Question

Show the mechanism for butadiene polymerizing into polybutadiene.

Answer 1

The polymerization occurred via two steps after the catalyst activated by cocatalyst. In the ?rst step, the coordination of butadiene monomer to the active center occurred, followed bymigratory insertion of the coordinated monomer into the cobalt-carbon bond. In migratory insertion step (second step), a vacant coordination site was regenerated, which enabled further chain propagation. Compared with traditional cobalt catalyst, the active center of the cationic cobalt catalyst had a very strong negative electron af?nity. Then, the coordination and insertion rate of butadiene monomer increased.