Copolymerization Behavior of Unbridged Indenyl Metallocenes: Substituent Effects on the Degree of Comonomer Incorporation

The copolymerization of ethylene and 1-hexene with a variety of unbridged indenylmetallocenes was investigated and compared to unbridged bis(indenyl)zirconium dichloride and bis(cyclopentadienyl)zirconium dichloride as well as ansa -bridged rac -ethylenebis(indenyl)zirconium dichloride (EBIZrCl 2 ). The unbridged bis(2-phenylindenyl)zirconium dichloride showed higher selectivity for the incorporation of 1-hexene than the bridged rac -ethylenebis(indenyl)zirconium dichloride and much higher 1-hexene incoporation than the unbridged bis(indenyl)zirconium dichloride and bis(cyclopentadienyl)zirconium dichloride. Both ligands appear to be important since the 1-hexene incorporation of the mixed ligand compound (cyclopentadienyl)(2-phenylindenyl)zirconium dichloride is much lower than that of bis(2-phenylindenyl)zirconium dichloride. For unbridged bis(indenyl)metallocenes, the nature of the substituent in the 2-position plays an important role in comonomer selectivity: bis(2-methylindenyl)zirconium dichloride and bis(2-phenylethynylindenyl)zirconium dichloride exhibit much higher 1-hexene incorporation than bis(indenyl)zirconium dichloride but lower than bis(2-phenylindenyl)zirconium dichloride.