One-pot synthesis of sulphur bridged dinuclear rhenium metallacycles via addition of S-S bond across Re-Re bond

Article abstract of DOI:10.1016/j.jorganchem.2010.02.027

Oxidative addition of diaryl disulphides RSSR to low-valent transition metal carbonyl Re₂(CO)₁₀ with monodendate pyridine ligands bring forth novel sulphur bridged neutral dinuclear rhenium metallacycles [L(CO)₃Re(μ-SR)

Full text of DOI:10.1016/j.jorganchem.2010.02.027

Journal of Organometallic Chemistry 695 (2010) 1458–1463
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
One-pot synthesis of sulphur bridged dinuclear rhenium metallacycles via
addition of S–S bond across Re–Re bond
A. Vanitha a, P. Sathiya a, S. Sangilipandi a, Shaikh M. Mobin b, Bala. Manimaran a,
*
a Department of Chemistry, Pondicherry University, Puducherry 605 014, India
b National Single Crystal X-ray Diffraction Facility, Indian Institute of Technology-Bombay, Powai, Mumbai 400 076, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Oxidative addition of diaryl disulphides RSSR to low-valent transition metal carbonyl Re2(CO)10 with
monodendate pyridine ligands bring forth novel sulphur bridged neutral dinuclear rhenium metallacy-
cles [L(CO)3Re(l-SR)2Re(CO)3L] (1–9) (L = pyridine ligand, R = aryl group) under one pot reaction condi-
tions. The Metallacycles 1–9 have been characterised by elemental analysis, NMR and IR and
absorption spectral analysis. Molecular structures of 4, 8 and 9 were determined by crystallographic anal-
ysis and the structural studies reveal that pyridyl groups attached to metal centres exhibit cis
conformation.
Received 20 December 2009
Received in revised form 11 February 2010
Accepted 25 February 2010
Available online 3 March 2010
Keywords:
Rhenium carbonyl
Diaryl disulphides
Pyridine ligands
Oxidative addition
Metallacycles
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
complexes were prepared from the reaction of benzene thiol with
Re(CO)5OTf as well as from the reaction of S2Ph2 with Re2(CO)10
Transition metal complexes containing the disulphide ligand
exhibit a wide range of interesting reactivity and chelating ability
at the sulphur atoms [1–8]. Metal sulphides are of interest due to
their wide application in various platforms, such as, catalyst for
the removal of organosulphur compounds from the feedstock
[9,10], as solid state lubricant [11], as good electrical conductor
[12–15] and for their role in NO storage and transport in vivo
to stabilize therapeutic protein structures in the biological pro-
cesses [16–18]. Recent studies have shown that metal disul-
phides can also exhibit a variety of important nanostructures
[19,20] and metal sulphide nanoparticles serve as catalysts with
very high reactivities [21–23]. Earlier, sulphur bridged Re and
Mn dinuclear complexes [Re(CO)4(SPh)]2 were obtained from
benzene thiol and metal hydrido complexes [24]. A decade ago,
under photolytic condition [27,28]. Hetero-multiple bridged rhe-
nium compounds Re2X2(CO)6S2Ph2 (X = Br, I) were synthesised
from rhenium pentacarbonyl halides and S2Ph2 [29,30] where,
cleavage of disulphide bond was not observed. Recent literature
evinced that Re2(l-SPh)3Cl4(PEt2Ph2) was obtained from Re2-
Cl4(PEt2Ph)4 and Ph2S2 [31], anionic [(CO)3Mn(
l
-SC8N2H4-o-
2ꢀ
S–)]2
complex was prepared from 2,3-quinoxalinedithiol and
[Mn(CO)5]ꢀ and neutral [(Mn(CO)3)2(
l-SC6H4-o-S–S–C6H4-o-l-S–)]
and [(Mn(CO)3(l-SC6H4-o-NH2–)]2 complexes were synthesised
by multi-step processes [32]. Deeming and coworkers have re-
ported that the reaction of Re2(CO)10 with pyridine-2-thione
yielded [Re2(pyS)2(CO)8] [33] and similar kind of Re and Mn com-
plexes [M2(l-pyS)2(CO)8] were obtained from [Re3(l-H)3(CO)11
(MeCN)] and Mn2(CO)10 respectively, with pyridine-2-thiolato li-
gands [34,35]. The reaction of Re(CO)5Cl with 8-thiohydroxyquin-
oline hydrochloride afforded the dimeric compound Re2(CO)6
(SX)2 [36]. Reactions of diaryl disulphide with Re2(CO)10 led to
the formation of [Re2(CO)8(l-SR)2] in much low yields under
thermolytic condition, while similar reactions carried out in pres-
hydrido sulphide bridged dirhenium complexes [Re2(l-H)(l-
SR)(CO)8] [R = H, n-Bu, Ph, 2-naphthyl] were generated from
[Re2(CO)8(MeCN)2] precursor with thiols [25]. Rosenberg and
coworkers have reported that dimetallic rhenium and manganese
complexes M2(CO)6(
l-
g
4-SC6H4S–SC6H4S)2 [M = Re, Mn] were ob-
tained from thiols and metal carbonyls [26], and [Re2(CO)8(SPh)2]
ence of pyridyl ligands resulted into the facile formation of [Re2
(CO)6(L)2(
synthesis of sulphur bridged neutral dinuclear rhenium metalla-
cycles [L(CO)3Re( -SR)2Re(CO)3L] (1–9) via oxidative addition of
l-SR)2] compounds. Herein, we report on the one-pot
l
S–S bond across Re–Re bond by the reaction of Re2(CO)10 and
diaryl disulphides with monodentate pyridine ligands.
