Dinuclear N-heterocyclic carbene copper(I) complexes

Copper(I) species exhibit various coordination modes as a function of surrounding ligands. Complexes bearing N-heterocyclic carbenes as ligands are usually monomeric species with the copper adopting a linear geometry. Contrarily to the parent phosphine complexes, in which the presence of species of higher nuclearity is well established, fewer examples of such copper(I)-NHC species are reported and, interestingly, their number is growing. Moreover, these are no longer a mere curiosity from a coordination perspective since they have been shown successful in catalysis. The aim of this review is to present a summary of the synthesis and structural properties of dinuclear copper(I)-NHC complexes. It is our hope that by centralizing all information available on such species, future efforts aimed at exploiting their full potential can be facilitated.