Cobalt complexes supported by diglyoxime ligands of the type Co(dmgBF2)2(CH3CN)2 and Co(dpgBF2)2(CH3CN2) (where dmgBF2 is difluoroboryldimethylglyoxime and dpgBF2 is difluoroboryldiphenylglyoxime), as well as cobalt complexes with 1;143;-tetraene-N4 (Tim) ligands of the type 1;Co(TimR)X23;n+ (R = Me or Ph, X = Br or CH3CN; n = 1 with X = Br and n = 3 with X = CH3CN) have been obsd. to evolve H2 electrocatalytically at potentials between -0.55 V and -0.20 V vs. SCE in CH3CN. The potentials at which these cobalt complexes catalyzed H2 evolution were close to the reported thermodn. potentials for the prodn. of H2 from protons in CH3CN, with the smallest overpotential being 40 mV for Co(dmgBF2)2(CH3CN)2. Consistent with these small overpotentials, some of the complexes were also able to oxidize H2 in the presence of a suitable conjugate base. [on SciFinder (R)]