2-(4-Ethoxyphenlytelluromethyl)tetrahydro-2H-pyran (L1) and 2-(2-{4-ethoxyphenyl}telluroethyl)-1,3-dioxane (L2)

Article abstract of DOI:10.1016/S0020-1693(01)00491-1

2-(4-Ethoxyphenlytelluromethyl)tetrahydro-2H-pyran (L¹) and 2-(2-{4-ethoxyphenyl}telluroethyl)-1,3-dioxane (L²) have been synthesized by reacting in situ generated ArTe^-Na⁺ with an appropriate organic halide. The reaction of L¹ with iodine results in its diiodo derivative [L¹(I)₂] (1). The complexes of stoichiometries [CuBrL¹] (2), [HgBr₂L¹] (3) and [RuCl₂(p-cymene)·L¹/L²] (4/5) are synthesized. The NMR (¹H and ¹³C) in conjunction with elemental analyses, molecular weight and conductance measurements were used to characterize L¹, L², 1 and the complexes 2-5. The ligands coordinate in all the complexes through Te, as indicated by the deshielding of CH₂Te signals (up to ～ 0.8 ppm) with respect to those of free ligands, except in the case of 2 in which bonding through CH₂O has also to be invoked. Complexes 4 and 5 are characterized structurally (Ru-Te bond length: 2.619(8) and 2.642(1) A?, respectively). The Ru-Cl bond lengths are in the range 2.404(3)-2.420(6) A?. The Te-C(aryl) bond is shorter than the Te-C(alkyl) bond in 4 but similar in 5. The two Ru(II) complexes are the first examples with potential (Te, O) ligands of Ar(R)Te type, which have been structurally characterized.

Full text of DOI:10.1016/S0020-1693(01)00491-1

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Inorganica Chimica Acta 320 (2001) 133–140
2-(4-Ethoxyphenlytelluromethyl)tetrahydro-2H-pyran (L1) and
2-(2-{4-ethoxyphenyl}telluroethyl)-1,3-dioxane (L2): synthesis,
reactions of L1 with iodine and ligation of L1 with Ru(II), Cu(I),
and Hg(II) and L2 with Ru(II). Crystal structures of
[RuCl2(p-cymene)·L1/L2]
Ajai K. Singh a,*, M. Kadarkaraisamy a, M. Mishra a, J. Sooriyakumar a, J.E. Drake b,
M.B. Hursthouse c, M.E. Light c, Jerry P. Jasinski d
a Department of Chemistry, Indian Institute of Technology, New Delhi 110016, India
b Department of Chemistry and Biochemistry, Uni6ersity of Windsor, Windsor, Ont., Canada, N9B 3P4
c Department of Chemistry, Uni6ersity of Southampton, Southampton SO17 1BJ, UK
d Department of Chemistry, Keene State College, Keene, NH 03435-2001, USA
Received 21 February 2001; accepted 11 May 2001
Abstract
2-(4-Ethoxyphenlytelluromethyl)tetrahydro-2H-pyran (L1) and 2-(2-{4-ethoxyphenyl}telluroethyl)-1,3-dioxane (L2) have been
synthesized by reacting in situ generated ArTe−Na+ with an appropriate organic halide. The reaction of L1 with iodine results
in its diiodo derivative [L1(I)2] (1). The complexes of stoichiometries [CuBrL1] (2), [HgBr2L1] (3) and [RuCl2(p-cymene)·L1/L2]
(4/5) are synthesized. The NMR (1H and 13C) in conjunction with elemental analyses, molecular weight and conductance
measurements were used to characterize L1, L2, 1 and the complexes 2–5. The ligands coordinate in all the complexes through
Te, as indicated by the deshielding of CH2Te signals (up to ꢀ0.8 ppm) with respect to those of free ligands, except in the case
of 2 in which bonding through CH2O has also to be invoked. Complexes 4 and 5 are characterized structurally (RuꢀTe bond
,
,
length: 2.619(8) and 2.642(1) A, respectively). The RuꢀCl bond lengths are in the range 2.404(3)–2.420(6) A. The TeꢀC(aryl) bond
is shorter than the TeꢀC(alkyl) bond in 4 but similar in 5. The two Ru(II) complexes are the first examples with potential (Te,
O) ligands of Ar(R)Te type, which have been structurally characterized. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Ruthenium complexes; Copper complexes; Telluride complexes
1. Introduction
methyl)tetrahydro-2H-pyran, 2-(2-{4-methoxyphenyl}-
telluroethyl)-1,3-dioxane, 2-(phenyltelluromethyl) tetra-
hydrofuran and 2-(2-{4-methoxyphenyl}telluroethyl)-
1,3-dioxolane, and investigated their palladium(II) and
platinum(II) complexes but none of them gives crystals
suitable for X-ray diffraction. Moreover, the structural
authentication of these ligands could not be carried out,
as their crystals do not diffract. We, therefore, modified
the aryl group attached to Te (used 4-ethoxyphenyl in
place of Ph or 4-methoxyphenyl) and synthesized 2-(4-
ethoxyphenlytelluromethyl)tetrahydro-2H-pyran (L1)
The hemilabile (Px, Oy) type of ligands are found
interesting for designing catalytically active species [1]
as their oxygen donor atoms can protect the metal by
occupying its vacant coordination site until the sub-
strate reaches it. Similar tellurium ligands of (Tex, Oy)
type [2] are less known, in spite of some current interest
in hybrid organotellurium ligands. Recently, we have
designed [3] four such ligands: 2-(phenyltelluro-
* Corresponding author. Tel.: +91-11-659-1379; fax: +91-11-686-
2037.
