Highly active mesoionic chalcogenone zinc(II) derivatives for C-S cross-coupling reactions

Article abstract of DOI:10.1039/c9nj04440j

The first mesoionic heavier chalcogenones, L¹-L³ [L¹ = 1-(2-mesitylene)-3-methyl-4-phenyltriazolin-5-selone; L² = 1-(2-mesitylene)-3-methyl-4-phenyltriazolin-5-thione; L³ = 1-(benzyl)-2-3(methyl)-4-phenyltriazolin-5-selone], were isolated and characterised. Density functional theory was used to obtain insights into the σ donor and π accepting nature of mesoionic chalcogenones. Using these new ligands, a series of the first zinc(ii) mesoionic chalcogenone complexes were isolated. Three mono nuclear zinc(ii) chalcogenone complexes, [(L¹)Zn(Cl)₂(HOMe)] (1), [(L²)Zn(Cl)₂(HOMe)] (3) and [(L²)Zn(Br)₂(HOMe)] (4), and two dinuclear zinc complexes, [(L¹)Zn(Br)(μ²-Br)]₂ (2) and [(L³)Zn(Br)(μ²-Br)]₂ (5), containing mesoionic thione and selone ligands were synthesized and characterised. These new complexes 1-5 represent the first structurally characterized mesoionic chalcogenone supported metal derivatives. Furthermore, all zinc complexes were characterized by thermogravimetric analysis and UV-vis spectroscopy. The solid-state structures of all zinc complexes were determined by single-crystal X-ray diffraction. The catalytic activities of the zinc(ii) complexes in thioetherification reactions were investigated without scrubbing of oxygen. The scope of the catalytic reactions was explored with a wide range of thiophenols and aryl halides. The diaryl thioethers were obtained in very good yield under mild conditions. The present protocol furnishes a synthetic route for the C-S cross-coupling of thiophenols and aryl halides without scrubbing oxygen and moisture.