Abstract
Nickel perfluoroethyl and perfluoropropyl complexes supported by naphthyridine-type ligands show drastically different aerobic reactivity from their trifluoromethyl analogs resulting in facile oxygen transfer to perfluoroalkyl groups or oxygenation of external organic substrates (phosphines, sulfides, alkenes and alcohols) using O(2) or air as a terminal oxidant. Such mild aerobic oxygenation occurs through the formation of spectroscopically detected transient high-valent Ni(III) and structurally characterized mixed-valent Ni(II)-Ni(IV) intermediates and radical intermediates, resembling O(2) activation reported for some Pd dialkyl complexes. This reactivity is in contrast with the aerobic oxidation of naphthyridine-based Ni(CF(3))(2) complexes resulting in the formation of a stable Ni(III) product, which is attributed to the effect of greater steric congestion imposed by longer perfluoroalkyl chains.