Diphenylthallium(III) thiosemicarbazonates: Flexibility of coordination in the solid state and polymorphism in chloroform solution

Article abstract of DOI:10.1016/S0020-1693(02)01433-0

The reactions of diphenylthallium(III) hydroxide in water-ethanol at room temperature with thiosemicarbazones HL=R=N(3)-N(2)H-C(1)(S)-N(1)H₂ (RO=cyclopentanone, benzaldehyde, 2-hydroxybenzaldehyde, 4-methoxybenzaldehyde, acetophenone, furan-2-carbaldehyde, pyridine-2-formaldehyde and pyridine-2-acetaldehyde) afforded novel diphenylthallium(III) thiosemicarbazonates of stoichiometry [TlPh₂(L)] (compounds 1-8, respectively) that were characterised with the help of analytical data, physical properties, IR spectrometry, multinuclear (¹H, ¹³C and ²⁰⁵Tl) NMR spectroscopy and X-ray studies of 1, 7 and 8. In crystals of 1 (and probably also in those of 2, 4, 5 and 6), Tl(III) is bound to two phenyl carbons and to the N(3) and S atoms of the monodeprotonated thiosemicarbazone in a distorted trigonal bipyramidal coordination polyhedron with one vacant site in the equatorial plane. In 3 the metal atom is S,N(3),O-coordinated. In 7 and 8 there are three independent molecules: all three have distorted trigonal bipyramidal coordination with Tl coordinated to two carbon atoms and to the N(Py), N(3) and S atoms of the deprotonated thiosemicarbazones, but they differ significantly in their bonding parameters. The ²⁰⁵Tl NMR spectra suggest that for 1-6 more than one coordination mode is present in solution in chloroform, whereas for 7 and 8 there is only one species. Low temperature proton NMR studies of 7 and 8 showed that the energy barrier to rotation of the amino groups about the C¹-N¹ bond correlated with the bonding parameters of the thioamide group in the solid state; in both cases the barrier is somewhat higher than in thiosemicarbazonates of PhHg(II).

Full text of DOI:10.1016/S0020-1693(02)01433-0

Inorganica Chimica Acta 347 (2003) 23ꢀ32
/
www.elsevier.com/locate/ica
Diphenylthallium(III) thiosemicarbazonates:
flexibility of coordination in the solid state and polymorphism
in chloroform solution
Tarlok S. Lobana 1,*, Jose´ S. Casas *, Alfonso Castineiras, Mar´ıa S. Garc´ıa-Tasende,
˜
Agust´ın Sa´nchez, Jose´ Sordo
Departamento de Qu´ımica Inorga´nica, Facultade de Farmacia, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain
Received 31 October 2001; accepted 8 January 2002
Dedicated in honor of Professor R. Uso´n
Abstract
The reactions of diphenylthallium(III) hydroxide in waterꢀ
N(3)ꢀN(2)HꢀC(1)(S)ꢀN(1)H2 (ROꢁcyclopentanone, benzaldehyde, 2-hydroxybenzaldehyde, 4-methoxybenzaldehyde, acetophe-
none, furan-2-carbaldehyde, pyridine-2-formaldehyde and pyridine-2-acetaldehyde) afforded novel diphenylthallium(III) thiosemi-
8, respectively) that were characterised with the help of analytical data,
/
ethanol at room temperature with thiosemicarbazones HLꢁ
/
Rꢁ
/
/
/
/
/
carbazonates of stoichiometry [TlPh2(L)] (compounds 1ꢀ
/
physical properties, IR spectrometry, multinuclear (1H, 13C and 205Tl) NMR spectroscopy and X-ray studies of 1, 7 and 8. In
crystals of 1 (and probably also in those of 2, 4, 5 and 6), Tl(III) is bound to two phenyl carbons and to the N(3) and S atoms of the
monodeprotonated thiosemicarbazone in a distorted trigonal bipyramidal coordination polyhedron with one vacant site in the
equatorial plane. In 3 the metal atom is S,N(3),O-coordinated. In 7 and 8 there are three independent molecules: all three have
distorted trigonal bipyramidal coordination with Tl coordinated to two carbon atoms and to the N(Py), N(3) and S atoms of the
deprotonated thiosemicarbazones, but they differ significantly in their bonding parameters. The 205Tl NMR spectra suggest that for
1ꢀ
/
6 more than one coordination mode is present in solution in chloroform, whereas for 7 and 8 there is only one species. Low
temperature proton NMR studies of 7 and 8 showed that the energy barrier to rotation of the amino groups about the C1ꢀ
/
N1 bond
correlated with the bonding parameters of the thioamide group in the solid state; in both cases the barrier is somewhat higher than in
thiosemicarbazonates of PhHg(II).
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Diphenylthallium(III) complexes; Thiosemicarbazone complexes
1. Introduction
coordination modes and structures [1ꢀ4]. Because of
/
their biological importance, complexes of thiosemicar-
bazones with transition metals have been more inten-
sively investigated than their complexes with main group
There are several reasons for interest in the coordina-
tion chemistry of thiosemicarbazones [1ꢀ5]. In particu-
/
lar, metal derivatives of thiosemicarbazones often
display better pharmacological properties than the
elements [1ꢀ
zonates of organometallic cations with heavy metals M
has increased in relation with efforts to activate Mꢀ
/
5]. However, interest in thiosemicarba-
/C
thiosemicarbazones themselves; and as a class, metalꢀ
/
bonds by coordination so as to convert toxic organo-
metallic substrates into less toxic inorganic compounds
thiosemicarbazone complexes exhibit a great variety of
[6ꢀ
We recently reported a series of thiosemicarbazonates
of organomercury(II) cations RHgꢂ (Rꢁ
C6H5- or 2-
C5H4NC6H4ꢀ) [12,13]. Here we describe analogous
thiosemicarbazonates of diphenylthallium(III) cation,
Ph2Tlꢂ (Scheme 1 shows the parent thiosemicarba-
/
11].
