Synthesis and reactivity of para-substituted benzoylmethyltellurium(II and IV) compounds: Observation of intermolecular C-H-O hydrogen bonding in the crystal structure of (p-MeOC6H4 COCH2)2TeBr2

Article abstract of DOI:10.1016/j.jorganchem.2003.10.021

Bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YC₆H₄COCH₂)₂ TeBr₂, (Y=H (1a), Me (1b), MeO (1c)) can be prepared either by direct insertion of elemental Te across C_Rf-Br bonds (wh

Full text of DOI:10.1016/j.jorganchem.2003.10.021

Journal of Organometallic Chemistry 689 (2004) 345–351
www.elsevier.com/locate/jorganchem
Synthesis and reactivity of para-substituted
benzoylmethyltellurium(II and IV) compounds: observation of
intermolecular C–H–O hydrogen bonding in the crystal structure
of (p-MeOC6H4COCH2)2TeBr2
a,
a
a
Ashok K.S. Chauhan *, Arun Kumar , Ramesh C. Srivastava ,
b
Jens Beckmann , Andrew Duthie , Ray J. Butcher
b
c
a
Department of Chemistry, University of Lucknow, Lucknow 226007, India
b
Centre for Chiral and Molecular Technologies, Deakin University, Geelong 3217, Australia
c
Department of Chemistry, Howard University, Washington, DC 20059, USA
Received 18 October 2003; accepted 18 October 2003
Abstract
Bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YC6H4COCH2)2TeBr2, (Y ¼ H (1a), Me (1b), MeO (1c)) can be pre-
pared either by direct insertion of elemental Te across CRf –Br bonds (where CRf refers to a-carbon of a functionalized organic
moiety) or by the oxidative addition of bromine to (p-YC6H4COCH2)2Te (Y ¼ H (2a), Me (2b), MeO (2c)). Bis(p-substituted
benzoylmethyl)tellurium dichlorides, (p-YC6H4COCH2)2TeCl2 (Y ¼ H (3a), Me (3b), MeO (3c)), are prepared by the reaction of the
bis(p-substituted benzoylmethyl)tellurides 2a–c with SO2Cl2, whereas the corresponding diiodides (p-YC6H4COCH2)2TeI2 (Y ¼ H
(4a), Me (4b), MeO (4c)) can be obtained by the metathetical reaction of 1a–c with KI, or alternatively, by the oxidative addition of
iodine to 2a–c. The reaction of 2a–c with allyl bromide affords the diorganotellurium dibromides 1a–c, rather than the expected
triorganotelluronium bromides. Compounds 1–4 were characterized by elemental analyses, IR spectroscopy, 1H, 13C and 125Te
NMR spectroscopy (solution and solid-state) and in case of 1c also by X-ray crystallography. (p-MeOC6H4COCH2)2TeBr2 (1c)
provides, a rare example, among organotellurium compounds, of a supramolecular architecture, where C–H–O hydrogen bonds
appear to be the non-covalent intermolecular associative force that dominates the crystal packing.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: C–H–O Hydrogen bonding; Supramolecular self-assembly; Secondary bonding; Functionalized Organotellurium halides
1. Introduction
sium telluracyanate, KTeCN, prepared from KCN and
Te powder. The corresponding Te(II) compounds are
reported to be formed either by the reduction of their
parent dichlorides [7] or by the reaction between lithium
enolate of a methylketone and PhTeI, prepared in situ
[9]. Although many of these compounds have been
characterized spectroscopically, only little information is
available on their solid-state structures. The role of non-
covalent secondary bonding, a characteristic feature of
organotellurium compounds, is currently being investi-
gated in the context of supramolecular chemistry prin-
ciples. Among organotellurium halides, Te–X secondary
interactions are responsible for the formation of either
supramolecular arrays or oligomeric supermolecules,
Organotellurium compounds containing RCOCH2
group have received considerable attention due to their
application in non-silver imaging [1] and as synthons for
a-haloketones [2,3]. Bis(aroylmethyl)- and arylaroylm-
ethyl tellurium dichlorides obtained earlier [2–7] by the
electrophillic substitution reaction of aroylmethyl ke-
tones with air/moisture sensitive TeCl4 or ArTeCl3, have
recently [8] also been synthesized by the use of potas-
* Corresponding author. Tel.: +91-522-2740245; fax: +91-522-
2331299.
