2-Thiophenyltellurium derivatives: Alternative synthetic routes and structural characterization

Article abstract of DOI:10.1016/j.ica.2011.05.039

Grignard reagent prepared from 2-thiophenyl bromide in THF consumes elemental tellurium readily at room temperature and provides a route to obtain bis(2-thiophenyl)ditelluride, Tpn₂Te₂ (1, Tpn = 2-C ₄H₃S) in goo

Full text of DOI:10.1016/j.ica.2011.05.039

Inorganica Chimica Acta 376 (2011) 80–86
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
2-Thiophenyltellurium derivatives: Alternative synthetic routes
and structural characterization
a
a
b
c
Ashok K.S. Chauhan a, , Poornima Singh , Ramesh C. Srivastava , Ray J. Butcher , Andrew Duthie
⇑
a Department of Chemistry, University of Lucknow, Lucknow 226007, India
b Department of Chemistry, Howard University, Washington, DC 20059, USA
c School of Life and Environmental Sciences, Deakin University, Geelong 3217, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
Grignard reagent prepared from 2-thiophenyl bromide in THF consumes elemental tellurium readily at
room temperature and provides a route to obtain bis(2-thiophenyl)ditelluride, Tpn2Te2 (1, Tpn = 2-
C4H3S) in good yield. It can also thiophenylate aryltellurium(II) bromides, producing solutions of mixed
aryl(heteroaryl)tellurides, which when chlorinated give crystalline aryl(heteroaryl)tellurium(IV) dichlo-
Received 14 March 2011
Received in revised form 20 May 2011
Accepted 31 May 2011
Available online 6 June 2011
rides, ArTpnTeCl2 (Ar = 1-C10H7, Npl; 2,4,6-Me3C6H2, Mes). Oxidative addition of a-bromo-N,N-diethylac-
etamide to (2-thiophenyl)tellurium(II) bromide, gave the mixed alkyl(heteroaryl)tellurium(IV)
dibromide, (Et2NCOCH2)TpnTeBr2. Ditelluride 1 can be detellurated by electrolytic copper to the bis(2-
thiophenyl)telluride, Tpn2Te (2). Chemical shifts, d(1H, 13C and 125Te) for (2-thiophenyl)tellurium(IV)
halides are reported. Crystal structures of Tpn2TeBr2 (2b), Tpn2TeI2 (2c) and Mes(Tpn)TeCl2 (2e) have
been determined unambiguously. In the case of 2e, steric repulsion of the mesityl ligand counters the tel-
lurium lone pair repulsion to widen the equatorial C–Te–C angle to the extent of 108°. In the crystal lat-
tices of 2b and 2c, the intermolecular TeÁ Á ÁX secondary bonds give rise to an interesting tetrameric
supramolecular architecture with S2 symmetry that defies the stereochemical activity of the lone pair
on the central tellurium atom.
Keywords:
Tellurated thiophene
Detelluration
Secondary bonding interactions
Sterically inactive lone pair
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
dihalides Tpn2TeX2 (X = Cl (2a), Br (2b), I (2c)) and preparation of
mixed diaryl- and alkylaryltellurium(IV) dihalides ArTpnTeCl2
The tellurated thiophene derivatives, Tpn2TeX2 (Tpn = 2-C4H3S),
Tpn2Te and Tpn3TeBr were first reported in 1929 [1,2] using TeBr2
as precursor. The mono and ditellurides, (Tpn2Te, Tpn2Te2), have
since been prepared by the use of 2-thiophenyllithium [3,4] and
also characterized crystallographically [5,6]. Though the formation
of TpnTeCl3 has been implied in one of the preparations of Tpn2Te2
(from TeCl4 and TpnHgCl) [7,8], no trihalide has so far been iso-
lated. In the other cases too, characterization has mostly been lim-
ited to elemental analyses and 1H NMR data. Surprisingly, insertion
of elemental tellurium into the Mg–C(Tpn) bond has not been
exploited as a synthetic route to obtain 2-thiophenyltellurium
derivatives, though this synthetic protocol is known for other aryl-
tellurium derivatives [9].
(Ar = 1-C10H7, Npl (2d), 2,4,6-Me3C6H2, Mes (2e)) and (Et2N-
COCH2)TpnTeBr2 (2f); (ii) 1H, 13C and 125Te NMR spectra of the sol-
uble compounds and (iii) structure elucidation of 2b, 2c and 2e by
single-crystal X-ray diffraction. Our interest in this area derives
from earlier work on the characterization of functionalized organo-
tellurium(II and IV) derivatives synthesized directly from elemen-
tal tellurium, including those derived from 2-acetylthiophene
[10,11]. The carbonyl O atom of each acylmethyl groups in
(RCOCH2)2TeX2 is invariably involved in intramolecular 1,4-TeÁ Á ÁO
non-covalent interactions, with cisoidal orientation of the organic
ligands imparting C2v symmetry to the (C–C(O)–CH2–)2TeX2 skele-
tal framework in the solid state. Interestingly, in case of (TpnC-
OCH2)2TeBr2, one of the 2-thiophenoylmethyl ligands adopts
trans disposition with respect to the other and its carbonyl O atom
is devoid of the 1,4-TeÁ Á ÁO interaction [11]. This observation
emphasizes the role of the ring heteroatom as the cisoidal con-
former would cause concentration of electron density in the
domain of the lone pair at the central Te atom. As even subtle
changes in electronic factors can be useful in the field of material
science, systematic preparation and characterization of the tellu-
rated thiophene derivatives was considered worthwhile so that a
comparison with the phenyltellurium analogues could be made.
