2-[2-(4-Methoxyphenyltelluro)ethyl]thiophene (L1) bis[2-(2-thienyl)ethyl] telluride (L2) and their metal complexes; crystal structure of trans-dichlorobis{2-(2- (4-methoxyphenyltelluro)ethyl)thiophene-Te}palladium(II) and {bis[2-(2-thienyl)ethyl] telluride}dichloro(p-cymene)ruthenium(II)

Article abstract of DOI:10.1016/j.jorganchem.2004.04.023

The reaction of ArTe^- (Ar=4-MeOC₆H₄) and Te^2- generated in situ by borohydride reduction of Ar₂Te₂ and Te, respectively, with 2-(2-thienyl) ethyl chloride has resulted in 2-[2-(4-methoxyphenyltelluro) ethyl]thiophene (L¹) and bis[2-(2-thienyl)ethyl] telluride (L²), respectively. Their complexes [AgNO₃ (L¹)] (1) [PdCl₂(L¹)₂] (2) [PtCl₂(L¹)₂] (3) [HgBr₂ (L¹)]₂ (4) [Ru(p-cymene)Cl₂ (L¹)] (5) [Ru(p-cymene)Cl₂(L²)] (6) and [PdCl₂(L²)₂] have been synthesized. The ligands and complexes exhibit characteristic ¹H and ¹³C{¹H} NMR spectra. Both the ligands coordinate only through Te in all the complexes. The single crystals of 2 and 6 are characterized by X-ray diffraction. Compound 2 has square planar geometry around Pd and trans arrangement of ligands. The Pd-Te bond distances 2.5951(7) and 2.5872(7) ? are longer than the values expected due to strong trans influence. The unique intermolecular secondary Te?Cl interaction (distance=3.450/3.449 ?) between neighbouring molecules has been observed in the crystal structure of 2. The distance between Pd atoms of two neighbouring molecules 3.2143(10) ? has also been found less than the sum of van der Waal's radii 3.26 ?. These secondary interactions in 2 result in the formation of a dimeric species, which remains intact even in the solution. Compound 6 is a half sandwich having three coordination sites occupied by two Cl atoms and the Te atom of L² with Ru-Te bond distance of 2.6528(9) ? and Ru-Cl, 2.415(2)/2.422(2) ?.

Full text of DOI:10.1016/j.jorganchem.2004.04.023

Journal of Organometallic Chemistry 689 (2004) 2346–2353
www.elsevier.com/locate/jorganchem
2-[2-(4-Methoxyphenyltelluro)ethyl]thiophene (L1)
bis[2-(2-thienyl)ethyl] telluride (L2) and their metal complexes; crystal
structure of trans-dichlorobis{2-(2-(4-methoxyphenyltelluro)ethyl)
thiophene-Te}palladium(II) and {bis[2-(2-thienyl)ethyl] telluride}
dichloro(p-cymene)ruthenium(II)
a
a,
a
b
c
Sumit Bali , Ajai K. Singh *, Pankaj Sharma , R.A. Toscano , J.E. Drake ,
d
M.B. Hursthouse , M.E. Light
d
a
Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India
b
Instituto de Quimica, UNAM, Circuito Exterior, Coyoacan, 04510 DF, Mexico
c
Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ont., Canada N9B 3P4
d
Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK
Received 5 March 2004; accepted 15 April 2004
Abstract
The reaction of ArTeꢀ (Ar ¼ 4-MeOC6H4) and Te2ꢀ generated in situ by borohydride reduction of Ar2Te2 and Te, respectively,
with 2-(2-thienyl)ethyl chloride has resulted in 2-[2-(4-methoxyphenyltelluro)ethyl]thiophene (L1) and bis[2-(2-thienyl)ethyl] telluride
(L2), respectively. Their complexes [AgNO3(L1)] (1) [PdCl2(L1)2] (2) [PtCl2(L1)2] (3) [HgBr2(L1)]2 (4) [Ru(p-cymene)Cl2(L1)] (5)
[Ru(p-cymene)Cl2(L2)] (6) and [PdCl2(L2)2] have been synthesized. The ligands and complexes exhibit characteristic 1H and
13C{1H} NMR spectra. Both the ligands coordinate only through Te in all the complexes. The single crystals of 2 and 6 are
characterized by X-ray diffraction. Compound 2 has square planar geometry around Pd and trans arrangement of ligands. The Pd–
ꢀ
Te bond distances 2.5951(7) and 2.5872(7) A are longer than the values expected due to strong trans influence. The unique inter-
ꢀ
molecular secondary Teꢁ ꢁ ꢁCl interaction (distance ¼ 3.450/3.449 A) between neighbouring molecules has been observed in the crystal
ꢀ
structure of 2. The distance between Pd atoms of two neighbouring molecules 3.2143(10) A has also been found less than the sum of
ꢀ
van der Waal’s radii 3.26 A. These secondary interactions in 2 result in the formation of a dimeric species, which remains intact even
in the solution. Compound 6 is a half sandwich having three coordination sites occupied by two Cl atoms and the Te atom of L2
ꢀ
ꢀ
with Ru–Te bond distance of 2.6528(9) A and Ru–Cl, 2.415(2)/2.422(2) A.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: 2-[2-(4-Methoxyphenyltelluro)ethyl]thiophene; Bis[2-(2-thienyl)ethyl] telluride; Organotellurium ligands; Metal complexes; Synthesis;
Crystal structure
1. Introduction
telluroether ligands compared to thioethers [1–4], the
availability of standardized routes for synthesis of such
ligands, the possibility of using metal complexes of Te-
ligands as precursor for II–VI semiconductors, and the
improved availability of FT NMR for studying behav-
iour in solution. Hybrid organotellurium ligands have
also received attention in the last decade [2]. They are
organotellurium compounds of RR0Te type, where R or
R0 has a coordinating group. The R and R0 groups ex-
plored are alkyl, aryl and heterocyclic groups derived
The interest in tellurium ligands [1–6] has grown in
the last decade. The important reasons for it are the
increasing evidence of enhanced ligating properties of
* Corresponding author. Tel.: +91-11-1265-91379; fax: +91-11-
2686207.
