Highly Efficient and Thermal Robust Cobalt Complexes for 1,3-Butadiene Polymerization

A family of highly bulky bis(salicylaldiminate) Co(II) complexes bearing cavity-like conformations are disclosed herein. Due to their unique bulky nature around the cobalt atoms that are reflected from space-filling models and the buried volume percentages, obviously longer bond distances of Co-N and Co-O are revealed from those complexes. Moreover, because of these well-protected active species, the cobalt complexes are able to catalyze 1,3-butadiene polymerization in high yields at extreme low catalyst concentrations, revealing a ultra high catalytic efficiency. At a ratio of 50000, all the complexes can afford polybutadiene with yields higher than 90%. Furthermore, the highly steric bulkiness of the ligand can also significantly enhance the thermostability of the active species. At temperature of 80–120 °C, the complexes are able to successfully maintain high activities, giving polymer yields up to 90%. © 2022, Chinese Chemical Society Institute of Chemistry, Chinese Academy of Sciences.