E-mail address: aksingh@chemistry.iitd.ernet.in (A.K. Singh).
and
2-(2-{4-ethoxyphenyl}telluroethyl)-1,3-dioxane
(L2). Tellurium, being a ‘soft’ donor coordinates with
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00491-1

134
A.K. Singh et al. / Inorganica Chimica Acta 320 (2001) 133–140
other metallic species which are also ‘soft’ in character
like Pd(II), Pt(II), Cu(I), Hg(II), Ru(II) etc. Conse-
quently, to understand the ligation of L1 and L2 atten-
tion has been focussed on these metallic species. The
Pd(II) and Pt(II) complexes of both these ligands do not
give good single crystals, whereas crystals of Ru(II) com-
plexes, viz. [RuCl2(p-cymene)·L1/L2] are suitable for X-
ray diffraction. The crystal structures of the two
ruthenium complexes are reported in the present paper.
The ligation of (Te, O) donors is nearly unexplored,
therefore, Cu(I) and Hg(II) complexes of L1 are also
made the subject of the present paper. These results au-
thenticate for the first time the identity of the two (Te, O)
type ligands L1 and L2 structurally. The reaction of L1
with iodine is also used to further support the authenti-
cation of (Te, O) type ligands. The Ru(II) complexes are
also first examples of structurally characterized com-
plexes having potential (Te, O) ligands of Ar(R)Te type.
2. Experimental
The C and H analyses were carried out with a
Perkin–Elmer elemental analyser 240 C. Tellurium was
estimated volumetrically [4]. The 1H and 13C{1H}
NMR spectra were recorded on a Bruker Spectrospin
DPX-300 NMR spectrometer at 300.13 and 75.47
MHz, respectively. The conductance measurements
were made in acetonitrile (concentration ꢀ1 mM)
using an ORION conductivity meter model 162. The
molecular weights (concentration ꢀ5–10 mM) in chlo-
roform were determined with a Knauer vapour pressure
osmometer model A0280. The melting points deter-
mined in open capillary are reported as such. 2-(Bro-
momethyl)tetrahydro-2H-pyran
and
2-(2-bromo-
ethyl)-1,3-dioxane obtained from Aldrich (USA) were
used as received. The dimeric complex [Ru(p-
cymene)Cl2]2 was synthesized by the reported [5]
method.
2.1. X-ray diffraction analysis
The orange block crystal of [(p-cymene)RuCl2·L1]
(4), was mounted on a glass fibre. The data were
collected on an Enraf–Nonius Kappa CCD area detec-
tor (ƒ scans and ꢀ scans) to fill Ewald sphere at the
EPSRC National Crystallography Service, University
of Southampton, Southampton, UK. The q range for
data collection was 2.92–30.46°. The cell refinement [6]
was made by the reported method and an absorption
correction was applied [7] (transmission factors range
from 0.8781 to 0.7630). The structures were solved by
direct methods [8]. All the non-hydrogen atoms were
treated anisotropically. The OC5H9 group (pyran ring)
is disordered but readily modelled. The hydrogen
atoms, with the exception of those in the disordered
group, 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 parame-
ters for final cycle of full-matrix least-squares refinement
[9] are given in Table 1. The data for [(p-cymene)-
RuCl2·L2] (5) was collected on a Rigaku AFC6S diffrac-
tometer using monochromated Mo Ka radiation and
ꢀ–2q scan technique (2q=55.2°). Lorentz and polariza-
tion corrections were applied. A correction for sec-
ondary extinction was also applied. The structure of 5
was solved by heavy atom Patterson methods [10]
and expanded using Fourier techniques [11]. All calcula-
tions for 5 were performed using the TEXSAN [12] crystal-
lographic software package of Molecular Structure
Corporation except for refinement, which was per-
formed using SHELXL-97 [9]. The parameters for final
cycle of full-matrix least-squares refinement on F2 are
given in Table 1.
Table 1
Crystal data and structure refinement parameters for 4 and 5
4
5
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C
654.10
150
0.71073
monoclinic
C2/c
24H34O2TeRuCl2 C24H34O3TeRuCl2
670.07
296
0.71073
monoclinic
P21/n
,
Unit cell dimensions
,
a (A)
13.026(3)
14.431(3)
14.431(3)
25.862(9)
10.003(4)
21.270(6)
90
107.00(3)
90
5262(5)
8
1.722
,
b (A)
,
c (A)
h (°)
i (°)
99.82
k (°)
3
,
V (A )
Z
2627(1)
4
1.659
1304
0.15×0.10×0.07
29 993
6874
Dcalc (Mg m−3
F(000)
)
2688
0.30×0.15×0.60
6533
Crystal size (mm)
Reflections collected
Independent reflections
6388
[Rint=0.0558]
[Rint=0.071]
3345/0/299
R1=0.057,
wR2=0.237
Data/restraints/parameters 6874/0/329
Final R indices
R1=0.0482,
wR2=0.1016
([F2\2|(F2)] for 2;
[F2\3|(F2)] for 5)
Goodness-of-fit on F2
1.048
1.034
Largest difference peak
and hole (e A
0.750 and −0.956 1.37 and −0.89
−3
,
)

A.K. Singh et al. / Inorganica Chimica Acta 320 (2001) 133–140
135
2.2. Synthesis of 2-(4-ethoxyphenlytelluromethyl)-
tetrahydro-2H-pyran (L1)
(C3), 73.2 (C2), 112.2 (Ar-CꢀTe), 115.8 (Ar-C, m to
Te), 137.1 (Ar-C, o to Te), 161.1 (Ar-CꢀOEt).
