Dinuclear PdII/PtIIcomplexes [M2(phosphine)n(thio-ligand)3]Cl incorporating N,S-bridged pyridine-2-thiolate and benzimidazoline-2-thiolate

Article abstract of DOI:10.1016/j.poly.2017.01.042

Equimolar reaction of [PdCl₂(dppm)] {dppm?=?bis(diphenylphosphino) methane} with pyridine-2-thione (pySH) in presence of NaOH base in aqueous ethanol formed dinuclear mixed-ligand complex, [Pd^II₂(μ-κ²:N,S-pyS)₃(μ-P,P-dppm)]Cl 1. Similarly, reaction of PdCl₂(PPh₃)₂with benzimidazoline-2-thione (bzimSH) in 1:2?M ratio in the presence of Et₃N base in acetonitrile has formed a dinuclear complex, [Pd^II₂(μ-κ²:N,S-bzimS)₂(κ¹-S-bzimS)(PPh₃)₃]Cl·2H₂O 2. Surprisingly, analogous thio-ligand, 1,3-imidazoline-2-thione (imzSH), merely formed a simple square planar complex, [Pd(κ¹-S-imzSH)₄]Cl₂·2H₂O 3. The reaction of H₂PtCl₆with pySH and dppm (1:1:1?M ratio) in the presence of Et₃N base in toluene–ethanol (1:1:: v/v) mixture also formed a mixed-ligand dinuclear complex [Pt^II₂(μ-κ²:N,S-pyS)₃(μ-P,P-dppm)]Cl similar to 1. All these complexes have been characterized using analytical data, IR, NMR (¹H,³¹P), UV–vis, fluorescence, ESI-mass and single crystal X-ray crystallographic techniques. The anionic thio-ligands are N,S-bridged in complexes 1 and 4, both N,S-bridged and κ¹-S bonded in 2 and as neutral κ¹-S bonded in 3. There are short M?M contacts in 1 and 4 (1: 2.7249(5) ? 4: 2.7350(8) ?). Complexes 1, 3 and 4 showed intense fluorescence. ESI mass spectral studies of 1, 3 and 4 revealed the formation of molecular ions and other species.

Full text of DOI:10.1016/j.poly.2017.01.042

Accepted Manuscript
II
II
Dinuclear Pd /Pt complexes [M (phosphine) (thio-ligand) ]Cl incorporating
2
n
3
N, S-bridged pyridine-2-thiolate and benzimidazoline-2-thiolate
Tarlok S. Lobana, Amanpreet K. Sandhu, Rakesh K. Mahajan, Geeta Hundal,
Sushil K. Gupta, Ray J. Butcher, Alfonso Castineiras
PII:
S0277-5387(17)30079-7
DOI:
http://dx.doi.org/10.1016/j.poly.2017.01.042
POLY 12446
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
2 December 2016
25 January 2017
25 January 2017
Please cite this article as: T.S. Lobana, A.K. Sandhu, R.K. Mahajan, G. Hundal, S.K. Gupta, R.J. Butcher, A.
II
II
Castineiras, Dinuclear Pd /Pt complexes [M (phosphine) (thio-ligand) ]Cl incorporating N, S-bridged pyridine-2-
2
n
3
thiolate and benzimidazoline-2-thiolate, Polyhedron (2017), doi: http://dx.doi.org/10.1016/j.poly.2017.01.042
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II
II
Dinuclear Pd /Pt
incorporating N, S-bridged pyridine-2-thiolate and benzimidazoline-
-thiolate
complexes [M (phosphine) (thio-ligand) ]Cl
2
n
3
2
a
a
a
a
Tarlok S. Lobana,* Amanpreet K. Sandhu, Rakesh K. Mahajan, Geeta Hundal, Sushil K.
b
b
c
Gupta, Ray J. Butcher, Alfonso Castineiras
a
Department of Chemistry, Guru Nanak Dev University, Amritsar-143 005, India
Department of Chemistry, Howard University, 525 College Street NW, Washington, DC 20059, USA
Departamento de Quimica Inorganica, Facultad de Farmacia, Universidad de Santiago,
b
c
Santiago/Spain.
Email: tarlokslobana@yahoo.co.in;
Fax: 91-183-2258820 ; Telephone : 91-183-2258802 ext. 3195
ABSTRACT
Equimolar reaction of [PdCl
2
(dppm)] {dppm = bis(diphenylphosphino) methane} with pyridine-
2
-thione (pySH) in presence of NaOH base in aqueous ethanol formed dinuclear mixed- ligand
II
2
complex, [Pd
2
(µ-κ :N,S-pyS)
3
(µ-P,P-dppm)]Cl 1. Similarly, reaction of PdCl
2
(PPh
N base in
(κ -S-bzimS)(PPh ]Cl·
3
) with
2
benzimidazoline-2-thione (bzimSH) in 1 : 2 molar ratio in the presence of Et
3
II
2
1
acetonitrile has formed a dinuclear complex, [Pd
2
(µ-κ :N,S-bzimS)
2
)
3 3
2
H
2
O 2. Surprisingly, analogous thio-ligand, 1,3-imidazoline-2-thione (imzSH), merely formed
1
a simple square planar complex, [Pd(κ -S-imzSH)
4
]Cl
2
·2H
2
O 3. The reaction of H
2
PtCl with
6
pySH and dppm (1:1:1 molar ratio) in the presence of Et
3
N base in toluene –ethanol (1 :1 : : v/v)
II
2
mixture also formed a mixed-ligand dinuclear complex [Pt
2
(µ-κ :N,S-pyS)
3
(µ-P,P-dppm)]Cl
1
similar to 1. All these complexes have been characterized using analytical data, IR, NMR ( H,
3
1
P), UV-visible, fluorescence, ESI-mass and single crystal x-ray crystallographic techniques.
1
The anionic thio-ligands are N,S-bridged in complexes 1 and 4, both N,S-bridged and κ -S
1
bonded in 2 and as neutral κ -S bonded in 3. There are short M···M contacts in 1 and 4 (1:
2
.7249(5) Ǻ; 4: 2.7350(8) Ǻ). Complexes 1, 3 and 4 showed intense fluorescence. ESI mass
spectral studies of 1, 3 and 4 revealed the formation of molecular ions and other species.
1

