio and 1:1 complexes
with 1:1 ratio. It is possible that complexes of both stoichi-
ometries exist in solution, and that which is isolated
depends on their relative solubilities. Only in the reactions
of Ph2Pb(OAc)2 with HFPhTSC and HAPhTSC did failure
to isolate a pure product suggest that the solids obtained
might be a mixture of 1:1 and 1:2 complexes, a result that
may perhaps have been due to the deactivating influence of
the HTSC phenyl on its carbothioamide group.
2.3.3. Complexes derived from [Me2Pb(OAc)2)]
[Pb(FTSC)2].
A
freshly prepared solution of
Me2Pb(OAc)2 (0.50 mmol) in 15 mL of methanol was
added dropwise, with stirring, to a solution of HFTSC
(0.14 g, 0.50 mmol) in the same solvent (25 mL). After
12 h stirring, the orange solid obtained was filtered out
and dried under vacuum. Yield 36%; m. p. 205 ꢁC. Anal.
Calc. for C24H24N6S2Fe2Pb: C, 37.0; H, 3.1; N, 10.8.
Found: C, 36.6; H, 3.2; N, 10.7%. MS (electrospray), m/z
(%): 1274 (10) [Pb2(FTSC)3], 781 (100) [M+H], 494 (81)
[M-FTSC], 288 (17) [HFTSC+H], 287 (38) [HFTSC]. IR:
3466m, 3424s, 3373m, 3297m, m(N–H); 1569vs, m(C@N);
The singular displacement of a Clꢀ ligand by HFMe-
MeTSC deserves a comment. In this HTSC, both the
N(1)H2 hydrogens had been replaced by methyl groups.
This double substitution eliminates the intramolecular
N(1)–Hꢁ ꢁ ꢁN(3) hydrogen bond, thereby allowing free rota-
tion about the C(1)–N(2) bond and facilitating the N(3),S-
coordination that is suggested by spectroscopic data (vide
infra). It therefore seems possible that in this reaction the
1
820m, br, m(C@S). H NMR: d[N(1)H2] 7.00s(2); d[C(2)H]
8.22s(1). 13C NMR: d[C(1)] 173.1; d[C(2)] 146.3; d[C(3)]
80.1.
[Pb(ATSC)2].
A
freshly prepared solution of
Me2Pb(OAc)2 (0.50 mmol) in 15 mL of methanol was
added dropwise, with stirring, to a solution of HATSC

Table 3
Crystallographic data for the complexes studied by X-ray diffraction
[Ph2PbCl2(HFMeTSC)2] [Ph2PbCl2(HATSC)2] [Ph2PbCl2(HAMeTSC)2] Æ 2MeOH [Ph2PbCl2(HAEtTSC)2] Æ 2(CH3)2CO [Ph2Pb(OAc)
(FMeTSC)] Æ MeOH
[Ph2Pb(OAc)
(FEtTSC)] Æ MeOH
Empirical formula
C
38H40Fe2 N6Cl2S2 Pb
C38H40Fe2 N6Cl2S2
Pb
C42 H52 Fe2 N6 Cl2 O2 S2 Pb
C48 H60 Fe2 N6 Cl2 O2 S2 Pb
C28 H31 Fe N3 O3
Pb
S
C29 H33 Fe N3 O3
Pb
S
Formula weight
Colour, habit
Crystal size
Crystal system, space
group
Unit cell dimensions
1034.67
Red, prism
0.39 · 0.13 · 0.08 mm
Triclinic,P1
1034.67
Red, prism
1126.81
Red, needle
1206.93
Red, prism
0.55 · 0.49 · 0.17 mm
Monoclinic, P2(1)/c
752.66
Red, prism
766.68
Red, prism
0.46 · 0.37 · 0.15 mm 0.43 · 0.08 · 0.06 mm
Monoclinic, P2(1)/n
0.20 · 0.18 · 0.16 mm 0.55 · 0.30 · 0.22 mm
Orthorhombic,
P212121
ꢀ
Monoclinic, P2(1)/c
Orthorhombic,
P212121
˚
a (A)
9.0796(15)
9.6305(16)
12.851(2)
104.269(3)
99.181(3)
112.391(2)
8..9140(15)
7.7592(13)
27.606(5)
–
11.4938(5)
16.0036(7)
12.3901(5)
–
92.608(3)
–
14.948(3)
11.0324(18)
15.885(3)
–
10.405(2)
15.200(3)