This communication details (i) an improved alternative synthe-
sis of bis(2-thiophenyl)ditelluride, Tpn2Te2 (1), its detelluration to
the corresponding monotelluride, Tpn2Te (2), oxidative halogen-
ations to trihalides TpnTeX3 (X = Cl (1a), Br (1b), I (1c)) and
⇑
Corresponding author. Tel.: +91 9415010763; fax: +91 522 2338531.
E-mail addresses: akschauhan2003@yahoo.co.in (A.K.S. Chauhan), poornima05-
singh@yahoo.co.in (P. Singh), rameshlko@yahoo.co.nz (R.C. Srivastava), rbutcher99
@yahoo.com (R.J. Butcher), aduthie@deakin.edu.au (A. Duthie).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.05.039

A.K.S. Chauhan et al. / Inorganica Chimica Acta 376 (2011) 80–86
81
Table 1
2. Experimental
Chemical shifts (d 125Te, in ppm) of organotellurium(I, II and IV) compounds in CDCl3.
2.1. General procedures
Compound
R = 2-thiophenyl (Tpn)
R = phenyl
R = methyl
R2Te2
R2Te
447 (264 [14])
409
871
421 [14]
690 [15]
917 [15]
890a [16]
–
–
0
Preparative work was performed under dry nitrogen. Melting
points were recorded in capillary tubes and are uncorrected. All
solvents were purified and dried before use. The starting material
2-bromothiophene was used as procured from Merck KGaA,
Germany. 1-Naphthyltellurium trichloride and mesityltellurium
trichloride were prepared by chlorination of their corresponding
R2TeCl2
R2TeBr2
R2TeI2
RTeCl3
RTeBr3
RTeI3
734 [15]
649 [15]
520 [15]
758d [16]e
647d [16]e
–
845
816
1524,872b
1100f
1229c [17]
1193c [17]
1101c [17]
1173f
ditellurides with SO2Cl2.
a-Bromo-N,N-diethylacetamide was pre-
a
b
c
In PhCH3-d8.
d
In CD2Cl2/DMSO-d6.
In C6D6/PhCH3-d8.
125Te values indicate dismutation to TeCl4 and Tpn2TeCl2.
pared by the reported method [10]. IR spectrum was recorded as
KBr pellets using a Perkin–Elmer RX1 spectrometer. 1H NMR spec-
tra were recorded at 300.13 MHz in CDCl3 on a Bruker DRX300
spectrometer using Me4Si as the internal standard. 13C{1H}
(100.54 MHz) and 125Te{1H} (126.19 MHz) NMR spectra were re-
corded on a JEOL Eclipse Plus 400 NMR spectrometer, using Me4Si
and Me2Te as internal standards. Spectra for compounds 1b and 1c
were obtained in 1:1 CDCl3/DMSO-d6 solutions, while all other
were in CDCl3. Reported values of chemical shifts (d) are in ppm.
Microanalyses were carried out using a Carlo Erba 1108 analyzer.
Tellurium was estimated volumetrically.
d
e
d
125Te values reported appear to be incorrect and are most likely due to the
dimethyltellurium(IV) dihalides.
f
In CDCl3/DMSO-d6.
Te, 27.80%. 13C{1H} NMR: d 125.1, 132.1, 136.7, quaternary C not
located. 125Te{1H} NMR: d 1100.
Likewise, 1c was prepared as a gray solid by the addition of io-
dine (0.38 g, 1.50 mmol) to a solution of 1 (0.21 g, 0.50 mmol).
Yield: 0.53 g (90%). M.p.: 126 °C. Anal. Calc. for C4H3SI3Te
(591.45): C, 8.12; H, 0.51; Te, 21.57. Found: C, 8.14; H, 0.28; Te,
21.95%. 13C{1H} NMR: d 126.7, 133.1, 139.1, quaternary C not lo-
cated. 125Te{1H} NMR: d 1173.
