Ligand-Level Chemical Activation: Coordination with Benefits

Abstract

Influencing electron distribution within a coordination complex bearing redox-active ligands offers the possibility to foster new reactivities. This redistribution can involve electrons but also protons or more elaborate chemical groups. Often perceived as a liability, chemical non-innocence can actually be considered a synthetic tool in which the synergy between metal and ligand leads to chemical reactivity at the ligand that is part of a streamlined process, rather than an unwanted side reaction. This concept article aims at providing examples of how redistributing electron density within a metal complex bearing redox-active ligands can foster interesting functionalization chemistry. This seemingly fundamental question has very practical applications in the fields of hydrogenation and energy-related catalytic reactions such as small-molecule activation, solar fuels, or to make new (photo)catalysts and noncanonical redox cofactors.