Tellurium derivatives of 3-acetyl-2,5-dimethylthiophene: Synthetic and structural aspects

Article abstract of DOI:10.1016/j.jorganchem.2012.12.038

Oxidative addition of α-bromo-3-acetyl-2,5-dimethylthiophene to elemental tellurium and aryltellurium(II) bromide provides direct routes to (2,5-dimethyl-3-thiophenoylmethyl)tellurium(IV) dibromides, (Me ₂TpnCOCH₂)₂TeBr

Full text of DOI:10.1016/j.jorganchem.2012.12.038

Journal of Organometallic Chemistry 728 (2013) 44e51
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Tellurium derivatives of 3-acetyl-2,5-dimethylthiophene: Synthetic
and structural aspects
,
a
b
c
Poornima Singh a , Ashok K.S. Chauhan , 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:
Oxidative addition of
a
-bromo-3-acetyl-2,5-dimethylthiophene to elemental tellurium and aryltellur-
Received 22 October 2012
Received in revised form
21 December 2012
ium(II) bromide provides direct routes to (2,5-dimethyl-3-thiophenoylmethyl)tellurium(IV) dibromides,
(Me2TpnCOCH2)2TeBr2 (1a; Me2Tpn ¼ 2,5-Me2-3-C4HS) and Ar(Me2TpnCOCH2)TeBr2 (Ar ¼ 1-C10H7, Npl,
2a; 2,4,6-Me3C6H2, Mes, 3a). The chloro analogs of 2a and 3a, Ar(Me2TpnCOCH2)TeCl2 (Ar ¼ Npl, 2b; Mes,
3b) and derivative when Ar ¼ Anisyl (anisyl ¼ 4-MeOC6H4, 4b) were prepared by the condensation
reaction of methyl ketone, Me2TpnCOCH3 with NplTeCl3, MesTeCl3 and anisylTeCl3 respectively while the
Accepted 27 December 2012
Keywords:
Tellurium
chloro analog of 1a, bis(2,5-dimethyl-3-thiophenoylmethyl)tellurium(IV) dichloride, (Me2TpnCOCH2)2
-
TeCl2 (1b) was obtained by the condensation reaction of methyl ketone, Me2TpnCOCH3 with TeCl4.
Metathesis of these products (1aeb, 2aeb, 3aeb and 4b) with an alkali iodide affords the iodo analogs
1c, 2c, 3c and 4c. These diorganotellurium dihalides are reduced with aqueous bisulfite to dio-
rganotellurides 1e4, which can be oxidized readily with dihalogens to the desired diorganotellurium(IV)
dihalides. The crystal structures of the Te(IV) compounds 1b, 2a, 3c and 4b have been studied and all the
Te(IV) compounds, the carbonyl functionalized organic moiety, show intramolecular 1,4eTe/O sec-
ondary bonding interaction (SBI). In the crystal lattice of 2a, the intermolecular Te/Br secondary
bonding interactions are evident and result in a dimer. They get further associated via CeH/Br sec-
ondary interactions to form a 3D supramolecular motifs. In 1b, 3c and 4b supramolecular motifs are
formed through CeH/O and CeH/Cl interactions.
3-Acetyl-2,5-dimethylthiophene
Organotellurium(IV) compound
Intramolecular secondary interaction
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
Cl2 (Tpn ¼ 2-C4H3S), first compound of its type, was obtained by the
reaction of TeCl4 with 2-acetylthiophene [14e16] and its solid state
The tellurium chemistry has been the subject of intensive
research in last three decades due to the interest of several research
groups in organometallic and supramolecular chemistry of orga-
notellurium compounds [1,2] and applications of metal complexes
of such compounds in catalysis [3e5]. An increase in the focus on
the exploration of new organotellurium compounds has been
noticed in past and as a result, various types of functionalized tel-
lurium derivatives have also been synthesized [6e13]. Functional-
ization of a Te compound by incorporating the heteroaryl moiety in
the backbone is also an interesting strategy. However, such com-
pounds have not been synthesized in a large number so far.
Heteroaroylmethyltellurium derivatives may represent a class of
such compounds and some compounds have already been explored.
Bis(2-thiophenoylmethyl)tellurium(IV) dichloride (TpnCOCH2)2Te
structure was also solved by X-ray diffraction technique [17]. Its
reduction resulted in bis(2-thiophenoylmethyl)telluride(II). Likewise,
bis(2-benzo[b]furoylmethyl)tellurium(IV)
dichloride
(BnzFu-
COCH2)2TeCl2 [15] and corresponding telluride, (BnzFuCOCH2)2Te
(BnzFu ¼ 2-C8H7O) have also been isolated.
The tellurated thiophene derivatives [18], bis(2-thiophenoylme
thyl)tellurium(IV) dibromide [19] and bis(2-furoylmethyl)tellur-
ium(IV) dibromide [20] have been synthesized recently by insertion
of elemental tellurium into the MgeC(Tpn) or by oxidative insertion
of elemental tellurium into the CeBr bond of RCOCH2Br.
Taking into consideration that this class can become more
interesting if enriched further by exploration of new analogs, in this
paper we report isolation and structural characterization including
supramolecular chemistry of the (2,5-dimethyl-3-thiophenoylme
thyl)tellurium(II and IV) derivatives with the aim of studying the
effect of different organic moieties (naphthyl, mesityl and anisyl) and
their substituents on SBI and other structural aspects. These species
* Corresponding author. Tel.: þ91 9455280547; fax: þ91 522 2338531.
E-mail address: poornima05singh@yahoo.co.in (P. Singh).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.12.038

P. Singh et al. / Journal of Organometallic Chemistry 728 (2013) 44e51
45
have been prepared under ambient conditions by (i) oxidative
addition of -bromo/iodo-2,5-dimethyl-3-acetylthiophene to ele-
All the tellurium(IV) compounds (1ae1c, 2ae2c, 3ae3c and
4ae4c) and tellurides 1 and 3 are sharp melting colorless to orange
solids, soluble in chloroform and dichloromethane while the tel-
luride 2 is red color oil and soluble in many organic solvents such as
hexane, petroleum ether, dichloromethane and chloroform. These
Te(IV) and Te(II) compounds are fairly stable as compared to the
analogous 2-acetylthiophene and 2-acetylfuran tellurium de-
rivatives [19,20].
a
mental tellurium, (ii) electrophilic substitution of 3-acetyl-2,5-
dimethylthiophene with the aryltellurium trichlorides that bear
a sterically cumbersome aryl ligand bound to tellurium atom and (iii)
oxidative addition of dihalogens to the tellurides to give the corre-
sponding tellurium(IV) dihalides. The isolated products have been
characterized with the help of elemental analyses and spectroscopic
studies. Single crystals could also be grown for some of these newly
synthesized compounds and the solid state structural studies have
been made with X-ray diffraction technique in such cases.
