α-telluration of 2-acetylthiophene: Electronic influence of the heteroaromatic moiety on solid state structures

Article abstract of DOI:10.1016/j.jorganchem.2010.07.025

Room temperature oxidative addition of α-bromo-2-acetylthiophene to elemental tellurium and aryltellurium(II) bromide provides direct routes to (2-thiophenoylmethyl)tellurium(IV) dibromides, (2-(C₄H ₃S)COCH₂)₂TeBr₂ (1b) and 2-(C ₄H₃S)COCH₂ArTeBr₂ (Ar = 1-C ₁₀H₇, Npl, 2b; 2,4,6-Me₃C₆H ₂, Mes, 3b). The chloro analogues, 2-(C₄H ₃S)COCH₂ArTeCl₂ (Ar = Npl, 2a; Mes, 3a) were prepared by the condensation reaction of the parent methyl ketone with NplTeCl₃ or MesTeCl₃. Metathesis of these products with an alkali iodide affords the iodo analogues 1c, 2c and 3c. These diorganotellurium dihalides are reduced with aqueous bisulfite to diorganotellurides 1-3, which can be oxidized readily with dihalogens to the desired diorganotellurium(IV) dihalides. Compound 1 is a rare example of a symmetrical telluroether with C_sp3-Te-C_sp3 grouping that has been characterized by single-crystal diffraction techniques. Preference of the 2-thiophenoylmethyl ligand for small-bite (C, O) chelation over less strained (C, S) coordination is evident in the crystal structures of the Te(IV) compounds 1b, 2a, 2b and 3a. The unexpected transoidal orientation of the two acylmethyl ligands in the solid state molecular configuration of symmetrical diorganotellurium(IV) dibromide 1b appears to be a combined effect of electronic repulsion due to the thiophene moieties and steric repulsion of bromo ligands.

Full text of DOI:10.1016/j.jorganchem.2010.07.025

Journal of Organometallic Chemistry 695 (2010) 2532e2539
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
a-Telluration of 2-acetylthiophene: Electronic influence of the heteroaromatic
moiety on solid state structures
,
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:
Room temperature oxidative addition of
a
-bromo-2-acetylthiophene to elemental tellurium and aryl-
Received 23 June 2010
Received in revised form
16 July 2010
Accepted 27 July 2010
Available online 3 August 2010
tellurium(II) bromide provides direct routes to (2-thiophenoylmethyl)tellurium(IV) dibromides, (2-
(C4H3S)COCH2)2TeBr2 (1b) and 2-(C4H3S)COCH2ArTeBr2 (Ar ¼ 1-C10H7, Npl, 2b; 2,4,6-Me3C6H2, Mes, 3b).
The chloro analogues, 2-(C4H3S)COCH2ArTeCl2 (Ar ¼ Npl, 2a; Mes, 3a) were prepared by the conden-
sation reaction of the parent methyl ketone with NplTeCl3 or MesTeCl3. Metathesis of these products
with an alkali iodide affords the iodo analogues 1c, 2c and 3c. These diorganotellurium dihalides are
reduced with aqueous bisulfite to diorganotellurides 1e3, which can be oxidized readily with dihalogens
to the desired diorganotellurium(IV) dihalides. Compound 1 is a rare example of a symmetrical tellur-
oether with Csp3eTeeCsp3 grouping that has been characterized by single-crystal diffraction techniques.
Preference of the 2-thiophenoylmethyl ligand for small-bite (C, O) chelation over less strained (C, S)
coordination is evident in the crystal structures of the Te(IV) compounds 1b, 2a, 2b and 3a. The unex-
pected transoidal orientation of the two acylmethyl ligands in the solid state molecular configuration of
symmetrical diorganotellurium(IV) dibromide 1b appears to be a combined effect of electronic repulsion
due to the thiophene moieties and steric repulsion of bromo ligands.
Keywords:
Tellurium insertion
2-Acetylthiophene
Sterically hindered organotelluriums
Dialkyltelluroether
Intramolecular secondary bonding
interactions
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
eliminates 2 mol of HCl to produce organotellurium(IV) dichlorides.
However, organotellurium(IV) trichlorides were isolated in the
Functional group promoted metallation of organic substrates
makes available organolithiums that readily undergo the insertion
of elemental tellurium into the carbon-metal bond to afford lithium
arenetellurolates. This synthetic protocol is especially effective in
the ortho telluration of heteroaromatic substrates [1]. Lithium or
sodium arenetellurolates are very good nucleophilic species and
can be easily alkylated by alkyl halides to obtain alkylaryltellurides
[2]. However, the reaction of lithium 2-thiophenetellurolates with
acylmethyl halides results in reductive dehalogenation to give
parent ketones [3] instead of the expected acylmethyl(2-thio-
reaction of TeCl4 with 2,6-diacetylpyridine, 2-acetylcyclohexanone
or 3-acetyl-7-methoxycoumarin where dehydrochlorination was
limited to only 1 mol [14]. Although the condensation product of
TeCl4 with 2-acetylthiophene, the bis(2-thiophenoylmethyl)tellu-
rium dichloride has been obtained in poor yields [3,10,14] the
reaction product of TeCl4 with 2-acetylpyridine still remains
uncharacterized [14]. These observations highlight the substantial
role heteroaromatic moiety electronic factors play in the electro-
philic reactions of their acetyl derivatives.
A
simple and direct route to bis(acylmethyl)tellurium(IV)
phenyl)tellurides. Another strategy of
a
-telluration of acyl-
dibromides, practiced in our laboratory, involves oxidative insertion
of elemental tellurium into the CeBr bond of RCOCH2Br. In contin-
uation, we now describe the isolation and structural characteriza-
tion of (2-thiophenoylmethyl)tellurium(II and IV) derivatives which
have been obtained at ambient conditions by (i) oxidative addition
methanes is their electrophilic substitution reaction with TeCl4 or
ArTeCl3 [4e8]. The condensation reaction of TeCl4 with simple
arylmethyl ketones such as acetophenone, its ring substituted
derivatives [3,9e11] and substituted acetylacetones [12,13]
of a-bromo/iodo-2-acetylthiophenes to elemental tellurium and (ii)
electrophilic substitution of 2-acetylthiophene with the aryltellu-
rium trichlorides that bear a sterically cumbersome aryl ligand
bound to tellurium atom.
