Association of Zn- and Mg-based chain transfer agents in coordinative chain transfer polymerizations of olefins for enhanced control and activity†

Abstract

Based on DFT-level computational studies, ZnEt₂ was implemented as a chain transfer agent (CTA) to promote the coordinative chain transfer (co)polymerization of ethylene for the first time with a metallocene complex of Nd. The use of ZnEt₂ in combination with Mg(ⁿBu)_1.5(ⁿOct)_0.5 compared to the use of Mg(ⁿBu)_1.5(ⁿOct)_0.5 alone, improves several key aspects of the polymerization process. When ethylene is polymerized, an increase of catalytic activities is observed and narrower molar mass distributions are obtained due to reduced β-H transfer and faster reversible chain transfer reactions. In copolymerization of ethylene with butadiene, the presence of ZnEt₂ has no impact on the polymerization process in terms of polymerization kinetics and microstructure of the final copolymer. Nevertheless, it acts as an excellent CTA. Using ZnEt₂ in combination with MesMgBr rather than Mg(ⁿBu)_1.5(ⁿOct)_0.5 enables selective chain transfer between neodymium and zinc and promotes a nearly quantitative chain-end functionalization with acyl chloride.