Keywords: Pyridine-2-thione, 1, 3-benzimidazoline-2-thione, 1, 3- imidazoline-2-
thione, palladium(II) chloride, platinum.
1
. Introduction
Heterocyclic thioamides incorporating N, S donor atoms constitute an important class of thio-
ligands whose coordination chemistry has been in focus of several research workers [1-29].
These thio ligands have shown interesting coordination variability which has resulted in the
formation of a diverse range of coordination compounds: mononuclear, dinuclear, oligomers and
polymers [10-12, 14, 18, 22-24, 27]. Another interest in the chemistry of heterocyclic thioamides
is linked to their biological applications such as anticancer [30-34], antimicrobial/ antibacterial
[
35, 36] and catalysis [37, 38].
H
N
S
HN
NH
N
H
S
N
H
S
pySH
bzimSH
imzSH
S
N
N
HN
HN
N-Me
N
H
S
N
H
N
S
pymSH
purSH2
mimzSH
Chart 1. Molecular structures of thio-ligands
II
II / III
The reactions of Pd /Pt
with a series of heterocyclic thioamides (Chart 1) have yielded
a variety of complexes with and without co-ligands. For example, without co-ligands, Pd/ Pt
II
1
have formed mononuclear and dinuclear complexes of the type: [Pt (κ -S-pySH)
4
]Cl
2
[15],
II
1
II
1
II
2
[
Pd (κ -S-mimzSH)
4
]Cl
2
·2H
2
O [39], [Pt (κ -S-mimzSH)
4
]Cl
2
[40], [Pd
2
(µ-κ :N,S-pyS)
4
] [41,
III
2
4
2] and [Pt
2
Cl
2
(µ- κ : N,S-pyS) ] [43]. The co-ligands used are mono- and di-tertiary
4
II
II
phosphines and a brief list of Pd / Pt complexes with pyridine-2-thione (pySH), pyrimidine-2-
thione (pymSH) and purine-6-thione (purSH
2
) (Chart 1) is listed here. Two types of complexes
)] [44], cis-[M(L )(P, P-L)] {M = Pd, Pt;
2
are formed: (a) mononuclear [PdCl(κ :N,S-pyS)(PPh
3
n
2

1
1
2
L
n
= 2(κ :S-pyS), 2(κ :S-pymS), κ -N,S-puS; P, P-L = Ph
2
P-(CH
2
)
n
-PPh
2
; n = 1, dppm; 2, dppe;
1
3
, dppp; 4, dppb; Ph
2
P-CH=CH-PPh
2
, dppen} [12, 14, 21, 45], [Pt(κ :S-pyS)
2
(PPh
3
)
2
] [13],
1
2
2
[
M(κ :S-pymS)
pyS)(PPh ](PF
dppm)] [14], [Pd
Pd; L = pyS, pymS) [48, 49].
2
(PPh
3
)
2
] (M = Pd, Pt) [45], [Pd(κ :N,S-pymS)(PPh
3
)
2
2
](ClO
4
) [46], [Pt(κ :N,S-
2
1
3
)
2
6
) [47], and (b) dinuclear, [Pd
2
(µ- κ :N,S-pyS)(µ-κ :S-pyS)(κ :S-pyS)
2
(µ-P,P-
] (M =
2
2
2
2
(µ-κ :N,S-pyS)
3
(κ :P,P-dppm)]Cl [14] and [M
2
Cl
2
(µ- κ :N,S-L)
2
3 2
(PMe )
From this laboratory, reactions of [M(diphosphine)Cl
P-CH -CH -PPh , dppe; Ph P-CH=CH-PPh , dppen) with pyridine-2-thione in 1 : 2 molar
ratio gave P, P- chelated square planar complexes, cis-M(κ -P,P)(κ -S-L)
a curiosity, it was desired to prepare Pd/Pt complexes similar to 'A' type by reacting
M(PPh Cl with 1, 3-benzimidazoline-2-thione (bzimSH) and 1, 3- imidazoline-2-thione
imzSH). The second curiosity was to react a metal salt (MCl ) with pySH and dppm in 1 : 1 : 1
2
] (M = Pd, Pt; diphosphine =
Ph
2
2
2
2
2
2
2
1
2
(A) (Chart 2) [12]. As
3
)
2
2
(
2
molar ratio so as to obtain mixed-ligand complexes of type, [M
2
(pyS)
2
(dppm)
2
]Cl (B, M = Pd/
2
Pt). The results of these reactions are reported in this paper.
P
M
N
P
M
S
N
S
P
S
N
N
S
N
=
M
-
Cl2
N
S
S
P
P
P
=
=
dppe, dppen (A)
dppm (B)
P
P
A
B
P
P
Chart 2
2
. Experimental
.1 Material and Techniques
2
Pyridine-2-thione, benzimidazoline-2-thione, 1,3-imidazoline-2-thione, 1,1-bis(diphenylphos -
phino)methane(dppm), PPh , PdCl and H PtCl were procured from Sigma–Aldrich Ltd. The
precursors, namely, PdCl (PPh and PdCl (dppm) were prepared by the addition of a respective
phosphines to a solution of PdCl in acetonitrile followed by refluxing for 5-6 h [50]. The
melting points were determined with a Gallenkamp electrically heated apparatus. The IR spectra
3
2
2
6
2
3
)
2
2
2
-1
were recorded using KBr pellets on Varian 660 FT IR Spectrometer in the 4000-200 cm range.
3