2.2. Syntheses
2.2.1. Synthesis of bis(2-thiophenyl)ditelluride, Tpn2Te2, 1
Magnesium turnings (0.50 g, 20.6 mmol) were flame dried un-
der dry N2 in a two neck 250 mL round bottom flask. On cooling,
2.2.3. Synthesis of bis(2-thiophenyl)telluride, Tpn2Te, 2
dry tetrahydrofuran (20 mL), a pinch of iodine and
a-bromothio-
Bis(2-thiophenyl)ditelluride 1 (0.50 g, 1.19 mmol) and freshly
prepared electrolytic copper (0.166 g, 2.61 mmol) were refluxed
in toluene (20 mL) for 2 h, during which the color of the solution
changed from red to yellow. It was filtered and the solvent re-
moved completely on a rotary evaporator. The solid obtained upon
cooling of the resulting oil was recrystallized from hexane to give
cream colored crystals of 2. Yield: 0.26 g (75%). M.p.: 42 °C (Ref.
[2] 50.5 °C). Anal. Calc. for C8H6S2Te (293.86): C, 32.70; H, 2.06;
Te, 43.42. Found: C, 32.92; H, 2.16; Te, 42.86%. 1H NMR: d 6.90–
6.93 (dd, 1H), 7.40–7.45 (m, 2H). 13C{1H} NMR: d 102.7, 128.8,
134.4, 140.6. 125Te{1H} NMR: d 409.
phene (1.8 mL, 18.6 mmol) were added and stirred until the mag-
nesium had been consumed (ꢀ1 h). Freshly ground tellurium
powder (2.30 g, 18.0 mmol) was then added in two portions and
stirring continued until all the tellurium was consumed. The
resulting gray solution was then exposed to air and stirred for an-
other 15 min, during which a deep red color developed. It was then
poured into an aqueous 5% solution of ammonium chloride and ex-
tracted with 250 mL chloroform. The extract was dried over anhy-
drous CaCl2, filtered and concentrated under reduced pressure to
ꢀ5 mL. Ethanol (5 mL) was added and the solution kept at
À10 °C overnight, giving a red solid that was recrystallized from
ethanol to give red crystals of 1. Yield: 2.95 g (75%). M.p.: 87–
88 °C (Ref. [4] 88 °C). 13C{1H} NMR: d 94.0, 128.6, 134.9, 141.5.
125Te{1H} NMR: d 447.
2.2.4. Oxidative halogen addition reactions of Tpn2Te, 2
Compound 2a: Sulfuryl chloride (0.040 mL, 0.50 mmol) in car-
bon tetrachloride (5 mL) was added dropwise to a cooled and stir-
red solution of bis(2-thiophenyl)telluride, 2 (0.147 g, 0.50 mmol)
in carbon tetrachloride (5 mL), to give a white precipitate. It was
filtered and recrystallized from dichloromethane/petroleum ether
40–60 °C to give colorless needles of 2a. Yield: 0.16 g (85%). M.p.:
184–185 °C (Ref. [1] 185.5 °C). Anal. Calc. for C8H6S2TeCl2
(364.77): C, 26.34; H, 1.66; Te, 34.98. Found: C, 26.02; H, 1.46;
Te, 35.18%. 1H NMR: d 7.23 (t, 1H), 7.79 (d, 1H), 8.15 (d, 1H).
13C{1H} NMR: d 127.1, 128.6, 135.7, 138.2. 125Te{1H} NMR: d 871.
2.2.2. Oxidative halogen addition reactions of Tpn2Te2, 1
Compound 1a: Dropwise addition of a solution of SO2Cl2
(0.12 mL, 1.50 mmol) in dichloromethane (5 mL) to a stirred red
solution of 1 (0.21 g, 0.50 mmol) in the same solvent (10 mL) at
0 °C followed by stirring at room temp (2 h), resulted in the precip-
itation of 1a as a yellow solid that was collected by filtration. Yield:
0.30 g (95%). M.p.: 122–124 °C (freshly prepared 1a). 125Te{1H}
NMR: d 872 and 1524 (1:1). See comments at Table 1. The yellow
solid gradually changes white and attempt to purify it by crystalli-
zation failed. After several recrystallizations the analysis was found
to correspond to that of 2a [C, 26.67; H, 1.72].
When the freshly prepared 1a (0.16 g, 0.50 mmol) in 10 mL
dichloromethane was shaken with an aqueous solution of Na2S2O5
(0.38 g, 2 mmol in 5 mL of water), the color of the organic layer
changed to red within a few minutes. The product isolated from
the organic layer was Tpn2Te2. M.p.: 87–88 °C. Yield: 0.08 g, 76%.
