Synthesis and characterization of some novel ruthenium(II) complexes containing thiolate ligands

Article abstract of DOI:10.1016/j.jorganchem.2009.12.006

Reactions of the ruthenium complexes [RuH(CO)Cl(PPh₃)₃] and [RuCl₂(PPh₃)₃] with hetero-difunctional S,N-donor ligands 2-mercapto-5-methyl-1,3,5-thiadiazole (HL¹), 2-mercapto-4-methyl-5-thia

Full text of DOI:10.1016/j.jorganchem.2009.12.006

Journal of Organometallic Chemistry 695 (2010) 994–1001
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of some novel ruthenium(II) complexes
containing thiolate ligands
*
Prashant Kumar, Mahendra Yadav, Ashish Kumar Singh, Daya Shankar Pandey
Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, UP, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of the ruthenium complexes [RuH(CO)Cl(PPh3)3] and [RuCl2(PPh3)3] with hetero-difunctional
S,N-donor ligands 2-mercapto-5-methyl-1,3,5-thiadiazole (HL1), 2-mercapto-4-methyl-5-thiazoleacetic
acid (HL2), and 2-mercaptobenzothiazole (HL3) have been investigated. Neutral complexes [RuCl
(CO)(PPh3)2(HL1)] (1), [RuCl(CO)(PPh3)2(HL2)] (2), [RuCl(CO)(PPh3)2(HL3)] (3), [Ru(PPh3)2(HL1)2] (4),
Received 30 September 2009
Received in revised form 4 December 2009
Accepted 7 December 2009
Available online 13 December 2009
[RuCl(PPh3)3(HL2)] (5), and [RuCl(PPh3)3(HL3)] (6) imparting
j
2-S,N-bonded ligands have been isolated
from these reactions. Complexes 1 and 4 reacted with diphenyl-2-pyridylphosphine (PPh2Py) to give
Keywords:
Ruthenium complexes
2-Mercapto-5-methyl-1,3,5-thiadiazole
2-Mercapto-4-methyl-5-thiazoleacetic acid
2-Mercaptobenzothiazole
neutral
j
1-P bonded complexes [RuCl(CO)( 1-P-PPh2Py)2(HL1)] (7), and [Ru( 1-P-PPh2Py)2(HL1)2] (8).
j
j
Complexes 1–8 have been characterized by analytical, spectral (IR, NMR, and electronic absorption)
and electrochemical studies. Molecular structures of 1, 2, 4, and 7 have been determined crystallograph-
ically. Crystal structure determination revealed coordination of the mercapto-thiadiazole ligands (HL1–
HL3) to ruthenium as
j
2-N,S-thiolates and presence of rare intermolecular S–S weak bonding interaction
Diphenyl-2-pyridylphosphine
in complex 1.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
Further, large size of sulfur makes it easier to adopt different angles
on coordination to metal ion in the complexes.
The role of organo-sulfur compounds is well documented in the
chemical and biological processes [1,2]. N-heterocyclic thiones con-
taining thioamide group are intriguing ligands in coordination
chemistry, since these can adopt versatile coordination modes
using exocyclic sulfur and endocyclic nitrogen donors (Scheme 1)
[3–6]. Mercapto-substituted thiadiazoles exist in thiol and thione
tautomeric forms. Also, these exhibit prototropic tautomerism,
acid–base equilibrium and redox reactions based on mercapto to
disulfido conversions. Tautomerization influences the reactivity of
thiadiazoles and has been demonstrated in the polymerization pro-
cesses [7], substitution reactions at different moieties [8,9], and in
metal complexation reactions [5,6]. A variety of N-heterocyclic
thiones having 5-membered, 6-membered and other condensed cy-
cles have extensively been used in the synthesis of both transition
and non-transition metal complexes [10–13]. Among these, 2-mer-
capto-5-methyl-1,3,5-thiadiazole (HL1), 2-mercapto-4-methyl-5-
thiazoleacetic acid (HL2), and 2-mercaptobenzothiazole (HL3) are
particularly interesting. Due to presence of two donor sites in its
protonated and deprotonated forms it may bind with two or more
metal ions within a rather rigid and compact molecular space and
promote interaction between the metal ions (Scheme 2) [14–19].
The synthetic utility of mercapto-functionalised thiadiazoles
and derivatives as bio-active compounds, metal chelating agents,
lubricant additives like corrosion inhibitors and anti-wear agents,
cross-linkers for polymers, components of cathode material bat-
tery systems, and in the syntheses of various organic compounds
has been reported [7,8,20,21]. A few platinum group metal com-
plexes imparting thiadiazole ligands have also been reported in
the literature [22,23]. Despite its extensive chemistry, reactivity
of the complexes [RuCl2(PPh3)3] and [RuH(CO)Cl(PPh3)3] with mer-
capto-functionalised thiadiazoles, has not yet been explored. Be-
cause of our interests in this area we have examined reactivity of
complexes [RuCl2(PPh3)3] and [RuH(CO)Cl(PPh3)3] with 2-mer-
capto-5-methyl-1,3,5-thiadiazole, 2-mercapto-4-methyl-5-thiaz-
oleacetic acid, and 2-mercaptobenzothiazole. Further, diphenyl-2-
pyridylphosphine is one of the most useful ligands applied in
coordination chemistry of the transition metals. It acts as a mono-
dentate or bidentate chelating ligand depending upon require-
ments of the metal centre [24–26]. We report herein syntheses,
spectral, electrochemical and structural characterization of some
ruthenium complexes containing mercapto-functionalised thi-
adiazoles in neutral chelating and diphenyl-2-pyridylphosphine
(PPh2Py) in neutral monodentate mode. Also, we describe herein
crystal structures of the complexes [RuCl(CO)(PPh3)2(HL1)], [RuCl-
(CO) (PPh3)2(HL2)], [Ru(PPh3)2(HL1)2], and [RuCl(CO)(
j
1-P-PPh2-
Py)2 (HL1)].