18.138(3)
–
–
–
10.5052(14)
15.633(2)
18.344(3)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
–
–
–
94.692(3)
–
1903.0(6) A
98.213(3)
–
2592.8(7) A
3
˚
3
˚
3
3
˚
3
˚
3
˚
˚
Volume
965.8(3) A
2276.70(17) A
2868.6(9) A
3012.6(7) A
Z; Calculated density 1; 1.779 Mg/m3
2; 1.806 Mg/m3
5.452 mmꢀ1
293
2; 1.644 g/m3
4.568 mmꢀ1
293
2; 1.546 Mg/m3
4.017 mmꢀ1
293
4, 1.743 Mg/m3
6.473 mmꢀ1
293
4, 1.690 Mg/m3
6.165 mmꢀ1
293
Absorption coefficient 5.372 mmꢀ1
T (K)
293
F (000)
510
1020
1124
1212
1472
1504
Reflections collected/
10,953/3931 (0.0230)
11,130/3875 (0.0212) 34,619/5644 (0.0482)
15,965/5301 (0.0237)
12,528/5277 (0.0301) 11,422/5438 (0.0174)
unique (Rint
)
Final R indices
[I > 2sigma(I)]
R1 = 0.0170
R1 = 0.0249
R1 = 0.0289
R1 = 0.0241
R1 = 0.0269
R1 = 0.0270
wR2 = 0.0393
wR2 = 0.0581
wR2 = 0.0517
wR2 = 0.0602
wR2 = 0.0506
wR2 = 0.0690

J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
2239
.
with these spectroscopic changes, a precipitate forms that
is presumably the Pb(II) complex, and a new signal appears
at 2.70 ppm that may plausibly belong to the FTSC-Me.
These data not only support reactions 2 and 3, but also
indicate that [Me3Pb(FTSC)] undergoes the redistribution
reaction [2]:
[Ph2PbX2 (HTSC)2]
Ph2PbX2
+
nHTSC
n = 1,2; X = Cl, AcO
[Ph2PbX(TSC)] + HX
Scheme 2.
2½Me3PbðFTSCÞꢂ ! Me4Pb þ ½Me2PbðFTSCÞ2ꢂ
ð4Þ
making the overall process
displacement of the Clꢀ may have been facilitated by prior
coordination of HFMeMeTSC in a chelated mode. No suc-
cess was achieved when the displacement of Clꢀ by other
HTSC ligands was attempted by performing the reaction
additionally in a basic medium.
That most of 1:1 complexes derived from Ph2Pb(OAc)2
rather than Ph2PbCl2 may have been due to acetate being
more basic than chloride, which must have aided deproto-
nation of the thiosemicarbazone.
3½Me2PbðFTSCÞ2ꢂ ! Me4Pb þ 2½PbðFTSCÞ2ꢂ
þ 2FTSC ꢀ Me
and accounting for the observed yields of the HFPhTSC
and HFMeMeTSC complexes.
ð5Þ
3.2. X-ray structures of the complexes
Table 4 lists selected bond lengths and angles in the
complexes studied crystallographically, and Figs. 1 and 2
show the structures and numbering schemes of two
examples.
3.1.2. Reactions of Ph3Pb(OAc) and Me2Pb(OAc)2
When the starting organolead compound was Ph3Pb-
(OAc), dephenylation occurred:
In all the compounds derived from Ph2PbCl2
{[Ph2PbCl2(HFMeTSC)2], [Ph2PbCl2(HATSC)2], [Ph2Pb-
Cl2(HAMeTSC)2] Æ 2MeOH and [Ph2PbCl2(HAEtTSC)2] Æ
2(CH3)2CO}, an all-trans octahedral arrangement is
adopted by the six ligands, namely the two phenyl groups,
the two chloride ligands and the sulphur atoms of the two
HTSC ligands (see Fig. 1 for [Ph2PbCl2(HATSC)2] and
Fig. 1S for the other adducts). The bond angles are close
to their ideal values (see Table 4). In [Ph2PbCl2(HATSC)2]
Ph3PbðOAcÞ þ HTSC ! ½Ph2PbðOAcÞðTSCÞꢂ þ HPh ð1Þ
Yields, however, were very low (see Section 2.3.2).