E-mail addresses: aksingh@chemistry.iitd.ac.in, ajai57@hot-
mail.com (A.K. Singh).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.04.023

S. Bali et al. / Journal of Organometallic Chemistry 689 (2004) 2346–2353
2347
from pyridine [7] and pyrrolidine [8a]. However com-
plexes of such tellurides having thienyl group have not
been investigated so far, except one report on cis-
[PdCl2{(C4H3S)T eCH3}2] [8b]. It was therefore thought
worthwhile to design 2-[2-(4-methoxyphenyltelluro)eth-
yl]thiophene (L1) and bis[2-(2-thienyl)ethyl] telluride
(L2) by reacting ArTeꢀ and Te2) with 2-(2-thienyl)ethyl
chloride respectively. Their complexation with Ag(I),
Hg(II), Pd(II), Pt(II) and Ru(II) has been studied.
tellurium only. The results of these investigations are
reported in the present paper.
2. Experimental
The C and H analyses were carried out with a Perkin
Elmer elemental analyzer 240 C. Tellurium was esti-
1
mated by atomic absorption spectrometer. 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 4000–
OMe
5
4
1
3
250 cmꢀ1 were recorded on a Nicolet Protege 460 FT-IR
6
ꢁ
Te
S
2
spectrometer as KBr and CsI pellets. The conductance
measurements were made in acetonitrile (concentration
ꢂ1 mM) using an ORION conductivity meter model
162. The molecular weights (concentration ꢂ5 mM) in
chloroform were determined with a Knauer vapour
pressure osmometer model A0280. The melting points
determined in open capillary are reported as such.
L1
5
4
1
3
6
S
S
Te
L2
2
2.1. X-ray diffraction analysis
The complexes, trans-dichlorobis{2-(2-(4-methoxy-
phenyltelluro)ethyl)thiophene-Te}palladium(II) (2) and
{bis[2-(2-thienyl)ethyl] telluride}dichloro(p-cymene)ru-
thenium(II) (6) have been characterized by X-ray dif-
fraction studies on its single crystals. In both the
complexes the ligands L1 and L2 coordinate through
X-ray diffraction data for 2 and 6 were collected on a
Bruker Smart APEX CCD diffractometer and Enraf
Nonius Kappa CCD area detector diffractometer with /
and x scans chosen to give a complete asymmetric unit,
using a graphite monochromatized Mo-Ka radiation
Table 1
Crystal data and structure refinement of trans-dichloro-bis{2-(2-(4-methoxyphenyl-telluro)ethyl)thiophene-Te}palladium(II)(2) and {bis[2-(2-thie-
nyl)ethyl] telluride}dichloro (p-cymene)ruthenium(II) (6)
Compound
2
6
Empirical formula
Formula weight
Temperature
C26H28Cl2O2Pd S2Te2
869.10
293(2) K
C22H28S2Cl2RuTe
656.13
120(2)
Crystal system
Space group
Unit cell dimensions
Monoclinic
C2=c
Monoclinic
Cc
ꢀ
ꢀ
a ¼ 28:262ð1Þ A
a ¼ 5:9522ð3Þ A
ꢀ
ꢀ
b ¼ 7:7048ð3Þ A
b ¼ 35:531ð3Þ A
ꢀ
ꢀ
c ¼ 27:770ð1Þ A
c ¼ 11:516ð1Þ A
a ¼ 90°
a ¼ 90°
b ¼ 97:857ð1Þ°
b ¼ 101:948ð5Þ°
c ¼ 90°
c ¼ 90
3
ꢀ
Volume (A )
5990.3(4)
8
1.927
2382.7(3)
4
1.829
Z
Density (calculated) (Mg/m3)
F ð000Þ
3328
0.250 ꢃ 0.104 ꢃ 0.030 mm/red/parallel-piped
1288
0.10 ꢃ 0.07 ꢃ 0.02/red/slab
3.55 to 27.47
Crystal size/colour/shape
h range for data collection (°)
Index ranges
)1.93 to 25.04
)33 6 h 6 33, ꢀ9 6 k 6 9, ꢀ33 6 l 6 33
23811
ꢀ7 6 h 6 7, ꢀ42 6 k 6 46, ꢀ14 6 l 6 14
11515
Reflections collected
Independent reflections
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices
5300 [R
¼ 0:0585]
4972 [Rint ¼ 0:0809]
0.9561 and 0.8052
4972/47/244
ðintÞ
0.9440 and 0.6932
5300/0/318
1.004
0.962
R1 ¼ 0:0413, wR2 ¼ 0:0750 [F 2 > 2rðF 2Þ]
R1 ¼ 0:0645, wR2 ¼ 0:0792
0.980 and )0.870
R1 ¼ 0:0499, wR2 ¼ 0:0812 [F 2 > 4rðF 2Þ]
R1 ¼ 0:0945, wR2 ¼ 0:0936
1.334 and )1.115
R indices (all data)
Largest difference peak and hole (e A
ꢀ3
ꢀ
)

2348
S. Bali et al. / Journal of Organometallic Chemistry 689 (2004) 2346–2353
ꢀ
(k ¼ 0:71073 A) at 293(2) and 120(2) K, respectively. An
analytical face indexed absorption correction was ap-
plied in case of 2. SMART software (data collection and
data reduction) and SHELXTL were used for solution
and refinement of its structure [9]. Table 1 summarizes
the crystal data along with other experimental parame-
ters for 2 and Fig. 1 depicts the its ORTEP diagram. Cell
refinement [10] of 6 gave cell constants corresponding to
a monoclinic cell whose dimensions are also given in
Table 1 along with other experimental parameters. The
molecule is displayed in the ORTEP diagram in Fig. 2.
