Supramolecular self-assembly of Ph2Tl(S2COME) based on a rare coordination mode of the xanthate ligand and thallium?π -phenyl interactions

Article abstract of DOI:10.1016/S0022-2860(03)00344-2

Diphenylthallium(III) xanthates, Ph₂Tl(S₂COR), R = Me, Et, iso-Pr, Bz, have been prepared from Ph₂TlBr and KS ₂COR, and the crystal structure of Ph₂Tl(S ₂COMe) has been determined by single crystal X-ray diffraction. The compound displays a supramolecular structure consisting of Ph ₂Tl(S₂COMe) tectons, self-assembled through intermolecular Tl?S and Tl?O secondary bonds and Tl?π-phenyl interactions.

Full text of DOI:10.1016/S0022-2860(03)00344-2

Journal of Molecular Structure 656 (2003) 225–230
www.elsevier.com/locate/molstruc
Supramolecular self-assembly of Ph2Tl(S2COMe) based on a rare
coordination mode of the xanthate ligand and thallium· · ·p-phenyl
interactions
a
Jose S. Casas , Alfonso Castin˜eiras , Ionel Haiduc , Agustın Sanchez , Radu
a
b,
a
*
´
´
F. Semeniucb,1, Jose Sordoa
a
´
Departamento de Quimica Inorganica, Facultade de Farmacia, Universidade de Santiago de Compostela, E-15706
Santiago de Compostela, Galicia, Spain
bFacultatea de Chimie, Universitatea Babes-Bolyai, Arany Janos Str. 11, RO-3400 Cluj-Napoca, Romania
Received 18 March 2003; accepted 14 April 2003
Dedicated to Professor Achim Mu¨ller with great admiration for his spectacular contributions to supramolecular inorganic chemistry
Abstract
Diphenylthallium(III) xanthates, Ph2Tl(S2COR), R ¼ Me, Et, iso-Pr, Bz, have been prepared from Ph2TlBr and KS2COR,
and the crystal structure of Ph2Tl(S2COMe) has been determined by single crystal X-ray diffraction. The compound displays a
supramolecular structure consisting of Ph2Tl(S2COMe) tectons, self-assembled through intermolecular Tl· · ·S and Tl· · ·O
secondary bonds and Tl· · ·p-phenyl interactions.
q 2003 Published by Elsevier B.V.
Keywords: Supramolecular; Self-assembly; Crystal structure; Diphenylthallium; Xanthate; Thallium· · ·p-aryl interactions; Secondary bonds
1. Introduction
the soft-metal derivatives self-assemble into supra-
molecular structures [5].
The coordination chemistry of 1,1-dithiolates
(phosphor-1,1-dithiolates [1], dithioarsinates [2],
dithiocarbamates [3], and xanthates [4]) received a
great deal of attention over the time and they still are
an important class of ligands. All these display a great
variety of coordination patterns and quite frequently
The xanthate ligands can be coordinated to metal
atoms (Scheme 1) as monodentate (a), isobidentate (b)
or anisobidentate (c). In rare cases additional metal–
oxygen interaction (coordination) (d) is observed.
Bimetallic bridging also occurs through sulfur atoms
(e), but occasionally the oxygen atom may become
involved (f).
*
Corresponding author. Fax: þ40-264-19-08-18.
We report here the synthesis and characterization
of four new diphenylthallium xanthates. These
compounds seemed attractive due to the remarkable
structural diversity of organotallium compounds in
E-mail address: silazan@yahoo.com (I. Haiduc).
Present address: Department of Chemistry and Biochemistry,
1
University of South Carolina, Columbia, South Carolina 29208,
USA.
0022-2860/03/$ - see front matter q 2003 Published by Elsevier B.V.
doi:10.1016/S0022-2860(03)00344-2

