The interplay of secondary Te?N, Te?O, Te?I and I?I interactions, Te?π contacts and π-stacking in the supramolecular structures of [{2-(4-nitrobenzylideneamino)-5-methyl}phenyl](4- methoxyphenyl)tellurium dihalides

Article abstract of DOI:10.1016/j.jorganchem.2004.12.001

The unsymmetrically substituted diorganotellurium dihalides [2-(4,4′-NO₂C₆H₄CHNC₆H ₃Me]RTeX₂ (R = 4-MeOC₆H₄, X = Cl, 1a; Br, 1b; I, 1c; R = 4-MeC₆H₄; X = Cl, 2; R = C ₆H₅, X = Cl, 3) were prepared in good yields and characterized by solution and solid-state ¹²⁵Te NMR spectroscopy, IR spectroscopy and X-ray crystallography. In the solid-state, molecular structures of 1a and 1c possess scarcely observed 1,4-type intramolecular Te?N secondary interaction. Crystal packing of these compounds show an unusually rich diversity of intermolecular secondary, Te?O, Te?I and I?I interactions, Te?π contacts as well as extensive π-stacking of the organic substituents.

Full text of DOI:10.1016/j.jorganchem.2004.12.001

Journal of Organometallic Chemistry 690 (2005) 1350–1355
www.elsevier.com/locate/jorganchem
The interplay of secondary Teꢀ ꢀ ꢀN, Teꢀ ꢀ ꢀO, Teꢀ ꢀ ꢀI and
Iꢀ ꢀ ꢀI interactions, Teꢀ ꢀ ꢀp contacts and p-stacking in
the supramolecular structures of [{2-(4-nitrobenzylideneamino)-
5-methyl}phenyl](4-methoxyphenyl)tellurium dihalides
a,
a
a
a
Ashok K.S. Chauhan *, Anamika , Arun Kumar , Ramesh C. Srivastava ,
Ray J. Butcher , Jens Beckmann c,1, Andrew Duthie
b
c
a
Department of Chemistry, University of Lucknow, Lucknow 226 007, India
Department of Chemistry, Howard University, Washington, DC 20059, USA
b
c
Centre for Chiral and Molecular Technologies, Deakin University, Geelong 3217, Australia
Received 31 October 2004; accepted 1 December 2004
Available online 7 February 2005
Abstract
The unsymmetrically substituted diorganotellurium dihalides [2-(4,40-NO2C6H4CHNC6H3Me]RTeX2 (R = 4-MeOC6H4, X = Cl,
1a; Br, 1b; I, 1c; R = 4-MeC6H4; X = Cl, 2; R = C6H5, X = Cl, 3) were prepared in good yields and characterized by solution and
solid-state 125Te NMR spectroscopy, IR spectroscopy and X-ray crystallography. In the solid-state, molecular structures of 1a and
1c possess scarcely observed 1,4-type intramolecular Teꢀ ꢀ ꢀN secondary interaction. Crystal packing of these compounds show an
unusually rich diversity of intermolecular secondary, Teꢀ ꢀ ꢀO, Teꢀ ꢀ ꢀI and Iꢀ ꢀ ꢀI interactions, Teꢀ ꢀ ꢀp contacts as well as extensive
p-stacking of the organic substituents.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Intramolecular coordination; Secondary interactions; Diorganotellurium dihalides
1. Introduction
secondary Teꢀ ꢀ ꢀp [2] interactions remain comparatively
less understood. On the other hand secondary Teꢀ ꢀ ꢀN,
Teꢀ ꢀ ꢀO interactions have mostly been identified to exist
intramolecularly [3]. The formation of, in general, a five-
membered ring by chelation through secondary
Teꢀ ꢀ ꢀN(O) interaction is reported to modulate the stabil-
ity and reactivity of organotellurium derivatives with
important consequences upon their applications [4].
We have recently reported [5] the existence of strained
four-membered rings formed by 1,4-type intramolecular
secondary Teꢀ ꢀ ꢀO interaction among diorganotellurium
dihalides and their influence on the intermolecular sec-
ondary Teꢀ ꢀ ꢀX interaction.
The crystal structures of most diorganotellurium
dihalides are characterized by the presence of consider-
ably longer intermolecular Teꢀ ꢀ ꢀX secondary bonds.
