Zirconium and Titanium Diamine Bis(phenolate) Catalysts for α-Olefin Polymerization: From Atactic Oligo(1-hexene) to Ultrahigh-Molecular-Weight Isotactic Poly(1-hexene)

Aiming at higher activities of group IV diamine bis(phenolate) catalysts in olefin polymerization, ligands containing electron-withdrawing groups have been introduced. The dibenzyl Zr complexes of these ligands lead to highly active 1-hexene catalysts upon activation yielding, however, low-molecular-weight atactic poly(1-hexene). In contrast, the corresponding titanium complexes are highly active and lead to ultrahigh-molecular-weight poly(1-hexene) of different isotacticities, dictated by the size of the phenolate substituents.