C2- and Cs-symmetric diamidodichlorotitanium complexes: Syntheses, structures and 1-hexene polymerization catalysis

Frank Heatley, Francis S. Mair, Robin G. Pritchard, Rebecca J. Woods

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The complexes l-[CMe2{CHMeN(2-Pri-C6H 4)}2TiCl2] (2) and u-[CMe2{CHMeN(2,6-Pr2iC6H3)} 2TiCl2] (3), C2- and Cs-symmetric analogues, respectively, of McConville's C2v hexene polymerization precatalyst [(CH2)3{N(2,6-Pr2i-C6H3)}2TiCl2] (1), were prepared by high-dilution salt-elimination from the lithium amides and characterized spectroscopically and crystallographically. Complex 2, though less active than 1, was a highly active catalyst of polymerization of 1-hexene when activated by MAO. Complex 3 was inactive under similar conditions. NMR analysis confirmed that there were more mmmm pentads in polymer produced by 2 than in the statistically atactic material produced by 1, though the isotacticity index was not high. The results are interpreted in terms of an isotactic/atactic block structure, caused by syn/anti fluxion of the two 2-isopropylphenyl rings in 2. Kinetic profiles and polydispersities were consistent with a slow initiation step involving monomer, followed by rapid propagation, with some chain transfer to aluminium and only a small extent of β-hydride elimination. The rubber-like polymers were indistinguishable by thermal analysis from those prepared by Ziegler-Natta catalyst systems. © 2005 Published by Elsevier B.V.
    Original languageEnglish
    Pages (from-to)2078-2086
    Number of pages8
    JournalJournal of Organometallic Chemistry
    Volume690
    Issue number8
    DOIs
    Publication statusPublished - 15 Apr 2005

    Keywords

    • Diamido ligands
    • Polyhexen
    • Titanium

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