* Corresponding author.
E-mail address: akschauhan2003@yahoo.co.in (A.K.S. Chauhan).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.07.025

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2532e2539
2533
Table 1
2. Results and discussion
Important chemical shifts (in ppm) for thiophenoylmethyltellurium derivatives.
1H
13C
125Te
2.1. Synthesis
CH2
CH3
CH2
CH3
CO
Thermally labile a-bromo-2-acetylthiophene adds to elemental
1a
5.19
1b 5.32
4.30
5.60
2b 5.75
5.77
5.54 2.34 (p-Me)
2.79, 2.82 (o-Me)
3b 5.70 2.34 (p-Me)
2.75, 2.79 (o-Me)
5.73 2.32 (p-Me)
2.64 (o-Me)
56.9
54.8
51.2
65.6
64.0
184.2 751
184.4 686
186.0 602
183.9 764
184.0 697
tellurium at room temperature to afford (2-(C4H3S)COCH2)2TeBr2
and to ArTeBr (prepared in situ from Ar2Te2 and Br2; Ar ¼ Npl, Mes),
to give 2-(C4H3S)COCH2ArTeBr2. The chloro analogues, (2-(C4H3S)
COCH2)2TeCl2 and 2-(C4H3S)COCH2ArTeCl2, are obtained by elec-
trophilic substitution of the parent ketone with TeCl4 and ArTeCl3,
respectively. Iodo analogues are prepared either by oxidative
1c
2a
2c
3a
606, 984
62.2 21.0 (p-Me)
23.5, 24.1 (o-Me)
61.2 21.0 (p-Me)
23.3, 24.6 (o-Me)
58.9 21.0 (p-Me)
23.2, 25.7 (o-Me)
184.4 784
184.5 704
addition of a-iodo-2-acetylthiophene to tellurium powder to afford
1c or by metathesis of the bromo/chloro compounds (1b, 2a, 3a)
with alkali metal iodides. Reduction of these dihalides with
Na2S2O5 affords the corresponding tellurides, (1, 2, 3) which are
readily oxidized with dihalogens to afford the corresponding dio-
rganotellurium(IV) dihalides (Scheme 1).
3c
590, 885
190.8 559
1
2
3
4.18
4.17
10.1
3.94 2.29 (p-Me)
2.51(o-Me)
2.2. Spectroscopic studies
and 1b are at lower wave number than that for the parent ketone,
2-acetylthiophene.
Important NMR chemical shifts are listed in Table 1 for critical
comparison. Methylene protons, appearing at w4.1 ppm in the 1H
NMR spectra of Te(II) derivatives 1e3, are appreciably shielded
All dihalides (1ae1c, 2ae2c and 3ae3c) and tellurides 1 and 3
are sharp melting colorless to orange solids, soluble in chloroform
and dichloromethane. Dialkyltelluride 1 and the Te(IV) diiodides
(1c, 2c and 3c) are stable for weeks only when stored at low
temperature (ꢀ10 ꢁC), while the other new organotellurium
when compared to their Te(IV) analogues (d 4.3e5.8 ppm). Protons
derivatives are fairly stable at ambient conditions. The
n(CO)
absorptions appearing at w1630 cmꢀ1 in the infrared spectra of 1a
of the thiophene moiety appear in the aromatic region, along with
Scheme 1.

2534
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2532e2539
Fig. 1. Molecular structure of 1. Selected interatomic distances (Å) and angles (◦): TeeC1a 2.170(2), TeeC1b 2.164(2), Te/O1a 3.588(2), Te/O1b 3.609(2), O1a/S1 3.000(2),
O1b/S2 2.93(2), C1aeTeeC1b 94.66(8), O1a/TeeC1b 66.96(6), O1b/TeeC1a 108.06(6), O1a/S1eC6a 142.60(9), O1b/S2eC6b 144.29(9).
the ring protons of the naphthyl and the mesityl groups. Appear-
ance of separate signals (1:1) for the ortho methyls of the mesityl
group in the 1H NMR spectra of 3ae3c is indicative of restricted
rotation of the benzene ring about the TeeC(Mes) bond. The 13C
NMR chemical shifts for the carbonyl carbon appear in the range
184e191 ppm and the methylene carbon between 56 and 66 ppm
for Te(IV) derivatives and at 10.1 ppm in case of 1. All the
symmetrical diorgantellurium derivatives (1, 1a, 1b, 1c) give rise to
a single 125Te NMR resonance indicating the presence of only one Te
containing species in their solutions. While the chemical shift for
ligand, adopts planar cis geometry (see Scheme 1) invariably among
the molecular structures of all the organotelluriums crystallo-
graphically characterized in the present study. The near linearity
attained by the O/SdCtrans triad (: OdSdCtrans ranges from 141.9
(1)ꢁ in 3a to 144.3(1)ꢁ in 1) makes the overlap of vacant
s*(SdCtrans) molecular orbital with filled p-orbital on the O atom
feasible. The observed shorter d(S, O) compared to S rvdw(S, O),
3.32 Å, appears to be a manifestation of intramolecular secondary
bonding interaction that stabilizes the observed cis conformation of
the bifunctional organic ligand.
telluride 1 (
derivatives are consistent with the electronegativity of the halo
ligands (
751 (1a), 686 (1b), 602 ppm (1c)). Two 125Te chemical
shifts are observed for asymmetric diorganotellurium(IV) diiodides
2c and 3c, indicating that they are not as stable to dis-
propotionation, at least in solution, as their chloro or bromo
analogues.
