Reductions of {RuNO}6-Type Nitrosyls. Characteristics of the Two-Electron Reduction Species Isolated as a Complex Having a Formally Negatively Charged <i>μ</i>-Nitrosyl ({RuNO}8–{RuNO}8) and the One-Electron Reduction Species Generated Electrochemically ({RuNO}7)

Abstract

Abstract The reaction between cis-[Ru(NO)(H2O)(bpy)2]3+ ({RuNO}6) and formic acid gives [{Ru(μ-NO)}2(bpy)4]2+ (2) ({RuNO}8–{RuNO}8), along with some other products species: cis-[Ru(NO)(OCHO)(bpy)2]2+ (1)({RuNO}6), and cis-[Ru(OCHO)(H2O)(bpy)2]+. The μ-nitrosyl complex (2) consists of two cis-Ru(bpy)2fragments connected by two formally negatively charged bridging nitrosyl ligands. Electrochemical study of the complex shows that two successive one-electron oxidation waves to give [{Ru(μ-NO)}2(bpy)4]4+({RuNO}7–{RuNO}7) are found. The generated two-electron oxidation species is disintegrated to afford a one-electron reduction species, cis-[Ru(NO·)(CH3CN)(bpy)2]2+ ({RuNO}7), along with a small amount of an unexpected nitro species, cis-[Ru(NO2)(CH3CN)(bpy)2]+. The characteristics of electrochemically generated one-electron reduction species cis-[Ru(NO·)X(bpy)2](n−1)+ ({RuNO}7) (X = H2O, OCHO) are investigated in the connection. During the degradation process of the one-electron reduction species, a nitrosyl-to-nitro conversion was found to proceed in cis-[Ru(NO·)(H2O)(bpy)2]2+, via the formation of cis-[Ru(NO·) (CH3CN)(bpy)2]2+ mentioned above; this is the first observation which explains the electrochemically-induced nitrosyl-to-nitro conversion observed in the reduction process of {RuNO}6-type complexes.