* Corresponding author. Tel.: +91 542 6702480.
E-mail address: dspbhu@bhu.ac.in (D.S. Pandey).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.12.006

P. Kumar et al. / Journal of Organometallic Chemistry 695 (2010) 994–1001
995
N
N
N
N
HN
N
solvent
S
S
HS
HS
S
S
S
S
S
S
solvent
S
HS
N
N
H
N
H
Scheme 1.
Microanalytical data: Anal. Calc. for C41H35Cl3N2OP2RuS2: C,
54.40; H, 3.90; N, 3.09. Found: C, 54.38; H, 3.86; N, 3.06%. 1H
NMR (d ppm): 7.36–7.02 (m, 30H, PPh3), 2.50 (s, 3H, CH3).
31P{1H} NMR (d ppm): 40.72 (s, PPh3). IR (KBr pellet, cmꢀ1):
1927 (s), 1575 (s), 1480 (s), 1433 (s), 1375 (m), 1188 (m), 1131
M
N
M
S
N
N
N
N
N
M
S
S
S
HS
S
(s), 1090 (m), 746 (m), 696 (s), 514 (s), 280
m(Ru–Cl). UV–Vis.
Scheme 2.
[kmax, nm ( )]: 483 (472), 355 (14 740), 277 (38 070), 247 (38 250).
e
2.2.2. Synthesis of [Ru(CO)Cl(PPh3)2(HL2)] 2
2. Experimental
2.1. Materials and physical measurements
It was prepared from [RuH(CO)Cl(PPh3)3] (0.1 g, 0.10 mmol) and
HL2 (0.19 mg, 0.10 mmol) following the above procedure for 1.
Complex 2 separated as a yellow crystalline solid. Yield: 0.657 g,
75%. Microanalytical data: Anal. Calc. for C43H37Cl3NO4P2RuS2: C,
53.51; H, 3.86; N, 1.45. Found: C, 53.86; H, 4.16; N, 1.62%. 1H
NMR (d ppm): 2.47 (s, 3H, CH3), 3.49 (s, 2H, CH2), 7.30–7.04 (m,
30H, PPh3). 31P{1H} NMR (d ppm): 44.82 (s, PPh3). IR (KBr pellet,
cmꢀ1): 3425 (m), 1930 (s), 1720 (s), 1576 (s), 1481 (s), 1430 (s),
1374 (m), 1182 (m), 1130 (s), 1089 (m), 746 (m), 696 (s), 518 (s),
Analytical grade chemicals were used throughout. The syn-
thetic manipulations were performed under oxygen free nitrogen
atmosphere. Solvents were dried and distilled before use by stan-
dard literature procedures [27]. Hydrated ruthenium(III) chloride,
2-mercapto-5-methyl-1,3,5-thiadiazole, 2-mercapto-4-methyl-5-
thiazoleacetic acid, 2-mercaptobenzothiazole, and 2-mercapto1-
methylimidazole and diphenyl-2-pyridylphosphine were procured
from Aldrich Chemical Company, Inc., USA and were used without
further purifications. The precursor complexes [RuH(CO)Cl(PPh3)3]
and [RuCl2(PPh3)3] were prepared and purified following the liter-
ature procedures [28,29].
292
m(Ru–Cl). UV–Vis. [kmax, nm (e)]: 485 (1980), 377 (14 400),
281 (37 400), 251 (37 700).
2.2.3. Synthesis of [Ru(CO)Cl(PPh3)2(HL3)] 3
The complex 3 was prepared following the above procedure for
1 except that HL3 (0.17 g, 0.10 mmol) was used in place HL1. It was
obtained as an orange microcrystalline solid. Yield: 0.572 g, 67%.