d
559 ppm) is towards high field, those for the Te(IV)
The central Te(IV) atom among 1b, 2a, 2b and 3a, imparts
trigonal bipyramidal primary geometry with expected XdTedX
and CeTeeC angular distortions due to its lone pair. However, the
sterically demanding 1-naphthyl and mesityl ligands in 2a, 2b and
3a, appreciably widen the CeTeeC angle in comparison to 1b (see
Table 2). Among the molecular structures of unsymmetrical dio-
rganotellurium(IV) dihalides 2a, 2b and 3a, the carbonyl O atom of
the sole functionalized ligand is involved simultaneously in the
intramolecular secondary bonding interaction to either of its
heavier congeners. The observed internuclear distance between O
and Te atoms, which is shorter than the sum of their van der Waals
radii [d(Te, O) ¼ 2.983(3) (2a), 2.982(4) (2b), 2.862(2) Å (3a); S
rvdw(Te, O) ¼ 3.58 Å] and near linearity of the O/TedCtrans triad
(: OdTedCtrans measures 150.3(1)ꢁ, 149.6(2)ꢁ and 162.3(1)ꢁ in 2a,
d
2.3. Crystal structures
The molecular structures of 1, 1b, 2a, 2b and 3a are shown in
Figs. 1e5 with selected bond parameters collected in the caption to
each figure. Asymmetric units in each case consist of one molecule.
Interestingly, 2-thiophenoylmethyl, the functionalized organic
Fig. 2. Molecular structure of 1b. Selected interatomic distances (Å) and angles (◦): TeeC1a 2.133(4), TeeC1b 2.157(5), TeeBr1 2.7143(6), TeeBr2 2.6196(8), Te/O1a 2.880(4),
Te/O1b 3.553(4), O1a/S1a 3.001(3), O1b/S1ba 2.938(6), C1aeTeeC1b 94.9(2), Br1eTeeBr2 177.50(2), O1a/TeeC1b 148.1(2), O1b/TeeC1a 60.1(1), O1a/S1aeC6a 142.1(2),
O1b/S1baeC6ba 143.5(3).

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2532e2539
2535
Fig. 3. Molecular structure of 2a. Selected interatomic distances (Å) and angles (◦): TeeC1a 2.126(3), TeeC1b 2.124(3), TeeCl1 2.545(1), TeeCl2 2.477(1), Te/O1a 2.984(3), O1a/S1a
2.995(3), C1aeTeeC1b 98.1(1), Cl1eTeeCl2 169.93(4), O1a/TeeC1b 150.2(1), O1a/S1aeC6a 143.9(2).
2b and 3a respectively) substantiate the presence of attractive 1,4-
Te/O interaction. This interaction brings the O atom in to the
equatorial C1AdTedC1B plane, reduces the tetrahedral angle
TedC1AdC2A to 106.3ꢁ, 106.5ꢁ and 105.1ꢁ in 2a, 2b and 3a
respectively and marginally the trans TedC(aryl) bond length [d
(TedC(aryl)) ¼ 2.124(3) (2a), 2.129(5) (2b), 2.131(2) Å (3a); cf.
2.103 Å in Npl2TeCl2 [15] and 2.100(2) Å in (2,6-(MeO)2C6H3)2TeCl2
[16]. The functionalized ligand thus prefers (C, O), rather than (C, S),
mode of chelation, though the latter, involving its trans confor-
mation, would have resulted in the formation of a less strained five-
member intramolecular ring.
In the crystal structure of symmetrically functionalized dio-
rganotellurium(IV) 1b (Fig. 2), one of the thiophene rings is two-
fold disordered with 70:30 occupancies. Interestingly, the observed
molecular configuration is unique. Among the molecular structures
of bis(acylmethyl/amidomethyl)tellurium(IV) dihalides [(RCOCH2)2
TeX2, R ¼ Me, Et, t-Bu, 4-YC6H4, NH2, NEt2, NMePh and X ¼ Cl, Br, I]
described earlier by us [7,8,17e20], both the carbonyl functional-
ized organic ligands exhibit (C, O) chelating behavior and impart
six-coordination to the central Te atom. The skeletal frameworks of
the organic ligands, TedCdC(O)dC/N, in these compounds are
invariably almost coplanar, with the equatorial CeTeeC plane and
the cisoidal orientation of the ligands imparting a butterfly shape
C2v molecular symmetry. In the anticipated molecular structure of
1b (see Scheme 1), by analogy to the structure of its chloro
analogue, (2-(C4H3S)COCH2)2TeCl2 [21], the cisoidal 2-thiophenoyl
moieties would bring five electron-rich chalcogen atoms in the
domain of the lone pair of the central atom. However, the steric and
electronic repulsions appear to predominate the subtle 1,4-Te/O
secondary bonding interactions. As a consequence, while one of the
organic ligands retains its (C, O) chelating mode of coordination in
the observed structure of 1b, the free rotation about the TedC bond
allows the other to move its carbonyl O atom out of the equatorial
plane (to an almost transoidal conformation) and close to the van
der Waals distance from the Te(IV) [d(Te, O1B) ¼ 3.55 Å]. The
intraligand S/O secondary bonding interaction and hence planar
cis conformation of this monodentate organic ligand is, however,
retained in the molecule of 1b and the five-coordinate central Te
atom becomes accessible for intermolecular Te/X secondary
bonding interactions. The centrosymmetric zero-dimensional
dimeric units that are realized via reciprocatory Te/Br1 interac-
tions self-assemble, in the crystal lattice of 1b, by means of
CdH1BA/O1A H-bonding interactions into one-dimensional
supramolecular arrays (Figure S1).
