Isospecific polymerization of propene by new indolyl-pyridylamido Zr(IV) catalysts

New zirconium complexes bearing indolyl-pyridylamido ligands [−NNN−] have been synthesized and used as catalysts in ethylene and propene polymerization in the presence of AliBu2H/MAO as cocatalytic system. Complexes 1 and 2, bearing ligands with a different steric hindrance on the carbon bridging the pyridine and the aniline moieties, exhibited remarkable catalytic activity for ethylene and propene polymerization, affording ultrahigh molecular weight polymers with monomodal molecular weight distributions. Moreover, the presence of the 2-isopropyl phenyl substituent on the bridging carbon (complex 2) resulted in higher stereoselectivity and regioselectivity providing a polypropylene sample with an [mmmm] content up to 96% and 1.3% of regioinversion. On the other hand, the change of the substituents of the aniline moiety (complex 3) gave a zirconium complex which resulted completely inactive both in the ethylene and propene polymerization.

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► New Zr complexes bearing indolyl-pyridylamido ligands have been synthesized.
► The complexes catalyze the polymerization of ethylene and propene.
► High molecular weight linear PEs and highly isotactic PPs were obtained.
► The size of the substituents on the ligands plays a critical role in the catalysis.