Synthesis and Structures of Low-Valent Tungsten Complexes Bearing Chiral Oxazoline-Derived Ligands

A Pfaltz, Guy Lloyd-Jones

Research output: Contribution to journalArticlepeer-review

Abstract

The synthesis of low-valent tungsten (0 and II) complexes bearing chiral bidentate phosphino-oxazoline or bisoxazoline ligands is described. The structures of four of the complexes have been determined by single crystal X-ray analyses. Tungsten(II)-allyl complexes of the type [W(CO)2(PN)(C3H5)Cl] (PN = phosphino-oxazoline) are fluxional in solution, but can be crystallized as single diastereoisomers. The complex [W(CO)3(PN)(CH3CN)], which also crystallizes as a single diastereoisomer, is readily oxidized in solution and solid state, in stark contrast to analogous compounds bearing four carbonyl ligands [W(CO)4(PN)] or [W(CO)4(NN)] (NN = bisoxazoline) which were found to be stable. [W(CO)3(PN)(CH3CN)] functions as a highly enantioselective catalyst in allylic substitution reactions with dimethyl sodiomalonate, whereas complexes of the type [W(CO)2(PN)(Z-C3H4)X)] (Z = H, Ph; X = Cl, Br) failed to yield allylic alkylation products.

Original languageEnglish
Pages (from-to)361-367
Number of pages7
JournalZeitschrift fur naturforschung section b-A journal of chemical sciences
Volume50
Issue number3
Publication statusPublished - Mar 1995

Keywords

  • CHIRAL TUNGSTEN COMPLEXES
  • PHOSPHINO-OXAZOLINE LIGANDS
  • BISOXAZOLINE LIGANDS
  • TUNGSTEN ALLYL COMPLEXES
  • ASYMMETRIC CATALYSIS
  • CATALYZED ALLYLIC SUBSTITUTION
  • ALKYLATIONS

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