The number and directionality of these interactions
and the influence on the geometry of the tellurium atoms
in diorganotellurium dihalides has been thoroughly
investigated [1]. By contrast the less commonly observed
*
Corresponding author. Tel.: +91 9415010763; fax: +91
5222740245.
E-mail address: akschauhan@hotmail.com (A.K.S. Chauhan).
1
We now describe the synthesis and full characteriza-
tion of five unsymmetrically substituted diorganotellu-
Present address: Institut fur Chemie, Freie Universita¨t Berlin,
¨
Fabeckstrasse 34-36, 14195 Berlin, Germany.
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.12.001

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 1350–1355
1351
rium dihalides, [2-(4,40-NO2C6H4CHNC6H3Me]RTeX2
(R = 4-MeOC6H4, X = Cl, 1a; Br, 1b; I, 1c; R = 4-
MeC6H4; X = Cl, 2; R = C6H5, X = Cl, 3). Compounds
1–3 may be considered as derivatives of 4-nitro-40-me-
thylbenzylidene aniline (NMBA), an organic substrate
known to possess second-order non-linear optical
(NLO) properties [6]. The crystal structures of 1a and
1c show an unusually rich diversity of secondary
Teꢀ ꢀ ꢀN, Teꢀ ꢀ ꢀO, Teꢀ ꢀ ꢀI and Iꢀ ꢀ ꢀI interactions, Teꢀ ꢀ ꢀp
contacts as well as extensive p-stacking in the solid-state.
A fundamental understanding of these non-covalent
bonds and their bearing on the packing order is a prere-
quisite in the context of crystal engineering [7].
bon atom [10]. Both these signals appear to be unaf-
fected by the electronegativity of the halogen. 125Te
NMR spectra of all the dihalides, 1–3 consist of a single
resonance. The 125Te MAS NMR chemical shift of 1a
(882 ppm) closely resembles the 125Te chemical shift in
CDCl3 (886 ppm) and suggests that the molecular struc-
tures are very similar in solution and the solid state. The
125Te chemical shifts (ꢁ882 ppm) of the dichlorides, 1a,
2, 3 are almost unaffected by the inductive effect of the R
group but move to upfield in case of the diiodide, 1c (840
ppm) with respect to the dichloride, 1a. The case of the
dibromide, 1b (777 ppm) is surprising. A telluronium
type structure for 1b, [RR0TeBr]+Br0, which could possi-
bly explain this large upfield shift is not supported by
conductivity measurements in acetonitrile. Repeated at-
tempts to grow single crystal of 1b failed due to its ten-
dency to deposit Te metal in solution on standing.
2. Results and discussion
2.1. Synthetic aspects
2.2. Crystal and molecular structure of 1a and 1c
The diorganotellurium dichlorides, 1a, 2 and 3 were
obtained in good yield, by transmetallation of aryl-
tellurium trichlorides, RTeCl3 (R = 4-MeOC6H4,
4-MeC6H4, C6H5) with [{2-(4-nitrobenzylideneamino)-
5-methyl}phenyl]mercury chloride, R0HgCl (R0 = 2-
(4,40-NO2C6H4CHNC6H3Me)) using a slightly modified
method of Wu and coworkers [8] (Scheme 1). The halide
exchange reaction of 1a with KBr and KI provided the
related diorganotellurium dibromide and diiodide,
R0(4-MeOC6H4)TeX2 (X = Br, 1b; I, 1c) in very good
yield (Scheme 1).
