Biomimetic Water Oxidation Catalyzed by a Binuclear Ruthenium (IV) Nitrido-Chloride Complex with Lithium Counter-Cations

Abstract

The lithium salt of the binuclear nitrido complex of ruthenium (IV) Li3(Ru2NCl8·2H2O) was synthesized. Using UV spectroscopy and voltammetry, we studied complex behavior in aqueous solutions. It was found that in dilute solutions of this compound, Cl− ions are replaced by H2O molecules, and the intra-sphere redox reaction between Ru (IV) and H2O, as well as the oxidation of water with the formation of oxygen and the acidic dissociation of coordinated water molecules also have been taking place. It was established by IR spectroscopy and ESI mass spectrometric analysis that not only the binuclear structure of the complex is preserved in acidic solutions, but also its dimerization product into the tetra-ruthenium dinitrido cluster Ru4N2O5+, which is a catalyst for the water oxidation reaction. The activity of the catalyst was TOF = 0.33 s−1, TON = 304.