Bis(4-ethoxyphenyl)ditelluride (1.00 g, 2 mmol) was
dissolved in ethanol (30 ml) and set to reflux under
dinitrogen atmosphere. A 5% solution of NaBH4 made
in 5% NaOH was added dropwise to this refluxing
solution until it became colourless, resulting in [ArTe−
Na+]. 2-(Bromomethyl)tetrahydro-2H-pyran (0.72 g, 4
mmol) was dissolved in ethanol (15 ml) and added to
the solution of [ArTe−Na+]. The mixture was refluxed
for 2–3 h, cooled to 25 °C and poured into 200 ml of
water. L1 was extracted into dichloromethane (100 ml).
The volume of the extract was reduced to 10 ml under
reduced pressure. Hexane (10 ml) was added to the
concentrate. The resulting off-white precipitate was
filtered, washed three to four times with hexane to
remove impurity of the precursor ditelluride and recrys-
tallized by layering its dichloromethane solution with
petroleum ether (40–60 °C). The recrystallized product
was dried in vacuo. Yield 70%; m.p. 78–80 °C. \M
(ohm−1 cm2 mol−1) 22.8. Anal. Found: C, 47.46; H,
5.83; Te, 36.11. Calc. for C14H20O2Te (MW 339, calc.
2.4. Synthesis of [CuBr(L1)]2 (2)
The cuprous bromide (0.28 g, 2 mmol) was dissolved
in 20 ml of nitromethane under oxygen-free nitrogen
atmosphere. A solution of L1 (0.99 g, 2 mmol) made in
10 ml of chloroform was added to it in one lot with
stirring. The mixture was stirred further for 1 h and
filtered through celite. The solvent from the filtrate was
evaporated off under reduced pressure on a rotary
evaporator. The residue was dissolved in 5–10 ml of
chloroform and mixed with 10 ml of petroleum ether
(40–60 °C). A yellow solid was obtained. It was
filtered, washed with hexane, recrystallized from chloro-
form–hexane (1:1) mixture and dried in vacuo. Yield
60%; m.p. 142–143 °C. \M (ohm−1 cm2 mol−1) 16.8.
Anal. Found: C, 32.05; H, 3.84; Te, 26.13. Calc. for
C14H20O2TeCuBr: C, 32.62; H, 3.93; Te, 25.97%. 1H
NMR (CDCl3, 25 °C): l (vs. TMS) 1.40–1.92 (m, 9H,
H4+H5+H6+CH3 of OEt), 3.57–3.67 (m, 1H, H1a),
3.69–3.88 (m, 1H, H1b), 4.05–4.15 (m, 5H, H3+H2+
OCH2 of OEt), 6.98–7.01 (d, 2H, Ar-H, m to Te),
7.99–8.02 (m, 2H, Ar-H, o to Te). 13C{1H} NMR
(CDCl3, 25 °C): l (vs. TMS) 14.6 (CH3), 22.8 (C5),
25.1 (C6), 32.1 (C4), 56.9 (C1), 63.8 (CH2 of OEt), 69.8
(C3), 72.5 (C2), 115.9 (Ar-C, m to Te), 134.6 (Ar-C, o
to Te), 173.3 (Ar-CꢀOEt).
1
MW 347.7): C, 48.35; H, 5.75; Te, 36.69%. H NMR
(CDCl3, 25 °C): l (vs. TMS) 1.40–1.94 (m, 9H, H4+
H5+H6+CH3 of OEt), 2.87–2.91 (m, 1H, H1a), 3.04–
3.08 (m, 1H, H1b), 3.48–3.58 (m, 2H, H3); 3.94–4.09
(m, 3H, H2+OCH2), 6.93–6.95 (d, 2H, Ar-H, m to
Te), 7.93–7.99 (m, 2H Ar-H, o to Te). 13C{1H} NMR
(CDCl3, 25 °C): l (vs. TMS) 14.6 (CH3), 16.3 (C1),
23.3 (C5), 25.1 (C6), 32.5 (C4), 63.5 (OCH2), 68.8 (C3),
73.7 (C2), 115.8 (Ar-C, m to Te), 133.9 (Ar-C, o to Te),
160.7 (Ar-CꢀOEt).
2.5. Synthesis of [HgBr(L1)]2 (3)
The solution of mercury(II) bromide (0.30 g, 0.85
mmol) made in 10 ml of acetone was mixed with L1
(0.34 g, 0.85 mmol) dissolved in 10 ml of chloroform.