E-mail address: akschauhan@hotmail.com (A.K.S. Chauhan).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.10.021

346
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 689 (2004) 345–351
but in presence of N, O or S atoms secondary interac-
tion between Te and the pnictogen/chalcogen is reported
to be the intermolecular force to associate molecular
units into supramolecular architectures [10,11]. Re-
cently, we have prepared bis(benzoylmethyl)tellurium
dibromide, (C6H5COCH2)2TeBr2 (1a), by the direct re-
action of elemental tellurium with phenacyl bromide
(Eq. (1), R ¼ Ph) and examined its crystal structure [12].
Of particular interest was the presence of rare bridging
C–H–Br hydrogen bonds that gave rise to polymeric
chains as the supramolecular motif.
resulted in the formation of the diorganotellurides
(p-YC6H4COCH2)2Te (Y ¼ H (2a), Me (2b), MeO (2c))
(Scheme 1). The oxidative addition of Br2 or I2 to 2a–c
provided the corresponding diorganotellurium bromides
1a–c and diiodides 4a–c, respectively (Scheme 1).
Usually the addition of methyl iodide and allyl bro-
mide to diorganotellurides R2Te proceeds via formation
of the corresponding triorganotelluronium salts [13,14].
However, when compounds 2a–c were reacted with allyl
bromide compounds 1a–c were formed instead of the
expected [(p-YC6H4COCH2)2 Te(C3H5)]þBrꢀ. The re-
action of compound 2a with MeI provided tellurium
metal and a sticky mass of unknown structure. Sulphuryl
chloride however, reacted with compounds 2a–c to give
the diorganotellurium dichlorides (p-YC6H4COCH2)2
TeCl2 (Y ¼ H (3a), Me (3b), MeO (3c)), which have
previously been obtained by the reaction of air sensitive
TeCl4with the respective ketones with the liberation of
HCl [5a]. All the diorganotellurium(IV) dihalides are
crystalline solids that are moderately soluble in chloro-
form and dichloromethane. The crystalline bis(p-substi-
tuted benzoylmethyl)tellurides, (Y ¼ H (2a), Me (2b),
MeO (2c)) are stable only for a couple of hours at room
temperature, though they can be stored in solution at low
temperature for several days.
2RCOCH2Br þ Te ! ðRCOCH2Þ TeBr2
ð1Þ
2
1a; R¼Ph
In order to examine the generality of the synthetic
method [Eq. (1)] and the relevance of C–H–X hydrogen
bonds as a supramolecular force, the reaction of
p-substituted benzoylmethyl bromides with elemental
tellurium has been examined. The reduction of bis(aro-
ylmethyl)tellurium dibromides (p-YC6H4COCH2)2
TeBr2 to give the corresponding diorganotellurides (p-
YC6H4COCH2)2Te and their reactivity towards Br2, I2,
SO2Cl2 and CH2@CHCH2Br are also reported.
2. Result and discussion
The infrared spectra of the p-substituted benzoylm-
ethyl derivatives (p-YC6H4COCH2)2TeX2 (X ¼ Br (1),
Cl (3), I (4)) and (p-YC6H4COCH2)2Te (2) show a
negative shift of the m(CO) compared to that in the
parent benzoylmethyl bromide indicating intramolecu-
lar coordination of the carbonyl groups to the tellu-
rium atoms. Interestingly, no significant change in the
m(CO) is observed between the tellurium(IV) and tel-
lurium(II) compounds reported in Table 1. Also, the
larger negative shifts of m(CO) in case of 1c, 3c and 4c
indicate that the p-MeO ring substituted benzoylmethyl
group is a relatively stronger chelating agent than its
Me or H analogues which may be explained in terms of
delocalization of the lone pair on the methoxy oxygen
through the ring on to the carbonyl oxygen. The se-
lected NMR chemical shifts of compounds 1–4 are
listed in Table 1. A comparison of these data reveals
