Detailed mechanistic information on methane elimination from a methyl(hydride) platinum(IV) complex. Relevance for the mechanism of methane activation

The kinetics of methane reductive elimination from both isomers of the meth yl(hydrido)platinum(IV) complex [Pt(H)(CH3)(2)(BPMA)](+) (BPMA = bis(pyridy lmethyl)amine) were studied by IH NMR spectroscopy. The application of high -pressure techniques enabled the determination of the activation volume far methane elimination (+6 cm(3)/mol for the cis isomer, ca. +8 cm(3)/mol for the trans isomer). The low activation volume together with results on the rate and stereochemistry of deuterium incorporation into one methyl group o f the cis isomer provides the basis for a suggested mechanism that involves five-coordinate platinum as a steady-state intermediate.