Tricoordinate Organochromium(III) Complexes Supported by a Bulky Silylamido Ligand Produce Ultra-High-Molecular Weight Polyethylene in the Absence of Activators

Hsuch-Ju Liu, Irene C. Cai, Alexey Fedorov, Micah S. Ziegler, Christophe Copéret, T. Don Tilley

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Low-coordinate organoCr(III) complexes supported by the silylamido ligand –N(SiMe3)DIPP (DIPP = 2,6-diisopropylphenyl) are ethylene polymerization catalyst precursors without the need of additional cocatalyst. The reaction of CrCl3(THF)3with 3 or 2 equiv. of LiN(SiMe3)DIPP yields either a four-membered cyclometalated Cr complex or Cr[N(SiMe3)DIPP]2Cl, respectively, with no trace of Cr[N(SiMe3)DIPP]3. Addition of 1 equiv. of LiN(SiMe3)DIPP to Cr[N(SiMe3)DIPP]2Cl also leads to the four-membered metallacycle, which upon heating transforms to a new six-membered Cr metallacycle, likely via a σ-bond metathesis step. Cr[N(SiMe3)DIPP]2Cl can be readily converted to bis(amido)Cr(III) vinyl and alkyl complexes Cr[N(SiMe3)DIPP]2R (R = vinyl, Bn, and Me). All of these structurally characterized low-coordinate Cr(III) complexes with a Cr–C bond initiate the polymerization of ethylene in the absence of activators or cocatalysts, producing ultra-high-molecular weight polyethylene.

Original languageEnglish
Pages (from-to)859-867
Number of pages9
JournalHelvetica Chimica Acta
Volume99
Issue number11
DOIs
StatePublished - 1 Jan 2016

Keywords

  • Cr(III) Amides
  • Cyclometalation
  • Ethylene polymerization
  • Low-coordinate complexes
  • Phillips catalyst

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