that the methylene protons in the tellurium(IV) species
are more deshielded than in the corresponding tellu-
rium(II) compounds. Surprisingly, the chemical shifts
are almost unaffected by the nature of the halide or the
substituent in para position. The 13C NMR spectrum
of the diorganotelluride 2a shows a downfield signal
for the carbonyl carbon (d 197.3 ppm) and an upfield
signal for methylene carbon (d 10.3 ppm), the latter
being different from the recently reported value (d 35.8
ppm) for 2a prepared by an alternative route [8]. Al-
though the chemical shift of the carbonyl C in 2a
closely resembles that of 1a (d 194.9 ppm), the upfield
shift of the resonance for the C atom attached to
tellurium(II) compound 2a as compared to that of
The reaction of p-substituted benzoylmethyl bro-
mides (p-YC6H4COCH2Br; Y ¼ H, Me, OMe) with
freshly ground tellurium powder occurs under gentle
heating to produce the corresponding diorganotellurium
dibromides (p-YC6H4COCH2)2TeBr2 (Y ¼ H (1a), Me
(1b), MeO (1c)) in high yields (Scheme 1). However, no
reaction occurred with p-XC6H4COCH2Br (X ¼ Cl, Br)
even upon heating to 100 °C for several hours, which
apparently demonstrates the importance of having ac-
tivating substituents in para-position of the benzoyl
group. The reaction of 1a–c with potassium iodide
afforded the corresponding diorganotellurium iodides
(p-YC6H4COCH2)2TeI2 (Y ¼ H (4a), Me (4b), MeO
(4c)) in high yields (Scheme 1), while the reduction of
1a–c with Na2S2O5, in a two phase system (organic/
aqueous) followed by a quick work-up of the reaction
mixture (to minimize decomposition to Te metal) [7],
Scheme 1.

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 689 (2004) 345–351
347
Table 1
Selected IR and NMR data for compounds 1–4
Compound
IR mCO (cmꢀ1
)
NMR chemical shifts (in ppm) in CDCl3
1H (CH2)
125Te
125Te (diso
)
(PhCOCH2)2TeCl2 (3a)
(PhCOCH2)2TeBr2 (1a)
(PhCOCH2)2TeI2 (4a)
1662a
1659b
1645b
1654
1646
1649
1645
1638
1636
1642d
1656
1647
1693
1685
1684
5.46c
5.45b
672
635
5.43b
f
(p-MeC6H4COCH2)2TeCl2 (3b)
(p-MeC6H4COCH2)2TeBr2 (1b)
(p-MeC6H4COCH2)2TeI2 (4b)
(p-MeOC6H4COCH2)2TeCl2 (3c)
(p-MeOC6H4COCH2)2TeBr2 (1c)
(p-MeOC6H4COCH2)2TeI2 (4c)
(PhCOCH2)2Te (2a)
5.41
5.45
681
675
667
661
f
5.45
5.41
4.26e
4.4
(p-MeC6H4COCH2)2Te (2b)
(p-MeOC6H4COCH2)2Te (2c)
PhCOCH2Br
4.22
4.46
4.44
p-MeC6H4COCH2Br
p-MeOC6H4COCH2Br
a (Lit. [6], 1660).
b (Earlier work [12]).
c (Lit. [6], 5.45, [8], 4.75).
d (Lit. [7], 1640).
e (Lit. [7], 4.26, [8], 4.53).
f Poor solubility.
tellurium(IV) in 1a (26.7 ppm) [12], is in accordance
with the expected enhanced shielding of the methylene
carbon in 2a. As such the previously reported signal at
35.8 ppm for the methylene carbon atom in 2a is in
contradiction with the enhanced shielding.
side. A possible explanation for this observation is the
high (pseudo) symmetrical environment around the tel-
lurium atoms, which is substantiated by X-ray crystal-
lography for 1a [12] and 1c. In addition, for all three
cases the 125Te MAS NMR signals are subject to second
order quadruple coupling with the bromine atoms.
However, due to the presence of two magnetically in-
equivalent bromine atoms and two different isotopomers
the extraction of coupling constants was not attempted.
Single crystal X-ray structures of 1a and 4a have been
reported previously by us [12]. Attempts to grow single
crystals of the remaining compounds described in this
work were only successful in the case of compound 1c.