An absorption correction was applied in this case also
[10]. The structure was solved by direct methods [11] and
was refined using the WinGX version [12] of SHELX-97
[13]. All of the non-hydrogen atoms were treated an-
isotropically. Hydrogen atoms were included in ideal-
ized positions with isotropic thermal parameters set at
1.2 times that of the carbon atom to which they were
in the first. The selected bond lengths and angles of 2
and 6 are given in Tables 2 and 3, respectively. Addi-
tional material for both the structures available from the
Cambridge Crystallographic Data Center [CCDC Nos.
235562 and 235563 for palladium (2) and ruthenium (6)
complexes] comprises the final atomic coordinates and
thermal parameters for all atoms and a complete listing
of bond distances and angles.
2.2. Synthesis of 2-(2-thienyl)ethyl chloride
A solution of 3.28 g (28 mmol) of thionyl chloride
made in 50 cm3 of chloroform was added drop wise in
nearly 30 min with vigorous stirring to 3.28 g (26 mmol)
of 2-(2-thienyl)ethanol (Aldrich, USA) and 2.17 g (21
mmol) of triethylamine, both dissolved in 50 cm3 of
chloroform and cooled in ice bath. The mixture was
further stirred in ice bath for 10 min and thereafter he-
ated on steam bath until hydrogen chloride evolution
ceased. After cooling, the deep red coloured solution
was poured in 100 cm3 of ice-cold 1 N hydrochloric acid
and the mixture was extracted 3–4 times with chloro-
form. The chloroform extracts were combined, washed
successively with 1 N hydrochloric acid, 2 N sodium
bicarbonate and water and dried over anhydrous so-
dium sulfate. The chloroform was evaporated off on a
rotary evaporator to give dark red coloured liquid.
attached. In
(CH2CH2C4H3S) group was modelled by setting the
bond distances and angles to be essentially the same as
6
the disorder in the second
1
Yield: ꢂ70%. NMR: H (CDCl3, 25 °C): d (vs TMS):
3.28–3.32 (t, 2H, H2), 3.72–3.77 (t, 2H, H1), 6.91–6.92(t,
1H, H4), 6.97–7.00 (m, 1H, H5), 7.20–7.22 (d, 1H, H6).
2.3. Synthesis of 2-[2-(4-methoxyphenyltelluro)ethyl]-
thiophene (L1)
Bis(4-methoxyphenyl)ditelluride (0.50 g, 1.0 mmol)
was dissolved in 30 cm3 of ethanol and the solution set
to reflux under nitrogen atmosphere. A solution of so-
dium borohydride in NaOH (5%) was added dropwise
to the refluxing solution of the ditelluride under nitrogen
Fig. 1. ORTEP plot of the molecule 2.
Table 2
ꢀ
Selected bond lengths (A) and bond angles (°) of 2
Bond length
Bond angle
Pd(1)–Te(1)
Pd(1)–Te(2)
Pd(1)–Cl(1)
Pd(1)–Cl(2)
Pd(1)–Pd(1A)
Te(1)–C(6)
Te(1)–C(8)
Te(2)–C(19)
Te(2)–C(21)
Te1ꢁ ꢁ ꢁCl1A/
Te1Aꢁ ꢁ ꢁCl1
Te2ꢁ ꢁ ꢁCl2A/
Te2Aꢁ ꢁ ꢁCl2
Pd–Pd
2.5951(7)
2.5872(7)
2.300(2)
2.299(2)
3.214(1)
2.143(7)
2.117(7)
2.133(6)
2.114(7)
3.450
Cl(1)–Pd–Cl(1)
177.06(7)
176.55(3)
85.18(5)
94.08(5)
94.64(5)
85.93(5)
93.6(3)
Te(1)–Pd(1)–Te(2)
Cl(1)–Pd(1)–Te(1)
Cl(1)–Pd(1)–Te(2)
Cl(2)–Pd(1)–Te(1)
Cl(2)–Pd(1)–Te(2)
C(6)–Te(1)–C(8)
C(19)–Te(2)–C(21)
C(19)–Te(2)–Pd(1)
C(21)–Te(2)–Pd(1)
94.2(3)
106.3(2)
100.9(2)
3.449
C(6)–Te(1)–Pd(1)
C(8)–Te(1)–Pd(1)
107.7(2)
96.6(2)
3.214(1)
Fig. 2. ORTEP plot of the molecule 6.