Microanalytical data: Anal. Calc. for C44H34ClNOP2RuS2: C, 61.78;
H, 4.01; N, 1.64. Found: C, 61.75; H, 4.02; N, 1.63%. 1H NMR (d
ppm): 8.61 (dd, 7.6 Hz, 1 H), 7.67 (dd, 7.8 Hz, 1 H), 7.33 (td,
7.8 Hz, 1 H), 7.24 (td, 7.6 Hz, 1 H), 7.28–7.02 (br m, PPh3).
31P{1H} NMR (d ppm): 39.85 (s, PPh3). IR (KBr pellet, cmꢀ1):
1927 (s), 1670 (s), 1576 (s), 1488 (s), 1435 (s), 1372 (m), 1182
C, H and N analyses were performed on an Exeter Analytical
Inc., Model CE-440 Elemental Analyzer. IR spectra were acquired
on
a Varian 3300 FT-IR spectrometer in the region 4000–
400 cmꢀ1. Electronic absorption spectra were recorded on a Shima-
dzu UV-1700 spectrophotometer at room temperature. 1H and 31P
NMR spectra in CDCl3 were obtained on a JEOL AL 300 FT-NMR
spectrometer at room temperature using TMS as an internal refer-
ence for 1H and 85% H3PO4 for 31P NMR. FAB mass spectra were re-
(m), 1131 (s), 1089 (m), 746 (m), 698 (s), 516 (s), 292
m
(Ru–Cl).
corded on
a
JEOL SX 102/Da-600 Mass Spectrometer.
UV–Vis. [kmax, nm (e)]: 479 (1480), 373 (13 200), 329 (37 700),
Electrochemical studies were performed on a CHI 620c Electro-
chemical Analyzer. A platinum working electrode, platinum wire
auxillary electrode, and Ag/Ag+ reference electrode were used in
a standard three-electrode configuration. Tetrabutylammonium
perchlorate (TBAP) was used as supporting electrolyte, and the
solution concentration was ca. 10ꢀ3 M.
253 (38 000).
2.2.4. Synthesis of [Ru(PPh3)2(HL1)2] 4
This complex was prepared using [RuCl2(PPh3)3] (0.1 g,
0.10 mmol) and HL1 (0.26 g, 0.20 mmol) in methanol (25 mL) fol-
lowing the procedure employed for 1. It was obtained as a yellow
crystalline solid. Yield: 0.790 g, 89%. Microanalytical data: Anal.
Calc. for C42H36N4P2RuS4: C, 56.81; H, 4.09; N, 6.31. Found: C,
56.80; H, 4.07; N, 6.33%. 1H NMR (d ppm): 7.34–7.10 (br m, 30H,
PPh3), 2.38 (s, 3H, CH3). 31P{1H} NMR (d ppm): 42.24 (s, PPh3). IR
(KBr pellet, cmꢀ1): 1572 (s), 1482 (s), 1432 (s), 1361 (m), 1189
(m), 1136 (m), 1085 (m), 807 (m), 744 (m), 696 (s), 519 (s). UV–
2.2. Syntheses
2.2.1. Synthesis of [Ru(CO)Cl(PPh3)2(HL1)]ꢁCH2Cl2
1
To a suspension of [RuH(CO)Cl(PPh3)3] (0.5 g, 0.67 mmol) in
methanol (25 mL), HL1 (0.066 g, 0.50 mmol) was added and con-
tents of the flask were heated under reflux for 8 h. Slowly, it gave
a clear orange solution. After cooling to room temperature the
solution was filtered through celite and concentrated to dryness
under reduced pressure. Residue was extracted with dichloro-
methane (5 mL) and filtered. Diethyl ether (50 mL) was added to
the filtrate, and left for slow crystallization. Slowly, it gave an or-
ange microcrystalline solid which was separated by filtration
washed with diethyl ether and dried in vacuo. Yield: 0.358 g, 72%.
Vis. [kmax, nm (e)]: 409 (2990), 341 (9360), 253 (38 400).
2.2.5. Synthesis of [RuCl(PPh3)3(HL2)] 5
Complex 5 was prepared following the above procedure for 4
using HL2 (0.19 mg, 0.10 mmol) in place of HL1 (0.26 g, 0.20 mmol).
It isolated as an orange microcrystalline solid. Yield: 0.799 g, 72%.
Microanalytical data: Anal. Calc. for C60H51ClNO2P3RuS2: C, 64.83;

996
P. Kumar et al. / Journal of Organometallic Chemistry 695 (2010) 994–1001
H, 4.62; N, 1.26. Found: C, 64.86; H, 4.61; N, 1.28%. 1H NMR (d
ppm): 2.37 (s, 3H, CH3), 3.46 (s, 2H, CH2), 7.38–7.02 (m, 45H,
PPh3). 31P{1H} NMR (d ppm): 59.72 (s, PPh3), and 54.90 (s, PPh3).
IR (KBr pellet, cmꢀ1): 3425 (m), 1718 (s), 1572 (s), 1475 (s), 1429
(s), 1372 (m), 1180 (m), 1126 (s), 1092 (m), 746 (m), 695 (s), 520
thermal parameters. All the hydrogen atoms were geometrically
fixed and allowed to refine using a riding model. The computer
program PLATON was used for analyzing interaction and stacking dis-
tances [31].
(s), 298
m(Ru–Cl). UV–Vis. [kmax, nm (e)]: 476 (1672), 367
2.3.2. Selected crystallographic data of the complexes
(14 200), 277 (37 200), 245 (33 500).