Among the diorganotellurides, 1 and 3 were obtained in the
crystalline state and single-crystal data for the symmetric tellur-
oether (1) were collected. Absence of axial halo ligands in it seems to
provide steric freedom to the 2-thiophenyl moieties. Free rotation
about the TedC bonds allows the organic ligands to adopt transoidal
orientation with minimum electronic repulsion, at least in the solid
state. The interplanar angles between the equatorial CeTeeC plane
and the mean planes comprising of skeletal atoms of the organic
ligands are 82.42(5)ꢁ and 72.46(6)ꢁ and the internuclear distances
between the Te(II) and carbonyl O atoms [d(Te, O) ¼ 3.588(2)Å and
Fig. 4. Molecular structure of 2b. Selected interatomic distances (Å) and angles (◦): TeeC1a 2.129(5), TeeC1b 2.133(4), TeeBr1 2.6361(5), TeeBr2 2.7071(6), Te/O1b 2.982(4),
O1b/S1b 2.984(5), C1aeTeeC1b 98.0(2), Br1eTeeBr2 171.14(2), O1b/TeeC1a 149.6(2), O1b/S1beC6b 144.0(3).

2536
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2532e2539
Fig. 5. Molecular structure of 3a. Selected interatomic distances (Å) and angles (◦): TeeC1a 2.131(2), TeeC1b 2.131(2), TeeCl1 2.4919(6), TeeCl2 2.5127(6), Te/O1b 2.862(2),
O1b/S1b 3.000(2), C1aeTeeC1b 108.49(8), Cl1eTeeCl2 173.32(2), O1b/TeeC1a 162.29(6), O1b/S1beC6b 141.9(1).
3.609(2) Å] are comparable to S rvdw(Te, O). Thus, the molecular
structure of 1 is devoid of intramolecular Te/O attractive interac-
tions that are reported to be present in analogous compounds, (4-
MeC6H4COCH2)2Te and (2,4,6-Me3C6H2COCH2)2Te [19,22]. Instead,
reciprocatory intermolecular Te/O secondary bonding interactions
that give rise to centrosymmetric zero-dimensional supramolecular
units in its crystal packing (Figure S2) may be substantiated from the
d(Te, O1B) of 3.485(2) Å and : O1BdTedCtrans of 151.87ꢁ(7).
trichloridewere prepared by the chlorination of their corresponding
ditellurides with SO2Cl2. IR spectra were recorded as KBr pellets
using a PerkineElmer RX1 spectrometer. 1H NMR spectra 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 recorded in CDCl3 on a JEOL
Eclipse Plus 400 NMR spectrometer, using Me4Si and Me2Te as
internal standards. Microanalyses were carried out using a Carlo
Erba 1108 analyzer. Tellurium was estimated volumetrically.
2.4. Conclusion
3.2. Syntheses
Oxidative addition of the aroylmethyl bromide to Te(0) and Te
(II) provides a direct route to (2-thiophenoylmethyl)tellurium(IV)
dibromides, which are readily reduced to the corresponding tel-
luroethers. As a consequence of secondary bonding interaction
between the lighter chalcogen atoms, the planar functionalized
organic ligand invariably adopts ciseS, O configuration among all
the Te(IV) and Te(II) derivatives. The (C, O) mode of chelation of the
ligand caused by 1,4-Te/O secondary bonding interaction is
preferred to the (C, S) mode. Among (2-thiophenoylmethyl)aryl-
tellurium(IV) dihalides, the central Te atom is five-coordinate even
in the presence of a bulky aryl ligand. Interestingly, the anticipated
six-coordination of Te atom in bis(2-thiophenoylmethyl)tellurium
(IV) dibromide is not realized, possibly as a combined effect of
electronic repulsion due to the thiophene moieties and steric hin-
derance of bromo ligands.
3.2.1. Syntheses of symmetrical diorganotellurium derivatives
Compound 1b: Freshly ground tellurium powder (0.50 g,
3.94 mmol) and a-bromoacetylthiophene (1.0 mL, 7.87 mmol) were
stirred together at room temperature for 24 h. A thick paste was
formed that was washed with diethyl ether and extracted with
dichloromethane (200 mL). The extract was passed through a small
silica column and the solvent reduced to about 5 mL by distillation.
Addition of hexane precipitated a colorless solid that was recrys-
tallized from dichloromethane to give 1b as pale yellow rectangular
crystals. Yield: 1.1
g
(52%). M.p.: 185 ꢁC. Anal. Calc. for
C12H10O2S2TeBr2 (537.74): C, 26.80; H, 1.87; Te, 23.73. Found: C,
26.80; H, 2.00; Te, 23.85. IR (cmꢀ1): 1630.8 (
n
C ¼ O). 1H NMR:
d 5.32
(s, 2H, CH2), 7.21e7.24 (t, 1H, ring proton), 7.83e7.85 (d, 2H, ring
protons) ppm. 13C{1H} NMR:
carbons), 184.4 (CO) ppm. 125Te{1H} NMR:
Compound 1c: solution of 1b (0.27 g, 0.50 mmol) in
d
54.8 (CH2), 128.8, 135.1, 137.0 (ring
686 ppm.
d
A
3. Experimental
dichloromethane (50 mL) was stirred with KI (0.33 g, 2.0 mmol) for
5 h. Potassium halides were removed by filtration and excess
solvent was removed by distillation. An orange solid settled on
cooling and was recrystallized from chloroform/hexane. Yield:
0.22 g (69% with respect to 1b). M.p.: 168 ꢁC. Anal. Calc. for
C12H10O2S2TeI2 (631.75): C, 22.81; H, 1.60; Te, 20.20. Found: C,
3.1. General procedures
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, with
a-bromoace-
22.62; H, 1.59; Te, 20.10; 1H NMR:
1H, ring proton), 7.69e7.70 (d, 1H, ring proton), 7.79e7.81 (d, 1H,
ring proton) ppm. 13C{1H} NMR:
51.2 (CH2), 128.4, 133.4, 135.1,
140.4 (ring carbons), 186.0 (CO) ppm. 125Te{1H} NMR:
602 ppm.
