Mechanisms of the Oxidation of Monooxoruthenium(IV) to Dioxoruthenium(VI)

The purpose of this project is to investigate how a metal-oxo species can be generated from the reaction of a low-valent precursor metal complex with an oxygen donor. Metal-oxo species play important roles as catalysts for oxidation in both chemical and biological systems. There are two key steps in a catalytic cycle involving metal oxo species: (1) formation of metal oxo species (M=O) via reaction of an oxygen donor (XO) with a low-valent metal complex (M); (2) oxidation of substrates (S) by the metal oxo species, M=O + S = SO + M. Reaction (2) has been extensively studied but less is known about reaction (1), especially for those involving the biologically important oxidants H2O2 and alkyl hydroperoxides. These oxidants are also commonly used in chemical systems. Specifically the researchers would like to investigate the mechanisms of the formation of [O=RuVI(L)=O]2+ from [RuIV(L) =O]2+ by various oxidants. Ruthenium complexes are important catalysts for oxidation of various organic substrates. An understanding of the mechanisms of its formation would help in the design of more efficient catalysts. An ideal ligand L is the macrocyclic tertary amine ligand TMC (1,4,8,11- tetramethyl-1,4,8,11-tetraazacyclotetradecane). This ligand forms very stable [O=RuVI(L)=O]2+ and [RuIV(L)=O]2+ complexes with well defined redox potentials, which will facilitate kinetic and mechanistic studies.