Complex 1. Formula = C41H35Cl3N2OP2RuS2, Mr = 905.19, Tri-
ꢀ
clinic space group P1, a = 11.397(3), b = 13.346(3), c = 13.889(4),
2.2.6. Synthesis of [RuCl(PPh3)3(HL3)] 6
a
l
= 80.022, b = 70.532,
= 0.828, T (K) = 120(2), k = 0.71073, Reflections collected/unique
(I)) = 0.0307,
c = 85.262, V = 1961.0(9), Z = 2, Dc = 1.533,
Complex 6 was prepared following the above procedure for 5
using HL3 (0.17 g, 0.10 mmol). After work-up it was obtained as a
yellow crystalline solid. Yield: 0.833 g, 77%. Microanalytical data:
Anal. Calc. for C61H49ClNP3RuS2: C, 67.24; H, 4.53; N, 1.29. Found:
C, 67.22; H, 4.56; N, 1.30%. 1H NMR (d ppm): 8.58 (dd, 7.2 Hz, 1 H),
7.58 (dd, 6.8 Hz, 1 H), 7.28 (td, 7.4 Hz, 1 H), 7.22 (td, 7.6 Hz, 1 H),
7.06–7.30 (br.m, PPh3). 31P{1H} NMR (d ppm): 49.62 (s, PPh3),
and 44.78 (s, PPh3). IR (KBr pellet, cmꢀ1): 1640 (s), 1582 (s),
1478 (s), 1426 (s), 1368 (m), 1174 (m), 1127 (s), 1086 (m), 746
15 543/6865 [Rint = 0.0210], R (all) = 0.0398, R(I > 2
r
wR2 = 0.0883, wR2 [I > 2 (I)] = 0.0864, GOF = 1.074.
r
Complex 2. Formula = C43H37Cl3NO4P2RuS2, Mr = 965.27, tri-
ꢀ
clinic space group P1, a = 9.2816(3), b = 11.4133(3), c = 22.1580
(7),
Z = 2, Dc = 1.490,
collected/unique 15 773/7523 [Rint = 0.0397],
R(I > 2 (I)) = 0.0777, wR2 = 0.2372, wR2
GOF = 1.002.
a
= 80.765(2), b = 78.780(2),
c = 69.176(2), V = 2141.32(12),
l
= 0.647, T (K) = 120(2), k = 0.71073, Reflections
R
[I > 2
(all) = 0.1066,
(I)] = 0.2237,
r
r
(m), 695 (s), 514 (s), 288
(1280), 357 (14 200), 316 (38 600), 242 (39 200).
m(Ru–Cl). UV–Vis. [kmax, nm (e)]: 437
Complex 4. Formula = C42H36N4P2RuS4, Mr = 888.00, Monoclinic
space group C2/c, a = 35.8089(8), b = 11.5091(2), c = 21.0986(5),
2.2.7. Synthesis of [Ru(CO)Cl(
j
1-P-N-PPh2Py)2(HL1)]ꢁCH2Cl2
7
b = 100.9212, V = 8537.8(3), Z = 8, Dc = 1.382,
120(2), k = 0.71073, Reflections collected/unique 30 552/7515
[Rint = 0.0572], R (all) = 0.0657, R(I > 2 (I)) = 0.0387, wR2 = 0.1323,
wR2 [I > 2 (I)] = 0.1276, GOF = 1.019.
l = 0.672, T (K) =
A mixture of [Ru(CO)Cl(PPh3)2(HL1)] (0.1 g, 0.11 mmol) and
PPh2Py (0.58 g, 0.22 mmol) in dichloromethane (25 mL) were stir-
red at room temperature for 16 h. Slowly, it dissolved and gave a
clear yellow solution. It was filtered to remove any solid impurities
and concentrated to half its volume. The concentrated solution was
saturated with petroleum ether (40–60 °C) and left for slow crys-
tallization in a refrigerator. Slowly, yellow microcrystalline prod-
uct separated which was filtered, washed with diethyl ether and
dried in vacuo. Yield: 0.632 g, 77%. Microanalytical data: Anal. Calc.
for C39H33Cl3N4OP2RuS2: C, 51.63; H, 3.67; N, 6.18. Found: C, 51.36;
H, 3.46; N, 6.52%. 1H NMR (d ppm): 3.08 (s, 3H, CH3), 8.42 [d, 1H,
H6 py (P)], 7.90 (m, 1H, H3 py (P)], 7.80–7.66 [m, 4H, H2 Ph (P)],
7.24 [m, 1H, H5 py (P)], 6.68–7.25 [m, 20H, Ph (PPh2Py)], 7.26–
7.04 (br. m, 20H, (PPh2Py)]. 31P{1H} NMR (d ppm): 48.72 (s,
PPh2Py). IR (KBr pellet, cmꢀ1): 1939 (s), 1656 (s), 1565 (s), 1486
(s), 1427 (s), 1378 (m), 1184 (m), 1127 (s), 1094 (m), 744 (m),
r
r
Complex 7. Formula = C39H33Cl3N4OP2RuS2, Mr = 907.19, tri-
ꢀ
clinic space group P1, a = 11.472(5), b = 13.606(5), c = 14.003(5),
a
= 80.390(5), b = 70.187(5),
Dc = 1.454, = 0.800, T (K) = 293, k = 0.71073, Reflections col-
lected/unique 28 123/9409 [Rint = 0.0220], R (all) = 0.0641, R(I >
(I)) = 0.0481, wR2 = 0.1537, wR2 [I > 2 (I)] = 0.1467, GOF = 1.146.
