Syndiotactic-Specific Polymerization of Propene with Nickel-Based Catalysts. 2. Regiochemistry and Stereochemistry of the Initiation Steps

A homogeneous catalytic system based on a suitable Ni(II) diimine derivative and methylaluminoxane affords predominantly syndiotactic polypropylene at subambient temperatures. The polymer microstructure is that expected for a “chain-end” mechanism of steric control. NMR analysis of polymer samples carrying selectively 13C-enriched end groups indicates a largely prevailing 1,2 regiochemistry for the insertion of propene into Ni-13CH3 bonds in the initiation step and a syndiotactic steric control already effective in the second propagation step.