The Impact of Substituents and Outgoing Ligands on the Catalytic Activity of Group 4 Metals Saligenin Complexes in the Synthesis of Ultrahigh Molecular Weight Polyethylene

Using new complexes of Group 4 metals with saligenin (2‐hydroxymethylphenol) ligands, it was shown that only titanium compounds activated by Al/Mg cocatalysts (Et 2 AlCl or Et 3 Al 2 Cl 3 + Bu 2 Mg) exhibit catalytic activity in ethylene polymerization. The authors attribute the lack of activity of the Zr and Hf complexes to differences in the redox potentials of these metals, based on the assumption that the catalytically active particle contains reduced Ti(III). Traditional activators—alkylaluminoxanes, tetrakisperfluorophenylborates, and simple organoaluminum compounds (OAC)—are unable to activate these complexes. A prerequisite for catalytic activity is the presence of Mg compounds, indicating the heterometallic (Ti‐Mg) nature of the active particle. Titanium complexes catalyze the synthesis of UHMWPE with a productivity of up to 3940 kg of PE mol −1 h −1 atm −1 . UHMWPE films obtained by solventless processing with subsequent uniaxial orientation drawing have a tensile modulus up to 120 GPa and tensile strength up to 2.3 GPa, which indirectly proves the low degree of macromolecule's entanglements. Titanium complexes, stabilized with dichlorosaligenin ligand, are also capable of catalyzing the synthesis of high molecular weight ethylene‐propylene‐5‐ethylidene‐norbornene terpolymers (EPDM).