A Possible Model for the Stereospecificity in the Syndiospecific Polymerization of Propene with Group 4A Metallocenes

Abstract

The techniques of conformational analysis to investigate the factors that determine the stereospecificity, previously applied to stereorigid model sites for the homogeneous isospecific Ziegler-Natta catalysis, are now extended to other stereorigid cationic model sites. For a model site including an isopropyl-(cyclopentadienyl-1-fluorenyl) ligand, a precise definition of the interactions that determine its enantiose-lectivity at the molecular level is presented. For other model sites including an isopropyl(cyclopentadienyl-1-indenyl) or an isopropyl(l-fluorenyl-3-methylcyclopentadienyl) ligand, on the basis of energy calculations, predictions of their stereospecific behavior are presented, which are in a qualitative agreement with the available experimental information. © 1991, American Chemical Society. All rights reserved.