Design of Novel Group 4 ansa-Metallocene Compounds and their Role as Catalysts in the Polymerization of Olefins

Abstract

Since the discovery by Sinn and Kaminsky that zirconocene complexes in the presence of MAO were able to polymerize olefins there has been a dramatic expansion in this field. One of the main focuses of this research is centred on the tailoring of metallocene complexes that can direct the catalytic reaction in producing polymers with desired physical properties. Ligand design is therefore of utmost importance in the development of "made to measure" single-site olefin polymerization catalysts. In addition the introduction of functional groups in the ligand system can be later exploited in immobilizing the catalyst on different substrates.

In this communication we describe the synthetic strategies used in the design of group four ansa-metallocene complexes and the application of these compounds as catalysts in the polymerization of ethylene and propylene. The principal design aims addressed include: 1. Variable substitution at the ansa-carbon bridging atom of the metallocene catalysts 2. Synthesis of hydride silylene ansa-bridged complexes that act as hydrosilylation reagents. 3. Functionalization of ansa-metallocene complexes 4. Synthesis of C1 symmetric ansa-metallocene catalysts which are isospecfic in the polymerization of propylene