* Corresponding author. Tel.: +91 413 2654414; fax: +91 413 2655987.
E-mail address: manimaran.che@pondiuni.edu.in (B. Manimaran).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.02.027

A. Vanitha et al. / Journal of Organometallic Chemistry 695 (2010) 1458–1463
1459
let and multiplet for phenylpyridine protons and the benzyl group
protons showed one doublet, one singlet and multiplet. When
compared with free ligand, proton signals of metallacycles were
shifted towards upfield except one doublet of pyridyl group. 13C
NMR of compounds 3, 6 and 9 exhibited carbonyl group peaks at
around d 200–194 ppm with 1:2 ratio and the signals at d 156–
122 ppm were assigned for pyridyl carbons and signals at around
d 142–126 ppm were assigned to phenyl carbons. The proton sig-
nals of benzyl sulphido bridged metallacycles 7–9 were found to
be shifted more towards downfield compared to phenyl and p-tolyl
sulphido bridged metallacycles 1–3 and 4–6 respectively. Absorp-
tion spectra of 1–9 in dichloromethane displayed higher energy
2. Results and discussion
2.1. Synthesis of sulphur bridged metallacycles 1–9 from Rhenium
carbonyl, diaryl disulphides and monodendate pyridine ligands
Synthesis of sulphur bridged Re(I) metallacycles proceeded
with simultaneous incorporation of two aryl sulphido ligands to
the equatorial sites of fac-Re(CO)3 core with substitution of CO
groups by rigid monotopic N-donor ligands to the axial site [37–
39]. The formation of metallacycles 1–9 were accomplished by
oxidative addition of diaryl disulphide (RSSR) to the rudimentary
rhenium carbonyl with monodentate pyridine ligands like pyridine
(py), 4-picoline (pic) and 4-phenylpyridine (Phpy) in mesitylene
medium (Scheme 1). The formal oxidative cleavage of S–S bond
and addition across the rhenium–rhenium bond afforded the
sulphur bridged dinuclear neutral metallacycles cis-[L(CO)3Re
transitions at around kmax 226–269 nm, and were attributed to li-
*
gand based
p–p
transitions. In addition, phenylpyridine contain-
ing compounds 3, 6 and 9 showed lower energy bands at around
kmax 340–358 nm due to MLCT transitions [38,41–48]. Metallacy-
cles 1–9 upon excitation at their respective ligand centred transi-
tions exhibited moderate emissions observed at around 400 nm.
(l-SR)2Re(CO)3L] (1–9) (L = pyridine ligand, R = aryl group). In case
of compound 5, the trans isomer has also been obtained as a minor
product. Metallacycles 1–9 were soluble in common organic sol-
vents and stable at room temperature.
However compound 5 showed two emission bands at 280 and
*
304 nm due to
p
–p
excited state of the ligands [49,50].
2.3. Structural characterisation of 4, 8 and 9
2.2. Spectroscopic characterisation of compounds 1–9
Single crystals of compounds 4, 8 and 9 were obtained by slow
diffusion of hexane into concentrated solution of compounds in
dichloromethane. Crystals of 4 and 8 were obtained at room tem-
perature and for compound 9 crystals were obtained at 5 °C. A
good quality single crystals of 4, 8 and 9 were subjected to X-ray
diffraction studies. Details about data collection, solution and
refinement were summarized in Table 1 and the molecular struc-
tures of compounds 4, 8 and 9 were depicted in Figs. 1–3,
respectively.
