α-Telluration of 2,4,6-trimethylacetophenone under mild conditions: Role of steric factor in the solid state structures of Te(II and IV) compounds

Article abstract of DOI:10.1016/j.jorganchem.2010.05.022

Elemental tellurium inserts into the C_sp3-Br bond of α-bromomesitylmethyl ketone and due to its strong carbophilic character affords the crystalline C-tellurated derivative of 2,4,6-trimethylacetophenone, (MesCOCH₂)₂TeBr₂, 1b in over 80% yield. Electrophilic substitution of the parent ketone with aryltellurium trichlorides, at room temperature, gives nearly quantitative yields of unsymmetrical alkylaryltellurium dichlorides (MesCOCH₂)ArTeCl₂ (Ar = mesityl, Mes, 2a; 1-naphthyl, Np, 3a; anisyl, Ans, 4a). Fairly stable mesitoylmethyltellurium(II) derivatives, (MesCOCH₂)₂Te, 1 and (MesCOCH₂)ArTe (Ar = Mes, 2; Np, 3 and Ans, 4) obtained as the reduction products of their dihalotellurium(IV) analogues, readily undergo oxidative addition of dihalogens to afford the corresponding (MesCOCH ₂)₂TeX₂ (X = Cl, 1a; Br 1b; I, 1c) and (MesCOCH₂)ArTeX₂ (X = Cl, Br, I, Ar = Mes, 2a, 2b, 2c; Np, 3a, 3b, 3c and Ans, 4a, 4b, 4c). Crystallographic structural characterization of 1, 1b, 2, 2a, 2b, 2c, 3, 3a and 4c illustrates that the steric demand of mesityl group appreciably influences primary geometry around the 5-coordinate Te(IV) atom when it is bound directly to it. It also makes the Te atom inaccessible for the ubiquitous Te?X intermolecular secondary bonding interactions that result in supramolecular structures. In the crystal lattice of symmetrical telluroether 1, an interesting supramolecular synthon based upon reciprocatory weak C-H?O H-bonding interaction gives rise to chains via self-assembly. α-Bromo-2,4,6-trimethylacetophenone adds oxidatively to Te⁰/Te^II to give the dialkyl- or alkylarylTe^IV species which on reduction afford carbonyl-functionalized telluroethers.

Full text of DOI:10.1016/j.jorganchem.2010.05.022

Journal of Organometallic Chemistry 695 (2010) 2118e2125
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
a-Telluration of 2,4,6-trimethylacetophenone under mild conditions: Role of steric
factor in the solid state structures of Te(II and IV) compounds
,
a
a
b
c
Ashok K.S. Chauhan a , Puspendra 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:
Elemental tellurium inserts into the Csp3eBr bond of
a
-bromomesitylmethyl ketone and due to its strong
Received 5 April 2010
Received in revised form
15 May 2010
Accepted 20 May 2010
Available online 27 May 2010
carbophilic character affords the crystalline C-tellurated derivative of 2,4,6-trimethylacetophenone,
(MesCOCH2)2TeBr2, 1b in over 80% yield. Electrophilic substitution of the parent ketone with aryltellu-
rium trichlorides, at room temperature, gives nearly quantitative yields of unsymmetrical alkylar-
yltellurium dichlorides (MesCOCH2)ArTeCl2 (Ar ¼ mesityl, Mes, 2a; 1-naphthyl, Np, 3a; anisyl, Ans, 4a).
Fairly stable mesitoylmethyltellurium(II) derivatives, (MesCOCH2)2Te, 1 and (MesCOCH2)ArTe (Ar ¼ Mes,
2; Np, 3 and Ans, 4) obtained as the reduction products of their dihalotellurium(IV) analogues, readily
undergo oxidative addition of dihalogens to afford the corresponding (MesCOCH2)2TeX2 (X ¼ Cl, 1a; Br
1b; I, 1c) and (MesCOCH2)ArTeX2 (X ¼ Cl, Br, I, Ar ¼ Mes, 2a, 2b, 2c; Np, 3a, 3b, 3c and Ans, 4a, 4b, 4c).
Crystallographic structural characterization of 1, 1b, 2, 2a, 2b, 2c, 3, 3a and 4c illustrates that the steric
demand of mesityl group appreciably influences primary geometry around the 5-coordinate Te(IV) atom
when it is bound directly to it. It also makes the Te atom inaccessible for the ubiquitous Te/X inter-
molecular secondary bonding interactions that result in supramolecular structures. In the crystal lattice
of symmetrical telluroether 1, an interesting supramolecular synthon based upon reciprocatory weak
CeH/O H-bonding interaction gives rise to chains via self-assembly.
Keywords:
a
-Telluration
Insertion of elemental Te
Sterically hindered organotelluriums
2,4,6-Trimethylacetophenone
Intramolecular secondary bonding
interactions
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
telluroethers is reported either for diaryls with Csp2eTeeCsp2 or
alkylaryls with Csp2eTeeCsp3 groupings. Single-crystal structural
Frankland’s original method for making compounds with
a zincecarbon bond [1] has since been used for other metals and
metalloids including tellurium. Thus, simple dialkyltellurium diio-
dide results when Te is heated with an iodoalkane (or bromoalkane
in the presence of NaI) [2]. The oxidative insertion of elemental Te
studies on dialkyltellurium(II) with Csp3eTeeCsp3 groupings, being
liquids or low melting solids, are rare and limited to the cyclic
tellurium(II) derivatives [5] and (4-MeC6H4COCH2)2Te [6]. In recent
years, 2,4,6-trimethylacetophenone, due to steric bulk and mesityl
group-induced crystallizability, has attracted considerable attention
[7] as a methyl ketone precursor to metal enolates, which them-
selves are useful in many organic transformations. Taking advan-
tages of steric effect of the mesityl group and inductive (þI) effect of
the ring methyl substituents in 2,4,6-trimethylacetophenone and its
into the
Csp3eBr bond of a-bromo-substituted acylmethanes
recently achieved by us provides a one-pot synthesis of keto-func-
tionalized dialkyltellurium dibromides [3]. Another route to tellu-
rated ketones involves electrophilic substitution of methyl ketones
with ArTeCl3/TeCl4 to afford diorganotellurium dichlorides [4].
Biphasic bisulfite reduction of these diorganotellurium(IV) dihalides
results in the labile Te(II) derivatives, (RCOCH2)2Te and (RCOCH2)
ArTe (Ar ¼ 1-Np, Mes; R ¼ Ph, Me, Et, i-Pr, t-Bu). Oxidative addition
of dihalogens to these tellurides gives their dihaloTe(IV) derivatives
as crystalline solids which have been characterized by spectral and
diffraction studies [4]. Solid state structural characterization of
a-bromo derivative, stable crystalline mesitoylmethyltellurium(II
and IV) derivatives have been isolated in the crystalline state and
structurally characterized in solution and solid state.
2. Results and discussion
2.1. Synthesis
* Corresponding author.