The reactions of Me2Pb(OAc)2 with HTSCs afforded
Pb(II) complexes almost instantaneously, even at low tem-
perature and in the absence of light, showing that the Pb–
Me bond is less stable than the Pb–Ph bond. It may be
assumed that after substitution of TSCꢀ for AcOꢀ there
occurred a redistribution reaction,
˚
the Pb-S distance, 2.8966(10) A, is clearly longer than the
2½Me2PbðTSCÞ2ꢂ ! ½MePbðTSCÞ3ꢂ þ ½Me3PbðTSCÞꢂ
ð2Þ
˚
2.819(2) A observed in [Ph2PbCl2(HSTSC)2] (HSTSC =
salicylaldehyde thiosemicarbazone), a similar centrosym-
metric adduct [4c], suggesting that HATSC is less basic
than HSTSC. The Pb-Cl distance in [Ph2PbCl2(HATSC)2],
followed by reductive elimination from the monomethyl
complex:
½MePbðTSCÞ3ꢂ ! TSC ꢀ Me þ ½PbðTSCÞ2ꢂ
ð3Þ
˚
˚
2.7471(9) A, is also longer than in the HSTSC adduct
[2.715(3) A], but clearly shorter than iꢀn polymeric
(see Section 1). However, since this process can afford at
most a 50% yield of the lead(II) complex, the fact that
yields of 61% and 74% were obtained with HFPhTSC
and HFMeMeTSC (see Table 2) shows that, at least in
these cases, some alternative decomposition pathway must
also have been operative. To investigate this, the 1H NMR
spectrum of a 1:1 solution of Me2Pb(OAc)2 and HFTSC in
CD3OD was monitored during several days. Within 24 h,
the organometallic signal at 2.19 ppm [2J(1H–207Pb) =
150 Hz)] was replaced by three new peaks at 0.72 ppm
[2J(1H–207Pb) = 62 Hz], 1.37 ppm [2J(1H–207Pb) = 81 Hz]
and 2.46 ppm (no coupling constant could be measured
˚
Ph2PbCl2 [2.795(6) A], in which all the Cl anions are
bridging ligands [16]. The C(1)–S(1) bond length,
˚
˚
1.716(4) A, is greater than in HATSC [1.693(3) A] [17], sug-
gesting partial evolution to the thiol form in the adduct.
The other distances in the thioamide group are not signif-
icantly changed. The thiosemicarbazone chain C(2)N(3)-
N(2)C(1)S(1)N(1) is practically planar (rms = 0.0823) and
retains the same configuration as in the free ligand, E about
both the C(1)–N(2) and C(2)–N(3) bonds. The E configura-
tion about C(1)–N(2) allows the formation of two intramo-
lecular hydrogen bonds, N(1)–H(1A)ꢁ ꢁ ꢁN(3) [N(1)ꢁ ꢁ ꢁN(3)
1
˚
= 2.639(4), N(1)–H(1A) = 0.86, H(1A)ꢁ ꢁ ꢁN(3) = 2.30 A;
for this last signal). Although H NMR data for methyl-
N(1)–H(1A)ꢁ ꢁ ꢁN(3) = 104.0ꢁ] and N(2)–H(2)ꢁ ꢁ ꢁCl(1) [N(2)
ꢁ ꢁ ꢁCl(1) = 3.209(3), N(2)–H(2) = 0.86, H(2)ꢁ ꢁ ꢁCl(1) =
lead(IV) derivatives are somewhat scarce, it seems that
