C 1 ‐Symmetric Heterocyclic Zirconocenes as Catalysts for Propylene Polymerization, 2

Sixteen C 1 ‐symmetric zirconocene and one hafnocene complexes bearing the 2,5‐R 2 ‐7H‐cyclopenta[1,2‐ b :4,3‐ b ′]dithiophene ligand (R = H, Me, Et, Ph) linked to a substituted indenyl ligand have been synthesized and tested in propylene polymerization. Most of the C 1 ‐symmetric zirconocenes of this type are highly active in propylene polymerization at low MAO/Zr ratios and produce poly(propylene)s (PP) in a broad range of isotacticity and melting points. The molecular weight and crystallinity of the PPs are strongly dependent upon the type of substituents on the indenyl moiety: PPs with T m between 75 and 156 °C and viscosity average molecular weights between 100 000 and 400 000 have been obtained at 50–70 °C in liquid propylene. General formula of the indenyl‐based zirconocenes. magnified image General formula of the indenyl‐based zirconocenes.