2.2. Spectroscopic studies
Important NMR chemical shifts of all the newly synthesized
compounds 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 in comparison to those
2. Results and discussion
2.1. Synthesis and general
of corresponding Te(IV) analogs (d 5.1e5.7 ppm) except in case of 3c
The (Me2TpnCOCH2)2TeBr2 (1a) is synthesized by the reaction of
(d
4.2 ppm). Protons of the thiophene ring along with the ring pro-
thermally unstable
a
-bromo-3-acetyl-2,5-dimethylthiophene with
tons of naphthyl, mesityl and anisyl groups appear in the aromatic
region, while the methyl protons of the thiophene and mesityl as
well as methoxy proton of anisyl group have been observed in the
aliphatic region. Appearance 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.
elemental tellurium at ambient temperature. When ArTeBr (pre-
pared in situ from Ar2Te2 and Br2; Ar ¼ Npl, Mes) is used as
a reactant instead of elemental Te in this reaction, formation of
Ar(Me2TpnCOCH2)TeBr2 (2a and 3a) takes place. The chloro ana-
logs, (Me2TpnCOCH2)2TeCl2 (1b) and Ar(Me2TpnCOCH2)TeCl2 (2be
4b) have been obtained by electrophilic substitution of the parent
ketone (Me2TpnCOCH3) with TeCl4 and ArTeCl3 (Ar ¼ Npl, Mes and
anisyl) respectively. Reduction of these dihalides (1ae3a and 1be
3b) with Na2S2O5 affords the corresponding tellurides (1e3)
with þ2 oxidation states. These tellurides (1e3) are readily oxi-
dizable with dihalogens to afford the corresponding dio-
rganotellurium(IV) dihalides (Scheme 1). The iodo analogs (1ce4c)
have been prepared by metathesis of the corresponding bromo/
chloro compounds (1a, 2b, 3b, 4b) with alkali metal iodides. Iodo
The 13C NMR chemical shifts for the carbonyl carbon appear in
the range 186e193 ppm and the methylene carbon between 58 and
70 ppm for Te(IV) derivatives and 13.6, 17.2 and 15.6 ppm in case of
tellurides 1, 2 and 3 respectively. The symmetrical (1a, 1b, 1c) and
unsymmetrical diorganotellurium(IV) derivatives (2aeb, 3aeb, 4b)
give rise to a single 125Te NMR resonance indicating the presence of
only one Te containing species in their solutions. The chemical shift
for telluride 3 (d 357 ppm) is toward higher field than those of the
analogs of 1a can also be prepared by oxidative addition of
2,5-dimethyl-3-acetylthiophene to tellurium powder.
a-iodo-
Te(IV) derivatives and the chemical shift for the Te(IV) derivatives
are consistent with the electronegativity of the halo ligands.
Scheme 1.

46
P. Singh et al. / Journal of Organometallic Chemistry 728 (2013) 44e51
Table 1
presence of attractive 1,4eTe/O interaction. This interaction can
be attributed to the overlap of a filled p-orbital on the O atom with
the vacant
Important chemical shifts (in ppm) for 2,5-dimethyl-3-thiophenoylmethyltellurium
derivatives.
s
*(TedCtrans) molecular orbital (partly responsible for
1H
13C
125Te
such an interaction) feasible. This interaction brings the O atom in
to the equatorial C1AeTeeC1B plane, reduces somewhat the tet-
rahedral angle TeeC1AeC2A to 105.1(1)ꢀ, 106.8(2)ꢀ, 104.0(2)ꢀ and
104.6(1)ꢀ in 1b, 2a, 3c and 4b respectively and marginally the trans
TeeC(aryl) bond length [d(TeeC(aryl)) ¼ 2.121(3) (2a), 2.147(3)
a
a
CH2
CH3
CH2
CH3
CO
1b
1a
1c
2b
2a
2c
3b
5.12
5.25
e
e
e
e
e
e
e
58.4
58.3
58.4
66.9
68.3
54.9
66.2
e
e
e
e
e
e
186.7
186.7
186.7
186.0
186.3
186.3
186.8
678
680
679
763
694
e
5.57
5.73
5.74
5.49
ꢀ
ꢀ
ꢀ
(3c), 2.092(2) (4b) A]; cf. 2.103 A in
b
a
-Npl2TeCl2 [21], 2.108 A in
ꢀ
-Npl2TeI2) [22] and 2.113e2.112, 2.110e2.114, 2.107e2.128 A in
(4-(MeO)C6H4)2TeX2 (where X ¼ Cl, Br, I respectively) [23e25].
In the crystal structure of symmetrically carbonyl functional-
ized diorganotellurium(IV) dichloride (1b) both the carbonyl
functionalized organic ligands exhibit (C, O) chelating behavior and
impart six-coordination to the central Te atom, similar to the
molecular structures of bis(hetroaroylmethyl)tellurium(IV) diha-
lides [(RCOCH2)2TeX2, R ¼ (C4H3S), X ¼ Cl; (C4H3O), X ¼ Cl, Br]
described earlier [17,20]. The skeletal frameworks of the organic
ligands, TeeCeC(O)eC, in these compounds are invariably almost
coplanar, with the equatorial CeTeeC plane and the cisoidal ori-
entation of the ligands imparting a butterfly shape C2v molecular
symmetry. Due to the steric influence of the methyl groups on 2-
and 5-position of the thiophene ring of organic moiety, 1,4 S/O
intramolecular secondary bonding interaction are absent in these
compounds. However such interactions have been reported to be
present in similar compounds containing 2-acetylthiophene moi-
ety [19]. In aryl(2,5-dimethyl-3-thiophenoylmethyl)tellurium(IV)
dihalides 2a, 3c and 4b, the increased values of dihedral angles
between the CeTeeC plane and the mean planes of the organic
ligands (Table 3) appears to be directly related with the steric de-
mand of the aryl ligand similarly as conclusion drawn from the
aryl(2-furoylmethyl)tellurium dichlorides [20].
