The mechanism of extraction of electrons from H-2 catalyzed by hydrogenases has proven challenging to elucidate. Catalytic extraction of electrons from H-2 has been achieved by use of a low-valent (NiRuI)-Ru-I complex [Ni-I(mu-SR)(2)Ru-I(eta(6)-C6Me6)] {(mu-SR)(2) = N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)- 1,3-propanediamine} as the active catalyst with evolution of H-2 under ambient conditions. The electrons extracted from H-2 have been used for a catalytic reduction of Cu2+ to Cu-0 with the NiRu complexes.