Activation of molecular oxygen. Kinetic studies of the oxidation of hindered phenols with cobalt-dioxygen complexes

Mechanistic studies of the oxidation of various substituted phenols by Co(II) bis(salicylidene-gamma-iminopropyl)methylamine, CoSMDPT are reported. The reaction is first order in (O2), (substrate) and (Co). A series of experiments are reported to provide strong support for a mechanistic scheme that involves reaction of coordinated dioxygen. Coordination of O2 to this cobalt(II) complex enhances the ability of the dioxygen to abstract hydrogen atoms and to react with phenoxy radicals. The mechanism provides a rationale for the influence of several variables on the reaction and suggests steps that were taken to retard catalyst deactivation. (Author)