The mixture was stirred for 1 h at r.t. The solvent was
completely removed on a rotary evaporator under re-
duced pressure. The residue was dissolved in 10 ml of
chloroform and mixed with 50 ml of hexane. The
resulting pale yellow precipitate was washed several
times with hexane, recrystallized from chloroform–hex-
ane mixture (1:1) and dried in vacuo. Yield 75%; m.p.
2.3. Reaction of L1 with iodine
The solution of ligand L1 (0.50 g, 1.04 mmol) made
in 10 ml of THF was added dropwise to iodine (0.52 g,
4.09 mmol) dissolved in 20 ml of THF with stirring at
room temperature (r.t.). The mixture was stirred further
for 1 h. The solvent was removed completely under
reduced pressure on a rotary evaporator. The residue
was dissolved in dichloromethane and layered with
petroleum ether (40–60 °C). The red fibrous crystals of
[L1(I)2] (1) were obtained after 24 h. They were sepa-
rated and dried in vacuo. Yield 80%; m.p. 125–126 °C.
89–90 °C(d).
\
M
(ohm−1 cm2 mol−1
) 17.9. Anal.
Found: C, 23.55; H, 2.70; Te, 18.35. Calc. for
C14H20O2TeHgBr2 (MW 1452.8, calc. MW 1416.7): C,
23.74; H, 2.82; Te, 18.02%. 1H NMR (CDCl3, 25 °C): l
(vs. TMS) 1.28–1.79 (m, 18H, H4+H5+H6+CH3 of
OEt), 3.28–3.35 (m, 1H, H1a), 3.40–3.44 (m, 1H, H1b),
3.57–3.68 (m, 2H, H3), 3.97–4.04 (m, 3H, H2+OCH2
of OEt), 6.98–7.01 (d, 2H, Ar-H, m to Te), 7.99–8.02
(m, 2H, Ar-H, o to Te). 13C{1H} NMR (CDCl3,
25 °C): l 14.5 (CH3), 22.8 (C5), 25.2 (C6), 32.0 (C4),
32.7 (C1), 63.5 (CH2 of OEt), 68.8 (C3), 73.7 (C2),
101.9 (Ar-CꢀTe), 116.6 (Ar-C, m to Te), 139.1 (Ar-C, o
to Te), 161.1 (Ar-CꢀOEt).
\
M (ohm−1 cm2 mol−1) 29.7. Anal. Found C, 25.95; H,
3.28; Te, 21.65. Calc. for C14H20O2TeI2: (MW 579.6,
calc. MW 601.4): C, 25.75; H, 3.32; Te, 21.21%. H
1
NMR (CDCl3, 25 °C) l (vs. TMS): 1.42–1.93 (m, 9H,
H4+H5+H6+CH3 of OEt), 3.49–3.57 (m, 1H, H1a),
3.86–3.91 (m, 1H, H1b), 3.96–4.05 (m, 5H, H3+H2+
OCH2 of OEt), 6.90–6.93 (d, 2H, Ar-H, m to Te),
7.92–7.94 (m, 2H Ar-H, o to Te).13C{1H} NMR
(CDCl3, 25 °C) l (vs. TMS): 14.7 (CH3), 22.8 (C5),
25.4 (C6), 32.4 (C4), 52.5 (C1), 63.8 (CH2 of OEt), 69.6

136
A.K. Singh et al. / Inorganica Chimica Acta 320 (2001) 133–140
1
2.6. Synthesis of [RuCl2(p-cymene)(L1)] (4)
MW 363.5): C, 46.20; H, 5.50; Te, 35.21%. H NMR
(CDCl3, 25 °C): l (vs. TMS) 1.18–1.20 (d, 1H, H5b),
1.37–1.42 (t, 3H, CH3 of OEt), 1.96–2.10 (m, 3H,
H2+H5a), 2.77–2.86 (t, 2H, H1), 3.69–3.73 (t, 2H,
H4b+H6b), 3.97–4.08 (m, 4H, H4a+H6a+CH2 of
OEt), 4.54–4.56 (t, 1H, H3), 6.71–6.74 (d, 2H, Ar-H, m
to Te), 7.64–7.67 (d, 2H, Ar-H, o to Te). 13C{1H}
NMR (CDCl3, 25 °C): l (vs. TMS) 1.0 (C1), 14.6 (CH3
of OEt), 26.0 (C5), 36.0 (C2), 63.5 (CH2 of OEt), 67.0
(C4, C6), 101.0 (Ar-CꢀTe), 102.5 (C3), 115.1 (Ar-C m
to Te), 140.8 (Ar-C o to Te).
[RuCl2(p-cymene)]2 (0.62 g, 1 mmol) dissolved in 10
ml of dichloromethane was mixed with a solution of L1
(0.69 g, 2 mmol) made in 20 ml of dichloromethane
with vigorous stirring. The mixture was stirred further
for 3 h. The solvent was removed on a rotary evapora-
tor under reduced pressure. The residue was dissolved
in diethylether (5 ml) and layered with 25 ml of
petroleum ether (40–60 °C). The dark-red microcrys-
talline solid was separated and dried in vacuo. The
orange coloured crystals of 4 were grown from a mix-
ture of dichloromethane and petroleum ether (40–
2.8. Synthesis of [RuCl2(p-cymene)·L2] (5)
60 °C) (8:2). Yield 75%; m.p. 153–154 °C.
