Effect of Solvent and Ancillary Ligands on the Catalytic H/D Exchange Reactivity of Cp*Ir^III(L) Complexes

The reactivity of a series of Cp*Ir^III(L) complexes that contain a diverse set of ancillary ligands, L, (L = PMe₃, N-heterocyclic carbene, NHC = 1,3-dimethylimidazol-2-ylidene, aqua, 4-<i>t</i>-butylpyridine, and 4-(2,4,6-tris-(4-<i>t</i>-butylphenyl)­pyridinium)­pyridine tetrafluoroborate) has been examined in catalytic H/D exchange reactions between C₆H₆ and a series of deuterated solvents (methanol-<i>d</i>₄, acetic acid-<i>d</i>₄, and trifluoroacetic acid-<i>d</i>₁). These studies demonstrate that (1) the mechanism of catalytic H/D exchange is significantly influenced by the nature of the solvent; (2) electron-donating ligands (PMe₃, NHC) promote the formation of Ir hydrides in methanol-<i>d</i>₄, and these are critical intermediates in catalytic H/D exchange processes; and (3) weak/poorly donating ligands (4-<i>t</i>-butylpyridine, 4-(2,4,6-tris-(4-<i>t</i>-butylphenyl)­pyridinium)­pyridine tetrafluoroborate and aqua) can support efficient H/D exchange catalysis in acetic acid-<i>d</i><sub>4