Secondary bonding in functionalized organotellurium compounds: Preparation and structural characterization of bis(acetamido)tellurium(IV) diiodide and bis(4-methylbenzoylmethyl)tellurium(II)

Article abstract of DOI:10.1016/j.jorganchem.2004.09.036

Elemental tellurium inserts, under mild conditions, between C-I bond of iodoacetamide to afford bis(acetamido)tellurium(IV) diiodide (NH ₂COCH₂)₂TeI₂, 1. Heating of N-bromomethylphthalimide with activated tellur

Full text of DOI:10.1016/j.jorganchem.2004.09.036

Journal of Organometallic Chemistry 690 (2005) 313–321
www.elsevier.com/locate/jorganchem
Secondary bonding in functionalized organotellurium
compounds: preparation and structural characterization of
bis(acetamido)tellurium(IV) diiodide and
bis(4-methylbenzoylmethyl)tellurium(II)
a,
a
a
Ashok K.S. Chauhan *, Anamika , Arun Kumar ,
a
Ramesh C. Srivastava , Ray J. Butcher
b
a
Department of Chemistry, University of Lucknow, Lucknow 226 007, India
Department of Chemistry, Howard University, Washington, DC 20059, USA
b
Received 5 August 2004; accepted 15 September 2004
Available online 14 October 2004
Abstract
Elemental tellurium inserts, under mild conditions, between C–I bond of iodoacetamide to afford bis(acetamido)tellurium(IV)
diiodide (NH2COCH2)2TeI2, 1. Heating of N-bromomethylphthalimide with activated tellurium powder however, resulted in the
formation of bis(phthalimido)methane, 2, instead of the expected product bis(phthalimidomethyl)tellurium(IV) dibromide. The
IR spectrum of 1 is indicative of intramolecular Teꢀ ꢀ ꢀO@C interaction which is also substantiated by its single-crystal structure.
The compound with planar small-bite chelating organic ligands acquires butterfly shape that imparts almost perfect C2v molecular
symmetry but unlike other organotellurium(IV) iodides, the solid state structure of 1 is devoid of any intermolecular Teꢀ ꢀ ꢀI or Iꢀ ꢀ ꢀI
secondary interactions owing to the presence of intramolecular Teꢀ ꢀ ꢀO secondary bonds as well as intermolecular N–Hꢀ ꢀ ꢀO, N–
Hꢀ ꢀ ꢀI and C–Hꢀ ꢀ ꢀI hydrogen bonds. Bis(4-methylbenzoylmethyl)telluride (4-MeC6H4COCH2)2Te, 3b, prepared by the reduction
of the corresponding dibromide, is the first structurally characterized acyclic dialkyltelluride and interestingly, does not involve
intramolecular Teꢀ ꢀ ꢀO@C interaction invariably present in the parent dihalides (4-YC6H4COCH2)2TeX2 (Y = H, X = I 4a;
Y = H, X = Br 5a; Y = MeO, X = Br 5c). Weak intermolecular Teꢀ ꢀ ꢀTe and C–Hꢀ ꢀ ꢀO hydrogen bonds appear to be the non cova-
lent intermolecular associative forces that dominate its crystal packing in the solid state of this Te(II) derivative. The dialkyltellu-
rides (4-YC6H4COCH2)2Te, (Y = H, 3a, Me, 3b) undergo oxidation in presence of (SCN)2 to give the corresponding
bis(isothiocyanato)tellurium(IV) derivatives and form 2:1 adducts with Pt(II) and Pd(II) chlorides.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Functionalized organotelluriums; Intramolecular coordination; Secondary interactions
1. Introduction
pounds is invariably pseudo trigonal bipyramidal with
two Te–C bonds and the stereochemically active lone
pair of electrons occupying the equatorial sites and
the two halogen atoms occupying the apical sites [1].
The presence of ubiquitous intermolecular Teꢀ ꢀ ꢀX (hal-
ogen) interactions in the non functionalized diorgano-
tellurium(IV) dihalides [2] and their significance in
supramolecular association and crystal engineering
have been surveyed recently [3]. However, if an organic
Solid state structural studies on diorganotellu-
rium(IV) dihalides indicate that the primary geometry
about Te atom in these monomeric covalent com-
*
Corresponding author. Tel.: +91 9415010763; fax: +91 522
2740245.
E-mail address: akschauhan@hotmail.com (A.K.S. Chauhan).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.09.036

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A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 313–321
ligand is functionalized to bear a nucleophillic atom A,
viz. N, O, S, Cl or Br, chelation via Teꢀ ꢀ ꢀA secondary
interactions affects the stability, chemical reactivity [4]
and biological activity [5] significantly. Even an ionic
structure [Ph(2-Me2NCH2C6H4)TeX]+Xꢁ for [2-
((dimethylamino)methyl)phenyl]phenyltellurium dibro-
mide/iodide involving stabilization of asymmetric
telluronium cation by means of intramolecular Teꢀ ꢀ ꢀN
secondary interaction has been structurally character-
ized [6]. Among unsymmetrical diorganotellurium(IV)
dichlorides with ArRTeCl2 [7] or ArAr0TeCl2 [8] stoi-
chiometry (where R and Ar or Ar0 are the sp3 and
sp2-hybridized carbon-linked organic groups respec-
tively and only one is a small-bite O donor bidentate
ligand) intramolecular 1,4-type Teꢀ ꢀ ꢀO secondary inter-
action is preferred to intermolecular Teꢀ ꢀ ꢀCl secondary
interactions as the latter may or may not act as molec-
ular associative force to result in a supramolecular
structure. The recently determined solid state structures
of symmetrical bis(2,6-dimethoxyphenyl)tellurium diha-
lides [9] are however, devoid of any intermolecular
Teꢀ ꢀ ꢀX secondary interaction presumably, due to the
formation of intramolecular 4-membered rings by both
the organic ligands making the Te atom coordinatively
saturated.
