Synthesis and characterization of monomeric diorganotellurium dihalides: Crystal and molecular structures of diphenacyltellurium dibromide and -diiodide

Article abstract of DOI:10.1016/S0022-328X(02)01648-0

Tellurium, but not selenium, reacts with phenacyl bromide (ω-bromoacetophenone) to give diphenacyltellurium dibromide (PhCOCH₂)₂TeBr₂ (1), which represents the first example of a functionally substituted organotellurium ha

Full text of DOI:10.1016/S0022-328X(02)01648-0

Journal of Organometallic Chemistry 658 (2002) 169ꢀ175
/
www.elsevier.com/locate/jorganchem
Synthesis and characterization of monomeric diorganotellurium
dihalides: crystal and molecular structures of diphenacyltellurium
dibromide and -diiodide
a,
Ashok K.S. Chauhan *, Arun Kumar , Ramesh C. Srivastava , Ray J. Butcher
a
a
b
a
Department of Chemistry, University of Lucknow, Lucknow 226007, India
b
Department of Chemistry, Howard University, Washington, DC 20059, USA
Received 25 February 2002; received in revised form 6 June 2002; accepted 6 June 2002
Abstract
Tellurium, but not selenium, reacts with phenacyl bromide (v-bromoacetophenone) to give diphenacyltellurium dibromide
PhCOCH TeBr (1), which represents the first example of a functionally substituted organotellurium halide to have been
prepared directly from elemental tellurium and an organic halide. Metathesis of 1 with KI affords the crystalline diiodide,
PhCOCH TeI (2), but halideꢀpseudohalide exchange does not proceed with KSCN or AgN . Compounds 1 and 2 have been
(
2
)
2
2
(
2
)
2
2
/
3
1
13
characterized by elemental analyses, IR, H- and C-NMR and mass spectrometry. Coordinative interaction of both the carbonyl
groups in 1 and 2, in solid state as well as in solution, is indicated by IR spectra. Crystal and molecular structures of the dihalides
were determined by X-ray diffraction method. Compounds 1 and 2 are isostructural and crystallize in the monoclinic system with
space group P2
1
/n. The primary geometry about the central Te atom in both the compounds is C-trigonal-bipyramidal with axial
halogens. Stereochemically active lone pair of electrons occupies the equatorial plane along with methylene C atoms of the organic
˚
ligands. The Teꢀ ꢀ ꢀO intramolecular attractive interactions, though weak [Teꢀ ꢀ ꢀO(1), Teꢀ ꢀ ꢀO(2): 2.938, 2.912 A in 1 and 2.877, 2.818
˚
A in 2] appear to saturate tellurium(IV) atom coordinatively so as to prevent intermolecular Teꢀ ꢀ ꢀBr/I interactions. However, there
is evidence of weak intermolecular TeÃ
supramolecular assemblies. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Secondary bonding; Organotellurium halides; Intramolecular coordination
/
Brꢀ ꢀ ꢀH(methylene) secondary interactions in compound 1, leading to the formation of
1
. Introduction
of such interactions that involve sulfur and selenium
have been carried out in detail [1a,7]. Among organo-
tellurium compounds, the kinetic stability of organyl-
tellurenyl halides RTeX is enhanced when the
functionalized organic ligand provides an opportunity
for intramolecular coordination through one of its
nucleophilic atoms A, to the central tellurium(II) and
The ubiquitous nature of intermolecular and intra-
molecular attractions is a characteristic feature of
chalcogen chemistry and owes to the hypervalent nature
of the elements. Such secondary interactions have
attracted considerable interest in the last two decades
due to their role in the (a) conformation of biological
macromolecules [1], (b) stabilization of otherwise un-
a nearly linear XÃ
/
Teꢀ ꢀ ꢀA arrangement is attained [8,9].