c = 85.134(5), V = 2026.5(14), Z = 2,
l
2r
r
3. Results and discussion
Reactions of the ruthenium complexes [RuH(CO)Cl(PPh3)3] and
[RuCl2(PPh3)3] with mercapto-functionalised thiadiazoles 2-mer-
capto-5-methyl-1,3,5-thiadiazole (HL1), 2-mercapto-4-methyl-5-
thiazoleacetic acid (HL2), 2-mercaptobenzothiazole (HL3) in meth-
anol under refluxing conditions afforded N,S-bonded neutral com-
plexes with the general formulations [Ru (CO)Cl(PPh3)2(HL)]
(HL = HL1, 1; HL = HL2, 2; HL = HL3, 3), [Ru(PPh3)2(HL1)2] 4 and
[RuCl(PPh3)3(HL)] (HL = HL2, 5; HL = HL3, 6), respectively in appre-
ciably good yields. Formation of complexes 1–6 involves replace-
ment of the coordinated hydride and one PPh3 from
[RuH(CO)Cl(PPh3)3] (1–3) and the chloro-group and one PPh3 from
[RuCl2(PPh3)3] (4–6) by N,S-donor sites after deprotonation from
the respective ligands. A simple scheme showing syntheses of
the complexes 1–6 is depicted in Scheme 3.
698 (s), 516 (s), 284
342 (9660), 250 (34 400), 235 (38 050).
m(Ru–Cl). UV–Vis. [kmax, nm (e)]: 419 (3990),
2.2.8. Synthesis of [Ru(j
1-P-N-PPh2Py)2(HL1)2] 8
Complex 8 was prepared following the above procedure for 7
except that [Ru(PPh3)2(HL1)2] (0.1 g, 0.11 mmol) was used in place
of [RuCl(CO)(PPh3)2(HL1)]. It isolated as an orange crystalline solid.
Yield: 0.731 g, 74%. Microanalytical data: Anal. Calc. for
C40H34N6P2RuS4: C, 53.98; H, 3.85; N, 9.44. Found: C, 53.96; H,
8.84; N, 9.42%. 1H NMR (d ppm): 2.48 (s, 3H, CH3), 8.38 [d, 1H,
H6 py (P)], 7.94 [m, 1H, H3 py (P)], 7.88–7.82 [m, 4H, H2 Ph (P)],
7.18 [m, 1H, H5 py (P)], 6.72–7.32 [m, 20H, Ph (PPh2Py)]. 31P{1H}
NMR (d ppm): 54.34 (s, PPh2Py). IR (KBr pellet, cmꢀ1): 1654 (s),
1535 (s), 1446 (s), 1436 (s), 1376 (m), 1174 (m), 1128 (s), 1096
Complexes 1 and 4 reacted with hetero-difunctional ligand
PPh2Py possessing both the ‘‘soft” phosphorus and ‘‘hard” nitrogen
donor sites to afford
j
1-P coordinated neutral complexes [RuCl-
(m), 748 (m), 694 (s), 512 (s). UV–Vis. [kmax, nm (
e)]: 412 (3690),
(CO)( j
j
1-P-PPh2Py)2(HL1)] (7) and [Ru(
1-P-PPh2Py)2(HL1)2] (8).
338 (9240), 244 (32 400).
Interestingly both the coordinated PPh3 in 1 and 4 were replaced
by PPh2Py, suggesting higher basicity of the latter in comparison
to the former. Synthesis of the complexes 7 and 8 are shown in
Scheme 4.
2.3. X-ray crystallography
2.3.1. Details of single crystal X-ray diffraction study
The complexes (1–8) are air-stable, non-hygroscopic crystalline
solids soluble in halogenated solvents like dichloromethane, chlo-
roform, insoluble in benzene, hexane, n-pentane, diethyl ether and
petroleum ether. Characterization of the complexes have been
achieved by standard spectroscopic techniques (IR, 1H and
31P{1H} NMR, electronic spectral, and electrochemical studies) as
well as elemental analyses. All the complexes gave satisfactory ele-
mental analyses. Analytical and spectral data of these complexes
corresponded to mononuclear complexes in which the ligands
Crystals suitable for single X-ray diffraction analyses for 1, 2, 4
and 7 were obtained from CH2Cl2/petroleum ether (40–60 °C) at
room temperature by the slow diffusion method. Preliminary data
on space group and unit cell dimensions as well as intensity data
were collected on an OXFORD DIFFRACTION XCALIBUR-S0 diffrac-
tometer using graphite-monochromatized Mo K
a radiation. The
structures were solved by direct methods and refined by
SHELX-97.[30] Non-hydrogen atoms were refined with anisotropic

P. Kumar et al. / Journal of Organometallic Chemistry 695 (2010) 994–1001
997
CO
PPh3
Cl
PPh3
Ru
S
N
O
CO
Ru
PPh3
N
CO
PPh3
N
OH
Cl
S
(2)
Cl
N
Ru
S
PPh3
PPh3
S
S
S
HL2
(1)
HL1
HL3
(3)
[RuHCl(CO)(PPh3)3]
[RuCl2(PPh3)3]
HL1
N
HL3
S
HL2
N
PPh3
N
PPh3
N
Cl
S
Ru
Ru
S
PPh3
PPh3
N
PPh3
PPh3
N
PPh3
S
Cl
Ru
S
S
O
S
(4)
(6)
PPh3
OH
S
(5)
HL1 = 2-mercapto-5-methyl-1,3,5-thiadiazol , HL2 = 2-mercapto-4-methyl-5-thiazoleacetic acid, HL3 = 2-
mercaptobenzothiazole . Reaction conditions = methanol, reflux, 8 h
Scheme 3.
