title: Neutron and X-ray diffraction and spectroscopic investigations of intramolecular [C-H...F-C] contacts in post-metallocene polyolefin catalysts: modeling weak attractive polymer-ligand interactions.
abstract: 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.
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China. mcwchan@cityu.edu.hk
authors.forename: Michael C W
authors.initials: MC
authors.lastname: Chan
authors.forename: Steven C F
authors.initials: SC
authors.lastname: Kui
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Cole
authors.forename: Garry J
authors.initials: GJ
authors.lastname: McIntyre
authors.forename: Shigekazu
authors.initials: S
authors.lastname: Matsui
authors.forename: Nianyong
authors.initials: N
authors.lastname: Zhu
authors.forename: Ka-Ho
authors.initials: KH
authors.lastname: Tam