Recent advances in bidentate bis(N-heterocyclic carbene) transition metal complexes and their applications in metal-mediated reactions

The advanced development of NHC chemistry has lead to an extensive array of NHC ligand classes varying in structural and electronic properties. Although monodentate NHC ligands are by far the most thoroughly studied, multi-dentate NHC ligands including bidentate, pincer, scorpionate and macrocyclic motifs along with their corresponding transition metal complexes are widely reported in the literature. The unique structural and electronic properties along with high degree of modularity inherent to NHC ligands has made them ideal candidates for the inclusion in chelate rings affording intriguing reactivity consequences in a wide range of transition metal-mediated reactions. This short review focuses on the recent developments of bidentate bis(NHC) transition metal complexes and their applications in contemporary metal-mediated reactions such as alkane oxidation, transfer hydrogenation and photochemical transformations.