Convenient preparation of copper(I) N-heterocyclic carbene complexes under mild conditions

This work describes a new method for the preparation of copper N-heterocyclic carbene (NHC) complexes, which is conducted under air with mild conditions, using bench-stable precursors and a weak base (NEt 3 ). Under optimized conditions, the complexes were prepared in short reaction times of 1 h, giving moderate to good yields after purification by column chromatography. Commonly utilized NHC–HCl salts were found to be applicable reacting with CuCl or CuI giving [(NHC)CuX]-type complexes (X = Cl, I). This study adds to the growing literature in the preparation of catalytically relevant transition metal NHC complexes under mild and operationally simple conditions.