Hybrid (Te, N) and (N, Te, N) ligands having pyrrolidine ring and their palladium(II) and mercury(II) complexes: Synthesis and crystal structures

Article abstract of DOI:10.1016/j.jorganchem.2003.08.024

Reactions of (2-choroethyl)pyrrolidine hydrochloride with ArTe ^- or Te^2- generated in situ by borohydride reduction of Ar₂Te₂ or elemental tellurium give N-{2-(4-methoxyphenyltelluro)ethyl}pyrrolidine (L¹) or bis{2-(pyrrolidine-N-yl)ethyl}telluride (L²), respectively, as viscous liquids, which are characterized by ¹H- and ¹³C{¹H}-NMR spectroscopy. The potentially bidentate hybrid organotellurium ligand (L¹) reacts with HgBr ₂ and Na₂PdCl₄ to give complexes [HgBr₂·L¹] (1) and [PdCl₂ ·L¹] (2) respectively. The potentially tridentate ligand (L²) also forms a complex [HgBr₂·L ²] (3). All three complexes give characteristic ¹ H- and ¹³C{¹H}-NMR spectra, although the deshielding of carbon atoms linked to Te/N as well as protons attached to them is small in the case of both Hg complexes. The single crystal structures of 1-3 have been solved. In 1 and 2 the ligand L¹ coordinates via Te and N both with metal indicating that the pyrrolidine N has good ligating strength. The Pd-Te and Hg-Te bond lengths are 2.4781(3) and 2.747(1) A?, respectively. The Pd-Cl trans to Te (2.3915(7) A?) is longer than other Pd-Cl bond length. There are two independent molecules in the asymmetric unit of 3 that have essentially the same bidentate molecular structures. There is no evidence of significant intermolecular Hg-Br bonding. The Hg-Te bond in 3 (ave. 2.686(2) A?) is shorter than in 1. The potentially tridentate ligand L² in complex 3 coordinates only as a bidentate donor. The molecular weights of 1 and 2 are close to double the formula weight indicating strong molecular association in solution. Te-C(alkyl) is somewhat longer than Te-C(aryl) for complexes 1 and 2.

Full text of DOI:10.1016/j.jorganchem.2003.08.024

Journal of Organometallic Chemistry 688 (2003) 20Á26
/
www.elsevier.com/locate/jorganchem
Hybrid (Te, N) and (N, Te, N) ligands having pyrrolidine ring and
their palladium(II) and mercury(II) complexes: synthesis and crystal
structures
Garima Singh a, Ajai K. Singh a,*, Pankaj Sharma a, John E. Drake b,
Michael B. Hursthouse c, Mark E. Light c
a Department of Chemistry, Indian Institute of Technology, New Delhi 110016, India
b Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ont., Canada N9B 3P4
c Department of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
Received 26 June 2003; received in revised form 11 August 2003; accepted 21 August 2003
Abstract
Reactions of (2-choroethyl)pyrrolidine hydrochloride with ArTeꢀ or Te2ꢀ generated in situ by borohydride reduction of Ar2Te2
or elemental tellurium give N-{2-(4-methoxyphenyltelluro)ethyl}pyrrolidine (L1) or bis{2-(pyrrolidine-N-yl)ethyl}telluride (L2),
1
respectively, as viscous liquids, which are characterized by H- and 13C{1H}-NMR spectroscopy. The potentially bidentate hybrid
organotellurium ligand (L1) reacts with HgBr2 and Na2PdCl4 to give complexes [HgBr2×
/
L1] (1) and [PdCl2×
/
L1] (2) respectively. The
potentially tridentate ligand (L2) also forms a complex [HgBr2×
/
L2] (3). All three complexes give characteristic H- and 13C{1H}-
1
NMR spectra, although the deshielding of carbon atoms linked to Te/N as well as protons attached to them is small in the case of
both Hg complexes. The single crystal structures of 1Á
3 have been solved. In 1 and 2 the ligand L1 coordinates via Te and N both
with metal indicating that the pyrrolidine N has good ligating strength. The PdÃTe and HgÃTe bond lengths are 2.4781(3) and
Cl trans to Te (2.3915(7) A) is longer than other PdÃCl bond length. There are two independent
molecules in the asymmetric unit of 3 that have essentially the same bidentate molecular structures. There is no evidence of
/
/
/
˚
˚
2.747(1) A, respectively. The PdÃ
/
/
˚
significant intermolecular HgÃ
ligand L2 in complex 3 coordinates only as a bidentate donor. The molecular weights of 1 and 2 are close to double the formula
weight indicating strong molecular association in solution. TeÃC(alkyl) is somewhat longer than TeÃC(aryl) for complexes 1 and 2.
# 2003 Elsevier B.V. All rights reserved.
/
Br bonding. The HgÃ
/
Te bond in 3 (ave. 2.686(2) A) is shorter than in 1. The potentially tridentate
/
/
Keywords: N-{2-(4-Methoxyphenyltelluro)ethyl}pyrrolidine; Bis{2-(pyrrolidine-N-yl)ethyl}telluride; Mercury; Palladium; Hybrid organotellurium
ligand; Complexes; Crystal structure
1. Introduction
FT-NMR for studies of behaviour in solution. Hybrid
organotellurium ligands have also received attention in
the last decade. They generally have oxygen, sulfur and
There are several reasons for the growing interest in
tellurium ligands [1Á4] over the last decade. Among
/
nitrogen as the donor sites along with tellurium [1Á
There are two types of hybrid organotellurium ligands
[1Á3] containing tellurium and nitrogen as donor sites:
(i) the ÃNR2 group is attached to an alkyl or aryl group
based skeleton and (ii) nitrogen is a part of a hetero-
cyclic ring. In the latter case it has been observed that
coordination via nitrogen is not realized when nitrogen
/
3].
those of importance are the increasing evidence of
enhanced ligating properties of telluroether ligands
compared to thioethers [1b], the availability of standar-
dized synthetic routes to the ligands, the possibility of
using metal complexes of Te-ligands as a precursor for
/
/
IIÁVI semiconductors, and the improved availability of
/
is a part of morpholine or phthalimide systems [5Á8] but
/
the nitrogen readily coordinates [9] when a pyridine ring
provides the nitrogen of the hybrid ligand. It was
therefore thought worthwhile to design suitable hybrid
* Corresponding author. Fax: ꢁ91-11-2686-2037.