Alternatively, 1c was also obtained when tellurium powder
(0.13, 1.0 mmol) and -iodoacetylthiophene [prepared by stirring
-bromoacetylthiophene (0.26 mL, 2.0 mmol) with KI (0.35 g,
d 4.30 (s, 2H, CH2), 7.15e7.18 (t,
tylthiophene being obtained as pale yellow lachrymatory oil by
bromination of 2-acetylthiophene (Merck, Germany) in glacial
acetic acid. 1-Naphthyltellurium trichloride and mesityltellurium
d
d
a
Table 2
Important bond angles and distances (ꢁ, Å) in compounds 1, 1b, 2a, 2b & 3a.
a
2.1 mmol) in 1 mL acetone for 1 h were stirred together at room
temperature for 2 h. An orange paste formed and was extracted
with dichloromethane (20 mL), passed through a small silica
column and the solvent reduced to 2 mL by distillation. Addition of
petroleum ether (40e60) and cooling afforded 1c as an orange
solid. Yield: 0.35 g (56% with respect to Te). M.p.: 168 ꢁC.
CeTeeC
TeeCeC
O/TeeCtrans
Te/O
TeeC(Ar)
1
94.7(1)
94.9(2)
98.2(1)
98.0(2)
108.5(1)
110.5(2)
105.9(3)
106.3(2)
106.5(3)
105.1(1)
151.9(1)
148.1(2)
150.3(1)
149.6(2)
162.3(1)
3.485(2)
2.880(4)
2.983(3)
2.982(4)
2.862(2)
1b
2a
2b
3a
2.124(3)
2.129(5)
2.131(2)

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2532e2539
2537
Compound 1:
A
solution of 1b (0.27 g, 0.50 mmol) in
(0.09 g, 0.47 mmol) for 20 min. The yellow organic layer was
separated, washed with water (4 ꢂ 20 mL) and passed through
anhydrous Na2SO4. The solvent was removed completely under
dichloromethane (10 mL) and diethyl ether (50 mL) was stirred
with an aqueous solution of Na2S2O5 (0.10 g, 0.53 mmol) for 1 h at
0
ꢁC. The yellow organic layer was separated, washed with water
vacuum to afford 2 as red oil. Yield: 0.09 g (47%). 1H NMR:
2H, CH2), 7.08e8.29 (m, 10H, aromatic protons) ppm.
d 4.17 (s,
(4 ꢂ 20 mL), and passed through anhydrous Na2SO4. The solvent
was reduced under vacuum at room temperature to about 2 mL,
3e4 drops of dichloromethane were added and the solution was
kept in a deep freezer, affording yellow hexagonal crystals of 1.
Yield: 0.13 g (66%). M.p.: 85 ꢁC (Ref. [3] 93e94 ꢁC). Anal. Calc. for
C12H10O2S2Te (377.94): C, 38.14; H, 2.67; Te, 33.76. Found: C,
Compound 3: A solution of 3a (0.22 g, 0.50 mmol) in dichloro-
methane (5 mL) and diethyl ether w50 mL was shaken with an
aqueous solution of Na2S2O5 (0.09 g, 0.47 mmol) for 30 min. The
yellow organic layer was separated, washed with water (4 ꢂ 20 mL)
and passed through anhydrous Na2SO4. The resulting solution was
reduced to about 2 mL, diluted with hexane (5 mL) and the solution
kept in a deep freezer. The resulting yellow crystalline solid was
recrystallized from diethyl ether to give 3 as yellow rectangular
crystals. Yield: 0.08 g (43%). M.p.: 72 ꢁC. Anal. Calc. for C15H16OSTe
(371.95): C, 48.44; H, 4.34; Te, 34.31. Found: C, 48.24; H, 4.30; Te,
38.24; H, 2.70; Te, 33.85. 1H NMR:
ring proton), 7.65e7.67 (d, 1H, ring proton), 7.80 (s, 1H, ring
proton) ppm. 13C{1H} NMR:
10.1 (CH2), 128.3, 132.9, 134.4, 142.2
(ring carbons), 190.8 (CO) ppm. 125Te{1H} NMR:
559 ppm.
d 4.18 (s, 2H, CH2), 7.15 (s, 1H,
d
d
Compound 1a: Addition of a solution of SO2Cl2 (0.12 mL,
1.5 mmol) in dichloromethane (5 mL) to a cooled light yellow
solution of 1 (0.19 g, 0.50 mmol) in the same solvent (20 mL)
resulted in the precipitation of 1a as a white solid that was
collected by filtration. Recrystallization from dichloromethane
gave 1a as white needles. Yield: 0.16 g (73% with respect to 1).
M.p.: 180 ꢁC dec (Ref. [3] 180e182 ꢁC dec). IR (cmꢀ1): 1629.1
34.65. 1H NMR:
d 2.29 (s, 3H, p-Me), 2.51 (s, 6H, o-Me), 3.94 (s, 2H,
CH2), 6.88e7.56 (m, 5H, aromatic protons) ppm.
3.2.4. Oxidative addition reactions of 2, 3 with dihalogens
Compound 2b: Bromine (0.03 mL, 0.50 mmol) in hexane was
added dropwise at room temperature to a stirred solution of 2
(0.19 g, 0.50 mmol) in the same solvent (w10 mL). A yellow solid
began to separate instantly and the mixture was stirred for another
15 min to complete the reaction. The separated solid was dissolved
in dichloromethane and the solution passed through a short silica
column. Addition of petroleum ether (60e80) to the concentrated
solution afforded 2b as yellow crystals. Yield: 0.25 g (94%). M.p.:
165 ꢁC. Anal. Calc. for C16H12OSTeBr2 (539.74): C, 35.60; H, 2.24; Te,
(n
C ¼ O). 1H NMR:
d
5.19 (s, 2H, CH2), 7.23 (s, 1H, ring proton),
56.9 (CH2),
7.83e7.84 (d, 2H, ring protons) ppm. 13C{1H} NMR:
d
128.8, 135.1, 136.9, 140.9 (ring carbons), 184.2 (CO) ppm. 125Te{1H}
NMR: 751 ppm.
d
Compound 1a was also prepared by condensation of TeCl4
(0.54 g, 2.0 mmol) with 2-acetylthiophene (0.54 mL, 5.0 mmol) in
refluxing chloroform (10 mL) for 4 h. The color of the solution
changed from yellow to black as HCl evolved. Chloroform (20 mL)
was added and the solution passed through a small silica column.