The crystals obtained of the diorganotellurides 2a–c
crumble as soon as they are separated from the mother-
liquor. The ORTEP view and atom numbering of the
molecular structure of 1c is presented in Fig. 1 and se-
lected bond lengths, bond angles and torsion angles are
given in Table 2. (p-MeOC6H4COCH2)2TeBr2 (1c)
crystallizes in the orthorhombic crystal system and the
The proton-decoupled 125Te NMR solution spectra
of the three bis(p-substituted benzoylmethyl)tellurium
dibromides 1a–c display a single resonance at d 672, 681
and 675, respectively. The chemical shifts are consider-
ably upfield as compared to those of the corresponding
bis(p-substituted phenyl)tellurium dichlorides (d 919–
931 ppm) [15]. The enhanced shielding may be due to (i)
intramolecular coordination of the carbonyl oxygens to
the tellurium atoms, (ii) the change from Te–aryl to Te–
alkyl and (iii) the difference between Te–Cl and Te–Br.
The 125Te MAS NMR chemical shifts of 1a–c (d 635,
667 and 661, respectively) compare reasonably well with
the values observed in CDCl3 solution. It is interesting
to note that the isotropic chemical shifts are accompa-
nied by only one set of small spinning sidebands on each
Fig. 1. Crystal structure of 1c.

348
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 689 (2004) 345–351
Table 2
Selected bond lengths and angles for (p-MeOC6H4COCH2)2TeBr2
ꢀ
Bond lengths (A)
Bond angles (°)
Te–C(1B)
Te–C(1A)
Te–Br(1)
2.132(4)
2.140(3)
2.6532(5)
2.6710(5)
2.840(3)
2.830(3)
1.211(4)
1.227(4)
C(1B)–Te–C(1A)
C(1B)–Te–Br(1)
C(1A)–Te–Br(1)
C(1B)–Te–Br(2)
C(1A)–Te–Br(2)
Br(1)–Te–Br(2)
95.35(13)
87.52(10)
88.09(10)
88.29(10)
88.76(10)
174.500(15)
117.2(3)
Te–Br(2)
Te–O(1A)
Te–O(1B)
O(1A)–C(2A)
O(1B)–C(2B)
C(6A)–O(6A)–C(61A)
C(6B)–O(6B)–C(61B)
C(2A)–C(1A)–Te
116.7(3)
104.4(2)
Torsion angles (°)
C(2B)–C(1B)–Te
105.1(2)
122.6(3)
119.7(3)
117.7(3)
122.2(3)
118.5(4)
119.3(3)
C(1B)–Te–C(1A)–C(2A)
C(1A)–Te–C(1B)–C(2B)
Te–C(1A)–C(2A)–O(1A)
Te–C(1B)–C(2B)–O(1B)
O(1A)–C(2A)–C(3A)–C(8A)
C(1A)–C(2A)–C(3A)–C(8A)
O(1A)–C(2A)–C(3A)–C(4A)
C(1A)–C(2A)–C(3A)–C(4A)
O(1B)–C(2B)–C(3B)–C(8B)
C(1B)–C(2B)–C(3B)–C(8B)
O(1B)–C(2B)–C(3B)–C(4B)
C(1B)–C(2B)–C(3B)–C(4B)
)168.0(2)
170.1(2)
4.1(4)
O(1A)–C(2A)–C(3A)
O(1A)–C(2A)–C(1A)
C(3A)–C(2A)–C(1A)
O(1B)–C(2B)–C(3B)
O(1B)–C(2B)–C(1B)
C(3B)–C(2B)–C(1B)
)0.9(4)
)2.4(5)
177.9(3)
177.1(3)
)2.6(5)
0.6(5)
)178.9(3)
)179.6(4)
0.9(5)
Hydrogen bond parameters
D–Hꢁ ꢁ ꢁA
ꢀ
ꢀ
ꢀ
d(D–H) (A)
0.98
0.98
d(Hꢁ ꢁ ꢁA) (A)
d(Dꢁ ꢁ ꢁA) (A)
\(DHA) (°)
143.1
111.9
C(61A)–H(61C)ꢁ ꢁ ꢁO(1A)#1
C(61B)–H(61E)ꢁ ꢁ ꢁO(1B)#2
C(61A)–H(61B)ꢁ ꢁ ꢁO(6B)#3
C(61B)–H(61F)ꢁ ꢁ ꢁO(6A)#3
2.45
2.48
2.47
2.68
3.289(5)
2.984(5)
3.319(5)
3.499(5)
0.98
0.98
145.4
141.8
Symmetry transformations used to generate equivalent atoms: #1: x ꢀ 1=2, ꢀy þ 5=2, ꢀz; #2: ꢀx þ 2, y þ 1=2, ꢀz ꢀ 1=2; #3: x þ 1=2, ꢀy þ 7=2,
ꢀz.
