706
G. Venkatachalam, R. Ramesh / Inorganic Chemistry Communications 9 (2006) 703–707
g^ = 2.95–2.28 and gi = 1.85–1.54 with gav = 2.44–2.12
(Table 2) which is derived from hgiꢁ ¼ ½1=3 g2x þ 1=3 gy2þ
1=3 g2z ꢂ1n2. In the solution spectra of the complexes at
LNT, the resolution was improved and a three line spec-
trum showing in the range gx = 2.91–2.82; gy = 2.62–2.36;
gz = 1.85–1.54 is exhibited. The presence of three different
‘g’ values indicates rhombic distortion in the complexes.
The rhombicity of the spectra reflects the asymmetry of
the electronic environment around ruthenium in the com-
plexes. Cyclic voltammogram of these complexes exhibit
one reversible oxidation (DEP = 70–80 mV) and one
quasi-reversible reduction (DEP = 90–110 mV) couples
an active species. All the reactions are believed to proceed
via metal hydrides as intermediate proposed in the litera-
ture [7a,11,13,23]. The catalytic activity of present com-
plexes is comparatively lower than that of the
ruthenium(III) Schiff base complexes of [ONNO]-type
mediated transfer hydrogenation of ketones reported by
us [18a].
In conclusion, we have synthesized and characterized a
series of ruthenium(III) bis-bidentate Schiff base complexes
and one of the complexes was utilized and gained as a cat-
alyst for the transfer hydrogenation of imines to amines.
and the E1/2 lies in the range +0.62 to +0.91 V (RuIV/RuIII
)
Acknowledgements
and ꢀ0.45 to ꢀ0.13 V (RuIII/RuII), respectively, versus Ag/
AgCl (Table 2). Both reversible oxidation and quasi-revers-
ible reduction processes are readily assigned as successive
metal centered couples only.
Financial support from the Council of Scientific and
Industrial Research (CSIR), New Delhi (Grant No. 01
(1725)/02/EMR-II) is gratefully acknowledged. One of
the authors (G.V) thank CSIR for the award of senior re-
search fellowship (SRF).
The catalytic transfer hydrogenation of imines to amines
by one of the synthesized ruthenium(III) bis-bidentate
Schiff base complexes [RuCl(PPh3)(L1)2] was performed
in the presence of isopropanol/KOH (Scheme 2) and the
results of this study are listed in Table 3.
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[19] General procedure for preparing ligands: The 5-chloro-4-methyl-2-
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such as aniline, p-chloroaniline, p-toluidine and p-nitroaniline was
Venkatachalam, Galmari
