Manganese N-Heterocyclic Carbene Complexes: Emerging Catalysts for Homogeneous Reduction Chemistry

Catalytic reductions are used in a variety of reactions in organic synthesis and industrial production of chemicals from the corresponding unsaturated precursors. Traditionally, homogeneous and heterogeneous catalysts based on late transition metals are used in these methods. With the increasing interest in the use of cheaper and more readily available 3d metals, especially in homogeneous catalysis, molecular-defined manganese complexes in particular have attracted considerable attention in recent years. In addition to phosphine and nitrogen donor ligands, N-heterocyclic carbene ligands are increasingly being used as ligands and have demonstrated their potential in several homogeneous catalytic reactions. This review presents the impressive progress achieved in recent years in the field of manganese–NHC complexes for reduction reactions. It discusses both high- and low-valent manganese–NHC complexes reported in the literature. Overall, this review can serve as guide for further catalyst developments in this exciting field of research.