* Corresponding authors. Fax: ꢂ34-981-594-912.
/
E-mail addresses: tarlokslobana@yahoo.co.in (T.S. Lobana),
qiscasas@usc.es (J.S. Casas).
/
/
1
Visiting Professor from the Department of Chemistry, Guru
Nanak Dev University, Amritsar, India, from February 1996 to April
1997.
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(02)01433-0

24
T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ
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Scheme 1.
zones). In most of the few organothallium(III) thiose-
micarbazonates reported previously the cation is
Me2Tlꢂ [5]. We found the new diphenylthallium(III)
thiosemicarbazonates to have interesting bonding prop-
erties, both in the solid state and in CDCl3 solution.
phenylboronic acid (6.0 g) in water (20 ml); this mixture
was refluxed for 5 h and allowed to cool, and the
TlPh2Br formed was filtered out, washed with water and
dried in vacuo.
Caution! thallium is a highly toxic cumulative poison
and thallium compounds should be handled carefully.
The ligands were prepared following a published [16]
general procedure by reacting the thiosemicarbazide
with the corresponding aldehyde or ketone in ethanol/
water. The properties of most of the ligands used, and
other relevant details, have been described elsewhere
[12].
2. Experimental
2.1. General materials
Cyclopentanone, benzaldehyde, salicylaldehyde, p-
methoxybenzaldehyde, acetophenone, 2-furanaldehyde,
2-pyridineformaldehyde, 2-pyridineacetaldehyde, thio-
semicarbazide, thallium(I) bromide and phenylboronic
acid were of reagent grade and were used without
further purification.
2.3. Synthesis of the complexes
2.3.1. [TlPh2(cptsc)] (1)
2.2. Synthesis of TlPh2X (XꢁOH, Br) and ligands
/
A solution of TlPh2(OH) (0.260 g, 0.73 mmol) in
water (40 ml) was added slowly with stirring to a
solution of Hcptsc (0.115 g, 0.73 mmol) in ethanol (25
ml). The mixture was stirred for 36 h at r.t. (ca. 25 8C)
and the volume was reduced when a white solid started
Diphenylthallium(III) hydroxide was prepared by a
method used previously [14] for dimethylthallium(III)
hydroxide, by stirring diphenylthallium(III) bromide for
24 h at room temperature (r.t.) with a freshly prepared
aqueous suspension of Ag2O [from AgNO3 (0.8 g) and
NaOH (1.5 g) in H2O], followed by filtration. TlPh2Br
was prepared as follows [15]: bromine (1.5 ml) was
added with stirring to a suspension of solid thallium(I)
bromide (6.25 g) in water (30 ml) until formation of a
clear solution that, following removal of excess bromine
under vacuum, was slowly added to a suspension of
forming. The solid was recrystallised from chloroformꢀ
/
ethanol and dried in vacuo. Yield, 45%; m.p., 150ꢀ
/
155 8C (decomp.). Anal. Found: C, 41.1; H, 3.99; N,
8.97. Calc. for C18H20TlN3S: C, 41.9; H, 3.88; N, 8.16%.
IR spectrum (cmꢃ1): 3454s, 3335s, n(NH2); 1591s,
n(CN); 790w, n(CS); 242, n(TlC). Crystals suitable for
the X-ray study were grown from ethanol.

T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ
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25
2.3.2. [TlPh2(btsc)] (2)
2.3.6. [TlPh2(ftsc)] (6)
A solution of TlPh2(OH) (0.430 g, 1.14 mmol) in
water (40 ml) was added slowly with stirring to a
solution of Hbtsc (0.205 g, 1.14 mmol) in ethanol (25
ml). The mixture was stirred for 48 h at r.t. (ca. 25 8C)
and the light green solid formed was filtered out, washed
A solution of TlPh2(OH) (0.260 g, 0.73 mmol) in
water (40 ml) was added slowly with stirring to a
solution of Hftsc (0.116 g, 0.73 mmol) in ethanol (25
ml). The mixture was stirred for 48 h at r.t. (ca. 25 8C)
and the light steel grey solid formed was filtered, washed
with ethanol, recrystallised from chloroformꢀ
and dried in vacuo. Yield, 40%; m.p., 140ꢀ
/
ethanol
145 8C
with ethanol, recrystallised from chloroformꢀ
and dried in vacuo. Yield, 43%; m.p., 145ꢀ
/
ethanol
155 8C
/
/
(decomp.). Anal. Found: C, 44.1; H, 3.30; N, 7.82.
Calc. for C20H18TlN3S: C, 44.7; H, 3.35; N, 7.82%. IR
spectrum (cmꢃ1): 3491m, 3372m, n(NH2); 1568vs,
n(CN); 805m, n(CS); 250m, n(TlC).
(decomp.). Anal. Found: C, 40.4; H, 2.88; N, 7.85.
Calc. for C18H16TlN3SO: C, 41.0; H, 3.04; N, 7.97%. IR
spectrum (cmꢃ1): 3479m, 3438m, 3350m, n(NH2);
1588s, n(CN); 809m, n(CS); 247m, n(TlC).
