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

Abstract

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-κC,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.

Nickel-Catalyzed Reductive Deoxygenation of Diverse C–O Bond-Bearing Functional Groups

“…Several other promising methods using the combination of a Brønsted or Lewis acid catalyst alongside a mild hydride source have also been reported . Other modern deoxygenation strategies include merging catalysis with Wolff–Kishner reductions, cross-coupling-like approaches, and beyond . Despite this progress, there is still a need for more universal, chemoselective deoxygenation reactions that work directly on unactivated C–O bond-containing starting materials.…”

Reversible Photoisomerization in a Ru cis-Dihydride Catalyst Accessed through Atypical Metal–Ligand Cooperative H2 Activation: Photoenhanced Acceptorless Alcohol Dehydrogenation

“…Examples of these key properties include light-induced M–H homolysis, reductive elimination of H 2 from cis -dihydrides, altered chemical properties (e.g., p K a , hydricity, etc. ), , and photoisomerization . If these processes are chemically reversible, they can benefit the system by preventing the formation of off-path photogenerated thermodynamic sinks and in principle could be harnessed as a photoswitch .…”