Zirconium bisamidinate complexes with sterically demanding ligands: structure, solution dynamics, and reactivity

Edwin Otten, Peter Dijkstra, Cindy Visser, Auke Meetsma, Bart Hessen

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27 Citations (Scopus)

Abstract

Bisamidinate zirconium dichloride and dimethyl complexes with the sterically demanding amidinate ligands [PhC(NAr)(2))](-) (A) and [PhC(NAr)(NAr')](-) (B) (Ar = 2,6-(Pr2C6H3)-Pr-i; Ar' = 2,6-Me2C6H3) were prepared. The steric demand of ligand A induces the unusual trans geometry in trans-(A)(2)ZrCl2, whereas (A)(2)ZrMe2 and (B)(2)ZrX2 (X = Cl, Me) adopt the more usual cis-X-2 geometry. The dynamic behavior of these complexes in solution was studied by 1D and 2D H-1 NMR spectroscopy. Reaction of (A)(2)ZrMe2 with H-2 leads, after stepwise hydrogenolysis of the Zr-Me bonds, to cyclometalation of the two amidinate ligands. The same product was obtained by thermolysis of the dimethyl complex. The square pyramidal five-coordinate 10 valence electron cationic monomethyl species [(A)(2)ZrMe](+) was generated and structurally characterized. Remarkably, the compound is unreactive toward ethylene, H-2, and CO. The sterically slightly less encumbered species [(B)(2)ZrMe](+) does polymerize ethylene, albeit with modest activity.

Original languageEnglish
Pages (from-to)4374-4386
Number of pages13
JournalOrganometallics
Volume24
Issue number18
DOIs
Publication statusPublished - 29-Aug-2005

Keywords

  • OLEFIN POLYMERIZATION CATALYSTS
  • ZIEGLER-NATTA POLYMERIZATION
  • BIS CHELATE COMPLEXES
  • LOW-VALENT CHEMISTRY
  • CONFIGURATIONAL REARRANGEMENTS
  • COORDINATION CHEMISTRY
  • CIS-M(AB)2X2 COMPLEXES
  • CRYSTAL-STRUCTURES
  • MAIN-GROUP
  • ETHYLENE POLYMERIZATION

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