Oxygen activation at a dicobalt centre of a dipyridylethane naphthyridine complex

摘要

The mechanism of oxygen activation at a dicobalt bis-μ-hydroxo core is probed by the implementation of synthetic methods to isolate reaction intermediates. Reduction of a dicobalt( III , III ) core ligated by the polypyridyl ligand dipyridylethane naphthyridine (DPEN) by two electrons and subsequent protonation result in the release of one water moiety to furnish a dicobalt( II , II ) center with an open binding site. This reduced core may be independently isolated by chemical reduction. Variable-temperature ~(1) H NMR and SQUID magnetometry reveal the reduced dicobalt( II , II ) intermediate to consist of two low spin Co( II ) centers coupled antiferromagnetically. Binding of O _(2) to the open coordination site of the dicobalt( II , II ) core results in the production of an oxygen adduct, which is proposed to be a dicobalt( III , III ) peroxo. Electrochemical studies show that the addition of two electrons results in cleavage of the O–O bond.