Alternative Transformations of N-Heterocyclic Carbene Complexes of the Group 11 Metals in Transmetalation Reactions (A Review)

Abstract

The carbene transfer from N-heterocyclic carbene complexes of Group 11 metals (NHC-M C ) (especially silver and copper) to other metals is considered a convenient and universal, sometimes having no alternative, method for the synthesis of a wide range of important N-heterocyclic carbene complexes of transition metals. As the number of successful examples of transmetalation with the formation of the target product has increased, the data were accumulated on alternative or unexpected results of the interaction of NHC-M C complexes with compounds of other metals. This review considers the examples of NHC-M C reactions with compounds of other metals which proceed with a change in the metals oxidation state, conversion of (NHC)M C X into cationic homoleptic [(NHC) 2 M C ] + forms, transmetalation retaining the other metal in the coordination sphere of the product, or formation of heterometallic adducts preserving the M C -C carbene bond, rather than these occurring according to the standard reaction pathway. Unusual "reverse" carbene transfer reactions have been considered separately. The review material reveals a promising new synthetic potential of NHC-M C in the reactions with other metals and discusses the possible mechanisms and driving forces of such transformations. The most important aspects of the application of the obtained products, primarily in various catalytic processes, have been considered as well.