226
J.S. Casas et al. / Journal of Molecular Structure 656 (2003) 225–230
forms I–IV to the overall structure.
These bands are useful in the characterization and,
to some extent, prediction of the structure of the
complex. For example, the presence of a band
[yOC(S2)], above 1200 cm21 is an indication of a
short O–C(S2) bond (form III has an important
contribution), while the shift of that band to lower
frequencies (below 1200 cm21) suggests that form III
has a small contribution to the structure, leading to a
rather long O–C(S2) bond. These suppositions are in
good agreement with results observed in solid state,
based on X-ray structural analyses [8,9].
Scheme 1. Some coordination patterns of xanthate ligands.
As it can be seen in Table 1, only compound 4 has a
band at 1224 cm21, suggesting contribution of form
III. Its absence in compounds 1–3 can be correlated
with a participation of oxygen in secondary bonding
to the metal, as found by X-ray diffraction for
compound 1 (vide infra).
terms of coordination numbers and geometries and
possible supramolecular self-assembly [6].
2. Results and discussion
2.1. Synthesis and characterization of the compounds
2.2. Solid state structure of Ph2Tl(S2COMe) (1)
The compounds were prepared via metathetical
reaction between one equivalent of diphenylthallium
bromide with one equivalent of the corresponding
potassium xanthate in methylene chloride suspension
(Eq. (1)). The diphenylthallium xanthates, Ph2Tl(S2-
COR), R ¼ Me (1), Et (2), iso-Pr (3), Bz (4), are air-
stable white solids, soluble in most common organic
solvents.
Crystallization of 1 from methylene dichloride
afforded X-ray quality crystals. Complete crystal
structure analysis revealed that (1) displays a
supramolecular structure consisting of Ph2Tl(S2-
COMe) tectons [10], self-assembled through inter-
molecular Tl· · ·S and Tl· · ·O secondary bonds and
Tl· · ·p-phenyl interactions. The primary structure of
Table 1
Ph2TlBr þ KS2COR ! Ph2TlS2COR þ KBr
ð1Þ
Infrared spectral data for compounds (1)†(4)
1
2
3
4
Assignmentsa
The infrared absorption spectra of the xanthates
and their metal complexes were extensively studied
[7]. Qualitative studies, supported by normal coordi-
nate analysis, revealed that within these systems (a
xanthate ligand coordinated to a heavy atom) the
vibrations are not pure. Their combination produce
the so called ‘xanthate bands’ around 1260, 1120 and
1025 cm21 [8], where the most important components
are yOC(S2), yaCS2 and ysCS2, respectively. Further-
more, the position of these bands are strongly
influenced by the contribution of the resonance
1476m
1431m
–
1476m
1432m
–
1477s
1475w
1430m
1224m
daO–CH3
dsO–CH3
1433s
–
yOC þ rCH3
þ yaCS2 þ yaCS2
1193s
1130s
1044s
1020m
966w
690s
1975vs
1139m
1036w
1020w
970s
1197vs
1140s
–
1166vs
1130sh
1052vs
1019w
968m
ysCS2
1021vs
968w
694s
yCO þ yaCS2
ysCOC þ ysCS2
ysCS2 þ dCOC
690s
696s
a
The assignments listed here refer only to the major components.