In the crystal lattice of 1b, the Te centers are not involved in any
intermolecular interactions presumably due to the presence of
sterically demanding heteroaroyl moiety (Me2TpnCOCH2ꢁ). In this
case one-dimensional supramolecular array was realized due to the
presence of CeH/O and CeH/Cl, H-bonding interactions
(Figure S1).
In 2a the five-coordinate central Te atom becomes accessible
for intermolecular Te/Br secondary bonding interactions. The
centrosymmetric zero-dimensional dimeric unit was realized via
2.33, 2.44 (o-Me)
2.82 (p-Me)
2.33, 2.45 (o-Me)
2.79 (p-Me)
2.36, 2.42 (o-Me)
2.66 (p-Me)
3.88 (p-OMe)
3.88 (p-OMe)
3.87 (p-OMe)
e
21.0 (p-Me)
23.6, 24.2 (o-Me)
21.0 (p-Me)
23.3, 24.8 (o-Me)
21.0 (p-Me)
23.2, 25.9 (o-Me)
55.5 (p-OMe)
56.4 (p-OMe)
55.4 (p-OMe)
e
783
3a
3c
5.65
4.15
65.1
63.0
186.8
187.1
703
e
4b
4a
4c
1
2
3
5.24
5.45
5.50
4.06
4.11
3.95
70.3
71.2
69.9
13.6
17.2
15.6
186.2
186.1
185.7
193.1
193.6
193.0
845
e
e
e
e
e
e
2.30(p-Me)
2.61(o-Me)
21.0 (p-Me)
28.1, 29.6 (o-Me)
357
a
Methyl protons excluding those of methyl groups of 3-acetyl-2,5-
dimethylthiophene moiety.
2.3. Crystal structures
The molecular structures of 1b, 2a, 3c and 4b are shown in
Figs. 1e4 with selected bond parameters collected in the caption to
each figure. Asymmetric units in each case consist of one inde-
pendent molecule.
The central Te(IV) atom among 1b, 2a, 3c and 4b shows trigonal
bipyramidal primary geometry with expected XeTeeX and CeTeeC
angular distortions due to its lone pair. However, the CeTeeC angle
in 3c is appreciably widened by the presence of the sterically
demanding mesityl ligand in comparison to that in 1b, 2a and 4b (see
Table 2).
In molecular structures of all the four diorganotellurium(IV)
dihalides (1b, 2a, 3c and 4b), the carbonyl O atom of the sole
functionalized ligand is involved simultaneously in the intra-
molecular secondary bonding interaction to the Te(IV) center. The
observed internuclear distance between O and Te atoms, which
is shorter than the sum of their van der Waals radii [d(Te,
reciprocatory Te/Br1 interactions [d(Te, Br)
¼
3.7870(5)
ꢀ
ꢀ
ꢀ
O) ¼ 2.825(2) (1b), 2.892(3) (2a), 2.837(3) (3c), 2.803(22) (4b) A;
A < Svdw(Te, Br) (3.93 A)] (Figure S2), these dimers are self-
assembled, in the crystal lattice of 2a, by means of CeH/Br sec-
ondary bonding interactions to give rise the 3Desupramolecular
architecture (Figure S3). On the other hand in 3c, steric bulk of
ꢀ
Srvdw(Te, O) ¼ 3.58 A] and near linearity of the O/TeeCtrans triad
(:OeTeeCtrans measures 154.80(5)ꢀ, 149.9(1)ꢀ, 162.9(1)ꢀ and
152.2(4)ꢀ in 1b, 2a, 3c and 4b respectively) substantiate the
ꢀ
ꢀ
Fig. 1. Molecular structure of 1b. Selected interatomic distances (A) and angles ( ): TeeC1 2.125(2), TeeCl 2.4852(6), Te/O 2.825(2), C1eTeeC1 100.43(6), CleTeeCl 172.83(2),
O/TeeC1 154.80(5).

P. Singh et al. / Journal of Organometallic Chemistry 728 (2013) 44e51
47
ꢀ
ꢀ
Fig. 2. Molecular structure of 2a. Selected interatomic distances (A) and angles ( ): TeeC1 2.121(3), TeeC11 2.130(4), TeeBr1 2.7114(5), TeeBr2 2.6432(5), Te/O 2.892(3), C1eTeeC1
96.5(1), Br1eTeeBr2 176.79(2), O/TeeC1 149. 9(1).
the mesityl ligand hinders the involvement of central Te atom to
enter in SBIs with the electron-rich I, O or S atoms. Molecular units
in it assemble into the one-dimensional supramolecular arrays via
CeH/O interactions (Figure S4). Presence of sterically cumber-
some heteroaromatic Me2Tpn moiety in 4b appears to discourage
the Te involved SBIs to take the center-stage, which paves the way
for a combination of CeH/O and CeH/Cl interactions. The cen-
trosymmetric dimeric units was formed through strong recip-
rocatory CeH/O interactions via CeH of Me2TpnCOCH2 e moiety
and O of anisyl ligand and these dimeric units are self-assembled in
the crystal lattice via (anisyl)CeH/Cl interactions to give rise the
ribbons (i.e. one-dimensional supramolecular arrays) consisted of
well-knit molecules (Figure S5).
condensation of an appropriate tellurium(IV) chlorides (TeCl4 or
ArTeCl3) with the parent methyl ketone (Me2TpnCOCH3). These
tellurium(IV) compounds have been converted to corresponding
Te(II) compounds by reduction with aqueous sodium metabisulfite
solution. The structural aspects of these newly synthesized com-
pounds have been studied to explore the supramolecular chemis-
try. The 2,5-dimethyl-3-thiophenoylmethyl moiety among the all
Te(IV) compounds (1b, 2a, 3c & 4b) act as (C, O) chelating ligand
and in (2,5-dimethyl-3-thiophenoylmethyl)aryltellurium(IV) diha-
lides, the central Te atom is five-coordinate even in the presence of
a bulky aryl ligand.