2.3.7. [TlPh2(pytsc)] (7)
2.3.3. [TlPh2(Hstsc)] (3)
A solution of TlPh2(OH) (0.345 g, 0.92 mmol) in
water (40 ml) was added slowly with stirring to a
solution of Hpytsc (0.167 g, 0.92 mmol) in ethanol (25
ml). The mixture was stirred for 30 h at r.t. (ca. 25 8C),
and the light greenish-yellow solid formed was filtered
out, washed with ethanol, recrystallised from ethanol
A solution of TlPh2(OH) (0.430 g, 1.14 mmol) in
water (40 ml) was added slowly with stirring to a
solution of H2stsc (0.225 g, 1.14 mmol) in ethanol (25
ml). The mixture was stirred for 40 h at r.t. (ca. 25 8C),
and the light-green solid formed was filtered out,
washed with ethanol, recrystallised from chloroformꢀ
/
and dried in vacuo. Yield, 46%; m.p., 170ꢀ180 8C
/
ethanol and dried in vacuo. Yield, 40%; m.p., 118ꢀ
/
(decomp.). Anal. Found: C, 42.2; H, 3.22; N, 10.45.
Calc. for C19H17TlN4S: C, 42.4; H, 3.16; N, 10.41%. IR
spectrum (cmꢃ1): 3470m, 3435m, 3310sh, 3262m,
130 8C (decomp.). Anal. Found: C, 42.7; H, 2.92; N,
7.64. Calc. for C20H18TlN3SO: C, 43.4; H, 3.25; N,
7.59%. IR spectrum (cmꢃ1): 3443m,br, 3330m,br,
n(NH2); 1594s, n(CN); 1303s, n(CO); 816w, n(CS);
246m, n(TlC).
n(NH2); 1588s, n(CN); 790m, n(CS); 619m, d(CH)o.p.
427m, d(CH)i.p.; 246m, n(TlC). Crystals suitable for the
X-ray study were grown from chloroformꢀethanol.
;
/
2.3.8. [TlPh2(acpytsc)] (8)
2.3.4. [TlPh2(mbtsc)] (4)
A solution of TlPh2(OH) (0.260 g, 0.73 mmol) in
water (40 ml) was slowly added with stirring to a
solution of Hacpytsc (0.135 g, 0.73 mmol) in ethanol
(25 ml). The mixture was stirred for 24 h at r.t. (ca.
25 8C), its volume was reduced under vacuum, and the
A solution of TlPh2(OH) (0.260 g, 0.73 mmol) in
water (40 ml) was slowly added with stirring to a
solution of Hmbtsc (0.145 g, 0.73 mmol) in ethanol
(25 ml). The mixture was stirred for 40 h at r.t. (ca.
25 8C), and the white solid formed was filtered out,
light greenishꢀ
washed with ethanol, recrystallised from ethanol and
dried in vacuo. Yield, 50%; m.p., 150ꢀ155 8C (de-
/yellow solid formed was filtered out,
washed with ethanol, recrystallised from chloroformꢀ
ethanol and dried in vacuo. Yield, 72%; m.p., 125ꢀ
/
/
/
140 8C (decomp.). Anal. Found: C, 43.4; H, 3.46; N,
7.25. Calc. for C21H20TlN3SO: C, 44.4; H, 3.53; N,
7.40%. IR spectrum (cmꢃ1): 3498m, 3373m, n(NH2);
1571s, n(CN); 1247s, n(CO); 809m, n(CS); 252m,
n(TlC).
comp.). Anal. Found: C, 42.9; H, 3.13; N, 9.94. Calc.
for C20H19TlN4S: C, 43.5, H, 3.44, N, 10.14%. IR
spectrum (cmꢃ1): 3450m, 3430m, 3312m,br, n(NH2);
1586s, n(CN); 798m, n(CS); 628m, d(CH)o.p.; 424m,
d(CH)i.p.; 249m, n(TlC). Crystals suitable for the X-ray
study were grown from chloroformꢀ
/ethanol.
2.3.5. [TlPh2(atsc)] (5)
2.4. Physical measurements
A solution of TlPh2(OH) (0.260 g, 0.73 mmol) in
water (40 ml) was added slowly with stirring to a
solution of Hatsc (0.135 g, 0.73 mmol) in ethanol (25
ml). The mixture was stirred for 24 h at r.t. (ca. 25 8C),
and the light steel grey solid formed was filtered out,
Elemental analyses for C, H and N were performed
with a CarloꢀErba 1108 microanalyser. Melting points
were determined with a Gallenkamp electrically heated
/
apparatus. Infrared spectra were recorded with samples
400cmꢃ1) or in Nujol mulls
washed with ethanol, recrystallised from chloroformꢀ
/
in KBr pellets (4000ꢀ
between polyethylene sheets (500ꢀ
/
ethanol and dried in vacuo. Yield, 52%; m.p., 130ꢀ
/
/
100 cmꢃ1) on a
140 8C (decomp.). Anal. Found: C, 45.7; H, 3.56; N,
7.61. Calc. for C21H20TlN3S: C, 45.7; H, 3.63; N, 7.62%.
IR spectrum (cmꢃ1): 3485s, 3353s, n(NH2); 1566vs,
n(CN); 818m, n(CS); 244, n(TlC).