Compound 1b was obtained as yellow solid from 1 (0.21 g,
0.50 mmol) and Br2 (0.09 mL, 1.76 mmol) in carbon tetrachloride
and was recrystallized from dimethyl sulfoxide to give yellow crys-
tals. Yield: 0.40 g (88%). M.p.: 160 °C. Anal. Calc. for C4H3SBr3Te
(450.44): C, 10.67; H, 0.67; Te, 28.33. Found: C, 10.04; H, 0.32;
Compound 2b was prepared similarly from
2 (0.147 g,
0.50 mmol) and bromine (0.026 mL, 0.50 mmol) to give a yellow
solid that was recrystallized as yellow rectangular crystals from
dichloromethane. Yield: 0.22 g (95%). M.p.: 194–196 °C (Ref. [1]
190.5 °C). Anal. Calc. for C8H6S2TeBr2 (453.67): C, 21.18; H, 1.33;
Te, 28.13. Found: C, 21.65; H, 1.03; Te, 28.50%. 1H NMR: d 7.22 (t,
1H), 7.78 (d, 1H), 8.21 (d, 1H). 13C{1H} NMR: d 121.9, 128.6,
135.8, 139.3. 125Te{1H} NMR: d 845.
Likewise, 2c was obtained from 2 (0.146 g, 0.50 mmol) and io-
dine (0.127 g, 0.50 mmol) as dark red crystals on crystallization
from dichloromethane. Yield: 0.244 g (88%). M.p.: 145 °C (Ref. [1]
125 °C). Anal. Calc. for C8H6S2TeI2 (547.67): C, 17.54; H, 1.10; Te,
23.30. Found: C, 17.48; H, 0.97; Te, 23.05%. 13C{1H} NMR: d
114.1, 128.6, 136.2, 143.0. 125Te{1H} NMR: d 816.

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A.K.S. Chauhan et al. / Inorganica Chimica Acta 376 (2011) 80–86
2.2.5. Synthesis of aryl(2-thiophenyl)tellurium(IV) dichlorides
Compound 2d: A solution of Grignard reagent (2.0 mmol) pre-
pared from magnesium (0.049 g, 2.0 mmol) and 2-thiophenyl bro-
mide (0.19 mL, 2.0 mmol) in dry THF (10 mL) was added slowly to
a solution of 1-naphthyltellurium(II) bromide (2.0 mmol) [pre-
pared in situ by the addition of THF solution (5 mL) of bromine
(0.05 mL, 1.0 mmol) to a stirred solution of dinaphthylditelluride
(0.51 g, 1.0 mmol) in the same solvent at 0 °C] under nitrogen
atmosphere. The reaction mixture was stirred at room temperature
for 1 h and then poured into a beaker containing aqueous 5% NH4Cl
solution, extracted with dichloromethane (2 Â 10 mL), washed
with water and dried over anhydrous Na2SO4. The residue obtained
after removal of the volatiles was extracted with hexane (10 mL)
and a solution of SO2Cl2 (0.16 mL, 2.0 mmol) in hexane (5 mL)
added to it drop wise at 0 °C. The solid product was recrystallized
from dichloromethane to give yellow rectangular crystals of 2d.
Yield: 0.354 g (43%). M.p.: 225 °C. Anal. Calc. for C14H10Cl2STe
(408.8): C, 41.13; H, 2.47; Te, 31.21. Found: C, 41.45; H, 2.96; Te,
30.59%. 1H NMR: d 7.45–8.43. 13C{1H} NMR: d 126.0, 126.3,
126.7, 127.3, 127.9, 128.3, 129.4, 129.8, 132.5, 133.1, 135.4,
138.2, 141.0. 125Te{1H} NMR: d 845.
Compound 2e was prepared similarly from 2-thiophenyl mag-
nesium bromide (5.0 mmol) and mesityltellurium(II) bromide
(5.0 mmol) [obtained in situ from bromine (0.13 mL, 2.5 mmol)
and dimesityl ditelluride (1.23 g, 2.5 mmol)] as colorless crystals.
Yield: 0.650 g (32%). M.p.: 105 °C. Anal. Calc. for C13H14Cl2STe
(400.82): C, 38.95; H, 3.52; Te, 31.83. Found: C, 38.72; H, 3.47;
Te, 31.75%. 1H NMR: d 2.14 (s, 3H, o-Me), 2.29 (s, 3H, o-Me), 2.85
(s, 3H, p-Me), 6.88 (s, 1H, m-H), 6.99 (s, 1H, m-H) of the mesityl
ring, 7.32 (t, 1H), 7.92 (d, 1H), 8.41 (d, 1H) of the thiophene ring.
13C{1H} NMR: d 21.0 (p-Me), 21.4 (o-Me), 23.5 (o-Me), 121.2,
129.4, 130.5, 131.9, 137.4, 138.3, 140.1, 140.2, 141.6, 141.9.
125Te{1H} NMR: d 828.
ꢀ2 mL followed by the addition of petroleum ether gave yellow
rectangular crystals of 2b. Yield: 0.08 g (35%). M.p.: 194 °C.
2.3. Crystallography
Single crystals suitable for X-ray crystallography were ob-
tained by slow evaporation of dichloromethane solutions of 2b,
2c and 2e. Intensity data were collected on an Oxford Diffraction
Gemini CCD diffractometer with graphite-monochromated Mo K
a
(0.7107 Å) radiation. Data were reduced and corrected for absorp-
tion using spherical harmonics, implemented in SCALE3 ABSPACK
scaling algorithm in the CrysAlisPro, Oxford Diffraction Ltd., Ver-
sion 1.171.33.34d program. The structures were solved by direct
methods and difference Fourier synthesis using SHELXS-97 and OR-
TEP figures generated using the program WinGX 2002 [12,13].
