The role of pendant bases in molecular catalysts for H2 oxidation and production

The paper presents a review of recent studies of complexes of Ni(II) and Fe(II) coordinated by diphosphine ligands with amine bases incorporated into the ligand chelate rings. The role of the bases in the second coordination sphere in mediating rapid intramolecular M–H/N–H exchange as well as intermolecular exchange with protons and in promoting the coupling of proton- and electron-transfer processes has been studied. Factors that favor efficient proton relay properties for the pendant amines have been established and the information has been used to develop efficient electrocatalysts for both hydrogen oxidation and production.