Assembly of diverse structural types of organotellurium compounds in the reactions of (4-MeO-C6H4)2TeO with pyridine carboxylic acids

Article abstract of DOI:10.1016/j.jorganchem.2009.03.042

The reactions of Ar₂TeO (Ar = 4-MeO-C₆H₄) with 2-, 3- and 4-pyridine carboxylic acids (LH) afforded different organotelluroxane structural types depending on the stoichiometry of the reactants and the conditions of the rea

Full text of DOI:10.1016/j.jorganchem.2009.03.042

Journal of Organometallic Chemistry 694 (2009) 2628–2635
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Assembly of diverse structural types of organotellurium compounds in the reactions
of (4-MeO-C6H4)2TeO with pyridine carboxylic acids
*
Vadapalli Chandrasekhar , Arun Kumar
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur – 208 016, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of Ar2TeO (Ar = 4-MeO-C6H4) with 2-, 3- and 4-pyridine carboxylic acids (LH) afforded dif-
ferent organotelluroxane structural types depending on the stoichiometry of the reactants and the con-
ditions of the reaction. Ar2Te(L)OH (1a–1c) are formed in a 1:1 reaction of Ar2TeO with LH in the presence
of water. On the other hand a 1:2 reaction under anhydrous conditions leads to the formation of Ar2TeL2
(2a–2c). A 2:2 reaction under anhydrous conditions affords the ditelluroxanes Ar2Te(L)OTe(L)Ar2 (3a–3c)
while tritelluroxanes Ar2Te(L)OTeAr2OTe(L)Ar2 (4a–4c) are formed in 3:2 reactions. Interestingly, 3a–3c
are formed in the reaction of 2a–2c with Ar2TeO. The former can be hydrolyzed to 1a–1c while the latter
upon reaction with Ar2TeO lead to the formation of the tritelluroxanes 4a–4c. Attempts to metalate 2a
with PdCl2(MeCN)2 leads to a transfer of the carboxylate ligand to palladium affording Ar2TeCl2 and
PdL2. X-ray crystal structures of representative examples of the family of 1, 2 and 3 reveal interesting
supramolecular structures and the formation of a novel [TeO]2 structural unit. The latter results from
intermolecular secondary Teꢀ ꢀ ꢀO interactions.
Received 9 February 2009
Received in revised form 24 March 2009
Accepted 29 March 2009
Available online 5 April 2009
Keywords:
Telluroxanes
Pyridine carboxylic acid
[TeO]2 structural unit
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
tigations, Beckmann and coworkers have also reported formation
of similar structural types in the reactions of R2TeO (R = Ph, 4-
Organotelluroxanes, in general, and organotellurium oxides, in
particular, although known for a long time, are only recently being
investigated in a systematic manner [1–32]. We have been inter-
ested in organostannoxanes for some time now and have been able
to discover synthetic routes for a large variety of organostannox-
ane structural types [33–41]. Most of these are assembled by the
reactions of organotin oxides, -hydroxides or -oxide-hydroxides
with a variety of protic acids such as carboxylic, phosphinic, phos-
phoric or sulfonic acids [33–41]. We were interested in investigat-
ing the corresponding reactions with organotellurium oxides to
find out if divergent structural types can be formed by modulating
the nature of protic acid. As part of this research activity we have
recently reported the reactions of Ar2TeCl2 (Ar = 4-MeO-C6H4) with
1,10-ferrocenedicarboxylic acid (L0H2) which afforded the hetero-
metallic macrocycle [Ar2TeL0]2. [42]. Similar macrocycles [R2SnL0]2
(R = nBu, Bn) were also isolated in the reactions of R2SnCl2 with
L0H2 [42]. Encouraged by these results we have investigated the
reactions of Ar2TeO with 2-, 3- and 4-pyridine carboxylic acids
(LH). We have been able to isolate Ar2Te(L)(OH) (1), Ar2Te(L)2 (2),
Ar2Te(L)OTe(L)Ar2 (3) and Ar2Te(L)OTe(Ar)2OTe(L)Ar2 (4). The syn-
thesis, reactivity and structural characterization of these divergent
product types is discussed herein. During the course of these inves-
MeO-C6H4, 4-Me2N-C6H4) with phenol and o-nitrophenol [29].
Such correspondence of products formed in the reactions with di-
verse reagents such as carboxylic acids and phenols is quite rare
among organotin compounds.
2. Results and discussion
All the three pyridine carboxylic acids (LH) (2-, 3- and 4-) react
with Ar2TeO giving the same product type (Scheme 1). The nature
of the product formed does not depend on which pyridine carbox-
ylic acid was used but on the stoichiometry of the reactants and
the reaction conditions.
A 1:1 reaction of Ar2TeO with LH in presence of a slight excess
of water affords the hydroxycarboxylates [Ar2Te(OH)L] (1a, 1b, 1c)
(Scheme 1). Infrared spectra of these compounds show peaks at
3424, 3431 and 3424 cmꢁ1, respectively, due to the OH stretching
frequency. 125Te NMR shows singlets at 977.1 (1b) and 976.8 (1c).
The ESI-MS spectrum of 1c shows a peak at 736.9 which corre-
sponds to [M+C6H6+CH3C6H5+2CH3CN+H]+. A 1:2 reaction of Ar2-
TeO and LH affords the dicarboxylates Ar2TeL2 (2a–2c) (Scheme
1). 125Te NMR of these compounds show the presence of singlets
which are slightly downfield shifted in comparison to compounds
belonging to the family 1: 1056.7 (2a), 1001.1 (2b) and 1046.4
(2c) ppm. A 2:2 reaction of Ar2TeO and LH under anhydrous condi-
tions afforded the condensed ditelluroxanes 3a–3c [125Te NMR of
* Corresponding author. Tel.: +91 512 259 7259; fax: +91 521 259 0007/7436.
E-mail address: vc@iitk.ac.in (V. Chandrasekhar).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.03.042

V. Chandrasekhar, A. Kumar / Journal of Organometallic Chemistry 694 (2009) 2628–2635
2629
Scheme 1.