Full-matrix least-squares refinements on F2, using all data, were
carried out with anisotropic displacement parameters applied to
non-hydrogen atoms. Hydrogen atoms attached to carbon were
included in geometrically calculated positions using a riding mod-
el and were refined isotropically. Crystal data and structure
refinement details are given in Table 2. Geometrical parameters
relevant to the primary geometry of the Te atom in each are in-
cluded in the captions.
3. Results and discussion
3.1. Synthesis
The synthetic routes to obtain 2-thiophenyltellurium deriva-
tives are presented in Scheme 1. Elemental tellurium inserts read-
ily into the Mg–C bond of TpnMgBr in THF at room temperature to
give, after oxidation and hydrolysis, bis(2-thiophenyl)ditelluride,
Tpn2Te2 (1). Trihalides TpnTeX3 (X = Cl (1a), Br (1b), I (1c)) were
obtained by addition of sulfuryl chloride, bromine or iodine to
dichloromethane or carbon tetrachloride solutions of 1 in a 3:1 M
ratio at 0 °C. These trihalides appear to be intrinsically unstable
as their acetronitrile and DMSO solutions gradually changed color
and often poor elemental analyses were obtained, particularly in
the case of 1a. 125Te NMR spectrum of 1a showed two signals,
1524 ppm signal may be due to a highly deshielded Te species,
TeCl4 and the 872 ppm signal corresponds to Tpn2TeCl2 (2a). These
species appear to be the result of dismutation of 1a in CDCl3. How-
ever, the freshly prepared 1a on reduction affords ditelluride 1 in
good yield.
Detellutration of 1 by freshly prepared electrolytic copper gives
bis(2-thiophenyl)telluride, Tpn2Te (2) which was initially prepared
by the reaction of TpnMgBr on TeBr2 or reduction of Tpn2TeBr2
with SnCl2 [1,2]. The oxidative addition of sulfuryl chloride, bro-
mine or iodine to a chloroform or dichloromethane solution of 2
at 0 °C gives crystalline symmetrical bis(heteroaryl)tellurium
dihalides, Tpn2TeX2 (X = Cl (2a), Br (2b), I (2c)). Alternatively, 2a
2.2.6. Synthesis of (N,N-diethylamidomethyl)(2-
thiophenyl)tellurium(IV) dibromide, 2f
To a stirred solution of 1 (0.21 g, 0.50 mmol) in dichlorometh-
ane (10 mL), a solution of bromine (0.025 mL, 0.50 mmol) in
dichloromethane (5 mL) was added dropwise at 0 °C.
a-Bromo-
N,N-diethylacetamide (0.14 mL, 1.0 mmol) was added to it and
the resulting solution stirred for 20 h. A small amount of elemental
tellurium was removed by filtration and the filtrate passed through
a short silica column. Upon concentration to ꢀ1 mL and addition of
hexane, a solid separated that was recrystallized from dichloro-
methane to give yellow 2f. Yield: 0.187 g (39%). M.p.: 174–
175 °C. Anal. Calc. for C10H15Br2NOSTe (484.71): C, 24.78; H, 3.12;
Te, 26.33. Found: C, 24.59; H, 3.05; Te, 26.45%. 1H NMR: d 1.20 (t,
3H, Me), 1.27 (t, 3H, Me), 3.37 (q, 2H, CH2N), 3.48 (q, 2H, CH2N),
4.68 (s, 2H, CH2Te), 7.23 (s, 1H), 7.79 (s, 1H), 8.22 (s, 1H) thiophene
ring protons. IR (cmÀ1): 1655 (
mC@O).
2.2.7. Alternative synthetic procedures for 2a and 2b
Bis(2-thiophenyl)ditelluride 1 (1.54 g, 3.66 mmol) was refluxed
with mercury(II) chloride (1.50 g, 5.53 mmol) in chloroform
(20 mL) with continuous stirring for 7 h. The chloroform layer be-
came colorless and was filtered. The filtrate was reduced to 2 mL
and addition of petroleum–ether afforded a colorless solid that
was recrystallized from dichloromethane to give colorless needles
of 2a. Yield: 1.067 g (80%). M.p.: 184 °C.
