Chapter 28 - Advances in the Design and Application of Redox-Active and Reactive Pincer Ligands for Substrate Activation and Homogeneous Catalysis

Abstract

In traditional design strategies for homogeneous catalysts, transition metals are the locus of all reactivity, and the “spectator” ligands merely enable redox-changes at and stabilize the required geometric modifications incurred on the metal ions during substrate activation and turnover. Lately, ligand design principles have been developed that install more active roles onto these organic fragments. Two main lines can be distinguished within this emerging field, namely (1) concepts that revolve around direct participation of the ligand in chemically reversible bond-breaking and -making processes during substrate activation and turnover (“reactive ligands”) and (2) strategies where the ligand displays redox-chemistry that either infers new reactivity at the metal center or at the metal-bound substrate (“redox-active ligands”). This chapter provides an overview of the main avenues pursued within both research directions, highlighting established and novel prominent developments as well as upcoming and potentially relevant unexplored opportunities for metal-ligand bifunctional and ligand-mediated catalysis. The first part deals with reactive ligands, the second part with redox-active ligands.