Zirconocene Complexes with Cyclopenta[l]phenanthrene Ligands:  Syntheses, Structural Dynamics, and Properties as Olefin Polymerization Catalysts

(2-Methylcyclopenta[ l ]phenanthryl) 2 ZrCl 2 and (2-phenylcyclopenta[ l ]phenanthryl) 2 ZrCl 2 were synthesized and used, after activation with MAO, as catalysts for the polymerization of propene. The resulting polymers had low isotacticities (8−18% [mmmm]). Ligand rotation barriers for the corresponding Zr−dibenzyl derivatives were determined by dynamic NMR spectroscopy. Pathways and transition states for ligand rotation in this series of complexes were studied by molecular-mechanics calculations and are discussed in relation to the microstructure of the respective polymer products.