1
The H NMR spectra were recorded in CDCl
3
/ dmso-d
6
using a Bruker Avance II 400 NMR and
Bruker Avance 500 NMR spectrometer at 400 MHz and 500 MHz respectively using TMS as an
3
1
internal reference. The P NMR spectra were recorded in CDCl
3
with Bruker Avance II 400
NMR at 161.97 MHz spectrometer with o-phosphoric acid as the external reference.
2
.2. Synthesis of complexes
II
2
2
.2.1. Synthesis of , [Pd
2
(µ-κ :N,S-pyS) (µ-P,P-dppm)]Cl (1)
3
To the solid thio-ligand pySH (0.01g, 0.090 mmol) placed in round bottom flask was added a
solution of sodium hydroxide (NaOH) (0.004g, 0.09 mmol) in distilled water (2 mL) which
formed a clear light yellow solution. To this solution was added a suspension of PdCl
2
(dppm)
(
0.05g, 0.089 mmol) in ethanol (15 mL) and the contents were refluxed for 10 h. The colour of
the reaction mixture became dark orange and was filtered. The filtrate was evaporated using
rotary evaporator until a solid was obtained. It was treated with acetone (10 mL) which dissolved
the complex leaving behind NaCl. The acetone solution was filtered to remove NaCl. To the
acetone extract was added 4 mL of dichloromethane-methanol (1 : 1 v/v) mixture and left to
evaporate at room temperature. The orange colored crystals of compound 1 were formed in a
period of 20-25 days (65 %; m.p 178-180 ˚C). Anal. Calc. for C40
H34ClN
3
P
2
Pd
2
S
3
(963.07) : C,
-1
4
9.84; H, 3.53; N, 4.36. Found: C, 49.78; H, 3.92; N, 4.48 %. IR bands(KBr, cm ): ν(C-H) 3049
m, 2924 m, 2862 m; ν(C-C) + ν(C-N) + δ(C-H), 1591 s, 1437 s, 1268 w, 1189 s; ν(C-S), 1108s;
1
ν(P-CPh), 1040 w; 741 s, ν(Pd-N), 504 s. H NMR data (CDCl
3
, δ, ppm, J, Hz): 9.42 (d, 1H, J =
6
6
3
6
1
0 Hz, H , pyS), 8.69 (d, 1H, J = 5 Hz, H , pyS), 8.50 (m, 2H, H , pyS), 8.24 (d, J, 5 Hz, 1H, H ,
3
4
4
pyS), 8.15 (m, 2H, H , H , pyS), 7.69 (m, 8H, o-H, Ph), 7.37 (m, 4H, p-H, Ph), 7.13 (m, 2H, H ,
5
5
pyS), 6.96 (m, 9H, H , pyS, m-H, Ph), 6.63 (m, 2H, H , pyS), 4.41 (m, 1H, -CH -, dppm), 4.24
2
3
1
(
m, 1H, -CH
2
-, dppm). P NMR data (CDCl
3
, δ ppm): δ
P
= 32.46 ppm, JP-P, 61.5 Hz; δ
P
= 28.02
-1
-1
-4
3
ppm, JP-P, 60 Hz. UV-vis. data, DMSO, λmax /nm, ε /Lmol cm : [10 M] 422 (3.57 x 10 ), 311
4
4
-5
em
ex
(
1.92 x 10 ), 273 (5.00 x 10 ). Fluorescence data, DMSO : [10 M] (λmax = 442 nm, λmax =
3
22 nm).
II
2
1
2
.2.2. Synthesis of [Pd
2
(µ-κ :N,S-bzimS)
2
(κ -S-bzimS)(PPh
3
)
3
2
]Cl·2H O (2)
To the solution of PdCl
2
(PPh
3
)
2
(0.050 g, 0.07 mmol) dissolved in 10 mL of CH
3
CN, bzimSH
(
0.021 g, 0.14 mmol) was added followed by Et
3
N base (0.5 mL). The solution became turbid
4

and yellowish orange in color. Then the refluxing was done for 6 h. The colour of the reaction
mixture became orange and was filtered. The filtrate was evaporated using rotary evaporator
until a solid was obtained. It was treated with acetone which dissolved the complex leaving
+
-
+
-
behind Et
3
NH Cl , white solid. The acetone solution was filtered to remove Et NH Cl . To it was
3
added 4 mL dichloromethane-methanol (1 : 1, v/v) mixture and left to evaporate at room
temperature. The orange colored crystals of compound 2 were formed in a period of 10-15 days
(
67 %, m.p 218-220 ˚C). Anal. Calc. for C75
H61ClN
6
P
3
Pd
2
S
3
·2H O(1519.67 ) : C, 59.22; H, 4.01;
2
-1
N, 5.53. Found: C, 59.80; H, 4.36; N, 5.52 %. IR bands(KBr, cm ): ν(O-H), 3393 m(b); ν(C-H),
3
1
051 m, 2963 w; ν(C-C) + ν(C-N) + δ(C-H), 1618 s, 1479 m, 1433 s, 1391 s, 1263 m, 1226 w;,
182 w; ν(P-CPh), 1096 s; ν(C-S) 1022 s; 802 m, 741 s, 691 s, ν(Pd-N), 523 s; 422 w. ESI Mass
could not be recorded due to poor solubility.
1
2
.2.1. Synthesis of [Pd(κ : S-imzSH)
4
]Cl
2
.2H
2
O (3)
To a suspension of PdCl
2
(PPh
3
)
2
(0.05, 0.071 mmol) in 10 ml of CH
3
CN, imzSH (0.014 g, 0.14
mmol) was added in presence of Et
3
N base (0.5 mL). The solution became turbid orange colored
and the contents were refluxed for 5-6 h. The filtrate was evaporated using rotary evaporator
until a solid was obtained. The solid obtained was dissolved in methanol (10 mL) and to this was
added CH
crystals of compound 3 were obtained after a period of 10 days (40 %, m.p 260-262 ˚C). Anal.
Calc. for C12 PdS (613.90): C, 23.46; H, 3.26; N, 18.24. Found: C, 23.20; H, 3.42; N,
8.40 %. IR bands(KBr, cm ): ν(O-H), 3447 m, 3384 m; ν(N-H), 3308 m; ν(C-H), 3081 s, 3016
3
CN (2 mL) and the mixture allowed to evaporate at room temperature. The dark red
H
20Cl
2
N
8
O
2
4
-1
1
w, 2968 m, 2938 m, 2847 s; ν(C-C) + ν(C-N) + δ(C-H), 1581 s, 1479 s, 1401 s, 1284 w, 1232 w;
1
ν(C=S), 1119 m; 1058 m, 951 w, 910 m, 815 m, 740 s, 665 m, 497 m. H NMR data (CDCl
3
+
4
,5
dmso-d
6
(8 : 2), δ, ppm, J, Hz): 11.93 (s, NH, 1H, imzSH), 7.25 (s, 2H, C H, imzSH). UV-vis.
-1
-1
-4
3
4
data, DMSO, λmax /nm, ε /Lmol cm : [10 M] 441 (2.20 x 10 ), 340 (1.41 x 10 ), 265 (3.08 x
4
-4
em
ex
1
0 ). Fluorescence data, DMSO : [10 M] (λmax = 442 nm, λmax = 342 nm).
2
2
2
.2.1. Synthesis of [Pt
2
(µ- κ :N, S-pyS) (κ :P,P-dppm)]Cl (4)
3
To the solid pySH (0.013g, 0.12 mmol) suspended in toluene (5 mL) in a round bottom flask was
added a solution of platinic acid, H PtCl (0.05 g, 0.12 mmol) in ethanol (15 mL) in presence of
Et N base (2 mL). The contents were stirred for 2 h until turbidity appeared and to this was
2
6
3
5

