Simplified Preparation of Copper(I) NHCs Using Aqueous Ammonia

The use of aqueous ammonia as a coordinating and basic reagent for the metalation of imidazol(in)ium salts derived from (S)IPr and (S)IMes with simple inorganic copper precursors is reported. The synthesis of copper carbene complexes was performed using aqueous/alcoholic media in mild conditions (room temperature to 60 °C) with short reaction times. Heteroleptic bromide and iodide complexes could be prepared efficiently for (S)IPr, while chloride complexes were easily accessible for SIMes and (S)IPr. Ammonia also allowed the efficient synthesis of homoleptic [Cu(NHC) 2 ](Y) (NHC = (S)IMes; Y = PF 6, BF 4 ) species by a variant procedure in ethanol.