E-mail address: aksingh@chemistry.iitd.ac.in (A.K. Singh).
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.08.024

G. Singh et al. / Journal of Organometallic Chemistry 688 (2003) 20Á
/26
21
organotellurium ligands having other nitrogen hetero-
cyclic ring systems, to improve the understanding of
such ligands containing nitrogen as a co-donor site.
Therefore, N-{2-(4-methoxyphenyltelluro)ethyl}pyrroli-
dine (L1) and bis{2-(pyrrolidine-N-yl)ethyl}telluride
(L2) were synthesized by reaction of the nucleophiles
4-MeC6H4Teꢀ and Te2ꢀ with the appropriate organic
halide.
experimental parameters. An absorption correction was
applied [11] but in the case of [HgBr2×
L2] the weak
quality of the data was such that an effective absorption
/
correction was difficult.
The structures of all three complexes were solved by
direct methods [12] and were refined (by full-matrix
least-squares on F2) using the WinGX version [13] of
SHELX-97 [14]. All of the non-hydrogen atoms were
treated anisotropically. Hydrogen atoms were included
in idealized positions with isotropic thermal parameters
set at 1.2 times that of the carbon atom to which they
were attached. The final cycles of full-matrix least-
squares refinement converged (largest parameter shift
was 0.001 times its esd). They were based on 3543
observed reflections (3261 for F2
variable parameters for [PdCl2×
reflections (3313 for F2ꢁ4s(F2)) and 174 variable
parameters for [HgBr2×
L1] and 8080 observed reflec-
tions (5116 for F2ꢁ4s(F2)) and 326 variable parameters
for [HgBr2×
L2]. Selected distances and bond angles of
ꢁ
/
4s(F2)) and 174
/
L1], 4002 observed
/
/
The complexation of L1 and L2 with Pd(II) and Hg(II)
has been investigated. The characterization of the
complexes [HgBr2(L1)] (1), [PdCl2(L1)] (2) and
[HgBr2(L2)] (3) by single crystal X-ray diffraction
reveals that the nitrogen donor site of these ligands
coordinates readily, even with Hg(II). The results of
these investigations are reported in this paper.
/
/
the three complexes are given in Tables 1 and 2 and the
molecules are displayed in the ORTEP diagrams given in
Figs. 1Á3.
/
2.2. Synthesis of N-{2-(4-
methoxyphenyltelluro)ethyl}pyrrolidine (L1)
2. Experimental
Bis(4-methoxyphenyl)ditelluride (0.50 g,1.0 mmol)
was dissolved in 30 cm3 of EtOH and the solution set
to reflux under nitrogen atmosphere. A solution of
sodium borohydride in NaOH (5%) was added dropwise
to the refluxing solution of the ditelluride under nitrogen
atmosphere until it became colourless due to the
formation of ArTeꢀ Naꢁ. (2-Choroethyl)pyrrolidine
hydrochloride (0.362 g, 2.0 mmol) dissolved in 5 cm3 of
EtOH was added to this solution with constant stirring.
The C and H analyses were carried out with a PerkinÁ
/
Elmer elemental analyzer 240 C. Tellurium was esti-
1
mated by atomic absorption spectrometry. The H- and
13C{1H}-NMR spectra were recorded on a Bruker
Spectrospin DPX-300 NMR spectrometer at 300.13
and 75.47 MHz respectively. IR spectra in the range
4000Á
250 cmꢀ1 were recorded on a Nicolet Prote´ge 460
FTIR spectrometer as KBr and CsI pellets. The
conductance measurements were made in MeCN (con-
/
The reaction mixture was refluxed further for 2Á3 h,
/
centration ꢀ
meter model 162. The molecular weights (concentration
5 mM) in chloroform were determined with a Knauer
/1 mM) using an ORION conductivity
cooled to room temperature (r.t.) and poured into ice
cold water (20 cm3) in which 0.1 g of NaOH was
dissolved. The ligand was extracted into chloroform
(200 cm3) from this aqueous mixture. The extract was
washed with water and dried over anhydrous sodium
sulphate. The solvent was evaporated off under reduced
pressure on a rotary evaporator, resulting in a red oil,
which was extracted into hexane. Further hexane was
removed under reduced pressure to get ligand L1 as clear
ꢀ
/
vapour pressure osmometer model A0280. The melting
points determined in open capillary are reported as such.
2.1. X-ray diffraction analysis
The crystals were mounted on a glass fibre. Data were
collected on an Enraf Nonius Kappa CCD area detector
diffractometer, with 8 and v scans chosen to give a
yellow oil. Yield 70%. LM, 14.4 ohmꢀ1 cm2 molꢀ1
.
