Metal–Ligand Cooperation in Cp*Ir-Pyridylpyrrole Complexes: Rational Design and Catalytic Activity in Formic Acid Dehydrogenation and CO2Hydrogenation under Ambient Conditions

Interconversion between CO2+ H2and FA/formate is the most promising strategy for the fixation of carbon dioxide and reversible hydrogen storage; however, FA dehydrogenation and CO2hydrogenation are usually studied separately using different catalysts for each reaction. This report describes of the catalysis of [Cp*Ir(N∧N)(X)]n+(Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; X = Cl, n= 0; X = H2O, n= 1) bearing a proton-responsive N∧N pyridylpyrrole ligand for both reactions. Complex 2-H2Ocatalyzes FA dehydrogenation at 90 °C with a TOFmaxof 45 900 h–1. Its catalysis is more active in aqueous solution than in neat solution under base-free conditions. These complexes also catalyze CO2hydrogenation in the presence of base to formate under atmospheric pressure (CO2/H2= 0.05 MPa/0.05 MPa) at 25 °C with a TOF value of 4.5 h–1in aqueous solution and with a TOF value of 29 h–1in a methanol/H2O mixture solvent. The possible mechanism is proposed by intermediate characterization and KIE experiments. The extraordinary activity of these complexes are mainly attributed to the metal–ligand cooperative effect of the the pyrrole group to accept a proton in the dehydrogenation of formic acid and assist cooperative heterolytic H–H bond cleavage in CO2hydrogenation.