Compounds 1–3 were obtained as yellow, red/brown
crystalline solids that are soluble in chloroform and
dichloromethane and were characterized by multinu-
clear NMR spectroscopy and IR spectroscopy. The IR
spectra of all the compounds show absorption bands
at ꢁ1620 cmꢂ1 due to m(C@N) which is comparable to
that reported for R0HgCl [9]. The 1H NMR spectra con-
sist of a high field (ꢁ8.8 ppm) signal for the methine pro-
ton in addition to the Me/OMe and ring proton signals
[8]. The tellurated C atom of the N-ring, as expected, is
deshielded and appears at ꢁ132 ppm in the 13C NMR
spectra of 1–3 as compared to the free Schiff base. The
signal at ꢁ144 ppm can be assigned to the methine car-
The molecular and crystal structures of 1a and 1c are
shown in Figs. 1–4. Relevant crystal data and selected
bond parameters are collected in Tables 1 and 2. Consis-
tent with the VSEPR theory, the geometry of the tellu-
rium atoms in 1a and 1c can be described as distorted
trigonal bipyramidal when considering the primary
coordination sphere with the C2X2 donor set (X = Cl,
I) and the stereochemically active lone pair (Figs. 1
and 3). The average (primary) Te–C, Te–Cl and Te–I
bond lengths resemble values reported for other diorg-
anotellurium dihalides [1]. In the secondary coordina-
tion sphere of 1a and 1c, the tellurium atoms are
intramolecularly coordinated (1,4-type) by the azome-
thine N atom of the Schiff base moieties (Figs. 1and
3). The shorter Teꢀ ꢀ ꢀN internuclear distances and re-
duced N1–C2–C1 and Te–C1–C2 bond angles indicate
the attractive secondary Teꢀ ꢀ ꢀN interaction in 1a and
1c to be fairly strong though weaker than that operative
in
[(C6H5)(2-Me2NCH2C6H4)TeX]+Xꢂ
˚
(Teꢀ ꢀ ꢀN =
2.389(12), X = Br [11] and 2.44(2) A, X = I [12]) Pres-
ence of less strained five membered ring and positive
charge on tellurium in case of the latter are probably
responsible for the stronger secondary Teꢀ ꢀ ꢀN interac-
- HgCl2
KX
RTeCl3 + R'HgCl
RR'TeCl2
RR'TeX2
X = Br, I
1a, R = 4-MeOC6H4
2, R = 4-MeC6H4
3, R = C6H5
1b, X = Br
1c, X = I
H
O2N
N
C
R' =
Scheme 1.

1352
A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 1350–1355
shortest distance between two Cl atoms in the crystal
˚
structure is 4.416(2) A (between Cl1 and Cl2 of an adja-
cent molecule). However, the proximity of the tellurium
to a methoxy group of an adjacent molecule suggests
that a Teꢀ ꢀ ꢀp interaction is operative (Fig. 2). The
Teꢀ ꢀ ꢀp and p (C = Y)ꢀ ꢀ ꢀp (C = Y) contacts associated
with quinoid electron delocalization across the para-
methoxy phenyl as well as the NMBA fragments appear
to be the intermolecular associative forces in absence of
Teꢀ ꢀ ꢀCl and Clꢀ ꢀ ꢀCl interactions. In the solid-state, com-
pound 1c contains two crystallographically independent,
yet similar conformers featuring Te1A and Te1B (Fig.
4). Besides the intramolecular N-coordination, the sec-
ondary coordination spheres of Te1A and Te1B are de-
Fig. 1. Molecular structure of 1a showing 30% probability displace-
ment ellipsoids and the crystallographic numbering scheme.
˚
tion. In contrast to many other diorganotellurium
dichlorides, compound 1a shows no secondary Teꢀ ꢀ ꢀCl
interactions [1]. Also there is no evidence for secondary
Clꢀ ꢀ ꢀCl interactions in the crystal structure of 1a; the
fined by a secondary Teꢀ ꢀ ꢀO interaction of 3.258(9) A
(O1A of an adjacent nitro group; symmetry operation:
1 ꢂ x, 2 ꢂ y, 3 ꢂ z) and a secondary Teꢀ ꢀ ꢀI interaction
˚
of 3.927(8) A (I2B of an adjacent molecule; symmetry
Fig. 2. Crystal structure of 1a, viewed along the a-axis.
Fig. 3. Molecular structure of one of the two crystallographically independent conformers of 1c showing 30% probability displacement ellipsoids and
the crystallographic numbering scheme.

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 1350–1355
1353
Fig. 4. Crystal structure of 1c, viewed along the a-axis.
