Nonclassical redox reactions involve bond formation at a metal center facilitated by oxidation of the surrounding ligands. In order to discourage ligand dissociation upon oxidation, a novel tripodal tris(aminophenol) ligand, tris(4-methyl-2-((3',5'-di-tert-butyl-2'-hydroxyphenyl)amino)phenyl)amine, MeClampH6, was prepared. Its diamagnetic molybdenum(VI) complex features a capped octahedral geometry with significant π donation from the three redox-active amidophenolate orbitals. Each amidophenolate displays a calculated metrical oxidation state of about -1.5 and a π bond order of 2/3. Analysis of the optical bands representing the a (πnb) → e (dπ*) and e (πb) → e (dπ*) transitions in neutral (MeClamp)Mo gives an estimate of 40 kcal/mol stabilization per π bond. The titanium(IV) analogue (MeClamp)Ti (shown below) is a diamagnetic, unsymmetrical κ6 complex with a doubly oxidized ligand and weaker π bonding. Evidence of catalytic oxidation of benzylic and aliphatic alcohols to aldehydes under aerobic conditions by (MeClamp)Ti will be presented.

Electronic structure and reactivity of d0 Mo and Ti complexes of a tris-aminophenolate ligand

249th National Meeting (2015)

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