A family of Group 4 post-metallocene catalysts, supported by fluorine-functionalized tridentate ligands with the fluorine substituent in the locality of the metal center, is described. For the first time, the contentious C-H...F-C interaction has been characterized by a neutron diffraction study, which has allowed the position of the hydrogen atoms to be accurately determined. The nature of the weak intramolecular C-H...F-C contacts in these complexes in solution and the solid state was probed by using multinuclear NMR spectroscopy in tandem with neutron and X-ray crystallography. Evidence is presented to demonstrate that the spectroscopic C-H...F-C coupling occurs "through-space" rather than "through-bond" or by MF coordination. The titanium catalysts exhibit excellent activities and high co-monomer incorporation in olefin polymerization. The observed intramolecular C-H...F-C interactions are important with regards to potential applications in polyolefin catalysis because they substantiate the proposed ortho-F...H(beta) ligand-(polymer chain) contacts derived from DFT calculations for the remarkable fluorinated phenoxyimine Group 4 catalysts. Compared with agostic and co-catalyst...metal contacts, weak attractive noncovalent interactions between a polymer chain and a judiciously designed "active" ligand is a new concept in polyolefin catalysis.

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The surprising impact of substituents that are seemingly remote from the active site upon the olefin polymerization characteristics of group 4 catalysts supported by pyridine-2-phenolate-6-(σ-aryl) ancillary ligands are described. Excellent ethylene polymerization activities (up to 22 kg mmol -1 h -1 (mol/L C2) -1 ) with borate cocatalysts are observed at 100 °C. On the basis of an X-ray crystal structure, a steric origin is proposed for the effect, which influences polymerization behavior by modulating catalyst conformation. However, excessively bulky substituents adjacent to the catalytic center can counteract this effect and give diminished efficiencies.

The Zr(IV) complexes [Zr(L1)X2(D)] [H2L1 = 2,6-di(3-tert-butyl-5-methylphen-2-ol)pyridine; X = Cl, D = thf (1), OEt2 (2), acetophenone (3), benzophenone (4), 2-acetonaphthone (5), Cl[HPR3] {R = Me (6), Et (7); R3 = Me2Ph (8)}; X = CH2Ph (9)] have been synthesized, and the crystal structures of 3, 4, and 7 have been determined. These catalysts, assisted by the robustness and chelating strength of the pyridine-bis(phenolate) moiety, exhibit excellent activities for ethylene polymerization in conjunction with MAO. Studies to assess the impact of the donor group during the catalytic process suggest that the same active species is generated by 1−8/MAO and the donor group does not play an active role. Even higher activities are observed for the 1/iBu3Al/Ph3CB(C6F5)4 system in ethylene polymerization and propylene copolymerization reactions (36 590 and 15 700 g of polymer (mmol of catalyst)-1 h-1, respectively), with the latter displaying good C3 incorporation (25.4 mol % C3). Insight into the catalytic behavior of the 1/MAO system has been derived from GPC and NMR characterization of the polymers prepared under different reaction conditions. 1H and 13C NMR end-group analyses reveal resonances for saturated methyl chain-end groups only and undetectable or negligible levels of unsaturated vinyl chain ends. This indicates that for the polymerization chain-transfer mechanism, the conventional β-H transfer reactions to the metal/monomer are insignificant and the unusual chain transfer to Al pathway is vastly dominant.