of 1 in CDCl3 shows a singlet for methylene protons at
d 4.46 and another at d 7.74 due to NH2 protons. The
13C NMR spectrum of 1 consists of two singlets at d
168 for carbonyl and d 39 for methylene carbon atoms.
2.1. Crystal structure of bis(acetamido)tellurium(IV)
diiodide 1
The ORTEP view and atom numbering of the molec-
ular structure of compound 1 is shown in Fig. 1 and se-
lected interatomic distances, bond angles and torsion
angles are given in Table 1. (H2NCOCH2)2TeI2 crystal-
lizes in the monoclinic crystal system and the P21/n
space group with four molecules per unit cell and is iso-
morphous with (PhCOCH2)2TeX2, (X = Br, I) [10a].
The primary molecular geometry is pseudo-trigonal
bipyramidal with the two I atoms occupying apical posi-
tions. The stereochemical activity of the lone pair at one
of its equatorial corner is comparable to that observed
in case of other dialkyltellurium(IV) dihalides [10,11]
as the reduced equatorial C–Te–C and axial X–Te–X
angles for all such compounds lie within the narrow
ranges 93.04–96.63ꢁ and 172.47–174.50ꢁ, respectively.
Interatomic distances of Te atom from the amido O
˚
atoms (2.837 and 2.854 A) are short enough to qualify
In order to examine (a) the generality of the observa-
tion that the 1,4-type Teꢀ ꢀ ꢀO interactions give rise to
intramolecularly stabilized telluronium cations also in
the functionalized symmetrical diorganotellurium(IV)
dihalides ðRF2 TeX2; RF ¼ functionalized organic ligandÞ
and (b) if such intramolecular interactions are retained
in the corresponding diorganotellurides RF2 Te, we have
attempted [10] to prepare a number of RF2 TeX2 by the
insertion of tellurium across Csp3-X (X = Br, I) bond
(Eq. (1)) and study their solid state structures in compar-
ison to their reduction products RF2 Te.
for bonafide Teꢀ ꢀ ꢀO secondary interactions of apprecia-
ble strength. The acetamido groups attached to Te atom
thus behave as small-bite chelating ligands and adopt
cisoidal configuration about the central atom resulting
thereby in a pentagonal bipyramidal molecular geome-
try with one equatorial corner occupied by the lone pair.
Both the secondary bonded O atoms are almost copla-
nar with the C–Te–C equatorial plane and subtend an
angle O1A–Te–O1B of 156.14ꢁ, wide enough to accom-
modate the Te lone pair. Of particular interest is the
presence of nucleophillic atoms with lone pairs of elec-
trons in the region also occupied by the lone pair on
Te as per VSEPR theory and may be compared with
the presence of halogen atoms reported to be clustered
in this region in many organotellurium(IV) halides as
a result of intermolecular Teꢀ ꢀ ꢀX secondary bonds [1–
3]. Another significant feature of the molecular structure
of 1 is the planarity of –CONH2 fragments as evident
from the values of bond angles around N (each 120ꢁ)
and torsion angles involving H–N–C–O atoms (each
2RFAX þ Te ! RF2 TeX2
ð1Þ
In this paper structural characterization of bis(ace-
tamido)tellurium(IV) diiodide, 1 and bis(4-methyl-
benzoylmethyl)telluride, 3b, is described. Also included
in this communication are some observations on the
ligational behaviour of 3 and their oxidative reaction
with thiocyanogen.
2. Results and discussion
Elemental tellurium reacts with iodoacetamide at
ꢂ100 ꢁC in toluene to give mustered yellow coloured
crystalline bis(acetamido)tellurium(IV) diiodide, 1, in
quantitative yield. 1 is sparingly soluble in chloroform
and acetone. The IR spectrum shows m(CO) at 1651
cmꢁ1 which is shifted downfield with respect to the acet-
amide (1680 cmꢁ1) indicating coordination of the CO
1
group to Te(IV). The H NMR of a saturated solution
Fig. 1. ORTEP view of bis(acetamido)tellurium(IV) diiodide, 1.

