Ultrahigh activity and broad temperature resistance of amine-imine cobalt precatalysts for butadiene polymerization

A series of amine-imine cobalt complexes (Co1-Co7) has been prepared and characterized. The complexes Co3, Co4, and Co6 have a distorted tetrahedral geometry, as determined by single crystal X-ray diffraction. In the presence of ethylaluminum sesquichloride (EASC), Co3 exhibited ultra-high activity toward butadiene (Bd) polymerization (up to 7813 kg_polymer mol^-1 h^-1). The activity is higher than any yet recorded for which yield high cis-1,4 polybutadiene by the well-defined late-transition metal catalytic system. The catalyst also exhibited excellent tolerance towards the ratio of Co/Bd and broad temperature stability. At a ratio of Bd/Co3 = 50 000, the complexes Co1-3 can afford polybutadiene with yields higher than 96% within 2 hours. At -20 °C to 100 °C, the complex Co3 afforded relatively high polymer yields at low catalyst concentrations (Bd/Co3 = 25 000). In addition, all polymers showed a relatively high molecular weight (up to 1.06 × 10⁶ g mol^-1).