2
the J(1H–207Pb) coupling constant of Me4Pb lies close to
˚
2.71 A; N(2)–H(2)ꢁ ꢁ ꢁCl(1) = 118.0ꢁ]. This intramolecular
60 Hz, those of trimethyllead derivatives between 70 and
90 Hz, and those of dimethyllead(IV) compounds near
150 Hz [2]. Accordingly, those measured in the Me2P-
b(OAc)2/HFTSC reaction after 24 h probably belong to
Me4Pb, Me3Pb and MePb, respectively. Simultaneously
hydrogen-bonding scheme is common to all four Ph2PbCl2
adducts (see Table 1S). In [Ph2PbCl2(HATSC)2] there is
additionally an intermolecular hydrogen bond [N(1)ꢁ ꢁ ꢁ
Cl(1)# = 3.273(3), N(1)–H(1B) = 0.86, H(1B)ꢁ ꢁ ꢁCl(1)# =

Table 4
Selected bond lengths (A) and angles (ꢁ) in the complexes
˚
[Ph2PbCl2(HFMeTSC)2]
[Ph2PbCl2(HATSC)2]
[Ph2PbCl2(HAMeTSC)2] Æ
[Ph2PbCl2(HAEtTSC)2] Æ
[Ph2Pb(OAc)(FMeTSC)] Æ
[Ph2Pb(OAc)(FEtTSC)] Æ
2MeOH
2(CH3)2CO
MeOH
MeOH
Pb(1)–S(1)
Pb(1)–Cl(1)
2.8824(7)
2.6768(7)
2.8966(10)
2.7471(9)
2.8522(10)
2.7229(10)
2.8214(9)
2.7063(8)
2.5397(17)
–
2.5367(14)
–
Pb(1)–C(21)
Pb(1)–C(15)
Pb(1)–N(3)
Pb(1)–O(1)
Pb(1)–O(2)
S(1)–C(1)
C(1)–N(1)
C(1)–N(2)
N(1)–C(13)
2.190(2)
–
–
–
2.183(3)
–
–
–
2.185(3)
–
–
–
2.188(3)
–
–
–
2.194(6)
2.187(6)
2.479(4)
2.326(4)
2.923(5)
1.755(6)
1.343(7)
1.313(7)
1.443(8)
1.381(7)
1.287(7)
1.450(8)
–
2.194(5)
2.197(6)
2.477(4)
2.318(4)
2.911(5)
1.757(6)
1.352(7)
1.297(7)
1.449(10)
1.375(6)
1.292(7)
1.447(7)
–
–
–
–
–
1.704(2)
1.319(3)
1.338(3)
1.444(4)
1.386(3)
1.284(3)
1.436(3)
98.770(19)
90.43(7)
81.230(19) (a)
–
1.716(4)
1.309(5)
1.343(4)
–
1.395(4)
1.293(4)
1.471(5)
89.49(3)
1.709(4)
1.303(5)
1.352(5)
1.456(5)
1.390(4)
1.286(5)
1.461(5)
92.81(3)
90.34(10)
87.19(3) (a)
–
1.709(3)
1.306(4)
1.344(4)
1.458(5)
1.387(3)
1.285(4)
1.467(4)
91.57(3)
90.81(9)
88.43(3) (c)
–
N(2)–N(3)
N(3)–C(2)
C(2)–C(3)
S(1)–Pb(1)–Cl(1)
Cl(1)–Pb(1)–C(21)
Cl(1)–Pb(1)–S(1)#1
S(1)–Pb(1)–N(3)
O(1)–Pb(1)–O(2)
S(1)–Pb(1)–O(1)
N(3)–Pb(1)–O(2)
C(15)–Pb(1)–C(21)
90.24(9)
90.51(3) (b)
–
–
–
–
–
–
–
–
–
73.66(14)
47.86(15)
79.85(13)
158.58(17)
145.8(2)
73.55(10)
48.23(14)
79.03(11)
159.25(13)
143.55(19)
–
–
–
–
–
–
–
–
–
–
–
–
#1(a) ꢀx + 1, ꢀy, ꢀz; (b) ꢀx, ꢀy, ꢀz; (c) ꢀx + 1, ꢀy + 1, ꢀz.

J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
2241
143.55(19)ꢁ, differs widely from the ideal 180ꢁ, and the
small bite of the ligands make the equatorial angles nar-
rower than 90ꢁ. Nevertheless, the equatorial fragment
[C(3)C(2)N(3)N(2)C(1)S(1)N(1)C(13)Pb(1)O(1)O(2)C(33)]
is practically planar (rms = 0.0617).