Crystal structure of 4 adopted dinuclear metallacyclic structure,
where each rhenium in fac-Re(CO)3 core is bonded to one pyridyl
and two aryl sulphido group and hence Re centres attained a dis-
torted octahedral geometry with C2v symmetry [33,34,40]. The
Re2S2 ring is non-coplanar with a dihedral angle of 5.2° between
the Re(1)–S(1)–Re(2) and Re(1)–S(2)–Re(2) planes. The ReꢁꢁꢁRe dis-
tance in Re2S2 ring is 3.830 Å. The octahedral geometry is associ-
ated with the angles of 84.7(1)° for S(1)–Re(1)–N(1), 84.3(1)° for
S(2)–Re(1)–N(2), 79.85(4)° for S(1)–Re(1)–S(2) and S(1)–Re(2)–
S(2). The two pyridyl groups are oriented in a cis conformation
The IR spectrum of compounds 1–9 in CH2Cl2 exhibited car-
bonyl stretching at the region of 2021–1900 cmꢀ1 characteristic
of facial assembly of three terminal carbonyl ligands (fac-Re(CO)3)
in an octahedrally coordinated metal centre [40]. 1H NMR spectra
of compounds 1–9 displayed appropriate signals for the pyridine
ligands and aryl groups bonded to bridging sulphur and the data
of the compounds were given in experimental section. In 1H
NMR spectra of compounds 1, 4 and 7 displayed, one doublet,
two triplets for pyridyl group (py) protons and phenyl group pro-
tons showed one doublet and two triplets. When compared with
free pyridine ligand (8.60, 7.65 and 7.26 ppm) and free diaryl disul-
phide (7.49, 7.30 and 7.23), the pyridyl and aryl group proton sig-
nals were shifted towards downfield in compounds. 13C NMR of
compounds 1, 4 and 7 showed signals for terminal carbonyl groups
at around d 201–182 ppm with 1:2 ratio and the signals at d 155–
124 ppm were attributed to pyridyl group and the phenyl group
carbons resonated at d 139–126 ppm. The 1H NMR spectra of com-
pounds 2, 5 and 8 displayed, two doublets for pyridyl protons and
methyl group protons showed a singlet. When compared to unco-
ordinated ligand, the protons signals were shifted towards the
downfield. 13C NMR of compounds 2, 5 and 8 displayed carbonyl
group peaks at around d 201–195 ppm with 1:2 ratio and the sig-
nals at d 155–125 ppm were assigned to pyridyl group and phenyl
group carbons appeared at around d 149–126 ppm. In 1H NMR
spectra of compounds 3, 6 and 9 displayed, two doublets, one trip-
and stabilised by weak face-face
p–p stacking interaction with a
distance of 3.818 Å at C4 and C4’ carbons of two pyridyl groups
(Fig. 1) [51–54]. The two p-tolyl groups bonded to bridging sulphur
are arranged in nearly the same plane that of two pyridyl groups
and bent away from the Re2S2 ring and pyridyl groups. C–Hꢁꢁꢁ
p
interactions were observed in between the two p-tolyl groups of
adjacent molecules (2.896 Å) [38,55–58]. C–HꢁꢁꢁO hydrogen
Scheme 1. Synthesis of sulphur bridged dinuclear metallacycles 1–9.

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A. Vanitha et al. / Journal of Organometallic Chemistry 695 (2010) 1458–1463
Table 1
Crystallographic data and structure refinement of 4, 8 and 9.
Compound
4
8
9
Empirical
Formula
Formula weight
Crystal system
T (K)
Space group
a (Å)
b (Å)
C30H24N2O6Re2S2
C32H28N2O6Re2S2
C42H32N2O6Re2S2
945.03
Tetragonal
150(2)
P 41 21 2
10.3069(3)
10.3069(3)
28.9013(14)
90
973.08
1097.22
Monoclinic
150(2)
Monoclinic
293(2) K
p 21/n
14.3664(5)
15.1547(6)
15.8619(8)
90
p 21/n
9.8062(8)
17.0820(11)
23.360(2)
90
c (Å)
a
(°)
b (°)
90
90
3070.2(2)
4
103.271(4)
90
3361.2(2)
4
99.369(8)
90
3860.8(5)
4
c
(°)
V (Å3)
Z
F(0 0 0)
1792
2.044
8.059
1856
1.923
7.364
2112
1.888
6.424
Dcalc (mg mꢀ3
)
l
(mmꢀ1
)
h, k, l collected
ꢀ12,12; ꢀ12,10;
ꢀ34, 34
3.13–25.00
ꢀ12,17; ꢀ16,18;
ꢀ11,11; ꢀ20, 20;
ꢀ27, 27
3.33–25.00
ꢀ18,18
Theta range for
data
2.99–25.00
collection (°)
Crystal size
(mm)
0.32 ꢂ 0.28 ꢂ 0.25 0.38 ꢂ 0.32 ꢂ 0.28 0.23 ꢂ 0.18 ꢂ 0.15
Reflections
collected/
unique
24 479/2710
13 222/5703
28 289/6784
Rint
0.0969
0.0386
0.0894
Data/restraints/
parameters
Final R indices
2710/0/191
5703/0/399
6784/0/487
Fig. 1. Molecular structure of 4. The thermal ellipsoids are drawn at the 50%
probability level. Important bond lengths (Å) and angles (°): Re(1)–S(1) 2.492(1),
Re(1)–N(1) 2.206(4), Re(1)–S(1)–Re(1) 99.92(4), S(1)–Re(1)–S(1) 79.85(4), N(1)–
Re(1)–S(1) 84.7(1).
R1 = 0.0294,
wR2 = 0.0420
1.168
R1 = 0.0404,
wR2 = 0.0840
1.029
R1 = 0.0542,
wR2 = 0.1391
1.096
[I > 2r(I)]
Goodness-of-fit
(GOF) on F2
R indices
R1 = 0.0307,
R1 = 0.0736,
R1 = 0.0680,
(all data)
wR2 = 0.0423
wR2 = 0.0944
wR2 = 0.1439
Largest
0.539 and ꢀ0.658 1.291 and ꢀ0.742 4.172 and ꢀ1.584
difference in
peak and hole
(e Åꢀ3
)
bondings were viewed in between C3 of p-tolyl moiety and car-
bonyl group with a distance of 2.701 Å, and H2 proton of pyridyl
group bonding with another carbonyl group with a distance of
2.597 Å [59–61].
