Reaction of 2,8-Bis(<i>o</i>‑hydroxyaryl)quinolines with Group 4 Metal Alkyls Resulting in Three Distinct Coordination Modes of the Tridentate Ligand. X‑ray Structure of Complexes and Performance as Precursors in Ethylene Polymerization Catalysis

A series of bis­(<i>o</i>-hydroxyphenyl)­quinolines have been prepared, starting from 2,8-dibromoquinoline. Reaction of these new ligand precursors with group 4 tetrabenzyl complexes MBn₄ results in benzyl substitution of the azine fragment with the formation of amide complexes (M = Ti) or amine complexes with an N–H fragment coordinated to the metal (M = Zr, Hf). The third structural typeZr complexes where the aromatic system of the precursor remains intactcan be prepared through the reaction of the bis­(<i>o</i>-hydroxyphenyl)­quinolones with 4 mol of methyllithium, followed by ZrCl₄. The new complexes result in active polymerization catalysts when activated with MAO/borate cocatalysts on silica supports, resulting in polyethylene copolymers with very high molecular weights and multimodal MWDs.