NMR spectroscopic observation of a metal-free acetylide anion

Yoshiyuki Tanaka, Makoto Arakawa, Yohei Yamaguchi, Chieko Hori, Masahiro Ueno, Takeyuki Tanaka, Tatsushi Imahori, Yoshinori Kondo

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

A metal-free acetylide was observed by using NMR spectroscopy. Metal-free acetylides are closely related to reactive intermediates (carbanions) in solution; therefore, they have been regarded as unobservable species. However, we generated this highly reactive and unstable species through the deprotonation of phenylacetylene by using the strong nonmclallic phosphazene base tBu-P4. In the presence of tBu-P4, the J coupling between the ethynyl carbon and hydrogen nuclei (1JCH) of phenylacetylene disappeared: this indicates the deprotonation of the alkyne terminal. Furthermore, a large low-field shift (approximately 90 ppm) of the alkyne carbon resonance was observed. We concluded that we have observed a metal-free carbanion with a formal charge on an sp-hybridized carbon atom for the first time.

Original languageEnglish
Pages (from-to)581-585
Number of pages5
JournalChemistry - An Asian Journal
Volume1
Issue number4
DOIs
Publication statusPublished - 2006 Nov 9

Keywords

  • Carbanions
  • Density functional calculations
  • Metal-free acetylide anions
  • Phosphazenes
  • Reactive intermediates

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry

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