Electrocatalytic hydrogen evolution by cobalt complexes of macrocyclic imine ligands

A series of cobalt complexes with macrocyclic imine ligands such as difluoroboryldiglyxomime and [14]-Tetraene-N4 are synthesized for electrochem. hydrogen evolution catalysis. The complexes catalyze the redn. of proton to dihydrogen at potentials in the range between -0.55 V to -0.20 V vs. SCE in acidic acetonitrile solns. A correlation between the rates of hydrogen evolution and the Co(II/I) potentials of the catalysts is established. The catalysis is triggered by the redn. of cobalt(II) precursors to cobalt(I) species, while have been synthesized and studied independently. Attempts are made to isolate important catalytic intermediates such as cobalt(III) hydride species