Deprotonation and metallation change the thiosemicar-
bazide moiety in the usual ways [20]. Thus in
[Ph2Pb(OAc)(FMeTSC)] Æ MeOH the C(1)–S(1) bond is
longer than in the corresponding adduct [1.755(6) as
˚
against 1.704(2) A; see Table 4] in accordance with the
Fig. 1. ORTEP drawing of [Ph2PbCl2(HATSC)2], showing the molecular
structure and the labelling scheme used.
greater evolution of the ligand towards the thiol form,
and the configuration about the N(2)–C(1) bond is Z
instead of E to allow the observed N(3),S-chelation. There
are no significant differences in Pb–C bond length between
adducts and complexes.
Though not bound to the metal, the methanol links the
molecules of the FRTSCꢀ complexes via two intermolecu-
lar hydrogen bonds (see Fig. 2 and Table 1S), acting as an
acceptor for the N(1)–H(1) of one molecule [N(1)–
H(1)ꢁ ꢁ ꢁO(3D)], and as a donor for the weakly coordinated
O atom of the acetato ligand of a neigbouring molecule
[O(3D)–H(3D)ꢁ ꢁ ꢁO(2)#].
3.3. IR spectroscopy
The main IR bands (see Section 2) were identified on the
basis of data for similar lead compounds [7] and ligands
[8,9]. Additional bands close to 1470, 1100, 1000, 820 and
480 cmꢀ1 are essentially due to ferrocenyl group vibrations,
although in several cases they include contributions from
the thiosemicarbazone group [6].
Fig. 2. ORTEP drawing of [Ph2Pb(OAc)(FEtTSC)] Æ MeOH, showing the
molecular structure, the labelling scheme used, and the intermolecular
hydrogen bonds that connect the molecules of complex via the methanol
molecule.
In comparison with the spectra of the free HTSCs, those
of all the [Ph2PbCl2(HTSC)2] compounds show slight shifts
in the m(N–H) bands (probably due to differences in the
hydrogen bond network), in m(C@S) (which is also less
intense), and in m(C@N). This common shift pattern sug-
gests that in all these adducts the HTSC ligand has the
same coordination mode, which the X-ray data for the
HFMeTSC, HATSC, HAMeTSC and HAEtTSC deriva-
tives show to be monodentate coordination through the
sulphur atom. The HTSC bands have similar positions in
the spectra of the [Ph2Pb(OAc)2(HTSC)2] compounds, sug-
gesting that the HTSC ligand is also S-coordinated in these
adducts. It is likewise plausible that these latter com-
pounds, like the chloride derivatives, have an all-trans octa-
hedral structure, with monodentate OAcꢀ ligands; but we
were unable to test this hypothesis by conclusive identifica-
tion of mas(COO) and msym(COO).
#
2.49 A; N(1)–H(1B)ꢁ ꢁ ꢁCl(1) = 151.8ꢁ; # = x, y ꢀ 1, z] that
˚
links the molecules along the y-axis. A similar interaction
associates the molecules along the z-axis in [Ph2PbCl2-
(HAEtTSC)2] Æ 2(CH3)2CO, in which the occluded acetone
molecules take no part in the hydrogen bonding. By con-
trast, the intermolecular interactions are more complex in
[Ph2PbCl2(HAMeTSC)2] Æ 2MeOH because the MeOH
molecules do participate in the hydrogen bond network.
In [Ph2PbCl2(HFMeTSC)2] there are no intermolecular
interactions (see Table 1S).
