Enhanced Hydrogen Generation from Formic Acid by Half-Sandwich Iridium(III) Complexes with Metal/NH Bifunctionality: A Pronounced Switch from Transfer Hydrogenation.

Abstract

By switching the catalytic function from transfer hydrogenation based on the metal/NH bifunctionality, facile dehydrogenation of formic acid was achieved by amido- and hydrido(amine)-Ir complexes derived from N-triflyl-1,2-diphenylethylenediamine (TfDPEN) at ambient temperature even in the absence of base additives. Further acceleration was observed by the addition of water, leading to a maximum turnover frequency above 6000 h(-1). A proton-relay mechanism guided by the protic amine ligand and water is postulated for effective protonation of metal hydrides.