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 313–321
315
Table 1
Selected interatomic distances (A) and angles (ꢁ) for bis(acetamido)tellurium(IV) diiodide, 1
˚
Te–C(1A)
O(1A)–C(2A)
2.137(7)
1.224(9)
2.8714(8)
1.292(11)
0.88
Te–C(1B)
O(1B)–C(2B)
2.117(7)
1.228(9)
Te–I(1)
N(1A)–C(2A)
Te–I(2)
N(1B)–C(2A)
2.9146(8)
1.317(10)
0.8800
N(1A)–H(1N1)
N(1A)–H(1N2)
Te–O(1A)
N(1B)–H(2N1)
N(1B)–H(2N2)
Te–O(1B)
0.88
2.839
0.8800
2.854
C(2A)–C(1A)–Te
C(1B)–Te–C(1A)
C(1B)–Te–C(1A)–C(2A)
Te–C(1A)–C(2A)–O(1A)
Te–C(1A)–C(2A)–N(1A)
104.7(5)
95.9(3)
166.3(5)
8.3(9)
C(2B)–C(1B)–Te
I(1)–Te–I(2)
105.9(5)
172.72(2)
171.2(5)
ꢁ1.2(9)
ꢁ179.5(6)
C(1A)–Te–C(1B)–C(2B)
Te–C(1B)–C(2B)–O(1B)
Te–C(1B)–C(2B)–N(1B)
ꢁ171.7(7)
Hydrogen bond parameters
D–H–A
˚
˚
d(H–A) (A)
˚
d(H–A) (A)
d(D–H) (A)
0.88
0.88
Æ(DHA) (0)
148.2
129.2
N(1A)–H(1AC). . .O(1B)#1
N(1A)–H(1AC). . .I(1)#1
N(1A)–H(1AD). . .O(1B)#2
N(1B)–H(1BC). . .I(2)#3
N(1B)–H(1BD). . .O(1A)#4
C(1A)–H(1AB). . .I(1)#4
2.47
3.24
2.12
2.9
3.246(10)
3.861(8)
2.914(9)
3.734(7)
2.847(9)
3.977(8)
0.88
0.88
150.3
158.7
0.88
0.99
2.03
3.02
154.9
163.8
Symmetry transformations used to generate equivalent atoms: #1 ꢁx + 1/2, y + 1/2, ꢁz + 3/2; #2 x + 1/2, ꢁy + 1/2, zꢁ1/2; #3 ꢁxꢁ1/2, yꢁ1/2,
ꢁz + 3/2; #4 xꢁ1/2, ꢁy + 1/2, zꢁ1/2.
being close to 0ꢁ or 180ꢁ). This means the N atoms must
be sp2-hybridized. The C–N bond lengths 1.292(11) and
˚
1.317(10) A are also considerably shorter than the sum
of single bond covalent radii of Csp2 and N atoms
˚
(1.44 A) (cf. [12]).
The crystal packing pattern of 1 is presented in Fig. 2.
It depicts with dashes the contacts shorter than van der
Waalsꢀ and that can be characterized as hydrogen bonds
on the basis of parameters given in Table 1. The NH
protons being adjacent to a C@O group in the amido
fragment being sufficiently acidic form bifurcated
(three-center) hydrogen bonds [13] where a given proton
is held among the N donor and two acceptors, the O and
I from the neighboring molecules. A given carbonyl O
acceptor atom likewise, is also involved in two hydrogen
bonds simultaneously. The shorter N–H bond length
˚
0.88 A in comparison to the sum of the covalent radii
˚
(1.02 A) thus appears to be a manifestation of N–
Hꢀ ꢀ ꢀO/I hydrogen bonding. Likewise, CH groups
Fig. 2. Unit cell structure of bis(acetamido)tellurium(IV) diiodide, 1.
bonded to the sufficiently electropositive Te(IV)
atom being acidic enough cause C–Hꢀ ꢀ ꢀI hydrogen
bonds which possess the required linearity (ÆC–
Hꢀ ꢀ ꢀI = 163.8ꢁ) and donor–acceptor distance [inter-
is devoid of any intermolecular Teꢀ ꢀ ꢀI secondary bond-
˚
atomic d(H–I) = 3.016 A]. The significant importance
˚
ing as the shortest distance (4.96 A) between Te and I
atoms of any neighboring pair of molecules is greater
of relatively weak C–Hꢀ ꢀ ꢀX hydrogen bonds (where
X = F, O, N, Cl, Br, I) in the field of crystal engineering
has been recognized earlier [13]. The donor–acceptor
separation values in Table 1, indicate that N–Hꢀ ꢀ ꢀO
hydrogen bonds of moderate strength cooperated with
the relatively weak N–Hꢀ ꢀ ꢀI and C–Hꢀ ꢀ ꢀI hydrogen
bonds act as the molecular associative forces that result
in the centrosymmetric supramolecular assembly in the
solid state of the title compound. The crystal packing
˚
than the sum of their van der Waals radii (4.35 A). It
may thus be concluded that H-bonds are preferred to
Teꢀ ꢀ ꢀX secondary interaction as the bonding motif for
supramolecular self assembly in intramolecularly
bonded functionalized diorganotellurium dihalides.
Halogen exchange reactions of 1 with MX (M = K or
Ag; X = Cl, Br, N3, SCN) did not proceed probably due
to the insoluble nature of the reactants. In order to

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extend the solid state studies to functionalized diorgano-
tellurium(II) compounds, attempts were made to reduce
1 to (NH2COCH2)2Te with a variety of reducing agents.