The two complexes derived from Ph2Pb(OAc)2 that were
studied by X-ray diffractometry, [Ph2Pb(OAc)(FEtTSC)] Æ
MeOH and [Ph2Pb(OAc)(FMeTSC)] Æ MeOH, have similar
structures (Figs. 2 and 2S). The metal again has coordina-
tion number six (or 5 + 1, see below), bonding to the two
phenyl groups, one N(3),S(1)-coordinated thiosemicarb-
azonato ligand, and one anisobidentate acetate [Pb(1)–
The deprotonation of HTSC makes the 3400–3000 cmꢀ1
region of the spectra of the [Ph2PbX(TSC)] and
[Ph2Pb(TSC)2] compounds much simpler than in the case
of the neutral HTSC adducts. The spectra of [Ph2Pb(FMe-
MeTSC)(OAc)] and [Ph2PbCl(FMeMeTSC)] are practi-
cally identical except for the two strongest and broadest
bands of the acetate, located at 1587 and 1387 cmꢀ1, which
are attributed to mas(COO) and msym(COO). This coinci-
dence supports the proposal that the TSCꢀ ligands of these
˚
O(1) = 2.318(4), Pb(1)–O(2) = 2.911(5) A in [Ph2Pb(OAc)
(FEtTSC)] Æ MeOH]. Although the longer Pb–O distance
exceeds all the acetate–diphenyllead(IV) distances reported
hitherto [18], it is well short of the sum of the van der
˚
Waals radii, 3.5 A [19]. With this weak interaction
included, the metal has coordination number six and pos-
sesses a very distorted octahedral environment with the
phenyl groups apical. The C–Pb–C bond angle,

2242
J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
compounds probably share the S,N-coordination found by
the X-ray study of [Ph2Pb(FMeTSC)(OAc)] and
[Ph2Pb(FEtTSC)(OAc)]. Similarly, in the spectra of all four
[Ph2Pb(TSC)(OAc)] compounds mas(COO) and msym (COO)
lie at positions in keeping with the anisobidentate OAcꢀ
coordination [21] shown by the X-ray study to be present
in [Ph2Pb(FMeTSC)(OAc)] and [Ph2Pb(FEtTSC)(OAc)].
The coordination number of the metal in these complexes,
6 (or 5 + 1), would also be attained in [Ph2PbCl(FMe-
MeTSC)] if these molecules were associated in dimers by
double Clꢀ bridges. Such association would be in keeping
with the strong, broad band observed at 190 cmꢀ1 in the
spectrum of this compound, but is not supported by the
mass spectrum (see below), and the structural diversity of
diphenyllead(IV) complexes of thiosemicarbazones [4c]
therefore means that a monomeric structure cannot be
ruled out.
The [Pb(TSC)2] compounds, too, have spectra in which
the positions of m(C@N) and m(C@S) suggest S,N-coordi-
nation by TSCꢀ. The scant solubility of these compounds
suggests a polymeric structure, which could come about
through the formation of Pb–Sꢁ ꢁ ꢁPb bridges similar to
those found in [Pb(4ML)(SCN)] (4ML = 2-acetylpyri-
dine-4N-methylthiosemicarbazonato) [22].
of the four [Ph2Pb(OAc)(TSC)] complexes also show a
weak peak ascribable to the molecular ion minus any sol-
vating methanol. The other main lead-bearing fragments
are [PhPb(TSC)] and [Pb(TSC)].
3.5. NMR spectroscopy
The most relevant signals in the 1H, 13C and 207Pb NMR
spectra of the complexes in DMSO-d6 solution are listed in
Sections 2.3 and 2.3S. The poor solubility of these com-
pounds precluded measurements in less coordinating
solvents.
In the 1H and 13C NMR spectra of the adducts
[Ph2PbCl2(HTSC)2], the HTSC signals lie at the same posi-
tions as in the spectra of the free ligands [5,10]. Also the
chemical shifts and coupling constants of the signals
belonging to the organometallic moiety are practically
identical to those of free Ph2PbCl2 in DMSO-d6 solution
{d (ppm) 8.13 (Ho), 7.59 (Hm), 7.42 (Hp); 3J(1H–207Pb)
205.9 Hz; for the 13C NMR parameters, see [23]}. The d
207Pb values {e.g. ꢀ506.9 ppm for [Ph2PbCl2(HATSC)]
and ꢀ506.6 ppm for [Ph2PbCl2(HFMeTSC)]} are also
quite similar to the chemical shift of the free acceptor in
the same solvent (ꢀ508.4 ppm in 2.10ꢀ2 M solution). All
this suggests that DMSO-d6 molecules, due to their donor
capacity and their excess in solution, displace the thiosem-
icarbazone ligands, giving the complex [Ph2PbCl2-
(DMSO)2] [24] plus free HTSC.
3.4. Mass spectrometry
Since the FAB spectra of the [Ph2PbCl2(HTSC)2] com-
pounds only show fragments of the HTSC ligand, these
compounds were also studied using ESI; the main metal-
lated fragments are listed in Sections 2.3 and 2.3S. In all
cases the highest-mass ion resulted from loss of a Clꢀ
and a thiosemicarbazone ligand by the initial adduct, and
this peak was always of significant intensity, although the
base peak always corresponded to the [Mꢀ2ClꢀTSC] ion.
