High-valent metal-oxo complexes have been implicated as key intermediates in catalytic reactions for a number of biological systems. In heme enzymes, one key factor for tuning metal-oxo reactivity is the axial ligand coordinated trans to the oxo group. This presentation will discuss the influence of mono-anionic ligands on the reactivity of a manganese(V)-oxo complex, (TBP8Cz)MnV(O) (TBP8Cz = octakis(4-tert-butylphenyl(corrolazinato)). In the case of the anionic donor CN-, structural evidence for a 6-coordinate complex was obtained by X-ray absorption spectroscopy (XAS). Analysis of the oxygen-atom-transfer (OAT) reactivity in the presence of CN- and other anionic donors, together with comparison of the reactivity of the parent complex, (TBP8Cz)MnV(O), reveals dramatic rate enhancements for sulfoxidation induced by the addition of X-. The kinetic data, including a Hammett study and Eyring analysis, reveal important trends in reactivity and mechanistic insights. DFT calculations were performed on the six-coordinate complexes to assess the ground state configuration and determine the origins of the rate enhancements.

Addition of monoanions to a manganese(V)-oxo complex results in dramatic rate enhancements for oxygen-atom-transfer

248th National Meeting (2014)

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