Introducing Weakly Ligated Tris(trifluoromethyl)copper(III)

Abstract 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 neutral adducts (DMF)2Cu(CF3)3 and (MeCN)Cu(CF3)3. Free Cu(CF3)3 is an elusive molecule of distorted T‐shaped geometry with Lewis acid properties, which is stabilized by solvation. Substitution of solvent molecules with monoanionic ligands in mild conditions afforded the first Cu(III)(CF3)3 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 trifluoromethylation reagents via the intermediacy of (MeCN)Cu(CF3)3 was developed. (DMF)2Cu(CF3)3 demonstrated promising properties in photoinduced radical C‐H trifluoromethylation. Oxidation state theoretical studies showed the Cu(CF3)3 compounds to be borderline between classical Cu(III) and inverted ligand field Cu(I) assignment.