Organotellurium(IV) halides in general, and diorga-
notellurium(IV) dihalides in particular, have been
shown to involve intermolecular Teꢀ ꢀ ꢀX and Iꢀ ꢀ ꢀI
secondary bonds that lead to molecular association
giving rise to dimeric, two-dimentional zigzag ribbon
like or three-dimentional polymeric structures in the
solid state [5,9,10]. However, when the organic ligand is
funtionalized and possesses a nucleophilic atom N or O
in close proximity to tellurium(IV), intramolecular
Teꢀ ꢀ ꢀN/O bonding is expected to discourage intermole-
stable organoseleniumꢀtellurium compounds [2], (c)
catalytic mechanism of glutathione peroxidase-like anti-
oxidant activity [3], (d) activity of the therapeutic agents
/
[1b,4] and (e) supramolecular association [5,6]. Systema-
tic structural investigations on the origin and magnitude
* Corresponding author
E-mail address: akschauhan@hotmail.com (A.K.S. Chauhan).
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 6 4 8 - 0

170
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 658 (2002) 169ꢀ175
/
1
cular Teꢀ ꢀ ꢀX secondary bonding. Organotellurium(IV)-
trichlorides and -tribromides that involve intramolecu-
lar coordination through carbonyl oxygen [11,12] or
pyridyl [13,14], azo [15], imino [16] and amino [8,17]
nitrogen as well as intermolecular Teꢀ ꢀ ꢀX secondary
bond (though weak and only one) are accessible either
via transmetallation using the organomercury derivative
and TeCl4 or by orthotelluration of the appropriate
organic substrate using n-butyllithium and elemental
tellurium followed by halogenolysis reaction with sul-
phuryl chloride or bromine [18]. The diorganotellur-
ium(IV) dihalides that have been studied for intramole-
cular coordination are of RR?TeX2 stoichiometry,
where only one organic ligand is funtionalized [19]. All
such intramolecularly coordinated organotellurium(IV)
with that appearing at 1693.4 cmꢁ in case of phenacyl
ꢁ
1
34.7 cm for 1
bromide. This negative shift [Dy(CO)ꢂ
/
ꢁ
1
and 48.2 cm for 2] is indicative of the involvement of
carbonyl oxygens in coordination to Te (IV). Larger
value of Dy(CO) for 2 suggests comparatively stronger
coordinative interaction of CO groups to Te(IV) in 2
compared with 1. Coordinative saturation of Te(IV) in 1
and 2 is also evident from the fact that both the
compounds failed to form anionic complexes with
Me NI which readily forms complexes with organotel-
4
lurium(IV) halides that are devoid of any intramolecular
coordinative interactions [21].
1
The H-NMR spectra of 1 and 2 consist of a multiplet
for the phenyl ring protons and a singlet for the
methylene protons which is shifted downfield compared
with the signal for the same protons in phenacyl
bromide. This deshielding of the methylene protons is
probably caused, at least in part, due to coordinative
interaction of the carbonyl groups. The signal for the
halides belong to 12ꢀ
/
Teꢀ5 class and always involve
/
molecular association through intermolecular, though
weak, Teꢀ ꢀ ꢀX secondary bonding in solid state.
We report here the first examples of structurally
characterized diorganotellurium(IV) dihalides in which,
both the funtionalized organic ligands are involved in
intramolecular coordination through carbonyl O atoms
1
25
methylene protons is flanked by two Te satellites with
2
125
1
/
J( TeÃ
H) value of 6.9 Hz for 1 and 6.3 Hz for 2.
1
3
The C-NMR spectra of the dihalides exhibit signals
due to carbon atom of CO group at ꢀ193 ppm and
methylene group at ꢀ27.7 ppm in addition to signals
for the phenyl ring carbon atoms at their usual places.