E-mail addresses: akschauhan2003@yahoo.co.in, akschauhan@hotmail.com
The reaction between freshly ground tellurium powder and
a-
(A.K.S. Chauhan).
bromo-2,4,6-trimethylacetophenone, initiated at the melting point
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.05.022

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2118e2125
2119
of the latter, is sustainable at ambient temperature in the absence of
a solvent and gives the colourless bromide (MesCOCH2)2TeBr2 (1b)
in over 80% yield. This is interesting as the yields in the insertion
chloroform. The n(CO) among the Te(IV) compounds appears at
1686 ꢀ 4 cmꢁ1 and at 1675 ꢀ 5 cmꢁ1 for the tellurides 1 and 2
which is lower than that in the parent ketone (1703 cmꢁ1) or its
a-
reactions of elemental tellurium into Csp3eBr bond of the other
a
-
bromo derivative (1693 cmꢁ1). The 1H NMR spectra show two
signals in the ratio of 2:1 for o-Me and p-Me protons in the mesityl
group of the acylmethyl ligand. However, the o-Me protons of the
mesityl ligand in mesityltellurium(IV) dichloride, 2a, appear sepa-
rately due to restricted rotation about the TeeC bond. The 1H NMR
spectra of the dibromo and diiodo analogues, 2b and 2c, consist of
more than one signal for methylene protons and multiplets for
methyl protons probably due to species formed by partial decom-
position in solution. Appearance of a singlet for the methylene
protons for dihalides 1ae1c even at low temperature indicates that
the steric bulk of the mesityl group of the ligands does not affect the
magnetic equivalence of methylene protons. A singlet for the
methylene protons also appears for the mixed alkylaryltellurium
dihalides, (MesCOCH2)ArTeX2 (except in the spectra of 2b and 2c).
As expected these protons are shielded in case of Te(II) compounds
bromoacylmethanes including freshly prepared -bromo pinaco-
a
lone [3,8] are generally between 40 and 65%. Near quantitative yield
of the reaction may be attributed to both the electronic and steric
factors; the latter probably helps in preventing side reactions. Fig. 1
depicts a possible mechanism for the formation of symmetrical
diorganotellurium dibromides from elemental Te and RCOCH2Br.
Since the intermediate alkyltellurenyl(II) halides are known to be
kinetically unstable the ultimate product is formed either via route
(a) or (b) [9]. However, we prefer route (a) due to the fact that
MesTeBr (prepared in situ) adds MesCOCH2Br to give (MesCOCH2)
MesTeBr2 in good yields at ambient temperature (vide infra). The
first step of the mechanism may be compared with the formation of
the well-known Reformatsky intermediates. Unlike the zinc
reagents [10], rearrangementof the intermediate, RCOCH2TeBr, to its
enolate form [CH2]C(R)OTeBr] does not take place (vide infra)
possibly due to strong carbophilic character of tellurium.
Elemental tellurium failed to insert into the Csp3eX bond of i-
PrCOCH2Br and MesCOCH2Cl, even in the presence of NaI. While the
former failure is surprising, the latter case may be attributed to
stronger Csp3eCl bond. However, the chloro analogue of 1b, (Mes-
COCH2)2TeCl2 (1a) could be prepared by electrophilic substitution
of the parent ketone with TeCl4 (Scheme 1). Metathetical reactions
of 1a or 1b with KI at room temperature afforded (MesCOCH2)2TeI2
(1c) in very good yield (85% with respect to 1b). Reduction of 1b
with a stoichiometric amount of sodium metabisulfite followed by
quick separation from the aqueous layer affords the symmetrical
telluroether (MesCOCH2)2Te (1) as a yellow crystalline solid. It is
one of the few examples of crystalline dialkyltellurides that has
been characterized crystallographically. Oxidation of 1 with SO2Cl2
or I2 gives the corresponding dihalide 1a or 1c, respectively.
Te(II), in the form of aryltellurium bromides (prepared in situ
from equimolar amounts of Ar2Te2 and Br2), also inserts into the
1 (
derivatives show a singlet for the carbonyl carbon at w
is shifted a little to w 205 in the case of Te(II) derivatives. The
d
3.9), 2 (
d
4.0) and 3 (
d
4.1). The 13C NMR spectra of the Te(IV)
201, which
d
d
methylene carbon is quite shielded in case of tellurides 1e3
compared to the Te(IV) derivatives. The 125Te NMR spectra of all the
products, except 2b (where two signals appear at
1:1 ratio), show a single peak, indicating the presence of only one
Te-containing species. The 125Te chemical shift for 1b (
625) is
shifted upfield compared to analogous pinacolyl derivative (t-
BuCOCH2)2TeBr2
d 671 and 716 in
d
(
d
672), indicating a greater þI effect of a mesityl
group compared to a t-Bu group (TeeC bond distances in both the
compounds are the same). The signals for the Te(II) compounds are
shielded as expected. A more pronounced shielding in 2 compared
to 1 is indicative of the stronger þI effect of the mesityl ligand in it.
2.3. Crystal structures
The molecular structures of Te(IV) compounds 1b, 2ae2c, 3a, 4c
and Te(II) compounds 1e3 were unambiguously determined by X-
ray diffraction techniques. Asymmetric units in each case consist of
one molecule, except in 2 where four independent molecules are
present. Crystal data and structure refinement details are given in
Table 1. ORTEP views of the molecular structures of 1b, 2b, 3a, 4c
and 1, showing 30% probability displacement ellipsoids, omitting H
atoms for clarity, and captioned with the geometrical parameters
relevant to the primary geometry, are depicted in Figs. 2e5 and 7.
ORTEP views for 2a, 2c, 2 and 3 (Figs. S1eS4) are part of the
supplementary material.
All compounds bear C-tellurated 2,4,6-trimethylacetophenone
and may be described as mesitoylmethyltellurium derivatives.
Taking into account the equatorial lone pair at the hypervalent
tellurium atom, the spatial arrangement around the central atom is
best described as j-trigonal bipyramidal with the expected ligand
atom occupancies. However, the carbonyl O atom(s) of the acyl-
C
sp3eBr bond of MesCOCH2Br to afford the mixed alkylar-
yltellurium(IV) dibromides, (MesCOCH2)ArTeBr2 (Ar ¼ Mes, 2b; Np,
3b). Reduction of these bromides with Na2S2O5 affords the mixed
alkylaryltelluroethers, (MesCOCH2)ArTe (2 and 3), as crystalline
solids that are fairly stable at room temperature to symmetrization
into (MesCOCH2)2Te and Ar2Te. However, the appearance of an
additional signal at 340 ppm due to Np2Te2 in the 125Te NMR
spectrum of 3 indicates its slow disproportionation in CDCl3 solu-
tion. The dichloromethane solutions of the unsymmetrical tellur-
oethers, 2e4, are also readily oxidized by halogen or a halogen
source to form (MesCOCH2)ArTeX2 (Ar ¼ Mes, X ¼Cl, 2a; Br, 2b; I,
2c; Ar ¼ Np; X ¼ Cl, 3a; Br, 3b; I, 3c and Ar ¼ Anisyl; X ¼ Cl, 4a; Br,
4b; I, 4c). Mixed alkylaryltellurium(IV) dichlorides, (MesCOCH2)
ArTeCl2 (2ae4a), are also obtained in quantitative yields by elec-
trophilic substitution of the parent ketone, MesCOCH3 with
ArTeCl3. Unlike Reformatsky reagents, Te(IV) dibromides, 1be3b
did not react with ketones and were recovered unchanged.
