Recent progress in synthesis of metal complexes of N-heterocyclic carbenes

• 1、Department of Chemistry, Zhejiang University

Abstract：N-Heterocyclic carbene ligands (NHCs) are playing an increasingly important role in the areas of pharmaceutical, materials science, and organic synthetic chemistry. While numerous powerful catalytic systems incorporating NHC ligands have been described, methods of synthesizing them have advanced more slowly. This review describes the recent progress of the methods used in the preparation of N-heterocyclic carbene complexes. According to the nature of the NHC precursor and to the activation method employed, the methods for preparing NHC–metal complexes can be classified as: (1) Insertion of a metal into the C = C bond of bis(imidazolidin-2-ylidene) olefins. (2) Use of preformed, isolated free carbenes. (3) Deprotonation of an azolium salt with a base. (4) Use of carbene adducts or “protected” forms of free NHC carbenes. (5) Transmetallation from a preformed NHC complex. (6) Oxidative addition via activation of the C2– X (X = Me, halogen, H) of an imidazolium cation. (7) Direct synthesis of Iron, Cobalt, Nickel, and Copper complexes of N-heterocyclic carbenes by using commercially available metal powders.

Keywords： Imidazolium N-heterocyclic carbene metal complex Synthesis