Anal. Found: Te, 38.01. Calc. for C13H19ONTe: Te,
38.36%. NMR: 1H (CDCl3, 25 8C): d (vs Me4Si): 1.68 (s,
4H, H4), 2.45 (s, 4H, H3), 2.81 (t, 2H, H1), 2.94 (t, 2H,
H2), 3.78 (s, 3H, OCH3), 6.66 (d, 2H, ArH m to Te),
7.61 (d, 2H, ArH o to Te); 13C{1H}-NMR (CDCl3,
25 8C): d (vs Me4Si): 8.80 (C1), 23.33 (C4), 54.38 (C3),
57.44 (C2), 58.50 (OCH3), 101.93 (ArC-Te), 114.92 (ArC
m to Te), 140.53 (ArC o to Te),161.36 (ArC p to Te).
complete asymmetric unit. For [PdCl2×
/
L1] (2) and
[HgBr2×
/
L2] (3) cell refinement [10] gave cell constants
corresponding to a monoclinic cells whose dimensions
are given in Table 1 along with other experimental
parameters. Cell refinement [10] for [HgBr2×
/
L1] (1) gave
cell constants corresponding to a triclinic cell whose
dimensions are also given in Table 1 along with other

22
G. Singh et al. / Journal of Organometallic Chemistry 688 (2003) 20Á26
/
Table 1
Crystal data and structure refinement for 1, 2 and 3
1
2
3
Empirical formula
Colour
C
13H19NOBr2TeHg
C13H19Cl2NOPdTe
Red
510.19
C24H48N4Br4Hg2Te2
White
1368.68
Colourless
693.30
120(2)
Formula weight
Temperature (K)
˚
Wavelength (A)
120(2)
0.71073
120(2)
0.71069
0.71069
Triclinic
¯
P1
Crystal system
Space group
Monoclinic
C2/c
Monoclinic
P2(1)/c
˚
a (A)
8.887(5)
9.563(5)
11.695(5)
99.585(5)
109.038(5)
108.705(5)
848.1(7)
2
24.9350(4)
8.5322(2)
16.1710(3)
11.745(5)
13.054(5)
23.787(5)
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
Á/
Á/
Á/
Á/
115.019(1)
Á/
3
˚
V (A )
Z
3117.6(1)
8
3647(2)
4
Dcalc (g cmꢀ3
)
2.715
15.463
628
2.174
3.359
1952
2.493
14.380
2496
Absorption coefficient (mmꢀ1
F(000)
)
Crystal size (mm)
0.20ꢂ
28.13
115h 5
155l 515
13 037
4002 [Rint
/
0.20ꢂ
/
0.04
0.40ꢂ
3.08Á27.47
295h 5
205l 520
14 093
3543 [Rint
/
0.15ꢂ
/
0.06
0.10ꢂ
3.01Á27.49
155h 5
305l 530
14 271
8080 [Rint
/
0.07ꢂ
/
0.07
u range for data collection (8) 4.94Á
Index ranges
/
/
/
ꢀ/
/
/
10, ꢀ
/
125
/
k 5
/
12, ꢀ
/
ꢀ/
/
/32, ꢀ
/
115
/
k 5
/
10, ꢀ
/
ꢀ/
/
/15, ꢀ
/
145
/
k 5
/
16, ꢀ
/
/
/
/
/
/
/
Reflections collected
Independent reflections
Max. and min. transmission
Goodness-of-fit on F2
Final R indices [F2ꢁ
R indices (all data)
Extinction coefficient
ꢃ/0.0492]
ꢃ/0.0482]
ꢃ/0.0651]
0.5767 and 0.1480
1.000
0.8239 and 0.3468
1.050
0.4326 and 0.3273
0.986
/
4s(F2)]
R1ꢃ
R1ꢃ
0.0011(3)
1.982 and ꢀ
/
0.0321, wR2ꢃ
/
0.0708
0.0769
R1ꢃ
R1ꢃ
0.00040(6)
1.408 and ꢀ
/
0.0274, wR2ꢃ
/0.0678
R1ꢃ
R1ꢃ
0.00038(7)
3.196 and ꢀ4.555
/0.0681, wR2ꢃ
/0.1501
/
0.0476, wR2ꢃ
/
/
0.0308, wR2ꢃ
/0.0697
/0.1180, wR2ꢃ
/0.1736
Largest difference peak and
ꢀ3
/2.777
/1.478
/
˚
hole (e A
)
2.3. Synthesis of bis{2-(pyrrolidine-N-yl)ethyl}telluride
(L2)
25 8C): d (vs Me4Si): 0.14 (C1), 22.66 (C4), 53.01 (C3),
59.91(C2).
2.4. Synthesis of [HgBr2(L1)] (1)
Tellurium powder (0.65 g, 5.0 mmol) and sodium
borohydride (0.38 g, 10.0 mmol) solution (made in 10
cm3 of 2.0 M NaOH) were mixed in 50 cm3 of water.
The mixture was refluxed for 2 h under nitrogen
atmosphere. The resulting colourless thin slurry of
Na2Te was kept under reflux, and a solution of (2-
chloroethyl)pyrrolidine hydrochloride (1.70 g,10.0
mmol) made in 5 cm3 of EtOH was added dropwise,
with constant stirring under nitrogen. The mixture was
cooled to r.t. and poured into 100 cm3 of water. The
ligand L2 was extracted into Et2O from the aqueous
phase. The ether extract was washed with distilled water
and dried over anhydrous Na2SO4. On evaporating off
ether under reduced pressure on a rotary evaporator L2
was obtained as an orange yellow viscous liquid, which
was found to be unstable as it showed signs of decay
within few days. Yield 60%. LM, 5.22 ohmꢀ1 cm2
molꢀ1. Anal. Found: Te, 38.66. Calc. for C13H24N2Te:
HgBr2 (0.20 g, 0.55 mmol) dissolved in acetone (15
cm3) was added to the solution of L1 (0.18 g, 0.55 mmol)
made in chloroform (20 cm3). The resulting mixture was
stirred at r.t. until all of the L1 complexed (monitored by
TLC). Thereafter, the solvent from the mixture was
evaporated off under reduced pressure on a rotary
evaporator. The resulting residue was dissolved in 20
cm3 of chloroform and filtered through celite. The
filtrate was concentrated to 10 cm3 and mixed with 20
cm3 of hexane. A colourless complex separated out
which was filtered and dried in vacuo. The single
crystals of the complex were grown from chloroform
over layered with hexane. Yield, 70%; m.p. 110 8C. Mol.
