Synthesis, structural, and spectroscopic characterization and reactivities of mononuclear cobalt(III)-peroxo complexes

Jaeheung Cho, Ritimukta Sarangi, Hye Yeon Kang, Jung Yoon Lee, Minoru Kubo, Takashi Ogura, Edward I. Solomon, Wonwoo Nam

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101 Scopus citations

Abstract

Metal-dioxygen adducts are key intermediates detected in the catalytic cycles of dioxygen activation by metalloenzymes and biomimetic compounds. In this study, mononuclear cobalt(III)-peroxo complexes bearing tetraazamacrocyclic ligands, [Co(12-TMC)(O2)]+ and [Co(13-TMC)(O 2)]+, were synthesized by reacting [Co(12-TMC)(CH 3CN)]2+ and [Co(13-TMC)(CH3CN)]2+, respectively, with H2O2 in the presence of triethylamine. The mononuclear cobalt(III)-peroxo intermediates were isolated and characterized by various spectroscopic techniques and X-ray crystallography, and the structural and spectroscopic characterization demonstrated unambiguously that the peroxo ligand is bound in a side-on η2 fashion. The O-O bond stretching frequency of [Co(12-TMC)(O2)]+ and [Co(13-TMC)(O2)]+ was determined to be 902 cm-1 by resonance Raman spectroscopy. The structural properties of the CoO 2 core in both complexes are nearly identical; the O-O bond distances of [Co(12-TMC)(O2)]+ and [Co(13-TMC)(O2)] + were 1.4389(17) Å and 1.438(6) Å, respectively. The cobalt(III)-peroxo complexes showed reactivities in the oxidation of aldehydes and O2-transfer reactions. In the aldehyde oxidation reactions, the nucleophilic reactivity of the cobalt-peroxo complexes was significantly dependent on the ring size of the macrocyclic ligands, with the reactivity of [Co(13-TMC)(O2)]+ > [Co(12-TMC)(O2)] +. In the O2-transfer reactions, the cobalt(III)-peroxo complexes transferred the bound peroxo group to a manganese(II) complex, affording the corresponding cobalt(II) and manganese(III)-peroxo complexes. The reactivity of the cobalt-peroxo complexes in O2-transfer was also significantly dependent on the ring size of tetraazamacrocycles, and the reactivity order in the O2-transfer reactions was the same as that observed in the aldehyde oxidation reactions.

Original languageEnglish
Pages (from-to)16977-16986
Number of pages10
JournalJournal of the American Chemical Society
Volume132
Issue number47
DOIs
StatePublished - 1 Dec 2010

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