O2 Activation by Non-adiabatic Oxidative Addition to aSingle Metal Center

摘要

A chromium(I) dinitrogen complex reacts rapidly with O2 to form the mononuclear dioxo complex Tp^tBu,MeCr^V(O)2, whereas the analogous reaction with sulfur stops at the persulfido complex Tp^tBu,MeCr^III(S2). The transformation of the putative peroxo intermediate Tp^tBu,MeCr^III(O2)(S = ³/2) into Tp^tBu,MeCr^V(O)2 (S = ½) is spin forbidden. The minimum energy crossing point on the two potential energy surfaces has been identified. While the dinuclear complex (Tp^tBu,MeCr)2(μ-O)2 exists, mechanistic experiments suggest that the O2 activation occurs on a single metal center, by an oxidative addition on the quartet surface followed by crossover to the doublet surface.