Highly Fluorinated (sigma-Aryl)-Chelating Titanium(IV) Post-Metallocene: Characterization and Scalar [C-H center dot center dot center dot F-C] Coupling

The observation of weak intramolecular C-H center dot center dot center dot F-C interactions in group 4 (sigma-aryl)-chelating complexes using NMR spectroscopic and neutron diffraction studies was recently reported. In this work, a new titanium(IV) catalyst precursor supported by a tridentate pyridine-2-phenolate-6-(sigma-aryl) ligand, featuring a metal center surrounded by multiple CF3 substituents, has been synthesized. The nature of intramolecular interactions in the bis(benzyl) complex in solution was probed using multinuclear NMR spectroscopic experiments (including [H-1,F-19]-HMQC and -HMBC), which reveal scalar coupling across C-H center dot center dot center dot F-C interactions between methylene hydrogens and the proximal CF3 group on the sigma-aryl (but not the phenolate) moiety. High activities are observed for ethylene polymerization at different temperatures, which exceed those for the Bu-t-phenolate congener.