Deactivation of Cationic CuI and AuI Catalysts for A³ Coupling by CH₂Cl₂: Mechanistic Implications of the Formation of Neutral CuI and AuI Chlorides

Care should be exercised when using CH2 Cl2 as a solvent for reactions in which amines are a reagent, since undesirable deactivation of cationic copper(I) and gold(I) catalysts to form the corresponding inactive neutral chloride complexes [LMCl] (M=Cu or Au) can occur as a result of the generation of hydrogen chloride in the medium. Cu(I) and Au(I) deactivation has been proved for the Mannich three-component coupling reaction. A series of Cu(I) and Au(I) complexes with potential mechanistic implications were isolated and characterized by X-ray crystallography.