Heterolytic CH activation and catalysis by an O-donor iridium-hydroxo complex

A well-defined, O-donor ligated iridium hydroxide complex is reported that is competent for benzene CH activation and long-lived catalytic H/D exchange between benzene and water. An inverse dependence of the H/D exchange rate on added pyridine, a kinetic isotope effect (KIE) of 2.65 ± 0.56 for CH activation with 1,3,5-trideuteriobenzene, a KIE of 1.07 ± 0.24 with C ₆H ₆/C ₆D ₆, and DFT calculations are consistent with the CH activation proceeding via rate-determining benzene coordination followed by fast CH cleavage via a σ-bond-metathesis transition state.