methyl ligand(s) invariably approaches significantly closer to the
ꢀ
Te(IV) atom compared to Srvdw(Te,O) value of 3.58 A. It lies almost
2.2. Spectroscopic studies
in the equatorial CeTeeC plane, trans to a TeeC bond (hO/TeeC
ranges from 144.686(163)ꢂ in 1b to 163.554(143)ꢂ in 2b) and thus
imparts a coordination number of 5 (6 in case of 1b) to the Te(IV)
atom. The sum of endocyclic angles of the four-membered ring
All the synthesized crystalline mesitoylmethyltellurium(II and
IV) derivatives are fairly soluble in dichloromethane and
Fig. 1. Probable Mechanism of Te Insertion.

2120
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2118e2125
Scheme 1.
formed by the intramolecular Te/O secondary bonding interac-
tion, being close to 360ꢂ (359.8 and 359.9ꢂ in 1b, 359.9ꢂ in 2a,
359.8ꢂ in 2b, 359.9ꢂ in 2c, 359.7ꢂ in 3a, and 359.9ꢂ in 4c),
substantiates coplanarity of the atoms comprising it. Compound
1b, with a six-coordinate Te atom similar to the analogous bis
(acylmethyl)tellurium(IV) dihalides, (RCOCH2)2TeX2 (R ¼ Ph, 4-
MeC6H4, t-Bu; X ¼ Br, I) [3,8], conforms to a butterfly shape with
perfect C2v point group symmetry. But, among mesityltellurium(IV)
dihalides, (MesCOCH2)MesTeX2, the sterically cumbersome mesityl
ligand widens the equatorial CeTeeC angle appreciably (108.58(7)ꢂ
in 2a, 109.55(15)ꢂ in 2b, and 107.41(10)ꢂ in 2c) in comparison to the
values observed for 1ae1c or the average value of 96(3)ꢂ found for
hCeTeeC in the CSD for diorganotellurium dihalides [11]. The
increasing deviation from linearity obvious from the XeTeeX angle
is consistent with the decrease of d(TeeX) (X ¼ I, 174.031(10)ꢂ; Br,
170.13(2)ꢂ; Cl, 168.712(16)ꢂ) and further substantiates the influence
of steric demand of the aryl ligand on the primary geometry of
Te(IV) in these compounds. Such steric congestion causes restricted
rotation of the mesityl ligand about the TeeC bond, resulting in
magnetic inequivalence of its ortho methyl and meta protons (vide
supra) and also restricts self-assembly via intermolecular Te/X
secondary bonding interactions, a characteristic feature of the
lattices of organotellurium(IV) halides. As such, in the lattice of 2b,
reciprocatory Te/Br secondary bonding interactions lead to
dimerization only and in collaboration with CeH/OH-bonding
interactions give rise to centrosymmetric pairs of molecules with
planar Te2Br2 units (Fig. S5).
X-ray crystal structures of very few dialkyltellurium(II)
compounds are known. Besides our recent report on the crystal
structure of bis(4-methylbenzoyl)tellurium(II), the other dia-
lkyltellurium derivatives for which single-crystal X-ray diffraction
data are available in the literature include phenoxatellurine [5h]
and substituted pentane-2,4-dionato-C1,C5-tellurium(II) chelates
(Fig. 6), all of which are cyclic telluroethers.
Though acylmethyltellurium(II) derivatives are reported to be
unstable to detelluration [12], yellow crystals of compound 1 are
fairly stable at ambient atmospheric conditions. In the absence of
axial halo ligands and enhanced electron density at the Te atom in
compound 1 (when compared with the Te(IV) analogue 1b), the
organic ligands adopt a transoidal orientation about the CeTeeC
plane away from the lone pair region and impart C2 molecular
symmetry.
be justified by VSEPR, are quite large in comparison to those
reported for the telluroethers with Csp3eTeeCsp3 linkage (Fig. 6).
Interatomic distances between Te and the O atoms in the molec-
ꢀ
ular structure of 1 (3.5861(24) and 3.6027(26) A) and 3 (3.8221
ꢀ
(32) A) are comparable to the Srvdw(Te,O) value and the acute
O/TeeC angles indicate absence of intramolecular Te/O
secondary bonding interactions. While electronic and steric
repulsions are responsible for the observed molecular configura-
ꢀ
tion of 1, the intermolecular Te/O (3.1175(27) A) interaction is
preferred to the intramolecular interaction and gives rise to a one-
dimensional supramolecular array of molecules in the lattice of 3
(Fig. S6). However, the d(Te, O) and the measures of hO/TeeC
(trans), in the molecular structures of each of the four indepen-
ꢀ
dent molecules present in the crystal lattice of 2 are 3.15 ꢀ 0.05 A
and 140.50 ꢀ 0.89ꢂ, respectively. These values fulfill the criteria of
d(Te, O) < Srvdw(Te, O) and near linearity of the O/TeeC(trans)
triad, for the presence of intramolecular 1,4-Te/O secondary
bonding interactions. The occurrence of intramolecular in prefer-
ence to intermolecular Te/O secondary bonding interactions in
case of 2 may be due to difference in the steric influence of the
aryl ligands. Orientation of the aryl ring bound to Te in 2 and 3 is
nearly orthogonal to the CeTeeC plane, with the interplanar angle
between the CeTeeC plane and average plane of the ring atoms
lying in the range of 67.1e83.5ꢂ. It may be said that 1,4-Te/O
secondary bonding interactions are too subtle to influence the
molecular geometry of
a-tellurated acylmethanes and that it is
determined primarily by the electronic and steric effects of the
ligands bonded to the tellurium atom.
The parametric details of the observed intermolecular CeH/O
and CeH/X (X ¼Cl, Br, I) interactions are listed in Table S1. In the
crystal lattice of 1, an elegant supramolecular synthon based upon
CeH/O hydrogen bonding is realized, where each acylmethyl
fragment, consisting of (methylene)CeH as H-bond donor and
carbonyl O as H-bond acceptor, behaves as a plug and socket pair to
extend a chain on either side of each molecule (Fig. S7). One-
dimensional arrays of molecules in the lattice of 1b (Fig. S8) are the
result of (methylene)CeH/Br interactions.
3. Experimental
3.1. General considerations
Interestingly, the observed hCeTeeC values for the Te(II)
compounds in the present study, that lie in the range 95.5e99.6ꢂ
(except 87.0ꢂ for one of the four independent molecules) and can
Preparative work was performed under dry nitrogen. Melting
points were recorded in capillary tubes and are uncorrected.
a-
Bromo-2,4,6-trimethylacetophenone was prepared as per the

Table 1
Summary of crystallographic and data processing parameters for (MesCOCH2)2Te, 1; (MesCOCH2)NpTe, 2(MesCOCH2)MesTe, 3; (MesCOCH2)2TeBr2, 1b; (MesCOCH2)NpTeCl2, 2a; (MesCOCH2)MesTeCl2, 3a; (MesCOCH2)MesTeBr2,
3b; (MesCOCH2)MesTeI2, 3c; (MesCOCH2)AnsTeI2, 4c.
