Silica‐supported metallocenes: stereochemical comparison between homogeneous and heterogeneous catalysis

Abstract

Abstract Propylene was polymerized in the presence of the isospecific Et(Ind) 2 ZrCl 2 (Et: ethylene, Ind: indenyl) and the aspecific (Ind) 2 ZrCl 2 complexes in solution and anchored to SiO 2 and SiO 2 /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 2 /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) 2 ZrCl 2 SiO 2 and (Ind) 2 ZrCl 2 SiO 2 produce the same prevailingly isospecific polymer suggests that only isospecific centers are formed in this case, independently of the metallocene stereochemical structure.