Chemical fixation of carbon dioxide to cyclic carbonates catalyzed by zinc(II) complex bearing 1,2-disubstituted benzimidazole ligand

Abstract A new zinc(II) complex of formula [ZnCl2(L1)2] (1) [L1 = 2-(2-thienyl)-1-(2-thienylmethyl)-1H- benzimidazole] was synthesized and fully characterized by nuclear magnetic resonance and infrared spectroscopy, elemental analysis, electrospray ionization high-resolution mass spectrometry, and thermogravimetric analysis. The molecular structure was confirmed by single-crystal X-ray diffraction. Complex 1 consists of mononuclear tetrahedral zinc(II) units with a locked geometry resulting from weak intramolecular S…π and π–π interligand interactions. The benzimidazole ligand and its zinc(II) complex were readily obtained through a simple synthetic route. The catalytic activity of 1 was investigated in the coupling of carbon dioxide with epoxides to produce cyclic carbonates, and a series of parameters were evaluated. The complex efficiently catalyzed the transformation of various epoxides under solvent-free conditions, with good conversions, turnover numbers, and turnover frequencies.