\
M
(ohm−1 cm2 mol−1) 33.2. Anal. Found: C, 44.56; H,
5.25; Te, 19.56. Calc. for C24H34O2TeRuCl2 (MW
648.6, calc. MW 653.8): C, 44.08; H, 5.20; Te, 19.54%.
1H NMR (CDCl3, 25 °C): l (vs. TMS) 1.21–1.80 (m,
9H, H4+H5+H6+CH3 of OEt), 2.08–2.12 (d, 3H,
CH3), 3.03–3.09 (sp, 1H, CH of i-Pr), 3.41–3.51 (m,
1H, H1a), 3.59–3.88 (m, 1H, H1b), 4.05–4.08 (q, 2H,
OCH2 of OEt), 4.87–5.42 (m, 4H, Ar-H of p-cymene
ring), 6.86–6.88 (d, 2H, Ar-H, m to Te), 7.84–7.93 (d,
2H, Ar-H, o to Te). 13C{1H} NMR (CDCl3, 25 °C):
l (vs. TMS) 14.6 (CH3 of OEt), 18.5 (CH3 of i-Pr),
22.1–22.4 (CH3 of p-cymene), 23.1 (C5), 25.5 (C6), 27.1
(C1), 30.8 (CH of i-Pr), 32.3–32.5 (C4), 63.5 (CH2 of
OEt), 68.4 (C3), 73.8 (C2), 81.2, 81.3, 81.7, 81.8, 84.0,
85.2, 85.4 (Ar-C of p-cymene ring, o and m to i-Pr),
97.3–97.9 (Ar-C linked to i-Pr), 104.2 (Ar-CꢀTe), 115.8
(Ar-C, m to Te), 138.1 (Ar-C, o to Te), 160.5 (Ar-
CꢀOEt).
A solution of L2 (0.73 g, 2 mmol) made in 10 ml of
chloroform was added dropwise to [RuCl2(p-cymene)]2
(0.61 g, 1 mmol) dissolved in 20 ml of chloroform, with
vigorous stirring at r.t. and the mixture was stirred
further for 3 h. The solvent was evaporated off under
reduced pressure on a rotary evaporator. The residue
obtained was dissolved in 5 ml of dichloromethane and
mixed with 10 ml of petroleum ether (40–60 °C). A
red–orange solid was obtained, which was washed with
diethylether and dried in vacuo. The brick-red coloured
single crystals of 5 were grown from dichloromethane–
petroleum ether (40–60 °C) mixture (1:1) by keeping
its solution for 48 h at 0 °C. They were filtered and
dried in vacuo. Yield 85%; m.p. 128–129 °C. \M
(ohm−1 cm2 mol−1) 26.0. Anal. Found: C, 41.92; H,
5.38; Te, 19.27. Calc. for C24H34O3TeRuCl2 (MW
660.0, calc. MW 670.0) C, 42.98; H, 5.07; Te, 19.10%.
1H NMR (CDCl3, 25 °C): l (vs. TMS) 1.23–1.29 (m,
7H, H5b+CH3 of i-Pr), 1.41–1.46 (t, 3H, CH3 of OEt),
1.90–2.00 (m, 3H, H2+H5a), 2.05 (s, 3H, CH3 of
p-cymene), 2.79–2.83 (sp, 1H, CH of i-Pr), 2.91–3.00
(m, 1H, H1), 3.20–3.26 (m, 1H, H1), 3.57–3.67 (t, 2H,
H4b+H6b), 3.96–4.10 (m, 4H, H4a+H6a+CH2 of
OEt), 4.43–4.46 (t, 1H, H3), 4.94–4.96, 5.19–5.21,
5.29–5.31, 5.40–5.42 (4d, 4H, ArH of p-cymene),
6.88–6.91 (d, 2H, Ar-H, m to Te), 7.81–7.67 (d, 2H,
Ar-H, o to Te). 13C{1H} NMR (CDCl3, 25 °C): l (vs.
TMS) 12.5 (C1), 15.1 (CH3 of OEt), 18.8 (CH3 of Ar-H
of p-cymene), 22.3, 22.8 (CH3 of i-Pr), 26.0 (C5), 31.1
(CH i-Pr of p-cymene), 34.3 (C2), 63.5 (CH2 of OEt),
67.0 (C4, C6), 81.6, 82.3, 84.9, 85.8 (Ar-C of p-cymene),
102.5 (C3), 106.0 (Ar-CꢀTe), 116.1 (Ar-C, m to Te),
137.4 (Ar-C, o to Te).
2.7. Synthesis of 2-(2-{4-ethoxyphenyl}telluroethyl)-
1,3-dioxane (L2)
Bis(4-ethoxyphenyl)ditelluride (0.99 g, 2 mmol) was
refluxed in methanol (30 ml) under dinitrogen atmo-
sphere. Sodium borohydride (ꢀ0.2 g dissolved in 2 ml
of 1 M NaOH) was added dropwise to the refluxing
solution until it became colourless resulting in [ArTe−
Na+]. The solution was cooled to ꢀ35 °C and 2-(2-
bromoethyl)-1,3-dioxane (0.77 g, 4 mmol) dissolved in 5
ml of methanol was added dropwise with stirring. The
reaction mixture was further refluxed for 1 h, cooled to
25 °C and poured into ice-cold water (200 ml). The
ligand L2 was extracted into dichloromethane (100 ml).