CO
N
PPh2Py
N
S
PPh2
N
Cl
6
5
Complex 2, DCM
Stirring, 16 h
Ru
N
Complex 1, DCM
Stirring, 16 h
N
PPh2Py
PyPh2P
3
N
S
Ru
S
N
4
S
PyPh2P
PPh2Py
(7)
S
S
(8)
Scheme 4.
(HL1–HL3) are bonded to metal centre through both the S,N-donor
sites.
HL1–HL3 after deprotonation to ruthenium in neutral chelating
mode. An interesting feature of 1H NMR spectra of the complexes
1–6 is absence of resonances associated with S–H protons in the
aliphatic region (ꢂ4.5 ppm). Absence of this signal suggested that
exocyclic sulfur from HL1–HL3 along-with nitrogen donor atoms
are involved in coordination with metal centre ruthenium. The aro-
matic protons of the coordinated triphenylphosphine resonated as
broad multiplets at ꢂd 7.02–7.38 ppm. 1H NMR spectra of 1, 4, 7
and 8 exhibited singlets at d 2.50, 2.38, d 3.08 and 2.48 ppm,
respectively, assignable to the chemically equivalent methyl pro-
tons. These signals exhibited downfield shift in comparison to
the uncoordinated HL1 (d 2.35 ppm) and may be attributed to the
linkage of HL1 to metal centre ruthenium. 1H NMR spectra of 3
and 6 displayed signals associated with coordinated HL3 at 8.61
(dd, 7.6 Hz, 1 H), 7.67 (dd, 7.8 Hz, 1 H), 7.33 (td, 7.8 Hz, 1 H),
7.24 (td, 7.6 Hz, 1 H). The down field shift in the position of signals
suggested coordination of HL3 to the metal centre through both S,
and N donor sites.
Formation of 1–8 has been supported by infra red spectral stud-
ies. Bands associated with m(C@N), m(C@S) and m(C„O) in the IR
spectra of complexes 1–3 and 7 (ꢂ1433, 1131, 1927 cmꢀ1, 1;
1430, 1130, 1930 cmꢀ1, 2; 1435, 1131, 1927 cmꢀ1, 3 and 1427,
1127, 1939 cmꢀ1, 7) displayed appreciable shifts in comparison
to uncoordinated ligands (HL1–HL3) and the precursor complex.
Shifting in the position of bands suggested linkage of respective li-
gands to the metal centre. Similarly, bands associated with m(C@N)
and m(C@S) were also displayed in the infra red spectra of 4, 5, 6,
and 8 [ꢂ1432 and 1136 cmꢀ1, 4; 1429 and 1128 cmꢀ1, 5; 1426
and 1127 cmꢀ1, 6; 1436 and 1128 cmꢀ1, 8]. Shift in the position
of these bands in comparison to the respective ligands suggested
their interaction with the metal centre.
3.1. 1H and 31P{1H} NMR spectral studies
1H and 31P{1H} NMR spectral data summarized in the experi-
mental section strongly supported coordination of the ligands
31P{1H} NMR spectra of the complexes 1 and 4 displayed sing-
lets at d 40.72 and d 42.24 ppm assignable to 31P nuclei of the coor-

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P. Kumar et al. / Journal of Organometallic Chemistry 695 (2010) 994–1001
dinated triphenylphosphine. Further, the presence of a singlet sug-
gested that both the 31P nuclei in these complexes are trans dis-
posed. 31P in the in the complexes 7 and 8 resonated at d 48.72
and 54.34 ppm, respectively. It exhibited a downfield shift in com-
parison to their precursors 1 and 4. This shift may be attributed to
the presence of strong donor PPh2Py (donor ability increases in the
order PPh3 < PPh2Py < PPhPy2 < PPy3) in comparison to PPh3. The
31P nuclei in 3 and 6 resonated as singlets at d 39.85 and d 49.62,
44.78 ppm. One can see that the complex 6 exhibited two singlets
owing to presence of both cis and trans phosphines ligands in this
complex.
