The ethylene-bridged pseudo-Cs symmetric ansa-zirconocene complexes, (1-fluorenyl-2-cyclopentadienylethane)zirconium dichloride (5a) and (1-fluorenyl-2-tetramethylcyclopentadienylethane)zirconium dichloride (5b), were synthesized and their molecular structures have been determined by single crystal X-ray diffraction studies. The complex 5a is very active toward propylene polymerization in the presence of methylaluminoxane (MAO), affording polypropylene with good syndiotacticity. In comparison with the known syndiotactic polypropylene catalytic system iPr(fluorenyl)(cyclopentadienyl)ZrCl2/MAO, 5a/MAO system is better in thermal stability, higher in activity and lower in syndiotacticity under the identical polymerization conditions. On the other hand, 5b/MAO system shows low activity and produces nearly atactic polypropylene with low molecular weight, which could be attributed to the increased electron density and steric bulkiness around the metal center.
Bibliographical noteFunding Information:
We gratefully acknowledge financial support provided by the Korea Science and Engineering Foundation and the Korea Advanced Industrial Technology.
- Pseudo-C symmetry
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry
- Materials Chemistry