CO2 Hydrogenation and Formic Acid Dehydrogenation Using Ir Catalysts with Amide-Based Ligands

A series of Ir catalysts bearing amide-based ligands generated by a deprotonated amide moiety was prepared with the hypotheses that the strong electron-donating ability of the coordinated anionic nitrogen atom and the proton-responsive OH group near the metal center will improve the catalytic activity for CO2 hydrogenation and formic acid (FA) dehydrogenation. The effects of the modifications of the ligand architecture on the catalytic activity were investigated for CO2 hydrogenation at ambient conditions (25 °C with 0.1 MPa H2/CO2 (v/v = 1/1)) and under slightly harsher conditions (50 °C with 1.0 MPa H2/CO2) in basic aqueous solutions together with deuterium kinetic isotope effects (KIEs) with selected catalysts. Cp*Ir(L12)(H2O)HSO4 (L12 = 6-hydroxy-N-phenylpicolinamidate) that has an anionic coordinating N atom and an OH group in the second coordination sphere, exhibits a turnover frequency (TOF) of 198 h–1 based on the initial 1 h of reaction. This TOF which, to the best of our knowledge, is the highes...