3a: 1033.0 ppm]. Representative examples of the family of com-
pounds 1, 2 and 3 have been characterized by single crystal X-
ray methods (vide infra). Tritelluroxanes 4a–4c were isolated in a
3:2 reaction of Ar2TeO with LH. These could not be characterized
by single crystal X-ray diffraction methods. However, their 125Te
NMR shows the presence of two signals [cf. 125Te of 4a: 967.6
and 975.2 ppm] suggesting their formation. Also the tritellurox-
anes 4a–4c are formed in reaction of 1a–1c with Ar2TeO (Scheme
2). From the work of Kobayashi it is already known that Ar2TeO re-
acts with cationic ditelluroxanes to afford oligotelluroxanes
[20,22]. In this case Ar2TeO functions as a nucleophile facilitating
the formation of new Te–O–Te bonds. Such a mechanism also ap-
pears to be operating in the conversion of 2a–2c to 3a–3c upon
reaction with Ar2TeO (Scheme 2). Interestingly, compounds 3a-3c
upon reaction with water afford the hydroxycarboxylates 1a–1c
(Scheme 2).
atoms for coordination. However, the reaction of 2a with
PdCl2(MeCN)2 resulted in the complete transfer of the carboxylate
ligand from tellurium to palladium resulting in the formation of
PdL2 and Ar2TeCl2 (Scheme 3). Such a transfer of carboxylate ligand
from a main-group metal to a transition metal ion has been re-
ported by us earlier and involves organotinpyrazolyl carboxylates
[43].
2.1. X-ray crystal structures of 1a, 1c, 2a, 2b, 3b and 3c
Crystal and cell parameter data for 1a, 1c, 2a, 2b, 3b and 3c are
given in Table 1. In view of the similarity of structures within a gi-
ven family only representative structures are discussed herein. The
remaining information is summarized in Supplementary material.
The molecular structure of 1a is shown in Fig. 1. Two molecules
are present in the asymmetric unit of which only one is shown in
Fig. 1a. The tellurium atom is present in a see-saw arrangement be-
cause of the influence of a stereochemically active lone pair. The
two oxygen atoms are trans with respect to each other with a
O5–Te–O3 bond angle of 168.57(11)°. The Te–O distance involving
the Te–OH group is considerably shorter (Te1–O5, 1.998(3) Å) in
comparison to the one which involves the carboxylate oxygen
atom (Te1–O3, 2.401(3) Å). A similar situation has been found by
Beckmann and co-workers in (p-MeO-C6H4)2Te(OPh)OH where
the Te–OH distance was 1.980(4) Å [29]. A long Te–O contact
involving the carbonyl oxygen atom (Te1ꢀ ꢀ ꢀO4: 2.8728(40) Å) is
also found in the present instance. This distance is smaller than
the sum of van der Waals radii (3.60 Å) and greater than the sum
of covalent radii (2.03 Å) of tellurium and oxygen atoms [44].
It was of interest to check the metalation behavior of these
compounds in view of the fact that they contained pyridyl nitrogen
Scheme 2.
Scheme 3.

2630
V. Chandrasekhar, A. Kumar / Journal of Organometallic Chemistry 694 (2009) 2628–2635
Table 1
X-ray crystallographic data for compounds 1a, 1c, 2a, 2b, 3b and 3c.
1a
1c
2a
2b
3b
3c
Empirical
formula
C20H19NO5Te
C20H19NO5Te
C52H44N4O13 Te2
C26H22N2O6Te
C197.50H180N8O38Te8
C191H176N8O36Te8
Formula weight
Temperature
[K]
480.96
100(2)
480.96
100(2)
1188.11
273(2)
586.06
100(2)
4294.29
153(2)
4180.2
100(2)
Wavelength [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
0.71073
Triclinic
P1
0.71073
Triclinic
P1
0.71073
Monoclinic
P21/c
20.878(4)
15.079(3)
15.972(3)
90
91.518(3)
90
5026.7(15)
4, 1.570
1.229
0.71073
Monoclinic
C2/c
23.5218(17)
15.1997(17)
15.3941(13)
90
120.141(2)
90
4759.6(18)
8, 1.636
0.71073
Monoclinic
P21/n
15.2510(13)
23.540(2)
25.744(2)
90
101.988(2)
90
9040.5(14)
2, 1.578
1.351
0.71073
Monoclinic
P21/n
14.8863(13)
23.393(2)
26.083(2)
90
98.992(2)
90
8971.5(14)
2, 1.547
1.358
ꢀ
ꢀ
10.7129(12)
11.5508(13)
17.185(2)
92.308(2)
103.340(2)
112.953(2)
1885.1(4)
4, 1.695
9.9767(15)
13.604(2)
15.596(2)
102.016(3)
104.604(3)
107.970(3)
1852.0(5)
4, 1.725
a
[°]
b [°]
c
[°]
V [Å3]
Z, Dcalc. [g cmꢁ3
l
]
[mmꢁ1
]
1.609
1.638
1.295
F(0 0 0)
952
952
2368
2336
4282
4164
Crystal size
[mm]
0.1 ꢂ 0.08 ꢂ 0.04
0.07 ꢂ 0.03 ꢂ 0.02
0.08 ꢂ 0.05 ꢂ 0.04
0.11 ꢂ 0.08 ꢂ 0.06
0.08 ꢂ 0.06 ꢂ 0.03
0.1 ꢂ 0.07 ꢂ 0.04
h range [°]
Limiting indices
2.14–26.00
ꢁ13 6 h 6 12,
ꢁ14 6 k 6 13,
ꢁ16 6 l 6 21
10 480
2.25–27.00
ꢁ12 6 h 6 10,
ꢁ17 6 k 6 16,
ꢁ18 6 l 6 19
11 234
2.08–28.35
ꢁ27 6 h 6 18,
ꢁ19 6 k 6 18,
ꢁ21 6 l 6 21
32 376
2.58–25.00
ꢁ27 6 h 6 27,
ꢁ18 6 k 6 11,
ꢁ17 6 l 6 18
12 118
2.08–26.50
ꢁ18 6 h 6 19,
ꢁ29 6 k 6 29,
ꢁ20 6 l 6 32
51 975
2.12–26.50
ꢁ18 6 h 6 15,
ꢁ17 6 k 6 29,
ꢁ30 6 l 6 32
51 760
Reflections
collected
Independent
reflections
7216 (0.0152)
7838 (0.0399)
12 307 (0.0904)
4200 (0.0415
18 675 (0.0747)
18 580 (0.0737)
(Rint
)
Data/restraints/
parameters
Goodness-of-fit
on F2
7216/0/493
1.095
7838/4/466
1.050
12 307/38/662
0.926
4200/12/318
1.054
18 675/23/1156
0.993
18 580/0/1103
1.018
Final R indices
[I > 2r(I)]
R indices (all
data)
R1 = 0.0354,
wR2 = 0.0960
R1 = 0.0390,
wR2 = 0.1085
R1 = 0.0873,
wR2 = 0.2149
R1 = 0.1477,
wR2 = 0.2735
R1 = 0.0758,
wR2 = 0.1677
R1 = 0.1864,
wR2 = 0.2231
R1 = 0.0380,
wR2 = 0.0883
R1 = 0.0470,
wR2 = 0.0949
R1 = 0.0495,
wR2 = 0.1062
R1 = 0.0826,
wR2 = 0.1274
R1 = 0.0559,
wR2 = 0.1336
R1 = 0.0911,
wR2 = 0.1662
The molecular structure of 2b is shown in Fig. 2a. The two car-
boxylate ligands bind to the central tellurium atom in a chelating
anisobidentate manner (cf. Te–O5, 2.136(3); Te–O6, 2.9524(26)
Å), resulting in an overall skewed-trapezoidal geometry. In spite of
the chelating coordination of the carboxylate ligands the O5–Te–
O3 bond angle (165.19(10)°) is not distorted appreciably and is
in fact comparable to that found in Ph2Te(OPh)2 (166.0(2)°) [29].
