Comparing kinetic profiles between bifunctional and binary type of Zn(salen) based catalysts for organic carbonate formation

Abstract

Zn(salen) complexes have been employed as active catalysts for the formation of cyclic carbonates from epoxides and CO2. A series of kinetic experiments were carried out to obtain information about the mechanism for this process catalysed by this kind of complexes and in particular about the order-dependence in catalyst. A comparative analysis was done between the binary catalyst system Zn(salphen)/NBu4I and a bifunctional system Zn(salpyr)·MeI with a built-in nucleophile. The latter system demonstrates an apparent second order dependence on the bifunctional catalyst concentration and thus follows a different, bimetallic mechanism as opposed to the binary catalyst that is connected with a first order dependence on the catalyst concentration and a monometallic mechanism.