PREPARATION AND CRYSTAL-STRUCTURES OF THE COMPLEXES (ETA(5)-C(5)H(3)ME-CME(2)-ETA(5)-C13H8)MCL(2) (M=ZR OR HF) - MECHANISTIC ASPECTS OF THE CATALYTIC FORMATION OF A SYNDIOTACTIC-ISOTACTIC STEREOBLOCK-TYPE POLYPROPYLENE

The reaction of MCl(4) (M = Zr or Hf) with the dilithium salt of 2-methyl-3-cyclopentadienyl-2-fluorenylpropane in pentane leads to the formation of the complexes (eta(5)-C(5)H(3)Me)-CMe(2)-eta(5)-C13H8)MCl(2). NMR and X-ray diffraction data show that the fluorenyl groups are eta(5) 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.