wt.: Found, 1310; calc. 1368.7. LM, 17.88 ohmꢀ1 cm2
molꢀ1. Anal. Found: C, 22.16; H, 2.56; N, 2.40; Te,
18.41. Calc. for C13H19Br2HgNOTe: C, 22.51; H, 2.74;
1
N, 2.02; Te,18.60%. NMR: H (CDCl3, 25 8C): d (vs
1
Te, 39.43%. NMR: H (CDCl3, 25 8C): d (vs Me4Si):
Me4Si): 1.25 (m, 4H, H4), 2.03 (t, 4H, H3), 2.66 (m, 2H,
H1), 3.04 (m, 2H, H2), 3.83 (s, 3H, OCH3), 6.92 (d, 2H,
ArH m to Te), 7.86 (d, 2H, ArH o to Te); 13C{1H}
1.68Á
/
1.76 (m, 8H, H4), 2.45Á
/
2.52 (m, 8H, H3), 2.70Á
/
2.85 (m, 8H, H2 and H1); 13C{1H}: d (vs TMS) (CDCl3,

G. Singh et al. / Journal of Organometallic Chemistry 688 (2003) 20Á
/26
23
Table 2
1
Bond lengths (A) and angles (8) for HgBr2L (1) and PdCl2L1 (2)
˚
Bond lengths
1
2
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Te(1)Ã
Te(1)Ã
/
Br(1)
Br(2)
Te(1)
N(1)
2.578(1)
2.537(1)
2.747(1)
2.457(4)
2.122(6)
2.172(5)
1.467(7)
1.482(7)
1.476(7)
1.515(9)
1.523(9)
1.538(9)
1.526(8)
Pd(1)Ã
Pd(1)Ã
Pd(1)Ã
Pd(1)Ã
Te(1)Ã
Te(1)Ã
/
Cl(1)
Cl(2)
Te(1)
N(1)
C(1)
C(8)
2.3160(7)
2.3915(7)
2.4781(3)
2.086(2)
2.117(3)
2.144(3)
1.504(3)
1.496(4)
1.498(4)
1.497(4)
1.527(4)
1.535(4)
1.535(4)
/
/
/
/
/
/
/
C(1)
/
/
C(8)
/
N(1)Ã
N(1)Ã
N(1)Ã
C(8)Ã
C(10)Ã
C(11)Ã
C(12)Ã
/
C(9)
N(1)Ã
N(1)Ã
N(1)Ã
C(8)Ã
C(10)Ã
C(11)Ã
C(12)Ã
/
C(9)
/
C(10)
C(13)
/
C(10)
C(13)
/
/
/C(9)
/C(9)
/
C(11)
C(12)
C(13)
/
C(11)
C(12)
C(13)
/
/
/
/
Bond angles
1
2
Br(1)Ã
Br(2)Ã
Br(1)Ã
Br(2)Ã
Te(1)Ã
Br(1)Ã
Hg(1)Ã
Hg(1)Ã
C(1)ÃTe(1)Ã
Hg(1)ÃN(1)Ã
Hg(1)ÃN(1)Ã
Hg(1)ÃN(1)Ã
C(9)ÃN(1)Ã
C(9)ÃN(1)Ã
C(10)Ã
Te(1)ÃC(8)Ã
C(8)ÃC(9)ÃN(1)
/
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Te(1)Ã
Te(1)Ã
/
Te(1)
Te(1)
N(1)
N(1)
114.17(3) Cl(1)Ã
125.84(3) Cl(2)Ã
/
Pd(1)Ã
Pd(1)Ã
Pd(1)Ã
Pd(1)Ã
Te(1)ÃPd(1)Ã
Pd(1)ÃCl(2)
Pd(1)ÃTe(1)Ã
Pd(1)ÃTe(1)Ã
C(1)ÃTe(1)Ã
Pd(1)ÃN(1)Ã
Pd(1)ÃN(1)Ã
Pd(1)ÃN(1)Ã
C(9)ÃN(1)Ã
C(9)ÃN(1)Ã
C(10)Ã
Te(1)ÃC(8)Ã
C(8)ÃC(9)ÃN(1)
/
Te(1)
Te(1)
N(1)
N(1)
83.80(2)
166.41(2)
170.93(7)
93.61(7)
89.78(7)
94.12(2)
102.83(8)
91.01(8)
96.2(1)
/
/
/
/
/
/
98.1(1)
108.8(1)
85.4(1)
Cl(1)Ã
/
/
/
/
Cl(2)Ã
/
/
/
/
N(1)
/
/
N(1)
Fig. 1. ORTEP plot of the molecule 1. The atoms are drawn with 50%
probability ellipsoids.
/
/Br(2)
114.81(3) Cl(1)Ã
/
/
/
/
C(1)
C(8)
101.1(2)
88.6(2)
/
/
C(1)
/
/
/
/
C(8)
/
/
C(8)
93.8(2)
/
/
C(8)
/
/C(9)
105.9(3)
109.2(4)
112.8(3)
110.8(5)
114.5(5)
103.7(4)
116.0(4)
115.4(5)
/
/
C(9)
112.6(2)
112.3(2)
112.2(2)
110.5(2)
106.8(2)
101.9(2)
107.6(2)
113.7(2)
/
/C(10)
/
/
C(10)
C(13)
/
/C(13)
/
/
/
/C(10)
/
/
C(10)
/
/C(13)
/
/
C(13)
/
N(1)Ã
/
C(13)
/
N(1)Ã
/
C(13)
/
/
C(9)
/
/
C(9)
/
/
/
/
(CDCl3, 25 8C): d (vs Me4Si): 20.26 (C1), 23.11 (C4),
53.88 (C3), 59.43 (C2), 55.69 (OCH3), 107.00 (ArC-Te),
116.44 (ArC m to Te) 139.99 (ArC o to Te), 157.80 (ArC
p to Te).
