Homoleptic and heteroleptic Zn(ii) selone catalysts for thioetherification of aryl halides without scrubbing oxygen

Abstract

Five new mononuclear tetra-coordinated zinc(II) selones, [Zn(L¹)₂Cl₂] (1), [Zn(L¹)₂Br₂] (2), [{Zn(L²)₄}{BF₄}₂] (3), [{Zn(L²)₄}{ClO₄}₂] (4), and [Zn(L²)₂Br₂] (5), have been isolated from a one-pot reaction between the corresponding zinc(II) salt and selone ligand, 1-methyl 3-naphthylmethylimidazoline-2-selone (L¹) or 1-isopropyl 3-methylimidazoline-2-selone (L²). All these complexes were characterized by CHN analysis, FT-IR, NMR studies, and single-crystal X-ray crystallography techniques. The Zn(II) center in 1–5 exhibits a distorted tetrahedral geometry. Besides, 1–5 were employed as catalysts in the thioetherification of aryl halides. The first zinc(II) catalyst-mediated thioetherification of aryl halides without scrubbing oxygen was demonstrated. Catalysts 1–5 are highly active towards the cross-coupling reaction between aryl halides and thiophenols. The catalytic ability of 1–5 was explored in THF, toluene, and CH₃CN solvents with different bases such as K₂CO₃, Cs₂CO₃, and NaO^tBu. Interestingly, the zinc(II) center attached to two selone ligands is much more catalytically active than that attached to four selone ligands.