The photochemistry of metal hydride complexes is dominated by H evolution, limiting access to reductive transformations based on photochemical hydride transfer. In this article, the innate H evolution photochemistry of the iridium hydride complexes [Cp*Ir(bpy-OMe)H] (, bpy-OMe = 4,4'-dimethoxy-2,2'-bipyridine) and [Cp*Ir(bpy)H] (, bpy = 2,2'-bipyridine) is diverted towards photochemical hydrodechlorination. Net hydride transfer from and to dichloromethane produces chloromethane with high selectivity and exceptional photochemical quantum yield ( ≤ 1.3). Thermodynamic and kinetic mechanistic studies are consistent with a non-radical-chain reaction sequence initiated by "self-quenching" electron transfer between excited state and ground state hydride complexes, followed by proton-coupled electron transfer (PCET) hydrodechlorination that outcompetes H-H coupling. This unique photochemical mechanism provides a new hope for the development of light-driven hydride transfer reactions.
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| http://dx.doi.org/10.1039/d0sc00422g | DOI Listing |
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