S. Bali et al. / Journal of Organometallic Chemistry 689 (2004) 2346–2353
2349
Table 3
a
ꢀ
Selected bond lengths (A) and angles (°) of 6
Bond lengths
Ru(1)–Te(1)
Ru(1)–C(13)
Ru(1)–C(16)
Te(1)–C(1)
S(1)–C(3)
2.6528(9)
2.202(9)
2.209(8)
2.155(8)
1.734(7)
1.494(8)
Ru(1)–Cl(1)
Ru(1)–C(14)
Ru(1)–C(17)
S(1)–C(6)
2.415(2)
2.184(9)
2.174(8)
1.720(8)
1.528(8)
1.721(8)
1.493(8)
Ru(1)–Cl(2)
Ru(1)–C(15)
Ru(1)–C(18)
Te(1)–C(7a)
C(9A)–S(2a)
C(7A)–C(8a)
2.422(2)
2.204(9)
2.161(8)
2.167(7)
1.734(7)
1.528(8)
C(1)–C(2)
C(12A)–S(2a)
C(8A)–C(9a)
C(2)–C(3)
Bond angles
Cl(1)–Ru(1)–Cl(2)
C(1)–Te(1)–Ru(1)
C(6)–S(1)–C(3)
C(2)–C(1)–Te(1)
88.53(8)
100.5(2)
92.2(4)
Cl(1)–Ru(1)–Te(1)
C(7A)–Te(1)–Ru(1)
C(12a)-S(2a)–C(9a)
C(3)–C(2)–C(1)
84.47(6)
103.8(2)
92.2(4)
Cl(2)–Ru(1)–Te(1)
C(1)–Te(1)–C(7a)
C(8a)–C(7A)–Te(1)
C(9a)–C(8A)–C(7a)
86.90(6)
96.2(3)
108.2(5)
113.9(5)
113.2(5)
113.9(5)
a The disorder in the second (CH2CH2C4H3S) group was modelled by setting the bond distances and angles to be essentially the same as in the first.
atmosphere until it became colourless due to the for-
mation of ArTeꢀ Naþ. 2-(2-Thienyl)ethyl chloride dis-
solved in 5 cm3 of ethanol was added to this solution
with constant stirring. The reaction mixture was refluxed
further for 2–3 h, cooled to room temperature 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 anhy-
drous sodium sulphate. The solvent was evaporated off
under reduced pressure on a rotary evaporator, resulting
in red oil, which was extracted with hexane. On re-
moving hexane from the extract under reduced pressure
on a rotary evaporator ligand L1 was obtained as clear
yellow oil. Yield: 80%. Anal. Calc. for C13H14OSTe: Te,
OCH3), 6.72–6.75 (bt, 3H, H4 + ArH m to Te), 6.81–6.84
(m, 1H, H5), 7.12 (d, J ¼ 5:0 Hz, 1H, H6), 7.54 (d, J ¼ 9
Hz, 2H, ArH o to Te).
2.5. Synthesis of [PdCl2(L1)2] (2)
To a solution of L1 (0.17 g, 0.50 mmol) made in 10
cm3 of acetone was added Na2[PdCl4] (0.08 g, 0.25
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 ex-
tracted into chloroform (100 cm3). The extract was dried
over anhydrous sodium sulphate, concentrated to ꢂ10
cm3 and mixed with hexane (20 cm3). The resulting
reddish solid was filtered, washed with hexane and dried
in vacuo. The single crystals of the complex 2 were
grown from chloroform hexane mixture (1:1). Yield:
75%; m.p., 110 °C. Mol. wt.: Found, 1726; Calc. 869.1.
1
36.92. Found: Te, 36.74%. NMR: H (CDCl3, 25 °C): d
(vs TMS): 3.03–3.08 (m, 2H, H1), 3.23–3.28 (m, 2H, H2),
3.77 (s, 3H, OCH3), 6.71–6.77 (m, 3H, H4 and ArH m to
Te), 6.87–6.89 (t, 1H, H5), 7.09 (d, J ¼ 1:2 Hz, 1H, H6),
7.66–7.69 (m, 2H, ArH o to Te); 13C{1H} (CDCl3,
25 °C): (vs TMS): 8.57 (C1), 29.65 (C2), 54.76 (OCH3),
100.19 (ArC-Te), 114.02 (ArC m to Te), 124.01 (C4),
124.63 (C6), 126.45 (C5), 140.32 (ArC o to Te), 145.37
(C3), 159.44 (ArC p to Te).
KM, 5.26 ohmꢀ1 cm2 molꢀ1
.
Anal. Calc. for
C26H28Cl2O2PdS2Te2: C, 35.90; H, 3.22; Te, 29.37.