Removal of excess solvent followed by cooling gave 1a as colorless
solid which was recrystallized from dichloromethane. Yield: 0.28 g
(32%). M.p.: 180 ꢁC dec.
23.64. Found: C, 34.90; H, 2.20; Te, 23.80. 1H NMR:
CH2), 7.63e8.27 (m, 10H, aromatic protons) ppm. 13C{1H} NMR:
64.0 (CH2), 126.6, 126.8, 127.4, 128.2, 128.8, 129.5, 131.8, 132.7,
133.0, 133.4, 134.3, 135.3, 137.1, 140.2 (aromatic carbons), 184.0 (CO)
ppm. 125Te{1H} NMR:
697 ppm.
d 5.75 (s, 2H,
d
d
Likewise, 3b was obtained as yellow crystals from 3 (0.19 g,
0.50 mmol) and Br2 (0.03 mL, 0.50 mmol). Yield: 0.23 g (87%). M.p.:
165 ꢁC. Anal. Calc. for C15H16OSTeBr2 (531.76): C, 33.88; H, 3.03; Te,
3.2.2. Synthesis of unsymmetrical diorganotellurium dichlorides
Compound 2a: A mixture of 1-naphthyltellurium trichloride
(0.18 g, 0.50 mmol) and two-fold excess of 2-acetylthiophene
(0.11 mL, 1.0 mmol) was stirred together at room temperature
under a flow of dry nitrogen for 12 h. The resulting paste was
washed with cold diethyl ether (5 ꢂ 10 mL), dissolved in
dichloromethane (20 mL) and passed through a short silica column.
The solvent was reduced to 10 mL and petroleum ether (40e60)
added to afford 2a as a cream colored solid that was recrystallized
from dichloromethane. Yield: 0.16 g (69%). M.p.: 168 ꢁC. Anal. Calc.
for C16H12OSTeCl2 (450.84): C, 42.63; H, 2.68; Te, 28.30. Found: C,
24.00. Found: C, 33.80; H, 3.12; Te, 24.10. 1H NMR:
d 2.34 (s, 3H, p-
Me), 2.75 (s, 3H, o-Me), 2.79 (s, 3H, o-Me), 5.70 (s, 2H, CH2), 6.98 (s,
1H, m-H mesityl ring), 7.06 (s, 1H, m-H mesityl ring), 7.22 (t, 1H,
thiophene ring), 7. 83, 7.85 (d, 1H, thiophene ring), 7.86, 7.87 (d, 1H,
thiophene ring) ppm. 13C{1H} NMR:
d 21.0 (p-Me), 23.3 (o-Me), 24.6
(o-Me), 61.2 (CH2), 128.8, 130.5, 131.5, 131.6, 135.0, 136.9, 139.6,
140.4, 141.2, 142.3 (aromatic carbons), 184.5 (CO) ppm. 125Te{1H}
NMR:
d 704 ppm.
42.67; H, 3.00; Te, 28.40. 1H NMR:
thiophene ring), 7.62e8.28 (m, 9H, aromatic protons) ppm. 13C{1H}
NMR: 65.6 (CH2), 126.4, 126.8, 127.3, 128.2, 128.8, 129.5, 131.9,
132.7, 132.8, 133.4, 134.3, 135.2, 137.0, 140.3 (aromatic carbons),
183.9 (CO) ppm. 125Te{1H} NMR:
764 ppm.
d
5.60 (s, 2H, CH2), 7.24 (t, 1H,
3.2.5. Metathetical reactions of 2a, 3a to 2c, 3c
Compound 2c: solution of 2a (0.23 g, 0.50 mmol) in
A
d
dichloromethane (30 mL) was stirred with KI (0.17 g, 1.0 mmol) for
3 h. The potassium halides were removed by filtration. Concen-
tration of the filtrate and addition of petroleum ether (40e60)
afforded orange 2c. Use of NaI gave 2c in comparable yield. Yield:
0.23 g (71%). M.p.: 156 ꢁC. Anal. Calc. for C16H12OSTeI2 (633.74): C,
30.32; H, 1.91; Te, 20.13. Found: C, 30.10; H, 1.98; Te, 20.18. 1H NMR:
d
Compound 3a was prepared similarly from mesityltellurium
trichloride (0.18 g, 0.50 mmol) and 2-acetylthiophene (0.11 mL,
1.0 mmol). Yield: 0.15 g (68%). M.p.: 152 ꢁC. Anal. Calc. for
C15H16OSTeCl2 (442.86): C, 40.68; H, 3.64; Te, 28.81. Found: C,
d
5.77 (s, 2H, CH2), 7.1e8.5 (m, 10H, aromatic protons) ppm. 125Te
40.57; H, 3.77; Te, 28.60. 1H NMR:
d
2.34 (s, 3H, p-Me), 2.79, 2.82
{1H} NMR:
d
606, 984 (0.75:0.25) ppm.
(2s, 6H, o-Me), 5.54 (s, 2H, CH2), 7.00 (s, 1H, m-H mesityl ring), 7.07
(s, 1H, m-H mesityl ring), 7.22 (t, 1H, thiophene ring), 7. 83e7.87 (m,
Compound 3c was prepared in a way similar by metathesis of 3a
(0.22 g, 0.50 mmol) with NaI or KI (1.0 mmol) as orange crystals.