The molecular structure of 3c is shown in Fig. 3a. Although two
molecules are present in its asymmetric unit, only one of them is
shown. The ditelluroxane is characterized by an acute Te1–O7–
Te2 angle of 116.3(2)° which is comparable to that found in
(R’O)R2TeOTeR2(OR0) (R = p-MeOC6H4; R0 = o-O2NC6H4) [29]. The
Te–O bond distances involving the central oxygen atom (av.
2.008(4) Å) are shorter than the Te–O bond distances involving
the carboxyl oxygen atom (av. 2.291(4) Å). As in the case of the
other family of compounds discussed already 3c is also character-
ized by the presence of long Teꢀ ꢀ ꢀO contacts (av. 3.063(5) Å).
tion of a one-dimensional chain (Supplementary material). Although
1c also forms a hydrogen-bonded dimer similar to that of 1b, further
supramolecular interactions are different due to the involvement of
the p-OMe group (Supplementary material). In contrast to the situa-
tion found here, (p-MeO-C6H4)2Te(OPh)OH does not appear to gen-
erate intermolecular secondary Teꢀ ꢀ ꢀO interactions [29].
The crystal structures of 2a and 2b show the formation of a cen-
trosymmetric dimeric unit which occurs as a result of reciprocato-
ry intermolecular Teꢀ ꢀ ꢀO interactions (cf. in 2b: Teꢀ ꢀ ꢀO4,
3.4194(40) Å). Further supramolecular interactions (C–Hꢀ ꢀ ꢀN and
C–Hꢀ ꢀ ꢀO) generate a 3D-supramolecular structure in 2b (Support-
ing Information). In 2a the two independent molecules present in
the asymmetric unit interact with only molecules of their type
leading to chain-structures (Supplementary material). This is facil-
itated by intermolecular C–Hꢀ ꢀ ꢀN interactions. Again, the corre-
sponding (p-Me2N-C6H4)2Te(OPh)2 and Ph2Te(OPh)2 do not
exhibit secondary Teꢀ ꢀ ꢀO interactions [29].
The supramolecular structures of 3b and 3c are similar and in-
volve two orthogonal O@C–O–Te–O–Te–O–C@O motifs which
interact with each other through secondary Teꢀ ꢀ ꢀO interactions
affording cyclic structures. Such supramolecular ring formation ap-
pears to be quite unique among organotelluroxanes (Fig. 3b and 4).
2.2. Supramolecular structures
The Te–OH units present in 1a do not interact with each other.
Two different molecules present in different asymmetric units
interact with each other to afford a dimeric structure. In this inter-
action the OH group (H5BO) participates in a bifurcated hydrogen
bonding with a pyridyl nitrogen atom (N1A) and a carboxylate oxy-
gen (O4A). This leads to the formation of an interesting
2.3. Conclusions
In conclusion, we report the formation of four different struc-
tural types in the reactions of Ar2TeO with pyridine carboxylic
acids. The nature of the carboxylic acid (2-, 3- or -4) does not affect
the course of reaction. On the other hand, the product formed de-
pends on the stoichiometry of the reactants. Among the four prod-
structural motif (Te1Aꢀ ꢀ ꢀO4B,
Te2O2 [Te1A-O4B-Te1B-O4A]
2.8059(36); Te1Aꢀ ꢀ ꢀO4A, 2.8728 (40); Te1Bꢀ ꢀ ꢀO4B, 3.0522(38);
Te1Bꢀ ꢀ ꢀO4A, 2.7282(33) Å). Further C–Hꢀ ꢀ ꢀO interactions (between
O5B and a pyridyl C–H(H20B); O5A and H20A) leads to the forma-

V. Chandrasekhar, A. Kumar / Journal of Organometallic Chemistry 694 (2009) 2628–2635
2631
Fig. 1. (a) ORTEP drawing of 1a with 50% probability thermal ellipsoids (only one molecule (molecule ‘a’) present in the asymmetric unit is shown). Hydrogen atoms,
molecule ‘b’ and solvent molecules have been omitted for clarity. Selected bond distances (Å) and angles (°) are as follows: Te1–C1, 2.113(4); Te1–C8, 2.112(4); Te1–O3,
2.401(3); Te1–O5, 1.998(3); Te1ꢀ ꢀ ꢀO4, 2.8728(40); O5–Te1–C8, 92.17(15); O5–Te1–C1, 85.81(14); C8–Te1–C1, 94.13(16); O5–Te1–O3, 168.57(11); C8–Te1–O3, 86.83(14);
C1–Te1–O3, 82.90(13). See Figure S2 in the Supporting information for a complete asymmetric unit. (b) A [TeO]2 dimeric unit is formed through intermolecular Teꢀ ꢀ ꢀO, O–
Hꢀ ꢀ ꢀO and O–Hꢀ ꢀ ꢀN interactions between the two molecules present in the asymmetric unit. Atoms involved in interactions are lying in a plane. Anisyl groups have been
omitted for clarity. The bond distances (Å) and angles (°) involved are: Te1Aꢀ ꢀ ꢀO4A, 2.8728(40); Te1Aꢀ ꢀ ꢀO4B, 2.8059(36); Te1Bꢀ ꢀ ꢀO4B, 3.0522(38); Te1Bꢀ ꢀ ꢀO4A, 2.7282(33);
H5AOꢀ ꢀ ꢀN1B, 2.1276(35); H5AOꢀ ꢀ ꢀO4B, 2.4005(42); H5BOꢀ ꢀ ꢀN1A, 1.9548(35); H5BOꢀ ꢀ ꢀO4A, 2.4750(39); O5A–H5AOꢀ ꢀ ꢀN1B, 162.764(239); O5A–H5AOꢀ ꢀ ꢀO4B,123.245(243);
O5B–H5BOꢀ ꢀ ꢀN1A, 165.577(241); O5B–H5BOꢀ ꢀ ꢀO4A, 119.755(237).