added solid dppm (0.046 g, 0.12 mmol). The clear orange color solution formed was stirred
+
-
overnight and Et
3
NH Cl formed was filtered off, and the filtrate was allowed to crystallize at
C40 H34 Cl N3 P2 Pt2 S3 room temperature. The orange crystals of compound 4 were
formed in a period of 15-20 days (68 %, m.p 197-199 ˚C). Anal. Calc. for C40
H
34ClN
3
P
2
Pt
2
S
3
-
(
1140.43): C, 42.09; H, 2.98; N, 3.68. Found: C, 42.50; H, 2.62; N, 3.56 %. IR bands(KBr, cm
1
)
: ν(O-H), 3453 s; ν(C-H), 3051 w, 2926 w, 2855w; ν(C-C) + ν(C-N) + δ(C-H), 1663 w, 1638
w, 1591 s, 1545 w, 1483 w, 1452 s, 1435 m, 1408 m, 1269 w, 1159 w; ν(C-S), 1136 w; ν(P-CPh),
1
1
098 m; 1053 w, 1020 w, 997 w, 739 s, 718 s, 696 s, 660 w, ν(Pt-N), 530 m; 486 w, 428 w. H
6
6
NMR data (CDCl
3
, δ, ppm, J, Hz): 9.13 (d, 1H, J = 5 Hz, H , pyS), 8.43 (d, 1H, J = 10 Hz, H ,
6
3
3
4
pyS), 8.36 (m, 3H, H , H , pyS), 8.21 (m, 2H, H , H , pyS), 7.70 (m, 8H, o-H, Ph), 7.42 (m, 2H,
4
5
5
H , pyS), 7.14 (m, 5H, p-H, Ph, H , pyS), 6.91 (m, 8H, m-H, Ph), 6.63 (t, 1H, J, 7.5, Hz, H ,
5
pyS), 6.56 (t, 1H, J = 7.5 Hz, H , pyS), 4.46 (m, 1H, -CH
2
-, dppm), 4.33 (m, 1H, -CH
2
-, dppm).
3
1
P NMR data (CDCl
3
, δ ppm): δ
P
= 12.70 ppm, JP-P, 38.87 Hz; δ = 8.29 ppm, JP-P, 38.87 Hz.
P
-
1
-1
-5
-4
3
4
UV-vis. data, DMSO, λmax /nm, ε /Lmol cm : [10 M] 354 (4.29 x 10 ), 302 (1.29 x 10 ), 273
4
em
ex
(
1.79 x 10 ). Fluorescence data, DMSO : [10 M] (λmax = 439 nm, λmax = 358 nm).
2
.3 X-ray crystallography
The single crystals of compounds (1-3) were mounted on glass fibers and data were collected
using Bruker CCD SMART 1000 (1), Xcalibur and Ruby, Gemini (2, 3) diffractometer,
equipped with a graphite monochromator and Mo–Kα radiation (λ = 0.71073 Å; 1-3). The unit
cell dimensions and intensity data were measured at 100(2) for 1, 173(2) for 2 and 123(2) for 3
respectively. The data were processed with Bruker SMART (data collection, cell refinement) 1,
CrysAlisPro (data collection, cell refinement, data reduction) (2, 3) [51], Bruker SAINT (data
reduction) (1) [52]. The structures were solved by direct methods using the program SHELXS-97
2
[
[
53] (1-3) [54] and refined by full-matrix least-squares techniques against F using SHELXL-97
55]. The data for complex 4 were collected on Bruker APEX-II CCD at room temperature. The
crystal quality was very poor and a number of crystals were tried before this data set was taken
and was the best out of the lot. The structure was solved by direct methods using SIR-92[54] and
2
it was refined by least square methods on F using SHELXL-97 program[53]. All atoms were
refined anisotropically. Hydrogen were calculated geometrically. The refinement showed a
disordered Cl atom which was resolved at two positions using PART command and refining its
6

sof and thermal parameters as free variables. The final difference Fourier map still shows a few,
3
small residual electron density peaks of 2.5 to 1.0 e Å which are lying very close to heavy atoms
like Pt, S and P and could not be modelled any further. These could be due to series termination
error or due to underlying unresolved disorder in certain atoms but as such there is no missing
atomic entity. The data quality is poor, is evident from the ratio of unique to observed reflections
being only 46%. The unit cell shows large solvent accessible voids due to packing forces only.
The cif shows certain B and C level alerts due to these reasons. The crystallographic data are
given in (Table 1) and bond lengths and angles are placed in Table 2.
3
. Results and Discussion
3
.1 Comments on the synthesis and IR spectroscopy
When PdCl
2
(dppm) was reacted with pyridine-2-thione (pySH) in 1 : 2 molar ratio in
2
1
aqueous NaOH in ethanol to obtain the expected complex, cis-Pd(κ :P,P-dppm)(κ :S-pyS)
2
(
similar to A, Chart 2) [12], no crystalline product could be isolated. On repeating this reaction in
1
: 1 molar ratio under similar experimental conditions, it gave a crystalline product with unusual
empirical composition, Pd
2
(pyS) (dppm)·Cl. The single crystal x-ray structure determination of
3
II
2
this product revealed the formation of a mixed-ligand dinuclear complex, [Pd (µ-κ :N,S-
2
2
pyS)
3
(κ :P,P-dppm)]Cl 1. Equimolar reaction of platinic acid (H
2
PtCl
6
) with pyridine-2-thione in
toluene-ethanol mixture using Et
3
N as base followed by addition of one mole of dppm has also
I,II
2
formed a mixed-ligand dinuclear complex [Pt
2
(µ-κ :N,S-pyS)
to Pt as observed earlier [45]. When PdCl
with benzimidazoline-2-thione (bzimSH) in 1 : 1 or 1 : 2 molar ratios using the procedure
3
(µ-P,P-dppm)]Cl 4. Ethanol is
IV
II
known to reduce Pt of H
2
PtCl
6
2
(dppm) was reacted
2
1
adopted for 1, no product similar to 1 or cis-M(κ :P,P-dppm)(κ :S-L)
2
(A, Chart 2) could be
(PPh in 2 :
N base in acetonitrile solvent, it has yielded mixed
established [12]. However, when benzimidazoline-2-thione was reacted with PdCl
2
)
3 2
1
molar ratio (L : M) in the presence of Et
3
II
2
1
ligand complex, [Pd
2
(µ-κ :N,S-bzimS)
2
(κ -S-bzimS)(PPh
3
)
3
]Cl·2H O 2, analogous to 1. A
2
related ligand 6-methyl-1H-benzo[d]imidazole-2-thione(L) with Pd(II) has yielded a simple
1
square planar complex, [PdCl
2
(κ :S-L)(PPh
3
)][56] Similarly, reaction of PdCl
2
(PPh
3
2
) with two
moles of 1,3-imidazoline-2-thione in acetonitrile in presence of Et
3
N base did not form the
1
expected dimer similar to 2, rather it has formed a square planar monomer, [Pd(κ :S-
7