TpnTeX3
SO2Cl2,
Br2 or I2
X = Cl (1a), Br (1b), I (1c)
Et2NCOCH2Br
Br2
Tpn2Te2
[TpnTeBr]
(Et2NCOCH2)TpnTeBr2
2f
1
Cu
X2
Tpn2Te
2
Tpn2TeX2
Te [O]
X = Cl (2a), Br (2b), I (2c)
Refluxing of 1 (0.21 g, 0.50 mmol) with N-bromosuccinimide
(0.178 g, 1.00 mmol) in acetonitrile for 3 h resulted in slow decol-
orization of the solution. It was cooled, filtered and the filtrate re-
duced to ꢀ2 mL. Addition of petroleum ether afforded a yellow
solid that was extracted with hot dichloromethane and passed
through a short silica column. Evaporation of the clear extract to
[ArTeBr]
SO2Cl2
TpnMgBr
ArTpnTe
ArTpnTeCl2
Ar = 1-C10H7, Npl (2d);
Tpn = 2-thiophenyl
2,4,6-Me3C6H2, Mes (2e)
Scheme 1. Reactions of TpnMgBr.

A.K.S. Chauhan et al. / Inorganica Chimica Acta 376 (2011) 80–86
83
and 2b were prepared by the reaction of 1 with mercuric chloride
and N-bromosuccinimide, respectively; elemental Te separates out
in each case. Thiophenylation of aryltellurium(II) bromides, ArTeBr
(prepared in situ from Ar2Te2 and Br2 in THF), with TpnMgBr leads
to the formation of unsymmetrical tellurides, ArTpnTe, which were
characterized as ArTpnTeCl2 (Ar = Npl (2d), Mes (2e)). The oxida-
diorganotellurium dihalides, variation of d 125Te values is consis-
tent with the electronegativity of the halo ligands.
3.3. Molecular and crystal structures
Crystal data and structure refinement details of compounds 2b,
2c and 2e are given in Table 2. Fig. 1 depicts an ORTEP view of the
molecular geometry of compounds 2b and 2c, which are isomor-
phous, while Fig. 2 shows an ORTEP view of 2e.
Asymmetric units in the lattices of diaryltellurium dihalides 2b,
2c and 2e have two independent molecules and the ring atoms of
the thiophenyl ligands are twofold disordered. The spatial arrange-
ment of ligand atoms around the hypervalent four-coordinate Te
atom in each of these Te(IV) compounds conforms to the usual
C2TeX2 grouping butterfly shape.
tive addition of
a-bromo-N,N-diethylacetamide to TpnTeBr (pre-
pared in situ from 1 and Br2 in dichloromethane) resulted in a
yellow crystalline alkyl(heteroaryl)tellurium(IV) dibromide, (Et2N-
COCH2)TpnTeBr2 (2f). The mono and ditellurides (2 and 1) and the
dihalides (2a–2f) are fairly soluble in halogenated solvents, but the
trihalides (1a–1c) show poor solubility in common organic sol-
vents and gradually change color in solution.
3.2. Spectroscopic studies
The equatorial C–Te–C angles for 2b and 2c, covering the range
91.0(4)–95.5(1)°, are significantly lower than the putative value of
120° for a trigonal bipyramidal geometry due to the stereochem-
ical activity of the lone pair on Te. In 2b and 2c, the planes of the
thiophenyl rings adopt a propeller arrangement (with respect to
the equatorial plane) and the hetero atoms have a trans disposi-
tion, imparting C2 molecular symmetry. On the other hand, in
the chloro analogue, 2a, the parallel heteroaromatic rings are
nearly perpendicular to the equatorial C–Te–C plane, resulting
in an idealized butterfly molecular shape [18]. The larger axial
halo ligands appear to influence the orientations of the heteroar-
omatic rings in 2b and 2c. In the mixed diaryltellurium(IV)
dichloride (2e), steric demand of the mesityl ligand enlarges the
equatorial angle in the two independent molecules (108.4(2)°,
108.3(2)°) and the planes of the aromatic rings are orientated al-
most orthogonally to each other (the interplaner angles in its two
molecules are 85.4(1)° and 88.9(2)°).
In the 1H NMR spectra of the thiophenyltellurium derivatives,
protons of the thiophene moiety appear in the aromatic region
as multiplets. The compound 2f shows signals due to methyl
and methylene protons in the expected region. Appearance of
two singlets for the o-Me groups in 2e indicates restricted
rotation along the Te–C(Mes) bond. All 13C NMR spectra are
characteristic of 2-thiophenyltellurium derivatives, with the
unsubstituted
a-carbon being the most deshielded of all the ring
carbons in the thiophene moiety. The 125Te NMR spectra of
2-thiophenyltellurium derivatives 1, 1b–1c, 2 and 2a–2e show
only one 125Te chemical shift, consistent with the presence of
only one Te containing species in solution. When compared with
those of phenyl [14–17] and methyl [15,16] analogues (Table 1),
the d 125Te values for 2-thiophenyltellurium derivatives show
that the shielding due to the hetero aryl group is greater than
the phenyl but smaller than the methyl group. Among the
Table 2
Crystal data and structure refinement details of 2b, 2c and 2e.