Fig. 2. (a) ORTEP drawing of 2b with 50% probability thermal ellipsoids. Hydrogen atoms have been omitted for clarity. Selected bond distances (Å) and angles (°) are as
follows: Te–C1, 2.102(4); Te–C8, 2.095(4); Te–O3, 2.164(3); Te–O5, 2.136(3); Teꢀ ꢀ ꢀO4, 3.0280(26); Teꢀ ꢀ ꢀO6, 2.9524(26); C8–Te–C1, 98.17(15); C8–Te–O5, 86.26(13); C1–Te–
O5, 83.12(13); C1–Te–O3, 83.79(13); C8–Te–O3, 88.77(13); O5–Te–O3, 165.19(10). (b) A centrosymmetric [TeO]2 dimeric unit formed through reciprocatory intermolecular
Teꢀ ꢀ ꢀO interactions. Anisyl groups have been omitted for clarity. Bond distance (Å): Teꢀ ꢀ ꢀO4h, 3.4196(40) Å.
uct types isolated in the present instance, two are monotellurium
derivatives, while the others are a ditelluroxane and tritelluroxane.
The structures of these products are similar to those isolated from
the reaction of diorganotellurium oxides with phenols. However, in
the present instance we have been able to observe interesting
supramolecular structures involving a novel [TeO]2 dimeric struc-

2632
V. Chandrasekhar, A. Kumar / Journal of Organometallic Chemistry 694 (2009) 2628–2635
Fig. 3. (a) ORTEP drawing of 3c with 50% probability thermal ellipsoids (only molecule ‘a’ is shown). Hydrogen atoms, molecule ‘b’ and solvent molecules have been omitted for
clarity. Selected bond distances (Å) and angles (°) are as follows: Te1–C1, 2.105(6); Te1–C8, 2.102(6); Te2–C15, 2.111(6); Te2–C22, 2.103(6); Te1–O5, 2.308(4); Te1–O7,
2.001(4); Te2–O7, 2.015(4); Te2–O8, 2.273(4); Te1ꢀ ꢀ ꢀO6, 3.0044(52); Te2ꢀ ꢀ ꢀO9, 3.1218(49); Te1–O7–Te2, 116.3(2); O7–Te1–C8, 87.8(2); O7–Te1–C1, 91.8(2); C8–Te1–C1,
95.8(2); O7–Te1–O5, 170.64(17); C8–Te1–O5, 84.1(2); C1–Te1–O5, 84.4(2); O7–Te2–C22, 90.7(2); O7–Te2–C15, 88.9(2); C22–Te2–C15, 95.2(2); O7–Te2–O8, 169.11(17);
C22–Te2–O8, 85.6(2); C15–Te2–O8, 81.3(2). See Fig. S17 in the Supporting information for a complete asymmetric unit. (b) A dimeric unit formed as a result of interactions
between molecule ‘a’ and molecule ‘b’ through intermolecular Teꢀ ꢀ ꢀO interactions. Bond distances (Å) and angles (°) involved are: Te1Aꢀ ꢀ ꢀO6A, 3.0044(52); Te2Aꢀ ꢀ ꢀO9A,
3.1218(49); Te1Bꢀ ꢀ ꢀO6B, 3.0461(49); Te2Bꢀ ꢀ ꢀO9B, 3.0657(62); Te1Aꢀ ꢀ ꢀO6B, 3.4567(61); Te2Aꢀ ꢀ ꢀO9B, 3.0182(74); Te2Bꢀ ꢀ ꢀO6A, 3.1232(50); Te1Bꢀ ꢀ ꢀO9A, 3.0426(50).
dures and stored under nitogen atmosphere and over activated
molecular sieves [45]. Tellurium tetrachloride, ortho-, meta- and
para-pyridinecarboxylic acids and palladium(II) chloride were pur-
chased from Aldrich Chemical Co. (USA) and were used as received.
Bis(p-methoxyphenyl)telluroxide was prepared from the reaction
of anisole with tellurium tetrachloride followed by its oxidation
with NaOH as reported in the literature [46]. Sodium hydroxide
(RANKEM) was purchased from RFCL Limited, New Delhi, India
and was used as such. Anisole was purchased from s.d. Fine. Chem.
Ltd., Mumbai, India and distilled under N2 atmosphere before use.
Melting points were measured by using a JSGW melting point
apparatus and are uncorrected. Elemental Analyses of the com-
pounds were obtained using a EAI elemental analyzer CE-440 mod-
el. The analyses of compounds were carried out on fully dried
samples. IR spectra were recorded as KBr pellets with a Bruker Vec-
tor 22 FTIR spectrophotometer operating from 4000 to 400 cmꢁ1
Electrospray ionization mass spectra were recorded with
.
a
WATERS–HAB213 spectrometer by using capillary 2.7 kV. NMR
(1H, 13C and 125Te NMR) spectra were recorded with a JEOL JNM
LAMBDA 400 model spectrometer or a JEOL JNM DELTA 500 model
spectrometer.
3.2. Syntheses
3.2.1. Synthesis of di-p-anisyltellurium hydroxy pyridylcarboxylates,
(4-MeO-C6H4)2Te(O2CC5H4N)(OH) (1a–1c)
Fig. 4. Mutually orthogonal orientation of the two O–Te–O–Te–O fragments in 3c.
Pyridinecarboxylic acid (0.25 g, 2.0 mmol) and bis(p-anisyl)tel-
luroxide (0.71 g, 2.0 mmol) were dissolved in toluene-methanol
(15 mL each) containing ꢃ1 mL of water. Prolonged (ꢃ24 h) heat-
ing at reflux under constant stirring gave a clear solution. The reac-
tion mixture was allowed to cool to room temperature and the
volatiles were removed completely under vacuum. The resulting
solid was recrystallized from its water–methanol (1:10 mL)
solution.
tural motif which is formed as a result of intermolecular secondary
Teꢀ ꢀ ꢀO interactions.