2.5. Synthesis of [PdCl2(L1)] (2)
To a solution of L1 (0.16 g, 0.50 mmol) made in 10
cm3 of acetone was added Na2[PdCl4] (0.08 g, 0.27
mmol) dissolved in 10 cm3 of water. The resulting
mixture was stirred for 2 h at room temperature and
poured into 100 cm3 of water. The complex was
extracted into chloroform (100 cm3). The extract was
Fig. 2. ORTEP plot of the molecule 2. The atoms are drawn with 50%
probability ellipsoids.
dried over anhydrous Na2SO4, concentrated to ꢀ
cm3, and mixed with hexane (20 cm3). The resulting
redÁyellow compound was separated, filtered, washed
with hexane and dried in vacuo. The single crystals of
the complex were grown by keeping overnight its
solution made in MeCN and layered with hexane at
/
10
C13H19Cl2NOPdTe: C, 30.58; H, 3.72; N, 2.74; Te,
1
25.98%. NMR: H (CDCl3, 25 8C): d (vs Me4Si):, 1.60
/
(m, 4H, H4), 2.49Á
/
2.85 (m, 4H, H3), 3.37 (m, 1H, H1),
3.60 (m, 1H, H1), 3.84 (s, 3H, OCH3), 4.15 (m, 1H, H2),
4.21(m, 1H, H2), 7.05Á
/
7.08 (d, 2H, ArH m to Te), 8.09Á
/
8.12 (d, 2H, ArH o to Te); 13C {1H} (CDCl3, 25 8C): d
(vs Me4Si): 15.33 (C1), 21.85, 22.01 (C4), 55.43 (OCH3),
59.93, 60.50, 60.9, (C3), 65.00 (C2), 106.80 (ArC-Te),
0Á5 8C. Yield, 70%; m.p. 124 8C. Mol. wt.: Found, 953;
/
calc. 510.2. LM, 6.88 ohmꢀ1 cm2 molꢀ1. Anal. Found:
C, 30.41; H, 3.91; N, 2.57; Te, 25.08; Calc. for

24
G. Singh et al. / Journal of Organometallic Chemistry 688 (2003) 20Á26
/
The L1 is moderately stable and can be stored under
ambient conditions for ca. 1 month after which it
solidifies as it decomposes. L2 is much less stable than
L1 and has to be stored at 0Á
/
5 8C. Elemental tellurium
starts to precipitate when L2 is kept in organic solvents
for more than 3Á
4 h. The reactions of L1 and L2 with
/
HgBr2 and Na2PdCl4 result in complexes 1 to 3, as
shown in equation 2.
The conductance measurements on the ligands and
complexes indicate that they are all non-electrolytes. In
Fig. 3. ORTEP plot of the two molecules in the asymmetric unit of 3
The atoms are drawn with 50% probability ellipsoids.
the IR spectra of 1 and 3 n(HgÃ
217 cmꢀ1, respectively, while in that of 2, n(TeÃ
Cl) at 295
/
Br) appears at 213 and
/
C(alkyl)) appears at 449 cmꢀ1 and n(PdÃ
/
cmꢀ1. The molecular weight measurements suggest that
in solution no association occurs for 1, whereas for 2
and 3 the molecular weights are close to double the
expected formula weights, indicating some molecular
association. The 1H- and 13C{1H}-NMR spectra of both
the ligands are characteristic. On the formation of 1, the
1H-NMR spectrum shows deshielding of the order of
116.19 (ArC m to Te) 138.27 (ArC o to Te), 161.50 (ArC
p to Te).
2.6. Synthesis of [HgBr2(L2)] (3)
To a solution of HgBr2 (0.20g, 0.55 mmol) in acetone
(20 cm3) was added a freshly prepared solution of L2
(0.17g, 0.55 mmol) in CHCl3 (20 cm3). The resulting
mixture was stirred at r.t. until the ligand L2 was
consumed (as monitored by TLC). The solvent was
removed from the mixture on a rotary evaporator. The
resulting residue was dissolved in 20 cm3 of CHCl3 and
filtered through celite. The filtrate was concentrated to
10 cm3 and mixed with 20 cm3 of hexane. A colourless
complex was separated, filtered, dried in vacuo. and
0.20Á
0.25 ppm for the aromatic protons of L1 and H1
/
while, H2, H3, and H4 all show shielding as expected for
a d10 metal. In the 13C{1H}-NMR spectrum of 1, C1 is
deshielded by ca 11.5 ppm in comparison to that of
ligand L1. The signals corresponding to ArC o to Te, C2
and ArC-Te are also deshielded by ca 1.5, 2.0 and 5.0
ppm, respectively. These observations concur with the
ligation of L1 through Te and N. The 1H-NMR
spectrum of the palladium complex 2 is somewhat
complicated as signals of H1 and H2 protons give four
groups of signals, because of strong chelation. In
comparison to free L1, the H2 protons show deshielding
of ca 1.2 ppm. For H1, H3 and aromatic protons the
recrystallized from CHCl3Áhexane (1:1) mixture. Yield,
/
70%; m.p. 91Á92 8C; Mol. wt.: Found, 1310; calc. 683.6.
