Synthesis, characterization and polymerization properties of isopropylidene(η5-3-neomenthylcyclopentadienyl)(η5-fluorenyl)zirconium dichloride

The reaction of neomenthylcyclopentadiene with acetone solution led to 6,6-dimethyl-3-neomenthylfulvene (6). The bridged 3-neomenthylcyclopentadienyl-2-fluorenylpropane (7) has been isolated after reaction of 6 with fluorenyllithium salt. The reaction of ZrCl4 with the dilithium salt of 7 in diethyl ether yields the complex isopropylidene(η5-3-neomenthylCp)-(η5-9-fluorenyl)ZrCl2 (4) as a 60:40 mixture of diastereomers. The complex was fully characterized by single-crystal X-ray diffraction and NMR methods. Complex 4 is an active catalyst for the homogeneous polymerization of propylene when activated by methylaluminoxane (MAO). The polypropylene polymer produced with 4 has lower molecular weight and a lower degree of syndiotactic or hemiisotactic stereoregularity, but a higher degree of isotactic character (mm triad of 63%) than the polymer produced with the syndiospecific catalyst isopropylidene(Cp)(Flu)ZrCl2 (1a) under these conditions.