Effect of Carboxylate Ligands on Alkane Dehydrogenation with (^dmPhebox)Ir Complexes

A series of carboxylate-ligated iridium complexes (^dmPhebox)­Ir­(O₂CR)₂(H₂O) (R = −CH₃, −CH₂CH₃, −CMe₃, −CH₂C₆H₅, and −CHCMe₂) were designed and synthesized to understand the carboxylate ligand effects on the reactivity of the complex for alkane dehydrogenation. Kinetic studies showed that the different R groups of the carboxylate iridium complexes can affect the reactivity with octane in the β-H elimination step. The rate constants for octene formation with different carboxylate ligands follow the order R = −CHCMe₂ > −CMe₃ > −CH₂CH₃ > −CH₃ > −CH₂C₆H₅. In contrast, there is no significant effect of carboxylate ligand on the rate of the C–H activation step at 160 °C. These experimental results support the findings in the previously reported density functional theory study of the (^dmPhebox)Ir complex in alkane C–H activation.