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)-fl uorenyl)-2-(4,5-cyclohexa-2-methyl-1-eta(5)-indenyl)ethane]zirconium dichlo ride (14b), and rac-[1-(9-eta(5)-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-et a(5)-indenyl)ethane]zirconium dichloride (15) were prepared in up to 93% yi eld. These compounds, activated with methyl aluminoxane, exhibit high activ e propene polymerization rates which remain constant over hours, even at el evated polymerization temperatures of 50 and 70 degrees C. The two differen t coordination sites of these "dual-side" catalysts lead to isotactic polyp ropenes with variable amounts of stereoerrors, depending on the monomer con centration, The 2-methyl substituent of the indenyl ligands results, at the same time, in significantly increased molecular weights of the polymer pro ducts (up to 2.3 x 10(5) g mol(-1)), the bulk properties of which can be ad justed from flexible, semicrystalline thermoplastic to excellent thermoplas tic elastic.