Metallocenes with Cp Ring-Fused to Chalcogen Heterocycles: Synthesis and Polymerization Results

Abstract

Substituted metallocene ligands containing cyclopentadiene ring fused to either selenophene or benzo[b]tellurophene were prepared following methods previously developed for analogs containing sulfur. 5-Methyl-4,5-dihydro-cyclopenta[b]-selenophen-6-one ( 2 ) and 3-Methyl-3,4-dihydro-benzo[b]cyclopenta[d]telluraphen-2-one ( 7 ) (major isomers) were prepared by polyphosphoric acid catalyzed Friedel-Crafts acylation/Nazarov cyclization of methacrylic acid onto selenophene and respectively benzo[b]tellurophene. Following reduction of the ketone to alcohol, then dehydration, the chalcogen-containing cyclopentadiene olefins were prepared. The olefins were deprotonated with n-butyllithium followed by either bridging with dichlorodimethylsilane, deprotonation and metallation, or deprotonation and direct metallation. In this manner, isomeric mixtures of –rac/-meso dimethylsilanediylbis(η⁵-5-Methyl-cyclopenta[b]selenophen-yl)zirconium dichloride ( 5 ) Bis(η^5?2-methyl-cyclopenta[b][1 Brintzinger, H. H., Fischer, D., Mülhaupt, R., Rieger, B. and Waymouth, R. 1995. Angew. Chem., 107: 1255[Crossref] , [Google Scholar]]benzotelluraphen-yl)zirconium dichloride ( 9 ) were prepared and characterized. Complexes formed active olefin polymerization catalyst when activated with methylalumoxane. Polymerization results with ethylene and propylene are included.