Crystal structure of 8 adopted a dinuclear metallacyclic struc-
ture, where each rhenium in fac-Re(CO)3 core is bonded to one pic-
oline and two benzyl sulphido group and hence Re centres attained
a distorted octahedral geometry. The Re2S2 ring is non-coplanar
with a dihedral angle of 7.74° between the Re(1)–S(1)–Re(2) and
Re(1)–S(2)–Re(2) planes. The ReꢁꢁꢁRe distance in Re2S2 ring is
3.837 Å. The octahedral geometry is associated with the angles of
84.1(2)° for N(1)–Re(1)–S(1), 85.6(2)° for N(2)–Re(2)–S(1),
99.36(8)° for Re(1)–S(1)–Re(2) and 99.64(7)° for Re(2)–S(2)–
Re(1). The two pyridyl groups are oriented in a cis conformation
and stabilised by weak face–face
p–p stacking interaction with a
distance of 3.809 Å at C4 and C4’ carbons of pyridyl groups
(Fig. 2). The two benzyl groups bonded to bridging sulphur are ar-
ranged in a same direction and bent away from the Re2S2 ring and
Fig. 2. Molecular structure of 8. The thermal ellipsoids are drawn at the 50%
probability level. Important bond lengths (Å) and angles (°): Re(1)–S(1) 2.510(2),
Re(1)–S(2) 2.512(2), Re(2)–S(2) 2.510(2), Re(2)–S(1) 2.523(2), Re(1)–S(1)–Re(2)
99.36(8), Re(2)–S(2)–Re(1) 99.64(7), S(1)–Re(1)–S(2) 80.09(7), S(2)–Re(2)–S(1)
79.88(7).
pyridyl groups. C–Hꢁꢁꢁ
p interactions were observed among CH2
group of benzyl and C3 carbon of picoline groups with a distance
of 2.879 Å. C–HꢁꢁꢁO hydrogen bondings were observed in between
carbonyl group and C3 carbon of benzyl group (2.696 Å) and C2 car-
bon of picoline group with another carbonyl group (2.495 Å).
Molecular structure of 9 adopted dinuclear metallacyclic struc-
ture, where each rhenium in fac-Re(CO)3 core is bonded to one
phenylpyridine and two aryl sulphido group and hence Re centres
attained a distorted octahedral geometry. The Re(1)–S(1) and
Re(1)–S(2) distances are not equal and Re2S2 ring is non-coplanar
with a dihedral angle of 17.85° between Re(1)–S(1)–Re(2) and
Re(1)–S(2)–Re(2) planes. In case of molecular structure of 4 and

A. Vanitha et al. / Journal of Organometallic Chemistry 695 (2010) 1458–1463
1461
rials were purchased from Sigma–Aldrich Chemicals. Rhenium car-
bonyl, diphenyl disulphide, p-tolyl disulphide, dibenzyl disulphide,
4-phenylpyridine were used as received. Pyridine, 4-picoline,
mesitylene and other solvents were dried using literature proce-
dure prior to use. IR spectra were taken on a Thermo Nicolet
6700 FT-IR spectrometer. 1H and 13C NMR were recorded on a
Avans Bruker 400 MHz spectrometer. Absorption spectra were re-
corded on a Varian Cary 5000 UV–Vis spectrophotometer. Emission
spectra were recorded on a Fluorolog Horiba jobin Yuvon SPEX-
F311 spectrometer. Elemental analysis were performed using Ele-
mentar Micro Cube CHN analyzer.
3.2. Synthesis of cis-[L(CO)3Re(l-SR)2Re(CO)3L], general procedure
A
mixture of Re2(CO)10 (0.3 mmol) and diaryl disulphide
(0.2 mmol) were taken in a 50 ml two neck Schlenk flask and fitted
with a reflux condenser. The system was evacuated and N2 was
purged. Monodentate pyridine ligand and 30 ml of mesitylene
was added in N2 atmosphere. The reaction mixture was heated to
reflux under N2 for 10–19 h and allowed to cool to room tempera-
ture. The mesitylene was removed by vacuum distillation and the
solid mixture was washed with hexane, chromatographed on sili-
cagel using dichloromethane and hexane as eluent to gave white
colour solid of [L(CO)3Re(l-SR)2Re(CO)3L] metallacycles.
