Organometallic chemistry of bis(N-heterocyclic carbene) ligands containing a heteroarene spacer

Heteroarene-linked bis(N-heterocyclic carbenes) constitute an important family of ligands in transition metal chemistry and homogeneous catalysis. These ligands are used as multidentate ligands for the construction of mononuclear and multinuclear complexes that show unique physical properties and that are efficient catalysts for many organic transformations. A number of transition metal complexes of heteroarene-linked bis(N-heterocyclic carbene) ligands have been synthesized and structurally characterized in recent decades. In this review, we summarize the recent developments in metal complexes supported by heteroarene-linked bis(N-heterocyclic carbene) ligands and their applications. The ligands and their complexes are categorized by the linkers between the two NHCs, such as pyridine, bipyridine, phenanthroline, naphthyridine, pyrazole, thiophene, and pyridazine. (C) 2017 Elsevier B.V. All rights reserved.