3. Experimental
3.1. Reagents and general procedures
1a: Yield: 0.80 g (83%). m.p. 142–143 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1603.24, masym (OH), 3423.95. 1H NMR (400 MHz, CDCl3):
d 3.75 (s, 6H, OMe), 6.84–7.76 (m, 12H, arom) ppm. 13C NMR
All reactions were carried out using anhydrous solvents unless
otherwise stated. The solvents were purified by standard proce-

V. Chandrasekhar, A. Kumar / Journal of Organometallic Chemistry 694 (2009) 2628–2635
2633
(500 MHz, CDCl3): d 170.72 (OCO), 161.64 (p-anisyl), 151.89 (2-
pyridyl), 149.24 (6-pyridyl), 136.71 (o-anisyl), 134.34 (3 and 5-pyr-
idyl), 125.42 (4-pyridyl), 124.73 (i-anisyl), 115.11 (m-anisyl), 55.46
(OMe) ppm. Anal. Calc. for C20H19NO5Te (480.97): C, 49.94; H, 3.98;
N, 2.91. Found: C, 49.81; H, 3.83; N, 2.83%. ESI-MS: m/z
(%) = 361.0052 (100) [(4-OMe-Ph)2Te(OH)]+, 78.9738 (16) [(4-
OMe-Ph)2TeO + H2O + H)]+, 717.0108 (4) [2(4-OMe-Ph)2TeO+H)]+,
736.9713 (28) [M+C6H6+CH3C6H5+2CH3CN+H]+.
ppm. Anal. Calc. for C26H22N2O6Te (586.06): C, 53.28; H, 3.78; N,
4.78. Found: C, 53.35; H, 3.69; N, 4.82%. ESI-MS: m/z
(%) = 124.0334 (93) [C5H4NCOOH+H]+, 360.9918 (100) [(4-OMe-
Ph)2Te(OH)]+, 528.9966 (4) [(4-OMe-Ph)2TeO+C5H4NCOOH+H-
COOH], 717.0073 (18) [2(4-OMe-Ph)2TeO+H)]+, 744.9816 (39)
[M+CH3C6H5+CH3OH + H]+, 822.0072 (36) [M + C5H4NCOOH +
HCOOH + 2CH3OH + H]+.
2c: Yield: 0.46 g (78%). m.p. 155–157 °C. IR (KBr)/cmꢁ1
: masym
1b: Yield: 0.75 g (78%). m.p. 161–166 °C. IR (KBr)/cmꢁ1
:
masym
(COO), 1641.46. 1H NMR (400 MHz, CDCl3): d 3.89 (s, 6H, OMe),
7.04–8.28 (m, 16H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
173.75 (OCO), 161.86 (p-anisyl), 150.45 (2- and 6-pyridyl),
134.98 (4-pyridyl), 133.66 (3- and 5-pyridyl), 132.66 (o-anisyl),
126.21 (i-anisyl), 116.58 (m-anisyl), 55.49 (OMe) ppm. 125Te
NMR (157.8 MHz, DCM+CDCl3): d = 1046.4 (s) ppm. Anal. Calc. for
C26H22N2O6Te (586.06): C, 53.28; H, 3.78; N, 4.78. Found: C,
53.21; H, 3.84; N, 4.69%. ESI-MS: m/z (%) = 124.0360 (53) [C5H4
NCOOH+H]+, 360.9973 (100) [(4-OMe-Ph)2Te(OH)]+, 528.9946 (3)
[(4-OMe-Ph)2TeO+C5H4NCOOH+HCOOH], 717.0005 (6) [2(4-OMe-
Ph)2TeO+H)]+, 744.9876 (33) [M+CH3C6H5+CH3OH+H]+, 822.0219
(5) [M+C5H4NCOOH+HCOOH+2CH3OH+H]+.
(COO), 1602.13, masym (OH), 3431.17. 1H NMR (400 MHz, CDCl3): d
3.73 (s, 6H, OMe), 6.94–8.54 (m, 12H, arom) ppm. 13C NMR
(500 MHz, CDCl3): d 165.96 (OCO), 156.31 (p-anisyl), 142.47 (2-
pyridyl), 141.69 (6-pyridyl), 139.13 (3-pyridyl), 134.03 (4-pyridyl),
133.33 (o-anisyl), 130.44 (5-pyridyl), 128.24 (i-anisyl), 119.35 (m-
anisyl), 60.40 (OMe) ppm. 125Te NMR (157.8 MHz, DCM + CDCl3): d
= 977.1 (s) ppm. Anal. Calc. for C20H19NO5Te (480.97): C, 49.94; H,
3.98; N, 2.91. Found: C, 50.21; H, 3.75; N, 2.96%.
1c: Yield: 0.79 g (81%). m.p. 175–182 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1625.42, masym (OH), 3423.74. 13C NMR (500 MHz, CDCl3):
d 170.21 (OCO), 161.22 (p-anisyl), 153.27 (2- and 6-pyridyl),
149.44 (4-pyridyl), 137.23 (3- and 5-pyridyl), 134.60 (o-anisyl),
124.52 (i-anisyl), 115.08 (m-anisyl), 55.79 (OMe) ppm. 125Te
NMR (157.8 MHz, DCM + CDCl3): d = 976.8 (s) ppm. Anal. Calc. for
C20H19NO5Te (480.97): C, 49.94; H, 3.98; N, 2.91. Found: C,
49.78; H, 3.78; N, 2.87%.
3.2.3. Synthesis of tetra-p-anisylditelluroxane bis(pyridyl-
carboxylates), (4-MeO-C6H4)2Te(O2CC5H4N)OTe(O2CC5H4N)(4-MeO-
C6H4)2 (3a–3c)
Pyridinecarboxylic acid (0.25 g, 2.0 mmol) and bis(p-anisyl)tel-
luroxide (0.71 g, 2.0 mmol) were dissolved in toluene-methanol
(20 mL each). The reaction mixture was heated at reflux under stir-
ring for ꢃ16 h. After allowing the reaction mixture to come to
room temperature volatiles were removed completely under vac-
uum. The solid, thus obtained was dissolved in a mixture of chlo-
roform-methanol (10 mL) which on slow evaporation gave
colorless crystals.