3.3. cis-[L(CO)3Re( -SC6H5)2Re(CO)3L] [L = py] (1)
l
A mixture of Re2(CO)10 (196 mg, 0.3 mmol) and diphenyl disul-
phide (44 mg, 0.2 mmol), were taken in a 50 mL two neck Schlenk
flask and fitted with a reflux condenser. The system was evacuated
and N2 was purged. Pyridine (2 ml, 24 mmol) and 30 ml of mesity-
lene were added under N2 atmosphere. The reaction mixture was
heated to 130 °C under N2 for 10 h and allowed to cool to room tem-
perature. Some of the settled white solid was separated from the
reaction mixture, and the solvent was removed by vacuum distilla-
tion. The solid mixture was washed with hexane, chromatographed
on silicagel using dichloromethane and hexane as eluent to gave
Fig. 3. Molecular structure of 9. The thermal ellipsoids are drawn at the 30%
probability level. Important bond lengths (Å) and angles (°): Re(1)–S(1) 2.517(2),
Re(1)–S(2) 2.495(3), Re(2)–S(2) 2.516(2), Re(2)–S(1) 2.516(2), Re(2)–S(1)–Re(1)
98.51(9), Re(1)–S(2)–Re(2) 99.12(9), S(2)–Re(1)–S(1) 78.59(8), S(2)–Re(2)–S(1)
78.22(8).
8 the dihedral angles were found to be 5.2° and 7.74° respectively.
The ReꢁꢁꢁRe distance 3.814 Å in Re2S2 ring was found to be de-
0
creased whereas C4–C4 distance 4.743 Å was observed to be in-
white colour solid of cis-[(py)(CO)3Re(l-SPh)2Re(CO)3(py)] Yield:
86 mg, 57% (based on Re2(CO)10). Anal. Calc. for C28H20N2O6Re2S2:
C, 36.67; H, 2.19; N, 3.05. Found: C, 37.33; H, 2.16; N, 3.28%. 1H
NMR (400 MHz, CDCl3, ppm): d 8.96 (d, 4H, H2 (py), 3J = 6.4 Hz),
7.79 (d, 4H, H2 (ph), 3J = 8.0 Hz), 7.64 (t, 2H, H4 (py), 3J = 7.6 Hz),
7.34 (t, 4H, H3 (py), 3J = 7.6 Hz); 7.17 (t, 4H, H3 (ph), 3J = 6.4 Hz),
7.12 (t, 2H, H4 (ph), 3J = 6.4 Hz). 13C NMR (100 MHz, CDCl3, ppm): d
198.8, 195.0 (1:2, CO), 155.3, 138.8, 124.7 (py), 137.5, 131.4, 128.6,
creased when compared with compounds 4 and 8. The Re2S2 ring
was bent towards away from the phenylpyridine ligands. The octa-
hedral geometry was associated with an intraligand angle of
84.7(1)° for S(1)–Re(1)–N(1), 84.3(1)° for S(2)–Re(1)–N(2), 78.58°
for S(1)–Re(1)–S(2) and 78.23° for S(1)–Re(2)–S(2). The two phen-
ylpyridine ligands are oriented in a cis conformation with a dis-
0
tance of 4.743 Å at C4–C4 carbons of two pyridyl groups (Fig. 3).
125.9 (ph). UV–Vis. {CH2Cl2, k nm (
(32,100), 268 (35,150). Emission: kmax
(CH2Cl2):
e
) dm3 molꢀ1 cmꢀ1}: 229
The phenyl group at para position of the pyridyl ring bonded to
Re(1) was twisted by an angle of 99.97°, whereas the other phenyl
group of phenylpyridine bonded to Re(2) was twisted by an angle
of 121.28°. Two benzyl sulphido groups were bent away from the
em
(CH2Cl2)/(nm) 373. IR
m .
(CO) 2027 (m) 2012 (s) 1927 (m) 1904 (vs) cmꢀ1
3.4. cis-[L(CO)3Re(l-SC6H5)2Re(CO)3L] [L = pic] (2)
Re2S2 ring. Intermolecular C–Hꢁꢁꢁ
p interactions were observed in
between the phenyl groups of adjacent phenylpyridine ligands
(2.856 Å) and in between phenyl group of one phenylpyridine
and pyridyl group of another phenylpyridine ligands (2.896 Å).
Compound 2 was prepared using Re2(CO)10 (196 mg, 0.3 mmol),
diphenyl disulphide (44 mg, 0.2 mmol) and 4-picoline (2 ml,
20 mmol) in mesitylene (30 ml) following the procedure adopted
Two benzyl groups were interacted by C–Hꢁꢁꢁ
p interaction with a
for 1. It was isolated as a white solid of cis-[pic(CO)3Re(l-
distance of 2.880 Å. C–HꢁꢁꢁO hydrogen bondings were connected
the carbonyl group and C3 of benzyl group with a distance of
2.686 Å and another carbonyl group was interlinked by hydrogen
bonding with one benzyl and one phenylpyridine groups (2.558 Å).
SC6H5)2Re(CO)3pic]. Yield: 36 mg, 25% (based on Re2(CO)10). Anal.