3.2. Electronic spectral studies
Electronic absorption spectra of the complexes 1–8 were ac-
quired in dichloromethane (10ꢀ4 M) at room temperature and
resulting data is summarized in the experimental section and spec-
tra of 1, 2, 5 and 7 is depicted in Fig. 1. Complexes 1–8 displayed
intense transitions in the UV–Vis region. Analogous general trend
has been observed in the electronic absorption spectra of all the
complexes under study. On the basis of its intensity and position
Fig. 2. Cyclic voltammogram of complex 1.
tron-transfer process. It is observable that complexes 1 and 7
exhibited higher oxidation potential in comparison to 4. It may
be attributed to the presence of an additional
p-acceptor ligand
(CO) in 1 and 7. Similar observation have been made in other com-
plexes RuCl2(CO)(PR3)3 and RuCl2(CO)2(PR3)2 [37]. As expected,
p-acceptors present in the carbonyl complexes leads
to higher oxidation potential.
lowest energy absorption bands in the visible region at ꢂ485–
*
additional
437 and 409–357 nm have been tentatively assigned to Md
p?L
metal to ligand charge transfer transitions (MLCT). The bands in
high-energy side at ꢂ235–260 nm have been assigned to intra-li-
gand
p ? p p
*/n ? * transitions.[32–36] One can see that coordina-
3.4. X-ray crystallography
tion of the ligands through both S and N donor sites resulted to a
blue shift in the position of Md
* transitions. It may be attributed
p
?L
Structure of the complexes 1, 2, 4, and 7 have been determined
crystallographically. Mercury views at 30% thermal ellipsoid prob-
ability along-with atom numbering scheme is shown in Figs. 3–6.
Details about data collection, solution and refinement are summa-
rized in Section 2 and important geometrical parameters are sum-
marized below the respective figures. Molecular structure of 1, 2
and 7 displayed distorted octahedral geometry about the ruthe-
nium, which is completed by N(1) and S(1) from mercapto-thi-
adiazoles (HL1–HL2), P(1) and P(2) from PPh3 (1 and 2), or PPh2Py
(7), carbonyl carbon [C(1), 1; C(40), 2 and C(6), 7] and Cl(1). In
complex 4, it is completed by N(1), N(2), S(1) and S(2) from the
mercapto-thiadiazoles (HL1) and P(1) and P(2) from the coordi-
nated PPh3. The N(1)–Ru(1)–S(1) angles are 66.8(6)°, 73.1(19)°
and 66.07(11)°, respectively in 1, 2 and 7, while in complex 4,
the angles N(1)–Ru(1)–S(2) and N(3)–Ru(1)–S(4) are essentially
to the formation of strained four membered chelate complexes.
3.3. Electrochemistry
Electrochemical properties of 1, 4, and 7 have been studied by
cyclic voltammetry in dichloromethane using 0.1 M tetrabutylam-
monium perchlorate (TBAP) as supporting electrolyte. Potential of
the Fc/Fc+ couple under the experimental conditions was 0.10 V
(80 mv) vs. Ag/Ag+. Representative voltammogram for 1 is depicted
in Fig. 2. Complexes 1, 4 and 7 in its cyclic voltammogram exhib-
ited an oxidative response at 0.73 (74), 0.38 (54) and 0.78 (64) V,
respectively which has been assigned to RuII/III oxidations. This oxi-
dation is reversible and characterized by a peak-to-peak separation
(
D
Ep) of ꢂ100 mV and the anodic peak current (ipa) is almost equal
to the cathodic peak current (ipc) expected for a reversible one elec-
Fig. 3. Molecular structure of the complex 1 and selected bond lengths (Å) and
angles (°): Ru1–C1 1.850(3), Ru1–N1 2.154(2), Ru1–P1 2.3806(11), Ru1–P2
2.3880(11), Ru1–Cl1 2.3896(9), Ru1–S1 4457(9), S1–C2 1.724(3), N1–Ru1–C1
172.8(10), C1–Ru1–P1 89.1(10), C1–Ru1–P2 90.7(10), N1–Ru1–P1 90.1(7), N1–
Ru1–P2 89.5(7), P1–Ru1–P2 175.6(3), N1–Ru1–S1 66.8(6).
Fig. 1. UV–Visible spectra of complexes 1, 2, 5 and 7.

P. Kumar et al. / Journal of Organometallic Chemistry 695 (2010) 994–1001
999
Fig. 6. Molecular structure of complex 7 and selected bond length (Å) and angles
(°): Ru01–CC„O 2.240(4), Ru01–N1 2.117(4), Ru01–P1 2.3804(14), Ru01–P2
2.3851(15), Ru01–Cl2 2.406(2), Ru01–S1 2.4968(14), S1–C35 1.719(5), N1–Ru01–
CC„O 173.6(6), P1–Ru01–CC„O 88.9(5), P2–Ru01–CC„O 89.9(5), N1–Ru01–P1
90.6(12), N1–Ru01–P2 89.8(12), P1–Ru01–P2 174.6(4), N1–Ru01–S1 66.07(11).
Fig. 4. Molecular structure of the complex 2 and selected bond length (Å) and
angles (°): Ru1–C6 1.827(7), Ru1–N1 2.162(5), Ru1–P1 2.3638(18), Ru1–P2
2.3713(18), Ru1–S1 2.413(3), Ru1–Cl1 2.462(3), S1–C2 1.822(12), N1–Ru1–C6
175.3(3), C6–Ru1–P1 90.7(2), C6–Ru1–P2 89.5(2), N1–Ru1–P1 90.2(15), N1–Ru1–
P2 89.7(15), P1–Ru1–P2 176.9(7), N1–Ru1–S1 73.1(19).
