Preparation and crystal structures of the complexes (η5-C5H3Me-CMe2-η5-C13H8)MCl2 (M=Zr or Hf): mechanistic aspects of the catalytic formation of a syndiotactic-isotactic stereoblock-type polypropylene

Article abstract of DOI:10.1016/0022-328X(95)00115-7

The reaction of MCl4 (M=Zr or Hf) with the dilithium salt of 2-methyl-3-cyclopentadienyl-2-fluorenylpropane in pentane leads to the formation of the complexes (η⁵-C5H3Me)-CMe2-η⁵-C13H8)MCl2.NMR and X-ray diffraction data show that the fluorenyl groups are η⁵ bonded in these complexes.When activated with methylaluminoxane or other appropriate ionizing agents, both complexes catalyze the polymerization of propylene in a di-stereospecific manner, to give syndiotactic-isotactic stereoblock polypropylene.Keywords: Zirconium; Hafnium; NMR spectroscopy; Crystal structure