Control of stereoerror formation with high-activity "dual-side" zirconocene catalysts:: A novel strategy to design the properties of thermoplastic elastic polypropenes

The new C-1-symmetric complexes rac-[1-(9-eta(5)-fluorenyl)-2-(3-methylbenz[e]-1-eta(5)-indenyl)ethane]zirconium dichloride (14a), rac-[1-(9-eta(5)-fluorenyl)-2-(4,5-cyclohexa-2-methyl-1-eta(5)-indenyl)ethane]zirconium dichloride (14b), and rac-[1-(9-eta(5)-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-eta(5)-indenyl)ethane]zirconium dichloride (15) were prepared in up to 93% yield. These compounds, activated with methyl aluminoxane, exhibit high active propene polymerization rates which remain constant over hours, even at elevated polymerization temperatures of 50 and 70 degrees C. The two different coordination sites of these "dual-side" catalysts lead to isotactic polypropenes with variable amounts of stereoerrors, depending on the monomer concentration, The 2-methyl substituent of the indenyl ligands results, at the same time, in significantly increased molecular weights of the polymer products (up to 2.3 x 10(5) g mol(-1)), the bulk properties of which can be adjusted from flexible, semicrystalline thermoplastic to excellent thermoplastic elastic.