The extract was washed with water, dried over sodium
sulfate and evaporated off under reduced pressure on a
rotary evaporator, resulting in yellowish oil. The oil
was dissolved in acetone–hexane (1:2) mixture and the
solution was kept at 0–5 °C for 3 days. The ligand L2
was filtered as an off-white crystalline solid and dried in
3. Results and discussion
Ligands L1 and L2 and their complexes have been
synthesized by the reactions given in the Eqs. (1)–(4).
They are authenticated by their elemental analyses. The
molar conductance (\M) of all the compounds deter-
mined in acetonitrile at ꢀ1 mM concentration level
vacuo.
Yield
73%;
m.p.
57–58 °C.
\
M
(ohm−1 cm2 mol−1) 8.8. Anal. Found: C, 45.45; H,
5.43; Te, 34.91. Calc. for C14H20O3Te (MW 354.4, calc.

A.K. Singh et al. / Inorganica Chimica Acta 320 (2001) 133–140
137
Fig. 1. HETCOR spectrum of L1.
has been found to be much lower than the value
expected for a 1:1 electrolyte. Therefore, they all may
be considered as non-ionic. The molecular weights of
the ligands and complexes determined in chloroform at
ꢀ5–10 mM concentration level have also been found
to be very close to those calculated from their molecu-
lar formulae.
based on the consideration of relative intensities of
signals and other literature reports [3]. The H1 protons
are not magnetically equivalent. The H1a, H1b and H2
protons constitute AA%B type spin system [13]. Thus,
H1a and H1b protons appear as two multiplets of equal
intensity in the regions 2.87–2.91 and 3.04–3.08 ppm,
respectively. The magnetic non-equivalence of H1a and
H1b protons is supported by the HETCOR spectrum of
L1, in which both H1a and H1b appear as multiplets but
they have only one 13C{1H} cross-peak (Fig. 1). The
diiodo derivative [L1(I)2] (1) is formed through oxida-
tive addition of iodine to tellurium of L1. The 1H NMR
spectrum of 1 is characteristic. The H1a and H1b signals
are found deshielded (ꢀ0.6–0.8 ppm) with respect to
those of free L1. This concurs with the +IV oxidation
[ArTe−Na+]+2-(bromomethyl)tetrahydro-
2H-pyran/2-(2-bromomethyl)-1,3-dioxane“2 L1/L2
N
(1)
Cu2Br2+2L1“[CuBrL1]2
[RuCl2(p-cymene)]2+2L1/L2
“2[RuCl2(p-cymene)·L1/L2]
HgBr2+L1“1/2[HgBr2L1]2
(2)
(3)
(4)
1
state of tellurium in 1. In the H NMR spectrum of 2,
both CH2ꢀTe and CH2ꢀO signals are found deshielded
by 0.65–0.81 and 0.5 ppm, respectively with respect to
those of the free ligand L1, suggesting that both tel-
lurium and oxygen are involved in the coordination
with copper. However in the 1H NMR spectrum of
complex 3 only CH2ꢀTe signals are found deshielded
(0.3–0.4 ppm with respect to those of free L1). The
3.1. NMR spectra
1
In the H NMR spectrum of L1, the H4, H5 and H6
protons merge together and appear as a multiplet in the
region of 1.24–1.96 ppm. The other assignments are

138
A.K. Singh et al. / Inorganica Chimica Acta 320 (2001) 133–140
CH2ꢀO signal remains unaffected. This implies that in 3
coordination of L1 with Hg is not through the CH2O-
group. However, the change in the chemical shift of
ArH ortho to Te is not significant for any of the three
CH2ꢀO signal remains unaffected in the case of 3 and 4
but exhibits a deshielding of ꢀ2–3 ppm in the case of
2. This concurs with the 1H NMR data and implies that
L1 coordinates as a (Te, O) ligand with Cu(I) only.
Complexes 2 and 3 do not give crystals suitable for
X-ray diffraction but on the basis of NMR data the
following structures seem to be the most plausible for
them (TeꢀOꢁL1).
1
complexes 2–4. Both CH2Te signals in the H NMR
spectrum of 4 also appear deshielded (ꢀ0.5 ppm) in
comparison to those of free L1 and CH2O signal also
remains unaffected, indicating that in 4 also L1 coordi-
1
nates with Ru through Te only. Similarly, in the H
NMR spectrum of 5 two CH2Te signals of equal inten-
sity, each corresponding to one proton, were observed
and both were found deshielded (ꢀ0.2– ꢀ0.5 ppm)
with respect to those of free ligand L2. The signals of
aryl protons ortho to Te are also shifted downfield
(ꢀ0.2 ppm) with respect to those of L2. The signals
due to ꢀCH2O-protons of the dioxane ring are found
insignificantly shifted in the spectrum of 5, when com-
pared to those of corresponding free L2. On the basis of
1
these H NMR observations it is reasonable to con-
clude that L1 and L2 coordinate through Te only,
except in the case of Cu(I)-complex, where bonding
through oxygen has also to be invoked.
