Isotactic-specific polymerization of propene with an iron-based catalyst: polymer end groups and regiochemistry of propagation

Prevailingly isotactic poly(propylene) samples were prepared with a homogeneous catalytic system based on a bis(imino)pyridyl Fe(II) derivative and methylaluminoxane. The polymer microstructure is in agreement with Bernoullian statistics of dyad formation, implicating a “chain-end” mechanism of steric control. The latter is operative even at polymerization temperatures as high as +50°C. NMR analysis of polymer end groups indicates that chain growth proceeds via 2,1 monomer insertion. The last two findings are unprecedented for isotactic-specific polymerization of propene and are reasonably related to each other.