Reactivity and Mechanistic Studies of Stereocontrol for Ziegler—Natta Polymerization Utilizing Doubly-Silylene Bridged Group 3 and Group 4 Metalocenes

A family of zirconocene, yttrocene, and scandocene complexes have been prepared utilizing an easily modified doubly bridged ligand array, (1,2-SiMe_2)_2{η^5-C_5H_2-4-R}{η^5-C_5H-3,5-CHMe_2)_2}, developed in our laboratories. Variations in ligand array substitution and metal center provide complexes that exhibit a range of stereoselectivities and activities in α-olefin polymerizations. A series of C_(s-) and C_(1-) symmetric metallocenes have been utilized for the preparation of polypropylene and polypentene under various polymerization conditions. Analysis of the resulting polymer microstructures has provided valuable information about the factors that dictate syndiospecificity, as well as common error forming mechanisms for these systems.