Table 1
Crystal data and structure refinement for 1a and 1c
1a
1c
Formula
Formula weight (g molꢂ1
Crystal system
C
21H18Cl2N2O3Te Æ 0.5CHCl3
C21H18I2N2O3Te
727.77
Triclinic
)
604.56
Monoclinic
0.25 · 0.30 · 0.55
C2/c
Crystal size, mm
Space group
0.08 · 0.40 · 0.95
ꢀ
P1
˚
a (A)
24.501(3)
7.6443(10)
25.868(4)
90
10.0878(17)
15.491(3)
16.247(3)
77.616(3)
82.594(3)
86.944(4)
2458.2(7)
4
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
101.421(2)
90
3
˚
V (A )
4748.8(11)
8
1.691
Z
Dcalc Mg mꢂ3
T (K)
1.966
148(2)
103(2)
1.673
l (mmꢂ1
F(000)
)
3.744
1360
2376
17616
Number of reflections collected
Number of independent reflections/Rint
Number of reflections observed with (I > 2r(I))
R1(F)(I > 2r(I))
12756
8498
5787
4900
7017
0.046
0.022
0.065
wR2F2 (all data)
0.127
0.00078(18)
(D/r)max
Largest difference peak/hole (e A
0.00010(4)
0.551/ꢂ0.446
ꢂ3
˚
)
1.367 (near Te)/ꢂ1.390 (near Te)
operation: 1 ꢂ x, 3 ꢂ y, 1 ꢂ z), respectively. In the crys-
tal structure of 1c there is also a secondary Iꢀ ꢀ ꢀI contact
3. Experimental
˚
of 3.711(5) A between I1A and I2B (symmetry opera-
3.1. General
tion: 1 ꢂ x, 3 ꢂ y, 2 ꢂ z), which is comparable to those
reported previously for other diorganotellurium diiod-
ides [13]. Compounds 1a and 1c crystallize in centrosym-
metric space groups and in their crystal lattice
symmetry-related N-(4-methylphenyl)-4-nitrobenzalede-
neimine moieties are associated by extensive p-stacking
and adopt head-to-tail conformations similar to the
NMBA molecules in the triclinic modification (Figs. 2
and 4). Consequently, all putative second-order NLO ef-
fects are expected to be nullified [6].
Preparative work was performed under dry nitrogen.
The starting materials [{2-(4-nitrobenzylideneamino)-5-
methyl}phenyl]mercury chloride and aryltellurium tri-
chlorides were prepared according to literature methods
[9,14]. Solution 1H (300.13 MHz), 13C (75.47 MHz) and
125Te (85.29 MHz) NMR spectra were recorded in
CDCl3 on Varian 300 DRX, 300 Unity Plus and JEOL
GX 270 NMR spectrometers, using Me4Si and Me2Te
as internal standards. Solid-state 125Te (126.2 MHz)

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A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 1350–1355
Table 2
130.11, 130.54, 133.86, 137.27, 144.22, 156.65, 162.38.
125Te NMR: d 886.2. 125Te MAS NMR: diso 882.4 (g:
0.45 f: 313; r11: ꢂ1110, r22: ꢂ969, r33: ꢂ570).
˚
Selected bond parameters (A, ꢁ) for 1a and 1c
1a (X = Cl)
1c (X = I)
Compounds 2 and 3 were prepared similarly. For (4-
methylphenyl)[{2-(4-nitrobenzylideneamino)-5-methyl}
phenyl]tellurium dichloride, 2, Yield: (63%); m.p. 230
ꢁC. Anal. Found: C, 47.47; H, 3.21; N, 5.46; Cl, 13.07;
Te, 25.07. Calcd. for C21H18N2O2Cl2Te (528.89): C,
47.69; H, 3.43; N, 5.30; Cl, 13.41; Te, 24.12. IR
Molecule A
Molecule B
Te1–X1
Te1–X2
2.507(1)
2.475(1)
2.879(2)
2.107(3)
2.104(3)
175.04(2)
81.44(5)
87.65(6)
89.89(6)
96.58(5)
87.52(7)
89.67(6)
53.61(8)
150.48(8)
98.12(9)
2.933(3)
3.022(3)
2.958(7)
2.159(7)
2.172(7)
174.97(2)
79.17(9)
90.94(17)
92.04(17)
95.89(9)
85.33(17)
91.79(17)
53.79(19)
149.37(19)
97.61(23)
2.993(2)
2.953(2)
Te1–N1
Te1–C1
Te1–C15
2.888(7)
2.152(7)
2.174(7)
X1–Te1–X2
X1–Te1–N1
X1–Te1–C1
X1–Te1–C15
X2–Te1–N1
X2–Te1–C1
X2–Te1–C15
N1–Te1–C1
N1–Te1–C15
C1–Te1–C15
170.41(2)
84.78(10)
84.44(17)
93.74(17)
85.67(10)
89.21(17)
94.17(17)
54.13(19)
151.24(19)
97.12(23)
1
(cmꢂ1): 1624.0 (mCH@N). H NMR: d 2.38 (s), 2.56 (s),
7.42–8.40 (m), 8.88 (s). 13C NMR: d 21.47, 76.58,
116.42, 124.21, 130.05, 130.63, 130.83, 133.78, 135.42,
140.44, 141.13, 142.49, 156.56. 125Te NMR: d 880.0.