In the 13C{1H} NMR spectrum of both the com-
plexes 4 and 5, Ar-C signals originating from p-cymene
ring appear in the range 81.2–85.8 ppm as reported
earlier [14]. In the spectrum of 5, CH2Te (C1) and
Ar-CꢀTe signals undergo a downfield shift of ꢀ11 and
ꢀ4 ppm, respectively in comparison to those of free
ligand and signal of CH2O (C2) is not affected signifi-
cantly, implying that only Te is involved in bonding as
inferred in the case of 4.
13C{1H} NMR spectra of L1, L2 and [L1(I)2] (1) are
characteristic. The DEPT-135 NMR spectrum of L2
was used to distinguish between CH3, CH2 and CH
group signals. The Ar-CꢀTe signal was not observed in
the spectrum of L1 and therefore it is of no diagnostic
use for 1 and complexes 2–4. The signal of CH2ꢀTe in
the 13C spectrum of 1 appears ꢀ36 ppm downfield
with respect to that of L1, concurring with the +IV
oxidation state of tellurium in the diiodo derivative. In
the spectra of complexes 2–4, CH2ꢀTe signal is found
deshielded (ꢀ7–47) with respect to that of free L1. The
3.2. Crystal structures of 4 and 5
The molecular structure of 4 is shown in Fig. 2 and
the selected bond lengths and bond angles are given in
Table 2. Complex 4 is a half-sandwich compound in
which the coordination sphere of the metal is composed
of two chloride ligands, h6-bonded p-cymene ring and
ligand L1 coordinated through Te. Its RuꢀTe bond
,
length (2.6197(8) A) is consistent with the literature
,
value 2.619(4)–2.650(1) A reported for [Ru{PhTe-
(CH2)3TePh}2Cl2] and [Ru{MeTe(CH2)3TeMe}2Cl
PPh3]PF6 [15a]. The average value for RuꢀC bond
,
length is 2.189 A and concurs with our earlier report
[15b]. Ruthenium atom does not appear to be placed at
the centre of the p-cymene ring, but is slightly shifted
towards C(6). The average aromatic CꢀC bond lengths
and CꢀCꢀC angles are found to be normal. The pyran
ring has chair conformation as expected. The RuꢀCl
,
bond distances 2.4205(12) and 2.4136(12) A are normal
,
and consistent with the litera-ture values 2.4173(8) A
[16], reported for [RuCl{h2-C,NꢀC6H3(CH2NMe2)2-
2,6}{h6-C10H14}]. The aromatic ring of p-cymene lig-
and is almost planar (CꢀCꢀC bond angles vary from
116.8(3) to 122.3(4)°) and perpendicular to Ru. The
Te(1)ꢀC(17) bond length is shorter than that for
Te(1)ꢀC(11), as in the former one carbon is aromatic.
Fig. 2. Molecular structure of 4. The atoms are drawn with 50%
probability ellipsoids. One of the disordered OC5H9 groups and
hydrogen atoms are omitted for clarity.

A.K. Singh et al. / Inorganica Chimica Acta 320 (2001) 133–140
139
Table 2
Selected bond lengths (A) and bond angles (°) for 4
Table 3
,
,
Selected bond lengths (A) and bond angles (°) for 5
,
,
Bond lengths (A)
Bond lengths (A)
TeꢀRu
Te(1)ꢀRu(1)
Ru(1)ꢀCl(1)
Te(1)ꢀC(11)
O(2)ꢀC(20)
Ru(1)ꢀC(1)
Ru(1)ꢀC(2)
Ru(1)ꢀC(4)
O(1A)ꢀC(12A)
O(1A)ꢀC(16A)
Te(1)···O(1A)
2.6197(8) Ru(1)ꢀCl(2)
2.4205(12) Te(1)ꢀC(17)
2.157(4) O(2)ꢀC(23)
1.377(5) Te(1)···O(2)
2.196(4) Ru(1)ꢀC(6)
2.185(4) Ru(1)ꢀC(3)
2.208(4) Ru(1)ꢀC(5)
O(1B)ꢀC(12B)
1.464(17) O(1B)ꢀC(16B)
3.281(4) Te(1)···O(1B)
2.4136(12)
2.105(4)
1.397(6)
6.255(4)
2.168(4)
2.210(4)
2.170(4)
1.366(19)
1.49(2)
2.642(1)
2.13(2)
2.415(3)
2.19(1)
2.20(1)
2.17(1)
1.43(2)
TeꢀC(11)
RuꢀCl(1)
RuꢀC(1)
RuꢀC(3)
RuꢀC(5)
O(2)ꢀC(13)
O(3A)ꢀC(20)
2.13(1)
2.404(3)
2.20(1)
2.199(9)
2.19(2)
1.40(2)
1.48(3)
TeꢀC(17)
RuꢀCl(2)
RuꢀC(2)
RuꢀC(4)
RuꢀC(6)
O(2)ꢀC(16)
1.43(2)
Bond angles (°)
RuꢀTeꢀC(11)
RuꢀTeꢀC(17)
TeꢀRuꢀCl(1)
104.4(2)
106.5(8)
88.88(6)
80.44(6)
89.1(1)
91.3(3)
110(1)
C(1)ꢀRuꢀC(3)
C(1)ꢀRuꢀC(5)
C(2)ꢀRuꢀC(3)
C(2)ꢀRuꢀC(5)
C(4)ꢀRuꢀC(3)
C(6)ꢀRuꢀC(3)
C(13)ꢀO(2)ꢀC(16)
67.9(3)
67.9(4)
37.2(4)
79.8(4)
38.6(4)
80.3(4)
112(1)
3.185(4)
Bond angles (°)
Cl(1)ꢀRu(1)ꢀTe(1)