1
2
3
1b
2a
2b
2c
3a
4c
Formula
Formula weight
Temperature (K)
C
22H26O2Te
C20H24OTe
407.99
200(2)
0.71073
Monoclinic
P1211
8.7755(4)
29.892(2)
13.8304(9)
90
91.659(6)
90
3626.5(4)
8
1.495
1.641
C21H20OTe
415.97
200(2)
0.71073
Monoclinic
P121/c1
23.0867(13)
7.9797(5)
9.5954(4)
90
100.377(5)
90
1738.80(16)
4
1.589
1.713
C22H26Br2O2Te
609.85
200(2)
0.71073
Orthorhombic
Pna21
11.8618(9)
31.146(3)
6.2930(7)
90
90
90
2324.9(4)
4
1.742
C20H24Cl2OTe
478.89
200(2)
0.71073
Monoclinic
P21/c
16.8488(4)
8.3543(2)
14.4008(4)
90
99.990(2)
90
1996.32(9)
4
1.593
1.762
C20H24Br2OTe
567.79
200(2)
0.71073
Triclinic
Pe1
9.6692(5)
9.6841(5)
12.3034(5)
108.972(4)
105.160(4)
96.121(4)
1028.12(9)
2
C20H24I2OTe
661.79
200(2)
0.71073
Orthorhombic
Pna21
7.3119(2)
13.1120(4)
23.1457(5)
90
C21H20Cl2OTe
486.87
296(2)
0.71073
Orthorhombic
Pbca
10.8740(3)
17.4945(5)
21.5467(5)
90
C18H20I2O2Te
649.74
200(2)
0.71073
Monoclinic
P21/c
24.3111(6)
9.20800(10)
9.4402(2)
90
96.275(2)
90
2100.59(7)
4
2.055
4.362
450.03
200(2)
0.71073
Orthorhombic
Pca21
7.8870(2)
15.3130(6)
16.4850(6)
90
ꢀ
Wavelength,
l
(A)
Crystal system
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a
b
g
90
90
90
90
90
90
3
ꢀ
V (A )
1990.95(12)
4
1.501
2219.06(10)
4
1.981
4098.94(19)
8
1.578
Z
dcalc (mg/m3)
1.834
5.337
mcalc (mmꢁ1
)
1.506
4.730
4.127
1.718
Completeneness to
F(000)
q
max (%) 99.2
904
99.2
1632
99.4
824
99.0
1184
99.3
952
99.2
548
99.4
1240
98.7
1920
99.1
1208
Size (mm3)
0.55 ꢃ 0.45 ꢃ 0.22 0.55 ꢃ 0.35 ꢃ 0.12 0.46 ꢃ 0.36 ꢃ 0.17 0.44 ꢃ 0.37 ꢃ 0.28 0.44 ꢃ 0.35 ꢃ 0.30 0.47 ꢃ 0.35 ꢃ 0.21 0.55 ꢃ 0.42 ꢃ 0.15 0.57 ꢃ 0.41 ꢃ 0.29 0.49 ꢃ 0.44 ꢃ 0.15
h, k, l ranges collected
ꢁ11 / 11
ꢁ22 / 12
ꢁ24 / 23
4.70e32.44
11 754
ꢁ13 / 13
ꢁ45 / 34
ꢁ20 / 20
4.65e32.49
36 925
ꢁ30 / 34
ꢁ12 / 10
ꢁ14 / 14
4.53e32.53
16 072
ꢁ17 / 17
ꢁ47 / 43
ꢁ8 / 9
ꢁ25 / 22
ꢁ12 / 10
ꢁ21 / 20
4.76e32.50
18 061
ꢁ14 / 14
ꢁ14 / 14
ꢁ17 / 18
4.55e32.47
15 728
ꢁ10 / 11
ꢁ19 / 19
ꢁ31 / 33
4.67e32.57
35 393
ꢁ16 / 14
ꢁ26 / 25
ꢁ29 / 30
4.69e32.53
24 299
ꢁ35 / 36
ꢁ13 / 13
ꢁ14 / 14
4.74e32.58
33 455
q
range (ꢂ)
4.75e32.62
30 385
Reflection collected
Data/restraints/parameters
5877/1/232
0.0357
0.0894
0.946
1.858/ꢁ0.339
19 310/511/722
0.1082
0.3217
1.175
5.137/ꢁ2.930
5767/0/211
0.0456
0.0940
0.963
1.684/ꢁ0.817
7485/1/250
0.0537
0.0721
0.843
1.069/ꢁ1.117
6601/0/224
0.0243
0.0580
1.068
0.796/ꢁ0.735
6758/0/224
0.0388
0.1088
1.107
1.702/ꢁ1.676
7418/1/223
0.0232
0.0413
0.942
0.581/ꢁ0.602
6848/0/230
0.0305
0.0587
0.904
1.102/ꢁ0.738
7140/0/215
0.0371
0.0843
1.053
1.660/ꢁ1.220
R(F)a
Rw(F2)b
GoF(F2)
Largest diff. peak/hole (eA )
3
ꢀ
P
P
a
R ¼
jj Fc j ꢁ j Fo jj
/
/
j Fo j.
P
P
b
½
Rw ¼ [ w(F2o – F2c)2
w(F2o)2]
.

2122
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2118e2125
Fig. 2. Molecular structure of 1b. Selected interatomic distances (A) and angles (ꢂ): TeeC1a ¼ 2.113(2), TeeC1b ¼ 2.135(2), TeeBr1 ¼ 2.6691(13), TeeBr2 ¼ 2.6617(13),
Te/O1 ¼ 2.936(6), Te/O2 ¼ 2.949(3); C1aeTeeC1b ¼ 93.4(3), Br1eTeeBr2 ¼ 172.37(3), O1a/TeeC1b ¼ 145.8(2), O1b/TeeC1a ¼ 144.7(2).
ꢀ
literature method [13]. 1-Naphthyl, mesityl and anisyltellurium
trichlorides were prepared by the chlorination of the correspond-
ing ditelluride. IR spectra were recorded as KBr pellets using
a PerkineElmer RX1 spectrometer. The electrospray mass spectra
were recorded on a Micromass Quattro II triple quadrupole spec-
trometer setting ESI capillary at 3.5 kV and the cone voltage at 40 V.
The data are averaged over six to eight scans. 1H NMR spectra were
recorded at 300.13 MHz in CDCl3 on a Varian DRX 300 spectrometer
using Me4Si as internal standard solution. 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, respectively, as internal standards. UV spectra were recor-
ded on a Shimadzu UV-1700 spectrophotometer. Microanalyses
were carried out using a Carlo Erba 1108 analyzer. Tellurium was
estimated volumetrically.