3. Experimental
2.4. Conclusion
3.1. General procedures
A strategy involving oxidative addition of
a
-bromo-3-acetyl-
All solvents were purified and dried before use. Te powder was
2,5-dimethylthiophene to elemental tellurium and aryltellurium(II)
bromide has been used as a direct synthetic route to obtain (2,5-
dimethyl-3-thiophenoylmethyl)tellurium(IV) dibromides (1ae3a).
The corresponding dichlorides can be obtained by the
purchased from Sigma Aldrich (USA). The 3-acetyl-2,5-dimethylthi
ophene required as a precursor for the synthesis of the a-bromo-3-
acetyl-2,5-dimethylthiophene has been procured from Aldrich
(USA). 1-Naphthyl, mesityl and anisyltellurium trichlorides were
ꢀ
ꢀ
Fig. 3. Molecular structure of 3c. Selected interatomic distances (A) and angles ( ): TeeC1 2.147(3), TeeC10 2.150(3), TeeI1 2.9291(3), TeeI2 2.9073(4), Te/O 2.837(3), C1eTeeC10
108.5(1), I1eTeeI2 173.93(1), O/TeeC1 162.9(1).

48
P. Singh et al. / Journal of Organometallic Chemistry 728 (2013) 44e51
ꢀ
ꢀ
Fig. 4. Molecular structure of 4b. Selected interatomic distances (A) and angles ( ): TeeC1 2.092(23), TeeC8 2.129(2), TeeCl1 2.5111(7), TeeCl2 2.5394(7), Te/O2a 2.803(22), C1e
TeeC8 99.71(8), Cl1eTeeCl2 173.11(2), O2a/TeeC1 152.2(4).
prepared by the chlorination of their corresponding ditellurides with
SO2Cl2. Melting points were recorded in capillary tubes and are
uncorrected. 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 on a JEOL Eclipse Plus 400 NMR spectrometer,
using Me4Si and Me2Te respectively as internal standards. Spectra for
compound 2b were obtained in 1:1 CDCl3/DMSO-d6 solution, spectra
for compounds 2c, 4c and 4a were recorded in DMSO-d6 while CDCl3
was used as a solvent for all other. Microanalyses were carried out
using a Carlo Erba 1108 analyzer.
thick paste was formed, that was washed with diethyl ether
(4 ꢂ 10 mL) to remove excess of unreacted bromo compound. The
desired product 1a was extracted with dichloromethane (50 mL)
and the extract was passed through a small silica column. After that
the solvent was reduced to about 5 mL by distillation and 15 mL of
petroleum ether (40e60 ꢀC) was added to obtain a white precipi-
tate which was recrystallized from dichloromethane to give 1a as
pale yellow rectangular crystals. Yield: 1.6 g (54%). M.p.: 167 ꢀC.
Anal. Calc. for C16H18O2S2TeBr2 (593.85): C, 32.36; H, 3.06. Found: C,
32.23; H, 2.98. 1H NMR:
5.25 (s, 4H, CH2), 7.00 (s, 2H, ring proton) ppm. 13C{1H} NMR:
(CH3), 16.3 (CH3), 58.3 (CH2), 126.2, 132.2, 136.4, 151.8 (ring car-
bons), 186.7 (CO) ppm. 125Te{1H} NMR:
680 ppm.
d
2.44 (s, 6H, CH3Tpn), 2.74 (s, 6H, CH3Tpn),
14.9
d
d
3.2. Syntheses
Compound 1: A solution of 1a (0.30 g, 0.51 mmol) in dichloro-
methane (25 mL) was stirred with an aqueous solution of Na2S2O5
(0.10 g, 0.53 mmol in 25 mL distilled water) for 1 h at 0 ꢀC. The yellow
organic layer was separated, washed with water (4 ꢂ 20 mL), and
passed through anhydrous Na2SO4. The solvent was reduced under
vacuum at room temperature to about w2 mL. Diethyl ether (5 mL)
was added and the solution was kept in a deepfreezer overnight
affording yellow needles of 1. Yield: 0.17 g (78%). M.p.: 115 ꢀC. Anal.
Calc. for C16H18O2S2Te (434.04): C, 44.27; H, 4.18. Found: C, 44.14; H,
3.2.1. Synthesis of a-bromo-3-acetyl-2,5-dimethylthiophene
Bromine (1.03 mL, 20 mmol) solution in 10 mL glacial acetic acid
was added slowly over a period of 2 h from a pressure equalizing
dropping funnel to a solution of 2,5-dimethy-3-acetylthiophene
(2.84 mL, 20 mmol) in glacial acetic acid (w20 mL) with constant
stirring. During addition, the color of solution changed from brown
to darker. After the addition was complete, the reaction mixture
was stirred further for 3 h and then poured into a beaker containing
crushed ice. A colorless semi-solid got settled at the bottom, which
was washed with water (6 ꢂ 20 mL) and extracted with w50 mL
diethyl ether. The solvent was removed at reduced pressure to
obtain a residual liquid which was cooled overnight in a deep-
4.09.1H NMR:
CH2), 6.96 (s, 2H, ring proton) ppm. 13C{1H} NMR:
d
2.40 (s, 6H, CH3Tpn), 2.66 (s, 6H, CH3Tpn), 4.06 (s, 4H,
14.9 (CH3), 16.1
d
(CH3), 13.6 (CH2), 126.3, 133.2, 135.1, 148.8 (ring carbons), 193.1
(CO) ppm.
Compound 1b: Addition of a solution of SO2Cl2 (0.12 mL,
1.5 mmol) in dichloromethane (5 mL) to a cooled light yellow so-
lution of 1 (0.22 g, 0.50 mmol) in the same solvent (20 mL) resulted
in the precipitation of 1b as a white solid that was collected by
filtration. Recrystallization from dichloromethane gave 1b as white
needles. Yield: 0.23 g (91%). M.p.: 174e175 ꢀC dec. Anal. Calc. for
freezer and colorless lachrymatory crystals of
2,5-dimethylthiophene were afforded after 48 h. Yield: 4.1 g (88%).
M.p.: 47e49 ꢀC. 1H NMR:
2.43 (3H, s, CH3), 2.69 (3H, s, CH3), 4.26
a-bromo-3-acetyl-
d
(2H, s, CH2), 7.01 (1H, s, thiophene ring) ppm.