Calc. for C30H24N2O6Re2S2: C, 38.13; H, 2.56; N, 2.96. Found: C,
38.08; H, 2.53; N, 2.92%. 1H NMR (400 MHz, CDCl3, ppm): d 8.85
(d, 4H, H2 (pic), 3J = 6.8 Hz), 7.36 (t, H3 4H, (ph), 3J =7.6 Hz); 7.85
(d, 4H, H2 (ph), 3J = 8.4 Hz), 7.24 (d, 4H, H3 (pic), J = 7.2 Hz); 7.19
(t, 2H, H4 (ph), 3J = 7.2 Hz), 2.45 (s, 6H, CH3 (pic)). 13C NMR
(100 MHz, CDCl3, ppm): d 195.2, 182.4 (1:2, CO), 154.8, 149.5,
3. Experimental
ab
3.1. Instruments and materials
125.4, 21.1 (pic), 139.0, 131.5, 128.5, 125.8 (ph). UV–Vis. {kmax
(CH2Cl2)/(nm) (e
) dm3 molꢀ1 cmꢀ1}: 228 (47,850), 265 (33,800).
em
All the reactions were carried out under dry, oxygen-free N2
atmosphere using standard Schlenk techniques. The starting mate-
Emission: kmax
(CH2Cl2)/(nm) 370. IR (CH2Cl2): m(CO) 2027 (m)
2012 (s) 1924 (m) 1903 (vs) cmꢀ1
.

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A. Vanitha et al. / Journal of Organometallic Chemistry 695 (2010) 1458–1463
0
3.5. cis-[L(CO)3Re(l-SC6H5)2Re(CO)3L] [L = Phpy] (3)
& H4 (Phpy)), 2.37 (s, 6H, CH3 (p-tolyl)). 13C NMR (100 MHz, CDCl3,
ppm): d 198.9, 195.3 (1:2, CO), 155.6, 149.9, 135.7, 130.3, 129.5,
Compound 3 was prepared using Re2(CO)10 (196 mg, 0.3 mmol),
diphenyl disulphide (66 mg, 0.3 mmol) and 4-phenylpyridine
(47 mg, 0.3 mmol) in mesitylene (30 ml) following the procedure
adopted for 1. It was isolated as a pale yellow solid of cis-[Phpy-
126.7, 122.0 (Phpy), 135.7, 135.5, 131.4, 129.5 (ph), 21.1 (CH3,
ab
(p-tolyl)). UV–Vis. {kmax (CH2Cl2)/(nm) (
226 (45,250), 264 (49,700), 358 (7,950). Emission: kmax
e
) dm3 molꢀ1 cmꢀ1}:
em
(CH2Cl2)/(nm) 402. IR (CH2Cl2): m(CO) 2026 (m) 2011 (vs) 1924
(CO)3Re(
l-SC6H5)2Re(CO)3Phpy]. Yield: 43 mg, 36% (based on
(m) 1902 (vs) cmꢀ1
.
Re2(CO)10). Anal. Calc. for C40H28N2O6Re2S2: C, 44.93; H, 2.64; N,
2.62. Found: C, 44.68; H, 2.68; N, 2.58%. 1H NMR (400 MHz, CDCl3,
ppm): d 9.01 (d, 4H, H2 (Phpy), 3J = 6.4 Hz), 7.85 (d, 4H, H2 (ph),
3.9. cis-[L(CO)3Re(
l
-SCH2C6H5)2Re(CO)3L] [L = py] (7)
0
3J = 8.4 Hz), 7.38 (t, 4H, H3 (Phpy), 3J = 7.2 Hz), 7.31 (m, 14H, Phpy
0
& ph), 7.20 (t, 2H, H4 (Phpy), 3J = 7.6 Hz). 13C NMR (100 MHz,
Compound 7 was prepared using Re2(CO)10 (196 mg, 0.3 mmol),
dibenzyl disulphide (49 mg, 0.2 mmol), and pyridine (2 ml,
24 mmol) in mesitylene (30 ml) following the procedure adopted
CDCl3, ppm): d 198.4, 195.0 (1:2, CO), 155.5, 149.8, 138.9, 131.5,
130.2, 126.6, 121.9 (Phpy), 135.4, 129.3, 128.6, 125.9 (ph). UV–
Vis. {kmax (CH2Cl2)/(nm) (
e
) dm3 molꢀ1 cmꢀ1}: 242 (49,800),
for 1. It was isolated as a white solid of cis-[py(CO)3Re(l-
ab
em
340 (950). Emission: kmax (CH2Cl2)/(nm) 404. IR (CH2Cl2): m(CO)
SCH2C6H5)2Re(CO)3py]. Yield: 108 mg, 62% (based on Re2(CO)10).
Anal. Calc. for C30H24N2O6Re2S2: C, 38.13; H, 2.55; N, 2.96. Found:
C, 37.98; H, 2.60; N, 2.91%. 1H NMR (400 MHz, CD3COCD3, ppm): d
8.75 (d, 4H, H2 (py), 3J = 6.8 Hz), 7.76 (tt, 2H, H4 (py), 3J = 7.6 Hz),
7.54 (d, 4H, H2 (ph), 3J = 7.8 Hz), 7.34 (t, 4H, H3 (py), 3J = 7.6 Hz),
7.26 (m, H3 & H4 (ph), 6H), 4.43 (s, 4H, CH2 (benz)). 13C NMR
(100 MHz, CD3COCD3, ppm): d 201.5, 195.2 (1:2, CO), 155.7,
2026 (s) 2012 (vs) 1925 (m) 1903 (vs) cmꢀ1
.