/
LM, 20.1 ohmꢀ1 cm2 molꢀ1. Anal. Found: C, 20.77; H,
3.21; N, 4.64, Te, 18.02; Calc. for C12H24Br2HgN2Te: C,
1
21.04; H, 3.50; N, 4.09; Te, 18.64%. NMR: H (CDCl3,
deshielding has been found to be ca 0.5Á0.8, 0.2 and 0.4
/
25 8C): d (vs Me4Si): 1.88Á1.89 (m, 4H, H4), 2.74 (bm,
/
to 0.5 ppm, respectively. Similarly in the 13C{1H}-NMR
spectrum of 2 the signals of C1, C2, C3 and ArC-Te have
4H, H3), 2.81 (bs, 2H, H1), 3.07 (bs, 2H, H2); 13C{1H}
(CDCl3, 25 8C): d (vs Me4Si): 16.83 (C1), 23.38 (C4),
53.38 (C2), 54.53 (C3).
been found to be deshielded (ca 5.6Á7.0 ppm) with
/
respect to those of free L1. Thus in 2, L1 is also
1
coordinated through both Te and N. In the H-NMR
spectrum of crystals of 3 H1, H2, H3 and H4 all appear
to be somewhat deshielded (0.17Á0.30) ppm. The signals
/
3. Results and discussion
of the pendent arm (Fig. 3) protons do not appear with
significant intensity. It is thus very likely that a fast
exchange on the NMR time scale occurs between
coordinated and pendent arm, which is supported by
the absence of separate signals for the pendent arm in
the 13C spectrum of 3. The C1 carbon signal of L2 on
The reactions given in equation 1 result in the
formation of the two ligands L1 and L2 which are oily
liquids highly soluble in chloroform and dichloro-
methane. L2 is also soluble in methanol but L1 only
moderately.

G. Singh et al. / Journal of Organometallic Chemistry 688 (2003) 20Á
/26
25
˚
formation of 3 shows deshielding of ca 16.7 ppm
whereas the C2 signal is shielded by 6.53 ppm on
complexation with Hg. The C3 and C4 signals on
the covalent radii of palladium and nitrogen.(ca 2.02 A)
suggesting relatively strong coordination, which is again
consistent with the conclusions reached from the NMR
˚
Te bond length of 2.4781(3) A is also
˚
consistent with the earlier report of 2.517 (1) A for
formation of 3 are deshielded by ꢀ
respectively. These observations indicate that HgÃ
/
0.7 and 1.52 ppm,
N
spectra. The PdÃ
/
/
bonding is not very strong, which is consistent with the
exchange of pendent and coordinated wings of L2. The
attempts to study the molecular associations of 2 and 3
and exchange of pendent arm with the coordinated one
in the case of 3 using variable temperature NMR did not
succeed as both the complexes have inadequate solubi-
lity below 0 8C for recording reasonable NMR.
[PdCl2(4-MeC6H4TeCH2CH2-2-(C5H4N))][9]. The
˚
Pd(1)Ã
/
Cl(1) bond (2.3160(7) A) is shorter than Pd(1)Ã
/
˚
Cl(2) (2.3915(7) A) as is to be expected for the trans
influence of Te but both are somewhat longer than the
˚
values of 2.287(3) and 2.352(3) A reported for another
Pd-complex of a (Te, N) ligand (4-MeC6H4TeCH2CH2-
2-(C5H4N)) [9]. The geometry around palladium is
distorted square planar with the cis Cl(1)Ã
angle 94.12(2)8 and the trans N(1)ÃPd(1)Ã
Te(1)ÃPd(1)ÃCl(2) angles 170.93(7) and 166.41(2)8,
respectively.
/
Pd(1)Ã
/
Cl(2)
3.1. The molecular structures of [HgBr2(L1)] (1) and
[PdCl2(L1)] (2)
/
/
Cl(1) and
/
/
HgBr2(L1)] (1) is the first example of a Hg-complex in
which a (Te, N) type hybrid organotellurium ligand acts
as a chelating ligand, in that the metal is also coordi-
nated via nitrogen as is demonstrated in Fig. 1. The
3.2. The molecular structure of [HgBr2(L2)] (3)
In the crystal of 3, there are two independent
molecules in the asymmetric unit that have molecular
structures that are essentially the same (Fig. 3).
Although the ligand L2 has three potential coordination
sites, coordination is via Te and only one nitrogen donor
atom. The second ring containing N forms a pendent
arm. The selected bond lengths and angles are given in
Table 3. As with 1 and 2, the bond angles at Te and the
selected bond lengths and angles are given in Table 2.
