The effect of oxidatively stable L- and X-type additives on the activity of Cp*Ir catalyst precursors in the C–H activation of arenes has been studied. Turnover numbers for C–H activation of up to 65 can thus be achieved, as determined by H/D exchange in MeOH-D4. In particular, carbonate additives are found to enhance the C–H activation reactivity of Cp*Ir(H2O)3(OTf)2 (1) more significantly than L-type ligands investigated in this study. Based on these studies, Cp*Ir/carbonate systems are developed that catalyze the aerobic Csp3–H oxygenation of alkyl arenes, employing air as oxidant.