Bruker IFS 66 V spectrometer. NMR spectra were
recorded with samples in CDCl3 using a Bruker AMX
1
300 spectrometer at 300.14 and 75.48 MHz for H and
13C spectra, respectively (both with TMS as internal

26
T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ32
/
Table 1
Summary of crystal data for compounds 1, 7 and 8
[TlPh2(cptsc)] (1)
18H20TlN3S
514.80
[TlPh2(pytsc)] (7)
[TlPh2(acpytsc)] (8)
Chemical formula
Formula weight
Temperature (K)
Crystal system
C
C19H17TlN4S
537.80
293(2)
C20H19TlN4S
551.82
293(2)
293(2)
monoclinic
P21/c (no. 14)
triclinic
¯
P1 (no. 2)
triclinic
¯
P1 (no. 2)
Space group
Unit cell dimensions
˚
a (A)
9.5659(10)
12.139(2)
16.388(2)
13.489(5)
15.178(6)
15.682(3)
71.038(19)
69.435(18)
82.25(4)
2842.3(16)
6
12.357(2)
12.787(2)
19.600(2)
81.022(10)
86.585(10)
77.345(10)
2983.7(7)
6
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
106.318(11)
3
˚
U (A )
1826.3(4)
4
8.960
Z
m(Mo Ka) (mmꢃ1
No. of reflections collected
No. of unique reflections/Rint
No. of observed reflections
)
8.642
14860
8.235
12671
3843
3710/0.0286
3710
0.0305/0.0655
14351/0.0821
6087
0.0472/0.0746
12088/0.0333
7965
0.0341/0.0700
Final R1 [I ꢀ
/
2s(I)]/wR2
reference) and at 173.76 MHz for 205Tl spectra (using an
aqueous solution of TlClO4 extrapolated to infinite
dilution as external reference). All physical measure-
ments were carried out in the RIAIDT services of the
University of Santiago de Compostela.
Scheme 1 afforded diphenylthallium(III) thiosemicarba-
zonates [TlPh2(L)]. The spectral data suggest that the
most acidic group of HL, ꢀ
/
N(2)H, is deprotonated in all
these complexes except in 3.
The new compounds are white, light steel grey, pale-
green or light greenish yellow (cf. experimental), and
rather than melting decompose to black material at
2.5. Structure determinations
temperatures in the range 118ꢀ180 8C. They are stable
/
to light and moisture in the solid state, but decompose in
solution if left for 3 days or more. All are soluble in
DMSO; 2, 4, 5, 6 and 8 are completely soluble in
dichloromethane and chloroform and slightly soluble in
ethanol and methanol; 1 and 3 are partially soluble in
these four solvents; and 7 is soluble in all the solvents.
Suitable crystals of 1, 7 and 8 were mounted on an
Enrafꢀ
/
Nonius MACH3 automatic diffractometer [17a].
2u scan
Data were collected at 293 K by the v ꢀ
technique using Mo Ka radiation (lꢁ
/
˚
0.71073 A), and
/
were corrected for Lorentz and polarisation effects
[17b]. Empirical [17c] absorption corrections were
applied for 1 and 8 and a semi-empirical correction
(psi scan) [17d] for 7. Structures 1 and 8 were solved by
the heavy atom method [17e] and 7 by direct methods
[17f]. All three were refined by full-matrix least-squares
methods based on F2. All non-hydrogen atoms were
refined anisotropically [17g]. Hydrogen atoms were
included in the model at geometrically calculated posi-
tions. Atomic scattering factors were taken from Inter-
national Tables for Crystallography [17h]. Molecular
graphics were generated with ORTEP [17i].
3.2. Crystal and molecular structures
The crystal data and most significant bond lengths
and angles of 1, 7 and 8 are listed in Tables 1 and 2,
respectively, and [TlPh2(cptsc)] (1) and [TlPh2(pytsc)] (7,
molecule 1) are shown together with their atom number-
ing schemes in Figs. 1 and 2, respectively. In all three
compounds the ligand adopts Z-configuration with
respect to the N(2)ꢀC(1) bond, chelating the Tl atom
/
Crystal data, experimental details and refinement
results are listed in Table 1.
via N(3) and S (in 1) or N(4), N(3) and S (in 7 and 8).
Whereas 1 has only one form of the molecule in its
crystal lattice, the crystals of 7 and 8 both have three
independent molecules differing significantly in their
bonding parameters. Packing in the lattice appears to
stabilize the independent molecules, because in solution
only one species was detected by NMR (vide infra).
In compound 1, Tl(III) is bound to one carbon atom
of each of the phenyl groups [C(7) and C(13)] and to the
donor atoms [(N(3) and S)] of the deprotonated
3. Results and discussion
3.1. General comments
The reactions of diphenylthallium(III) hydroxide at
room temperature with the thiosemicarbazones HL of

T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ
/32
27
˚
S bond length, 1.749(7) A, is shorter than a
Table 2
The Cꢀ
single bond (dCꢀS
double bond (dCꢀS
double bond character. Interestingly, the length of this
/
˚
˚
Some significant bond lengths (A) and bond angles (8) in compounds 1,
7 and 8
ꢁ
/
1.81 A) but longer than a Cꢀ
/
S
˚
ꢁ1.62 A) [23], suggesting partial
/
a
Parameter
Compound Molecule 1 Molecule 2 Molecule 3
˚
bond in [TlMe2(cptsc)], 1.78(2) A [18,23], is close to that
Bond lengths
of a single bond even though the TlꢀS bond is also
/
Tlꢀ
/
N(3)
S
1
7
8
1
7
8
7
8
1
2.452(5)
2.547(7)
2.500(6)
2.6156(18)
2.779(3)
2.711(2)
2.657(7)
2.569(6)
2.146(6)
2.148(6)
2.154(9)
2.141(9)
2.175(7)
2.146(7)
1.749(7)
1.724(9)
1.727(9)
1.344(8)
1.317(10)
1.353(9)
1.302(8)
1.321(10)
1.295(9)
1.391(7)
1.383(9)
1.382(8)
1.278(7)
1.258(10)
1.281(8)
slightly longer than in 1; this is probably due to the S
atom of [TlMe2(cptsc)] being involved in a weak
2.472(7)
2.558(5)
2.537(7)
2.485(5)
additional TlÁ Á ÁS interaction that is not present in 1.
