Reaction of two dioxime ligands, viz. dimethylglyoxime (H(2)dmg) and diphen
ylglyoxime (H(2)dpg), (abbreviated in general as H2L, where H stands for th
e oxime protons) with [Ru( PPh3)(3)Cl-2] in 1:1 mole ratio affords complexe
s of type [Ru(PPh3)(2)(H2L)Cl-2]. Structure of the [Ru(PPh3)(2)(H(2)dpg)Cl-
2] complex has been solved by X-ray crystallography. The coordination spher
e around ruthenium is N2P2Cl2 with the two PPh3 ligands in trans and the tw
o chlorides in cis positions. Reaction of the dioxime ligands with [Ru(PPh3
)(3)Cl-2] in 2:1 mole ratio in the presence of a base affords complexes of
type [Ru(PPh3)(2)(HL)(2)]. Structure of the [Ru(PPh3)(2)(Hdmg)(2)] complex
has been solved by X-ray crystallography. The coordination sphere around ru
thenium is N4P2 with the two PPh3 ligands in trans positions. Reaction of t
he [Ru(PPh3)(2)(H(2)dpg)Cl-2] complex with a group of bidentate acidic liga
nds, viz. picolinic acid (Hpic), quinolin-8-ol (Hq) and 1-nitroso-2-naphtho
l (Hnn), (abbreviated in general as HL', where H stands for the acidic prot
on) in the presence of a base affords complexes of type [Ru(PPh3)(2)(H(2)dp
g)(L')](+) isolated as perchlorate salts. All the complexes are diamagnetic
(low-spin d(6), S = 0) and in dichloromethane solution show several intens
e MLCT transitions in the visible region. Cyclic voltammetry on all the com
plexes shows a reversible ruthenium(II)-ruthenium(III) oxidation within 0.3
6-0.98 V versus SCE followed by a quasi-reversible ruthenium(III)-ruthenium
(IV) oxidation within 0.94-1.60 V versus SCE. (C) 2001 Elsevier Science B.V
. All rights reserved.