[M ꢁ Br]þ, 612.0 [M]þ, 627.0 [M þ OH]þ, 1239.1 [2 M þ OH]. lmax in
CHCl3/nm (3
/dm3molꢁ1cmꢁ1): 252 (38 560), 242 (15 950).
3.3. Electrophilic substitution reactions of 2,4,6-
trimethylacetophenone with ArTeCl3
Compound 2a: Mesityltellurium trichloride (0.35 g, 1.0 mmol)
and 2,4,6-trimethylacetophenone (0.32 g, 2.0 mmol) were stirred
together at room temperature under a flow of dry nitrogen (w12 h).
The resulting solid was dissolved in diethyl ether and addition of
ethanol afforded colourless solid (MesCOCH2)MesTeCl2 (2a) which
was recrystallized as rectangular crystals from CH2Cl2. Yield: 0.32 g
(66%). M.p.: 177 ꢂC. Anal. Calcd. for C20H24OCl2Te: C, 50.16; H, 5.05;
Te, 26.64. Found: C, 49.80; H, 5.18; Te, 27.58.
NMR:
¼ 2.32 (s, 6H, p-Me), 2.34 (s, 6H, o-Me), 2.65 (s, 3H, o-Me),
2.83 (s, 3H, o-Me), 5.38 (s, 2H, CH2), 6.91 (s, 2H, aryl), 6.98 (s, 1H,
aryl), 7.01 (s, 1H, aryl) ppm. 13C{1H} NMR:
n
(CO): 1690 cmꢁ1. 1H
d
3.2. Insertion of elemental Te into Csp3eBr bond of
a-bromo-2,4,6-
d
¼ 19.30, 21.00, 21.15,
trimethylacetophenone
23.62, (o-Me and p-Me), 24.19 (CH2), 128.94, 130.35, 131.46, 133.82,
134.27, 134.68, 140.02, 140.28, 141.09, 142.32 (C-aryl), 201.67 (CO)
Compound 1b: Freshly ground tellurium powder (0.64 g,
-bromo-2,4,6-trimethylacetophenone (1.62 g,
ppm. 125Te{1H} NMR:
d
¼ 755 ppm. ES-MS m/z: 425.1
5.0 mmol) and
a
[M ꢁ 2Cl þ OH]þ, 445.1 [M ꢁ Cl]þ, 499.0 [M þ OH]þ, 571.2
10.0 mmol) were stirred together at w40 ꢂC for 24 h. The resulting
solid was extracted with CH2Cl2 (20 mL) and precipitated with
hexane to give crude 1b, which was recrystallized from CH2Cl2 as
colourless needle shaped crystals. Yield: 2.95 g (84%). M.p.: 205 ꢂC.
[M ꢁ 2Cl þ MesCOCH2]þ.
Compound 3a: A mixture of 1-naphthyltellurium trichloride
(0.36 g, 1.0 mmol) and 2,4,6-trimethylacetophenone (0.32 g,
2.0 mmol) was stirred slowly at room temperature under a flow of
dry nitrogen (w12 h). The resulting paste was washed with cold
petroleum ether (3 ꢃ10 mL), triturated with diethyl ether and
filtered to remove excess 2,4,6-trimethylacetophenone. The residue
was dissolved in chloroform and filtered through a short silica
column. Concentration of the extract to about one third and addi-
tion of diethyl ether afforded colourless solid (MesCOCH2)NpTeCl2
n
(CO): 1686 cmꢁ1. Anal. Calcd. for C22H26O2Br2Te: C, 43.33; H, 4.30;
Te, 20.92. Found: C, 43.52; H, 4.25; Te, 21.10. 1H NMR:
3H, p-Me), 2.31 (s, 6H, o-Me), 5.15 (s, 2H, CH2), 6.88 (s, 2H, aryl)
ppm. 13C{1H} NMR:
¼ 19.41 (p-Me), 21.14 (o-Me), 60.68 (CH2),
d
¼ 2.30 (s,
d
128.99, 133.80, 133.98, 140.27 (C-aryl), 208.48 (CO) ppm. 125Te{1H}
NMR:
d
¼ 625 ppm. ES-MS m/z: 469.1 [M ꢁ 2Br þ OH]þ, 531.0
ꢂ
ꢀ
Fig. 3. Molecular structure of 2b. Selected interatomic distances (A) and angles ( ): TeeC1a ¼ 2.151(4), TeeC1b ¼ 2.133(5), TeeBr1 ¼ 2.6447(7), TeeBr2 ¼ 2.6636(7), Te/O ¼ 2.829
(4); C1aeTeeC1b ¼ 109.5(2), Br1eTeeBr2 ¼ 170.13(2), O1a/TeeC1b ¼ 163.6(1).

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2118e2125
2123
ꢂ
ꢀ
Fig. 4. Molecular structure of 3a. Selected interatomic distances (A) and angles ( ): TeeC1a ¼ 2.121(3), TeeC1b ¼ 2.126(3), TeeCl1 ¼ 2.5146(9), TeeCl2 ¼ 2.485(1), Te/O ¼ 2.880(3);
C1aeTeeC1b ¼ 98.8(1), Cl1eTeeCl2 ¼ 171.72(3), O1a/TeeC1b ¼ 151.9(1).
(3a). Yield: 0.41 g (85%). M.p.: 185 ꢂC. Anal. Calcd. for C21H20OCl2Te:
C, 51.80; H, 4.14; Te, 26.21. Found: C, 51.50; H, 4.10; Te, 27.00. (CO):
1687 cmꢁ1. 1H NMR:
¼ 2.32 (s, 3H, p-Me), 2.37 (s, 6H, o-Me), 5.60
(s, 2H, CH2), 6.92 (s, 2H, aryl), 7.56e8.17 (m, 7H, aryl) ppm. 13C{1H}
NMR:
0.5 mmol) was carried out for 30 min. As soon as the organic layer
turned yellow it was quickly separated, washed with water
(4 ꢃ 50 mL) and dried over anhydrous Na2SO4. Concentration of the
filtrate to about one third and addition of diethyl ether afforded
a yellow solid that was dissolved in CH2Cl2/hexane (3:1) and cooled
to w10 ꢂC for 24 h to give yellow needle shaped crystals of the
telluride 1. Yield: 0.12 g (51%). M.p.: 72e74 ꢂC. Anal. Calcd. for
C22H26O2Te: C, 58.71; H, 5.82; Te, 28.35. Found: C, 59.02; H, 5.94; Te,
n
d
d
¼ 19.32 (p-Me), 21.17 (o-Me), 71.12 (CH2), 126.37, 126.81,
127.34, 128.29, 128.99, 129.46, 131.95, 132.57, 132.76, 132.88, 132.81,
134.13, 134.31, 140.33 (C-aryl), 201.47 (CO) ppm. 125Te{1H} NMR:
d
¼ 741 ppm.
