Picolinamide‐Based Iridium Catalysts for Aqueous Formic Acid Dehydrogenation: Increase in Electron Density of Amide N through Substituents

Abstract Formic acid (FA) is considered to be a potential hydrogen storage material. Homogeneous catalysts are desired, which decompose aqueous FA into H 2 and CO 2 without addition of organic additives as they can contaminate the generated gas mixture. We report a new series of Cp * Ir (Cp * =pentamethylcyclopentadienyl) catalysts featuring picolinamide‐based ligands for efficient H 2 generation from FA solution. Among them in‐situ generated catalyst from [Cp * Ir(H 2 O) 3 ]SO 4 and picolinohydroxamic acid ( L3 ) achieved a high turnover frequency (TOF) of 90625 h −1 at 80 °C in 0.9 M FA solution and a turnover number (TON) of 120520 at 80 °C in a recycle experiment. The substituent effect of amide N atom was discussed and a plausible mechanism was proposed based on the experimental results.