imzSH
2
)
4
]Cl
2
·2H
2
O 3 involving de-ligation of PPh . The difference in bonding of thio-ligands in
3
complex 2 relative to complexes 1 and 4 is probably due to the higher steric requirement of
benzimidazoline-2-thione which has not favored multiple bridging between two metals. Chart 3
shows bonding view of complexes synthesized.
The IR spectral data of complexes are given in the experimental section and that of the
ligands is placed in supporting information. The IR spectrum of free pySH ligand shows a ν(N-
-1
H) band at 3161 cm which is absent in its complexes 1 and 4, and it showed deprotonation of
-
-1
the thio-ligand (pySH to pyS ). Similarly, the free pySH ligand showed a band at 1138 cm due
-1
to ν(C=S) which is shifted to 1108, 1119 (1) and 1136 (4) cm in respective complexes. The
-1
ν(N-H) band of free bzimSH at 3153 cm is absent in its complex 2. The ν(C=S) band at 1179
-1
-1
cm of free bzimSH is shifted to 1022 cm in complex 2. In complex 3, the ν(N-H) band
-1
appeared at 3308 cm which is in the high energy region relative to the uncoordinated ligand
-1
-1
(
imzSH, 3130 cm ). The characteristic ν(C-S) band in complex 3 appears at 1119 cm and it
-1
remains unchanged relative to the free thio-ligand (1120 cm ). The ν(P-CPh) peaks in the range,
-1
1
040-1098 cm , reveal the presence of coordinated phosphines in complexes. The IR spectra of
-1
complexes 2, 3 and 4 have shown ν(O-H) bands at 3393, 3384-3447 and 3453 cm respectively
which confirm the presence of the non-bonded water molecules in complexes.
8

P
P
S
N
PPh3
Ph P
3
N
S
N
=
II
Pd
S
II
Pd
II
Pd
Cl
Cl
N
N
II
N
S
N
Pd
S
S
Ph P
3
S
N
H
S
2
N
2
1
P
P
NH
HN
S
II
Pt
=
Ph PCH PPh
2
P
P
2
2
Cl
S
S
N
N
H
N
II
N
1, 4
H
Pt
N
Pd
S
H
N
Cl2 .
S
H
N
S
S
NH
HN
3
4
Chart 3. A view of bonding pattern of complexes synthesized.
3
.2. Molecular structures
Table 1 gives crystal data of compounds 1-4, while bond parameters are placed in Table 2.
Complexes 1 and 2 formed monoclinic clinic crystals in space groups: C2/c and P2 /c
respectively, while complexes 3 and 4 formed triclinic (3) or trigonal(4) crystals in space groups
1
II
2
P-1 and P-3c1 respectively. Molecular structure of complex [Pd
2
(µ-κ :N, S-pyS) (dppm)]Cl 1
3
-
is shown in Fig. 1. It has three anionic pyS and one neutral dppm ligands which make N, S or P,
P bridges between two metals. Each palladium metal is in divalent oxidation state and chloride
II
2
+
is outside the coordination sphere of the cation [Pd
2
(µ-κ :N, S-pyS) (dppm)] . The Pd1 atom is
3
bonded to two nitrogen atoms at Pd-N distances of 2.131(3), 2.075(3), one sulfur atom at Pd-S
distance of 2.2901(10) and one phosphorus atom at Pd-P distance of 2.2614(11) Å (Table 2). The
Pd2 atom is bonded to one nitrogen atom at Pd-N distance of 2.081(3), two sulfur atoms at Pd-S
distances of 2.3052(10), 2.3517(11) and one phosphorus atom at Pd-P distance of 2.2843(11) Å.
Thus the two metal centers have different coordination cores: PdN
2
PS and PdNPS . The trans
2
bond angles around the Pd1 and Pd2 metal centers, namely, [N(31)-Pd(1)-S(11), 175.77(10)°,
P(1)-Pd(1)-N(21) 173.29(9)°, S(31)-Pd(2)-N(11) 175.26(9)° and S(21)-Pd(2)-P(2) 175.84(4)°]
deviate from linearity and it confirms that each of palladium centers has slightly distorted square
9

planar geometry. The Pd-S, Pd-N and Pd-P bond distances are similar to those found in reported
2
2
complexes, [PdCl(µ-κ : N,S-pymS)(PMe
3
)]
2
[48] and [PdCl(µ- κ :N,S-pyS)(PMe
3
2
)] [49]. The
Pd-Pd distance of 2.7249(5) Å is less than the sum of van der Waals radius of palladium metal
atom (3.20 Å) which suggests that there is a weak metal-metal interaction [57].
2
2
Fig. 1. ORTEP diagram of the molecule 1 [Pd
2
(µ- κ :N, S-pyS) (κ :P,P-dppm)]Cl at at 30%
3
probability; hydrogens have been removed for clarity.
II
2
The coordination pattern and molecular structure of dinuclear complex, [Pt (µ-κ : N, S-
2
2
pyS)
3
(κ :P,P-dppm)]Cl 4 is similar to that of complex 1(Fig. 2). The Pt-S, Pt-N and Pt-P bond
2
distances are similar to those found in reported complexes, [Pt
2
(µ-κ : N,S-pyS)
4
]Cl [43] and
2
2
[
Pt(en)
2
(µ- κ : N,S-pyS)
2
]Cl
2
·3H O {en = ethylene diamine} [58]. The trans bond angles around
2
the Pt1 and Pt2 metal centers deviate from linearity and it suggests that both the platinum metal
centers have slightly distorted square planar geometries. The Pt-Pt distance of 2.7349(8) Å is less
1
0

