Visible Light-Induced Oxidation of Alcohols by a Luminescent Osmium(VI) Nitrido Complex: Evidence for the Generation of PhIO + as a Highly Active Oxidant in the Presence of PhIO.

Although alcohols are readily oxidized by a variety of oxidants, their oxidation by metal nitrido complexes is yet to be studied. We report herein visible-light-induced oxidation of primary and secondary alcohols to carbonyl compounds by a strongly luminescent osmium(VI) nitrido complex ( OsN ). The proposed mechanism involves initial rate-limiting hydrogen-atom transfer (HAT) from the α-carbon of the alcohol to OsN* . Attempts to develop catalytic oxidation of alcohols by OsN* using PhIO as the terminal oxidant resulted in the formation of novel osmium(IV) iminato complexes in which the nitrido ligand is bonded to a δ-carbon of the alcohol. Experimental and theoretical studies suggest that OsN* is reductively quenched by PhIO to generate PhIO + , which is a highly active oxidant that readily undergoes α- and δ-C-H activation of alcohols.