Active trifluoromethylating agents from well-defined copper(I)-CF3 complexes

The first examples of isolable and structurally characterized Cu(I)-CF3 complexes are reported. N-Heterocyclic carbene (NHC)-supported copper tert-butoxide complexes reacted with Me3Si-CF3 to afford new (NHC)Cu-CF3 complexes whose structures were dependent on whether or not the C-4-C-5 positions of the five-membered NHC rings were saturated. In situ generated (Sl/Pr)Cu-CF3 cleanly transferred its trifluoromethyl group to a number of organic halides under mild conditions.