Found: C, 35.41; H, 3.01; Te, 28.98%. NMR: 1H
(CDCl3, 25 °C): d (vs TMS): 3.10–3.40 (bd, 3H,
2H2 + 1H1), 3.50 (bs, 1H, H1), 3.83 (s, 3H, OCH3), 6.81–
6.82 (m, 1H, H4), 6.88–6.91 (bm, 2H, H5 + ArH m to
Te), 7.13–7.15 (t, 1H, H6), 7.20–7.60 (bd, 2H, ArH o to
Te).
2.4. Synthesis of [AgNO3(L1)] (1)
A solution of AgNO3 (0.1 g, 0.58 mmol) made in 15
cm3 of dry acetonitrile was stirred under dry nitrogen
atmosphere in absence of light with a solution of L1
made in 10 cm3 of chloroform. The mixture was stirred
at room temperature for 1 h. The pink coloured complex
precipitated, which was filtered, washed well with ace-
tone followed by cold chloroform and dried in vacuo. It
was recrystallized using acetonitrile. Yield: 70%; m.p.,
130 °C (d). Mol. wt.: Found, 511; Calc. 515.5. KM, 28.15
ohmꢀ1 cm2 molꢀ1. Anal. Calc. for C13H14NO4STeAg: C,
30.26; H, 2.71; N, 2.51; Te, 24.80. Found: C, 30.31; H,
2.6. Synthesis of PtCl2(L1)2 (3)
A solution of L1 (0.17g, 0.50 mmol) made in 10 cm3
of acetone was added to K2[PtCl4] (0.08 g, 0.25 mmol)
dissolved in 10 cm3 of water. The resulting mixture was
stirred for 3 h at room temperature and poured into 100
cm3 of water. The complex was extracted into chloro-
form (100 cm3). The extract was dried over anhydrous
sodium sulphate, concentrated to ꢂ10 cm3, and mixed
with hexane (20 cm3). The resulting orange colored
compound was filtered, washed with hexane and re-
crystallized from chloroform: hexane (2:1) mixture.
Yield: 78%; m.p., 91–94 °C. Mol. wt.: Found, 955; Calc.
1
2.68; N, 2.36 Te, 24.10%. NMR: H (CH3CN, 25 °C):
(vs TMS): 3.06 –3.09 (2t, 4H, H1 + H2), 3.69 (s, 3H,

2350
S. Bali et al. / Journal of Organometallic Chemistry 689 (2004) 2346–2353
957.3. KM, 8.67 ohmꢀ1 cm2 molꢀ1. Anal. Calc. for
C26H28Cl2O2PtS2Te2: C, 32.59; H, 2.92; Te, 26.65.
Found: C, 32.08; H, 2.85; Te, 26.09. NMR: 1H (CDCl3,
25 °C): d (vs TMS): 2.87–2.95 (m, 1H, H2), 3.18–3.26 (m,
1H, H2), 3.33–3.43 (m, IH, H1), 3.59–3.65 (m, 1H, H1),
3.74–3.87 (s, 3H, OCH3), 6.69–6.81 (m, 3H, H4 and Ar–
H m to Te), 6.84–6.89 (m, 1H, H5), 7.06–7.15 (m, 1H,
H6), 7.26–7.37 (m, 1H, ArH o to Te), 7.46–7.49 (d,
J ¼ 8:5 Hz, 1H, ArH o to Te).
2.9. Synthesis of L2
Tellurium powder (0.65 g, 5 mmol) and sodium bo-
rohydride (0.38 g, 10 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.
To the resulting colourless thin slurry of Na2Te kept
under reflux, a solution of 2-(2-thienyl)ethyl chloride
(1.47 g, 10 mmol) made in 5 cm3 of ethanol was added
drop wise with constant stirring under nitrogen atmo-
sphere. The mixture was cooled to room temperature
and poured into 100 cm3 of water. The ligand L2 was
extracted into diethyl ether 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 ob-
tained as a reddish yellow viscous liquid that is unstable
as it shows the sign of decay within few days. Yield:
79%. Anal. Calc. for C12H14S2Te: Te, 36.49, Found: Te,
2.7. Synthesis of [HgBr2(L1)]2 (4)
The HgBr2 (0.20g, 0.55 mmol) dissolved in acetone
(20 cm3) was mixed with a solution of L1 (0.17g, 0.55
mmol) made in chloroform (20 cm3). The resulting
mixture was stirred at room temperature 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 chlo-
roform and filtered through celite. The filtrate was
concentrated to 10 cm3 and mixed with 20 cm3 of hex-
ane. A white complex was separated, filtered, dried in
vacuo. and recrystallized from chloroform–hexane (1:1)
mixture. Yield: 70%; m.p. 65 °C; Mol. wt.: Found, 1403;
Calc. 1412. KM, 9.38 ohmꢀ1 cm2 molꢀ1. Anal. Calc. for
C13H14OSTeHgBr2: C, 22.09; H, 1.98; Te, 18.00. Found:
C, 21.77; H, 1.91; Te, 17.72%. NMR: 1H (CDCl3,
1
36.36%. H NMR (CDCl3, 25 °C): d (vs TMS): 2.88–
2.93 (t, 2H, H1), 3.26–3.31 (t, 2H, H2), 6.83–6.84 (d,
J ¼ 3 Hz, 1H, H4), 6.92–6.95 (m, 1H, H5), 7.14–7.16 (d,
J ¼ 6 Hz, 1H, H6). 13C{1H} (CDCl3, 25 °C): d (vs
TMS): 3.96, 4.73 (C1), 31.74. 34.21 (C2), 124.25 (C4),
125.61 (C6), 126.68 (C5), 145.34 (C3).