The mass spectrum of 1 does not show the molecular
ion peak but shows fragmentation peaks at m/z 105, 77
and the resulting 14ꢀ
/
Teꢀ
/
6 system is devoid of any
/
intermolecular Teꢀ ꢀ ꢀX secondary interaction. It also
appears to be the first report on oxidative addition of
a funtionalized alkyl halide to elemental tellurium,
/
though the addition of simple alkyl iodidesꢀbromides
/
ꢃ
ꢃ
ꢃ
to Te to give dialkyltellurium dihalides has been known
since long.
and 51 due to C H CO , C H and C H character-
6 5 6 5 4 3
istic of the fragmentation of the aromatic ketones. The
FAB mass spectrum consists of the base peak at m/z 447
ꢃ
130
Br for Te] and another peak
corresponding to [M ꢁ
/
ꢃ
130
2
. Results and discussion
at m/z 367 corresponding to [M ꢁ2Br for Te].
/
2
.1. Synthesis and spectral characterization
The freshly activated tellurium powder reacts with
2.3. Description and discussion of the structures of 1 and
2
phenacyl bromide under mild condition to afford color-
less 1. However, neither the ethylene ketal of phenacyl
bromide nor p-bromophenacyl bromide reacted with
tellurium powder even when heated up to their melting
points. While the former case is not entirely unexpected
the latter case is surprising as both phenacyl bromide
The molecular structures of 1 and 2 with atom
numbering are presented in Figs. 1 and 2, respectively.
Crystal data and numerical details of the data collection
and refinement are given in Table 1 and selected bond
lengths and angles in Table 2. Torsion angle values that
are significant to illustrate distortion from coplanarity
of the atoms around the central Te atom are given in
Table 3.
and p-bromophenacyl bromide react with Ph P with
3
equal ease to give the corresponding phosphonium salts
[
20]. The reason is probably electronic and not steric.
Metathetical reaction of 1 with an excess of KI in
chloroform yielded red needles of 2 but halideꢀpseudo-
Both the compounds crystallize in the monoclinic
system with four molecules per unit cell. The primary
/
halide exchange reactions with KSCN and AgN failed,
3
as did the reaction of Se powder with phenacyl bromide.
Both 1 and 2 are moderately soluble in chloroform and
dichloromethane and are stable to air.
2
.2. IR and NMR spectroscopic studies
The IR spectra of 1 and 2 show absorption due to
ꢁ
1
y(CO) at lower wave number ꢀ
/1650 cm
compared
Fig. 1. ORTEP view of compound 1.

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 658 (2002) 169ꢀ
/175
171
Table 2
Bond lengths (A) and angles (8) for 1 and 2
˚
1
(XꢂBr)
2 (XꢂI)
Bond lengths
TeÃX(1)
TeÃC(1B)
C(1B)ÃC(2B)
C(2B)ÃC(3B)
O(1B)ÃC(2B)
TeÃO(1A)
TeÃX(2)
TeÃC(1A)
C(1A)ÃC(2A)
C(2A)ÃC(3A)
O(1A)ÃC(2A)
TeÃO(1B)
2.6459(5)
2.134(4)
1.515(5)
1.482(5)
1.224(4)
2.938
2.8808(14)
2.131(15)
1.54(2)
Fig. 2. ORTEP view of compound 2.