P212121 space group (cf. (PhCOCH2)2TeX2; X ¼ Br, I:
coordination number in organotellurium compounds
with the help of inter- and intra-molecular Te–X
(X ¼ halogen, N, O, S) secondary interactions. Fur-
thermore, it has been observed that the 5 + 2 coordina-
tion geometry (5 equatorial neighbours including the
lone pair and 2 apical neighbours) about the central
tellurium atom is the most frequently encountered
amongst six coordinate diorganotellurium dihalides [11].
The geometry of 1c is no exception to this showing in-
tramolecular coordination of both carbonyl O atoms
monoclinic crystal system with P21=n space group) with
four molecules per unit cell. The asymmetric unit reveals
only one crystallographically independent molecule,
which is consistent with the number of signals found in
the 125Te MAS NMR spectrum. In view of the steric
demand of the active lone pair, the primary geometry of
the tellurium atom may be described best as distorted
trigonal bipyramidal. The distortion (though less than
that observed in case of 1a) is apparent from the reduced
bond angles Br1–Te–Br2 (174.5°) and C1A–Te–C1B
(95.35°) as against 180° and 120°, respectively, for
the idealized trigonal bipyramidal geometry. The
larger equatorial C–Te–C bond angle in (p-
MeOC6H4COCH2)2TeBr2 (1c) as compared to that of
(PhCOCH2)2TeBr2 (1a) (93.04°) indicates that Te–C
bonds in the former have relatively poorer p-character.
This would impart poorer s-character to the lone pair
resulting in a deshielding of the Te nucleus in 1c as
compared to 1a which is also corroborated by the ap-
pearance of downfield resonance signal in the solution
as well as in the solid state 125Te NMR spectra of 1c
when compared to that of 1a. Tellurium, owing to its
great propensity for secondary bonding, achieves higher
ꢀ
(Te–O distances: 2.840 and 2.830 A), which are both
ꢀ
longer than the sum of their covalent bond radii (2.03 A)
and significantly shorter than the sum of van der Waals
ꢀ
radii (3.60 A) [16]. Also, the tetrahedral bond angles Te–
C1A–C2A and Te–C1B–C2B have been reduced to
104.4° and 105.1°. The shorter Te–O distances in 1c
compared to 1a (2.938 and 2.917 A) indicate a stronger
ꢀ
Te–O interaction, which is also reflected in the lowering
of carbonyl stretching frequency in 1c compared to 1a.
The intramolecularly bonded carbonyl O atoms are
arranged cis to each other in the equatorial plane, both
at an angle of 54.5° to the adjacent Te–C bonds, pro-
viding sufficient space for the lone pair (bond angle
O1A–Te–O1B 149.6°). The octahedrally arranged six

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 689 (2004) 345–351
349
ligand atoms and slight deviation of the two O atoms
from the equatorial plane impart an almost perfect C2v
molecular geometry.
3. Experimental
3.1. General procedures
The remarkable feature of the solid-state structure of
(p-MeOC6H4COCH2)2TeBr2 (1c) is the presence of C–
H–O bonding interaction having a considerable elec-
trostatic contribution. Such interactions have been
proposed to be the dominant factor in assembling the
molecular units leading to a supramolecular structure
in organic [17] and nonorganic [18] crystals as well as in
crystalline organotellurium(IV) carboxylates [19]. The
chemically meaningful H–O distance, which is the
separation between CH of methoxy group (acting as H-
bond donor) and the O atom of the carbonyl/methoxy
group (H-bond acceptor) of neighboring molecules, lie
Benzoylmethyl bromides were prepared by bro-
mination of the corresponding acetophenones in gla-
cial acetic acid. The commercial tellurium powder
(Fluka) was washed with concentrated HCl and water
and dried at ꢂ120 °C. It was ground for ꢂ10 min just
before use. Solvents were purified and dried by stan-
dard methods. Melting points were recorded in capil-
lary tubes and are uncorrected. Wherever required the
reactions were carried out under dry nitrogen gas. The
1H and 13C NMR spectra were recorded at 300.13
and 50.32 MHz, respectively, in CDCl3 on a Varian
DRX 300 spectrometer using TMS as internal stan-
dard. Solution 125Te NMR were measured in CDCl3
at 85.2 MHz using a JEOL GX 270 MHz NMR
spectrometer and referenced against Me2Te. The 125Te
MAS NMR spectra were obtained at 126.2 MHz us-
ing a JEOL Eclipse Plus 400 MHz NMR spectrometer
equipped with a high speed locked 4 mm Bruker
Probe operating at spinning frequencies between 8 and
9 kHz. Experimental condition: pulse width 1 ms,
relaxation delay 120 s, 400–900 transients. The iso-
tropic chemical shifts were referenced against Me2Te
using solid Te(OH)6 as the secondary reference (diso
692.1, 685.5) [21]. IR spectra were examined as KBr
pellets using a Perkin–Elmer RX1 spectrometer. Ele-
mental carbon and hydrogen analyses were performed
on a Carlo Erbra 1108 make analyzer. Tellurium was
estimated volumetrically and the halogen content
gravimetrically as silver halide.
