STERIC AND ELECTRONIC EFFECTS OF R IN (2-(4-R-C6H4)INDENYL)(2)ZRCL2 CATALYSTS ON THE SYNTHESIS OF ELASTOMERIC POLYPROPYLENE

Metallocene catalysts derived from bis(2-arylindenyl)zirconium dichlor ide catalysts yield elastomeric stereoblock polypropylene. A study of the steric and electronic effects of varying the 4-substituent of bis( 2-(4-R-C6H4)indenyl)zirconium dichloride [(1 R=H, 2 R=Me, 3 R=Et, 4 R= nBu, 5 R=tBu, 6 R=SiMe3, 7 R=CF3, 8 R=Cl)] on propylene polymerization at 25, 50, 75 psig and bulk propylene revealed that the polymerizatio n behavior of these catalysts is not strongly influenced by the nature of the substituent in the 4-position of the 2-aryl substituent. Exami nations of the microstructure of the elastomeric polypropylenes produc ed showed that for catalysts 2-8 the isotacticities varied over a smal l range and were similar to those produced by catalyst 1 (20% less tha n or equal to [mmmm] less than or equal to 44%). The catalyst producti vities and molecular weights also showed the same trend. Complex 3 was crystallographically characterized and was found to crystallize in ex clusively the meso conformation. (C) 1998 Elsevier Science B.V. All ri ghts reserved.