2.10. Synthesis of {Ru(p-cymene)Cl2(L2)} (6)
1
25 °C): d (vs TMS): H (CDCl3, 25 °C): d (vs TMS):
To a solution of [RuCl2(p-cymene)]2 (0.61g, 1 mmol)
made in 20 cm3 of dichloromethane was added a solution
of L2 (0.68 g, 2 mmol) made in 10 cm3 of dichlorome-
thane. The mixture was stirred for 2 h at room temper-
ature. The solvent was completely removed on a rotary
evaporator under reduced pressure. The residue obtained
was dissolved in dichloromethane (5 cm3) and mixed
with hexane (10 cm3). The resulting red precipitate was
filtered, washed with hexane and dried in vacuo. The
single crystals suitable for diffraction were grown from
chloroform hexane 1:1 mixture. Yield: 74%; m.p., 99 °C.
Mol. wt.: Found, 652; Calc. 655.7. KM, 10.47
ohmꢀ1 cm2 molꢀ1. Anal. Calc. for C22 H28Cl2RuS2Te: C,
40.26; H, 4.27; Te, 19.46. Found: C, 40.01; H, 4.23; Te,
3.37–3.41 (t, 2H, H2), 3.69– 3.72 (t, 2H, H1), 3.76 (s, 3H,
OCH3), 6.87–6.94 (m, 4H, ArH m to Te + H4 + H5)
7.14–7.16 (m, 1H, H6), 7.65 – 7.67 (m, 2H, ArH o
to Te).
2.8. Synthesis of [Ru(p-cymene)Cl2(L1)] (5)
The [RuCl2(p-cymene)]2 (0.61g, 1 mmol) was dis-
solved in 20 cm3 of dichloromethane. A solution of L1
(0.69g, 2 mmol) made in 10 cm3 of dichloromethane was
added to it. The mixture was stirred for 2 h at room
temperature. The solvent was completely removed on a
rotary evaporator under reduced pressure. The residue
obtained was dissolved in dichloromethane (5 cm3) and
mixed with hexane. The resulting red precipitate was
filtered, washed with hexane and dried in vacuo. The
complex was crystallized using chloroform hexane 1:1
mixture. Yield: 76%; 160 °C (d). Mol. wt.: Found, 646;
Calc. 651.7. KM, 9.48 ohmꢀ1 cm2 molꢀ1. Anal. Calc. for
C23H24OSRuTe: C, 42.35; H, 3.68; Te, 19.50. Found: C,
42.01; H, 3.66; Te, 19.02%. NMR: 1H (CDCl3, 25 °C): d
(vs TMS): 1.23 (d, J ¼ 3 Hz, 6H, CH3 of i-Pr), 2.15 (s,
3H, CH3 of p-cymene), 2.84 (t, 2H, H2), 3.04–3.07 (m,
1H, CH of i-Pr), 3.32 – 3.41 (bd, 2H, H1), 3.84 (s, 3H,
OCH3), 4.86–5.39 (m, 4H, Ar–H p-cymene), 6.72 –6.83
(m, 1H, H4), 6.85–6.89 (m, 3H, ArH m to Te + H5),
7.05– 7.07 (m, 1H, H6), 7.66–7.83 (2d, 2H, ArH o to Te).
1
19.09%. NMR: H (CDCl3, 25 °C): d (vs TMS): 1.24–
1.26 (d, J ¼ 6 Hz, 6H, CH3 p-cymene), 2.16 (s, 3H,
Ar–CH3 p-cymene), 2.77– 2.82 (m, 1H, CH p-cymene),
2.84–2.91 (m, 1H, H2), 3.12–3.17 (t, 2H, H1 + H2), 3.22–
3.27 (m, 1H, H1), 5.14–5.16 (d, J ¼ 5:3 Hz, 2H, Ar–H p-
cymene), 5.26–5.28 (d, J ¼ 4:8 Hz, Ar–H p-cymene), 6.85
(bs, 1H, H4), 6.95 (m, 1H, H5), 7.17–7.18 (m, 1H, H6).
2.11. Synthesis of [PdCl2(L2)2] (7)
PdCl2 (0.07g, 0.39 mmol) was stirred with 5 ml of dry
benzonitrile and the mixture was warmed to give a clear
solution. After cooling the clear solution to room tem-
perature it was mixed with a solution of L2 (0.27g, 0.78

S. Bali et al. / Journal of Organometallic Chemistry 689 (2004) 2346–2353
2351
mmol) made in 10 cm3 of chloroform. The mixture was
further stirred for 3 h at room temperature. The solvent
was completely removed on a rotary evaporator under
reduced pressure. The residue obtained was dissolved in
dichloromethane (5 cm3) and mixed with hexane. The
resulting red brown precipitate was filtered, washed with
hexane and dried in vacuo. The complex was crystallized
using chloroform hexane 1:1 mixture. Yield: 70%; m.p.