Compound 4a: A solution of anisyltellurium trichloride (0.34 g,
28.10.
o-Me), 3.91 (s, 2H, CH2), 6.85 (s, 2H, aryl) ppm. 13C{1H} NMR:
¼ 16.12 (p-Me), 20.04 (o-Me), 21.06 (CH2), 128.72, 134.18, 137.39,
139.14 (C-aryl), 205.11 (CO) ppm. 125Te{1H} NMR:
¼ 386 ppm.
n
(CO): 1671 cmꢁ1. 1H NMR:
d
¼ 2.22 (s, 3H, p-Me), 2.56 (s, 6H,
1.00 mmol) and 20,40,60-trimethylacetophenone (0.32 g, 2.0 mmol)
in dry chloroform (10 mL) was heated to reflux for 3 h, cooled and
filtered through a short silica column. Concentration of the
resulting solution and addition of petroleum ether afforded col-
ourless crystalline solid (MesCOCH2)AnsTeCl2 (4a). Yield: 0.54 g
(68%). M.p.: 190 ꢂC. Anal. Calcd. for C18H20O2Cl2Te: C, 46.31; H, 4.32;
d
d
Compound 2: A solution of 2a (0.48 g, 1.00 mmol) in dichloro-
methane (w50 mL) was shaken with an aqueous solution of
Na2S2O5 (0.19 g, 1.0 mmol) for 1 h. The organic layer gradually
turned yellow. It was separated, washed (4 ꢃ 50 mL) with water
and dried over anhydrous Na2SO4. Volatiles were removed under
reduced pressure. The resulting yellow oil was dissolved in hexane
(5 ml) and cooled in a freezer overnight to give yellow rectangular
crystals of the telluride 2. Yield: 0.24 g (58%). M.p.: 61 ꢂC. Anal.
Calcd. for C20H24OTe: C, 58.88; H, 5.93; Te, 31.27. Found: C, 58.80; H,
Te, 27.33. Found: C, 46.80; H, 4.20; Te, 27.50.
NMR:
¼ 2.29 (s, 3H, p-Me), 2.32 (s, 6H, o-Me), 3.86 (s, 3H, OMe),
5.11 (s, 2H, CH2), 6.88 (s, 2H, aryl), 7.03 (d, 2H, aryl), 8.09 (d, 2H,
aryl) ppm. 13C{1H} NMR:
n
(CO): 1686 cmꢁ1. 1H
d
d
¼ 19.29 (p-Me), 21.13 (o-Me), 55.55
(OMe), 71.73 (CH2), 115.73, 117.46, 128.93, 133.77, 134.13, 135.67,
140.15, 162.33 (C-aryl), 201.41 (CO) ppm. 125Te{1H} NMR:
d
¼ 823 ppm.
5.50; Te, 30.90.
2.27 (s, 6H, o-Me), 2.53(s, 6H, o-Me), 4.01 (s, 2H, CH2), 6.81 (s, 2H,
aryl), 6.92 (s, 2H, aryl). 13C{1H} NMR:
n
(CO): 1678 cmꢁ1. 1H NMR:
d
¼ 2.26 (s, 6H, p-Me),
d
¼ 19.52, 20.11, 20.89, 21.02
3.4. Reduction of 1b, 2a, 3a and 4a to 1, 2, 3 and 4
(o-Me, p-Me), 29.50 (CH2), 117.04, 127.29, 128.58, 133.83, 137.82,
138.81, 139.40, 145.39 (C-aryl), 205.85(CO) ppm. 125Te{1H} NMR:
Compound 1: Reduction of 1b (0.31 g, 0.50 mmol) in dichloro-
d
¼ 296 ppm.
methane (50 ml) with an aqueous solution of Na2S2O5 (0.09 g,
Fig. 5. Molecular structure of 4c. Selected interatomic distances (A) and angles (ꢂ): TeeC(1a) ¼ 2.144(3), TeeC(1b) ¼ 2.126(4), TeeI(1) ¼ 2.9187(3), TeeI(2) ¼ 2.8831(3),
Te/O ¼ 2.903(3); C(1a)eTeeC(1b) ¼ 98.6(1), I(1)eTeeI(2) ¼ 175.29(1), O1a/TeeC1b ¼ 151.6(1).
ꢀ

2124
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2118e2125
hexane yielded the corresponding dihalides. Recrystallization from
CH2Cl2 or CHCl3 gave analytically pure samples.
Compound 1a: Yield: 0.17 g (66%). M.p.: 224e225 ꢂC. Anal. Calcd.
for C22H26Cl2OTe: C, 50.72; H, 5.03; Te 24.49. Found: C, 51.00; H,
4.95; Te, 25.10.
o-Me), 5.00 (s, 2H, CH2), 6.88 (s, 2H, aryl) ppm. 13C{1H} NMR:
¼ 19.41 (p-Me), 21.15 (o-Me), 60.67 (CH2), 128.99, 133.81, 133.98,
140.27 (C-aryl), 201.57 (CO) ppm. 125Te{1H} NMR:
¼ 625 ppm.
n
(CO): 1686 cmꢁ1. 1H NMR:
d
¼ 2.29 (s, 9H, p-Me and
d
d
lmax in CHCl3/nm (3
/dm3molꢁ1cmꢁ1): 254 (36 940).
Compound 2b: Yield: 0.37 g (65%). M.p.: 162 ꢂC. Anal. Calcd. for
C20H24OBr2Te: C, 42.31; H, 4.26; Te, 22.47. Found: C, 42.52; H, 4.10;
Te, 23.00.
n
(CO): 1686 cmꢁ1. 1H NMR:
d
¼ 2.32 (s, 9H, o-Me and p-
Me), 2.34e2.36 (m, 3H, p-Me), 2.61e2.65 (m, 3H, o-Me), 2.80e2.83
(m, 3H, o-Me), 5.38, 5.41, 5.46, 5.48, 5.55 (5 signals due to CH2;
combined integration equivalent to 2H), 6.91 (s, 2H, aryl), 6.98 (s,
Fig. 6. Crystallographically Characterized Substituted Pentane-2, 4-dionato-C1, C5-
tellurium(II) Chelates.
1H, aryl), 7.01 (s, 1H, aryl) ppm. 13C{1H} NMR:
d
¼ 19.34, 19.43,
20.98, 21.14, 23.33, 23.45, 24.46, 24.72 (o-Me, p-Me, CH2), 128.96,
128.99, 130.37, 130.44, 131.03, 131.47, 131.51, 132.64, 133.81, 133.88,
133.97, 134.30, 134.48, 139.59, 139.78, 140.32, 140.35, 141.16, 141.22,
142.29, 142.31 (C-aryl), 201.66, 201.70 (CO) ppm. 125Te{1H} NMR:
Compound 3: 3a was reduced in the same way as 2a to afford
yellow needles (from hexaneatꢁ10 ꢂC)of thetelluride 3. Yield:0.19 g
(45%). M.p.: 40e41 ꢂC. Anal. Calcd. forC21H20OTe:C, 60.63;H, 4.85; Te,
d
¼ 716, 672 (1:1) ppm.
