Chemistry of 2-thienyl derivatives of arsenic and antimony: Synthesis and characterization; X-ray structure of [PdCl2{(C4H3S)3As}2]

Article abstract of DOI:10.1016/S0277-5387(02)01375-X

Tri-(2-thienyl)-arsine and -stibine, Th₃E (E =As; Sb), were prepared by the reaction of 2-thienylmagnesium bromide and the appropriate metal trichloride. Several derivatives of the general formulae E(C₄H₃S)₃X₂ (X = Cl, Br, OAc; E = As, Sb) have been prepared. So as to explore the coordination behaviour of Th₃E, a series of complexes of the type MCl₂(AsTh₃)₂, [PdX₂(μ-Y)₂(AsTh₃)₂], [PdCl(S∧S)(AsTh₃)] [M = Pd, Pt; X = Cl, Me; Y = Cl, dmpz, pz, S∧S = S₂P(OEt)₂, S₂P(OPrⁱ)₂] have also been prepared. All complexes have been characterized by elemental analysis, IR and NMR spectroscopy, and show that these ligands coordinate to palladium(II) and platinum(II) through E (As or Sb) exclusively. The molecular structure of [PdCl₂(AsTh₃)₂] has been established by X-ray structural analysis and reveals a square planar geometry for palladium defined by an As₂Cl₂ donor set.

Full text of DOI:10.1016/S0277-5387(02)01375-X

Polyhedron 22 (2003) 549Á555
/
www.elsevier.com/locate/poly
Chemistry of 2-thienyl derivatives of arsenic and antimony: synthesis
and characterization; X-ray structure of [PdCl2{(C4H3S)3As}2]
H. Mahalakshmi a, Vimal K. Jain a,*, Edward R.T. Tiekink b,*
a Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
b Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
Received 7 October 2002; accepted 22 November 2002
Abstract
Tri-(2-thienyl)-arsine and -stibine, Th3E (Eꢀ
appropriate metal trichloride. Several derivatives of the general formulae E(C4H3S)3X2 (Xꢀ
prepared. So as to explore the coordination behaviour of Th3E, a series of complexes of the type MCl2(AsTh3)2, [PdX2(m-
Y)2(AsTh3)2], [PdCl(SfflS)(AsTh3)] [Mꢀ Cl, dmpz, pz, SfflSꢀS2P(OEt)2, S2P(OPri)2] have also been
Pd, Pt; XꢀCl, Me; Yꢀ
/As; Sb), were prepared by the reaction of 2-thienylmagnesium bromide and the
/
Cl, Br, OAc; EꢀAs, Sb) have been
/
/
/
/
/
prepared. All complexes have been characterized by elemental analysis, IR and NMR spectroscopy, and show that these ligands
coordinate to palladium(II) and platinum(II) through E (As or Sb) exclusively. The molecular structure of [PdCl2(AsTh3)2] has been
established by X-ray structural analysis and reveals a square planar geometry for palladium defined by an As2Cl2 donor set.
# 2002 Elsevier Science Ltd. All rights reserved.
Keywords: 2-Thienyl derivatives; Arsenic; Antimony; X-ray structures; [PdCl2{(C4H3S)3As}2]
1. Introduction
Metal complexes containing chelating ditholates (such
as xanthates, dithiocarbamates, dithiophosphates) have
been employed as single source precursors to deposit
metal sulphide films [6]. Group V organometallic
complexes derived from such ligands have been investi-
gated quite extensively [7]. In this connection, a family
of new single source precursors of Group V elements
containing a thienyl group may be conceived.
Organometallic compounds of the Group V elements
find extensive applications as molecular precursors in
chemical vapour deposition procesess (MOCVD) for the
deposition of a wide variety of semiconductors. The
search for better precursors with desirable properties has
been a driving force for the continued current interest in
the organometallic chemistry of these elements.
Interestingly synthesis, spectroscopy [8Á
/
11] and co-
ordination chemistry [12Á15] of several 2-thienylpho-
/
The VÁ/VI compound semiconductors differ greatly
sphines have been reported, but the thienyl derivatives
of heavier Group V congenors are conspicously missing.
With this perspective it was considered worthwhile to
synthesize 2-thienyl derivatives of arsenic and antimony,
and to study some of their chemical and physical
properties.
from their IIIÁ
which are influenced by non-stoichiometry. For exam-
ple, incorporation of copper can convert p-type Bi2Te3
/
V derivatives in their extrinsic properties
to n-type. The VÁVI compound Bi2Te3 is one of the best
/
room temperature thermocouple materials for thermo-
electric cooling [1]. Thin films of As2S3 (band gap 2.36
eV) are used for holographic recording [2], optical
memories [3], relief imaging [4], high resolution micro-
lithography [5], etc.
2. Experimental
2.1. Materials and instrumentation
* Corresponding authors. Tel.: ꢁ
/
91-22-559-5095; fax: ꢁ91-22-550-
/
5151.
