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

• Published in: Chemistry : a European journal 2018-06, Vol.24 (35), p.8779-8786
• Main Authors: Straistari, Tatiana, Hardré, Renaud, Fize, Jennifer, Shova, Sergiu, Giorgi, Michel, Réglier, Marius, Artero, Vincent, Orio, Maylis
• Format: Article
• Language: English
• Subjects: Catalysis; Catalytic activity; Chemistry; Cobalt; Cobalt compounds; Coordination compounds; electrocatalysts; Electrolysis; Gas analysis; hydrogen evolution reaction; Hydrogen evolution reactions; Hydrogen production; Ligands; Metals; Organic chemistry; Protonation; Quantum chemistry; redox-active ligands
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201801155

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 130 s−1 for 1 m 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. Center of attraction: A dinuclear cobalt complex based on a thiosemicarbazone ligand is an efficient electrocatalyst for hydrogen evolution reactions. The catalytic mechanism involves ligand‐based reductions alternating with protonation steps consistent with an unusual ligand‐assisted metal‐centered reactivity (see scheme).