On the Structure of [K(crypt‐222)]+

Abstract

Due to disorder, [K(crypt‐222)]+ (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)]+ 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.