E-mail addresses: jainvk@apsara.barc.ernet.in (V.K. Jain),
chmtert@nus.edu.sg (E.R.T. Tiekink).
All the reactions were carried out under a nitrogen
atmosphere in dry and distilled analytical grade sol-
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0277-5387(02)01375-X

550
H. Mahalakshmi et al. / Polyhedron 22 (2003) 549Á555
/
vents. 2-Bromothiophene was purchased from Fluka
and distilled prior to use. AsCl3 and SbCl3 were
obtained from commercial sources and distilled before
2.2.2. [(C4H3S)3Sb]
To an ethereal solution of 2-thienylmagnesium bro-
mide, C4H3SMgBr [prepared from Mg turnings (4.2 g,
0.17 mol) and C4H3SBr (28.2 g, 16.7 ml, 0.17 mol) in 300
ml ether], a solution of SbCl3 (9.61 g, 0.042 mol) in Et2O
at 0 8C was added over a period of 2 h. The reaction
mixture was stirred at r.t. for 3 h followed by refluxing
for 1 h. The reactants were cooled to 0 8C and treated
1
use. The H, 13C{1H} and 31P{1H} NMR spectra were
recorded on a Bruker DPX-300 spectrometer operating
at 300, 75.46 and 121.5 MHz, respectively. Chemical
shifts are relative to internal CHCl3 peak (d: 7.26 ppm
1
for H and 77.0 for 13C{1H}) and external 85% H3PO4
for 31P{1H}. IR spectra were recorded as Nujol mulls on
a CsI plates on a Bomen MB-102 FT IR spectro-
with deoxygenated aqueous NH4Cl solution (80Á100
/
ml). The ether layer was separated, dried over CaCl2 and
passed through a Florisil column. The solvent was
evaporated in vacuo leaving behind a yellow liquid
which was recrystallized from C6H14 to yield
[(C4H3S)3Sb] as an off-white crystalline solid in 65%
yield (10.2 g).
photometer in the range 4000Á
200 cmꢂ1. Microanalysis
of the complexes was carried out in the Analytical
Chemistry Division of BARC.
/
2.2. Preparations
2.2.3. [(C4H3S)3AsCl2]
To an ice cooled C6H14 solution (30 ml) of
[(C4H3S)3As] (4.0 g, 12.3 mmol), chlorine gas was
bubbled until precipitation of a white solid. This was
accompanied by a colour change of the solution from
pale-yellow to orange, to light-pink and finally, the
solution turned yellow. The supernatent was decanted
and solid washed with C6H14 and recrystallized from
2.2.1. [(C4H3S)3As] (Th3As)
To an ethereal solution of 2-thienylmagnesium bro-
mide, C4H3SMgBr [prepared from Mg turnings (4.7 g,
0.19 mol) and C4H3SBr (31.90 g, 19.0 ml, 0.19 mol) in
300 ml ether], a solution of AsCl3 (9.0 g, 0.05 mol) in
Et2O at 0 8C was added over a period of 2 h [16]. The
reaction mixture was stirred at room temperature (r.t.)
for 3 h followed by refluxing for 1 h. The reactants were
cooled to 0 8C and treated with deoxygenated aqueous
C6H6ÁC6H14 to yield [(C4H3S)3AsCl2] as an off-white
/
solid (4.17 g, 85%).
NH4Cl solution (80Á100 ml). The ether layer was
/
separated, dried over CaCl2 and passed through a
Florisil column. The solvent was evaporated in vacuo
leaving a yellow liquid, which was distilled under
vacuum to give a pale-yellow oil in 98% yield. b.p.
2.2.4. [(C4H3S)3SbBr2]
To an ice cooled C6H6ÁC6H14 (2:1) solution (30 ml)
/
of [(C4H3S)3Sb] (3.2 g, 8.75 mmol), a CCl4 solution of
bromine (1.40 g, 8.76 mmol) was added dropwise with
continuous stirring until the brown colour of bromine
150Á160/0.4 mm. Pertinent data are given in Table 1.
/
Table 1
Analytical data of tri-(2-thienyl)arsine and -stibine and their complexes
Compound
Recrystallization solvent (% yield)
M.p. (8C)
Analysis Found (Calc.)