The ESI spectrum of [Ph2PbCl(FMeMeTSC)] shows no
multimetallated fragments suggestive of association in
dimers in either methanol or chloroform. The highest-mass
ion is the protonated molecular ion, which appears with
low intensity (2%) at m/z 712. The base peak corresponds
to a fragment with m/z 512 that was identified as the
[PbCl(FMeMeTSC-HNMe2)] ion. The formation of this
fragment, which amounts to a reductive elimination that
has also been observed in the spectra of other diphenyl-
lead(IV) thiosemicarbazonates [4b], reflects the weakness
of Pb–C bonds [1].
The FAB spectra of the complexes of general formula
[Ph2Pb(OAc)2(HTSC)2] all show a [Ph2Pb(TSC)] fragment
indicative of loss of the acetate ligands and one HTSC
ligand. As in the cases of the chloride derivatives, depheny-
lation also occurs, giving the [Pb(TSC)] ion. The absence of
metallated fragments containing the acetate group is
explained by the FAB spectra of the [Ph2Pb(OAc)(TSC)]
complexes, which show Pb–OAc to be their weakest bond.
Ready loss of the OAcꢀ group from acetate/thiosemicar-
bazonate complexes has previously been observed under
ESI [4b]. In spite of this tendency, the FAB spectra of three
The 1H and 13C NMR spectra of [Ph2PbCl(FMe-
MeTSC)] are more complex, especially in the region of
the phenyl and ferrocenyl bands. Several species appear
to be present, but only the signals associated with one of
the major ones, designated arbitrarily as a, were identified
(by means of 1H–13C HMQC and HMBC experiments; see
the Experimental Part). In the 1H NMR spectrum the
absence of a N(2)–H signal confirms the deprotonation
of the thiosemicarbazone ligand. The 13C NMR spectrum
shows C(1) (169.7 ppm) to be more shielded than in the free
HFcMeMeTSC (180.0 ppm [5]), which is in keeping with
evolution to the thiol form, while C(2) is deshielded
(150.2 ppm vs. 144.7 ppm in free HFMeMeTSC). All these
changes are compatible with coordination of the thiosemi-
carbazone via the S and N(3) atoms. In addition, some of
the ferrocenyl carbons are deshielded by as much as 5 ppm
with respect to the free ligand, suggesting that the effects of
coordination are transmitted from the thiosemicarbazone
chain to this group. The 207Pb NMR spectrum shows
two signals, at ꢀ509.0 and ꢀ285.0 ppm; the upfield loca-
tion is practically that of [Ph2PbCl2(DMSO)2] (see above).
In view of this, it seems plausible that in DMSO the com-
plex undergoes the process:
2Ph2PbClðFMeMeTSCÞ þ 2DMSO
! ½Ph2PbCl2ðDMSOÞ2ꢂ þ Ph2PbðFMeMeTSCÞ2ꢂ
This would explain the presence of more than one set of
1
Ph2Pb signals in the H and 13C NMR spectra, and the

J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
2243
signal at ꢀ509.0 ppm in the 207Pb NMR spectrum. Also,
Table 5
Electrochemical data (mV) for selected complexes
the difference between the coordination spheres of [Ph2Pb-
Cl2(DMSO)2] and [Ph2Pb(FMeMeTSC)2], with O and Cl
donors in one and N and S donors in the other, makes it
reasonable for the 207Pb NMR signal of the latter to lie
224 ppm downfield from that of the former, since Pb is
deshielded more by N-binding than by O-binding, and
more still by S-binding [25,26]. The complexity of the ferr-
ocenyl signals suggests that the two FMeMeTSCꢀ ligands
of [Ph2Pb(FMeMeTSC)2] may not be equivalent, or that
the conformations of these ligands are not the same in all
molecules.
E1/2
Ref.
