Synthesis, characterization and redox properties of ruthenium(ll) dithiocarbonato complexes having 2,2'-bipyridine coligands

379-384A group of stable new ruthenium (II) mixed tris-chelated complexes of the type [Ru(bpy)2(L)]CIO4.2H2O, [bpy:2,2'-bipyridine; L:anionic form of KSSCOR, R=Me, Et, "pr, "Bu] have been prepared by the reaction of Ru(bpy)2CO3 with KSSCOR in methanol. The complexes are essentially diamagnetic and behave as 1:1 electrolytes in CH3CN. All the complexes show metal to ligand charge transfer transitions in the visible region (495-450 nm). The complexes do not exhibit any emission spectra at room temperature. The geometry of the complexes has been assessed by high-resolution 1H NMR spectroscopy. Reductions of coordinated bpy units are observed in the range -1.5 and -1.8 V, respectively. All the complexes exhibit one reversible ruthenium (II)-ruthenium(lll) oxidation couple near 0.7 V (versus SCE) in acetonitrile solution at platinum electrode. Coulometric oxidation of [Rull(bpy)2(L)]+ at 0.9 V (vs. SCE) as well as-chemical oxidation by Ce(IV) in 0.1M aqueous HCIO4 produces unstable green coloured ruthenium(III) congener of [RuII(bpy)2(L)]+ i.e, [RuIII(bpy)2(L)]+2.The presence of trivalent ruthenium in the oxidized solution is evidenced by the rhombic EPR spectrum with ‘g values (g1 =2.720, g2=2.370 and g3= 1.700)