Metal-carbon bond functionalization in the context of methane oxidation

Abstract

Metal-mediated alkane functionalization requires catalyzing C-H cleavage and carbon- heteroatom bond formation, each of which pose high, potentially rate- limiting barriers. To complement the traditional nucleophilic attack mechanism for functionalizing M-CH_3 bonds, we have used computed free energy surfaces to develop the attack of electrophiles on metalcarbon bonds. Recently we described the conversion of a vanadium- Ph bond to phenoxide via migration of the Ph group to a sep. vanadate oxo group. This formally homolytic M-C bond cleavage results in the one- electron redn. of both vanadium centers. We predict that some one-electron oxidants will allow this mechanism to be transferred to late transition metals compatible with non- radical methane oxidn. Iridium- Me bonds, however, are less polar than those of Group 10 metals and stronger than those of 1st and 2nd row metals. We find their functionalization is likely to begin with attack at the C-H bonds.