Alternatively, compounds 1a–1c have been prepared by the
hydrolysis of 3a–3c, respectively. In a general procedure, product
type 3 (0.095 g, 0.1 mmol) was heated at reflux in 10 mL aque-
ous-methanol (ꢃ50%) for about 24 h. The solution was cooled to
room temperature and concentrated up to 1–2 mL under vacuum
and ꢃ15 mL methanol was added. Again it was reduced to about
5 mL. Slow evaporation of solution afforded colorless crystals of
respective product type 1 in 45–59% yields.
3a: Yield: 0.72 g (76%). m.p. 131–132 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1603.48. 1H NMR (400 MHz, CDCl3): d 3.74 (s, 12H, OMe),
6.92–8.93 (m, 24H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
170.68 (OCO), 161.91 (p-anisyl), 150.12 (2-pyridyl), 141.59 (6-pyr-
idyl), 134.19 (o-anisyl), 129.12 (3-pyridyl), 128.32 (5-pyridyl),
125.38 (4-pyridyl), 123.34 (i-anisyl), 115.32 (m-anisyl), 55.53
(OMe) ppm. 125Te NMR (157.8 MHz, DCM+CDCl3): d = 1033.0 (s)
ppm. Anal. Calc. for C40H36N2O9Te2 (943.92): C, 50.90; H, 3.84; N,
2.97. Found: C, 51.17; H, 3.60; N, 2.93%.
3.2.2. Synthesis of di-p-anisyltellurium bis(pyridylcarboxylates),
(4-MeO-C6H4)2Te(O2CC5H4N)2 (2a–2c)
A mixture of pyridinecarboxylic acid (0.25 g, 2.0 mmol) and
bis(p-anisyl)telluroxide (0.36 g, 1.0 mmol) were taken together in
dry toluene (ꢃ50 mL) and stirred under heating at reflux with
the use of a Dean–Stark apparatus for 8 h. The reaction mixture
was allowed to come to room temperature and the volume re-
duced to about 10 mL and about 2 mL of dry methanol was added.
Slow evaporation of the solution afforded colorless crystals which
were collected by decantation and washed with cold diethyl ether.
3b: Yield: 0.63 g (65%). m.p. 132–136 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1602.68. 1H NMR (400 MHz, CDCl3): d 3.89 (s, 12H, OMe),
6.90–8.64 (m, 24H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
170.69 (OCO), 161.66 (p-anisyl), 151.86 (2-pyridyl), 149.22 (6-pyr-
idyl), 136.75 (3-pyridyl), 135.32 (4-pyridyl), 134.34 (o-anisyl),
125.46 (5-pyridyl), 124.74 (i-anisyl), 115.12 (m-anisyl), 55.46
(OMe) ppm. Anal. Calc. for C40H36N2O9Te2 (943.92): C, 50.90; H,
3.84; N, 2.97. Found: C, 50.93; H, 3.77; N, 3.16%.
2a: Yield: 0.48 g (82%). m.p. 168–171 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1659.16. 1H NMR (400 MHz, CDCl3): d 3.75 (s, 6H, OMe),
6.88–8.73 (m, 16H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
169.69 (OCO), 161.78 (p-anisyl), 149.50 (2-pyridyl), 149.27 (6-pyr-
idyl), 136.96 (o-anisyl), 135.05 (3-pyridyl), 127.77 (5-pyridyl),
126.26 (4-pyridyl), 125.26 (i-anisyl), 115.33 (m-anisyl), 55.37
(OMe) ppm. 125Te NMR (157.8 MHz, DCM + CDCl3): d = 1056.7 (s)
ppm. Anal. Calc. for C26H22N2O6Te (586.06): C, 53.28; H, 3.78; N,
4.78. Found: C, 53.02; H, 3.68; N, 4.89%. ESI-MS: m/z
(%) = 124.0388 (26) [C5H4NCOOH+H]+, 360.9916 (100) [(4-OMe-
Ph)2Te(OH)]+, 528.9963 (6) [(4-OMe-Ph)2TeO+C5H4NCOOH+H-
COOH], 717.0009 (15) [2(4-OMe-Ph)2TeO+H)]+, 744.9789 (41)
[M+CH3C6H5+CH3OH + H]+, 822.0154 (18) [M + C5H4NCOOH +
HCOOH + 2CH3OH + H]+.
3c: Yield: 0.68 g (72%). m.p. 160 °C. IR (KBr)/cmꢁ1
: masym (COO),
1603.99. 1H NMR (400 MHz, CDCl3): d 3.84 (s, 12H, OMe), 6.94–
8.69 (m, 24H, arom) ppm. 13C NMR (500 MHz, CDCl3): d 170.31
(OCO), 160.46 (p-anisyl), 149.37 (2- and 6-pyridyl), 137.52 (4-pyr-
idyl), 135.42 (3- and 5-pyridyl), 134.37 (o-anisyl), 124.59 (i-anisyl),
115.15 (m-anisyl), 55.79 (OMe) ppm. Anal. Calc. for C40H36N2O9Te2
(943.92): C, 50.90; H, 3.84; N, 2.97. Found: C, 51.09; H, 3.96; N,
2.79%.
In an alternate procedure, product type 2 (0.06 g, 0.1 mmol) and
bis(p-anisyl)telluroxide (0.036 g, 0.1 mmol) were heated at reflux
together in ꢃ10 mL toluene-methanol containing small amount
of water aqueous-methanol for 6 h under stirring condition. The
resulting solution was cooled to room temperature and concen-
trated to dryness. Recrystallization from chloroform–methanol
solution afforded colorless crystals product type 3 in 41–56%
yields.
2b: Yield: 0.43 g (73%). m.p. 182–183 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1642.74. 1H NMR (400 MHz, CDCl3): d 3.78 (s, 6H, OMe),
6.96–9.07 (m, 16H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
170.22 (OCO), 162.05 (p-anisyl), 152.71 (2-pyridyl), 151.23 (6-pyr-
idyl), 137.39 (3-pyridyl), 134.34 (4-pyridyl), 127.59 (o-anisyl),
125.30 (5-pyridyl), 123.15 (i-anisyl), 115.54 (m-anisyl), 55.42
(OMe) ppm. 125Te NMR (157.8 MHz, DCM+CDCl3): d = 1001.1 (s)

2634
V. Chandrasekhar, A. Kumar / Journal of Organometallic Chemistry 694 (2009) 2628–2635
3.2.4. Synthesis of hexa-p-anisyltritelluroxanes
Acknowledgments
bis(pyridylcarboxylate), (4-MeO-C6H4)2Te(O2CC5H4N)OTe(4-MeO-
C6H4)2OTe(O2CC5H4N)(4-MeO-C6H4)2 (4a–4c)
V.C. is a Lalit Kapoor Chair Professor of Chemistry. V.C. is thank-
ful to the Department of Science and Technology for a J.C. Bose fel-
lowship. A.K. thanks the Department of Science and Technology for
Fast Track Young Scientist Fellowship.