1.48(2)
1.208(19)
2.877
Table 1
Crystal data and structure refinement details for compounds 1 and 2
2.6927(5)
2.139(4)
1.509(5)
1.486(5)
1.226(4)
2.917
2.9345(14)
2.131(15)
1.50(2)
Compound 1
14Br Te
Compound 2
1.48(2)
1.217(18)
2.818
Empirical formula
Formula weight
Temperature (K)
C
16
H
2
O
2
16 14 2 2
C H I O Te
525.69
93(2)
0.71073
619.67
93(2)
Bond angles
˚
Wavelength (A)
0.71073
Monoclinic
P2 /n
C(1B)ÃTeÃC(1A)
C(1B)ÃTeÃX(1)
C(1A)ÃTeÃX(1)
93.04(14)
87.56(10)
89.13(10)
107.4(2)
122.3(3)
119.1(4)
118.6(3)
118.8(3)
122.0(3)
53.2
95.8(6)
88.3(4)
88.7(4)
Crystal system
Space group
Monoclinic
P2 /n
1
1
Crystal size (mm)
Unit cell dimensions
0.15ꢄ0.35ꢄ0.98
0.12ꢄ0.35ꢄ0.96
C(2B)ÃC(1B)ÃTe
O(1B)ÃC(2B)ÃC(3B)
O(1B)ÃC(2B)ÃC(1B)
C(3B)ÃC(2B)ÃC(1B)
C(4B)ÃC(3B)ÃC(2B)
C(8B)ÃC(3B)ÃC(2B)
O(1B)ÃTeÃC(1B)
O(1B)ÃTeÃC(1A)
O(1A)ÃTeÃO(1B)
X(1)ÃTeÃX(2)
103.6(10)
123.0(14)
117.5(14)
119.5(13)
117.7(14)
121.7(14)
54.7
˚
a (A)
5.8385(7)
10.4127(13)
27.656(3)
90
5.7920(5)
7.4170(7)
˚
b (A)
˚
c (A)
40.914(4)
90
a (8)
b (8)
g (8)
91.166(2)
90
90.520(2)
90
3
145.5
149.9
˚
Volume (A )
Z
1681.0(4)
4
6.524
1757.6(3) gꢂ908
4
5.207
160.7
152.7
172.474(15)
86.52(10)
86.54(10)
107.8(2)
121.9(4)
119.8(3)
118.2(3)
121.8(4)
118.6(3)
52.9
172.64(5)
85.1(4)
88.7(4)
Absorption coefficient
ꢁ
1
C(1B)ÃTeÃX(2)
C(1A)ÃTeÃX(2)
(mm
Index ranges
)
ꢁ65h 56,
ꢁ65h 56,
ꢁ85k 58,
ꢁ475l 548
9583
C(2A)ÃC(1A)ÃTe
O(1A)ÃC(2A)ÃC(3A)
O(1A)ÃC(2A)ÃC(1A)
C(3A)ÃC(2A)ÃC(1A)
C(8A)ÃC(3A)ÃC(2A)
C(4A)ÃC(3A)ÃC(2A)
O(1A)ÃTeÃC(1A)
O(1A)ÃTeÃC(1B)
106.6(10)
121.4(13)
119.1(13)
119.4(13)
119.6(14)
121.2(14)
53.5
ꢁ
ꢁ
125k 512,
325l 531
Reflections collected
Independent reflections
Absorption correction
Data/restraints/para-
meters
8879
2864 [Rintꢂ0.0295] 2977 [Rintꢂ0.0766]
SADABS
SADABS
2864/0/191
2977/96/191
2
145.8
147.6
Goodness-of-fit on F
1.000
1.367
Final R indices
a
R
1
ꢂ0.0261,
wR ꢂ0.0572
ꢂ0.0336,
wR ꢂ0.0594
R
1
ꢂ0.0767,
wR ꢂ0.1883
ꢂ0.0834,
wR ꢂ0.1915
[
R indices (all data)
I ꢁ2s(I)]
2
2
R
1
R
1
2
2
Extinction coefficient
Largest difference peak
0.00040(15)
1.00 and ꢁ0.706
0.0027(4)
3.748 and ꢁ2.567
Table 3
ꢁ
3
Significant torsion angles (8) for 1 and 2
˚
and hole (e A
)
a
2
0
1
2
Definitions:
2
R(F
2
o
)ꢂajjF
o
jꢁjF
c
jj/ajF
o
j
and
wR(F
)ꢂ
2 2
c
1/2
c
)]} .
