A Simple Catalyst for the Synthesis of Cyclic Carbonates Based on Zinc(ii) Iodide

A new zinc(II) complex, LZnI, was obtained by the interaction of tridentate ligand 2,6-bis(5-(tert-butyl)-1H-pyrazol-3-yl)pyridine (L) with zinc(II) iodide. The compound was isolated in individual form and characterized using NMR spectroscopy and single-crystal X-ray diffraction (CIF file CCDC No. 2447394). The resulting complex exhibits catalytic activity in the reaction of CO with substituted epoxides to form cyclic carbonates. This behavior is attributed to the simultaneous presence of a Lewis acidic metal center capable of coordinating the epoxide, a Lewis basic nitrogen site facilitating CO binding, and a nucleophilic iodide anion that activates epoxide ring opening. The development of this approach to catalyst design may facilitate the creation of efficient systems for reactions of carbon dioxide with three-membered heterocycles.