ꢀ
in the range between 2.45 and 2.68 A (Table 2). An H–
ꢀ
O distances of 2.80 A is taken as a cut off value for a
bonafide C–H–O bond in the case of 3d transition
metal carbonyl complexes [20]. The C–H–O hydrogen
bonding interaction has significant implications in
many diverse areas of structural chemistry and is, no
longer, considered an exoteric phenomenon. However,
for the first time such interactions among organotellu-
rium halides are shown to be a significant factor in the
self-organization of molecular units resulting in the
supramolecular structure (Fig. 2). From the crystal
packing pattern it is obvious that molecules of (p-
MeOC6H4COCH2)2TeBr2 (1c) are placed in pairs in
such a way that the lone pairs on the Te atoms are
facing opposite directions and the stacking of benzene
rings becomes feasible, thereby providing an opportu-
nity for attractive C–H–O hydrogen bonding as well as
p–p interactions, resulting in the stabilization of the
crystal lattice.
3.1.1. Synthesis of (p-YC6H4COCH2)2TeBr2 (Y ¼ CH3
(1b); OCH3 (1c))
A mixture of tellurium powder (1.28 g; 10 mmol)
and p-methylbenzoylmethyl bromide (4.69 g; 22 mmol)
was heated (ꢂ60 °C) with stirring until the mixture
solidified. Dichloromethane (10 ml) was added and
reaction mixture heated to reflux for 2 h. The solid
was filtered, washed with cold dichloromethane and
extracted with hot alcohol free chloroform. Concen-
tration of the extract and addition of pet-ether (40–60
°C) afforded crystalline 1b, yield, 2.80 g, (49%); m.p.
195 °C; Anal. Calc. for C18H18O2Br2Te: C, 39.0; H,
3.3; Br, 28.9; Te, 22.9. Found C, 39.2; H, 3.1;
Br, 28.7; Te, 21.9%. 1H NMR (CDCl3), (d ppm)
7.97–7.84(d), 7.34–7.29(d), 5.41(s), 2.57(s); IR; m(CO),
1646 cmꢀ1
.
1c was prepared similarly. Yield, 50%; m.p. 165 °C;
Anal. Calc. for C18H18O4Br2Te: C, 36.8; H, 3.1; Br,
27.3; Te, 21.8. Found C, 37.1; H, 2.9; Br, 26.9; Te,
1
21.4%. H NMR (CDCl3), (d ppm) 8.05–8.01(d), 7.04–
Fig. 2. Molecules of 1c connected through C–H–O hydrogen
bonds.
6.99(d), 5.45(s), 3.73(s); IR; m(CO), 1638 cmꢀ1
.

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A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 689 (2004) 345–351
3.1.2. Reduction of (p-YC6H4COCH2)2TeBr2 to (p-
YC6H4COCH2)2Te, (Y ¼ H (2a); CH3 (2b); OCH3
(2c))
Their melting points and IR spectra were similar
to those obtained by method (Section 3.1.4).