{
a[w(F
o
ꢁF
) ]/a[w(F
C(1B)ÃTeÃC(1A)ÃC(2A)
TeÃC(1A)ÃC(2A)ÃO(1A)
TeÃC(1A)ÃC(2A)ÃC(3A)
O(1A)ÃC(2A)ÃC(3A)ÃC(8A)
C(1A)ÃC(2A)ÃC(3A)ÃC(8A)
O(1A)ÃC(2A)ÃC(3A)ÃC(4A)
C(1A)ÃC(2A)ÃC(3A)ÃC(4A)
C(1A)ÃTeÃC(1B)ÃC(2B)
TeÃC(1B)ÃC(2B)ÃO(1B)
TeÃC(1B)ÃC(2B)ÃC(3B)
O(1B)ÃC(2B)ÃC(3B)ÃC(4B)
C(1B)ÃC(2B)ÃC(3B)ÃC(4B)
O(1B)ÃC(2B)ÃC(3B)ÃC(8B)
C(1B)ÃC(2B)ÃC(3B)ÃC(8B)
ꢁ176.7(3)
ꢁ2.6(4)
178.9(3)
167.4(4)
ꢁ14.2(6)
ꢁ12.9(5)
165.6(3)
ꢁ174.6(3)
4.7(4)
168.0(10)
1.4(17)
geometry about the central Te atom in these compounds
is C-trigonal-bipyramidal with apical positions occupied
by the more electronegative halogen atoms whereas the
methylene C atoms are at equatorial corners. The lone
pair of electrons at the third equatorial position is
ꢁ176.7(11)
ꢁ1(2)
177.4(14)
177.9(15)
ꢁ4(2)
178.9(10)
16.4(17)
ꢁ163.7(12)
ꢁ9(2)
171.5(14)
173.3(16)
ꢁ7(2)
stereochemically active as it reduces bond angles X(1)Ã
TeÃX(2) (172.58 in 1 and 172.68 in 2) and C(1A)ÃTeÃ
C(1B) (93.08 in 1 and 95.88 in 2) considerably. The
distances TeÃC(1A) and TeÃC(1B) being 2.139(4) and
.134(4) A in 1 and 2.131(15) A each in 2 are
insignificantly shorter than the sum of Pauling’s single
/
ꢁ175.3(3)
3.9(6)
/
/
/
ꢁ176.1(3)
ꢁ175.1(4)
4.8(5)
/
/
˚
˚
2

172
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 658 (2002) 169ꢀ175
/
3
bond covalent radii [22] of tellurium and sp hybridized
˚
carbon atoms (2.142 A) and may be compared with the
1. This may be attributed to steric factors as longer TeÃ
/
I
bonds in 2 would permit closer approach of the carbonyl
oxygens to the central Te atom. The Teꢀ ꢀ ꢀO interactions
appear to be weak in comparison to those reported for
other intramolecularly bonded organotellurium com-
typical values found in dialkyl- [5c], alkylaryl- [19,23]
and cycloalkyl-tellurium dihalides [5c,5d]. The phenyl
rings are planar and its bond lengths and angles are as
expected.
pounds [11,12,25ꢀ
tances fall in the range 2.13ꢀ
/
27], where the observed TeÃ
/
O dis-
˚
2.57 A {except in the case
of 2-(butyldichlorotelluro)benzaldehyde [19], where it is
Molecular association is a characteristic feature of
organotellurium(IV) halides where the central Te atom
attains six coordination via intermolecular Teꢀ ꢀ ꢀX
secondary interactions. The Teꢀ ꢀ ꢀBr distances
/
˚
2.839 A}. All such compounds consist of less strained
five membered intramolecular heterocyclic ring. How-
ever, the two organic bidentate chelating ligands with a
smaller bite present in molecules 1 and 2, that belong to
˚
.6459(5) and 2.6927(5) A in 1 are longer than the sum
2
˚
˚
of covalent radii of Te (1.37 A) and Br (1.13 A) [22] but
are typical of the reported TeÃBr bond lengths when the
/
14ꢀ
/
Teꢀ6 class, form four-membered heterocyclic rings.