For (phenyl)[{2-(4-nitrobenzylideneamino)-5-methyl}
phenyl]tellurium dichloride, 3, Yield: (55%); m.p. 252
ꢁC. Anal. Found: C, 45.88; H, 3.32; N, 5.18; Cl, 14.00;
Te, 25.12. Calcd. for C20H16N2O2Cl2Te (514.86): C,
46.65; H, 3.13; N, 5.44; Cl, 13.77; Te, 24.78. IR
1
(cmꢂ1): 1621.5 (mCH@N). H NMR: d 2.356 (s), 7.428–
CP MAS NMR spectra were acquired using a JEOL
Eclipse Plus 400 NMR spectrometer equipped with a
high speed locked 4 mm probe operating at spinning fre-
quencies between 8 and 9 KHz. Experimental condition:
pulse width 1 ms, relaxation delay 120 s, 400–900 tran-
sients. The isotropic chemical shifts are referenced
against Me2Te using solid Te(OH)6 as the secondary ref-
erence (diso 692.1, 685.5) [15]. Definitions diso(ppm) =
ꢂriso = ꢂ(r11 + r22 + r33)/3; f (ppm) = r33 ꢂ riso and
g = (r22 ꢂ r11)/(r33 ꢂ riso) where r11, r22 and
r33 (ppm) are the principal tensor components of the
shielding anisotropy (SA), sorted as follows
jr33 ꢂ riso| > |r11 ꢂ riso| > |r22 ꢂ riso|. IR spectra were
recorded as KBr pellets using a Perkin–Elmer RX1
Spectrometer. Microanalyses were carried out using a
Carlo Erba 1108 make analyzer. Tellurium was esti-
mated volumetrically and the halogen content gravimet-
rically as silver halide [16].
8.417 (m), 8.897 (s). 13C NMR: d 21.62, 77.09, 116.58,
124.37, 129.97, 130.18, 130.58, 131.91, 134.00, 135.68,
140.51, 141.36, 156.75. 125Te NMR: d 881.1.
3.3. Synthesis of (4-methoxyphenyl)[{2-(4-
nitrobenzylideneamino)-5-methyl}phenyl]tellurium
dibromide (1b) and diiodide (1c)
A solution of 1a (550 mg, 1.00 mmol) in chloroform
(50 mL) was stirred with a twofold excess of KI for 12 h.
A colour change from yellow to red occurred. The mix-
ture was filtered and the solvents reduced to approxi-
mately one fifth in vacuo. Addition of petroleum ether
40–60 ꢁC (10 mL) induced crystallization, providing
red/brown crystals of 1c. Yield (611 mg, 84%); m.p.
196 ꢁC. Anal. Found: C, 34.88; H, 2.54; N, 4.03; I,
34.52; Te, 17.07. Calcd. for C21H18N2O3I2Te (727.82):
C, 34.66; H, 2.42; N, 3.84; I, 34.87; Te, 17.53. IR
1
(cmꢂ1): 1615.5 (mCH@N). H NMR: d 2.39 (s), 3.93 (s),
3.2. Synthesis of (4-methoxyphenyl)[{2-(4-
nitrobenzylideneamino)-5-methyl}phenyl]tellurium
dichloride (1a)
7.03–8.43 (m), 8.90 (s). 13C NMR: d 21.56, 55.62,
115.83, 116.57, 124.29, 131.10, 130.13, 133.86, 138.73,
144.18, 156.46, 162.31. 125Te NMR: d 840.7.