J.S. Casas et al. / Journal of Molecular Structure 656 (2003) 225–230
227
the molecular tecton and the atom numbering scheme
Table 2
Selected bond lengths and angles for (1)
are presented in Fig. 1.
Selected bond lengths and angles are listed in
Table 2. The molecular structure is based on an
anisobidentate coordination mode of the xanthate
ligand, the difference between the two sulfur–
Atoms
Distance
Atoms
Angles
Tl–S(1)
2.845(3)
3.001(2)
2.993(2)
3.204(7)
2.993(2)
2.145(9)
2.138(9)
1.675(9)
1.697(9)
1.347(11)
1.459(10)
S(1)–Tl–S(2)
61.12(7)
168.10(12)
81.83(7)
163.46(10)
142.878(16)
123.9(6)
165.4(4)
48.59(12)
96.7(3)
Tl–S(2)
O(1a)–Tl–S(2a)
S(1)–Tl–S(2a)
Tl–S(2a)–Tl(b)
S(2a)–Tl(b)–S(2)
S(1)–C(1)–S(2)
C(11)–Tl–C(21)
O(1a)–Tl–S(2a)
C(21)–Tl–S(1)
C(11)–Tl–S(1)
C(21)–Tl–S(2)
C(11)–Tl–S(2)
C(21)–Tl–S(2a)
C(11)–Tl–S(2a)
C(11)–Tl–O(2a)
C(21)–Tl–O(2a)
Tl–S(2a)
Tl(b)–O(1)
Tl(b)–S(2)
Tl–C(11)
Tl–C(21)
C(1)–S(1)
C(1)–S(2)
O(1)–C(1)
C(2)–O(1)
˚
thallium distances [Tl–S(1) 2.845(3) A and Tl–
˚
˚
S(2) 3.001(2) A] being around 0.2 A. The phenyl
groups have a deviation from linearity, the C(11)–
Tl–C(21) angle being of 165.4(4)8.
The secondary structure, shown in Fig. 2, is the
result of supramolecular self-assembly through
intermolecular thallium–sulfur secondary bonds
˚
[Tl· · ·S(2a) 2.993(2) A] with additional Tl· · ·O(1a)
˚
interactions (3.203(3) A), leading to a zig-zag
97.8(3)
92.2(2)
95.3(2)
89.8(2)
91.7(2)
chain-like array running along the b axis of the
crystal. These intermolecular distances are shorter
than the corresponding van der Waals distances
86.3(3)
83.8(3)
Symmetry transformations used to generate equivalent atoms:
˚
˚
(Tl· · ·S 4.46 A and Tl· · ·O 4.10 A according to
Batsanov [11]).
(a) 2x þ 1; y þ 1=2; 2z þ 1=2; (b) 2x þ 1; y 2 1=2; 2z þ 1=2:
second thallium atom in a chain is connected to a
phenyl ring on the same side of a parallel chain.
Intermolecular Tl· · ·p-phenyl interactions leading to
supramolecular self-assembly have been previously
observed in some thallium phenyl–pyrazolyl com-
plexes and in other compounds [12].
In the crystal the supramolecular chains are further
associated through thallium· · ·p-phenyl interactions
between adjacent chains, leading to a 2D stepped
layered structure shown in Fig. 3. In this arrangement
a phenyl group occupies the apparently empty space
of an opposite thallium atom. It is noted that every
In the molecular tecton (Fig. 1) the thallium atom is
four-coordinate, with a c-trigonal bipyramidal geo-
metry. If all the interactions are considered, the
thallium atom becomes seven-coordinate (see Fig. 3)
with a distorted pentagonal-bipyramidal geometry
with axial phenyl groups, four equatorial positions
occupied by three sulfur atoms and an oxygen atom.
The p-aryl group occupies the fifth equatorial
˚
position, with the Tl· · ·centroid distance of 3.893 A.
This value is shorter than the sum of the van der Waals
˚
radius of thallium (2.46 A) and the half-thickness of
˚
the phenyl ring (1.77 A). The distance between the
centroids of opposite (parallel) phenyl groups is
˚
5.183 A, too large for any significant p–p interaction.
The structure of our compound can be compared
with that of Me2Tl(S2COMe) [13]. The latter is also a
supramolecular solid made of Me2Tl(S2COMe) che-
˚
late molecular tectons (Tl–S 2.98(2) and 2.96(3) A)
with intermolecular contacts leading to a bidimen-
sional layer made of interacting chain-like arrays
Fig. 1. Molecular structure of Ph2Tl(S2COMe). Color scheme:
thallium purple, carbon orange, sulfur yellow, oxygen red.
˚
(Tl· · ·S 3.19 A, Tl· · ·O 3.13 A within the chain). In
˚

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J.S. Casas et al. / Journal of Molecular Structure 656 (2003) 225–230
Fig. 2. Secondary structure formed by supramolecular self-assembly of (1).
this compound the chains are associated through
Tl· · ·S secondary bonds (interchain distances Tl· · ·S
˚
3.35 A). The coordination geometry of seven-coordi-
a biconnective and a monoconnective sulfur atom
and a monoconnective oxygen atom. Of the metal–
ligand interactions in this pattern, two are secondary
bonds (Tl· · ·S and Tl· · ·O).
nate thallium is distorted pentagonal-bipyramidal,
with axial methyl groups and the equatorial positions
occupied by four sulfur atoms and an oxygen atom.
In both compounds R2Tl(S2COR) the rare co-
ordination pattern (f) is present, which involves
A somewhat related structure is that of Me2-
Tl(OSPPh2) [14], which involves c-trigonal-bipyra-
midal coordination of thallium, with four equatorial
positions occupied by two sulfur and two oxygen
Fig. 3. Supramolecular 2D (layer) tertiary structure of (1) formed by Tl· · ·p-phenyl inter-chain interactions.