/
Br atom is not involved in intermolecular Teꢀ ꢀ ꢀBr
The strong intramolecular interactions leading to close
Teꢀ ꢀ ꢀO contacts seem to be impeded by steric limitations
imposed by the tetrahedral and trigonal angles at the
carbon atoms of the methylene and the carbonyl groups,
respectively. As a consequence, all the atoms that
constitute heterocyclic rings due to intramolecular
coordination around Te atom in each of the compound
1 and 2 deviate marginally from coplanarity as is
obvious from the torsion angle values given in Table
3. Analogous weak intramolecular secondary interac-
secondary interactions [9,17]. Longer TeÃ
/
Br bond
for [2-(dimethylamino-
˚
distances, viz. 2.758(2)
methyl)phenyl]tellurium(IV) tribromide [17] and
A
˚
2
.71(1) A for 2-(2?-pyridyl)phenyltellurium(II) bromide
24] have been observed and in the case of the former
Br bonds has been attributed to the
[
elongation of TeÃ
/
involvement of this Br atom in intermolecular Teꢀ ꢀ ꢀBr
secondary interaction.
The apical TeÃ
/
I bond lengths 2.8808(14) and
.9345(14) A in compound 2 are typical of organotellur-
ium diiodides that are reported to possess nearly linear
IÃTeÃI system with two unequal TeÃI distances; the
shorter in the range 2.85ꢀ2.90 A and the longer in the
3.01 A [5d,5e]. The pair of bonds, each of
˚
˚
2
tions with Teꢀ ꢀ ꢀO distances 2.953 A for acetato(2-
˚
phenylazophenyl)-C,N?-tellurium(II) [28] and 2.988 A
/
/
/
for diacetatobis(p-methoxyphenyl)tellurium(IV) [29]
have been observed earlier and support our conclusion.
It is therefore, interesting to note that Te(IV) atom
prefers intramolecular Teꢀ ꢀ ꢀO interactions to complete
its six coordination to intermolecular Teꢀ ꢀ ꢀX secondary
interactions even when it leads to the formation of the
strained four-membered rings. The molecules of com-
pound 1 and 2 acquire cisoidal conformation of the
organic ligands, though there exists an opportunity for
the Te atom to attain six coordination in each molecule
via intramolecular Teꢀ ꢀ ꢀO secondary interaction by
adopting transoid ligand conformations by means of
˚
/
˚
range 2.91ꢀ
/
order ca. 1/2, has been described as three center-four
electron bond where lengthening of one through inter-
moleular secondary bonding of the iodine atom to a Te
or I atom in neighboring molecules shortens the other
bond of the pair. Compound 2 is the first structurally
characterized organotellurium(IV) iodide where six co-
ordination around the Te atom is achieved by intramo-
lecular secondary interactions and intermolecular Teꢀ ꢀ ꢀI
or Iꢀ ꢀ ꢀI secondary interactions are absent. The explana-
tion given above for the elongation of one of the TeÃ
/X
free rotations about TeÃ
/
C(methylene) or C(methylene)Ã
/
bond in intermolecularly bonded organotellurium ha-
lides is not applicable for 2 and may not be the only
factor for elongation in the former cases as well. There is
C(carbonyl) bonds, which is probably prohibited by the
presence of stereochemically active lone pair on the Te
atom.
evidence of intermolecular TeÃ
/
Brꢀ ꢀ ꢀH secondary bond-
ing in 1 [Brꢀ ꢀ ꢀH, 2.951 A (0.5ꢁx, 0.5ꢃy, ꢁ0.5ꢁz) and
TeÃBrÃH angle, 164.38]. One of the Br atoms of one
˚
/
/
/
/
/
/
3. Experimental
molecule bridges two H atoms, one from each methylene
groups of the neighboring molecule simultaneously (Fig.
3.1. General procedures
3), leading to the formation of molecular assemblies
with staircase like structure.
