An improved bidentate complex of iridium as a catalyst for hydrogen isotope exchange

Iridium(I) complexes 1, containing bidentate phosphines, and 3, with arsine ligands, are generated in situ. These species mediate hydrogen isotope exchange in a variety of aromatic substrates including benzyl ketones. Although the catalytic activities of complexes 1 and 3 are generally unexceptional, a logical step leads to the use of [ethylene‐1,2‐bis(diphenylarsine)](cyclooctadiene)iridium(I) tetrafluoroborate (5), which is an efficient catalyst for both aryl and benzyl ketones, and mediates exchange to a substantial extent in other substrates also.