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 C6H6/C6D6, 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.