Introducing Weakly Ligated Tris(trifluoromethyl)copper

Tris(trifluoromethyl)copper(III) – Cu(CF3)3 – was prepared for the first time and fully characterized in the form of weakly coordinated highly reactive solvent adducts (DMF)2Cu(CF3)3 and (MeCN)Cu(CF3)3. DFT calculation studies confirmed the superacid properties of Cu(CF3)3 molecule, exhibiting higher expected Lewis acidity than SbF5, which makes it one of the strongest Lewis acids known (pF- = -13.9). Substitution of solvent molecules with monoanionic ligands in mild conditions afforded the first Cu(III) carboxylates [Cu(CF3)3(OAc)]- and [Cu(CF3)3(OBz)]- and Cu(III) nitrito complex [Cu(CF3)3(ONO)]-. An improved synthesis of valuable Grushin’s reagents via the intermediary (MeCN)Cu(CF3)3 was developed.