Click-Derived Triazoles and Triazolylidenes of Manganese for Electrocatalytic Reduction of CO2

Abstract

A series of new <i>fac</i>-[Mn(L)(CO)₃Br] complexes where L is a bidentate chelating ligand containing mixed mesoionic triazolylidene-pyridine (MIC^py, <b>1</b>), triazolylidene-triazole (MIC^trz, <b>2</b>), and triazole-pyridine (trz^py, <b>3</b>) ligands have been prepared and fully characterized, including the single crystal X-ray diffraction studies of <b>1</b> and <b>2</b>. The abilities of <b>1</b>-<b>3</b> and complex <i>fac</i>-[Mn(MIC^MIC)(CO)₃Br] (<b>4</b>) to catalyze the electroreduction of CO₂ has been assessed for the first time. It was found that all complexes displayed a current increase under CO₂ atmosphere, being <b>3</b> and <b>4</b> the most active complexes. Complex <b>3</b>, bearing a N^N-based ligand exhibited a good efficiency and an excellent selectivity for reducing CO₂ to CO in the presence of 1.0 M of water, at low overpotential. Interestingly, complex <b>4</b> containing the strongly electron donating di-imidazolylidene ligand exhibited comparable activity to <b>3</b>, when the experiments were performed in neat acetonitrile at slightly higher overpotential (-1.86 vs. -2.14 V).