title: Synthesis, characterization, and reactivity of cobalt(III)-oxygen complexes bearing a macrocyclic N-tetramethylated cyclam ligand.
abstract: Mononuclear metal-dioxygen species are key intermediates that are frequently observed in the catalytic cycles of dioxygen activation by metalloenzymes and their biomimetic compounds. In this work, a side-on cobalt(III)-peroxo complex bearing a macrocyclic N-tetramethylated cyclam (TMC) ligand, [Co(III) (15-TMC)(O2 )](+) , was synthesized and characterized with various spectroscopic methods. Upon protonation, this cobalt(III)-peroxo complex was cleanly converted into an end-on cobalt(III)-hydroperoxo complex, [Co(III) (15-TMC)(OOH)](2+) . The cobalt(III)-hydroperoxo complex was further converted to [Co(III) (15-TMC-CH2 -O)](2+) by hydroxylation of a methyl group of the 15-TMC ligand. Kinetic studies and (18) O-labeling experiments proposed that the aliphatic hydroxylation occurred via a Co(IV) -oxo (or Co(III) -oxyl) species, which was formed by OO bond homolysis of the cobalt(III)-hydroperoxo complex. In conclusion, we have shown the synthesis, structural and spectroscopic characterization, and reactivities of mononuclear cobalt complexes with peroxo, hydroperoxo, and oxo ligands.
authors.affiliation: Department of Bioinspired Science, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (South Korea).
authors.forename: Doyeon
authors.initials: D
authors.lastname: Kim
authors.forename: Jaeheung
authors.initials: J
authors.lastname: Cho
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Lee
authors.forename: Ritimukta
authors.initials: R
authors.lastname: Sarangi
authors.forename: Wonwoo
authors.initials: W
authors.lastname: Nam
keywords: aliphatic hydroxylation; bioinorganic chemistry; cobalt; macrocyclic ligands; oxygen
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