A solution of 1b (0.89 g, 1.6 mmol) in dichlorome-
thane (50 ml) was shaken with an aqueous solution of
Na2S2O5 (0.38 g, 2 mmol) for a few minutes. The or-
ganic layer gradually turned yellow. It was separated
and washed (3 ꢃ 20 ml) with water, dried over anhy-
drous Na2SO4 for about 10 min. Volatiles were removed
under reduced pressure and the residue was crystallized
from pet-ether to give yellow needles of 2b, which are
stable at low temperature. Yield, 2.39 g, (38%); m.p. 86
°C (Lit.[7] 95 °C); Anal. Calc. for C18H18O2Te: C, 54.9;
3.1.4. Halogen exchange/metathesis
A solution of 1b (0.54 g, 1 mmol) in chloroform was
stirred with 1.5-fold excess of KI for 2 h. The orange
coloured reaction mixture was filtered. Concentration of
the filtrate and addition of pet-ether afforded 4b as red/
brown crystals. Yield, 0.44 g, (70%); m.p. 145 °C; Anal.
Calc. for C18H18O2I2 Te; C, 33.4; H, 2.8; I, 39.2; Te,
19.7. Found C, 33.1; H,2.6; I, 39.1; Te, 19.0%. 1H NMR
(CDCl3, d ppm) 7.95–7.85(d), 7.36–7.30(d), 5.45(s),
4.36(s); IR: m(CO), 1649 cmꢀ1
.
1
H, 4.6; Te, 32.4. Found C, 54.6; H, 4.3; Te, 33.3%. H
4c was obtained similarly. Yield, (72%); m.p. 150 °C;
Anal. Calc. for C18H18O4I2 Te; C, 31.8; H, 2.7; I, 39.2;
NMR (CDCl3), (d ppm) 8.05–8.02(d), 7.44–7.43(d),
4.40(s), 2.60(s).
1
Te, 19.6. Found C, 31.5; H, 2.7; I, 38.2; Te, 18.9%. H
NMR (CDCl3, d ppm) 8.03–8.01(d), 7.05–7.02(d),
2a and 2c were prepared similarly. 2a, Yield, (40%);
m.p. 76 °C (Lit. [7], 79 °C); Anal. Calc. for C16H14O2Te:
C, 52.5; H, 3.9; Te, 34.9. Found C, 52.2; H, 3.7; Te,
5.41(s), 3.95(s); IR: m (CO), 1636 cmꢀ1
.
1
34.5%. H NMR (CDCl3), (d ppm) 7.98–7.96(d), 7.58–
3.1.5. Attempted oxidative addition of allyl bromide to 2a
Allyl bromide (1 ml) in pet-ether (10 ml) was added
slowly to a stirred solution of freshly prepared 2a (0.79 g;
2 mmol) in the same solvent (30 ml) with stirring. A white
solid gradually formed, which after 2 h was collected by
filtration, washed with pet-ether and characterized as 1a.
Yield: 1 g, (85%); m.p. 182 °C. Likewise 2b and 2c af-
forded 1b and 1c, respectively, in over 80% yield.
7.55(t), 7.50–7.45(t), 4.26(s); 13C NMR (CDCl3), (d
ppm) 197.3, 135.0, 133.3, 128.6, 10.3. IR: m(CO), 1642
cmꢀ1. 2c, Yield (32%); m.p. 66 °C (Lit [7], 67 °C); Anal.
Calc. for C18H18O4Te; C, 50.8; H, 4.2; Te, 30.0. Found
1
C, 50.6; H, 3.9; Te, 29.3%. H NMR (CDCl3), (d ppm)
7.98–7.95(d), 6.95–6.92(d), 4.22(s), 3.88(s); IR: m(CO),
1647 cmꢀ1
.
3.1.3. Oxidation of (p-YC6H4COCH2)2Te (2) with Br2,
I2 and SO2Cl2
3.2. X-ray crystallography
(a) Freshly prepared 2a (0.35 g, 1 mmol) was dissolved
in pet-ether (20 ml) and cooled at 0 °C. A solution of
bromine (0.18 ml, 1.2 mmol) in CCl4 was slowly
added with stirring. After the complete addition,
the reaction mixture was gradually warmed to room
temperature and stirred for 2 h. A light yellow col-
ored solid separated which was filtered, dried and re-
crystallized with CHCl3/pet-ether to give 1a. Yield,
0.43 g, (85%); m.p. 182 °C (Lit. [12], 182–184 °C),
IR: m(CO), 1659 cmꢀ1 (Lit. [12]), 1659 cmꢀ1. 1b
and 1c were prepared similarly from 2b and 2c, re-
spectively, and their melting points and IR spectra
were similar to those obtained by method (Section
3.1.1).
