Bipyridyl Functionalized NHC‐Sulfenyl, Selenenyl Cations; Potential Species for Alkylation Reactions and Ligands in Copper(I) Catalysis

Reactions of bipyridyl-functionalized imidazole-thiones and selones with MeX (X=I, OTf) afforded sulfenyl and selenenyl cations [(NNC)EMe]X (2/3, E=S, Se). Further reactions of these main-group cations with [Cu(CH₃CN)₄]BF₄, Cu(OTf) furnished dicationic [{Cu(μ-I)(NNC)EMe}₂][Y]₂ (5/6, Y=BF₄, OTf) and tricationic copper(I) complexes [Cu{(NNC)EMe}₂](OTf)₂BF₄ (7 a/7 b) when employed [(NNC)EMe]I and [(NNC)EMe]OTf respectively. All these cationic complexes were characterized by various spectroscopic techniques, including X-ray diffraction analysis. The solid-state structures revealed novel bonding modes of the cations. The cationic nature of new complexes was analyzed by the ⁷⁷Se NMR spectroscopy, which indicated different electronic environments around the selenium centers. The cations [(NNC)EMe]X (X= I, OTf), and (NNC)SMe bearing copper complex [{Cu(μ-I)(NNC)EMe}₂][Y]₂ proved as potential candidates for alkylation of various Lewis bases and as molecular catalyst in aldehyde-alkyne-amine coupling reactions, respectively. The latter catalytic reactions yielded a range of three-component products in good to excellent yields with low catalyst loading under solvent-free conditions, which demonstrate the potential utility of group-16 cations as ancillary ligands in homogeneous catalysis.