On the Structure of [K(crypt-222)]+ CF3−

Richard L. Harlow, Jordi Benet-Buchholz, Fedor M. Miloserdov, Andrey I. Konovalov, William J. Marshall, Eduardo C. Escudero-Adán, Eddy Martin, Anton Lishchynskyi, Vladimir V. Grushin

Research output: Contribution to journalArticleAcademicpeer-review

12 Citations (Scopus)

Abstract

Due to disorder, [K(crypt-222)]+ CF-3 (1) is crystallographically indistinguishable from its isomer, a 1:1 fluoroform clathrate of deprotonated [K(crypt-222)]+, [K(crypt-222{-H+})]·CHF3 (2). In our preceding publications, 1 was characterized on the basis of combined X-ray diffraction, NMR, reactivity, labeling, acid-base, and DFT studies. Herein we report that neither incorporation of deuterium nor any other transformation of [K(crypt-222)]+ is observed in the presence of CD3OD/CD3OK at 70 °C or CD3S(O)CD2K/(D6)DMSO at 23 °C over hours and even days. Since fluoroform is easily and quickly deprotonated under such conditions, the demonstrated greater acidity of CHF3 relative to [K(crypt-222)]+ provides additional evidence in favor of 1 and against 2. Likewise, crystal packing analysis and DFT calculations support 1, which has now been refined in the ultimately correct space group R32. Our previously drawn conclusions regarding [K(crypt-222)]+ CF-3 and the existence of a ‘naked’ trifluoromethyl anion in a condensed phase remain valid. The recent alternative refinement (Becker and Müller, Chem. Eur. J. 2017, 23, 7081 – 7086) of our raw diffraction data has been improperly performed in the wrong space group to yield a non-charge-balanced model [K(crypt-222)]+·CHF3, which is hereby repudiated. Becker and Müller's attempts to resolve the charge balance issue have produced models that are inadequate from the perspective of both crystallography and chemistry.

Original languageEnglish
Article numbere1800015
JournalHelvetica chimica acta
Volume101
Issue number4
DOIs
Publication statusPublished - Apr 2018
Externally publishedYes

Keywords

  • cryptands
  • disorder
  • free (‘naked’) ions
  • trifluoromethyl anion
  • X-ray structure determination

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