Thermally robust α-diimine nickel and cobalt complexes for Cis-1,4 selective 1,3-butadiene polymerizations

Abstract

Boosting the thermal stability of α-diimine late transition metal precatalysts is a great challenge in the field of olefin/diene polymerization. In this research, a family of α-diimine nickel and cobalt complexes were disclosed. Due to the large steric hindrance of the dibenzhydryl moiety as well as the intra-ligand π-π stacking interactions in the complexes, they revealed high thermal stabilities for 1,3-butadiene polymerization at high temperatures. For some of the complexes, increasing temperature up to 90 °C showed no obvious deactivation of the precatalysts, affording corresponding polybutadiene products in high yields. Nevertheless, increasing temperature performed negative influence on the molecular weights and cis-1,4- contents of the resultant polymers, and gradual decreased molecular weight and cis-1,4- contents in both Ni(II) and Co(II) mediated systems were revealed.