Selectivity diversity for a single cobalt(II) precatalyst mediated butadiene polymerization

Abstract

Selectivity diversity from a single catalyst not only allows for facile switch the type of product, but also helps to understand the reaction mechanism by simply varying the reaction conditions. In this research, we disclosed the capability of diversified selectivity of a cobalt complex as precatalyst to mediated 1,3-butadiene, which could produce different structures polymers under different conditions. On direct activation by EASC or MAO, such a complex was able to reveal high cis-1,4- selectivity, giving polybutadiene (PB) products with extremely low glass transition temperature; introducing PPh3 as external donor to such a system, the selectivity could switch from cis-1,4- to highly 1,2- manner, giving atactic 1,2- PBs. Moreover, the 1,2- contents of the obtained polymers were proportionally dependent on the PPh3 equivalents, gradual increasing PPh3/Co ratio was able to access cis-1,4-ran-1,2- products with gradual increased 1,2-contents. In contrast, selecting CS2 as donor could give high syndiotactic 1,2-PB products, which demonstrated melting temperatures up to 203.9 °C. Possible mechanism for such a selectivity diversity was proposed.