C
H
N
[(C4H3S)3As]
[(C4H3S)3Sb]
liquid (98)
hexane (65)
43.8 (44.4)
38.7 (38.8)
34.9 (36.5)
27.0 (27.1)
39.8 (39.3)
35.2 (34.9)
30.8 (31.5)
32.6 (33.6)
33.1 (33.0)
37.3 (38.0)
36.8 (38.1)
29.3 (28.7)
32.1 (32.5)
35.7 (36.4)
39.5 (40.0)
38.1 (37.5)
31.3 (31.7)
28.9 (29.5)
2.4 (2.8)
2.4 (2.4)
1.9 (2.3)
1.7 (1.7)
2.7 (3.1)
2.0 (2.2)
1.7 (2.0)
3.6 (4.0)
2.5 (2.8)
2.5 (2.8)
4.1 (4.7)
1.5 (1.8)
2.3 (2.5)
2.3 (2.8)
3.2 (3.5)
2.9 (2.9)
2.9 (3.4)
2.4 (2.9)
45
[(C4H3S)3AsCl2]
[(C4H3S)3SbBr2]
benzeneÁ
benzeneÁ
benzeneÁ
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 (75)
/hexane (85)
123Á
175Á
174Á
222
230
/
124
176
176
/hexane (50)
/
[(C4H3S)3Sb(OAc)2]
[PdCl2(Th3As)2]
/CH2Cl2 Á
/hexane (39)
/
a
/
hexane (70)
hexane (42)
hexane (22)
hexane (82)
hexane (70)
hexane (40)
a
[PtCl2(Th3As)2]
/
[PtCl2(PPrn3)(Th3As)]
[PtCl2(PMe2Ph)(Th3As)]
[PtCl2(PMePh2)(Th3As)]
[PtCl(PfflC)(Th3As)]
[Pd2Cl2(m-Cl)2(Th3As)2]
[Pd2Me2(m-Cl)2(Th3As)2]
[PdCl(m-dmpz)(Th3As)]2
[PdMe (m-dmpz)(Th3As)]2
[PdMe (m-pz)(Th3As)]2
[PdCl{S2P(OPri)2}(Th3As)]
[PdCl{S2P(OEt)2}(Th3As)]
/
142Á143
/
/
215
197
185
210
/
/
a
a
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 Á
CH2Cl2 Á
benzeneÁ
/
hexane (55)
hexane (53)
hexane (57)
hexane (40)
hexane (51)
158Á159
/
a
/
236
182
120
162
167
4.4 (4.9)
5.2 (5.2)
5.0 (5.5)
a
/
/
a
a
/
/
hexane (42)
a
Melts with decomposition.

H. Mahalakshmi et al. / Polyhedron 22 (2003) 549Á
/555
551
persisted with a concomitant formation of a white solid.
The supernatent was decanted and solid washed with
2.2.9. [Pd2Cl2(m-Cl)2(Th3As)2]
To a MeOH solution (20 ml) of Na2PdCl4 (294 mg,
1.0 mmol), solid [PdCl2(Th3As)2] (820 mg, 0.99 mmol)
was added and the reaction mixture was stirred under
reflux for 4 h whereupon a brown precipitate formed.
After cooling to r.t., the solid was filtered through a
sintered disc, washed well with MeOH, water and finally
with a small amount of absolute EtOH. It was recrys-
tallized from CH2Cl2 as a brown solid in 75% yield (747
mg).
C6H14 and recrystallized from C6H6ÁC6H14 to yield
/
[(C4H3S)3SbBr2] as an off-white crystalline solid (2.32 g,
50%).
2.2.5. [(C4H3S)3Sb(OAc)2]
To a C6H6 solution of [(C4H3S)3SbBr2] (422 mg, 0.79
mmol), solid AgOAc (265 mg, 1.59 mmol) was added
with stirring which was continued for 6 h. Precipitated
AgBr was removed by filtration and the solvent was
evaporated in vacuo to give a white solid which on
2.2.10. [Pd2Me2(m-Cl)2(Th3As)2]
a
To
CH2Cl2 solution (15 ml) of [Pd2Cl2(m-
recrystallization from C6H6Á
/
CH2Cl2ÁC6H14 yielded a
/
Cl)2(Th3As)2] (442 mg, 0.44 mmol), Me4Sn (158 mg,
0.13 ml, 0.88 mmol) was added with stirring. An
immediate colour change from dark-brown to pale-
yellow and finally colourless was observed. The reaction
mixture was stirred at r.t. for 4 h. The solvent was
evaporated in vacuo to give a pale-yellow solid which
was washed well with C6H14 and recrystallized from
colourless crystalline solid in 39% yield (150 mg).
2.2.6. [PdCl2(Th3As)2]
To a C6H6 solution of Th3As (1.75 g, 5.4 mmol), solid
[PdCl2(PhCN)2] (1.03 g, 2.7 mmol) was added and the
reactants were stirred at r.t. for 6 h. The solvent was
CH2Cl2Á/C6H14 to give a pale-yellow solid (233 mg,
removed under vacuum leaving behind an orangeÁ
brown solid which was washed with C6H14 (3ꢃ10 ml)
and recrystallized from CH2Cl2ÁC6H14 as an orange
/
55%).
/
/
2.2.11. [PdCl(m-dmpz)(Th3As)]2
crystalline solid in 70% yield (1.5 g).
[PtCl2(Th3As)2] was prepared similarly from Th3As
and [PtCl2(PhCN)2] as a yellow solid in 42% yield.