85 °C. Mol. wt.: Found, 869; Calc. 876.6. KM, 12.41
ohmꢀ1 cm2 molꢀ1. Anal. Calc. for C24H28S4Te2PdCl2:
C, 32.85; H, 3.19; Te, 29.11. Found: C, 32.61; H, 3.16 ;
Te, 29.08%. 1H NMR (CDCl3, 25 °C): d (vs TMS):
2.87–2.97 (m, 2H, H2), 3.35–3.37 (m, 6H, 4H1 and 2H2),
6.87–6.88 (d, J ¼ 3 Hz, 1H, H4), 6.92–6.95 (m, 1H, H5),
7.16–7.17 (d, J ¼ 4:4 Hz, 1H, H6). 13C{1H} (CDCl3,
25 °C): d (vs TMS): 16.85 (C1), 29.83. (C2), 124.14 (C4),
125.38 (C6), 127.12 (C5), 145.75 (C3).
mondentate bonding mode in this complex. The CH2Te
1
signal in H NMR of silver complex appears shielded
with respect to that of free L1. Similar observations are
reported earlier also when formation of a metal-tellu-
rium bond by a 3/4d10 metal occurs [2–4]. Thus the co-
ordination number of Ag in its complex appears to be
two (coordinated by Te and O of NOꢀ3 group). The
complex 4 exhibits bands at 225, 235 and 290 cmꢀ1 in-
dicating the presence of both bridging and terminal Br
ligands. The CH2 protons in 4 appear ꢂ0.1–0.6 ppm
deshielded with respect to those of L1, indicating the
ligation of the ligand L1 through Te. Thus 4 appears to
be dimeric having two bromo bridges and its Hg is co-
ordinated by Te and three bromine atoms. The most
plausible geometry of Hg in 4 appears to be tetradeh-
dral. In the complexes 2 and 3 m (M–Cl) appears at 330
and 315 cmꢀ1 indicating the presence of two trans M–Cl
bonds of a square planar complex. However in the
spectrum of 7 (also square planar most probably) the m
(M–Cl) due to two trans Pd–Cl appears at 348 cmꢀ1. IR
spectrum of 5 has msyn(Ru–Cl) and masym(Ru–Cl) at 350
and 330 cmꢀ1, respectively, whereas that of 6 has these
band at 325 and 305 cmꢀ1, respectively. In complexes 1,
2, 3, 5, 6 and 7 H1 protons appear deshielded (ꢂ0.25–
0.5) whereas H2 protons and aryl protons ortho to tel-
lurium appear almost unaffected or shielded (up to 0.4
ppm). These observations suggest that there is weak
intramolecular Sꢁ ꢁ ꢁTe interaction in the ligands, which
breaks down on complex formation through Te donor
site resulting in the shielding of H2 and ArH ortho to Te,
otherwise they are expected to exhibit small deshielding.
Thienyl protons are marginally affected on complex
formation and sulfur of thienyl group is not involved in
ligation of L1 and L2 as evidenced by single crystal
structures of 2 and 6. Therefore L1 and L2 coordinate in
all seven complexes through Te alone. The presence of
positive charge on sulfur probably blocks its coordina-
tion. The two signals for C1 and C2 in 13C{1H} NMR
spectrum of L2 appear probably due to the presence of
its two conformers.
3. Results and discussion
The ligand L1 synthesized by the sequence of reac-
tions given in Scheme 1 was found stable for two months
under ambient conditions. Thereafter, deposition of
white solid starts in the oil L1, which is most likely a
tellurium dioxide formed by oxidative decomposition of
L1. However, L2 begins to show the sign of decompo-
sition after storing it for four days at room temperature
but TeO2 appears to be again formed. Generally Te-
alkyl bond is considered weaker with respect to that of
Te-aryl bond and this may be responsible for the dif-
ference between stability of L1 and L2 as in the later
both Te–C bonds are Te-alkyl ones. All the complexes
1–7 of both the ligands can be stored at room temper-
ature for two months easily. Both L1 and L2 and their
complexes are highly soluble in chloroform and dichlo-
romethane and moderately soluble in acetone. In
methanol, ethanol and hexane the two ligands are
sparingly soluble. The molecular weight and conduc-
tance measurements on complexes 1–7 suggest that 1, 3
and 5–7 are monomeric in nature and complex and 4 is
dimeric. All the complexes are non-electrolytes. In IR
spectrum of Ag(I) complex two bands appear at 1384
and 1487 cmꢀ1 and there is no band at 1700–1800 cmꢀ1
(due to free NOꢀ3 ). This suggests that nitrate is in a
3.1. Crystal structures of 2 and 6
The molecular structure of 2 is shown in Fig. 1.
Palladium has nearly square planar geometry and a
SOCl2
-
BH4
CH2CH2OH
S
-
+
CHCl3
Dry
/ Te
ArTe
EtOH
/ L2
1/2
Ar2Te2
/ Te
CH2CH2Cl
S
EtOH
Reflux
Et3N, Reflux
OMe
=
Ar
L1
Scheme 1.