Involvement of both the carbonyl O atoms to the
All reactions were carried out under dry nitrogen gas.
Solvents were purified and dried by standard methods.
The commercial tellurium powder (Fluka) was activated
central Te atom is evident from the TeÃ
/
O distances
˚
2.938 and 2.917 A in compound 1 and 2.877 and 2.818 A
in compound 2 which are shorter than the sum of the
˚
by washing with conc. HCl and water and drying at ꢀ
/
120 8C. It was grinded for 15 min just before use.
Phenacyl bromide was prepared by bromination of
acetophenone in glacial acetic acid and its ethylene
ketal by azeotropic distillation with ethylene glycol.
Melting points were recorded in capillary tubes and are
˚
van der Waals radii (3.58 A) of the two atoms.
Comparatively smaller Teꢀ ꢀ ꢀO interatomic distances in
2
indicate stronger intramolecular interaction and is in
accordance with the larger value for Dy(CO) for 2 than

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 658 (2002) 169ꢀ
/175
173
Fig. 3. Unit cell structure of compound 1.
1 13
uncorrected. H- and C-NMR spectra were recorded
mixture was stirred vigorously for 5 h. After filtering off
the potassium halide, the red solution was concentrated
to give red needles of 2. Yield: 0.40 g (65%); m.p.
134 8C; Anal. Found: C, 31.24; H, 2.40; I, 41.22; Te,
20.35. Calc. for C H O I Te: C, 31.01; H, 2.28; I,
at 300.13 and 75.46 MHz, respectively, in CDCl or
3
DMSO-d on a Varian DRX 300 Spectrometer using
6
TMS as internal standard. IR spectra of solid samples
were examined as KBr pellets as well as chloroform
1
1
6
14 2 2
solution using a Perkinꢀ
/
Elmer RX1 Spectrometer.
40.96; Te, 20.59%. H-NMR (CDCl ), d(ppm) 8.00 (d),
3
1
3
7.67 (t), 7.52 (t), 5.43 (s). C-NMR (DMSO-d ), d(ppm)
Elemental carbon and hydrogen analyses were per-
formed on a Carlo Erba 1108 make analyzer. Tellurium
was estimated volumetrically and the halogen content
gravimetrically as silver halide. Fast atom bombardment
6
190.0, 136.8, 133.2, 128.7, 128.1, 26.7; IR; y(CO), 1645.2
ꢁ
1
cm
.
(
1
FAB) mass spectrum of 1 was recorded on a JEOL SX
02/DA-6000 Mass Spectrometer/Data System using
3.1.3. Attempted reaction of 1 with Me NI, KCN or
4
AgN3
To a solution of 1 (0.26 g, 0.5 mmol.) in chloroform
10 ml) was added Me NI (0.24 g, 1.2 mmol). The
Argon/Xenon (6 kV, 10 mA) as the FAB gas. The
accelerating voltage was 10 kV and m-nitrobenzyl
alcohol was used as the matrix.
(
4
reaction mixture was refluxed for 4 h, cooled and
filtered. The filtrate was freed from solvent and the
residue (0.23 g) was identified as unreacted 1 (authentic
3
.1.1. Synthesis of (PhCOCH ) TeBr (1)
2 2 2
A mixture of tellurium powder (1.28 g, 10 mmol) and
phenacyl bromide (4.38 g, 22 mmol) was heated to
60 8C with stirring for 5 h. Dichloromethane (10 ml)
1
H-NMR spectrum).
Compound 1 was recovered unchanged after stirring
with an excess of potassium thiocyanate or silver azide
in refluxing chloroform for 5 h.
ꢀ
/
was added and the reaction mixture was refluxed for 2 h.