Thus, NH2NH2 Æ xH2O and Na2S Æ 9H2O caused com-
plete reduction of 1 to elemental tellurium. Na2S2O5
did not react. Having failed to reduce 1 to the corre-
sponding telluride we turned our attention to bis(4-sub-
stituted benzoylmethyl)tellurides (4-YC6H4COCH2)2Te,
which were recently obtained in our laboratory by the
reduction of (4-YC6H4COCH2)2TeBr2. Since the diha-
lides (4-YC6H4COCH2)2TeX2, are characterized by the
presence of 1,4-type Te–O interactions, it appeared
interesting to examine if such an interaction is retained
in the (4-YC6H4COCH2)2Te.
Fig. 3. ORTEP view of bis(4-methylbenzoylmethyl)telluride, 3b.
2.2. Crystal structure of bis(4-methylbenzoylmethyl)tellu-
ride 3b
observed in case of tellurium(IV) derivatives 1, 5a
˚
and 5c (in the range 2.117–2.140 A) and that of the
˚
sum of single bond covalent radii (2.142 A) of Te
Among the known organotellurium(II) compounds
for which solid state structures have been determined,
leaving a cyclic telluride dibenzotelluraphene [14] and
a few alkyl aryl tellurides with RTeAr stoichiometry
[15], rest of the diaryltellurides Ar2Te and aryltellu-
rium(II) halide/pseudohalide ArTeX, are reported to
be stabilized by the presence of intramolecular 1,5-type
secondary interaction. In addition to 5-membered intra-
molecular ring formed by the functionalized organic lig-
and Ar, 1,4-type Te–O/S non bonded interactions have
also been observed in ArTeY compounds where Y is a
small-bite bidentate anionic group linked to Te(II)
through O or S atom, viz. carboxylate (RCOOꢁ) [16],
dithioxanthate (ROCSSꢁ) [17], dithiocarbamate
(R2NCSSꢁ) [18], dithiophosphate [(RO)2PSSꢁ] [17a,19]
or dithiophosphinate (R2 PSSꢁ) [19a,20]. We are not
aware of any 1,4-type intramolecular Te(II)–O(carbonyl
or ethereal) secondary interaction, though such an inter-
action involving only one of the carbonyl groups has
been reported in case of (PhCOCH2)2Se [21]. Moreover,
unlike diaryltellurides which are solids, dialkyltellurides
are generally malodorous liquids or low melting solids.
As such only one report on the crystal structure of a cy-
clo-alkyltelluride [22] and none on any acyclic dialkyltel-
luride has so far appeared. Our earlier attempts to grow
diffraction quality crystals of thermally and photo labile
dialkyltellurides 3, had failed. The yellow crystals grad-
ually turned blackish within a couple of hours at room
temperature. However, we have now observed that even
after a couple of weeks if these blackish crystals are
redissolved in pet. ether, filtered and allowed to crystal-
lize at low temperature a small crop (ꢂ20% of the orig-
inal) of yellow crystals can be recovered at least in case
of 3b.
and sp3-hybridized C atoms, but comparable to the
˚
average value of Te–C distances (2.17 A) reported
for 1-telluracyclohexane-3,5-dione [22], the only struc-
turally characterized compound where Te(II) is bonded
to sp3-hybridized C atoms. The 95.19(13)ꢁ value of C–
Te–C angle in 3b is reminiscent of the stereochemical
activity of the lone pairs on Te atom and is typical
of value observed for Ar2Te and RArTe [92.3(2)–
98.8(3)ꢁ] [4c,15,23]. The interesting feature of the struc-
ture of 3b is the insignificant intramolecular 1, 4-type
Teꢀ ꢀ ꢀO@C secondary interaction as is evident from
the interatomic distances between Te and the carbonyl
˚
oxygen atoms being 3.600 and 3.670 A. The other con-
sequences of the release of carbonyl O atoms from
intramolecular Teꢀ ꢀ ꢀO attractive non bonded interac-
tion in going from the functionalized dialkyltellu-
rium(IV) dihalides to their tellurides is (a) the
attainment of almost ideal tetrahedral angle at the
methylene C atoms [107.8(2)ꢁ and 108.7(2)ꢁ] and
(b) the complete loss of the planarity of the cisoidal
R2Te moiety observed in the corresponding diorgano-
tellurium(IV) derivatives, resulting therein the transoi-
dal orientation of the benzoyl fragments so as to
minimize the repulsion between lone pairs on the
carbonyl
compound.