Cl(1)ꢀRu(1)ꢀCl(2)
C(11)ꢀTe(1)ꢀRu(1)
C(12A)ꢀO(1A)ꢀC(16A) 109.8(10) C(12B)ꢀO(1B)
ꢀC(16B)
79.85(3) Cl(2)ꢀRu(1)ꢀTe(1)
89.38(5) C(11)ꢀTe(1)ꢀC(17)
101.43(12) C(17)ꢀTe(1)ꢀRu(1)
78.80(4)
97.51(17)
104.78(11)
113.4(12)
TeꢀRuꢀCl(2)
Cl(1)ꢀRuꢀCl(2)
Cl(2)ꢀRuꢀC(1)
C(13)ꢀOꢀC(14)
O(1)ꢀC(12)ꢀC(2)
58.5(2)
C(12A)ꢀC(11)ꢀTe(1)
110.2(10) O(1B)ꢀC(12B)
ꢀC(13B)
111.7(12)
O(1A)ꢀC(12A)ꢀC(13A) 112.2(18) O(1B)ꢀC(12B)ꢀC(11) 108.7(13)
O(1A)ꢀC(12A)ꢀC(11) 106.3(10) O(1B)ꢀC(16B)
ꢀC(15B)
,
and 2.13(2) A, respectively, surprisingly equal. The
107.8(16)
,
RuꢀCl bond distances of 5 (2.404(3) and 2.415(3) A)
are normal and also consistent with the literature values
mentioned above. The aromatic ring of p-cymene lig-
and in 5 is almost planar as the CꢀCꢀC bond angles
vary from 118.5(9) to 121.9(9)°. The carbon and oxygen
atoms of OEt group have disorder. Thus, there are
pairs O3A, O3B and C23A, C23B. Therefore, C23A
and C23B, as well as C24, do not have any hydrogen
attached to them.
O(1A)ꢀC(16A)ꢀC(15A) 111.6(13)
4. Conclusions
The potential (Te, O) ligands, 2-(4-ethoxyphenlytel-
luromethyl)tetrahydro-2H-pyran (L1) and 2-(2-{4-
ethoxyphenyl}telluroethyl)-1,3-dioxane(L2), which like
(P, O) ligands may exhibit hemi-lability and thus can be
of some importance in the context of catalytically active
species, have been authenticated structurally in
[RuCl2(p-cymene)·L1/L2] (4/5). The coordination of L1
through Te alone as well as a (Te, O) ligand has been
demonstrated. Ligand L2 coordinates with Ru through
Te only. The RuꢀTe bond lengths are 2.619(8) and
Fig. 3. Molecular structure of 5. The atoms are drawn with 50%
probability ellipsoids.
,
2.642(1) A in 4 and 5, respectively. Complexes 4 and 5
are the first examples of complexes with potential (Te,
O) ligands of Ar(R)Te type, which have been struc-
turally characterized.
Ru complex 5 is also a half-sandwich compounds
and its molecular structures is shown in Fig. 3. The
selected bond lengths and bond angles of 5 are given in
Table 3. The metal’s coordination sphere has a compo-
sition similar to that of 4. The RuꢀTe bond length is
5. Supplementary material
,
2.642(1) A and consistent with that of 4 and the
literature reports mentioned above. The average aro-
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 149842 and 149843 for com-
plexes 4 and 5, respectively. Copies of this information
may be obtained free of charge from The Director,
matic CꢀC bond lengths and CꢀCꢀC angles of 5 are
,
1.37(2) A and 120.0(0)°, respectively, and normal. The
dioxane ring has a chair conformation as expected. In 5
TeꢀC(alkyl) and TeꢀC(aryl) bond lengths are 2.13(1)

140
A.K. Singh et al. / Inorganica Chimica Acta 320 (2001) 133–140
[6] Z. Otwinowski, W. Minor, Denzo, in: C.W. Carter Jr., R.M.
Sweet (Eds.), Macromolecular Crystallography, Part A. In:
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1997 (307pp.).
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
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(
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[10] P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, S.
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Acknowledgements
A.K.S., M.M., M.K. and J.S. thank the Department
of Science and Technology (India) for financial sup-
port. J.E.D wishes to thank the Natural Sciences and
Engineering Research Council (Canada).
[11] P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, R.
de Gelder, R. Israel, J.M.M. Smits, The DIRDIF program system,
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[12] TEXSAN for Windows: Crystal Structure Analysis Package,
Molecular Structure Corporation, 1997.
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