A 2:3 mixture of pyridinecarboxylic acid (0.123 g, 1.0 mmol)
and bis(p-anisyl)telluroxide (0.54 g, 1.5 mmol) were taken in tolu-
ene–methanol (15 mL each) and stirred under heating at reflux
conditions for ꢃ12 h. After cooling to room temperature the reac-
tion mixture was concentrated to ꢃ5 mL and 10 mL of toluene
added. Slow evaporation of this mixture gave colorless crystals.
Appendix A. Supplementary material
4a: Yield: 0.48 g (74%). m.p. 180–188 °C. IR (KBr)/cmꢁ1
: masym
CCDC 718395, 718396, 718397, 718398, 718399 and 718400
contain the supplementary crystallographic data for 1a, 1c, 2a, 2b,
3b and 3c. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via http://www.ccdc.cam.a-
c.uk/data_request/cif. Supplementary material (Tables of selected
bond length and angles for compound 1a, 2a, 2b, 3b, 1c and 3c,
and additional figures) associated with this article can be found,
in the online version, at doi:10.1016/j.jorganchem.2009.03.042.
(COO), 1595.70. 1H NMR (400 MHz, CDCl3): d 3.75 (18H, OMe),
6.89–7.78 (m, 32H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
170.21 (OCO), 161.43 (p-anisyl), 152.56 (2-pyridyl), 149.25 (6-pyr-
idyl), 137.25 (o-anisyl), 134.44 (3- and 5-pyridyl), 125.69 (4-pyri-
dyl), 124.45 (i-anisyl), 115.01 (m-anisyl), 55.82 (OMe) ppm. 125Te
NMR (157.8 MHz, DCM+CDCl3): d = 967.6 and 975.2 (s) ppm in
2:1 ratio for terminal and inner tellurium atoms respectively. Anal.
Calc. for C54H50N2O12Te3 (1301.78): C, 49.82; H, 3.87; N, 2.15.
Found: C, 50.0; H, 3.79; N, 2.31%.
References
4b: Yield: 0.37 g (57%). m.p. 151–152 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1604.36. 1H NMR (400 MHz, CDCl3): d 3.79 (18H, OMe),
6.88–9.06 (m, 32H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
170.95 (OCO), 161.67 (p-anisyl), 151.54 (2-pyridyl), 151.22 (6-pyr-
idyl), 137.10 (3-pyridyl), 133.97 (4-pyridyl), 128.61 (o-anisyl),
128.32 (5-pyridyl), 122.96 (i-anisyl), 115.06 (m-anisyl), 55.49
(OMe) ppm. Anal. Calc. for C54H50N2O12Te3 (1301.78): C, 49.82;
H, 3.87; N, 2.15. Found: C, 49.59; H, 4.01; N, 2.09%.
[1] M.M. Campos, E.L. Suranyi, H. de Andrade, N. Petragnani Jr., Tetrahedron 20
(1964) 2797–2801.
[2] J.I. Musher, Angew. Chem. 81 (1969) 68–82.
[3] J.I. Musher, Angew. Chem., Int. Ed. Engl. 8 (1969) 54–68.
[4] B.C. Pant, Tetrahedron Lett. (1972) 4779–4780.
[5] B.C. Pant, W.R. McWhinnie, N.S. Dance, J. Organomet. Chem. 63 (1973) 305–
310.
[6] B.C. Pant, J. Organomet. Chem. 65 (1974) 51–56.
[7] K.J. Irgolic, The Organic Chemistry of Tellurium, Gordon and Breach, New York,
1974.
[8] C.S. Mancinelli, D.D. Titus, R.F. Ziolo, J. Organomet. Chem. 140 (1977) 113–
125.
[9] K.J. Irgolic, J. Organomet. Chem. 158 (1978) 267–323.
[10] N.W. Alcock, R.M. Countryman, J. Chem. Soc., Dalton Trans. (1979) 851–853.
[11] N.W. Alcock, W.D. Harrison, J. Chem. Soc., Dalton Trans. (1982) 709–712.
[12] N.W. Alcock, W.D. Harrison, J. Chem. Soc., Dalton Trans. (1982) 1421–1428.
[13] N.W. Alcock, W.D. Harrison, C.J. Howes, J. Chem. Soc., Dalton Trans. (1984)
1709–1716.
[14] N.W. Alcock, M. Roe, J. Chem. Soc., Dalton Trans. (1989) 1589–1598.
[15] J. Bergman, L. Engman, J. Sidén, in: S. Patai, Z. Rappoport (Eds.), The Chemistry
of Organic Selenium and Tellurium Compounds, vol. 1, Wiley, Chichester,
1986, pp. 517–558.
4c: Yield: 0.41 g (62%). m.p. 192–195 °C. IR (KBr)/cmꢁ1
: masym
(COO), 1595.67. 1H NMR (400 MHz, CDCl3): d 3.73 (18H, OMe,),
6.98–8.54 (m, 32H, arom) ppm. 13C NMR (500 MHz, CDCl3): d
174.97 (OCO), 166.36 (p-anisyl), 158.04 (2- and 6-pyridyl),
141.97 (4-pyridyl), 139.64 (3- and 5-pyridyl), 130.34 (o-anisyl),
128.78 (i-anisyl), 119.53 (m-anisyl), 60.57 (OMe) ppm. Anal. Calc.
for C54H50N2O12Te3 (1301.78): C, 49.82; H, 3.87; N, 2.15. Found:
C, 49.63; H, 3.97; N, 2.23%.
In an alternate procedure, product type 1 (0.096 g, 0.2 mmol)
and bis(p-anisyl)telluroxide (0.036 g, 0.1 mmol) were heated at re-
flux together in dry toluene using Dean–Stark apparatus for 10 h.
The reaction mixture was allowed to come at room temperature
and concentrated to 5 mL. Slow evaporation of the solution affor-
ded colorless crystals of product type 4 in 37–45% yields.
[16] A.E. Reed, P. Von, R.J. Schleyer, Am. Chem. Soc. 112 (1990) 1434–1445.