3.6. cis-[L(CO)3Re(l-SC6H4CH3)2Re(CO)3L] [L = py] (4)
Compound 4 was prepared using Re2(CO)10 (196 mg, 0.3 mmol),
p-tolyl disulphide (49 mg, 0.2 mmol), and pyridine (2 ml, 24 mmol)
in mesitylene (30 ml) following the procedure adopted for 1. It was
142.6, 126.2 (py), 139.3 129.6, 129.4, 127.9 (ph), 43.6 (CH2, (benz)).
ab
isolated as a white solid of cis-[py(CO)3Re(
l-SC6H4CH3)2Re(CO)3-
UV–Vis. {kmax (CH2Cl2)/(nm) (
e
) dm3 molꢀ1 cmꢀ1}: 228 (34,350),
(CH2Cl2)/(nm) 369. IR (CH2Cl2):
em
py]. Yield: 120 mg, 49% (based on Re2(CO)10). Anal. Calc. for
C30H24N2O6Re2S2: C, 39.49; H, 2.9; N, 2.87. Found: C, 38.67; H,
2.68; N, 2.77%. 1H NMR (400 MHz, CD3COCD3, ppm): d 9.03 (d,
4H, H2 (py), 3J = 6.4 Hz), 7.92 (t, 2H, H4 (py), 3J = 7.6 Hz), 7.75 (d,
4H, H2 (ph), 3J = 8.4 Hz), 7.41 (dt, 4H, H3 (py), 3J = 5.6 Hz), 7.19 (d,
4H, H3 (ph), 3J = 8.0 Hz), 2.34 (s, 6H, CH3 (p-tolyl)). 13C NMR
(100 MHz, CDCl3, ppm): d 198.8, 194.0 (1:2, CO), 154.3, 136.4,
267 (12,700). Emission: kmax
m(CO) 2021 (m) 2006 (s) 1913 (m) 1900 (vs) cmꢀ1
.
3.10. cis-[L(CO)3Re(l-SCH2C6H5)2Re(CO)3L] [L = pic] (8)
Compound 8 was prepared using Re2(CO)10 (196 mg, 0.3 mmol),
dibenzyl disulphide (49 mg, 0.2 mmol), and 4-picoline (2 ml,
20 mmol) in mesitylene (50 ml) following the procedure adopted
124.3 (py), 130.7, 134.6, 130.3, 128.2 (ph), 19.8 (CH3, (p-tolyl)).
ab
UV–Vis. {kmax (CH2Cl2)/(nm) (
e
) dm3 molꢀ1 cmꢀ1}: 229 (40,150),
(CH2Cl2)/(nm) 375. IR (CH2Cl2):
em
265 (29,950). Emission: kmax
for 1. It was isolated as a white solid of cis-[pic(CO)3Re(l-
m(CO) 2027 (m) 2012 (s) 1923 (m) 1904 (vs) cmꢀ1
.
SCH2C6H5)2Re(CO)3pic]. Yield: 34 mg, 25% (based on Re2(CO)10).
Anal. Calc. for C32H28N2O6Re2S2: C, 39.49; H, 2.90; N, 2.87. Found:
C, 39.61; H, 2.85; N, 2.89%. 1H NMR (400 MHz, CD3COCD3, ppm): d
8.57 (d, 4H, H2 (pic), 3J = 6.4 Hz), 7.52 (d, 4H, H2 (ph), 3J = 7.2 Hz),
7.33 (t, 4H, H3 (ph), 3J = 7.2 Hz), 7.26 (tt, 2H, H4 (ph), 3J = 7.2 Hz),
7.09 (d, 4H, H3 (pic), 3J = 6.6 Hz), 4.42 (s, 4H, CH2 (benz)), 2.37 (s,
6H, CH3 (pic)). 13C NMR (100 MHz, CD3COCD3, ppm): d 201.7,
195.3 (1:2, CO), 155.1, 151.3, 126.8 (pic)), 142.7, 129.6, 129.4,
3.7. cis-[L(CO)3Re(l-SC6H4CH3)2Re(CO)3L] [L = pic] (5)
Compound 5 was prepared using Re2(CO)10 (196 mg, 0.3 mmol),
p-tolyl disulphide (49 mg, 0.2 mmol), and 4-picoline (2 ml,
20 mmol) in mesitylene (30 ml) following the procedure adopted
for 1. It was isolated as a white solid of cis-[pic(CO)3Re(l-
ab
SC6H4CH3)2Re(CO)3pic]. Yield: 56 mg, 19% (based on Re2(CO)10).
