Hydrogen Evolution Reactions Catalyzed by a Bis(thiosemicarbazone) Cobalt Complex: An Experimental and Theoretical Study

The synthesis and characterization of a dinuclear bis(thiosemicarbazone) cobalt complex [Co2L2(NCS)(2)] is reported. This complex exhibits significant catalytic activity for hydrogen production in DMF by using triethylammonium (Et3NHBF4) as the proton source. Cyclic voltammetry data allowed a maximum turnover frequency of 130s(-1) for 1m proton concentration to be determined. The catalytic nature of the process and the production of dihydrogen were confirmed by gas analysis during controlled potential electrolysis experiments. Quantum chemical calculations show that the complex displays a ligand-assisted metal-centered reactivity and supports a catalytic mechanism involving ligand-based reduction and protonation steps followed by metal-centered processes.