Compound 3b: Yield: 0.38 g (62%). M.p.: 172 ꢂC. Anal. Calcd. for
30.67. Found: C, 61.00; H, 4.52; Te, 31.20.
¼ 2.23 (s, 9H, p-Me, o-Me), 4.18 (s, 2H, CH2), 6.72 (s, 2H, aryl),
7.48e8.15 (m, 7H, aryl) ppm.13C{1H} NMR:
n
(CO): 1680 cmꢁ1. 1H NMR:
C21H20OBr2Te: C, 43.80; H, 3.50; Te, 22.16. Found: C, 44.10; H, 3.20;
Te, 23.00.
(CO): 1688 cmꢁ1. 1H NMR:
¼ 2.32 (s, 3H, p-Me), 2.40 (s,
6H, o-Me), 5.59 (s, 2H, CH2), 6.92 (s, 2H, aryl), 7.53e8.11 (m, 7H,
aryl) ppm. 13C{1H} NMR:
d
n
d
d
¼ 19.10 (p-Me), 20.15 (o-
Me), 20.99 (o-Me), 32.20 (CH2), 115.45, 126.74,127.02,128.70,128.92,
d
¼ 19.45 (p-Me), 21.17 (o-Me), 69.30
129.83,130.07,131.91,132.28,132.79,133.37,133.41,133.90,140.57 (C-
(CH2), 126.61, 126.78, 127.46, 128.30, 128.97, 129.04, 129.47, 131.84,
132.68, 133.38, 133.76, 133.97, 134.33, 140.40 (C-aryl), 201.51 (CO)
aryl), 188.29 (CO) ppm. 125Te{1H} NMR:
Compound 4: Reduction of 4a similarly afforded (MesCOCH2)
AnsTe (4) as an orange coloured liquid that was characterized by its
bromination to (MesCOCH2)AnsTeBr2.
d
¼ 423 ppm.
ppm. 125Te{1H} NMR:
d
¼ 671 ppm.
Compound 4b: Yield: 0.35 g (62%). M.p.: 188 ꢂC. Anal. Calcd. for
C18H20O2Br2Te: C, 38.90; H, 3.63; Te, 22.96. Found: C, 39.00; H, 3.50;
Te, 23.3.
6H, o-Me), 3.85 (s, 3H, OMe), 5.32 (s, 2H, CH2), 6.88 (s, 2H, aryl), 6.98
(d, 2H, aryl), 8.07 (d, 2H, aryl) ppm. 13C{1H} NMR:
n
(CO): 1684 cmꢁ1. 1H NMR:
d
¼ 2.30 (s, 3H, p-Me), 2.35 (s,
3.5. Oxidative addition of halogens to tellurides 1e4
d
¼ 19.14 (p-Me),
A solution of the appropriate telluride, prepared by the reduc-
tion of 1.00 mmol of 1b (0.61 g) for 1; 2a (0.48 g) for 2; 3a (0.49 g)
for 3; and 4a (0.47 g) for 4; in CH2Cl2 (w20 mL), was cooled to 0 ꢂC
and treated dropwise with a solution of 1.00 mmol SO2Cl2 (0.14 g)
for 1a; Br2 (0.16 g) for 2b, 3b and 4b; I2 (0.25 g) for 1c, 2c, 3c and 4c
in the same solvent (w10 mL) under stirring over a period of
30 min. Concentration of the solution followed by addition of
21.14 (o-Me), 55.55 (o-Me), 68.93 (CH2), 114.21, 115.89, 128.99,
133.73, 133.96, 136.71, 140.26, 162.21 (C-aryl), 201.45 (CO) ppm.
125Te{1H} NMR:
d
¼ 769 ppm.
Compound 1c: Yield: 0.28 g (80%). M.p.: 211 ꢂC. Anal. Calcd. for
C22H26I2OTe: C, 37.54; H, 3.72; Te, 18.13. Found: C, 37.15; H, 3.50; Te,
19.00.
o-Me), 5.17 (s, 2H, CH2), 6.87 (s, 2H, aryl) ppm. 13C{1H} NMR:
¼ 19.86 (p-Me), 21.15 (o-Me), 56.57 (CH2), 129.08, 133.65, 134.07,
140.35 (C-aryl), 201.85 (CO) ppm. 125Te{1H} NMR:
¼ 526 ppm.
n
(CO): 1689 cmꢁ1. 1H NMR:
d
¼ 2.29 (s, 3H, p-Me), 2.35 (s, 6H,
d
d
lmax in CHCl3/nm (3
/dm3molꢁ1cmꢁ1): 282 (20 050), 346 (7780).
Compound 2c: Yield: 0.46 g (69%). M.p.: 125 ꢂC. Anal. Calcd. for
C20H24OI2Te: C, 36.30; H, 3.66; Te, 19.28. Found: C, 36.50; H, 3.55;
Te, 19.50.
n
(CO): 1685 cmꢁ1. 1H NMR:
d
¼ 2.262.77 (m, 18H, 6 Me),
4.23, 5.60 (two signals assignable to CH2 in the ratio 36:64;
combined integration equivalent to 2H), 6.87e7.03 (m, 4H, aryl)
ppm. 13C{1H} NMR:
d
¼ 19.98, 21.00, 21.17, 23.14, 25.73 (o-Me, p-
Me), 30.79 (CH2), 126.15, 127.21, 128.67, 129.13, 130.68, 131.63,
133.62, 133.93, 134.27, 138.86, 140.48, 141.51, 142.02, 147.15 (C-aryl),
201.88 (CO) ppm. 125Te{1H} NMR:
d
¼ 550 ppm.
Compound 3c: Yield: 0.41 g (60%). M.p.: 147 ꢂC. Anal. Calcd. for
C21H20OI2Te: C, 37.66; H, 3.01; Te,19.05. Found: C, 37.80; H, 3.00; Te,
19.50.
o-Me), 5.61 (s, 2H, CH2), 6.92 (s, 2H, aryl), 7.55e8.10 (m, 7H, aryl)
ppm. 13C{1H} NMR:
n
(CO): 1683 cmꢁ1. 1H NMR:
d
¼ 2.33 (s, 3H, p-Me), 2.46 (s, 6H,
d
¼ 20.02 (p-Me), 21.18 (o-Me), 65.43 (CH2),
123.63, 126.90, 127.03, 127.58, 128.20, 129.18, 129.43, 131.82, 132.34,
133.41, 133.70, 134.16, 134.29, 140.53 (C-aryl), 201.67 (CO) ppm.
125Te{1H} NMR:
d
¼ 574 ppm.
Compound 4c: Yield: 0.39 g (60%). M.p.: 150 ꢂC. Anal. Calcd. for
C18H20O2I2Te: C, 33.27; H, 3.10; Te, 19.64. Found: C, 33.60; H, 3.00;
ꢂ
ꢀ
Fig. 7. Molecular structure of 1. Selected interatomic distances (A) and angles ( ):
TeeC1a ¼ 2.148(4), TeeC1b ¼ 2.153(4), Te/O1a ¼ 3.603(3), Te/O1b ¼ 3.586(2);
C1aeTeeC1b ¼ 97.3(2), O1a/TeeC1b ¼ 109.69(9), O1b/TeeC1a ¼ 106.4(1).