O
atoms in the diorganotellurium(II)
It may be emphasized here that in spite of the absence
of any significant intramolecular Teꢀ ꢀ ꢀO@C interaction,
at least in the solid state, the m(CO) absorptions in the
infrared spectrum of 3 are observed at lower wave num-
bers (1656–1640 cmꢁ1) as compared to those in the parent
acetophenones (1697–1689 cmꢁ1) and their 2-bromo
derivatives (1693–1684 cmꢁ1). Thus, even a significant
negative shift of this frequency in case of the tellurides
with respect to the parent acetophenones or 2-bromoac-
etophenones cannot unequivocally be taken as an evi-
dence for Teꢀ ꢀ ꢀO@C coordination unless supported by
X-ray data. It is interesting to note that mCO for (PhC-
The ORTEP view of the molecular structure with
atom numbering is presented in Fig. 3 and selected
bond parameters are given in Table 2. The Te–C dis-
˚
tances 2.158(3) and 2.164(3) A are longer than those

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 313–321
317
Table 2
Selected interatomic distances (A) and angles (ꢁ) for bis(4-methylbenzoylmethyl)telluride, 3b
˚
Te–C(1A)
2.164(3)
1.220(4)
1.514(5)
1.500(5)
Te–C(1B)
2.158(3)
O(1A)–C(2A)
C(1A)–C(2A)
C(2A)–C(3A)
O(1B)–C(2B)
C(1B)–C(2B)
C(2B)–C(3B)
1.233(4)
1.501(5)
1.493(5)
C(2A)–C(1A)–Te
C(1B)–Te–C(1A)
107.8(2)
95.19(13)
C(2B)–C(1B)–Te
108.7(2)
C(1A)–Te–C(1B)–C(2B)
Te–C(1A)–C(2A)–O(1A)
O(1A)–C(2A)–C(3A)–C(4A)
O(1A)–C(2A)–C(3A)–C(9A)
ꢁ90.4(2)
94.8(3)
C(1B)–Te–C(1A)–C(2A)
Te–C(1B)–C(2B)–O(1B)
O(1B)–C(2B)–C(3B)–C(4B)
O(1B)–C(2B)–C(3B)–C(9B)
ꢁ75.5(2)
ꢁ87.0(3)
ꢁ162.5(3)
16.1(5)
ꢁ175.2(3)
6.3(5)
Hydrogen bond parameters
D–H–A
˚
˚
d(H–A) (A)
d(D–H) (A)
0.99
0.98
Æ(DHA) (ꢁ)
158.6
158.8
C(1A)–H(1AB). . .O(1B)#1
C(1A)–H(1AB). . .O(1B)#1
2.46
2.56
3.401(4)
3.495(5)
Symmetry transformations used to generate equivalent atoms: #1 ꢁx + 1/2, yꢁ1/2, ꢁz + 1/2.
OCH2)2S (1690 cmꢁ1), (PhCOCH2)2Se (1670 cmꢁ1) [24]
and (PhCOCH2)2Te (1642 cmꢁ1) [10b] decrease with
increasing mass of the chalcogen.
2.3. Reactions of bis(4-substituted benzoylmethyl)tellu-
rides 3
The crystal packing pattern of 3b is shown in Fig. 4.
2.3.1. Reactions of 3 with pseudohalogen (SCN)2
Oxidative addition of dihalogens to 3 has been re-
ported earlier [10b]. Thiocyanogen reacts with 3a and
3b at 0 ꢁC to afford yellowish oxidative addition prod-
ucts (4-YC6H4COCH2)2Te(SCN)2, which are sparingly
soluble in common organic solvents. The m(CN) absorp-
tion appears below 2100 cmꢁ1 in their IR spectra which
indicates these to be N-bonded [26] isothiocyanto deriv-
atives. The broader shape of m(CN) absorption with a
shoulder, insolubility and colour of the compounds
probably hint at some molecular association via weak
Te–S bonds formed by the bridging thiocyanate groups
in the solid state of these functionalized dialkyltellu-
rium(IV) diisothiocyantes.
˚
The Te–Te interatomic distance 4.147 A between a pair
of molecules is shorter than the sum of their van der
˚
Waals radii (4.40 A). At the same time H-bond param-
eters given in Table 2, clearly indicate the presence of C–
H–O hydrogen bonds formed by the carbonyl O atoms
(as H-bond acceptors) and C of methylene or methyl
groups (as H-bond donors). The shortest distance be-
tween tellurium and the centroid of any aromatic ring
that has been observed in the crystal packing is 4.057
˚
A. The distance is too long to account for the presence
of any significant Te–p (aryl) secondary interaction as
a bonding motif for supramolecular assembly [25]. The
solid state structure of compound 3b thus appears to
consist of dimeric units formed by means of a Teꢀ ꢀ ꢀTe
secondary interaction and a (methylene)C–Hꢀ ꢀ ꢀO (car-
bonyl) H-bond which in turn are linked into chains via
(methyl)C–Hꢀ ꢀ ꢀO (carbonyl) H-bonds that give rise to
centrosymmetric supramolecular structure.
2.3.2. Reactions of 3 with Pt(II) and Pd(II) chlorides
Non-functionalized cyclic and acyclic diorganotellu-
roethers (R2Te) behave as monodentate ligands and
form 1:2 complexes with d8 and d10 metal centers. (Te,
N) or (Te, O) hybrid telluroethers often form 1:1 com-
plexes with d8 metal centers in which both the ligating
atoms coordinate the central metal atom [27]. As the
dialkyltellurides 3, possess both hard and soft donor
centers and the carbonyl oxygen atoms are not involved
in intramolecular coordination, their ligational behavior
towards Pt(II) and Pd(II) chlorides has been examined.