Yield: 0.19 g (64%). M.p.: 98 ꢁC. Anal. Calc. for C15H16OSTeI2
(625.76): C, 28.79; H, 2.58; Te, 20.39. Found: C, 28.78; H, 2.60; Te,
2H, thiophene ring) ppm. 13C{1H} NMR:
d 21.0 (p-Me), 23.5 (o-Me),
24.1 (o-Me), 62.2 (CH2), 128.8, 130.4, 131.6, 134.8, 134.9, 136.8, 140.0,
140.6, 141.0, 142.3 (aromatic carbons), 184.4 (CO) ppm. 125Te{1H}
20.38; 1H NMR:
d 2.32 (s, 3H, p-Me), 2.64 (s, 6H, o-Me), 5.73 (s, 2H,
NMR:
d
784 ppm.
CH2), 6.93(s, 1H, m-H mesityl ring), 7.02 (s, 1H, m-H mesityl ring),
7.22 (s, 1H, thiophene ring), 7.82 (s, 2H, thiophene ring) ppm. 13C
3.2.3. Reduction of 2a, 3a to 2, 3
Compound 2: A solution of 2a (0.23 g, 0.50 mmol) in dichloro-
methane (20 mL) was shaken with an aqueous solution of Na2S2O5
{1H} NMR:
d
21.0 (p-Me), 23.2 (o-Me), 25.7 (o-Me), 58.9 (CH2), 127.2,
128.4, 130.7, 133.7, 133.4, 135.0, 136.9, 140.3, 142.1, 147.10 (aromatic
carbons) ppm. 125Te{1H} NMR:
590, 885(1:1) ppm.
d

2538
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2532e2539
Table 3
Crystal data and structure refinement details of 1, 1b, 2a, 2b and 3a.
1
1b
2a
2b
3a
empirical formula
formula mass
C12H10O2S2Te
377.92
C12H10Br2O2S2Te
537.74
C16H12Cl2OSTe
450.82
C16H12Br2OSTe
539.74
C15H16Cl2OSTe
442.84
(g molꢀ1
)
temp (K)
110(2)
295(2)
295(2)
295(2)
295(2)
wavelength,
cryst syst
l
(Å)
0.71073
0.71073
Triclinic
0.71073
Monoclinic
0.51 ꢂ 0.47 ꢂ 0.36
P 1 21/n 1
9.5437(2)
13.5609(3)
13.0199(3)
90
107.763(3)
90
1604.72(6)
4
0.71073
0.71073
Monoclinic
0.56 ꢂ 0.21 ꢂ 0.18
P 1 21/c 1
8.8076(2)
13.1440(3)
15.0915(4)
90
101.641(2)
90
1711.17(7)
4
Monoclinic
0.48 ꢂ 0.43 ꢂ 0.18
P 1 21/c 1
11.4870(3)
7.8833(3)
14.7573(4)
90
106.206(3)
90
1283.26(7)
4
Monoclinic
0.51 ꢂ 0.42 ꢂ 0.35
P 1 21/n 1
9.6524(4)
13.5973(8)
13.3312(6)
90
108.220(4)
90
1661.95(14)
4
cryst size (mm3)
space group
a (Å)
0.88 ꢂ 0.57 ꢂ 0.31
P ꢀ1
7.1593(4)
9.7490(5)
12.0975(6)
109.268(4)
96.401(4)
94.559(4)
785.98(7)
2
b (Å)
c (Å)
a
b
G
(deg)
(deg)
(deg)
V (Å3)
Z
rcalcd (Mg mꢀ3
)
1.956
2.629
728
2.272
7.235
504
1.866
2.311
872
2.157
6.719
1016
1.719
2.165
864
abs coeff (mmꢀ1
F(000)
)
index ranges
ꢀ17 ꢃ h ꢃ 15
ꢀ9 ꢃ k ꢃ 11
ꢀ16 ꢃ l ꢃ 22
8934
ꢀ10 ꢃ h ꢃ 10
ꢀ14 ꢃ k ꢃ 10
ꢀ17 ꢃ l ꢃ 18
9461
ꢀ14 ꢃ h ꢃ 14
ꢀ20 ꢃ k ꢃ 19
ꢀ19 ꢃ l ꢃ 19
16172
ꢀ14 ꢃ h ꢃ 14
ꢀ12 ꢃ k ꢃ 19
ꢀ20 ꢃ l ꢃ 16
13556
ꢀ12 ꢃ h ꢃ 7
ꢀ18 ꢃ k ꢃ 19
ꢀ18 ꢃ l ꢃ 22
14373
no. of rflns collected
no. of indep rflns
4234 (R(int) ¼ 0.0279)
5040
5418
5469
5678
(R(int) ¼ 0.0519)
(R(int) ¼ 0.0265)
(R(int) ¼ 0.0416)
(R(int) ¼ 0.0238)
completeness to
qmax (%)
99.3
98.4
99.3
99.0
99.1
abs cor
Semi-empirical from
equivalents
Analytical
Semi-empirical from
equivalents
Semi-empirical from
equivalents
Semi-empirical from
equivalents
max, min transmission
refinement method
1.00000, 0.38285
Full-matrix least-
squares on F2
0.174, 0.047
1.00000, 0.82083
1.00000, 0.12410
1.00000, 0.42309
no. of data/restraints/
params
4234/0/154
5040/0/188
5418/0/190
5469/0/180
5678/0/185
goodness of fit on F2
0.976
0.942
1.076
0.951
1.017
final R indices (I > 2
R indices (all data)
s
(I))
R1 ¼ 0.0267,
wR2 ¼ 0.0577
R1 ¼ 0.0410
wR2 ¼ 0.0605
0.658/ꢀ0.776
R1 ¼ 0.0485,
wR2 ¼ 0.1051
R1 ¼ 0.0908
wR2 ¼ 0.1164
1.361/e0.974
R1 ¼ 0.0353,
wR2 ¼ 0.0966
R1 ¼ 0.0570
wR2 ¼ 0.1021
1.122/e1.048
R1 ¼ 0.0448,
wR2 ¼ 0.1057
R1 ¼ 0.0833
wR2 ¼ 0.1138
1.376/e1.260
R1 ¼ 0.0313,
wR2 ¼ 0.0652
R1 ¼ 0.0524
wR2 ¼ 0.0700
0.595/e0.504
largest diff peak/hole
(e Åꢀ3
extinction coefficient
)
0.0072(9)
0.0034(4)
3.2.6. Alternative Procedures for synthesis of 2b and 3b
To a solution of ArTeBr [prepared in situ by mixing dichloro-
methane solutions of Npl2Te2 (0.51 g, 1.0 mmol) or Mes2Te2 (0.49 g,
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 model
and were refined isotropically. Crystal data and structure refine-
ment details are given in Table 3. ORTEP views of the molecular
structures are depicted in Figs. 1e5, showing 30% (1b, 2a, 2b, 3a)
and 50% (1) probability displacement ellipsoids, omitting H atoms
for clarity, and captioned with the geometrical parameters relevant
to the primary geometry.