3.2.2. Syntheses of symmetrical diorganotellurium derivatives
Compound 1a: Freshly ground tellurium powder (0.50 g,
3.94 mmol) and a-bromo-3-acetyl-2,5-dimethylthiophene (1.84 g,
Table 3
Interplanar angles,
s
(ꢀ) among 3-heteroaroylmethyltellurium derivatives.
7.89 mmol) were stirred together at room temperature for 72 h. A
a
b
2,5-Dimethyl-3-thiophenoyl methyltellurium derivative
s1
s2
Table 2
1b
2a
3c
4b
14.74(5)
4.63(8)
5.8(1)
e
ꢀ
ꢀ
Important bond angles ( ) and distances (A) in compounds 1b, 2a, 3c & 4b.
8.2(1)
10.8(1)
2.16(5)
CeTeeC
TeeCeC
O/TeeCtrans
Te/O
TeeC(Ar)
2.13(5)
1b
2a
3c
4b
100.43(6)
96.5(1)
108.5(1)
99.71(8)
105.1(1)
106.8 (2)
104.0(2)
104.6(1)
154.80(5)
149.9(1)
162.9(1)
152.2(4)
2.825(2)
2.892(3)
2.837(3)
2.803(22)
e
a
s1 ¼ angle between the equatorial plane CeTeeC and mean plane of skeletal
2.121(3)
2.147(3)
2.092(23)
atoms of the heteroaroyl moiety.
b
s2 ¼ angle between the equatorial plane CeTeeC and mean plane of ring atoms
of the aryl ligand.

P. Singh et al. / Journal of Organometallic Chemistry 728 (2013) 44e51
49
C16H18O2S2TeCl2 (504.95): C, 38.06; H, 3.59. Found: C, 38.11; H, 3.47.
1H NMR:
2.43 (s, 6H, CH3Tpn), 2.74 (s, 6H, CH3Tpn), 5.12 (s, 4H,
CH2), 6.99 (s, 2H, ring proton) ppm. 13C{1H} NMR:
14.95 (CH3),16.4
(CH3), 58.4 (CH2), 126.1, 132.2, 136.4, 151.9 (ring carbons), 186.7 (CO)
ppm. 125Te{1H} NMR:
678 ppm.
Compound 1b was also prepared by condensation of TeCl4
(0.54 g, 2.0 mmol) with 3-acetyl-2,5-dimethylthiophene (0.57 mL,
5.0 mmol) in refluxing chloroform (15 mL) for 5 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. Reduction of solvent upto 5 mL by distillation, followed by
cooling, gave 1b as colorless solid which was recrystallized from
dichloromethane to give colorless needle shape crystals. Yield:
0.45 g (45%). M.p.: 174e175 ꢀC dec.
evaporation. Yield: 0.48 g (72%). M.p.: 152 ꢀC. Anal. Calc. for
C17H20OSTeCl2 (470.91): C, 43.36; H, 4.28. Found: C, 43.35; H, 4.21.
d
d
1H NMR:
d 2.33 (s, 3H, p-Me), 2.44 (s, 3H, CH3Tpn), 2.75, 2.76 (2 s,
6H, o-Me), 2.82 (s, 3H, CH3Tpn), 5.49 (s, 2H, CH2), 6.99 (s, 1H, m-H
mesityl ring), 7.01 (s, 1H, thiophene ring), 7.05 (s, 1H, m-H mesityl
d
ring) ppm. 13C{1H} NMR:
d 14.9 (CH3), 16.4 (CH3), 21.0 (p-Me), 23.6
(o-Me), 24.2 (o-Me), 66.2 (CH2), 125.9, 130.3, 131.5, 132.4, 134.5,
136.4, 140.2, 141.1, 142.2, 151.9 (aromatic carbons), 186.8 (CO) ppm.
125Te{1H} NMR:
d 783 ppm.
Compound 4b: It was synthesized by reacting anisyltellurium
trichloride (0.5 g, 1.47 mmol) with 3-acetyl-2,5-dimethylthiophene
(0.4 mL, 2.8 mmol) in a similar method as used in case of 2b and 3b.
Its recrystallization from chloroform gave rectangular colorless
crystals on slow evaporation. Yield: 0.56 g (83%). M.p.: 142 ꢀC. Anal.
Calc. for C15H16O2STeCl2 (458.86): C, 39.26; H, 3.51. Found: C, 39.23;
Compound 1c: An iodine (0.08 g, 0.3 mmol) solution in 20 mL
petroleum ether (40e60 ꢀC) was added to a cold solution of 1
(0.109 g, 0.25 mmol) in 2 mL dichloromethane at 0 ꢀC under stir-
ring. After 15 min, the precipitated solid was filtered and recrys-
tallized from dichloromethane to obtain 1c as deep orange
hexagonal crystals. Yield: 0.162 g (94%). M.p.: 154 ꢀC. Anal. Calc. for
C16H18O2S2TeI2 (687.85): C, 27.94; H, 2.64. Found: C, 27.69; H, 2.59.
H, 3.57. 1H NMR:
3H, p-OMe), 5.24 (s, 2H, CH2), 6.94 (s, 1H, thiophene ring), 7.06, 7.08
(d, 2H, o-aryl), 8.13, 8.16 (d, 2H, m-aryl) ppm. 13C{1H} NMR:
14.9
d 2.41 (s, 3H, CH3Tpn), 2.75 (s, 3H, CH3Tpn), 3.88 (s,
d
(CH3), 16.4 (CH3), 55.5 (p-OMe), 70.3 (CH2), 115.6, 118.2, 126.1, 132.1,
135.8, 136.3, 152.0, 162.2 (aromatic carbons), 186.2 (CO) ppm. 125Te
{1H} NMR:
d 845 ppm.
13C{1H} NMR:
136.4, 151.9 (ring carbons), 186.7 (CO) ppm. 125Te{1H} NMR:
d 14.95 (CH3), 16.4 (CH3), 58.4 (CH2), 126.1, 132.2,
3.2.4. Reduction of 2b, 3b to 2, 3
d
679 ppm.
