Propylene was polymerized in the presence of the isospecific Et(Ind),ZrCI, (Et: ethylene, Ind: indenyl) and the aspecific (Ind),ZrCl, complexes in solution and anchored to S O , and SiO,/MAO (MAO: methylaluminoxane) supports. From the stereochemical analysis of the polypropene samples obtained it can be deduced that i) the same active species is formed when a metallocene is in solution and when it is anchored to the SiO,/MAO support and ii) a completely different active species is formed when the metallocene is anchored to the silica. The fact that both systems Et(Ind),ZrCI,-SiO, and (Ind),ZrC1,--Si02 produce the same prevailingly isospecific polymer suggests that only isospecific centers are formed in this case, independently of the metallocene stereochemical structure.
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