Tlꢀ
/
˚
N(3) bond length, 1.278(7) A, is that of a
2.691(3)
2.7339(19)
2.708(8)
2.613(5)
2.764(3)
2.743(2)
2.641(8)
2.644(6)
The C(2)ꢀ
/
˚
double bond (dCꢁN
tion of ꢀN(2)H lends C(1)ꢀ
shortening it to 1.302(8) A {close to the length of a Cꢀ
double bond and somewhat shorter than the 1.310(2) A
of [TlMe2(cptsc)]}. The thiosemicarbazone bite angle
ꢁ
/
1.28 A) [23], and the deprotona-
Tlꢀ
/
N(4)
C
/
/N(2) double bond character,
˚
/N
Tlꢀ
/
˚
7
8
2.156(9)
2.139(10)
2.150(7)
2.151(7)
2.161(9)
2.140(9)
2.146(8)
2.122(8)
N(3)ꢀ
/
TlꢀS, 72.90(12)8, is close to that of [TlMe2(cptsc)],
/
70.9(3)8 [18]. These and other bond angles allow the
coordination polyhedron to be described as a distorted
trigonal bipyramid with one vacant equatorial position.
The crystal and molecular structures of compounds 7
and 8 are similar. Both compounds crystallize in the
same space group and both have three independent
molecules in the asymmetric unit. The closest precedent
for such variety is [TlMe2(pytsc)], in which there are two
independent molecules in each asymmetric unit [24]. For
clarity, Fig. 2 shows only molecule 1 of compound 7;
compound 8 is very similar and is not shown. Table 2
lists the most significant bond lengths and angles of the
Sꢀ/
C(1)
1
7
8
1
7
8
1
7
8
1
7
8
1
7
8
1.711(9)
1.729(7)
1.724(11)
1.742(7)
C(1)ꢀ/N(1)
1.339(10)
1.353(8)
1.357(11)
1.350(9)
C(1)ꢀ/N(2)
1.331(10)
1.310(8)
1.299(11)
1.290(9)
N(2)ꢀN(3)
/
1.392(9)
1.392(7)
1.361(9)
1.368(7)
C(2)ꢀN(3)
/
three molecules of each compound. In general, the Tlꢀ
N(3) bonds in 7 and 8 are shorter than in [TlMe2(pytsc)],
as are TlꢀS and TlꢀN(4); however, the TlꢀC bonds are
clearly longer in the diphenylthallium derivatives. The
bite angle N(3)ꢀTlꢀS is wider in 7 and 8 than in
[TlMe2(pytsc)], but the CꢀTlꢀC bond angle is narrower.
As expected, the pentacoordinated Tl of 7 and 8 has
longer TlꢀN(3) and TlꢀS bonds than the tetra-coordi-
nated Tl of 1.
/
1.288(10)
1.299(8)
1.266(11)
1.304(8)
/
/
/
Bond angles
CꢀTlꢀ
/
/C
1
7
8
1
7
8
146.6(2)
160.6(3)
151.1(3)
72.90(12)
68.39(18)
70.88(13)
154.7(4)
157.7(3)
158.2(4)
152.8(3)
/
/
/
/
N(3)ꢀ
/
TlꢀS
/
71.60(18)
69.51(12)
68.97(19)
71.29(14)
/
/
In keeping with the general tendency of diorganothal-
lium(III) compounds to acquire high coordination
number by binding to donor atoms of a second molecule
a
[18,19], the Tl of molecule 1 of 7 interacts weakly with
S(1)i (iꢁ
sum of the van der Waals radii 3.76 A [23]), giving rise
/
1ꢃ
/
x, 2ꢃ
/
y, ꢃ
/
z; Tl(1)Á Á ÁS(1)iꢁ
/3.425(3) A,
˚
˚
cyclopentanone thiosemicarbazone (cptscꢃ). The Tlꢀ
/
to a very weakly bound dimer. Molecule 3 of compound
8
˚
N(3) bond length, 2.452(5) A, is shorter than in
has
a
similar but even weaker interaction
˚
˚
[Tl(3)Á Á ÁS(3)iꢁ
/
3.614(2) A, iꢁ
/
ꢃ
/
x, 2ꢃ
/
y, 1ꢃz]. These
/
[TlMe2(cptsc)], in which Tlꢀ
so is the Tlꢀ
2.6156(18); [TlMe2(cptsc)], 2.627(5) A}. This shortening
of the TlꢀN(3) and TlꢀS bonds is accompanied by a
lengthening of the TlꢀC distances, 2.146(6) and 2.148(6)
/
N(3)ꢁ/2.55(1) A [18], and
/S distance though less markedly {1,
two bonds are shorter than the analogous bond of
˚
molecule 1 of [TlMe2(pytsc)] [3.671(2) A], but longer
˚
/
/
˚
than that of molecule 2 [3.207(3) A] [24].