Compound 2: A solution of 2b (0.24 g, 0.50 mmol) in dichloro-
methane (20 mL) was shaken with an aqueous solution of Na2S2O5
(0.09 g, 0.47 mmol) for 20 min. The yellow organic layer was sep-
arated, washed with water (4 ꢂ 20 mL) and passed through
anhydrous Na2SO4. The solvent was reduced to w1 mL by dis-
tillation and the solution was cooled to 0 ꢀC after addition of 5 mL of
hexane in order to achieve the precipitation of unreacted 2b which
is removed by filtration. The filtrate was left till the complete
evaporation of volatiles to obtain the 2 as red oil. Yield: 0.14 g (69%).
Compound 1c was also obtained when tellurium powder
(0.13 g, 1.0 mmol) and
[prepared by stirring
a
-iodo-2,5-dimethyl-3-acetylthiophene
a
-bromo-2,5-dimethyl-3-acetylthiophene
(0.47 g, 2.0 mmol) with KI (0.35 g, 2.1 mmol) in 1 mL acetone
for 1 h] were stirred together at room temperature for 2 h. An
orange paste containing the desired product (1c) formed. The 1c
was extracted with dichloromethane (20 mL), passed through
a small silica column and the solvent reduced to w2 mL by dis-
tillation. Addition of 10 mL petroleum ether (40e60 ꢀC) and
cooling afforded 1c as an orange solid. Yield: 0.47 g (68% with
respect to Te). M.p.: 154 ꢀC.
1H NMR:
CH2), 6.40 (s, 1H, thiophene ring), 7.00e8.27 (m, 7H, Npl protons)
ppm. 13C{1H} NMR:
15.2 (CH3), 16.4 (CH3), 17.2 (CH2), 116.1, 126.6,
d 2.15 (s, 3H, CH3Tpn), 2.55 (s, 3H, CH3Tpn), 4.11 (s, 2H,
d
Alternatively 1c was prepared from a solution of 1a (0.30 g,
0.51 mmol) in dichloromethane (15 mL), stirred with KI (0.33 g,
2.0 mmol) for 4 h. Potassium halides were removed by filtration
and excess solvent was removed by distillation. An orange solid
settled on cooling which was recrystallized from chloroform to give
deep orange crystals of 1c. Yield: 0.25 g (73% with respect to 1a).
M.p.: 154 ꢀC.
126.7, 126.8, 127.5, 129.3, 130.9, 133.2, 133.8, 134.2, 134.9, 136.8,
141.8, 148.8 (aromatic carbons), 193.6 (CO) ppm.
Likewise, 3 was obtained as yellow crystals from 3b (0.23 g,
0.50 mmol) and Na2S2O5 (0.09 g, 0.47 mmol). Yield: 0.15 g (75%).
M.p.: 54 ꢀC. Anal. Calc. for C17H20OSTe (400.01): C, 51.04; H, 5.04.
Found: C, 50.95; H, 5.21. 1H NMR:
d
2.30 (s, 3H, p-Me), 2.61 (s, 6H, o-
Me), 2.76 (s, 6H, CH3Tpn), 3.95 (s, 2H, CH2), 6.49 (s, 1H, thiophene
ring), 6.95 (s, 2H, m-H mesityl ring) ppm. 13C{1H} NMR:
14.9 (CH3),
d
3.2.3. Syntheses of unsymmetrical diorganotellurium dichlorides
Compound 2b: A mixture of 1-naphthyltellurium trichloride
(0.5 g, 1.39 mmol) and 3-acetyl-2,5-dimethylthiophene (0.4 mL,
2.8 mmol) was stirred together at room temperature under a flow
of dry nitrogen for 8 h. The resulting paste was washed with cold
diethyl ether (5 ꢂ 10 mL), dissolved in dichloromethane (50 mL)
and passed through a short silica column. The solvent was reduced
to 10 mL and petroleum ether (40e60 ꢀC) added to afford 2b as
a cream color solid, which was recrystallized from dichloro-
methane to give pale yellow rectangular crystals. Yield: 0.58 g
(88%). M.p.: 180 ꢀC. Anal. Calc. for C18H16OSTeCl2 (478.89): C, 45.14;
15.6 (CH2), 15.8 (CH3), 21.0 (p-Me), 28.1 (o-Me), 29.6 (o-Me), 117.1,
126.2, 127.2, 133.5, 134.3, 139.6, 145.8, 148.2 (aromatic carbons),
193.0 (CO) ppm. 125Te{1H} NMR:
d 357 ppm.
3.2.5. Oxidative addition reactions of 2, 3 with dihalogens
Compound 2a: Bromine (0.03 mL, 0.50 mmol) in hexane (10 mL)
was added dropwise at room temperature to a stirred solution of 2
(0.20 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 solid was filtered and dis-
solved in dichloromethane. The solution was passed through
a short silica column, concentrated and kept for slow evaporation to
afford 2a as yellow crystals. Yield: 0.19 g (94%). M.p.: 173 ꢀC. Anal.
Calc. for C18H16OSTeBr2 (567.79): C, 38.08; H, 2.84. Found: C, 38.05;
H, 3.37. Found: C, 45.00; H, 3.24. 1H NMR:
2.80 (s, 3H, CH3Tpn), 5.57 (s, 2H, CH2), 7.08 (s, 1H, thiophene ring),
7.61e8.25 (m, 7H, Npl protons) ppm. 13C{1H} NMR:
13.3 (CH3),
d 2.45 (s, 3H, CH3Tpn),
d
14.6 (CH3), 66.9 (CH2), 125.1, 125.5, 125.6, 125.9, 126.4, 127.7, 130.1,
130.7, 130.8, 131.8, 132.3, 132.6, 134.3, 149.6 (aromatic carbons),
H, 2.78. 1H NMR:
(s, 2H, CH2), 7.10 (s, 1H, thiophene ring), 7.59e8.24 (m, 7H, Npl
protons) ppm. 13C{1H} NMR:
14.98 (CH3), 16.5 (CH3), 68.3 (CH2),
d 2.46 (s, 3H, CH3Tpn), 2.80 (s, 3H, CH3Tpn), 5.73
186.0 (CO) ppm. 125Te{1H} NMR:
d
763 ppm.
d
Compound 3b: It has been synthesized by reaction of mesi-
tyltellurium trichloride (0.5 g, 1.42 mmol) and 3-acetyl-2,5-
dimethylthiophene (0.4 mL, 2.8 mmol) using a similar procedure
as used for 2b. Recrystallization from dichloromethane afforded
rectangular colorless crystals of the compound on slow
126.1, 126.6, 126.9, 127.4, 128.2, 129.5, 129.6, 131.9, 132.0, 132.6,
133.6, 134.3, 136.6, 152.6 (aromatic carbons), 186.3 (CO) ppm. 125Te
{1H} NMR:
d 694 ppm.