Fig. 7. Intermolecular association of coordinated 2-mercapto-5-methyl-1,3,5-thia-
diazol (HL1) ligands in the crystal of complex 1. Angles between the planes defined
by S(2)–S(1)–S(1) 55.75°, C(2)–S(2)–S(1) 86.29°, C(2)–S(1)–S(1) 82.26°.
Fig. 5. Molecular structure of the complex 4 and selected bond length (Å) and
angles (°): Ru1–N1 2.084(4), Ru1–N3 2.069(4), Ru1–P1 2.2940(14), Ru1–P2
2.2838(14), Ru1–S2 2.5456(14), Ru1–S4 2.5466(14), N1–Ru1–P1 98.5(12), N1–
Ru1–P2 94.4(12), N3–Ru1–P1 92.3(12), N3–Ru1–P2 95.5(12), P1–Ru1–P2 103.8(5),
N1–Ru1–S2 66.03(12), N1–Ru1–S4 101.1(12), N3–Ru1–N1 162.9(17), P1–Ru1–S2
162.9(5), P2–Ru1–S2 85.3(5), P1–Ru1–S4 87.1(5), P2–Ru1–S4 159.4 (5).
equal and 66.03(12)° and 66.1(12)°, respectively. It suggested in-
ward bending of mercapto-thiadiazole moiety towards metal cen-
tre and smaller value of this angle in comparison to ideal value of
90° is probably source of the observed distortion.
The angles P(1)–Ru–P(2) in 1, 2 and 4 are 175.6(3)°, 176.9(7)°,
and 103.8(5)°, respectively and associated P(1)–Ru(01)–P(2) angle
in 7 is 174.6(4)°. The P–Ru–P angles suggested that triphenylphos-
phine ligands are trans disposed in 1, 2 and 7, while it adopted a cis
arrangement in 4. The Ru(1)–P(1) and Ru(1)–P(2) bond distances
are 2.3806(11) and 2.3880(11) Å in 1, while it is 2.2940(14) and
2.2838(14) Å in 4. These are essentially equivalent and comparable
to the values reported in other related complexes [38–41]. The
Fig. 8. Face-to-face p–p interaction leading to supramolecular motif in complex 1.

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P. Kumar et al. / Journal of Organometallic Chemistry 695 (2010) 994–1001
Fig. 9. Hydrogen-bonding intermolecular interactions between carboxylate oxygen and water molecules leading to regular hexamer motif in 6.
ruthenium to carbonyl carbon Ru(1)–C(1) bond distances are
1.850(3), 1.827(7) and 2.240(4) Å, respectively in 1, 2 and 7. It falls
in the range for Ru–C carbonyl bond lengths [40,42,43]. The Ru(1)–
S(1) bond distances are 2.4457(9), 2.413(3) and 2.4968(14) Å, in 1,
2, and 7, while Ru(1)–S(2) and Ru(1)–S(4) bond distances in 4 are
2.5456(14) and 2.5466(14) Å. These are normal for Ru(II)–S bond
distances [41–43]. The S–C bond distances in 1, 2 and 7 are in
the range of 1.82–1.71 Å [S(1)–C(2) 1.724(3), 1; S(1)–C(2)
1.822(12), 2; S(1)–C(35) 1.719(5) Å, 7] and it is 1.716(6) Å in 4. It
is well established that the S–C distances in thiol form falls in
the range of 1.83–1.70 Å [41]. Therefore, coordinated mercapto
groups in 1, 2, 4, and 7 are present in thiol forms.
It is interesting to note that two distinct molecules in the asym-
metric unit of complex 1 are apparently linked intermolecularly by
the unusual arrangement of two sulfur atoms from 2-mercapto-5-
methyl-1,3,5-thiadiazole (Fig. 7). The secondary bonding is clearly
weak [S(1)ꢁꢁꢁS(1) 3.461, S(1)ꢁꢁꢁS(2) 3.461 Å; covalent radii sums S–S
2.04 Å], however it should be noted that the complex is sterically
cluttered and this may be limiting the interaction. Intermolecular
interactions in the solid state between sulfur and nitrogen or sulfur
in sulfur–nitrogen containing compounds are uncommon and in
particular, thiadiazoles as a class often show this feature, however
it is less common in coordination complexes. Weak interaction
ogy, New Delhi, India (Grant No. SR/SI/IC-15/2007). Also, we are
thankful to Prof. P. Mathur, In-charge, National Single Crystal X-
ray Diffraction Facility, Indian Institute of Technology, Mumbai
for providing single crystal X-ray data.
Appendix A. Supplementary material
CCDC 753774, 753775, 753776, and 753777 contains the sup-
plementary crystallographic data for complexes 1, 2, 4, and 7.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif. Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2009.12.006.
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Acknowledgements
We gratefully acknowledge financial support from the Depart-
ment of Science and Technology, Ministry of Science and Technol-

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