Proton‐Coupled Redox Chemistry, Oxidative Reactivity, and Electronic Characterization of Aqua‐, Hydroxo‐, and Oxo‐Triruthenium Clusters

Abstract

AbstractThe pH‐dependent electronic and electrochemical properties of a series of triangular μ3‐oxo‐centered trinuclear clusters of the type [Ru3O(Ac)6(py)2(OHx)]n (Ac = acetate; py = pyridine; x = 0, 1, or 2; where the formal oxidation states on the metal ions range from +II to +IV) have been investigated with emphasis on the elucidation of the successive proton‐coupled redox processes spanning the interconvertible aqua‐ (x = 2), hydroxo‐ (x = 1), and oxo‐ (x = 0) forms, from which the complete Pourbaix diagram has been proposed. From the spontaneous slow coupling reaction of the monomeric cluster in its deprotonated (oxo) form at high pH, the μ‐oxo‐bridged cluster dimer (i.e. {(py)2(Ac)6ORu3}‐O‐{Ru3O(Ac)6(py)2}) has been isolated and fully characterized by spectroelectrochemistry as well. A further understanding of the underlying electronic interactions across the various oxidation and protonation states, and the role of such phenomena in the activation of the Ru–O bonding system in oxygen‐transfer catalysis, have also been explored. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)