Synthesis, Structure, and Olefin Polymerization Catalytic Behavior of Aryl-Substituted Zirconocene Dichlorides

Standard ligand-substitution reactions afforded moderate yields of (PhC5H4)2ZrCl2 (1), (1,3-Ph2C5H3)CpZrCl2 (2), [1,3,-(C6F5)2C5H3]CpZrCl2 (5), and [1,2,4-(C6F5)2C5H3]CpZrCl2 (6). Crystal structures of 1, 2, 6, and [(C6F5)C5H4]2HfMe2 (7) were obtained. Physicochemical studies (CV, IR) show that C6F5 groups are strongly electron-withdrawing compared to phenyl groups. In ethylene-1-hexene copolymerization reactions using 1, 2, (C6F5C5H4)CpZrCl2 (3), (C6F5C5H4)2ZrCl2 (4), and 5 (toluene solution, methylalumoxane cocatalyst), C6F5 substituents decrease catalytic activity but increase comonomer incorporation compared to phenyl substituents.