Sequential Immobilization of Ansa-Hafnocene Complexes for Propene Polymerization

25 October 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

We report the immobilization of the ultrarigid ansa-hafnocene complexes [Me2Si(Ind*)2HfCl2] (Ind* = 7,(3',5'-Di-tert-butylphenyl)-4-methoxy-2-methylindenyl) on silica as heteregeneous catalysts for propene polymerization. A sequential three-step synthesis on the siliceous surface led to pre-catalysts of the generalized structure SiO2-Si(Ind*)2HfCl2, which possess the silylene bridge of the substituted bis(indenyl) ligand directly attached to the surface. The immobilized pre-catalysts show very poor performance in the polymerization of propene, independent on the reaction conditions and the employed silica. Based on the results, we suggest that the close proximity of the catalyst to the surface combined with the steric congestion provoked by the ligand prevents a continuous polymerization, most likely due to a blockage of the catalytically active sites with growing polymer.

Keywords

Propene Polymerization
Metallocene Catalysts
Catalyst Immobilization

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