Catalysis of Proton Reduction by a [BO_4]-Bridged Dicobalt Glyoxime

We report the preparation of a dicobalt compound with two singly proton-bridged cobaloxime units linked by a central [BO_4] bridge. Reaction of a doubly proton-bridged cobaloxime complex with trimethyl borate afforded the compound in good yield. Single-crystal X-ray diffraction studies confirmed the bridging nature of the [BO_4] moiety. Using electrochemical methods, the dicobalt complex was found to be an electrocatalyst for proton reduction in acetonitrile solution. Notably, the overpotential for proton reduction (954 mV) was found to be higher than in the cases of two analogous single-site cobalt glyoximes under virtually identical conditions.