(b) Sulfuryl chloride (0.5 ml) was added dropwise with
stirring to a solution of 2a (0.35 g, 1 mmol) in di-
chloromethane at 0 °C. The reaction mixture was al-
lowed to come to the room temperature and stirred
for 15 min. Concentration under reduced pressure
and addition of pet-ether afforded colourless crystal-
line 3a. Yield, 0.33 g, (81%); m.p. 195 °C (Lit. [7,8],
195–197 °C). 3b. Yield, 80%; m.p. 212–214 °C (Lit.
[7], 213–215 °C) and 3c. Yield, 75%; m.p. 195–196
°C (Lit. [7], 197 °C) were obtained similarly.
(c) The iodides, 4a, 4b and 4c were prepared by using io-
dine and the corresponding 2 as in Section 3.1.3a.
Needle shaped white single crystals of (p-
MeOC6H4COCH2)2TeBr2 (1c) suitable for diffraction
studies were obtained by slow cooling of its dichlo-
romethane solution. The X-ray diffraction measure-
ments were performed at 93(2) K Bruker P4S
diffractometer employing graphite monochromated Mo
ꢀ
Ka radiation (k ¼ 0:71073 A) to a maximum of
hmax ¼ 29:19° via x scan (completeness 92.4% to hmax).
A total of 15,425 reflections were collected and the data
were reduced and corrected for absorption using SAD-
ABS program. The structure was solved by direct
methods and difference Fourier synthesis using SHELX-
97 implemented in the WIN GX 2002 [22]. The non-
hydrogen atoms were refined anisotropically while the
hydrogen atoms, introduced on calculated positions,
were refined isotropically. An acceptance criterion of
I > 2rðIÞ was used and the final cycle of full-matrix least
squares refinement based on 4878 independent reflec-
tions and 228 parameters converged with unweighted
(R1) and weighted (wR2) agreement factors of 0.0255 and
0.0538, respectively. Flack parameter Lattice parameters
and structure solution of the title compound are:
C18H18Br2O4Te, M ¼ 585:74, orthorhombic, P212121,
ꢀ
ꢀ
ꢀ
a ¼ 5:6210ð7Þ A, b ¼ 13:6545ð17Þ A, c ¼ 25:608ð3Þ A,
V ¼ 1965:4ð4Þ A , Z ¼ 4, Dx ¼ 1:980 M g/m3,
3
ꢀ
F ð000Þ ¼ 1120, l ¼ 5:598 mmꢀ1. The maximum and

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 689 (2004) 345–351
351
[6] D.G. Marsh, J.Y.C. Chu, J.W. Lewicki, J.L. Weaver, J. Am.
Chem. Soc. 98 (1975) 8432.
minimum residual electron densities were 0.539 and
ꢀꢀ3
)0.753 e A while the value for the Flack parameter is
0.0124 with 0.0074 esd.
[7] L. Engman, Organometallics 6 (1986) 427.
[8] A.Z. Al-Rubaie, L.Z. Yousif, A.K. Al-BaÕaj, J. Organomet.
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Synthesis (1987) 1096.
4. Supplementary material
[10] I. Haiduc, R.B. King, H.B. Newton, Chem. Rev. 1094 (1994)
301.
Crystallographic data for the structure analysis has
been deposited with the Cambridge Crystallographic
Data Center, CCDC No. 209756 for bis(4-meth-
oxybenzoylmethyl)tellurium dibromide (1c). Copies of
this information may be obtained free of charge from the
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK. Fax: +44-1223-336-033; or E-mail: deposite@ccdc.
cam.ac.uk or www:http://www.ccdc.cam.ac.uk.
[11] I. Haiduc, J. Zuckerman-Schpector, Phosphorous, Sulfur and
Silicon 171 (2001) 171.
[12] A.K.S. Chauhan, A. Kumar, R.C. Srivastava, R.J. Butcher,
J. Organomet. Chem. 658 (2002) 169.
[13] (a) A.Z. Al-Rubaie, W.R. McWhinnie, S. Chapelle, J. Orgnomet.
Chem. 234 (1982) 287;
(b) R.H. Jones, T.A. Hamor, J. Orgnomet. Chem. 234 (1982)
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Acknowledgements
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(1980) 417.
We are thankful to the Department of Science and
Technology, Government of India and the Australian
Research Council (ARC) for financial support.
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