The resulting green solid was filtered and washed with
cold dichloromethane (2ꢄ
hot chloroform. Concentration of the chloroform solu-
tion and addition of pet-ether (40ꢀ60 8C) afforded
colorless crystal of 1. Yield 2.6 g, (50%); m.p. 182ꢀ
/
5 ml). It was extracted with
3
.1.4. Attempted reaction of tellurium with phenacyl
/
bromide ethylene ketal or 4-bromophenacyl bromide
A mixture of tellurium powder (1.28 g, 10 mmol) and
the ethylene ketal of phenacyl bromide (5.08 g, 25
/
1
2
3
7
1
1
84 8C; Anal. Found: C, 36.56; H, 2.72; Cl, 30.35; Te,
0.43. Calc. for C H O Br Te: C, 36.56; H, 2.68; Br,
1
6
14
2
2
mmol) was heated to ꢀ70 8C for 5 h Chloroform (10
/
1
0.40; Te, 20.50%. H-NMR (CDCl ), d(ppm) 8.03(d),
3
ml) was added and the reaction mixture was refluxed for
2 h. Unreacted tellurium (1.26 g, 98%) was filtered off.
The filtrate was freed from solvent to give unreacted
ketal (4.83 g, 95.1%), m.p. 60 8C (authentic IR and H-
NMR spectrum).
1
.70 (t), 7.55 (t), 5.45 (s). C-NMR (DMSO-d ), d(ppm)
3
6
98.8, 137.72, 134.05, 129.56, 129.01, 27.57; IR: y(CO),
ꢁ
1
1
658.7 cm
.
3
.1.2. Synthesis of (PhCOCH ) TeI (2)
2
Reactants were similarly recovered unchanged when
tellurium powder was heated with 4-bromophenacyl
2
2
An excess of potassium iodide was added to a solution
of 1 (0.53 g, 1.0 mmol) in chloroform (20 ml) and the
bromide at ꢀ100 8C for 5 h.
/

174
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 658 (2002) 169ꢀ175
/
3.1.5. Attempted reaction of selenium powder with
phenacyl bromide
4. Supplementary material
Selenium powder (0.79 g, 10 mmol) and phenacyl
bromide (4.38 g, 22 mmol) were heated together at
Crystallographic data for the structure analyses have
been deposited with the Cambridge Crystallographic
Data Center, CCDC no.179339 for diphenacyltellurium
dibromide (1) and CCDC no. 179340 for diphenacyltel-
lurium diiodide (2). Copies of this information may be
obtained free of charge from The Director, CCDC, 12
ꢀ60 8C for 8 h. Chloroform (10 ml) was added and the
/
reaction mixture was refluxed for 2 h. After cooling, the
reaction mixture was filtered, washed with chloroform
(
2ꢄ/5 ml) and dried. The non-aromatic residue (0.75 g;
95%) was unreacted selenium powder. The phenacyl
bromide was recovered from the filtrate (authentic IR
spectrum).
Union Road, Cambridge CB2 1EZ, UK (Fax: ꢃ44-
1223-336033; or e-mail: deposite@ccdc.cam.ac.uk or
www: http://www.ccdc.cam.ac.uk).
/
3
.2. X-ray crystallographic studies
Acknowledgements
Diffraction quality transparent needle shaped crystals
of compound 1 were obtained by allowing a saturated
acetone solution to cool slowly at room temperature.
We are thankful to Professor (Mrs.) P.R. Shukla for
her efforts to initiate the work. The financial support
from the Department of Science and Technology,
Government of India is gratefully acknowledged.
Reddishꢀorange fine needle shaped crystals of 2 were
/
obtained by keeping the concentrated filtrate obtained
from the reaction of 1 with KI in chloroform overnight
at room temperature. The X-ray diffraction measure-
ments were performed at 93(2) K for both the com-
pounds on a Bruker P4S diffractometer employing
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0
/
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/
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(
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(
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(
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(
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(
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(
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5
(
(
(
(
(
(
d) J.D. McCullough, C. Knobler, R.F. Ziolo, Inorg. Chem. 24
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2
for compound 1 and 0.0767 and 0.1883 for the
compound 2.
19 (1980) 2556.

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