[5]
This work
This work
HFMeTSC
[Ph2PbCl2(HFMeTSC)2]
[Ph2Pb(FMeTSC)(OAc)] Æ MeOH
0.584
0.604
0.626
The complexes derived from Ph2Pb(OAc)2 are poorly
soluble even in DMSO, which in some cases precluded
the recording of the 13C and 207Pb NMR spectra. However,
for [Ph2Pb(OAc)2(HFTSC)2] all the spectra were obtained.
1
Although the H and 13C signals of the HFTSC ligand are
practically at the same positions as in the spectra of free
HFTSC [5], those of the Ph2Pb moiety (see Section 3.2)
differ slightly from those of Ph2Pb(OAc)2 in DMSO-d6
(167.0 ppm, Ci; 134.5 ppm, Co, 132.1 ppm, Cm; 130.0
2
3
ppm, Cp, JC –Pb ¼ 125 Hz, JC –Pb ¼ 206 Hz), and the
o
m
Fig. 3. Cyclic voltammogram of [Ph2Pb(FMeTSC)(OAc)] Æ MeOH.
207Pb nucleus is more deshielded in the complex
(ꢀ659.6 ppm) than in Ph2Pb(OAc)2 (ꢀ858.0 ppm in
2.10ꢀ2 M solution; note that, as Fig. 3S shows, this param-
eter is practically independent of concentration, which
rules out any association in solution). This deshielding,
which is coherent with partial permanence of the S atom
in the coordination sphere of the metal [26], is even more
pronounced in [Ph2Pb(FMeTSC)(OAc)] Æ MeOH (d 207Pb
= ꢀ532.0 ppm) and [Ph2Pb(FMeMeTSC)(OAc)] (d 207Pb
= ꢀ530.0 ppm), in which the deprotonated ligand proba-
bly remains N(3),S-coordinated in solution.
oxidation more difficult. This interpretation, which
assumes ‘‘communication’’ between the thiosemicarbazone
and ferrocenyl moieties is supported by a recent theoretical
study [6], and is in keeping with the positive E1/2 shift being
larger for [Ph2Pb(FMeTSC)(OAc)] Æ MeOH than for
[Ph2PbCl2(HFMeTSC)2], since more electron charge
should be transferred to the lead centre from N,S-bound
FMeTSCꢀ anion than from neutral S-bound HFMeTSC
ligand. It thus seems that the redox ‘‘tail’’ of this type of
thiosemicarbazone is sensitive not only to coordination
by metals but also to the coordination mode.
The solubility of the [Pb(TSC)2] complexes in DMSO-
1
d6, though very poor, did allow the recording of H and
13C NMR spectra in all cases, though not always with a
good signal to noise ratio. In all the cases, both spectra
confirm the presence of deprotonated N,S-coordinated
ligands (see Sections 3.2 and 3.2S).
Acknowledgements
This work was supported by the UE Directorate Gen-
eral for Regional Policies, the Spanish Ministry of Science
and Technology and the German Academic Exchange Ser-
vice through Hispano-German Integrated Action HA2001-
0071, project BQU2002-04524-C02-01 and project
CTQ2006-11805/BQU, and by the Xunta de Galicia,
Spain, under projects PGIDIT03PXIC20306PN and
XUGA20308B97.
3.6. Cyclic voltammetry
In spite of the poor solubility of these complexes, it was
possible to investigate the electrochemical behaviour of
both a 1:2 and a 1:1 Ph2Pb complexes of HFMeTSC in
CH2Cl2 solution (see Table 5). The cyclic voltammograms
were recorded in the potential range in which ferrocene
undergoes redox processes. Like that of the free ligand
[5], they reflect quasi-reversible redox processes {Fig. 3
shows that of [Ph2Pb(FMeTSC)(OAc)] Æ MeOH}. In each
case, only one redox specie seems to be present, and like
ferrocenyl thiosemicarbazonates of gold(III) [5], it has an
E1/2 value that is more positive than that of free
HFMeTSC. This E1/2 shift may be ascribed [27] to the
inductive effect of the coordinated lead: coordination
reduces the electron charge on the TSC chain and, via
the chain, that of the ferrocenyl Fe(II) centre, making its
Appendix A. Supplementary material
1CCDC 631406,631407, 631408, 631409, 631410 and
631411 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary

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J.S. Casas et al. / Journal of Organometallic Chemistry 692 (2007) 2234–2244
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