Brown/yellow adducts MCl2 Æ 2R2Te, as evident from
elemental analyses, are obtained when a solution of
diketonic telluroethers 3, in dichloromethane is added
to a solution of MCl2(PhCN)2 (M = Pt, Pd). The ad-
ducts are only sparingly soluble in chloroform, acetone
and alcohol. The IR spectra of the adducts show
m(CO) at 1645–1668 cmꢁ1 which is ꢂ8 cmꢁ1 higher than
for the corresponding free telluroether ligand 3. The
1
Fig. 4. Unit cell structure of bis(4-methylbenzoylmethyl)telluride, 3b.
deshielding of the methylene protons in the H NMR

318
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 313–321
spectra of the adducts (wherever meaningful spectra of
saturated solutions could be obtained) indicate the
monodentate behavior of 3 with only Pt/Pd–Te interac-
tion in the adducts.
recorded at 300.13 and 50.32 MHz, respectively, in
CDCl3 on a Varian DRX 300 spectrometer using TMS
as internal standard. IR spectra were examined as KBr
pellets using a Perkin–Elmer RX1 spectrometer. Fast
atom bombardment (FAB) mass spectrum of 1 was re-
corded on a JEOL SX 102/DA-6000 Mass Spectrome-
ter/Data System using Argon/Xenon (6 kV, 10 mA) as
the bombarding gas. The accelerating voltage was 10
kV and m-nitrobenzyl alcohol was used as the matrix.
Elemental carbon, hydrogen and nitrogen analyses were
performed on a Carlo Erba 1108 make analyzer. Tellu-
rium was estimated volumetrically and the halogen con-
tent gravimetrically as silver halide. The preparation of
bis(p-substituted benzoyl methyl)tellurides has been re-
ported elsewhere [10b].
2.4. Reactions of elemental Te with other functionalized
halomethyl organic substrates
N-Bromomethylphthalimide in refluxing toluene does
not react with Te powder but when heated (ꢂ150 ꢁC) to-
gether in absence of a solvent afforded crystalline
bis(phthalimido)methane 2 and other unidentified non-
tellurium containing product(s) (see Section 3). A plau-
sible mechanism for the formation of 2 is given in
Scheme 1 and is based on the observation that the par-
ent phthalimide remains unaffected when heated in ab-
sence of Te and the general lability of RTeX species
and Te–N bonds. The colourless crystals of compound
2 melt at 230 ꢁC and are soluble in common organic sol-
vent. The IR spectrum shows m(CO) at 1732 cmꢁ1 which
is very close to that observed in case of N-bromo-
3.1.1. Synthesis of bis(acetamido)tellurium(IV) diiodide
1
A mixture of activated tellurium powder (0.65 g, 5
mmol) and iodoacetamide (1.85 g, 10 mmol) in 3 ml tol-
uene was heated (ꢂ100 ꢁC) with stirring till all the tellu-
rium was consumed. The resulting yellow paste was
freed from toluene by decantation and washing with
ether. The residue was extracted with hot acetone. The
solvent was removed under reduced pressure and the
residue was recrystallized from acetone to give yellow
needles of 1. Yield (2.3 g, 92%); m.p. 152 ꢁC; Anal.
Found: C, 9.62; H, 1.58; N, 5.53; I, 50.50; Te, 24.90.
Calc. for C4H8N2O2I2Te: C, 9.65; H, 1.66; N, 5.63; I,
51.01; Te, 25.64%. IR (m/cmꢁ1), 1650 (CO), 3259 (N–
1
methylphthalimide 1728 cmꢁ1. The H NMR spectrum
consists of a singlet at d 5.46 for methylene protons
and two multiplets at d 7.73 and d 7.86 for the aryl
protons.
Both, N-bromoethylphthalimide and 2-bromoethanol
failed to react with Te in the sense of Eq. (1) up to 100
ꢁC even in presence of NaI which shows that it is imper-
ative for a functional group to be present at the a-car-
bon atom for the insertion of Te (Eq. (1)) to take
place. Iodoacetic acid also failed to react as it sublimes
out (ꢂ50 ꢁC) before it could react with Te powder.
1
H); H NMR (d ppm), 7.74 (4H, s, 2NH2), 4.46 (4H,
s, 2CH2); 13C NMR, (d ppm), 167.97 (CO), 38.92
(CH2); FAB mass, m/z 373 (M+ ꢁ I for 130Te with char-
acteristic isotopomeric pattern).
3. Experimental
3.1.2. Oxidative addition of (SCN)2 to (4-YC6H4CO-
CH2)2 Te (Y = H 3a, Me 3b)
3.1. General
(C6H5COCH2)2Te(NCS)2. A freshly prepared solu-
tion of (SCN)2 [obtained by the reaction of Pb(SCN)2
with Br2 in CCl4] (0.145 g, 1.25 mmol) in CCl4 (20 ml)
was slowly added to the solution of (C6H5COCH2)2Te
(0.35 g, 1 mmol) in the same solvent under stirring at
0 ꢁC. White product separated during addition. It was
stirred for ꢂ1 h and filtered and washed 4 times with
CCl4. Light yellow colored product was recrystallized
from CH2Cl2 to give (C6H5COCH2)2Te(NCS)2. Yield
(0.33 g, 64%); m.p. 120 ꢁC; Anal. Found: C, 44.39; H,
The commercial tellurium powder (Fluka) was acti-
vated by washing with conc. HCl and water and drying
at 120 ꢁC. It was grinded for 15 min just before use.
Iodoacetamide, N-(2-bromoethyl)phthalimide, N-brom-
omethylphthalimide, 2-bromoethanol and iodoacetic
acid were used as received. PtCl2(PhCN)2 and
PdCl2(PhCN)2 were prepared by standard methods.