A
solution of [{2-(4-nitrobenzylideneamino)-5-
1b was prepared similarly from 1a and KBr. Yield:
(82%); m.p. 180 ꢁC. Anal. Found: C, 39.73; H, 2.64;
N, 4.60; Br, 24.10; Te, 21.07. Calcd. for
C21H18N2O3Br2Te (633.79): C, 39.80; H, 2.86; N, 4.42;
methyl}phenyl]mercury chloride (2.37 g, 5.00 mmol)
and 4-methoxyphenyltellurium trichloride (1.70 g, 5.00
mmol) in chloroform (250 ml) was heated under reflux
for 20 h. Precipitated HgCl2 was filtered off and the sol-
vents reduced to approximately one fifth in vacuo. Addi-
tion of petroleum ether (b.p. 40–60 ꢁC) (50 mL) induced
the precipitation of solid, which was recrystallized twice
from CHCl3 to give yellow crystals of 1a. Yield: (1.88 g,
66%); m.p. 220 ꢁC. Anal. Found: C, 42.68; H, 3.06; N,
4.80; Cl, 20.03; Te, 20.87. Calcd. for C21H18N2O3Cl2-
Te Æ 0.5CHCl3 (604.61): C, 42.71; H, 3.08; N, 4.63; Cl,
20.52; Te, 21.11. IR (cmꢂ1): 1623.5 (mCH@N). 1H
NMR: d 2.36 (s), 3.94 (s), 7.15–8.41 (m), 8.88 (s). 13C
NMR: d 21.56, 55.63, 115.75, 116.49, 118.75, 124.29,
1
Br, 25.21; Te, 20.13. IR (cmꢂ1): 1620.5 (mCH@N). H: d
2.355 (s), 3.935 (s), 7.154–8.407 (m), 8.881 (s). 13C
NMR: d 21.54, 55.59, 116.11, 116.77, 124.34, 130.18,
132.19, 133.71, 140.46, 144.12, 156.07, 162.15. 125Te
NMR: d 777.1.
4. Crystallography
Single crystals of 1a and 1c suitable for X-ray crys-
tallography were obtained by slow evaporation of

A.K.S. Chauhan et al. / Journal of Organometallic Chemistry 690 (2005) 1350–1355
1355
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˚
mated Mo Ka (0.7107 A) radiation. Data were reduced
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and SADABS [17]. The structures were solved by direct
methods and difference Fourier synthesis using
SHELXS-97 implemented in the program WINGX 2002
[18]. Full-matrix least-squares refinements on F2, using
all data, were carried out with anisotropic displacement
parameters applied to all non-hydrogen atoms. Hydro-
gen atoms were included in geometrically calculated
positions using a riding model and were refined isotrop-
ically. Crystallographic parameters and details of the
data collection and refinement are given in Table 1. Fig-
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5. Supplementary material
Crystallographic data for the structure analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC No. for 1a 246743 and for 1c is
246745. Copies of this information may be obtained free
of charge from the Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, U.K. Fax: +44-1223-336-033; or
E-mail: deposite@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk.
[9] K. Ding, Y. Wu, H. Hu, L. Shen, X. Wang, Organometallics 11
(1992) 3849.
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[11] M.R. Detty, A.E. Friedman, M. McMillan, Organometallics 13
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[12] M.R. Detty, A.J. Williams, J.M. Hewitt, M. McMillan, Organo-
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[13] For secondary Iꢀ ꢀ ꢀI interactions in R2TeI2, see J.D. McCullough,
C. Knobler, R.F. Ziolo, Inorg. Chem. 24 (1985) 1814, and
references cited therein.
Acknowledgements
[14] (a) G.T. Morgan, R.E. Kellett, J. Chem. Soc. (1926) 1080;
(b) W.R. McWhinnie, P. Thavornyutikarn, J. Chem. Soc. Dalton
Trans. (1972) 551.
The financial assistance by the University Grants
Commission, New Delhi, India is gratefully
acknowledged.
[15] M.J. Collins, J.A. Ripmeester, J.F. Sawyer, J. Am. Chem. Soc.
109 (1987) 4113.
[16] (a) For the quantitative Te determination, see F.H. Kruse, R.W.
Sauftner, J.F. Suttles, Anal. Chem. 25 (1953) 500;
(b) A.I. Vogel, A Text Book of Quantitative Inorganic Analysis,
third ed., Longmans, London, 1962, For the quantitative halide
determination, see.
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¨