than the sum of van der Waals radius of platinum metal atoms (3.40-3.60 Å) which suggests that
there is a weak metal-metal bonding [57]
II
2
2
Fig. 2. ORTEP diagram of the molecule [Pt
2
(µ- κ : N, S-pyS)
3
(κ :P,P-dppm)]Cl 4, at 30%
probability. Hydrogens have been removed for clarity.
2
1
The bonding pattern of complex [Pd
2
(µ- κ : N,S-bzimS)
2
(κ : S-bzimS) (PPh
3
)
3
]Cl· 2H O 2
2
is different from that of complex 1 due to different coordination modes adopted by
-
benzimidazoline-2-thiolate anion (Fig.3). Here three anionic (bzimS ) and three PPh
3
ligands
coordinate to two metal centers and thio-ligands ligands are present in two different co-
ordination modes: one of them is terminally S-bonded and other two thio-ligands are N,S-
bridging. The Pd1 is bonded to one nitrogen atom at Pd-N distance of 2.058(3), one sulfur atom
1
1

at Pd-S distance of 2.3779(11) and two phosphorus atoms at Pd-P distances of 2.2992(12) and
.3092(11) Å. The Pd2 is bonded to one nitrogen atom at Pd-N distance of 2.052(4), two sulfur
atoms at Pd-S distances of 2.3669(11), 2.3140(12) and one phosphorus atom at Pd-P distance of
.2744(11) Å. Thus two metal centers have different coordination cores: PdNP S and PdNPS
2
2
2
2
.
This complex 2 has two µ-N,S bridging ligands with long Pd-Pd distance (4.371 Å) while
complex 1 has three µ-N,S bridging and one P,P-bridging ligands with short Pd-Pd distance of
o
2
.7249(5) Å. The trans bond angles around metal centers fall in the range, 172 – 175
(
approximately) (see Table 2) which deviate from linearity and hence the geometry around each
metal center is distorted square planar similar to that observed in complex 1.
1
2

2
1
+
Fig. 3. ORTEP diagram of [Pd
2
(µ-κ :N,S-bzimS)
2
(κ :S-bzimS)(PPh
3
) ] cation of 2 at 30%
3
probability; anion and hydrogens have been removed for clarity.
1
Finally the molecular structure of complex [Pd(κ :S-imzSH)
4
]Cl
2
·2H O 3 shown in Fig
2
4
is different from other three dinuclear complexes. Here Pd is coordinated to four sulfur atoms
of neutral imidazoline-2-thione ligands. The trans S-Pd-S bond angles are 180° each with S1-Pd-
o
S2 angles of 85.440(16) and 94.560(16) and it suggests nearly square planar geometry arund
the metal center. The Pd-S distances of 2.3305(4) and 2.3333(4) Å are very similar to the values,
1
2
.336(2) and 2.327(1) Å reported for analogous complex, [Pd(κ :S-mimzSH)
4
]Cl
2
.2H O {
2
mimzSH = 1-methylimidazoline-2-thione} [39].
1
2+
Fig. 4. ORTEP diagram of molecule [Pd(κ :S-imzSH)
4
] 3 at 30% probability; chloride and
water omitted for clarity
1
3

Table 1
Crystallographic data for complexes 1–4.
1
2
3
4
Empirical
formula
M
C
40
H
34ClN
3
P
2
Pd
2
S
3
C
75
H
65ClN
6
P
3
O
2
Pd
2
S
3
C
12
H
20Cl
2
N
8 2
O Pd S
4
C
40
H
34ClN
3
P
2
Pt
S
2 3
963.07
1518.67
613.90
1140.46
T /K
100 (2)
173(2)
123(2)
293(2)
Crystal
system
Monoclinic
C 2/c
Monoclinic
triclinic
Trigonal
Space
group
P 2
1
/c
P -1
P -3c1
a(Å)
b(Å)
c(Å)
17.2872(13)
15.7441(12)
32.164(2)
12.8539(6)
19.0643(9)
28.5138(9)
8.0760(5)
8.2064(5)
32.257(4)
32.257(5)
19.126(6)
10.2050(6)
α (º)
β (º)
90.00
90.00
68.311(5)
80.785(5)
90.00
90.00
93.071(8)
96.904(4)
γ (º)
90.00
90.00
71.528(6)
595.36(6)
120.00
3
V(Å )
8741.5 (11)
6936.7(5)
17235(8)
Z
8
4
1
12
1
4

D
calcd
1.464
1.454
1.712
1.319
-
3
(
g.cm )
-
1
µ (mm )
1.131
3880
0.767
3096
1.380
308
5.099
6552
F(000)
Reflections 37294
collected
56438
7208
103125
Unique
8525
23285
3918
14727
reflections
(
R
int, 0.0293)
(Rint, 0.0636)
23285/916/ 823
(Rint, 0.0246)
3918/ 0/ 141
(Rint, 0.1138)
14727/ 0/ 465
Data/
8525/ 0/ 469
restraints /
parameters
Reflens.wit 7035
14056
3315
6753
h [I>2σ(I)]
R
indices R
I>2σ(I)]
1
= 0.0392
= 0.1025
0.0690
0.1487
0.0267
0.0685
0.1622
[
wR
2
0
.0573
0.0353
.0592
R
indices R1 = 0.0510
0.1243
0.1781
0.1944
0.2324
(all data)
wR =0.1077
2
0
Largest
2.017 and
1.498 and
0.401 and
2.563 and
-1.501 e.Å
diff. Peak
and hole
-3
-3
-3
-3
-0.433 e.Å
-0.632 e.Å
-1.561 e.Å
1
5

Table 2
Important bond lengths (Å) and angles (°) of complexes 1–4
Compound 1
Pd1–N31
2.075(3)
Pd2–N11
2.081(3)
Pd1–N21
2.131(3)
Pd2–P(2)
2.2843(11)
2.3052(10)
2.3517(11)
1.750(4)
Pd1–P1
2.2614(11)
2.2901(10)
2.7249(5)
1.752(4)
Pd2–S31
Pd1–S11
Pd2–S21
Pd1–Pd2
S21–C21
S11–C11
S31–C31
1.755(5)
N21–Pd1–P1
N31–Pd1–S11
N11–Pd2–S31
P2–Pd2–S21
N11–Pd2–P2
S31–Pd2–S21
Compound 2
Pd1–N21
173.29(9)
175.77(10)
175.26(9)
175.84(4)
94.73(9)
N21–Pd1–S11
P1–Pd1–S11
N31–Pd1–N21
N31–Pd1–P1
P2–Pd2–S31
N11–Pd2–S21
88.54(9)
85.23(4)
92.54(13)
93.86(10) .
86.83(4)
89.09(4)
89.40(9)
2.058(3)
Pd2–S3
Pd2–S2
S1–C11
2.3140(12)
2.3669(11)
1.735(5)
Pd1–P2
2.3092(11)
2.2992(12)
Pd1–P1
1
6

