Syntheses of Bis(N-heterocyclic carbene)s and their application in main-group chemistry

Since the first isolation of an N-heterocyclic carbene (NHC) in the early 1990s, these species have been identified as valuable tools for the stabilization of main-group elements in unusual oxidation states and allowed for the isolation of novel types of compounds. While bis(NHC)s, i.e., compounds in which two NHC units are framed within one molecule by using suitable linker groups, found numerous application in rare-earth and transition-metal chemistry, this does not hold true for main-group elements. Although examples are found throughout the s- and p-block, their potential still needs to be realized. This review summarizes the syntheses of the related bis(NHC)s and gives an overview of mono-, di- and polynuclear complexes incorporating main-group elements and bis(NHC)s. © 2020 Elsevier B.V.