Whenever required the reactions were carried out under
dry N2 atmosphere. The 1H and 13C NMR spectra were
R2NCH2Br
[R2NCH2-Te-NR2]
Te
R2NCH2Br
[R2NCH2-Te-Br]
+
- CH2Br2
O
C
-Te
N
R2N=
R2N-CH2-NR2
C
O
2
Scheme 1.

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 313–321
319
2.64; N, 5.90; Te, 27.30. Calc. for C18H14O2S2N2Te: C,
44.85; H, 2.93; N, 5.81; Te, 26.47%. IR (m/cmꢁ1),
1683.2 (CO), 2001.0 (NCS); H NMR (d ppm), 7.99–
7.44 (10H, m, 2 Ar), 4.77 (4H, s, 2CH2).
vapors were deposited at the wall of the flask and the
reaction mixture became dark solid. It was cooled and
5 ml toluene was added. After refluxing for 15 min the
solid dissolved to give yellowish transparent solution
and a little black solid indicating consumption of most
of the Te powder. Workup of the reaction mixture by
distilling off the solvent and washing the residue with
chloroform, however, gave Te powder (0.21 g). The fil-
trate, after concentration and addition of pet-ether,
was cooled to 0 ꢁC. Colourless crystals of bis(phthalim-
ido)methane, 2, were separated. Yield, (0.20 g); m.p. 230
ꢁC; Anal. Found: C, 67.01; H, 3.21; N, 9.50. Calc. for
C17H10N2O4: C, 66.70; H, 3.26; N, 9.15%. IR(m/cmꢁ1),
1732.1 (CO); 1H NMR (d ppm), 7.88–7.70 (8H, m,
2Ar), 5.64 (2H, s, CH2). Concentration of the mother
liquor afforded yellow solid (0.25 g) of variable compo-
sition and melting point.
1
(4-MeC6H4COCH2)2Te(NCS)2 was prepared simi-
larly from (4-MeC6H4COCH2)2Te and (SCN)2. Yield
(60%); m.p. 98 ꢁC; Anal. Found: C, 47.67; H, 3.14; N,
5.32; Te, 24.67. Calc. for C20H18O2S2N2Te: C, 47.09;
H, 3.56; N, 5.49; Te, 25.01%. IR (m/cmꢁ1), 1650.7
1
(CO), 2067.9 (NCS); H NMR (d ppm), 7.93-7.31 (8H,
m, 2 Ar), 4.73 (4H, s, 2CH2), 2.45 (6H, s, 2CH3).
3.1.3. Reaction of (4-YC6H4COCH2)2Te (Y = H, Me,
MeO) 3 with MCl2 Æ ( PhCN)2 (M = Pt and Pd)
PtCl2[(C6H5COCH2)2Te]2. To
a
solution of
[PtCl2(PhCN)2] (0.47 g, 1.0 mmol) in CH2Cl2 (20 ml)
was added to a solution of (C6H5COCH2)2Te (0.73 g,
2.0 mmol) in the same solvent slowly. On the basis of
TLC monitoring the reaction was completed in 14 h.
The reaction mixture was concentrated and addition of
pet-ether afforded the 1:2 complex, Yield (0.60 g,
60%); m.p. 164 ꢁC; Anal. Found: C, 38.28; H, 2.68;
Te, 24.60. Calc. for C32H28O4Cl2Te2 Pt: C, 38.52; H,
The parent N-bromomethylphthalimide remained
unaffected when heated in absence of Te powder under
similar conditions.
3.2. X-ray crystallography
The conditions to grow suitable crystals of 1 and 3b
for crystallographic studies are given at appropriate
places in the result and discussion section. The X-ray
diffraction measurements were performed at 103(2) K
using a Bruker PS4 diffractometer employing graphite
1
2.82; Te, 25.57%. IR (m/cmꢁ1), 1657.7 (CO); H NMR
(d ppm), 7.7 (20H, m, 4 Ar), 2.60 (8H, s, 4CH2).
The following adducts were prepared similarly.
PtCl2[(4-MeC6H4COCH2)2Te]2, Yield (81%); m.p.
186 ꢁC; Anal. Found: C, 41.30; H, 3.54; Te, 24.81. Calc.
for C36H36O4Cl2Te2Pt: C, 41.03; H, 3.44; Te, 24.21%. IR
(m/cmꢁ1), 1663.4 (CO); 1H NMR (d ppm), 7.93–7.33
(16H, m, 4 Ar, 5.29 (8H, s, 4CH2), 2.46 (12H, s, 4CH3).
PtCl2[(4-MeOC6H4COCH2)2Te]2, Yield (55%);
m.p. 190 ꢁC; Anal. Found: C, 38.50; H, 3.02; Te,
22.21. Calc. for C36H36O8Cl2Te2Pt: C, 38.68; H, 3.24;
Te, 22.81%. IR (m/cmꢁ1), 1668.7 (CO).
˚
monochromated Mo Ka radiation (k = 0.71073 A). De-
tails of the crystallographic parameters for compounds 1
and 3b are given in Table 3. The structures were solved
by direct methods (SIR92) [28] and expanded using
Table 3
Crystallographic data for compounds 1 and 3b
PdCl2[(C6H5COCH2)2Te]2, Yield (70%); m.p. 178
ꢁC; Anal. Found: C, 42.55 ; H, 2.86; Te, 27.40. Calc.
for C32H28O4Cl2Te2Pd: C, 42.28; H, 3.10; Te, 28.07%.