Likewise, 3a was obtained as yellow crystals from 3 (0.20 g,
0.50 mmol) and Br2 (0.03 mL, 0.50 mmol). Yield: 0.17 g (81%).

50
P. Singh et al. / Journal of Organometallic Chemistry 728 (2013) 44e51
M.p.: 145 ꢀC. Anal. Calc. for C17H20OSTeBr2 (559.81): C, 36.47; H,
3.60. Found: C, 36.35; H, 3.78. 1H NMR:
2.33 (s, 3H, p-Me), 2.45
(s, 3H, CH3Tpn), 2.73, 2.76 (2 s, 6H, o-Me), 2.79 (s, 3H, CH3Tpn),
5.65 (s, 2H, CH2), 6.97 (s, 1H, m-H mesityl ring), 7.01 (s, 1H, thio-
phene ring), 7.04 (s, 1H, m-H mesityl ring) ppm. 13C{1H} NMR:
7 h. The potassium chloride formed as a byproduct and excess of KI
were removed by filtration. The filtrate was passed through a short
silica column. Petroleum ether (40e60 ꢀC) was added to the solu-
tion after reduction of the solvent to give orange 2c which was
recrystallized from chloroform and red rectangular crystals were
obtained. Yield: 0.31 g (94%). M.p.: 135e136 ꢀC. Anal. Calc. for
C18H16OSTeI2 (661.79): C, 32.67; H, 2.44. Found: C, 32.59; H, 2.51. 1H
d
d
14.95 (CH3), 16.4 (CH3), 21.0 (p-Me), 23.3 (o-Me), 24.8 (o-Me),
65.1 (CH2), 125.8, 130.4, 131.1, 131.5, 132.2, 136.4, 139.8, 141.2,
142.1, 152.0 (aromatic carbons), 186.8 (CO) ppm. 125Te{1H} NMR:
NMR:
7.11 (s,1H, thiophene ring), 7.53e8.20 (m, 7H, Npl protons) ppm. 13C
{1H} NMR:
15.4 (CH3), 16.6 (CH3), 55.2 (CH2), 120.1, 127.1, 127.4,
d 2.46 (s, 3H, CH3Tpn), 2.80 (s, 3H, CH3Tpn), 5.74 (s, 2H, CH2),
d
703 ppm.
Compound 4a:
A
solution of 4b (0.23 g, 0.50 mmol) in
d
dichloromethane (25 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 solvent was reduced to w1 mL
and the solution was cooled to 0 ꢀC after addition of 5 mL of
hexane to remove the precipitate, so formed, of unreacted 4b by
filtration. In the filtrate, Br2 (0.03 mL, 0.50 mmol) solution in
hexane (5 mL) was added and stirred for 15 min to obtain the 4a
as a solid which was filtered, dissolved in dichloromethane, passed
through a short silica column and kept for crystallization to afford
4a as yellow crystals. Yield: 0.17 g (62%). M.p.: 142 ꢀC dec. Anal.
Anal. Calc. for C15H16O2STeBr2 (547.76): C, 32.89; H, 2.94. Found: C,
127.6, 128.0, 129.4, 130.9, 133.2, 133.7, 136.2, 136.5, 137.1, 144.7, 150.7
(aromatic carbons), 186.6 (CO) ppm.
Compound 3c was prepared in a similar way used for the
metathesis of 3b (0.24 g, 0.50 mmol) with KI (0.33 g, 2.0 mmol) as
orange crystals. Yield: 0.24 g (73%). M.p.: 108 ꢀC. Anal. Calc. for
C17H20OSTeI2 (653.81): C, 31.23; H, 3.08. Found: C, 31.15; H, 3.01. 1H
NMR:
d 2.36 (s, 3H, p-Me), 2.42 (s, 3H, CH3Tpn), 2.66 (s, 3H,
CH3Tpn), 2.77 (s, 6H, o-Me), 4.15 (s, 2H, CH2), 7.00 (s, 2H, m-H
mesityl ring), 7.02 (s, 1H, thiophene ring) ppm. 13C{1H} NMR:
d
15.01 (CH3), 16.3 (CH3), 21.0 (p-Me), 23.2 (o-Me), 25.9 (o-Me), 63.0
(CH2), 125.8, 127.2, 130.7, 131.7, 132.2, 136.5, 139.3, 141.9, 147.1, 152.0
(aromatic carbons), 187.1 (CO) ppm.
32.78; H, 2.87. 1H NMR:
d
2.42 (s, 3H, CH3Tpn), 2.76 (s, 3H,
Compound 4c was also prepared using similar procedure as in
case of 2c and 3c by metathesis of 4b (0.23 g, 0.50 mmol) with NaI
(0.30 g, 2.0 mmol) or KI (0.33 g, 2.0 mmol) as orange crystals of 4c.
Yield: 0.24 g (75%). M.p.: 134 ꢀC. Anal. Calc. for C15H16O2STeI2
CH3Tpn), 3.88 (s, 3H, p-OMe), 5.45 (s, 2H, CH2), 6.97 (s, 1H, thio-
phene ring), 7.02, 7.05 (d, 2H, o-aryl), 8.11, 8.14 (d, 2H, m-aryl)
ppm. 13C{1H} NMR:
d 15.1 (CH3), 16.4 (CH3), 56.4 (p-OMe), 71.2
(CH2), 115.4, 118.1, 126.2, 132.3, 134.9, 136.6, 152.0, 161.5 (aromatic
carbons), 186.1 (CO) ppm.
(641.76): C, 28.07; H, 2.51. Found: C, 28.13; H, 2.47. 1H NMR:
d 2.43
(s, 3H, CH3Tpn), 2.75 (s, 3H, CH3Tpn), 3.87 (s, 3H, p-OMe), 5.50 (s,
2H, CH2), 6.94 (s, 1H, thiophene ring), 6.99 (d, 2H, o-aryl), 8.06 (d,
3.2.6. Metathetical reactions of 2b, 3b, 4b with KI
2H, m-aryl) ppm. 13C{1H} NMR:
d 14.6 (CH3), 15.8 (CH3), 55.4
Compound 2c:
A
solution of 2b (0.24 g, 0.50 mmol) in
(p-OMe), 69.9 (CH2), 114.5, 126.2, 132.3, 134.7, 136.2, 143.4, 149.9,
dichloromethane (25 mL) was stirred with KI (0.33 g, 2.0 mmol) for
159.4 (aromatic carbons), 185.7 (CO) ppm.
