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 (CH 3 CN)] 2 (PF 6 ) 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 (CH 3 CN)-[Ru(bpy)(CO) 2 (CH 3 CN) 2 ] 2+ or trans (Cl)-[Ru(bpy)(CO) 2 Cl 2 ] 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 (CH 3 CN)-[Ru(bpy)(CO) 2 (CH 3 CN) 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 CO 2 into CO with a 98% electrical yield at a low potential in hydro-organic or pure aqueous electrolytes.