Bis(phenolate) N‐Heterocyclic Carbene [OCO] Pincer Ligands: A Unique Family for the Stabilization of Transition Metal Centers and Main Group Elements

The present contribution comprehensively reviews the coordination chemistry of N‐heterocyclic carbene (NHC) bis‐phenolate tridentate ligand of the type [OCO] to various metal and heteroatom centers. The structural features of the resulting robust [OCO]M chelates are discussed along with their unique and specific properties, including emerging redox and optical properties of such complexes. Thanks to their stability and electronic features, this class of robust metal chelates has already been exploited for various catalytic applications, most notably the controlled polymerization of polar cyclic monomers and olefins, N 2 reduction and photoinduced catalysis. In addition, some [OCO]M complexes have also been shown to stoichiometrically activate/functionalize small molecules such as O 2 and NH 3 . All these aspects, some of them just emerging, are discussed herein along with future research opportunities on [OCO]M chelates.