A Cholestenyl‐Substituted Bis(indenyl)zirconocene‐Derived Homogeneous Ziegler Catalyst for Stereoselective Propene Polymerization

Abstract

Abstract(–)1‐5‐Cholesten‐3β1‐yl tosylate (6) undergoes SN2 substitution with indenyllithium to give (–)1‐3‐(5‐cholesten‐3α1‐yl)indene (7), which is subsequently deprotonated by methyllithium to give the cholestenyl‐substituted indenyllithium reagent 8. Its reaction with 0.5 molar equivalents of ZrCl4(THF)2 furnished the three bis[3‐(5‐cholesten‐3α1‐yl)indenyl]ZrCl2 diastereoisomers in a ratio of 9a: 9b: 9c60 : 16 : 24. The major organometallic reaction product 9a was recovered isomerically pure and used for the generation of an active homogeneous metallocene/alumoxane Ziegler‐type catalyst for stereoselective propene polymerization. The catalyst derived from the non‐bridged chirally substituted bis(indenyl)zirconocene complex 9a produces partially isotactic polypropylene almost completely by enantiomorphic site control in the temperature range from – 50 to + 15°C.