Substrate Recognition and Regioselective Catalysis with Complexes Bearing NR,NH-NHC Ligands

Complexes bearing protic N-heterocyclic carbene (NHC) ligands (NR,NH-NHCs) have been shown to use the NH group of the NHC ligand for the formation of hydrogen bonds to selected substrates. This type of hydrogen bond can be used for substrate recognition, selection, and orientation. In contrast to related systems, the hydrogen bond donor and thus the molecular recognition unit is located in proximity to the metal center. This concept article discusses major strategies for the preparation of complexes bearing protic NHC ligands and their potential applications.