2352
S. Bali et al. / Journal of Organometallic Chemistry 689 (2004) 2346–2353
trans structure having two tellurium atoms and two
chlorine atoms in its coordination sphere. Pd–Te bond
ꢀ
distances 2.5951(7) and 2.5872(7) A of 2 are compa-
rable with the reported values for other trans-
[PdCl2(Te-ligand)2] complexes; 2.5873(2)[14], 2.5865(2)/
The smaller difference between Ru–Te/Pd–Te bond
lengths of 2 and 6 with respect to values reported in
literature may also arise from a combination of steric
and electronic effects of various organic groups/moieties
present in the organotellurium ligands which due to
large size of Te are more prone to these effects. However,
the contribution of crystal packing to the variation of
these bond lengths may also not be ruled out, particu-
larly in view of large size of tellurium atom.
On the basis of spectroscopic evidences it appears
that in 3 and 7 metal atoms also have square planar
geometry as supported in case of 2 by single crystal
structure determination. Similarly 5 may be described
like 6 as a half sandwich compound containing p-cym-
ene as p-ligand and two Cl and L2 (bonded through Te)
as three two electron donors.
2.6052(2)[15]
and
2.5975(6)/2.6021(6)[15]
when
Te-ligands are bis(2-{1,3-dioxan-2-yl}ethyl) telluride, N-{2-
(4-methoxyphenyltelluro)ethyl}morpholine and bis{2-
(N-morpholino)ethyl} telluride, respectively. However,
for complex [PdCl2{4-MeOC6H4TeCH2CH2SEt}] [16]
ꢀ
the reported Pd–Te bond distance 2.492(13) A is
shorter than those of 2. It may be due to chelate effect
of the bidentate ligand. The strong trans influence
exerted in 2 by each Pd–Te bond on the other is
probably responsible for this elongation. The Pd–Cl
bond lengths 2.3006(18)/2.2990(18) 2.6528(9) are also
comparable with the values reported for other trans-
ꢀ
[PdCl2(Te-ligand)2] complexes (2.9990(8)–2.329(2) A).
The bond angles at Te are consistent with its nearly
trigonal pyramidal (93.6(3)–107.67(18)°) geometry. The
unique feature of crystal structure of 2 is the inter-
molecular interaction between Te coordinated to Pd
4. Conclusion
The ligands 2-[2-(4-methoxyphenyltelluro)ethyl]thio-
phene (L1) and bis[2-(2-thienyl)ethyl] telluride (L2) are
the first examples of thienyl group containing tellurides
studied extensively for ligation reactions. The L1 and L2
are synthesized and properly characterized for the first
time. The palladium(II) complex of L1 has an unique
structure in which there are intermolecular interactions
between Te coordinated to Pd and Cl atoms and two Pd
atoms of neighbouring molecules are closer than the
sum of van der Waal’s radii. These secondary interac-
tions in 2 result in the formation of a dimeric species,
which remains intact even in the solution as supported
by molecular weight values. Complex 6 is the first
structurally characterized example of Ru(II) complex
formed with thienyl group containing telluride.
ꢀ
and Cl (Teꢁ ꢁ ꢁCl distances 3.449/3.450 A are shorter
ꢀ
than sum of van der Waal’s radii 4 A). These sec-
ondary interaction in 2 (may be supported a little bit
by crystal forces) reduces Pd–Pd distance between the
ꢀ
two molecules to 3.2143(10) A (sum of van der Waal’s
ꢀ
radii is 3.26 A) and result in the formation of a di-
meric species, which remains intact even in the solu-
tion as molecular weight of 2 is found to be double of
the value expected for a monomeric moiety. This in-
dicates that secondary intermolecular Teꢁ ꢁ ꢁCl interac-
tions are significantly strong [20a] and not fully
dissociated on dissolution in chloroform. However, the
dimeric nature even in solution suggests that the ten-
dency of Te and Cl to form supramolecular associa-
tions [20a] through inter/intramolecular interaction is
mainly responsible for dimmer formation.
Acknowledgements
The molecular structure of 6 is shown in Fig. 2. It is a
half-sandwich compound in which two chlorine atoms,
the tellurium atom and the p-cymene ring constitute the
coordination sphere around ruthenium. The Ru–Te bond
A.K.S. and S.B. thank Council of Scientific and In-
dustrial Research (India) for financial assistance (Project
No. 01(1849)/03/EMR-II). M.B.H. thanks the UK En-
gineering and Physical Sciences Council for support of
the X-ray facilities at Southampton. J.E.D. thanks the
University of Windsor for financial support. P.S. is
thankful to Instituto de Quimica, UNAM and DGAPA,
UNAM for sabbatical leave at IIT, Delhi.
ꢀ
length of 2.6528(9) A is consistent with the values 2.651(5)
ꢀ
and 2.6559(9) A reported for [Ru(p-cymene)Cl2{bis(1,3-
dioxan-2yl)}ethyl telluride}] [14] and [Ru(p-cymene)Cl2
{N-[2-(4-methoxyphenyltelluro)ethyl]phthalimide}][17]
but some what longer than the values 2.619(8), 2.642(1),
ꢀ
2.6381(16)/2.6411(2) A observed for [Ru(p-cymene)Cl2L]
type of complexes when L ¼ 2-(4-ethoxyphenlytellurom-
ethyl)tetrahydro-2H-pyran [18], 2-(2-{4-ethoxyphenyl}
telluroethyl)-1,3-dioxane[18] and bis{(4-methoxyphenyl-
telluro)} methane [19], respectively. The Ru–Cl bond
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