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T. Mathur et al. / Polyhedron 25 (2006) 2503–2512
Two isomers, green tcc-Ru(30-PyaiR)2Cl2 and blue-violet
ctc-Ru(30-PyaiR)2Cl2 are also characterised.
The microanalytical data of the complexes are as fol-
lows: Anal. Calc. for C18H18N10Cl2Ru (4b): C, 39.47; H,
3.39; N, 25.71. Found: C, 39.56; H, 3.30; N, 25.64%. Anal.
Calc. for C22H22N10Cl2Ru (4c): C, 41.74; H, 3.88; N, 24.30.
Found: C, 41.81; H, 3.83; N, 24.39%. Anal. Calc. for
C30H26N10Cl2Ru (4d): C, 51.65; H, 3.66; N, 20.00. Found:
C, 51.58; H, 3.72; N, 20.06%. Anal. Calc. for C18H18N10-
Cl2Ru (5b): C, 39.50; H, 3.25; N, 25.70. Found: C, 39.56;
H, 3.30; N, 25.64%. Anal. Calc. for C22H22N10Cl2Ru
(5c): C, 41.78; H, 3.78; N, 24.30. Found: C, 41.81; H,
3.83; N, 24.39%. Anal. Calc. for C30H26N10Cl2Ru (5d): C,
51.65; H, 3.66; N, 20.00. Found: C, 51.58; H, 3.72; N,
20.06%.
4. Experimental
4.1. Materials and methods
3-Aminopyridine was purchased from Lancaster, UK.
Imidazole and all other organic chemicals and inorganic
salts were available from the Sisco Research Lab, Mum-
bai, India. Ru(CO)3(PPh3)2 was synthesized as in the
reported procedure [33]. For the solution spectral studies,
spectroscopic grade solvents were used from Lancaster,
UK. Microanalyses (C, H, N) were performed using a
Perkin–Elmer 2400 CHNO elemental analyzer. Spectro-
scopic measurements were carried out using the following
instruments: UV–Vis spectra, JASCO UV–Vis/NIR model
V-570; IR spectra (KBr disk, 4000–200 cmꢀ1), JASCO
FT-IR model 420; 1H NMR spectra in CDCl3 and
CD3CN Bruker 300 MHz FT-NMR spectrometers in the
presence of TMS as internal standard. Molar conduc-
tances (KM) were measured in a Systronics conductivity
meter 304 model using ca. 10ꢀ3 M solutions in DMSO.
Silver is measured gravimetrically. Emission was exam-
ined by a F-4500 Hitachi spectrofluorimeter at room tem-
perature (298 K) in MeCN under non-degassed
conditions.
4.1.3. Preparation of [Ru(CO)(PPh3)2(30-PyaiH)] (6a)
To a solution of [Ru(CO)3(PPh3)2] (0.200 g, 0.282
mmol) in MeCN (20 ml) was added 30–PyaiH (0.05 g,
0.289 mmol) in acetonitrile. The solution was stirred for
8 h. The yellow solution turned red. The solution was fil-
tered and evaporated slowly. Red coloured crystals devel-
oped after four days. The crystals were collected by
filtration, washed with cold water–acetonitrile (1:1, v/v)
and dried over CaCl2 in vacuo. The yield was 0.16 g
(78%). The microanalytical data of the complexes are as
follows: Anal. Calc. for C45H37N5OP2Ru (6a): C, 65.37;
H, 4.48; N, 8.47. Found: C, 65.29; H, 4.43; N, 8.39%. Anal.
Calc. for C46H39 C46H39N5OP2Ru (6b): C, 65.71; H, 4.64;
N, 8.33. Found: C, 65.66; H, 4.60; N, 8.27%. Anal. Calc.
for C47H41N5OP2Ru (6c): C, 66.04; H, 4.80; N, 8.20.
Found: C, 65.96; H, 4.76; N, 8.15%. Anal. Calc. for
C52H43 N5OP2Ru (6d): C, 68.12; H, 4.69; N,7.64. Found:
C, 68.06; H, 4.65; N, 7.58%.
4.1.1. Synthesis of the ligands 30-(pyridyazo)imidazole
Pyridylazoimidazole is a new class of unsymmetric bi-
heterocycle and has been synthesized by coupling the dia-
zonium salt of 3-aminopyridine with imidazole in Na2CO3
solution. N(1)-alkylation has been performed by the
reported method using RX in dry THF in the presence of
NaH. The chromatographic process has been used to pur-
ify the N(1)-alkylated product. Detailed procedures have
been reported earlier [26].
4.1.4. Oxidation of [Ru(CO)(PPh3)2(30-PyaiMe)] by Cl2
(6b)
To a MeCN solution (15 ml) of [Ru(CO)(PPh3)2(30-
PyaiMe)] (0.2 g, 0.24 mmol) 3 ml of Cl2 saturated MeCN
solution was added, dropwise, and stirred. The solution
colour changed immediately from brown red to orange
red. The solution was stirred for 30 min and then evapo-
rated in air to reduce its volume to half of its original
value. Upon addition of a 2 ml saturated solution of
NaClO4 to this solution, a dark coloured compound pre-
cipitated. This was then filtered, washed with water and
dried over CaCl2. The CH2Cl2 solution of the dry mass
was chromatographed over silica gel prepared in petro-
leum ether (60–80 ꢁC). A deep orange red band was eluted
by MeCN–toluene (1:3, v/v) and a black mass was
attached on the column head. The solution was evapo-
rated via rotary evaporation and the solid product was
recrystallised by diffusion of a CH2Cl2 solution to hexane.
Yield, 0.14 g, 60%.
4.1.2. Preparation and separation of tcc- and
ctc-[Ru(30-PyaiMe)2Cl2] (4 and 5)
A degassed dry ethanol (10 ml) solution of 3-PyaiMe
(0.25 g, 1.34 mmol) was added slowly using a pressure
equalising funnel to a green Ru(II) solution (prepared by
reduction of RuCl3 Æ 3H2O (0.17 g, 65 mmol) in 10 ml dry
ethanol and refluxed for 3 h under nitrogen environment).
The volume of the solution was reduced to half of its origi-
nal volume by nitrogen bubbling and was kept in refriger-
ator overnight. The precipitate so obtained was filtered and
washed with water, cold ethanol and finally with ether. It
was then dried over CaCl2. A CH2Cl2 solution of the dry
mass was chromatographed over silica gel prepared in
petroleum ether (60–80 ꢁC). A green band was eluted by
toluene–acetonitrile (9:1 v/v) and a blue violet band was
collected using toluene–acetonitrile (3:2 v/v). The solutions
were evaporated in air and crystalline products were iso-
lated in 35% and 20% yields.
The other compounds were prepared by an identical
procedure and the yield varied from 60% to 65%.
The microanalytical data of the complexes are as fol-
lows: Anal. Calc. for C45H37N5O5P2Cl2Ru (7a): C, 56.26;
H, 3.80; N, 7.17. Found: C, 56.19; H, 3.85; N, 7.28%. Anal.
Mathur