To a CH2Cl2 solution of [Pd2Cl2(m-Cl)2(Th3As)2] (60
mg, 0.06 mmol), Nadmpz [prepared from a MeOH
solution (5 ml) of dmpzH (11 mg, 0.12 mmol) and
NaOH (0.005 g, 0.24 ml, 0.49 N)] was added dropwise
with constant stirring. An immediate colour change
from brown to pale-yellow was observed. The reactants
were stirred at r.t. for 4 h after which the solvent was
dried thoroughly in vacuo and extracted with CH2Cl2
and filtered. The solvent was evaporated under vacuum
to obtain a yellow solid that was recrystallized from
2.2.7. [PtCl2(PPrn3 )(Th3As)]
To a CH2Cl2 solution of [Pt2Cl2(m-Cl)2(PPrn3 )2] (48
mg, 0.056 mmol), a solution of Th3As (36 mg, 0.11
mmol) was added with stirring. A clear pale-yellow
solution was obtained almost immediately. The reac-
tants were stirred at r.t. for 4 h after which the solvent
was removed in vacuo to yield a white solid which was
CH2Cl2ÁC6H14 in 53% yield (35 mg).
/
[PdMe(m-dmpz)(Th3As)]2 and [PdMe(m-pz)(Th3As)]2
were prepared in a similar manner.
washed with C6H14 (3ꢃ
CH2Cl2ÁC6H14 as a white crystalline solid in 22% yield
(18 mg).
[PtCl2(PMe2Ph)(Th3As)],
and [PtCl(PfflC)(Th3As)] (PfflCꢀ
/
5 ml) and recrystallized from
/
2.2.12. [PdCl{S2P(OEt)2}(Th3As)]
[PtCl2(PMePh2)(Th3As)]
But2 PCCH2(Me)2)
To a C6H6 solution of [Pd2Cl2(m-Cl)2(Th3As)2] (63
mg, 0.063 mmol), solid NH4[S2P(OEt)2] (26 mg, 0.128
mmol) was added with stirring which was continued at
r.t. for 4 h. It was filtered and the filtrate was
concentrated in vacuo to obtain an orange oil which
/
were prepared in a similar manner.
2.2.8. [PdCl2(PMePh2)(Th3Sb)]
To a CDCl3 solution of [Pt2Cl2(m-Cl)2(PMePh2)2] (26
mg, 0.028 mmol), solid Th3Sb (21 mg, 0.057 mmol) was
added. A clear solution was obtained almost immedi-
ately. This solution was then studied by 1H and 31P
NMR spectroscopy.
on recrystallization from C6H6ÁC6H14 yielded an or-
/
ange crystalline solid (34 mg, 42%).
[PdCl{S2P(OPri)2}(Th3As)] was prepared in a similar
manner from [Pd2Cl2(m-Cl)2(Th3As)2] and NH4[S2P(O-
Pri)2] in 51% yield.
Attempted preparation of [PdCl2(PMePh2)(Th3Sb)].
To a CDCl3 solution of [Pd2Cl2(m-Cl)2(PMePh2)2] (27
mg, 0.036 mmol), solid Th3Sb (28 mg, 0.075 mmol) was
added. A clear solution was obtained almost immedi-
ately, although the solution turned black within a few
minutes. This solution was monitored by 31P NMR
spectroscopy.
2.3. Crystallography
Intensity data for an orange crystal of
[PdCl2(Th3As)2] (0.18ꢃ
at 183 K on a Bruker AXS SMART CCD diffract-
ometer fitted with Mo Ka radiation using v scans such
/
0.29ꢃ0.29 mm) were measured
/

552
H. Mahalakshmi et al. / Polyhedron 22 (2003) 549Á555
/
that umax was 30.08. Data were corrected for Lp as well
as for absorption employing an empirical procedure
[17a]. The structure was solved by heavy-atom methods
[17b] and refined (anisotropic displacement parameters,
data for the above and their complexes are collected in
Table 2. The IR spectra displayed a band of medium to
strong intensity at 476 n(AsÃ
/
C) and 473 n(SbÃ
/
C) cmꢂ1
,
C) stretchings. The H
1
respectively attributable to n(MÃ
/
H atoms in the riding model approximation and a
2
NMR spectra displayed characteristic resonances of the
thienyl group. In the 13C NMR spectra, the C-2
resonance of the stibine is shielded compared with the
arsine derivative (approximately 6 ppm) while the C-5
resonance of Th3Sb was slightly deshielded (approxi-
mately 3 ppm) compared with that for the arsine
analogue. The C-3 and C-4 resonances show very little
change on increasing the size of the metal atom.
weighting scheme of the form wꢀ
/
1/[s2(Fo )ꢁ
/
2
2
0.0508P2ꢁ
/
1.4976P] where Pꢀ
/
(Fo ꢁ2Fc )/3) by a full-
/
matrix least-squares procedure based on F2 [17c].
Disorder was evident for two of the thienyl groups
and this was resolved by refining each of the affected
thienyl groups over two positions. In effect, this meant
splitting the S2/C8 and S3/C12 positions, respectively.