IR (m/cmꢁ1), 1658.0 (CO); 1H NMR (d ppm), 7.97–
7.45 (20H, m, 4 Ar), 4.65 (8H, s, 4CH2).
PdCl2[(4-MeC6H4COCH2)2Te]2, Yield (72%); m.p.
186–189 ꢁC; Anal. Found: C, 44.60; H, 3.56; Te,
25.60. Calc. for C36H36O4Cl2Te2Pd: C, 44.80; H, 3.76;
Te, 26.43%. IR (m/cmꢁ1), 1653.2 (CO).
PdCl2[(4-MeOC6H4COCH2)2Te]2, Yield (48%);
m.p. 188-195 ꢁC; Anal. Found: C, 41.86; H, 3.70; Te,
23.48. Calc. for C36H36O8Cl2Te2Pd: C, 42.01; H, 3.52;
Te, 24.78%. IR (m/cmꢁ1), 1645.2 (CO); 1H NMR (d
ppm), 8.02–6.90 (16H, m, 4 Ar), 4.68 (8H, s, 4CH2),
3.90 (12H, s, 4CH3).
1
3b
Empirical formula
Formula weight
Crystal system
C4H8I2N2O2Te
497.52
C18H18O2Te
393.92
Monoclinic
P2(1)/n
Monoclinic
P2(1)/n
Space group
Unit cell dimensions
˚
a (A)
7.3936(13)
16.073(3)
9.0676(16)
90
11.2075(13)
7.3963(8)
19.167(2)
90
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
91.430(3)
90
90.288(2)
90
3
˚
U (A )
1077.3(3)
103(2)
0.71073
4
1588.8(3)
103(2)
0.71073
4
Temperature (K)
Wavelength
Z
l(Mo Ka) (mmꢁ1
)
Reflections collected
Independent reflections
8.457
7067
2497 [Rint = 0.0642] 3798 [Rint = 0.0530]
1.874
11295
3.1.4. Reaction of Te with N-bromomethylphthalimide
N-Bromomethylphthalimide (1.0 g, 3.9 mmol) and
activated Te powder (0.25 g, 2.0 mmol) were heated
together at 150 ꢁC in absence of a solvent. Brownish
Final R indices [I>2r(I)] R1 = 0.0425,
wR2 = 0.1158
R1 = 0.0339,
wR2 = 0.0579
R1 = 0.0654,
wR2 = 0.0650
R indices (all data)
R1 = 0.0564,
wR2 = 0.1275

320
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 313–321
(e) E.E. Castellano, J. Zuckermann-Schpector, J.T. Ferreira, J.V.
Comasseto, Acta Cryst. C42 (1986) 44.
Fourier techniques (DIRDIF 94) [29]. Data reduction
and refinement were generally routine [30].
[8] B. Borecka, T.S. Cameron, M.A. Malik, B.C. Smith, Can. J.
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4. Supplementary material
[10] (a) A.K.S. Chauhan, A. Kumar, R.C. Srivastava, R.J. Butcher, J.
Organomet. Chem. 658 (2002) 169;
Crystallographic data for the structure analysis have
been deposited with the Cambridge Crystallographic
Data Center. CCDC numbers are 241611 for bis(acetam-
ido)tellurium diiodide 1 and 224723 for bis(4-methyl-
benzoylmethyl)telluride 3b. 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.
(b) A.K.S. Chauhan, A. Kumar, R.C. Srivastava, J. Beckmann,
A. Duthie, R.J. Butcher, J. Organomet. Chem. 689 (2004)
345.
[11] (a) P.C. Srivastava, A. Sinha, S. Bajpai, H.G. Schmidt, M.
Noltemeyer, J. Organomet. Chem. 575 (1999) 261;
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(c) L.Y.Y. Chan, F.W.B. Einstein, J. Chem. Soc., Dalton Trans.
(1972) 316.
[12] The average parameters concluded for the H2N–C(O) fragments
from 3160 observations in Cambridge Structural Database search
˚
˚
˚
are d(C–N) 1.327(25) A, d(C@O) 1.244(25) A, d(N–H) 0.906(1) A
and ÆH–N–H 119.2(1)ꢁ.
[13] C.B. Aakeroy, K.R. Seddon, Chem. Soc. Rev. (1993) 397.
[14] J.D. McCullough, Inorg. Chem. 14 (1975) 2639.
[15] (a) S. Kato, O. Niyomura, S. Nakaiida, Y. Kawahara, T. Kanda,
R. Yamada, S. Hori, Inorg. Chem. 38 (1999) 519;
(b) A.K. Singh, M. Kadarkaraiyasami, G.S. Murthy, J. Srinivas,
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Res. (S) (2001) 339;
Acknowledgement
The financial assistance by the Department of Science
and Technology, Government of India and University
Grants Commission, New Delhi is gratefully ack-
nowledged.
(d) A.K. Singh, J. Sooriyakumar, R.J. Butcher, Inorg. Chim.
Acta 312 (2001) 163.
[16] (a) V.I. Minkin, I.D. Sadekov, A.A. Maksimenko, O.E. Komp-
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(b) M.A.K. Ahmed, W.R. McWhinnie, T.A. Hamor, J. Organ-
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