Issue 25, 2020

Mechanistic basis for tuning iridium hydride photochemistry from H2 evolution to hydride transfer hydrodechlorination

Abstract

The photochemistry of metal hydride complexes is dominated by H2 evolution, limiting access to reductive transformations based on photochemical hydride transfer. In this article, the innate H2 evolution photochemistry of the iridium hydride complexes [Cp*Ir(bpy-OMe)H]+ (1, bpy-OMe = 4,4ʹ-dimethoxy-2,2′-bipyridine) and [Cp*Ir(bpy)H]+ (2, bpy = 2,2ʹ-bipyridine) is diverted towards photochemical hydrodechlorination. Net hydride transfer from 1 and 2 to dichloromethane produces chloromethane with high selectivity and exceptional photochemical quantum yield (Φ ≤ 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.

Graphical abstract: Mechanistic basis for tuning iridium hydride photochemistry from H2 evolution to hydride transfer hydrodechlorination

Supplementary files

Article information

Article type
Edge Article
Submitted
22 Jan 2020
Accepted
05 Mar 2020
First published
06 Mar 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 6442-6449

Mechanistic basis for tuning iridium hydride photochemistry from H2 evolution to hydride transfer hydrodechlorination

S. M. Barrett, B. M. Stratakes, M. B. Chambers, D. A. Kurtz, C. L. Pitman, J. L. Dempsey and A. J. M. Miller, Chem. Sci., 2020, 11, 6442 DOI: 10.1039/D0SC00422G

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