1.0 mmol) and Br2 (0.05 mL, 1.0 mmol) at room temperature], a-
bromoacetylthiophene (0.25 mL, 2.0 mmol) was added at room
temperature under stirring. The reaction mixture was stirred for
24 h at room temperature and filtered to remove a black residue.
The dark brown filtrate was passed through a small silica column,
concentrated and an equal volume of petroleum ether (60e80)
added. Yellow crystals separated on overnight cooling in a refrig-
erator. Yield: 2b, 0.67 g (60%); 3b 0.53 g (50%).
Acknowledgments
3.2.7. Crystallography
Single crystals suitable for X-ray crystallography were grown by
slow evaporation of dichloromethane solutions of 1b, 2a, 2b and 3a.
In case of the telluride 1, cooling (ꢀ10 ꢁC) of its solution in a mixture
of dichloromethane/diethylether (1:10) resulted in the desired
crystals. Intensity data were collected on an Oxford Diffraction
Financial assistance by the Department of Science and
Technology, Government of India, New Delhi, is gratefully
acknowledged.
Gemini CCD diffractometer with graphite-monochromated Mo-K
a
Appendix A. Supplementary material
(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.,
Version 1.171.33.34d program. The structures were solved by direct
methods and difference Fourier synthesis using SHELXS-97 and
ORTEP figures generated using the program WinGX 2002 [23,24].
CCDC 780935, 780936, 780937, 780938, and 780939, contain
the supplementary crystallographic data for 1, 1b, 2a, 2b, and 3a,
respectively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2532e2539
2539
[11] K.K. Verma, S. Garg, Synth. React. Inorg. Met.-Org. Chem. 24 (1994) 647,
1631.
[12] J.C. Dewan, J. Silver, J. Chem. Soc. Dalton (1977) 644e647 and references
therein.
[13] C.L. Raston, R.J. Secomb, A.H. White, J. Chem. Soc. Dalton (1976) 2307e2310.
[14] H.J. Gysling, H.R. Luss, S.A. Gardner, J. Organomet. Chem 184 (1980) 417e431.
[15] J. Farran, A. Alvarez-Lorena, J.F. Pinella, G. Germain, L. Torres-Castellanos,
Z. Kristallogr. 210 (1995) 65.
The centrosymmetric dimeric supramolecular units identified in
the crystal lattice of 1b and 1 (Figures S1 and S2) and parametric
details of weak H-bonding CeH/O and CeH/Cl/Br in tabular form
(Table S1) are given as supplementary information, can be found in
the online version, at doi:10.1016/j.jorganchem.2010.07.025.
[16] M. Asahara, M. Tanaka, T. Erabi, M. Wada, J. Chem. Soc. Dalton Trans. (2000)
3493e3499.
References
[17] A.K.S. Chauhan, A. Kumar, R.C. Srivastava, R.J. Butcher, J. Organomet. Chem.
658 (2002) 169e175.
[18] A.K.S. Chauhan, A. Kumar, R.C. Srivastava, J. Beckmann, A. Duthie, R.J. Butcher,
J. Organomet. Chem. 689 (2004) 345e351.
[1] L. Engman, M.P. Cava, Organometallics 1 (1982) 470e473.
[2] L. Engman, M.P. Cava, J. Org. Chem. 47 (1982) 3946e3949.
[3] L. Engman, Organometallics 5 (1986) 427e431.
[19] A.K.S. Chauhan, Anamika, A. Kumar, R.C. Srivastava, R.J. Butcher, J. Organomet.
Chem. 690 (2005) 313e321.
[20] S. Misra, A.K.S. Chauhan, P. Singh, R.C. Srivastava, A. Duthie, R.J. Butcher,
Dalton Trans. (2010) 2637e2643.
[4] N. Petragnani, Tetrahedron 12 (1961) 219e225.
[5] H.A. Stefani, J.V. Comasseto, N. Petragnani, Synth. Commun. 17 (1987) 443.
[6] I.D. Sadekov, A.V. Zakharov, A.A. Maksimenko, Sulfur Reports. 23 (2002)
125e207.
[21] J. Zukerman-Schpector, R.L. Camillo, I. Caracelli, J. Comasseto, L.O.R. Cunha,
Rev. Roumaine de Chim. 47 (2003) 1021e1025.
[7] A.K.S. Chauhan, P. Singh, A. Kumar, R.C. Srivastava, R.J. Butcher, A. Duthie,
Organometallics 26 (2007) 1955e1959.
[22] A.K.S. Chauhan, P. Singh, R.C. Srivastava, R.J. Butcher, A. Duthie, J. Organomet.
Chem. 695 (2010) 2118e2125.
[8] A.K.S. Chauhan, P. Singh, R.C. Srivastava, A. Duthie, A. Voda, Dalton Trans.
(2008) 4023e4028.
[23] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837e838.
[24] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[9] G.T. Morgan, O.C. Elvins, J. Chem. Soc. 127 (1925) 2625.
[10] A. Ishii, J. Nakayama, Y. Horikawa, M. Hoshino, Sulfur Lett. 10 (1989) 71e77.