Investigation of Bridge and 2-Phenyl Substituent Effects on Ethylene/α-Olefin Copolymerization Behavior with 1,2‘-Bridged Bis(indenyl)zirconium Dichlorides

Ethylene/propylene and ethylene/1-hexene copolymerizations were studied with a series of ansa-metallocenes characterized by a gauche orientation of the indenyl ligands: [1-(1-indenyl)-2-(2-indenyl)ethane]zirconium dichloride, Et(2-Ind)(1-Ind)ZrCl2 (1)/MMAO, [2-(2-indenyl)-1-(2-phenyl-1-indenyl)ethane]zirconium dichloride, Et(2-Ind)(2-Ph-1-Ind)ZrCl2 (2)/MMAO, and [(2-indenyl)(2-phenyl-1-indenyl)dimethylsilyl]zirconium dichloride, Me2Si(2-Ind)(2-Ph-1-Ind)ZrCl2 (3)/MMAO to determine the significance of 2-phenyl ligand substitution as well as bridge type and placement on a series of gauche-1,2‘-bridged metallocenes. Comparison between the 1,1‘-bridged metallocene anti-ethylenebis(1-indenyl)zirconium dichloride and gauche-1 showed that the different bridge placements gave similar copolymerization reactivity in contrast to the different reactivities observed for anti-1,1‘-bridged dimethylsilylbis(2-phenylindenyl)zirconium dichloride and gauche-1,2‘-dimethylsilyl-bridged 3 respectively. Similar to trends observed with unbridged systems, substitution of a phenyl group in the 2-position resulted in a significant increase in α-olefin incorporation for 2 compared to unsubstituted 1. Ethylene-bridged 2 gave higher comonomer incorporation and a blockier comonomer distribution compared to dimethylsilylene-bridged 3.