J.S. Casas et al. / Journal of Molecular Structure 656 (2003) 225–230
229
atoms. In this structure, the chain-like arrays are not
associated into a tertiary structure, probably because
of the steric bulkiness of the phenyl groups.
3.3. Crystallographic studies
A colorless prismatic crystal of Ph2Tl(S2COMe)
was grown by slow evaporation of a dichloromethane
solution of the compound. The crystal was mounted
on a glass fibber and used for data collection. Cell
constants and an orientation matrix for data collection
were obtained by least-squares refinement of the
diffraction data from 25 reflections in an Enraf Nonius
MACH3 automatic diffractometer [16]. Data were
collected at 293 K using Mo Ka radiation
3. Experimental
3.1. General
All reactions were carried out in open air.
Elemental analysis was performed on a Perkin
Elmer 240B apparatus. Melting points are uncorrected
as determined on a Bu¨chi apparatus. IR spectra were
recorded on a Perkin Elmer 1330 spectrometer (KBr
pellets). The starting material Ph2TlBr was prepared
as described in Ref. [15]; all solvents were commer-
cial products of analytical grade purity (Aldrich) and
used as supplied. Sodium methylxanthate or potass-
ium benzylxanthate were prepared from the appro-
priate alcohol, sodium or potassium hydroxide and
carbon disulphide, with excess alcohol acting as
solvent. The synthesis of diphenylthallium methyl-
xanthate is representative for all other syntheses in
this work.
˚
(l ¼ 0:71073 A) and the v scan technique and
corrected for Lorentz and polarization effects [17].
A semiempirical absorption correction (c scan) was
made [18].
The structure was solved by direct methods [19]
which revealed the position of all non-hydrogen
atoms, and refined on F2 by a full-matrix least-squares
procedure using anisotropic displacement parameters
[20]. All hydrogen atoms were located from differ-
ence Fourier maps except those of the methyl groups
which were located in their calculated positions (C–
˚
H ¼ 0.96 A). The located H atoms were refined
isotropically, whereas the calculated H atoms were
Table 3
Crystal and structure refinement data for (C6H5)2Tl(S2COCH3) (1)
3.2. Synthesis of compounds
Empirical formula
Formula weight
Temperature (K)
Wavelength
C14H13OS2Tl
Ph2Tl(S2COMe). To a suspension of Ph2TlBr
(0.439 g, 0.001 mol in 50 ml methylene chloride) was
added a solution of NaS2COMe (0.130 g, 0.001 mol in
50 ml ethanol). After 2 h of stirring the solution was
filtered and concentrated under vacuum (ca. 10 ml)
and petroleum ether (50 ml, b.p. 40–60 8C) was added
to precipitate a white powder identified as Ph2Tl(S2-
COMe) (yield: 51%, m.p. ¼ 150 8C dec.).
C14H13OS2Tl requires C, 36.10%, H, 2.81%, S,
13.77%; found C, 36.04%, H, 2.80%, S, 14.13%.
Similarly prepared were the following.
465.73
293(2)
0.71073
Crystal system
Monoclinic
Space group
˚
a (A)
˚
b (A)
P21=c
9.9426(17)
11.2339(11)
˚
c (A)
13.3300(20)
a (deg)
b (deg)
g (deg)
90
90.85(2)
90
3
˚
Volume (A )
1488.7(4)
Z
4
Density (calc.) (Mg m23
)
2.078
Ph2Tl(S2COEt). Yield: 54%, m.p. ¼ 150 8C dec.
C15H15OS2Tl requires C, 37.55%, H, 3.15%, S,
13.37%; found C, 37.83%, H, 2.88%, S, 12.84%.
Ph2Tl(S2COPri). Yield: 53%, m.p. ¼ 190 8C dec.
C17H19OS2Tl requires C, 40.21%, H, 3.77%, S,
12.63%; found C, 39.64%, H, 3.37%, S, 13.46%.
Ph2Tl(S2COBz). Yield: 48%, m.p. ¼ 145 8C dec.
C20H17OS2Tl requires C, 44.33%, H, 3.16%, S,
11.84%; found C, 43.98%, H, 2.80%, S, 11.20%.
Absorption coefficient (mm21
)
11.115
Fð000Þ
872
Crystal size (mm3)
0.35 £ 0.25 £ 0.10
3733
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices ½I . 2sðIÞꢀ
R indices (all data)
3582 ½RðintÞ ¼ 0:0456ꢀ
3582/0/165
0.979
R1 ¼ 0:0427; wR2 ¼ 0:1041
R1 ¼ 0:1027; wR2 ¼ 0:1233

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J.S. Casas et al. / Journal of Molecular Structure 656 (2003) 225–230
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data, experimental details and refinement results are
listed in Table 3.
[6] J.S. Casas, M.S. Garcia-Tasende, J. Sordo, Coord. Chem. Rev.
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4. Supplementary material
Crystallographic information on (1) has been
deposited with the Cambridge Crystalographic Data
Center as supplementary publication number CCDC
208123. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: þ44-1223-033;
e-mail: deposit@ccdc.cam.ac.uk).
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Acknowledgements
We thank Xunta de Galicia (Spain) [Grant XUGA
20308 B 97] and the National Council for Academic
Research (Roumania) [Grant No. 88] for the financial
support of this work.
´
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