˚
Te bond length of 2.747(1) A is consistent with
The HgÃ
/
˚
the earlier report of 2.728(1) A for [HgBr(1-(NMe2)-2-
N bond
(TeC6H4-4-OEt)-4-MeC6H5)]2 [15]. The HgÃ
/
˚
length of 2.457(4) A is within the range of values
reported in literature [16,17] for complexes of Hg with
˚
various nitrogen donors [2.226(9)Á2.505(7) A]. In this
/
case it is longer than the sum of the covalent radii of
˚
mercury and nitrogen (ca 2.23 A) suggesting relatively
weak coordination which is consistent with the conclu-
Table 3
2
˚
Selected bond lengths (A) and angles (8) for HgBr2L (3)
sions reached from the NMR spectra. The HgÃ
/
Br bond
Bond lengths
˚
lengths of 2.578(1) and 2.537(1) A are only marginally
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Hg(1)Ã
Te(1)Ã
N(1)Ã
N(1)Ã
N(1)Ã
C(1)Ã
Te(1)Ã
/
Br(1)
Br(2)
Te(1)
N(1)
2.700(2)
2.505(2)
2.684(1)
2.48(1)
2.16(1)
1.48(2)
1.47(2)
1.48(2)
1.49(2)
2.14(1)
Hg(2)Ã
Hg(2)Ã
Hg(2)Ã
Hg(2)Ã
Te(2)Ã
N(3)Ã
N(3)Ã
N(3)Ã
C(13)Ã
Te(2)ÃC(19)
/
Br(3)
Br(4)
Te(2)
N(3)
2.685(2)
2.509(2)
2.688(1)
2.52(1)
2.15(1)
1.46(2)
1.49(2)
1.50(2)
1.53(2)
2.11(1)
˚
longer than the value of 2.500(1) A reported earlier for
the Hg-complex of a (Te, N) ligand coordinating only
through Te [15]. The bond angles around Hg are in the
/
/
/
/
/
/
/
C(1)
/
C(13)
range 85.4(1) to 125.84(3)8, with the Br(1)Ã
at 114.81(3)8. It seems unlikely that the difference in the
HgÃBr bond lengths arises from intermolecular associa-
/
Hg(1)Ã
/Br(2)
/
C(2)
C(3)
C(6)
/
C(14)
C(15)
C(18)
/
/
/
/
/
/
C(2)
/
C(14)
tion involving the bromine atoms because the two
/
C(7)
/
closest HgÁ Á ÁBr- contacts, Hg(1)Á Á ÁBr(1)- and
˚
Bond angles
Br(1)ÃHg(1)Ã
Br(2)ÃHg(1)Ã
Br(1)ÃHg(1)Ã
Br(2)ÃHg(1)Ã
N(1)ÃHg(1)Ã
Br(1)ÃHg(1)Ã
Hg(1)ÃTe(1)Ã
Hg(1)ÃTe(1)Ã
C(1)ÃTe(1)Ã
Hg(1)ÃN(1)Ã
Hg(1)ÃN(1)Ã
Hg(1)ÃN(1)Ã
C(2)ÃN(1)Ã
C(2)ÃN(1)Ã
C(3)ÃN(1)Ã
Te(1)ÃC(1)Ã
N(1)ÃC(2)ÃC(1)
Hg(1)Á Á ÁBr(2)- of 4.629(2) and 5.864(2) A are clearly
/
/
Te(1)
Te(1)
N(1)
N(1)
103.57(4) Br(3)Ã
143.85(5) Br(4)Ã
91.1(3) Br(3)Ã
109.3(3) Br(4)Ã
85.8(3) N(3)ÃHg(2)Ã
108.62(5) Br(3)ÃHg(2)Ã
90.1(3) Hg(2)ÃTe(2)Ã
95.4(4) Hg(2)ÃTe(2)Ã
94.5(5) C(13)ÃTe(2)Ã
105.4(7) Hg(2)ÃN(3)Ã
113.8(8) Hg(2)ÃN(3)Ã
114.8(8) Hg(2)ÃN(3)Ã
N(3)Ã
N(3)Ã
N(3)Ã
C(13)Ã
C(14)ÃC(13) 113(1)
/
Hg(2)Ã
Hg(2)Ã
Hg(2)Ã
Hg(2)Ã
/
Te(2)
Te(2)
N(3)
N(3)
106.83(4)
larger than the sum of the van der Waals radii of Hg and
˚
Br of ca 3.39 A. Thus the geometry around Hg can best
/
/
/
/
145.29(5)
92.3(2)
/
/
/
/
be described as distorted tetrahedral, with the coordina-
tion sphere being made up of Te, N and the two Br
atoms. The bond angles at Te and N are consistent with
/
/
/
/
108.3(2)
84.8(2)
/
/
Te(1)
/
/
Te(2)
/
/
Br(2)
/
/
Br(4)
104.61(6)
90.2(3)
/
/
C(1)
/
/
C(13)
their nearly trigonal pyramidal (88.6(2)Á
/
101.1(2)8) and
/
/
C(7)
/
/C(19)
98.1(4)
tetrahedral geometry (105.9(3)Á
/
112.8(3) 8), respectively.
/
/
C(7)
/
/
C(19)
92.0(5)
The molecular structure of [PdCl2(L1)] (2) also shows
(Fig. 2) the ligand L1 chelating through Te and N. The
selected bond lengths and angles are given in Table 2.
Again, the bond angles at Te and N are consistent with
/
/
C(2)
C(3)
C(6)
/
/
C(14)
C(15)
C(18)
104.1(7)
112.5(8)
113.2(8)
/
/
/
/
/
/
/
/
/
/
C(3)
C(6)
C(6)
113(1)
110(1)
101(1)
C(14)Ã
C(14)Ã
C(15)Ã
/
/
C(15) 114(1)
C(18) 109(1)
C(18) 104(1)
/
/
/
/
their nearly trigonal pyramidal (91.01(8)Á
and tetrahedral geometry (101.9(2)Á112.6(2) 8), respec-
tively. The PdÃN bond length of 2.086(2) A is consistent
with the literature reports [9]. This is close to the sum of
/
102.83(8) 8)
/
/
/
/
/
/
/
C(2)
114.8(9) Te(2)Ã
117(1)
/
/
C(14)
113.4(9)
˚
/
/
/
N(3)Ã
/
/

26
G. Singh et al. / Journal of Organometallic Chemistry 688 (2003) 20Á26
/
coordinating N atom are consistent with their nearly
trigonal pyramidal (91.1(3)Á98.1(4)8) and tetrahedral
geometry (104.1(7)Á114.8(8)8), respectively. In both 1
and 2, the TeÃC(alkyl) bond is somewhat longer than
the Teà Te bond length in
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(Fax: ꢁ44-1223-336033; e-mail: deposit@ccdc.cam.a-
c.uk or www: http://www.ccdc.cam.ac.uk).
/
/
/
/
/
C(aryl), as expected. The HgÃ
3 (ave 2.686(2) A) is some what shorter than that in 1 or
/
˚
Acknowledgements
[HgBr(1-(NMe2)-2-(TeC6H4-4-OEt)-4-MeC6H5)]2 [15].
