Olefin polymerization behavior of titanium(IV) pyridine-2-phenolate-6- (σ-aryl) catalysts: Impact of "py-adjacent" and phenolate substituents

A series of Ti(IV) post-metallocene bis(benzyl) precatalysts supported by tridentate pyridine-2-phenolate-6-(σ-aryl) [O,N,C] ligands, featuring various substituents on the σ-aryl (directly adjacent to the pyridine ring: fluoro, trifluoromethyl, benzo [C4H4]) and phenolate groups (tert-butyl, trifluoromethyl, cumyl, 1,1-diphenylethyl), have been prepared. Multinuclear (including 1H, 13C, and 19F) NMR characterizations of the complexes have been performed. The principal purpose of this study was to investigate the impact of these substituents upon ethylene polymerization reactivity and polymer properties. The cumyl-phenolate σ-naphthyl Ti precatalyst, in conjunction with [Ph3C][B(C6F5)4], displays good activity and produces polyethylene with exceptionally high MW (Mn = 4 × 106) and an Mw/Mn value (2.5) approaching single-site character at 50 °C, but multisite behavior is apparent for other catalysts. DFT calculations have been performed to probe the polymerization behavior and the role of the py-adjacent su...