Tridentate [N,N,O] Schiff-base group 4 metal complexes: Synthesis, structural characterization and reactivity in olefin polymerization.

New complexes LTiCl3(1), LZrCl3(2) and LHfCl3(3) (L=(E)-2-tert-butyl-6[(quinoline-8-ylimino)methyl]phenolate) have been synthesized and fully characterized by multinuclear NMR, mass spectrometry and X-ray diffractometry. The three isostructural complexes show distorted octahedral geometries. Complexes 1–3 were tested as catalysts for ethylene polymerization under a variety of experimental conditions. Reasonable productivities were achieved after activation by methylaluminoxane (MAO) under moderate temperature and pressure conditions (e.g., 50 ◦C and 6 atm). Complexes 1–3 were also tested as precatalysts for the polymerization of propene. Interestingly, polymerization by 1-MAO at −20 ◦C afforded an isotactic polypropylene containing 5% isolated regioirregular units in threo configuration. This very unusual microstructure implicates that both primary and secondary monomer insertions occur with the same enantioface selectivity, at variance with what is observed in the case of metallocene catalysts