2b
2c
2e
Empirical formula
Formula mass (g molÀ1
T (K)
C8H6Br2S2Te
453.67
295(2)
C8H6I2S2Te
547.65
293(2)
C13H14Cl2STe
400.80
295(2)
)
k (Å)
0.71073
0.71073
0.71073
Crystal system
Crystal size (mm3)
Space group
a (Å)
b (Å)
c (Å)
triclinic
triclinic
triclinic
0.75 Â 0.48 Â 0.29
0.47 Â 0.31 Â 0.21
0.81 Â 0.55 Â 0.35
ꢀ
ꢀ
ꢀ
P1
P1
P1
9.2522(4)
9.4617(3)
11.6605(4)
12.6839(5)
86.429(3)
68.636(3)
74.925(3)
1257.56(8)
4
8.9381(7)
12.0641(10)
14.4264(5)
91.802(5)
102.075(5)
100.610(7)
1491.21(18)
4
11.5073(4)
12.4557(6)
89.544(3)
70.200(4)
76.255(3)
1208.18(9)
4
2.494
9.376
832
a
(°)
b (°)
c
(°)
V (Å3)
Z
qcalc (Mg mÀ3
)
2.893
7.564
976
1.785
2.469
776
Absorption coefficient (mmÀ1
F(0 0 0)
)
h, k, l ranges collected
À13 ? 13
À13 ? 14
À17 ? 17
À18 ? 18
15 776
À13 ? 12
À19 ? 17
À22 ? 22
23 055
À16 ? 17
À18 ? 16
Reflection collected
14 921
Independent reflections (Rint
h range (°)
Completeness to hmax (%)
Absorption correction
Maximum, minimum transmission
Refinement method
)
7598 (0.0313)
4.77–32.60
97.9
8290 (0.0300)
5.04–32.81
98.7
semi-empirical from equivalents
1.00000, 0.21127
12 021 (0.0204)
5.17–35.01
99.0
analytical
0.473, 0.253
analytical
0.182, 0.028
full-matrix least-squares on F2
7598/292/295
1.061
Data/restraints/parameters
8290/320/287
1.028
12 021/0/313
1.052
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0618, wR2 = 0.1213
R1 = 0.1165, wR2 = 0.1348
1.110/À0.960
R1 = 0.0348, wR2 = 0.0831
R1 = 0.0496, wR2 = 0.0875
1.746/À1.683
R1 = 0.0531, wR2 = 0.1342
R1 = 0.0783, wR2 = 0.1497
1.963/À1.253
Largest diff peak/hole (e ÅÀ3
)

84
A.K.S. Chauhan et al. / Inorganica Chimica Acta 376 (2011) 80–86
Fig. 1. ORTEP view of the molecular structure common to 2b (X = Br) and {2c (X = I)} with 30% probability displacement ellipsoids. H atoms are omitted for clarity. Selected
interatomic distances (Å) and angles (°) for the two independent molecules of each: Te–C11 2.082(6), 2.118(8) {2.123(4), 2.090(4)}; Te–C21 2.11(1), 2.10(1) {2.107(3),
2.107(4)}; Te–X1 2.6755(9), 2.6076(11) {2.8401(5), 2.9320(4)}; Te–X2 2.6789(10), 2.7460(9) {3.0166(4), 2.9301(5)}; C11–Te–C21 92.5(5), 91.0(4) {94.9(1), 95.5(1)}; X1–Te–
X2 177.63(3), 175.87(3) {171.76(1), 175.69(1)}.
Fig. 2. ORTEP view of the molecular structure of 2e with 50% probability displacement ellipsoids. H atoms are omitted for clarity. Selected interatomic distances (Å) and
angles (°) for the two independent molecules: Te1–C1a 2.134(4), Te1–C10a 2.096(4), Te1–Cl11 2.507(2), Te1–Cl12 2.501(1), C1a–Te1–C10a 108.4(2), Cl11–Te1–Cl12
173.08(4); Te2–C1b 2.135(4), Te2–C10b 2.095(4), Te2–Cl21 2.511(2), Te2–Cl22 2.497(2), C1b–Te2–C10b 108.3(2), Cl21–Te2–Cl22 174.3(1).
Unlike telluride 2, which was previously shown to have no
intermolecular interactions less than 3.5 Å [5], the solid state
structures of 2b and 2c consist of a four molecule supramolecu-
lar self assembly through non-covalent TeÁ Á ÁX bonds. This results
in an interesting incomplete cubane framework with S2 molecu-
lar symmetry (Fig. 3). The two independent molecules in both 2b
and 2c are linked together into dimers by means of intermolec-
ular reciprocal TeÁ Á ÁX secondary bonding interactions. Pairs of
these dimers are further associated centrosymmetrically into a
tetrameric structure, in which each Te(IV) atom is six coordinate
and the two secondary bonded X ligands drawn from different
molecules are coplanar with its equatorial C–Te–C group. The
Te–X and TeÁ Á ÁX bond lengths differ significantly, spanning the
ranges 2.6076(8)–2.7460(7) and 3.5242(9)–3.5783(8) Å in 2b
and 2.8401(4)–3.0166(4) and 3.6308(4)–3.6673(4) Å in 2c.