For isotropic refinement, the site occupancy factors for
the major components were 0.638(5) and 0.548(5),
respectively. The atomic numbering scheme (50% prob-
ability level) is shown in Fig. 1 that was drawn with
ORTEP [17d]. Calculations were performed with the
teXsan package [17e].
Oxidation of Th3M with halogens readily afforded the
dihalides Th3MX2 (XꢀCl; Br) in fairly good yields.
/
Th3AsCl2 was highly hygroscopic while Th3SbBr2 was
obtained as an off-white crystalline solid. The IR
spectrum of Th3AsCl2 showed a band at 350 cmꢂ1
,
absent in the spectrum of Th3As, that was assigned to
n(AsÃ
Cl). Similarly, a strong band at 289 cmꢂ1 in the
spectra of Th3SbBr2 may be assigned to n(SbÃBr).
Medium to strong bands at 463 and 454 cmꢂ1 were
C), respectively. In the
Crystal data for [PdCl2(Th3As)2]: C24H18As2Cl2PdS6,
/
Mꢀ
8.6185(5), bꢀ
108.972(1)8, Vꢀ
Dcalcd, 1.921 g cmꢂ3, m 3.590 mmꢂ1, 4147 unique
reflections, 3659 reflections with I ]2s(I), R1(Fo) and
wR2(Fo) (I ]
/
825.9, monoclinic, space group P21/n, aꢀ
/
/
˚
/
18.5077(10), cꢀ
/
9.4670(5) A, bꢀ
/
/
1428.04(14), Zꢀ
/
4, Tꢀ183(2) K,
/
assigned to n(AsÃ
/
C) and n(SbÃ
/
1H NMR spectra, the H-3 and H-5 proton resonances of
the 2-thienyl group are considerably deshielded on
oxidation. In the 13C{1H} NMR spectra of these
dihalides, C-2, C-3 and C-5 resonances are slightly
/
/
2s(I)): 0.035 and 0.093, R1ꢂ(F3o) and wR2(Fo)
˚
(all data) 0.040, 0.0.095, rmax 0.97 e A
.
shifted (3Á4 ppm) than those of the corresponding
/
signals for Th3E. The C-4 resonance was little affected
on oxidation with halogens.
3. Results and discussion
The reaction of Th3SbBr2 with 2 equiv. of AgOAc in
benzene solution yielded [Th3Sb(OAc)2] as a white
crystalline solid. A medium intensity band at 1569
cmꢂ1, absent in the spectrum of Th3SbBr2 may be
Tri-(2-thienyl)-arsine and -stibine, Th3E (Thꢀ
/
C4H3S; EꢀAs, Sb), were prepared by the reaction of
/
assigned to n(CÄ
/
O). The 1H NMR spectrum displayed a
the metal trichloride MCl3 with 2-thienylmagnesium
bromide in dry ether. The arsine is a yellow liquid while
the stibine is a crystalline solid. Selected spectroscopic
single resonance at d 2.09 ppm for the acetate protons.
In the 13C{1H} NMR spectrum, a singlet at d 175.7 ppm
has been attributed to carbonyl carbon of the acetate.
The coordination chemistry of thienyl phosphines has
been explored to some extent [12Á15]. These ligands in
/
general coordinate to metal centres via the phosphorus
atom only. However, recently it has been demonstrated
that Ph2ThP can also act as a bidentate ligand in
[Re2(CO)8{m-PPh2(C4H3S)}], coordinating to rhenium
through both the phosphorous and sulphur atoms of the
Ph2ThP ligand [13f]. In view of the various possible
bonding modes of this family of ligands it was thought
of interest to examine coordination chemistry of Th3E
ligands (Eꢀ
/
As or Sb).
Reaction of [MCl2(PhCN)2] (Mꢀ/Pd or Pt) with 2
mol equiv. of Th3As yielded [MCl2(Th3As)2] as yellow
crystalline solids. The palladium complex displayed only
one n(PdÃ
/
Cl) stretching band at 328 cmꢂ1 indicating a
trans configuration. Only one set of resonances are
observed in the 1H NMR spectrum. By contrast, the 1H
NMR spectrum of the platinum complex exhibited two
sets of resonances; the minor set in approximately 10%
Fig. 1. Molecular structure and crystallographic numbering scheme
˚
for [PdCl2(Th3As)2]. Selected geometric parameters (A; 8): PdÃ
/
As
C1
2.4091(3); PdÃ
/
Cl 2.2865(7); ClÃ
C5 109.72(8), PdÃAsÃ
/
PdÃ
/
As 88.08(2), PdÃ
/
AsÃ
/
120.95(9), PdÃAsÃ
/
/
/
/C9 116.09(9).

