Light-Promoted Transfer of an Iridium Hydride in Alkyl Ether Cleavage

A catalytic, light-promoted hydrosilylative cleavage reaction of alkyl ethers is reported. Initial studies are consistent with a mechanism involving heterolytic silane activation followed by delivery of a photohydride equivalent to a silyloxonium ion generated in situ. The catalyst resting state is a mixture of Cp*Ir(ppy)H (ppy = 2-phenylpyridine-kappa C,N) and a related hydride-bridged dimer. Trends in selectivity in substrate reduction are consistent with nonradical mechanisms for C-O bond scission. Irradiation of Cp*Ir(ppy)H with blue light is found to increase the rate of hydride delivery to an oxonium ion in a stoichiometric test. A comparable rate enhancement is found in carbonyl hydrosilylation catalysis, which operates through a related mechanism also involving Cp*Ir(ppy)H as the resting state.

Automated summary

This study reports a catalytic, light-promoted hydrosilylative cleavage reaction of alkyl ethers, involving heterolytic silane activation and delivery of a photohydride equivalent. The catalyst resting state is a mixture of Cp*Ir(ppy)H and a related hydride-bridged dimer, with trends in selectivity suggesting nonradical mechanisms for C-O bond scission. Irradiation of Cp*Ir(ppy)H with blue light increases the rate of hydride delivery in a stoichiometric test, indicating a comparable rate enhancement in carbonyl hydrosilylation catalysis operating through a related mechanism with Cp*Ir(ppy)H as the resting state.