Anal. Calc. for C32H28N2O6Re2S2: C, 39.49; H, 2.9; N, 2.87. Found:
C, 38.67; H, 2.81, N, 2.83%. 1H NMR (400 MHz, CDCl3, ppm): d
8.77 (d, 4H, H2 (pic), 3J = 6.4 Hz), 7.66 (d, 4H, H2 (ph), 3J = 8.4 Hz),
7.14 (d, 4H, H3 (ph), 3J = 8.0 Hz), 6.90 (d, 4H, H3 (pic), 3J = 6.4 Hz),
2.34 (s, 6H, CH3 (pic)). 2.33 (s, 6H, CH3 (p-tolyl)). 13C NMR
(100 MHz, CDCl3, ppm): d 198.7, 195.2 (1:2, CO), 154.7, 152.9,
127.8 (ph), 43.5 (CH2, (benz)), 21.1 (CH3, (pic)). UV–Vis. {kmax
(CH2Cl2)/(nm) (e
) dm3 molꢀ1 cmꢀ1}: 228 (31,400), 269 (11,150).
em
Emission: kmax
(CH2Cl2)/(nm) 366. IR (CH2Cl2): m(CO) 2019 (m)
2004 (s) 1913 (m) 1898 (vs) cmꢀ1
.
3.11. cis-[L(CO)3Re(l-SCH2C6H5)2Re(CO)3L] [L = Phpy] (9)
125.3, 21.0 (pic), 149.4, 135.5, 131.3, 129.3, (ph), 20.8 (CH3, (p-to-
ab
lyl)). UV–Vis. {kmax (CH2Cl2)/(nm) (
e
) dm3 molꢀ1 cmꢀ1}: 233
Compound 9 was prepared using Re2(CO)10 (196 mg, 0.3 mmol),
dibenzyl disulphide (74 mg, 0.3 mmol), and 4-phenylpyridine
(47 mg, 0.3 mmol) in mesitylene (30 ml) following the procedure
adopted for 1. It was isolated as a pale yellow solid of cis-[Phpy-
em
(11,850), 266 (20,500). Emission: kmax (CH2Cl2)/(nm) 280, 304.
IR (CH2Cl2): m(CO) 2025 (s) 2009 (vs) 1921 (w) 1902 (s) cmꢀ1
.
3.8. cis-[L(CO)3Re(l-SC6H4CH3)2Re(CO)3L] [L = Phpy] (6)
(CO)3Re(l-SCH2C6H5)2Re(CO)3Phpy]. Yield: 16 mg, 10% (based on
Re2(CO)10). Anal. Calc. for C42H32N2O6Re2S2: C, 45.97; H, 2.94; N,
2.55. Found: C, 45.08; H, 2.73; N, 2.43%. 1H NMR (400 MHz,
CD3COCD3, ppm): d 8.76 (d, 4H, H2 (Phpy), 3J = 6.4 Hz), 7.60 (d,
Compound 6 was prepared using Re2(CO)10 (130 mg, 0.2 mmol),
p-tolyl disulphide (49 mg, 0.2 mmol), and 4-phenylpyridine
(31 mg, 0.2 mmol) in mesitylene (30 ml) following the procedure
adopted for 1. It was isolated as a white solid cis-[Phpy(CO)3-
0
0
4H, H2 (Phpy), 3J = 8.4 Hz), 7.42 (t, 4H, H3 (Phpy), 3J = 6.8 Hz),
7.36 (d, 4H, H2 (benzyl), 3J = 6.0 Hz), 7.26 (m, H3 (Phpy & benzyl),
10H), 4.51 (s, 4H, CH2 (benz)). 13C NMR (100 MHz, CD3COCD3,
ppm): d 200.4, 194.4 (1:2, CO), 155.2, 149.3, 135.4, 130.0, 129.2,
Re(l-SC6H4CH3)2Re(CO)3Phpy]. Yield: 22 mg, 17% (based on
Re2(CO)10). Anal. Calc. for C42H32N2O6Re2S2: C, 45.97; H, 2.94; N,
2.55. Found: C, 45.87; H, 2.85, N, 2.63%. 1H NMR (400 MHz, CDCl3,
126.4, 121.7 (Phpy), 141.9, 129.0, 128.6, 127.0 (ph), 42.9 (CH2,
0
ab
ppm): d 9.0 (d, 4H, H2 (phpy), 3J = 6.8 Hz), 7.73 (d, 4H, H2 (Phpy),
(benz)). UV–Vis. {kmax (CH2Cl2)/(nm) (
e
) dm3 molꢀ1 cmꢀ1}: 229
em
3J = 8.0 Hz), 7.38 (t, 4H, H3’ (Phpy), 3J = 7.2 Hz), 7.32 (d, 4H, H2
(ph), 3J = 8.4 Hz), 7.19 (d, 4H, H3 (ph), 3J = 8.0 Hz), 7.29 (m, 6H, H3
(32,100), 268 (35,150), 348 (960). Emission: kmax (CH2Cl2)/(nm)
389. IR (CH2Cl2): m .
(CO) 2020 (s) 2005 (vs) 1914 (m) 1900 (vs) cmꢀ1

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Acknowledgments
We thank the Department of Science and Technology, Govern-
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Instrumentation Facility, Pondicherry University for providing
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CCDC 756132, 756131, and 756133 contain the supplementary
crystallographic data for 4, 8 and 9. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
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