H. Mahalakshmi et al. / Polyhedron 22 (2003) 549Á
/555
553
Table 2
IR and NMR data of tri-(2-thienyl)arsine and -stibine and their complexes
Compound
1H NMR data
(d)
13C{1H} NMR data
(d)
31P{1H} NMR data
(d)
IR (cmꢂ1
)
[(C4H3S)3As]
[(C4H3S)3Sb]
[(C4H3S)3AsCl2]
7.24 (dd, 3.3, 4 Hz, H-4); 7.45 (d, 3.3 Hz, H-3); 127.7 (C-4); 131.0 (C-3); 134.3
(C-5); 138.3 (C-2)
476 nAsÃ
473 nSbÃ
463 nAsÃ
/
C
C
C
7.66 (d, 3.8 Hz, H-5)
7.23 (dd, 3.3, 4.8 Hz, H-4); 7.40 (dd, 0.8, 3.3
Hz, H-3); 7.69 (dd, 0.8, 4.8 Hz, H-5)
128.1 (C-4); 132.5 (C-3); 132.7
(C-2); 137.1 (C-5)
/
7.19 (t, 4.3 Hz, H-4); 7.74 (d, 4.3 Hz, H-3); 8.28 127.3 (C-4); 134.3 (C-3); 137.9
/
(d, 3.0 Hz, H-5)
(C-5/C-2)
350 nAsÃ
Cl
454 nSbÃ
/
[(C4H3S)3SbBr2]
7.33 (dd, 3.8, 4.8 Hz, H-4); 7.85 (dd, 0.8, 4.8
Hz, H-3); 8.40 (dd, 0.8, 4.0 Hz, H-5)
128.0 (C-4); 135.4 (C-3); 136.2
(C-2); 140.0 (C-5)
/C
289 nSbÃ
/
Br
[(C4H3S)3Sb(OAc)2]
2.09 (s, CH3CO2); 7.14 (m); 7.35 (m); 7.66 (m) 20.2 (CH3CO2); 125.1, 126.8
(each singlet, for all 4 carbon
473 nSbÃ
/C
atoms); 175.5 (ÃCO)
/
1569 nCÄ
/
O
[PdCl2(Th3As)2]
[PtCl2(Th3As)2]
7.18 (t, 4 Hz, H-4); 7.65Á
/
7.70 (m, H-3, H-5)
472 nAsÃ
328 nPdÃ
Cl
/
C
/
7.04 (t, H-4); 7.37 (dd, H-3, H-5) a; 7.19 (t, 4.3
472 nAsÃ
/
C
b
Hz, H-4); 7.56Á7.67 (m, H-3, H-5)
/
279, 328
nPtÃCl
3288 325, 317
nPtÃCl
/
[PtCl2(PPrn3 )(Th3As)]
0.93 (t, 7 Hz, PCH2CH2Me); 1.48Á
/
1.67 (m,
PCH2CH2); 7.20 (t, 5 Hz, H-4); 7.65 (d, 4 Hz);
ꢂ
/
2.1 1J(PtÃ
Hz
/
P)ꢀ
/
/
7.70 (d, 4 Hz)
3
[PtCl2(PMe2Ph)(Th3As)]
1.67 (d, 11 Hz, J(PtÃ
/
H)ꢀ/32 Hz, PMe2); 1.89
ꢂ/
15.4 1J(PtÃ
Hz ꢂ10.9 small%
1J(PtÃ
P)ꢀ3245 Hz
2.2 1J(PtÃ
P)ꢀ3491 325 nPtÃ
Hz Cl
7.3 1J(PtÃ
Hz
/
P)ꢀ
/
3425 325 nPtÃ
/
(d, 11 Hz, small 5%); 7.07 (t, 3.6 Hz, H-4);
7.16Á7.65 (m, Ph, H-3, H-5)
1.67 (d, 11 Hz, PMe); 7.03 (dd, 3.6 Hz, 4 Hz,
H-4); 7.23Á7.61 (m, Ph, H-3, H-5)
1.64 (d, 13.5 Hz, PBut2 ); 1.48 (d, 13.8 Hz,
PCMe2); 1.26 (d, 13.6 Hz, PCÃCH2); 7.15 (t,
4.0 Hz, H-4); 7.60 (d, 4 Hz, H-3, H-5)
2.11 (d, 11 Hz, 3J(PtÃ
H)ꢀ42 Hz, PMe); 7.09Á
7.79 (m, PhꢁTh)
/
Cl
/
/
/
[PtCl2(PMePh2)(Th3As)]
[PtCl(PfflC)(Th3As)]
ꢂ/
/
/
/
/
ꢂ/
/
P)ꢀ
/
3038 325 nPtÃ
/
/
Cl
[PtCl2(PMePh2)(Th3Sb)]
/
/
/
ꢂ
Hz
/
3.3 1J(PtÃ
/
P)ꢀ
/
3516 487 nSbÃ
/
C
/
325 nPtÃ
/
Cl
[PdCl2(PMePh2)(Th3Sb)]
[Pd2Cl2(m-Cl)2(Th3As)2]
7.18 (d, 3.7 Hz, 4 Hz, H-4); 7.67 (d, 5 Hz), 7.69
(d, 4 Hz) (H-3, H-5)
268, 328,
352 nPdÃ
Cl
/
[Pd2Me2(m-Cl)2(Th3As)2]
[PdCl(m-dmpz)(Th3As)]2
0.86 (s, PdÃ
/
Me); 7.15 (m, H-4); 7.66 (m, H-3,
330 nPdÃ
/
H-5)
1.87 (s, 3-Me, pz); 2.47 (s, 5-Me, pz); 5.37 (s, 4-
H, pz); 7.03 (m, H-4); 7.56 (m, H-3, H-5)
Cl
[PdMe (m-dmpz)(Th3As)]2 0.48 (s, PdÃ
Me, pz); 5.52 (s, 4-H, pz); 7.02Á
7.55 (d, H-3, H-5)
0.54 (s, PdÃMe); 5.92 (s, H-4, pz); 6.78 (s, H-3,
5, pz); 7.01Á7.11 (m, H-4); 7.3Á7.6 (m, H-3, H-
5)
/
Me); 1.70 (s, 3-Me, pz); 2.38 (s, 5-
/
7.16 (m, H-4);
[PdMe (m-pz)(Th3As)]2
/
/
/
[PdCl{S2P(OPri )2}(Th3As)] 1.35, 1.39 (each d, 6.2 Hz, OCH2Me2); 4.83