In all three compounds (1, 7 and 8) a hydrogen bond
network stabilizes the lattice (see Table 3). In 1, a weak
/
˚
˚
A in 1 as against 2.07(3) and 2.13(3) A in [TlMe2(cptsc)].
The TlꢀN and TlꢀS bonds in 1 are also shorter than
those of [TlMe2(mbtsc)] [19], in which mbtscꢃ is bound
to Tl via N(2) and S instead of N(3) and S [with Tlꢀ
/
/
intermolecular hydrogen bond between N(1)ꢀH(1B)
/
and the S atom of a neighboring molecule links the
molecules in dimers. In 7 there are three hydrogen
bonds, two binding molecule 1 to molecules 2 and 3, and
one between two molecules of type 2; no S atoms are
/
˚
˚
N(2)ꢁ
/
2.56(1) A and Tlꢀ
/
Sꢁ
/
2.991(4) A], and those of
22].
other diorganothallium(III) compounds [10,14,20ꢀ
/

28
T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ32
/
Fig. 1. An ORTEP drawing of [TlPh2(cptsc)] (1), showing the molecular structure and the labelling scheme.
Fig. 2. An ORTEP drawing of molecule 1 of [TlPh2(pytsc)] (7), showing the molecular structure and the labelling scheme.
involved in any of the three. There are also three
hydrogen bonds in 8, two of them binding molecule 1
to molecule 3 via S atoms, and one between two
molecules of type 2.
thiosemicarbazone ligand (1, 2 and 5), and those in
which there is (3, 4, 6, 7 and 8).
Analysis of the shifts that the free thiosemicarbazone
IR bands undergo upon deprotonation and coordina-
tion suggests that in the first class 2 and 5 have the same
N(3),S-coordination as was found in the X-ray study of
1. As in the spectra of other complexes of deprotonated
thiosemicarbazones [12], the n[N(2)H] band located
around 3100 cmꢃ1 in that of the free ligand disappears
(although a weak residual band in the spectrum of 1
suggests that in Hcptsc this is a multicomponent band).
3.3. IR spectra
The main IR bands of the complexes are listed in the
Experimental part. For discussion of these spectra the
complexes can be grouped in two classes: those in which
there is no donor atom in the R substituent of the

T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ
/32
29
The n(NH2) bands are slightly shifted to higher wave-
numbers, indicating that this group is not coordinated
to Tl. The coordination of N(3) does not shift n(CN)
significantly, but coordination of S shifts the n(CS) band
located between 830 and 820 cmꢃ1 to lower wavenum-
bers, and bands between 1100 and 1000 cmꢃ1 are
weakened.
For the compounds with a donor atom in the R
substituent of the ligand, spectral changes similar to
those described above likewise show coordination via
N(3) and S. In the spectra of 7 and 8, coordination by
the pyridine N is reflected by the shift to higher
wavenumbers of the in-plane and out-of-plane CH
(only the most intense signal is listed in the tables).
Deprotonation of N(2)H is shown by all of the com-
plexes except 3 having any signal in the 8ꢀ
region [compound 3 has a signal at 10.76 ppm, a
position intermediate between the ꢀOH (9.87 ppm)
and ꢀN(2)H (11.38) signals of free H2stsc in DMSO-
d6] [13]. As usual, the NH2 protons appear as single
peaks (compounds 1, 3 and 5ꢀ8) or vanish (compounds
/12 ppm [13]
/
/
/
2 and 4), whereas in the room temperature spectra of the
free thiosemicarbazones they appear as two broad peaks
in the region 6ꢀ
signals of Ph2Tlꢂ are separated by the 205Tl nucleus
(Iꢁ 450
1/2); the o-Ph signals have 3JTlꢀH values of 400ꢀ
/9 ppm [12]. The o-, m- and p-Ph proton
/
/
vibrations. In the spectra of 4 and 6 n(Cꢀ
/
O) and the
Hz (Table 4), but due to the overlapping of signals it was
only possible to calculate 4JTlꢀH and 5JTlꢀH for some of
the compounds.
furan ring vibrations, respectively, are practically in the
same positions as in those of the free ligands, which
argues against O-coordination.
The 13C NMR data are listed in Table 5. The
interaction of diphenylthallium(III) with the thiosemi-
carbazones mainly affects C(1) and C(2) (see Refs.
[12,26] for the data of the free ligands); Ph2Tlꢂ carbons
remain unaffected, as do ligand ring carbons (except in 7
and 8; vide infra). The accumulation of negative charge
on the donor S atom, and the downfield shift of the C(2)
signal relative to the free ligands, suggest that N(3),S-
In the spectrum of 3, broad bands at 3443 and 3330
cmꢃ1 are attributed to n(NH2). A medium intensity
band at 3146 cmꢃ1 might in principle be due to either
n(OH) or n(NH) depending on the location of the H
atom remaining after monodeprotonation, but attribu-
tion to n(NH) seems more plausible in view of the O-
coordination suggested by the shift of the n(CO) bands
(at 1283s and 1267s in the free ligand) to higher
wavenumbers close to their positions in the spectra of
complexes in which this ligand is S,N,O-coordinated
and bideprotonated [25]. This probable S,N(3),O-coor-
dination of 3 contrasts with the essentially monodentate
S-donor behaviour found [13] in the [2(-(pyridin)-2?-
yl)phenyl]mercury(II) complex of this ligand, in which,
as in 3, it is monodeprotonated.
coordination holds in 1ꢀ
affects the pyridyl signals as well as those of C(1) and
C(2). C(3) and C(7) move upfield and C(4ꢀ6) move
/6. In 7 and 8 coordination
/
downfield relative to the free ligand in DMSO-d6 [26].
