Controlling Product Selectivity by Modulating H-Bonding and the Rate of Hydrogen Elimination and Hydrogen Transfer from an Ir(III)-H Complex.

Harnessing key intermediates in metal-catalyzed reactions enables highly selective organic transformations. Herein, we report an Ir(III)-catalyzed strategy for the selective synthesis of benzimidazoles and N-methylbenzimidazoles from diverse 2-nitroanilines and 1,2-diaminobenzenes using methanol. Solvent-controlled stabilization of the imine intermediate governed product selectivity: TFE favored benzimidazole formation, whereas methanol promoted rapid hydrogenation to N-methylbenzimidazoles. Mechanistic studies, supported by control experiments and DFT calculations, revealed the crucial role of solvent-modulated hydrogen transfer from a proton-responsive Ir-H species.