Chemical CO2 fixation by a heterogenised Zn(ii)-hydrazone complex†

Abstract

A new Zn(II) coordination compound, [Zn(HL)(OAc)₂] (1), with ONN-donor hydrazone ligand (HL = (E)-4-amino-N′-(1-(pyridin-2-yl)ethylidene)benzohydrazide) was synthesized and structurally characterized by using spectroscopic techniques and X-ray analysis. These analyses indicated that the Zn(II) ion in the resulting coordination compound is five coordinated and the compound has a free amine functionality on the phenyl ring. Thus, [Zn(HL)(OAc)₂] (1) was immobilized on the surface of propionylchloride functionalized silica gel through an amidification process via the reaction of the aniline part of compound 1 and the acyl chloride group of the support. The synthesized heterogeneous catalyst, Si-[Zn(HL)(OAc)₂], was characterized by several analytical methods and the results confirmed the successful support of 1 on the surface of the support. Si-[Zn(HL)(OAc)₂] was used in a chemical CO₂ fixation reaction and styrene epoxide was used as a model substrate to investigate the catalytic performance of the supported Zn(II) catalyst. Si-[Zn(HL)(OAc)₂] can efficiently catalyze the formation of cyclic carbonate from the reaction of epoxide and CO₂ in the presence of TBAB as a co-catalyst.