A Cobalt–Dithiolene Complex for the Photocatalytic and Electrocatalytic Reduction of Protons

The complex [Co(bdt)2]− (where bdt = 1,2-benzenedithiolate) is an active catalyst for the visible light driven reduction of protons from water when employed with Ru(bpy)32+ as the photosensitizer and ascorbic acid as the sacrificial electron donor. At pH 4.0, the system exhibits very high activity, achieving >2700 turnovers with respect to catalyst and an initial turnover rate of 880 mol H2/mol catalyst/h. The same complex is also an active electrocatalyst for proton reduction in 1:1 CH3CN/H2O in the presence of weak acids, with the onset of a catalytic wave at the reversible redox couple of −1.01 V vs Fc+/Fc. The cobalt–dithiolene complex [Co(bdt)2]− thus represents a highly active catalyst for both the electrocatalytic and photocatalytic reduction of protons in aqueous solutions.