Te, 20.10.
n
(CO): 1682 cmꢁ1. 1H NMR:
d
¼ 2.31 (s, 3H, p-Me), 2.41 (s,
6H, o-Me), 3.85 (s, 3H, o-Me), 5.39 (s, 2H, CH2), 6.88 (s, 2H, aryl),

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 695 (2010) 2118e2125
2125
6.90 (d, 2H, aryl), 7.99 (d, 2H, aryl) ppm. 13C{1H} NMR:
Me), 21.16 (o-Me), 55.53 (o-Me), 65.69 (CH2), 109.06, 116.25, 129.15,
d
¼ 20.02 (p-
geometrically calculated positions using a riding model and were
refined isotropically.
133.34, 134.31, 138.21, 140.40, 161.96 (C-aryl), 201.64 (CO) ppm.
125Te{1H} NMR:
d
¼ 685 ppm.
Acknowledgments
3.6. Metathetical reactions of 1b, 2a, 3a and 4a
Financial assistance by the Department of Science and Tech-
nology, Government of India, New Delhi, is gratefully acknowl-
edged. P.S. thanks C.S.I.R, New Delhi, India for an SRF.
Compound 1c was obtained in a better yield when 1b (0.61 g,
1.00 mmol) and KI (0.33 g, 2.00 mmol) were stirred together in
dichloromethane (15 mL) for w3 h. Potassium halides were
removed by filtration. Addition of petroleum ether and cooling
afforded yellow crystals of 1c. Yield: 0.60 g (85%).
Appendix A. Supplementary material
Compounds 2c (yield: 80%), 3c (yield: 69%) and 4c (yield: 94%)
were prepared in a similar way.
CCDCs 770267, 770268, 770269, 770270, 770271, 770272,
770273, 770274 and 770275 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
3.7. Alternative procedures for synthesis of 2b, 3b and 1a
Compounds 2b and 3b: To a suspension of MesTeBr (prepared in
Supplementary data associated with this article can be found in
the online version, at doi: 10.1016/j.jorganchem.2010.05.022.
situ from Mes2Te2 (0.25 g, 0.50 mmol) and Br2 (0.08 g, 0.50 mmol)
in chloroform at 0 ꢂC) was added a solution of
a-bromo-2,4,6-tri-
methylacetophenone (0.32 g, 2.00 mmol) in the same solvent at
room temperature. The reaction mixture was stirred for 12 h and
then passed through a short silica column. Addition of petroleum
ether (40e60 ꢂC) to the concentrated solution and cooling afforded
2b as a light yellow solid. Yield: 0.14 g (30%). M.p.: 160e162 ꢂC.
Under similar conditions Np2Te2 (0.25 g, 0.50 mmol) afforded
3b. Yield: 0.13 g (28%). M.p.: 172 ꢂC.
Compound 1a: A solution of TeCl4 (0.68 g, 2.5 mmol) and 2,4,6-
trimethylacetophenone (1.60 g, 5.0 mmol) in dry chloroform
(15 mL) was heated to reflux for 3 h, cooled and filtered through
a short silica column. Concentration of the resulting solution and
addition of petroleum ether afforded colourless crystalline solid,
(MesCOCH2)2TeCl2, 1a. Yield: 0.41 g (78%). M.p. 225 ꢂC.
References
[1] D. Seyferth, Organometallics 20 (2001) 2940e2955.
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(b) C.L. Raston, R.J. Secomb, A.H. White, J. Chem. Soc., Dalton (1976)
2307e2310;
(c) J.C. Dewan, J. Silver, Inorg. Nucl. Chem. Lett. 12 (1976) 647e649;
(d) J.C. Dewan, J. Silver, J. Chem. Soc., Dalton (1977) 644e647;
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(f) J.C. Dewan, J. Silver, Acta Crystallogr. B33 (1977) 2671e2674;
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10 (1973) 527e531.
3.8. Reaction of 1be3b with ketones
Compound 1b (1.0 mmol) was stirred with 5 mL of acetone,
acetophenone or pinacolone at room temperature for 3 h. Removal
of volatiles under reduced pressure afforded unreacted 1b. Like-
wise, 2b and 3b were recovered unchanged from the reaction
mixture.
[6] A.K.S. Chauhan, Anamika, A. Kumar, R.C. Srivastava, R.J. Butcher, J. Organomet.
Chem. 690 (2005) 313e321.
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(2006) 1778e1785;
(b) S.E. Baillie, E. Hevia, A.R. Kennedy, R.E. Mulvey, Organometallics 26 (2007)
204e209;
(c) D.R. Armstrong, A.M. Drummond, L. Balloch, D.V. Graham, E. Hevia, A.
R. Kennedy, Organometallics 27 (2008) 5860e5866 and references therein.
[8] A.K.S. Chauhan, P. Singh, A. Kumar, R.C. Srivastava, R.J. Butcher, A. Duthie,
Organometallics 26 (2007) 1955e1959.
[9] J. Beckmann, M. Hesse, H. Poleschner, K. Seppelt, Angew. Chem., Int. Ed. 46
(2007) 8277e8280 and references therein.
3.9. Crystallography
Single crystals suitable for X-ray crystallography were grown by
slow evaporation of dichloromethane solutions of 1b, 3a and 4c;
ether solutions of 2a, 2b and 2c and cooling of concentrated hexane
solutions of 1, 2 and 3 to ꢁ10 ꢂC. Intensity data were collected on an
[10] (a) T. Hama, X. Liu, D.A. Culkin, J.F. Hartwig, J. Am. Chem. Soc. 125 (2003)
11176e11177;
(b) T. Hama, X. Liu, D.A. Culkin, J.F. Hartwig, J. Am. Chem. Soc. 128 (2006)
4976e4985;
Oxford Diffraction Gemini CCD diffractometer with graphite-
(c) P. Powell, Principles of Organometallic Compounds, second ed. Chapman
and Hall, London, New York, 1988, p. 59 (Chapter 3);
(d) An X-ray study on BrZnCH2CO2Et however suggests simultaneous
formation of a ZneC and a ZneO bond in the dimer J. Dekker, P.H.M. Budze-
laar, J. Boersma, G.J.M. van der Kerk. Organometallics 3 (1984) 1403e1407.
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[13] C.O. Guss, J. Am. Chem. Soc. 75 (1953) 3177e3179.
[14] SMART, SAINT and SADABS. Siemens Analytical X-ray Instruments, Inc.,
Madison, Wisconsin, USA, 1999.
ꢀ
monochromated Mo-K
a
(0.7107 A) radiation. Data were reduced
and corrected for absorption using the programs SAINTand SADABS
[14]. The structures were solved by direct methods and difference
Fourier synthesis using SHELXS-97 and ORTEP figures generated
using the program WinGX 2002 [15]. Full-matrix least-squares
refinements on F2, using all data, were carried out with anisotropic
displacement parameters applied to non-hydrogen atoms. The
anisyl group of 4c is two-fold disordered with occupancies of 0.554
(8):0.45. Hydrogen atoms attached to carbon were included in
[15] (a) L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837e838;
(b) L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.