Zirconocene complexes with cyclopenta[l]phenanthrene ligands: Syntheses, structural dynamics, and properties as olefin polymerization catalysts

(2-Methylcyclopenta[I]phenanthryl)(2)ZrCl2 and (2-phenylcyclopenta[I]phenan thryl)(2)ZrCl2 were synthesized and used, after activation with MAO, as cat alysts for the polymerization of propene. The resulting polymers had low is otacticities (8-18% [mmmm]). Ligand rotation barriers for the corresponding Zr-dibenzyl derivatives were determined by dynamic NMR spectroscopy. Pathw ays and transition states for ligand rotation in this series of complexes w ere studied by molecular-mechanics calculations and are discussed in relati on to the microstructure of the respective polymer products.