The C-F...cation interaction: an ammonium complex of a hexafluoro macrocyclic cage compound.
An ammonium complex of the hexafluoro cage compound 1 was isolated and its structure was elucidated by X-ray crystallographic analysis. The C-F bonds are elongated by the complexation, which is clear evidence of C-F...cation interaction. The driving force of NH4(+) inclusion is the C-F cation interaction, but the C-F...HN+ hydrogen bond does not contribute to this complexation. The crystal structure of the NH4+ complex 1 shows short C-F...HN+ contacts (2.286-2.662 A). Furthermore, it shows that closer F...H(+)(-N) distances give a larger F...H(+)-N angle. Although such structural features seem to indicate the existence of C-F...HN+ hydrogen bonds, the spectral data (1H NMR, 19F VT-NMR, and IR spectroscopy) did not support the existence of hydrogen bonds. Thermodynamic parameters, log K(s) (4.6 +/- 0.1, 298 K), deltaH (-5.3 +/- 0.1 kcal mol(-1)), and deltaS (3.2 +/- 0.3 cal mol(-1) K(-1)), of the complexation were obtained in CDCl3/CD3CN mixture.
Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan. takemura@rc.kyushu-u.ac.jp
H
H
Takemura
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Kon
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M
Yasutake
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Nakashima
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T
Shinmyozu
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T
Inazu
D002412:Cations; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*
D002412:Cations; D000644:Quaternary Ammonium Compounds