˚
As in 1, the HgÃ
/
N bond length (ave 2.50(2) A) is longer
AKS and GS thank Council of Scientific and In-
dustrial Research (India) for financial support. M.B.H.
thanks the UK Engineering and Physical Sciences
Council for support of the X-ray facilities at South-
ampton. J.E.D. thanks the University of Windsor for
financial support. PS, on leave from Instituto de
Quimica, UNAM is thankful to DGAPA, UNAM for
financing sabbatical stay at IITD.
than the sum of the covalent radii of mercury and
nitrogen again consistent with the relatively weak
coordination suggested by the NMR spectra. The
geometry around Hg in 3 is more distorted from
tetrahedral than in 1 with the angles subtended at Hg
ranging from 84.8(2)8 for N(3)Ã
145.29(5)8 for Br(4)ÃHg(2)ÃTe(2); the latter value being
particularly high for tetrahedral geometry. The HgÃBr
/
Hg(2)Ã/Te(2) to
/
/
/
˚
2.700(2) A)
bond lengths cover a wider range (2.505(2)Á
/
than in 1, but bracket the average value in 1 of 2.56(3)
References
˚
˚
A. Given that two of the longer HgÃ
/
Br bonds at ca 2.70
A are close to the values found for bridging Br atoms in
related species such as [HgBr2L]2, where Lꢃ
[1] (a) A.K. Singh, V. Srivastava, J. Coord. Chem. 27 (1992) 237;
(b) A.K. Singh, S. Sharma, Coord. Chem. Rev. 209 (2000) 49.
[2] A.K. Singh, Proc. Indian Acad. Sci. (Chem. Sci.) 114 (2002) 357.
[3] (a) E.G. Hope, W. Levason, Coord. Chem. Rev. 12 (1993) 109;
(b) W. Levason, D. Orchard, G. Reid, Coord. Chem. Rev. 225
(2002) 159;
/
As(C6H5)2(C8H7O2) [18]. However as with 1, there is
no evidence of significant intermolecular HgÁ Á ÁBr bond-
ing because the shortest such distances are Hg(1)Á Á ÁBr(4)
4.541(3), Hg(1)Á Á ÁBr(3) 4.445(3), Hg(2)Á Á ÁBr(2) 4.236(3),
(c) J.A. Barton, A.R.J. Genge, N.J. Hill, W. Levason, S.D.
Orchard, B. Patel, G. Reid, A.J. Ward, Heteroatom Chem. 13
(2002) 550.
˚
Hg(2)Á Á ÁBr(1) 4.335 (3) A; values that are greater than
the sum of the van der Waals radii of Hg and Br of ca
˚
3.39 A but much shorter than found in 1. Thus all of the
[4] (a) J. Arnold, Prog. Inorg. Chem. 43 (1995) 353;
(b) P. Mathur, Adv. Organomet. Chem. 41 (1997) 243.
[5] A.K. Singh, J. Sooriyakumar, S. Husebye, K.W. Tornroos, J.
Organomet. Chem. 612 (2000) 46.
Br atoms have similar HgÁ Á ÁBr non-bonding distances,
whether or not they are forming shorter or longer HgÃ
/
Br bonds. Interestingly, but perhaps just coincidentally,
the inclusion of the two additional positions in a very
large coordination sphere results in a pseudo octahedral
arrangement around the Hg atoms, with for example the
[6] A.K. Singh, M. Kadarkaraisamy, G.S. Murthy, J. Srinivas, B.
Varghese, R.J. Butcher, J. Organomet. Chem. 605 (2000) 39.
[7] A.K. Singh, J. Sooriyakumar, M. Kadarkaraisamy, J.E. Drake,
M.B. Hursthouse, M.E. Light, R.J. Butcher, Polyhedron 21
(2002) 667.
trans angles Br(1)Ã
/
Hg(1)Á Á ÁBr(3), Te(1)ÃHg(1)Á Á ÁBr(2)
/
[8] A.K. Singh, J. Sooriyakumar, R.J. Butcher, Inorg. Chim. Acta
312 (2001) 163.
and N(1)Ã
/
Hg(1)Á Á ÁBr(4) being 153.48(7), 143.85(6), and
[9] A. Khalid, A.K. Singh, Polyhedron 16 (1997) 33.
[10] DENZO (Z. Otwinowski, W. Minor, Methods in Enzymology,
vol. 276: Macromolecular Crystallography, part A, C.W. Carter,
Jr., R.M. Sweet (Eds.) Academic Press, 1997, pp. 307.
[11] SORTAV (R.H. Blessing, Acta Crystallogr. A51 (1995) 33; R.H.
Blessing, J. Appl. Crystallogr. 30 (1997) 421.
174.9(4)1 respectively. The presence of the pendent arm
of the ligand L2 as a potentially tridentate ligand
coordinates in a bidentate mode may be a more
important factor in the packing although the
Hg(1)Á Á ÁN(2) and Hg(2)Á Á ÁN(4) distances are 4.45(2)
˚
[12] G.M. Sheldrick, Acta Crystallogr. A46 (1990) 467.
[13] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[14] SHELXL97 (G.M. Sheldrick, University of Gottingen, Gottingen,
and 4.44(2) A, respectively.
¨
¨
Germany).
[15] B.L. Khandelwal, A.K. Singh, V. Srivastava, D.C. Povey, G.W.
Smith, Polyhedron 9 (1990) 2041.
4. Supplementary material
[16] B. Korpar-Colig, Z. Popovic, D. Matkovic-Calogovic, D. Vikic-
Topic, Organometallics 12 (1993) 4708.
Crystallographic data for the structural analysis of
compounds 1, 2 and 3 have been deposited with the
Cambridge Crystallographic Data Centre, CCDC nos.
213574, 213575, and 213576. Copies of this information
may be obtained free of charge from The Director,
[17] D.C. Bebout, J.F. Bush, II, K.K. Crahan, M.E. Kastner, D.A.
Parrish, Inorg. Chem. 37 (1998) 4641.
[18] A.K. Singh, C.V. Amburose, T.S. Kraemer, J.P. Jasinski, J.
Organomet. Chem. 592 (1999) 25.