[17] P. Magnus, M.B. Roe, V. Lynch, C. Hulme, J. Chem. Soc., Chem. Commun. (1995)
1609–1610. and references therein.
[18] K.-y. Akiba, Chemistry of Hypervalent Compounds, Wiley-VCH, New York,
1998.
[19] K. Kobayashi, N. Deguchi, E. Horn, N. Furukawa, Angew. Chem., Int. Ed. Engl. 37
(1998) 984–986.
[20] K. Kobayashi, N. Deguchi, O. Takahashi, K. Tanaka, E. Horn, O. Kikuchi, N.
Furukawa, Angew. Chem., Int. Ed. Engl. 38 (1999) 1638–1640.
[21] K. Kobayashi, H. Izawa, K. Yamaguchi, E. Horn, N. Furukawa, Chem. Commun.
(2001) 1428–1429.
[22] K. Kobayashi, K. Tanaka, H. Izawa, Y. Arai, N. Furukawa, Chem. Eur. J. 7 (2001)
4272–4279.
[23] K.K. Verma, D. Soni, S. Verma, Phosphorus Sulfur Silicon Relat Elements 166
(2000) 231–241.
[24] H. Citeau, K. Kirschbaum, O. Conrad, D.M. Giolando, Chem. Commun. (2001)
2006–2007.
[25] T.M. Klapötke, B. Krumm, P. Mayer, H. Piotrowski, O. Ruscitti, Z. Naturforsch.
57b (2002) 145–150.
[26] J. Beckmann, D. Dakternieks, A. Duthie, F. Ribot, M. Schürmann, N.A. Lewcenko,
Organometallics 22 (2003) 3257–3261.
[27] J. Beckmann, D. Dakternieks, A. Duthie, N.A. Lewcenko, C. Mitchell, M.
Schurmann, Z. Anorg. Allg. Chem. 631 (2005) 1856–1862.
[28] J. Beckmann, J. Bolsinger, J. Spandl, J. Organomet. Chem. 693 (2008) 957–
964.
[29] J. Beckmann, J. Bolsinger, A. Duthie, Aust. J. Chem. 61 (2008) 172–182.
[30] H.W. Roesky, R.J. Butcher, S. Bajpai, P.C. Srivastava, Phosphorus Sulfur Silicon
Relat. Elements 161 (2000) 135–141.
3.3. X-ray crystallography
All measurements for 1a, 1c, 2a, 2b, 3b and 3c were made on
CCD Bruker SMART APEX diffractometer. Crystallographic data
and refinement parameters are summarized in Table 1. Single crys-
tals suitable for X-ray crystallographic analyses for 1a and 1c were
obtained by slow evaporation their aqueous methanol solutions.
Compounds 2a and 2b were obtained by slow evaporation of tolu-
ene solutions while chloroform-methanol solutions were used for
crystallization of 3b and 3c. Data were collected [at 273(2) K, 2a;
153(2) K, 3b, 100(2) K, 1a, 1c, 2b, and 3c] using graphite-mono-
chromated Mo K
a radiation (k = 0.71073 Å). The program SMART
a
[47] was used for collecting frames of data, indexing reflection,
and determining lattice parameters, SAINT [47] for integration of
the intensity of reflections and scaling, SADABS [48] for absorption
correction and SHELXTL [49–50] for space group and structure deter-
mination. Full-matrix least-squares refinements on F2, using all
data, were carried out with anisotropic displacement parameters
applied to all non-hydrogen atoms. Hydrogen atoms were included
in geometrically calculated positions using a riding model and
were refined isotropically. The figures were created using DIAMOND
3.1d software [51].
[31] P.C. Srivastava, S. Bajpai, C. Ram, R. Kumar, R.J. Butcher, J. Organomet. Chem.
692 (2007) 2482–2490.
[32] P.C. Srivastava, S. Bajpai, R. Kumar, S. Srivastava, V. Singh, S. Dwivedi, R.J.
Butcher, Can. J. Chem. 85 (2007) 534–539.
[33] R.R. Holmes, Acc. Chem. Res. 22 (1989) 190–197.
[34] V.K. Jain, Coord. Chem. Rev. 135/136 (1994) 809–843.
[35] J. Beckmann, K. Jurkschat, Coord. Chem. Rev. 215 (2001) 267–300.
[36] V. Chandrasekhar, S. Nagendran, V. Baskar, Coord. Chem. Rev. 235 (2002) 1–52.

V. Chandrasekhar, A. Kumar / Journal of Organometallic Chemistry 694 (2009) 2628–2635
2635
[37] V. Chandrasekhar, R. Boomishankar, S. Singh, A. Steiner, S. Zacchini,
Organometallics 21 (2002) 4575–4577.
[45] A.I. Vogel, Vogel’s Textbook of Practical Organic Chemistry, 5th ed., Longman,
London, 1989.
[38] V. Chandrasekhar, R. Boomishankar, A. Steiner, J.F. Bickley, Organometallics 22
(2003) 3342–3344.
[46] N. Petragnani, J.V. Comasseto, Synthesis (1986) 1–30.
[47] SMART
& SAINT Software Reference Manuals, Version 6.45, Bruker Analytical X-
[39] A.G. Davies, Organotin Chemistry, Wiley–VCH, Weinheim, Germany, 2004.
[40] V. Chandrasekhar, K. Gopal, P. Thilagar, Acc. Chem. Res. 40 (2007) 420–434.
[41] V. Chandrasekhar, P. Singh, K. Gopal, Organometallics 26 (2007) 2833–2839.
[42] V. Chandrasekhar, R. Thirumoorthi, Organometallics 26 (2007) 5415–5422.
[43] V. Chandrasekhar, P. Thilagar, T. Senapati, Eur. J. Inorg. Chem. (2007) 1004–
1009.
ray Systems Inc., Madison, WI, 2003.
[48] G.M. Sheldrick, SADABS A Software for Empirical Absorption Correction, Ver.
2.05, University of Göttingen, Göttingen, Germany, 2002.
[49] SHELXTL Reference Manual, ver. 6.1, Bruker Analytical X-ray Systems Inc.,
Madison, WI, 2000.
[50] G.M. Sheldrick, SHELXTL ver. 6.12, Bruker AXS Inc., Madison, WI, 2001.
[51] K. Bradenburg, DIAMOND, ver. 3.1d, Crystal Impact GbR, Bonn, Germany, 2006.
[44] A. Bondi, J. Phys. Chem. 68 (1964) 441–451.