Pd1–S1
2.3774(11)
2.052(4)
S2–C21
S3–C31
1.728(5)
1.713(5)
Pd2–N11
Pd2–P3
2.2744(11)
172.57(9)
174.16(4)
175.08(10)
174.84(4)
91.36(9)
N21–Pd1–P1
P2–Pd1–S1
N11–Pd2–S3
P3–Pd2–S2
N11–Pd2–P3
N11–Pd2–S2
Compound 3
Pd–S1
P1–Pd1–S1
N21–Pd1–S1
P1–Pd1–P2
N21–Pd1–P2
S3–Pd2–S2
P3–Pd2–S3
83.99(4)
89.74(10)
97.78(4)
88.84(10)
87.32(4)
87.51(4)
93.80(9)
a
2.3305(4)
2.3333(4)
S1–C11
S2–C21
1.7331(17)
1.7223(18)
Pd–S2
S1–Pd–S1
180.00
S1–Pd–S2
85.440(16)
S1–Pd–S2
94.560(16)
Compound 4
Pt1- N11
2.045(9)
2.255(3)
2.353(4)
Pt2-N21
Pt2–N31
Pt2–P1
2.093(13)
2.072(11)
2.239(4)
2.295(4)
Pt1–P2
Pt1–S21
Pt1–S31
2.302(3)
Pt2–S11
1
7

Pt1–Pt2
2.7349(8)
1.737(14)
88.61(14)
C21–S21
1.714(17)
1.766(17)
176.8(3)
C11–S11
P1–Pt2–S11
C31–S31
N11–Pt1–S31
N21–Pt2–S11
88.9(4)
P2–Pt1–S21
178.23(13)
N31–Pt2–P1
N31–Pt2–S11
92.5(5)
P2–Pt1–S31
N11–Pt1–P2
N11–Pt1–S21
S31–Pt1–S21
88.05(12)
92.3(3)
177.1(3)
90.1(5)
N31–Pt2–N21
N21–Pt2–P1
a
89.3(3)
176.7(4)
90.43(13)
Symmetry operators used: -x, -y, -z
3
.3 Electronic absorption/ emission and NMR spectroscopy
Complexes 1, 3 and 4 have shown weak to intense electronic absorption bands with
vibronic fine structure in the region 265-422 nm (Fig. 5). The intense absorption bands in the
region 265-340 nm are due to intra-ligand transitions (π→π*/ n→π*). Further, the absorption
bands in the region, 354-441 nm are attributed to LLCT (ligand to ligand charge transfer) and
MLCT (metal to ligand charge transfer) bands. It may be noted that similar type of assignments
2
have been made in literature for the dinuclear complexes, [M
2
(dtbpy)
2
(µ-κ :N,S-pyS)
2
4 2
][ClO ]
(
M = Pt or Pd; dtbpy = 4, 4'-di-tert-butyl-2,2'-bipyridine) [59]. In order to check the emission
property, the complexes were excited in the region 320 to 360 nm and complexes have shown
intense emission bands in the 360-600 nm region with λmax at 422 to 442 nm (Fig. 6). The
emission bands are attributed to the transitions from excited state of ligands (π*) to the ground
state of ligands (π) [LLCT] or and transition from excited state of ligand (π*) to ground state of
2
metal (dσ*, dz ) orbital [LMCT]. These transitions are assigned on a pattern similar to that
reported in literature [59].
1
8

1
3
4
Fig. 5. Electronic absorption spectra of complexes 1, 3 and 4.
1
9

1
1
0
0
0
0
0
.2
.0
.8
.6
.4
.2
.0
1
4
3
3
50
400
450
500
550
600
Wavelength (nm)
em
ex
em
Fig. 6. Fluorescence spectra of complexes 1 (λmax = 442 nm, λmax = 322 nm), 3 (λmax = 442
ex
em
ex
nm, λmax = 342 nm) and 4 (λmax = 439 nm, λmax = 358 nm).
1
2
2
1
The H NMR spectra of complexes, [Pd
2
(µ- κ :N, S-pyS)
3
(κ :P,P-dppm)]Cl 1, [Pd(κ :S-
2
1
imzSH)
4
]Cl
2
·2H
2
O 3, and [Pt
2
(µ-κ :N,S-pyS)
3
(κ :P,P-dppm)]Cl 4, has been recorded. Complex 1
did not show the presence of NH proton signals (δ = 13.40 ppm, free pySH ligand) suggesting
-
that the thio ligands are coordinating to the metal center as mono anions (pyS ). The pyridyl
6
3
4
5
group of a thio ligand shows more than one signal due to each of H , H , H , and H protons
which reveal difference in chemical environment of pyridyl groups in the mixed valent complex.
6
3
The H and H protons showed the highest low field shifts and support coordination of nitrogen
4
5
and sulfur donor atoms to the metal centers. The H and H proton signals also move downfield
in the complex. The low field shifts in pyridyl proton signals of complex 4 are somewhat lower
than those shown by complex 1 (see experimental). The phenyl protons of dppm in complexes 1
and 4 appeared as resolved multiplets for o-, p- and m-H at δ = 7.69-7.70, 7.14-7.37, 6.91-7.27
ppm respectively. The -CH
2
- protons appeared as two separate sets of multiplets at δ 4.24 and
4
.41; 4.33 and 4.66 ppm for complexes 1 and 4 respectively. The NMR spectrum of complex 2
2
0

could not be recorded due to due to its poor solubility. The NH (δ = 11.93 ppm) and ring protons
4
5
(
H , H , δ = 7.25 ppm) of imidazoline ring in complex 3 moved high field relative to the free
4
5
31
ligand (NH proton, δ = 12.17 ppm, H , H δ = 7.28 ppm). The P NMR spectrum of complex 1
3
1
shows two P NMR signals at δ = 32.46 ppm, (Jp-p = 61.5 Hz) and 28.02 ppm (Jp-p = 60 Hz)
3
1
corresponding to two different types of phosphorus atoms. Similarly, P NMR spectrum of
3
1
complex 4 also shows two P NMR signals at δ = 12.70 (Jp-p = 38.9 Hz) ppm and 8.29 (Jp-p
=
3
1
3
8.9 Hz) ppm. The presence of two sets of P NMR signals could be due to non equivalent
1
95
environment around the phosphorus atoms (Figs. 7 and 8). The lack of satellites due to Pt
1
95
nucleus with I = 1/2 is due to the low abundance of Pt.
2
1

