N-Heterocyclic Carbene Complexes in C–H Activation Reactions

In this contribution, we provide a comprehensive overview of C–H activation methods promoted by NHC–transition metal complexes, covering the literature since 2002 (the year of the first report on metal–NHC-catalyzed C–H activation) through June 2019, focusing on both NHC ligands and C–H activation methods. This review covers C–H activation reactions catalyzed by group 8 to 11 NHC–metal complexes. Through discussing the role of NHC ligands in promoting challenging C–H activation methods, the reader is provided with an overview of this important area and its crucial role in forging carbon–carbon and carbon–heteroatom bonds by directly engaging ubiquitous C–H bonds.