TY - JOUR
T1 - On the Structure of [K(crypt-222)]+ CF3−
AU - Harlow, Richard L.
AU - Benet-Buchholz, Jordi
AU - Miloserdov, Fedor M.
AU - Konovalov, Andrey I.
AU - Marshall, William J.
AU - Escudero-Adán, Eduardo C.
AU - Martin, Eddy
AU - Lishchynskyi, Anton
AU - Grushin, Vladimir V.
PY - 2018/4
Y1 - 2018/4
N2 - 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.
AB - 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.
KW - cryptands
KW - disorder
KW - free (‘naked’) ions
KW - trifluoromethyl anion
KW - X-ray structure determination
U2 - 10.1002/hlca.201800015
DO - 10.1002/hlca.201800015
M3 - Article
AN - SCOPUS:85045892764
SN - 0018-019X
VL - 101
JO - Helvetica chimica acta
JF - Helvetica chimica acta
IS - 4
M1 - e1800015
ER -