Further, the 1JTlꢀC coupling constants of 7 and 8 are the
largest, followed by that of 6. Coordination of the
pyridyl group to Ph2Tlꢂ transfers additional charge to
Tl, which in turn seems to pass it on to the phenyl
3
Tl coupling. The JCꢀTl
Finally, whether the metal is tetra-, penta- or hex-
acoordinated does not significantly affect the position of
groups, increasing the 13Cꢀ205
values, involving meta-carbons, are also highest for 7
and 8.
/
n(Tlꢀ
/
C), which in all cases appears as a band close to
.
250 cmꢃ1
3.4.2. 205Tl NMR spectra
Table 6 lists 205Tl NMR data for 1ꢀ
8. All signals are
/
3.4. Solution-phase studies
rather narrow singlets. Complexes 7 and 8, which
contain pyridyl groups, showed only one signal each,
in contrast to the two, three or even four signals shown
3.4.1. 1H and 13C NMR spectra
1
The chief H NMR data for the complexes in CDCl3
are listed in Table 4. In general, the spectra show more
than one signal associated with each resonant nucleus
by 1ꢀ
/
6. Most of the peaks occur in the regions 3728ꢀ
/
3766 ppm (peak I), 3612ꢀ
/
3662 ppm (peak II) and 3461ꢀ
/
Table 3
˚
Intermolecular hydrogen bonds in compounds 1, 7 and 8 (A, 8)
Compound
Dꢀ
/
HÁ Á ÁA
d(Dꢀ/H)
d(HÁ Á ÁA)
d(DÁ Á ÁA)
ꢁ(DHA)
/
1
7
N(1)ꢀ
/
H(1)BÁ Á ÁSi
0.86
2.70
3.512(6)
3.048
2.973
3.098
3.575
3.085
3.456
157.5
N(11)ꢀ
N(21)ꢀ
N(21)ꢀ
N(11)ꢀ
N(21)ꢀ
N(31)ꢀ
/
H(11)B...N(32)ii
H(21)AÁ Á ÁN(22)iii
H(21)B...N(12)
H(11)B...S(3)iv
H(21)AÁ Á ÁN(22)v
H(31)B...S(1)vi
0.860
0.860
0.860
0.860
0.860
0.860
2.207
2.135
2.252
2.734
2.322
2.620
165.79
164.79
167.95
166.48
147.97
164.37
/
/
8
/
/
/
(i) ꢃ
/
x, ꢃ
/
yꢂ
/
1, ꢃ
/
zꢂ
/
1, (ii) ꢃ
/
xꢂ
/
1, ꢃ
/
yꢂ
/
2, ꢃ
/
zꢂ
/
1, (iii) ꢃ
/
xꢂ
/
1, ꢃ
/
yꢂ
/
1, ꢃ
/
zꢂ
/
1, (iv) xꢂ
/
1, yꢃ
/
1, z, (v) ꢃ
/
xꢂ
/
2, ꢃ
/
yꢂ
/
1, ꢃ
/
z, (vi) xꢃ
/
1, yꢂ1, z.
/

30
T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ32
/
Table 4
1H NMR data (d, ppm; J, Hz) for diphenylthallium(III) thiosemicarbazonates
Compound
N(1)H2/OH C(2)H/C(2)ꢀ
/
Ligand protons
TlPh2 protons
CH3
o-Ph
(3JTl ꢀ H
m-Ph
(4JTl ꢀ H
p-Ph
(5JTl ꢀ H
)
)
)
[TlPh2(cptsc)] (1)
[TlPh2(btsc)] (2)
[TlPh2(Hstsc)] (3)
5.02s
a
2.51t (C3,6H2), 2.20b (C3,6H2), 1.61m (C4,5 H2) 7.71d (404) 7.44dt (120) 7.31d (46)
b
b
7.93s
5.70s, 10.76s 8.01s
7.20ꢀ
/
7.6m (C4 ꢀ 8H)
7.75d (417)
7.23td (C6H), 7.08dd (C5H), 6.94d (C8H), 6.83td 7.79d (419)
(C7H)
Â
/
7.50d
c
a
[TlPh2(mbstsc)] (4)
[TlPh2(atsc)] (5)
[TlPh2(ftsc)] (6)
[TlPh2(pytsc)] (7)
7.89s
2.36s (CH3)
7.54d (C5,7H), 6.85d (C4,8H), 3.81s (CH3)
7.77d (420)
b
Â
/
7.48d
Â
/
7.33
7.30
b
b
5.18s
5.26s
5.51s
7.07ꢀ
7.80(C4 ꢀ 8H)
/
8.13s
8.43s
2.54s (CH3)
7.52d (C6H), 6.57d (C4H), 6.49dd (C5H)
8.59s (C7H), 7.79t (C5H), 7.11s (C6H)
7.69d (422) 7.40d (130)
7.68d (450) 7.34d
Â
/
d
Â/
[TlPh2(acpytsc)] (8) 5.44s
8.56d (C7H), 7.83td (C5H), 7.66d (C4H), 7.10b 7.62d (440) 7.32d (133)
(C6H)
7.30d (26)
a
Not observed.
Overlapping ligand ring signals.
b
c
One of the signals of this doublet appears at 7.44 ppm, the other overlaps ligand ring signals and the m-PhTl signals.
