As part of a collaborative, NSF-supported initiative to help develop the basic chem. needed for producing solar fuels, our group has been studying relatively inexpensive, first row transition metals that mediate electrocatalytic hydrogen evolution at unusually pos. potentials. These complexes constitute a severe structural departure from the active sites of hydrogenase enzymes, but are attractive candidates for hydrogen evolution because they access reduced states at quite pos. potentials that then trigger the two-electron redn. of proton to hydride. The systems are unusual in that they display remarkable tolerance to the typical hydrogenase poison, carbon monoxide. Our efforts to more fully map the chem. of these types of systems will be described. [on SciFinder (R)]