Lengthening of the primary Te–X bonds with increasing coordi-
nation number of the halogen atom is also evident.
The interesting feature of such a supramolecular architecture,
which has also been observed earlier in case of other diaryltellurium
dihalides [19–23], is that the angles between adjacent Te–X/TeÁ Á ÁX
bonds around each Te atom are close to 90° (Table 3). It may be
substantiated that the lone pair of each 6-coordinate-14-electron
Te atom is redundant, as a result, the angle subtended by the
halo ligands held by means of secondary bonding interaction
at the central atom becomes even smaller compared to the
C–Te–C angle. However, the formation of analogous cubane-like

A.K.S. Chauhan et al. / Inorganica Chimica Acta 376 (2011) 80–86
85
Fig. 3. A zero-dimensional supramolecular tetrameric unit of 2c. Hydrogen atoms have been omitted for clarity. Symmetry operation: a = 1 À x, 1 À y, 2 À z.
4. Conclusion
Table 3
Interatomic distances (Å) and angles (°) in the tetrameric supramolecular structure of
2c.
Bis(2-thiophenyl)ditelluride, obtained conveniently from ele-
mental tellurium and Grignard reagent of 2-thiophenyl bromide,
has been employed to prepare 2-thiophenyltellurium(II, IV) deriv-
atives, Tpn2Te, TpnTeX3, Tpn2TeX2 and TpnArTeX2. 13C, and 125Te
NMR chemical shifts for all the compound and crystal data for
Tpn2TeBr2, Tpn2TeI2 and TpnMesTeCl2 are discussed. Electronic
and steric factors seem to influence the orientation of the planar
heteroaromatic rings in the solid state molecular geometry of these
compounds. The tetrameric supramolecular self assembly realized
via TeÁ Á ÁX interactions in the isomorphous compounds Tpn2TeX2
(X = Br, I) consists of an incomplete cubane framework in which
the lone pair on each Te atom appears to be redundant.
Te1–C11A
Te1–C21A
Te1–I1
Te1–I2
2.123(4)
2.107(3)
2.8401(4)
3.0166(4)
3.6501(4)
3.6607(4)
94.91(15)
88.62(1)
82.00(1)
94.63(11)
92.35(8)
93.08(9)
90.43(1)
83.60(1)
93.42(8)
92.27(9)
83.440(9)
90.08(1)
171.76(1)
175.37(8)
170.0(1)
Te2–C11B
Te2–C21B
Te2–I3
Te2–I4
2.091(3)
2.108(3)
2.9321(4)
2.9300(4)
3.6380(4)
3.6673(4)
95.52(14)
87.56(10)
93.50(1)
83.35(10)
91.03(7)
92.13(9)
84.82(1)
86.81(1)
92.61(8)
89.81(9)
91.42(1)
91.32(1)
175.69(1)
174.94(6)
178.43(7)
Te1Á Á ÁI3
Te2Á Á ÁI2
Te1Á Á ÁI4a
Te2Á Á ÁI2a
C11A–Te1–C21A
C21A–Te1–I3
I3–Te1–I4a
I4a–Te1–C11A
I1–Te1–C11A
I1–Te1–C21A
I1–Te1–I3
C11B–Te2–C21B
C21B–Te2–I2
I2–Te2–I2a
I2a–Te2–C11B
I3–Te2–C11B
I3–Te2–C21B
I3–Te2–I2
I1–Te1–I4a
I2–Te1–C11A
I2–Te1–C21A
I2–Te1–I3
I3–Te2–I2a
I4–Te2–C11B
I4–Te2–C21B
I4–Te2–I2
Acknowledgments
I2–Te1–I4a
I2–Te1–I1
I4–Te2–I2a
I4–Te2–I3
Financial assistance by the Department of Science and Technol-
ogy, Government of India, New Delhi, is gratefully acknowledged.
P.S. thanks Council of Scientific and Industrial Research (India)
for the award of Senior Research Fellowship.
I3–Te1–C11A
I2–Te2–C11B
I4a–Te1–C21A
I2a–Te2–C21B
Symmetry operation: a = 1 À x, 1 À y, 2 À z.
Appendix A. Supplementary material
supramolecular self assembly in the solid state of b,
c, and d poly-
morphs of tetrameric TeI4 or its adduct {(CH2)4TeI2ÁTeI4}2 has ear-
lier [24] been accounted for by the presence of ionic species viz.
(TeI3+)2(I–)2(TeI4)2 and {(CH2)4TeI+}2(TeI3+)2(I–)4.
The supramolecular architectures identified in the crystal lat-
tices of 2e and 2b (Figs. S1 and S2) together with the bond param-
eters in the tetrameric cluster of 2b (Table S1) are given as

86
A.K.S. Chauhan et al. / Inorganica Chimica Acta 376 (2011) 80–86
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