(septet, 6.2 Hz, OCH2Ç); 7.19 (t, 8.5 Hz, H-4);
7.66 (dd, H-3, H-5)
97.5
317, 333
nPdÃCl
/
[PdCl{S2P(OEt)2}(Th3As)] 1.37 (t, 7.0 Hz, OCH2Me); 4.20 (q, 7.0 Hz,
OCH2Ç); 7.19 (m, H-4); 7.66 (d, 3.7 Hz, H-3,
H-5)
101.5
327 nPdÃ
/
Cl
a
Present in small % (approximately 10%) concentration, may be due to trans isomer.
These are major peaks due to cis isomer.
b

554
H. Mahalakshmi et al. / Polyhedron 22 (2003) 549Á555
/
concentration. The IR spectrum of the complex dis-
Cl) stretching bands (328 and 279
cmꢂ1) indicating that the complex exists in a cis
configuration, as is usually the case. The species in
approximately 10% concentration in solution may be the
trans isomer of [PtCl2(Th3As)2]. Crystals suitable for X-
The absorption at 352 cmꢂ1 is assigned to n(PdÃ
Clterminal) while those at lower wavenumbers are as-
signed to the bridging n(PdÃCl) stretching absorptions.
These assignments are in agreement to those obtained
for similar arsine complexes [22]. A preliminary X-ray
structural analysis of [Pd2Cl2(m-Cl)2(PEt2Th)2] shows
that the phosphine is coordinated through P atom with
no sulphur palladium interactions [23].
/
played two n(PtÃ
/
/
ray
diffraction
analysis
were
obtained
for
[PdCl2(Th3As)2] and hence, a full molecular structure
determination was conducted.
Treatment of [Pd2Cl2(m-Cl)2(Th3As)2] with Me4Sn
readily gave a binuclear methyl palladium complex
[Pd2Me2(m-Cl)2(Th3As)2]. The IR spectrum showed a
The molecular structure of [PdCl2(Th3As)2] is shown
in Fig. 1 and selected geometric parameters are collected
in the caption to the Figure. The molecule is centrosym-
metric so that the configuration of the As2Cl2 donor set
is trans. This also implies that the configuration of the
band at 330 cmꢂ1 which may be assigned to n(PdÃ
/
Cl).
The 1H NMR spectra showed a single resonance at 0.86
ppm attributable to PdÃMe protons.
Reactions of chloro-bridged binuclear palladium
complexes [Pd2X2(m-Cl)2(Th3As)2] (XꢀCl, Me) with
/
Th3As ligands, as viewed down the AsÃ
staggered. The PdÃAs bond distance is as found in
related systems [18]. The AsÃC distances in Th3As
ligand fall in the narrow range of 1.904(3)Á
and the CÃAsÃC angles lie between 101.25(12) and
103.81(13)8. These are approximately the same
/
PdÃ/As axis, is
/
/
/
dimethylpyrazole (dmpzH) in 1:2 stoichiometry in the
presence of 2 equiv. of NaOH afforded the dimethyl
pyrazolate bridged complexes [Pd2X2(m-dmpz)2-
˚
1.913(3) A
/
/
/
(Th3As)2]. The 1H NMR spectrum of the PdÃ
/
Me
dimethyl pyrazolate bridged complex exhibited a singlet
at 0.48 ppm for PdÃMe protons; the signal is shielded
compared to the parent complex. The appearence of
only one singlet for C4ÃH of the pyrazolate group (d
5.52 in PdMe and 5.37 in PdÃCl) indicates that only
˚
(1.893(3)Á
(107.73(8)Á
found in the structure of the As(V) species, Th3AsÄ
[19].
