Redox-Active Ligands in Catalysis

Nature’s use of redox‐active moieties combined with 3d transition‐metal ions is a powerful strategy to promote multi‐electron catalytic reactions. The ability of these moieties to store redox equivalents aids metalloenzymes in promoting multi‐electron reactions, avoiding high‐energy intermediates. In a biomimetic spirit, chemists have recently developed approaches relying on redox‐active moieties in the vicinity of metal centers to catalyze challenging transformations. This approach enables chemists to impart noble‐metal character to less toxic, and cost effective 3d transitional metals, such as Fe or Cu, in multi‐electron catalytic reactions. Juggling with both hands: For sustainable energy, mastering multi‐electron catalytic processes is the key feature. To address this challenge, nature combines redox‐active metals with redox‐active mediators or ligands. The resulting catalytic transformations (e.g. water splitting, CO2 reduction, CH activation) proceed with low kinetic barriers. This Minireview highlights recent examples of homogeneous catalysis involving redox‐active ligands.