Chemistry of ruthenium. Part 6. Bis(2,2′-bipyridine)(isonitrosoketonato)ruthenium(II) perchlorate monohydrate. Synthesis, spectra, and electrochemistry

Abstract

New ruthenium(II) complexes of type [Ru(bipy)₂(L)](ClO₄)·H₂O are formed by the reaction of [Ru(bipy)₂Cl₂] with HL and in one case by chelative nitrosation of ketones with [Ru(bipy)₂(NO)Cl]²⁺[HL = RC(NOH)C(O)R′, bipy = 2,2′-bipyridine]. These display metal-to-ligand charge-transfer transitions in the visible region (450–490 nm), a reversible Ru^III–Ru^II couple near 0.9 V versus s.c.e., and one or more ligand reduction couples below –I V. Trends of E₂₉₈° values for a group of related complexes are rationalised. The oxidised complex [Ru(bipy)₂(L)]²⁺ is unstable and has a ligand-to-metal charge-transfer transition near 600 nm. Its energy correlates linearly with E₂₉₈° of the Ru^III–Ru^II couple. In acetonitrile, [Ru(bipy)₂(L)]⁺ can be protonated to [Ru(bipy)₂(HL)]²⁺. The Ru^III–Ru^II couple of the protonated complex is at a higher (∼1.0 V) potential than that of [Ru(bipy)₂(L)]⁺. The chemistries of [Ru(bipy)₂(L)]⁺ and [RuX₂(HL)(L)] are compared.