/
1.895(3) A) and significantly smaller
/
109.00(13)8), respectively compared to those
/
/O
/
The reaction of PdCl2(PhCN)2 or Na2PdCl4 with
Th3Sb in 1:2 molar ratio always resulted in decomposi-
tion leading to black insoluble powder (Found: C, 0.5;
H, 0.3%) (possibly Pd metal). No reaction is observed
/
trans isomer is formed as has been observed for the
analogous phosphine derivatives [24,25].
Reactions of chloro-bridged binuclear Pd complexes
[Pd2Me2(m-Cl)2(Th3As)2] with pyrazole (pzH) in 1:2
stoichiometry in the presence of 2 equiv. of NaOH
afforded the pyrazolate bridged complexes [Pd2Me2-
(pz)2(Th3As)2].
when [PtCl2(RCN)2] (Rꢀ
Th3Sb.
Cleavage of chloro-bridged platinum complexes
/Me or Ph) is treated with
[Pt2Cl2(m-Cl)2(PR3)2] or [Pt2(m-Cl)2(PfflC)2] (PfflCꢀ
/
But2 PCCH2Me2) with Th3As or Th3Sb in dichloro-
methane readily afforded mononuclear complexes
[PtCl2(PR3)(Th3E)] or [PtCl(PfflC)(Th3As)] as colourless
crystalline solids. Except [PtCl2(PMe2Ph)(Th3As)], they
were isolated as the cis products as revealed by the
Reaction of [Pd2Cl2(m-Cl)2(Th3As)2] with 2 equiv. of
ammonium salt of dialkyldithiophosphate NH4[S2P-
(OR)2] (Rꢀ
Et, Pri) easily afforded dithiophosphate
/
complexes [PdCl(S2P(OR)2)(Th3As)]. The 1H NMR
spectra of both the complexes showed the expected
resonances. The 31P NMR also displayed single reso-
nances (d 97.5 ppm for Et and d 101.5 ppm for Pri).
These resonances are more shielded than the parent
ligand. The IR spectra of both the complexes showed a
band of medium to strong intensity at approximately
magnitude of 1J(PtÃ
/P) which agrees well with the
reported cis derivatives [20]. In the former, resonances
attributable to another species (approximately 5% in
concentration) have been observed. They can be as-
signed to the trans product. The 1J(PtÃ
/
P) (3038 Hz) for
[PtCl(PfflC)(Th3As)] may be attributed the arsine trans
to the orthometallated phosphorous atom. The magni-
330 cmꢂ1 assignable to n(PdÃ
/
Cl). Structures of several
[PdCl(SfflS)(PR3)] complexes have been established
which show a chelated dithio ligand [26]. A similar
structure is likely for the complexes reported here.
From the foregoing, it appears that the Th3E (As, Sb)
ligands function exclusively as monodentate donors in
the systems investigated, as was usually the case for the
phosphorus analogue.
tude of 1J(PtÃ
/
P) can be compared with other complexes
neutral donor ligand) for which a
[PtCl(PfflC)(L)] (Lꢀ
/
trans configuration has been assigned [21]. Although
Th3Sb cleaves the chloro bridge in platinum complex to
give [PtCl2(PMePh2)(Th3Sb)], a similar reaction with the
palladium complex [Pd2Cl2(m-Cl)2(PMePh2)] results in
decomposition. This is in contrast to the bridge cleavage
reactions with phosphine or amine ligands.
Reaction of [PdCl2(Th3As)2] with Na2PdCl4 afforded
the chloro bridge complex [Pd2Cl2(m-Cl)2(Th3As)2]. The
IR spectrum displayed three absorptions at 268, 328 and
4. Supplementary material
Crystallographic data for the structural analysis of
[PdCl2(Th3As)2] have been deposited at the Cambridge
352 cmꢂ1 which are assigned to n(PdÃ
/Cl) absorptions.

H. Mahalakshmi et al. / Polyhedron 22 (2003) 549Á
/555
555
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Obsch. Khim, 52 (1982) 2638; [Chem Abst., 98 (1983) 72281];
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Zaslonova, Zh. Obsch. Khim, 52 (1982) 2793; [Chem Abst., 98
(1983) 89518].
Crystallographic Data Centre, CCDC No. 192486.
Copies of the information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: ꢁ44-1223-336033; e-
/
mail: deposit@ccdc.cam.ac.uk or www. http://
www.ccdc.cam.ac.uk).
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Acknowledgements
One of the authors (HM) is grateful to Department of
Atomic Energy for the award of a Senior Research
Fellowship. The authors thank Dr J.P. Mittal, Director,
Chemistry and Isotope Group and Dr P. Raj, Head,
NM & SC Division for encouragement of this work. We
are also grateful to Analytical Chemistry Division,
BARC, for carrying out the microanalysis of the
complexes.
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