Synthesis, Structure, and Physicochemical Characterizations of a New Cationic Ruthenium(I)−Ruthenium(I) Tetracarbonyl Bipyridine Dimer Precursor for the Electrochemical Synthesis of an Organometallic Ruthenium(0) Polymer

The synthesis and structure of the Ru(I) dimer [Ru(bpy)(CO)2(CH3CN)]2(PF6)2 (1; bpy = 2,2‘-bipyridine) are described. The electrochemical properties of this complex have been examined. The irreversible two-electron reduction of 1 gives [Ru(bpy)(CO)2] n polymer film on the electrode surface. The physicochemical properties of this metal−metal bond based polymer equal those of the polymers formed from the reduction of trans(CH3CN)-[Ru(bpy)(CO)2(CH3CN)2]2+ or trans(Cl)-[Ru(bpy)(CO)2Cl2] monomer complexes previously described. The Ru(0) polymer can be oxidized in a stepwise manner, leading first to the Ru(I) dimer 1 and then to the Ru(II) monomer 2: cis(CH3CN)-[Ru(bpy)(CO)2(CH3CN)2]2+. On the other hand, the dimer 1 exhibits an irreversible two-electron oxidation, leading to the same Ru(II) monomer (2). Carbon electrodes modified with the polymer resulting from 1 catalyze the electrochemical reduction of CO2 into CO with a 98% electrical yield at a low potential in hydro-organic or pure aqueous electrolytes.