3
1
2
Fig. 7. P NMR spectrum of [Pd
2
(µ- κ : N, S-pyS) (dppm)]Cl 1.
3
14.0 13.5 13.0 12.5 12.0 11.5 11.0 10.5 10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
3
1
2
Fig. 8. P NMR spectrum of [Pt
2
(µ- N, S-pyS)
3
(κ :P,P-dppm)]Cl 4.
2
2

3
.4. ESI Mass spectral studies
ESI-mass spectral data of complexes (1, 3, 4) have been obtained. The purpose of carrying
+
out this study was to determine the molecular ion ([M] ), to understand the fragmentation pattern
and formation of new species, if any. Complexes 1 and 4 showed the presence of the molecular
+
species, [M] (1 : m/z obsd. 925.95; calcd. 925.94); (4 : m/z obsd. 1104.13; calcd.1104.07)
+
(
Figs. 9 and 10). Fig. 11 reveals ESI-mass peak due to [Pd(imzSH)
3
Cl] species (3 : m/z obsvd
4
40.93, m/z calcd. 440.90) and its isotopic pattern. A few other species are placed in
supplementary.
Intens.
5
+MS, 0.0-0.9min #2-55
x10
1.0
0.8
0.6
0.4
0.2
0.0
1
+
9
27.9864
1
+
1+
26.9873
9
25.9864
1+
929.9863
9
1
+
1
+
9
24.9868
1
+
928.9880
9
23.9864
1+
31.9861
1
+
9
30.9874
9
9
22.9855
1+
32.9866
1+
33.9857
9
9
9
21.9833
22
9
924
926
928
930
932
934 m/z
C₄₀H₃₄N₃S₃Pd₂P₂, M, 925.9454
2500
2000
1500
1000
1
+
9
27.9471
1+
1+
1
+
9
25.9472 926.9479
1
+
929.9473
1
+
924.9480
9
28.9486
1
+
9
23.9478
1
+
1+
30.9491
9
31.9474
9
1
+
1
+
9
22.9479
1+
33.9481
500
1+
21.9474
932.9496
9
9
0
922
924
926
928
930
932
934 m/z
+
Fig. 9. ESI-mass peak due to the species [Pd
25.94 with isotopic pattern (complex 1)
2
(pyS) (dppm)] , m/z observed 925.95, m/z calcd.
3
9
2
3

Intens.
4
+MS, 0.0-0.6min #2-34
x10
4
3
1
+
1104.1316
1+
1
105.1337
1
+
2
1
0
1103.1307
1106.1329
1
+
1
107.1337
1+
1
102.1276
1108.1340
1
+
1
109.1341
1
100
1102
1104
1106
1108
1110
m/z
C₄₀H₃₄N₃S₃Pt₂P₂, M, 1104.0680
3000
2000
1000
0
1
+
1
104.0672
1+
105.0685
1
1
+
1+
1
103.0661
1106.0689
1
+
1
+
1107.0701
1+
1
102.0639
1108.0708
1
+
1
+
1
109.0718
1
110.0718
1
100
1102
1104
1106
1108
1110
m/z
+
Fig. 10. ESI-mass peak due to the species [Pt
2
(pyS)
3
dppm] , m/z observed 1104.13, m/z calcd.
1
104.07 with isotopic pattern (complex 4)
Intens.
4
+MS, 0.0min #2
x10
2.0
1.5
1.0
0.5
0.0
1
+
1
+
442.9271
4
40.9272
1
+
4
39.9292
444.9265
1
+
4
41.9259
4
38.9271
1+
43.9258
1+
446.9245
1
+
4
4
45.9258
4
38
439
440
441
442
443
444
445
446
447
m/z
C₉H₁₂N₆S₃ClPd, M, 440.9003
3000
2000
1000
0
1
+
1
+
442.8995
4
40.9003
1
+
1
+
4
44.8994
4
39.9020
1
+
1+
38.9008
4
41.8997
4
1+
43.9003
1+
446.8977
1
+
4
4
45.9012
4
38
439
440
441
442
443
444
445
446
447
m/z
+
Fig. 11. ESI-mass peak due to [Pd(imzSH)
with isotopic pattern (complex 3)
3
Cl] species, m/z observed 440.93, m/z calcd. 440.90
2
4

4
1
. Conclusion
Three mixed-ligands dinuclear complexes, namely, [Pd
II
2
2
(µ-κ :N,S-pyS) (µ-P,P-dppm)]Cl
3
II
2
1
II
2
, [Pd
2
(µ-κ :N,S-bzimS)
2
(κ -S-bzimS)(PPh
3
)
3
]Cl·2H
2
O
2 and [Pt
2
(µ-κ :N,S-pyS) (µ-P,P-
3
-
-
dppm)]Cl 4, have been synthesised (pyS = pyridine-2-thiolate; bzimS = benzimidazoline-2-
thiolate; dppm = Ph
2
P-CH
2
-PPh ). Using a different procedure, equimolar reaction of
2
II
II
[
[
PdCl
2
(dppm)] with sodium salt of pyridine-2-thiolate in ethanol also gave a Pd -Pd dimer,
2
2
Pd (µ- κ :N, S-pyS) (κ : P,P-dppm)]·Cl [14]. The difference in bonding of thio-ligands in
2
3
complex 2 relative to complexes 1 and 4 is probably due to the higher steric requirement of
benzimidazoline-2-thiolate anion which has not favored multiple bridging between two metals.
Complexes 1, 3 and 4 have shown intense fluorescence. ESI mass studies of 1 and 4 have
+
+
supported the formation of the molecular species, [Pd
respectively.
2
(pyS)
3
(dppm)] and [Pt
2
(pyS) (dppm)]
3
Supplementary material
CCDC, 1426481(1), 1426482 (2), 1426483 (3) and 1426484 (4) contain the supplementary
crystallographic data for complexes 1-4 respectively of this paper. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-
0
33; mail: deposit@ccdc.cam.ac.uk. supporting information: spectroscopic data of ligands; ESI-
mass data of complexes.
Acknowledgements
Financial support from University Grants Commission [Major Project : F. No. 34-307\ 2008
(
SR)], New Delhi is gratefully acknowledged. RJB acknowledges the NSF-MRI program (grant
No. CHE0619278) for funds to purchase the X-ray diffractometer. SKG wishes to thank USIEF
for the award of Fulbright-Nehru Senior Fellowship. We thank
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