Intramolecular Hydrogen Transfer Reactions Catalyzed by Pentamethylcyclopentadienyl Rhodium and Cobalt Olefin Complexes: Mechanistic Studies.

The mechanism of intramolecular transfer dehydrogenation catalyzed by [Cp*M(VTMS)2] (1, M=Rh, 2, M=Co, Cp* = C5Me5, VTMS = vinyltrimethylsilane) complexes has been studied using vinyl silane protected alcohols as substrates. Deuterium-labeled substrates have been synthesized and the regioselectivity of H/D transfers investigated using 1H and 2H NMR spectroscopy. The labeling studies establish a regioselective pathway consisting of alkene directed α C-H activation, 2,1 alkene insertion, and finally β-hydride elimination to give silyl enol ether products.