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Neutron and X‐ray Diffraction and Spectroscopic Investigations of Intramolecular [CH⋅⋅⋅FC] Contacts in Post‐Metallocene Polyolefin Catalysts: Modeling Weak Attractive Polymer–Ligand Interactions
Author(s) -
Chan Michael C. W.,
Kui Steven C. F.,
Cole Jacqueline M.,
McIntyre Garry J.,
Matsui Shigekazu,
Zhu Nianyong,
Tam KaHo
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501054
Subject(s) - intramolecular force , polyolefin , metallocene , chemistry , crystallography , ligand (biochemistry) , polymer chemistry , polymerization , catalysis , agostic interaction , neutron diffraction , stereochemistry , polymer , metal , organic chemistry , crystal structure , biochemistry , receptor , layer (electronics)
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 CH⋅⋅⋅FC 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 CH⋅⋅⋅FC 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 CH⋅⋅⋅FC coupling occurs “through‐space” rather than “through‐bond” or by M⋅⋅⋅F coordination. The titanium catalysts exhibit excellent activities and high co‐monomer incorporation in olefin polymerization. The observed intramolecular CH⋅⋅⋅FC interactions are important with regards to potential applications in polyolefin catalysis because they substantiate the proposed ortho ‐F⋅⋅⋅H(β) 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.