Overlapping ligand ring signals and the m-PhTl signals.
d
1
3498 ppm (peak III), although 3 and 5 each show an
additional signal outside these ranges (Table 6). The
presence of more than one signal in the spectra may be
due either to association/dissociation equilibria or to
coordination isomerism. Since 7 and 8 each show a
single peak in the high field region (the location expected
for Tl nuclei that are more shielded than in 1, 2, 4, 5 and
6 due to their higher coordination numbers; vide supra),
these phenomena probably do not affect these com-
plexes, i.e. the N,N,S-coordination observed in the solid
state (vide supra) remains in solution (indeed, even
association via intermolecular TlÁ Á ÁS interactions can-
not be completely ruled out). Note that it is no longer
possible to distinguish three independent molecules as it
is in the crystal; either there is only one species in
chloroform or the three species do not differ enough to
produce significantly distinct 205Tl signals.
3.4.3. Low-temperature H NMR studies
As mentioned above, at room temperature the 1H
NMR spectra of compounds 1ꢀ8 show either one peak
or no peak due to the ꢀN(1)H2 protons. At low
temperature, however, two peaks are obtained, due to
restricted rotation of the ꢀN(1)H2 group about the
C(1)ꢀN(1) bond. As the temperature is raised these two
peaks coalesce at a temperature Tc from which the
energy barrier to rotation of the ꢀN(1)H2 group about
C(1)ꢀN(1) can be obtained using the modified form of
the GutowskyꢀHolm equation [12,27],
/
/
/
/
/
/
/
DGꢄꢁTc[0:191ꢃ0:019 log(Dn=Tc)] (kJ molꢃ1
)
(1)
where DG* is the free energy of activation, Tc the
coalescence temperature in K, and Dn the linewidth in
Hz at the half-height of the coalescence peak.
In this study it was possible to determine coalescence
temperatures for 7 and 8, but for 1ꢀ
the spectra prevented quantitative analysis. The result-
ing calculated barrier to rotation of the ꢀN(1)H2 group
about C(1)ꢀN(1) is somewhat higher in 7 than in 8
(Table 7), which is in keeping with the average C(1)ꢀ
N(1) bond length in the solid state being shorter in 7
than in 8. In both cases, the barrier is somewhat higher
than in thiosemicabazonates of phenylmercury [11,12].
/
6 the complexity of
The multiplicity of signals in 1ꢀ6 may be due partially
/
to dissociation equilibra and partially to co-existence of
complexes with different co-ordination modes (recall
that the structure of [TlMe2(mbtsc)] shows that N(2),S-
coordination is possible as well as N(3),S-coordination
in this type of complex) [19]. The presence of more than
one coordination mode is supported by the fact that the
complex with the greatest number of peaks (four) is 3,
which is probably O,N(3),S-coordinated in the solid
state (vide supra) and which in CDCl3 solution may also
exist as O,N(3)-, N(3),S- and N(2),S-coordinated forms
/
/
/
4. Supplementary material
due to a prototropic ꢀ
/
OHl
/
ꢀN(2)H equilibrium. It
/
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
must nevertheless be pointed out that many of the
species reflected in Table 6 are only present in very low
concentration. The absence of any polymorphism in
solutions of 7 and 8 is possibly attributable to the very
strong N,N,S-coordination of their ligands.
Data Centre, CCDC Nos. 166259ꢀ166261 for com-
/
pounds 1, 7 and 8, respectively. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK

T.S. Lobana et al. / Inorganica Chimica Acta 347 (2003) 23ꢀ
/32
31
Table 6
205Tl NMR data (d, ppm) for diphenylthallium(III) thiosemicarba-
zonates a
Compound Peak I
Peak II
Peak III
1
3741(78.8) 3626(9.5)
3732(5.0), 3765(7.0) 3627(88.0)
3498(11.7)
2
3 b
4
3735(12.6) 3612(79.7)
3766(6.4), 3736(4.9) 3631(88.7)
3466(3.5)
5 c
6
3728(58.2)
3759(7.1)
3635(39.0)
3662(81.7), 3627(11.2)
7
3461(100)
3471(100)
8
a
Percentage of each peak is given in parentheses.
Compound 3 has an additional signal at 3833 (4.2%).
b
Table 7
Calculated barrier to rotation of the N(1)H2 group about the C(1)ꢀ
N(1) bonds of complexes 7 and 8 with average C(1)ꢀS and C(1)ꢀN(1)
/
/
/
distances
ꢄ
Compound Tc
Dn
DGTc (kJ
d(C(1)ꢀ
/
S) d(C(1)ꢀN(1)
/
molꢃ1
)
˚
(A)
˚
(A)
(K) (Hz)
7
8
229 134.6 44.74
223 139.0 43.46
1.720(10)
1.733(8)
1.337(10)
1.352(9)
(fax: ꢂ44-1223-336-033; e-mail: deposit@ccdc.cam.ac.
/
uk or www: http://www.ccdc.cam.ac.uk). Tables listing
detailed crystallographic data, atomic positional para-
meters and bond lengths and angles are available from
the authors on request.
Acknowledgements
We thank the Xunta de Galicia (Spain) for financial
support under project no. PGIDT00PX120301PR. Pro-
fessor T.S. Lobana thanks the Directorate General for
Scientific and Technical Research of the Spanish Min-
istry of Education and Science for financial support as
Visiting Professor (SAB 95-0185) and Guru Nanak Dev
University, Amritsar, India, for the leave of absence.
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