Syndiotactic-Specific Polymerization of Propene with Nickel-Based Catalysts. 3.Polymer end-groups and regiochemistry of propagation

Low molecular weight prevailingly syndiotactic polypropylene samples have been synthesized under proper conditions . 13 with homogeneous catalytic systems based on Ni II diimine derivatives and methylaluminoxane. C NMR analysis of the natural abundance end groups formed in both the initiation and termination steps suggests that the regiospecificity of propene insertion during the propagation is prevailingly 1,2. The effects of ligand variation at the Ni catalytic center on the regiospecificity of the polymerization is in agreement with 1,2 insertion as the main mode of propagation