Table 4
Crystal data and structure refinement details for 1b, 2a, 3c and 4b.
1b
2a
3c
4b
Empirical formula
C16H18Cl2O2S2 Te
504.92
C18H16Br2OSTe
567.79
C17H20I2OSTe
653.79
C15H16Cl2O2STe
458.84
Formula mass (g molꢁ1
)
Temperature (K)
295(2)
0.71073
295(2)
0.71073
295(2)
0.71073
295(2)
0.71073
ꢀ
Wavelength,
l
(A)
Crystal system
Orthorhombic
Triclinic
Monoclinic
0.47 ꢂ 0.43 ꢂ 0.35
P 1 21/n 1
7.5175(2)
18.6185(4)
15.0694(3)
90
94.471(2)
90
2102.76(9)
4
Triclinic
Crystal size (mm3)
Space group
0.52 ꢂ 0.26 ꢂ 0.10
0.51 ꢂ 0.32 ꢂ 0.25
0.41 ꢂ 0.38 ꢂ 0.24
P c c n
P ꢁ1
P ꢁ1
ꢀ
a (A)
15.4652(5)
13.8512(6)
9.5644(2)
90
90
90
2048.82(12)
4
1.637
1.921
9.2753(4)
9.8603(4)
10.7574(5)
83.515(3)
86.702(4)
80.082(4)
962.21(7)
2
8.1440(3)
8.9352(3)
12.1090(5)
81.050(3)
87.973(3)
88.726(3)
869.75(6)
2
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(deg)
(deg)
(deg)
3
ꢀ
V (A )
Z
rcalcd (Mg mꢁ3
)
1.960
5.808
540
2.065
4.450
1216
1.752
2.137
448
Absorption coefficient (mmꢁ1
F(000)
)
992
h, k, l ranges collected
ꢁ12 / 24
ꢁ14 / 11
ꢁ14 / 14
ꢁ16 / 16
12,231
ꢁ6 / 11
ꢁ26 / 28
ꢁ20 / 22
17,079
ꢁ12 / 12
ꢁ13 / 13
ꢁ18 / 16
11,235
ꢁ10 / 22
ꢁ15 / 15
Reflection collected
10,844
Independent reflections
q
4229 [R(int) ¼ 0.0279]
6338 [R(int) ¼ 0.0374]
5.14e32.73
98.8
7081 [R(int) ¼ 0.0305]
5.07e32.75
99.2
5739 [R(int) ¼ 0.0225]
5.10e32.76
99.2
range (ꢀ)
5.01e34.98
Completeness to qmax (%)
Absorption correction
Max., min. transmission
Refinement method
99.1
Semi-empirical from equivalents
1.00000, 0.55270
Full-matrix least-squares on F2
4229/0/107
1.00000, 0.38024
1.00000, 0.74890
1.00000, 0.68858
Data/restraints/parameters
6338/0/211
0.835
7081/0/204
0.900
5739/0/198
0.979
Goodness of fit on F2
0.907
Final R indices (I > 2
R indices (all data)
Largest diff peak/hole (e A
s
(I))
R1 ¼ 0.0295, wR2 ¼ 0.0688
R1 ¼ 0.0560, wR2 ¼ 0.0759
0.786/ꢁ0.536
R1 ¼ 0.0413, wR2 ¼ 0.0774
R1 ¼ 0.0968, wR2 ¼ 0.0853
1.172/ꢁ1.026
R1 ¼ 0.0354, wR2 ¼ 0.0637
R1 ¼ 0.0805, wR2 ¼ 0.0709
1.096/ꢁ0.821
R1 ¼ 0.0310, wR2 ¼ 0.0673
R1 ¼ 0.0517, wR2 ¼ 0.0718
1.100/ꢁ0.514
ꢀꢁ3
)
Extinction coefficient
e
e
e
0.0036(9)

P. Singh et al. / Journal of Organometallic Chemistry 728 (2013) 44e51
51
3.2.7. Alternative procedures for synthesis of 2a and 3a
obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
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,
1.0 mmol) and Br2 (0.05 mL, 1.0 mmol) at room temperature],
Appendix B. Supplementary data
a
-bromo-2,5-dimethyl-3-acetylthiophene (0.47 g, 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 ꢀC) added. Yellow crystals separated on overnight
cooling in a refrigerator. Yield: 2a, 0.88 g (79%); 3a 0.83 g (73%).
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2012.12.038.
References
[1] I. Haiduc, J. Zukerman-Schpector, Phosphorus, Sulfur Silicon Relat. Elem. 171
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3.3. Crystallography
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3533e3545.
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[6] P.C. Srivastava, A. Sinha, S. Bajpai, H.G. Schmidt, M. Noltemeyer, J. Organomet.
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Single crystals suitable for X-ray crystallography were grown by
slow evaporation of dichloromethane solutions of 1b, 2a, 3c and 4b.
Intensity data were collected on an Oxford Diffraction Gemini CCD
ꢀ
diffractometer with graphite-monochromated Mo-K
a
(0.7107 A)
radiation. Data were reduced and corrected for absorption 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 [26]. 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 geo-
metrically calculated positions using a riding model and were
refined isotropically. Crystal data and structure refinement details
are given in Table 4. The molecular structures are depicted in
Figs. 1e4, showing 30% (1b, 2a, 3c, 4b) probability displacement
ellipsoids, omitting H atoms for clarity, and captioned with the
geometrical parameters relevant to the primary geometry were
generated using the program ORTEP-3 version 2.02 [27].
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Acknowledgments
Financial assistance by the Department of Science and Tech-
nology, Government of India, New Delhi, is gratefully acknowl-
edged. P.S. thanks Council of Scientific and Industrial Research
(India) for the award of Senior Research Fellowship.
Appendix A. Supplementary material
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CCDC 871504, 871505, 871506 and 871507 contain the supple-
mentary crystallographic data for this paper. These data can be