Regioirregular propene insertion in polypropenes synthesized with unbridged bis(2-aryl)indenyl zirconium dichloride catalysts: Implications on activity

Catalysts of the type bis(2-(3,5-R2C6H3)indenyl)zirconium dichloride/MAO (2 , R = H; 3, R = CF3) were investigated for regioregularity of monomer inser tion in bulk propene polymerization and compared to the isospecific catalys t rac-(ethene)bis(indenyl)zirconium dichloride/MAO (1). The amount of regio irregular propene insertions were in the range of 0.1-0.5 mol % and followe d the trend 2 < 3 < 1. Comparison of polymerizations in the presence and ab sence of hydrogen revealed a 4-10-fold increase in productivity for catalys ts 2 and 3 in the presence of hydrogen but only a slight increase in produc tivity with 1. For catalysts 2 and 3, only 2,1-erythro internal regioerrors were observed, whereas 1 produced both 2,1-erythro and 2,1-threo misinsert ions. Evidence for ethene insertion following a 2,1-regioerror was obtained by copolymerization of (C2H4)-C-13 with propene using catalyst 3. The corr elation between number of 2,1-misinsertions and catalyst activity is discus sed.