Saal Thomas, Haiges Ralf, Christe Karl O
Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1661, USA.
Dalton Trans. 2023 Dec 12;52(48):18143-18147. doi: 10.1039/d3dt02944a.
The low-temperature protonation of trifluoroacetic acid with the superacids HF/SbF and HF/AsF resulted in the syntheses of the first examples of trifluoromethylcarboxonium salts. The less acidic trifluoromethylacetamide was also protonated in the same fashion, resulting in exclusive protonation of the carbonyl function. Their [SbF] and [AsF] salts were characterized by crystal structures, vibrational and multinuclear NMR spectra, and by electronic structure calculations. These salts are thermally unstable, colorless solids, stabilized by very strong hydrogen bonding. The proton NMR resonances of the [CFC(OH)][SbF] and [CFC(OH)][AsF] salts occur at an unprecedented 16.0 and 15.7 ppm, respectively, thus extending the upper limit of the range of observed proton NMR chemical shifts from 14 to 16 ppm.
用超强酸HF/SbF和HF/AsF对三氟乙酸进行低温质子化反应，首次合成了三氟甲基羧鎓盐。酸性较弱的三氟乙酰胺也以同样的方式被质子化，导致羰基官能团发生专一性质子化。它们的[SbF]盐和[AsF]盐通过晶体结构、振动光谱和多核NMR光谱以及电子结构计算进行了表征。这些盐是热不稳定的无色固体，通过非常强的氢键作用得以稳定。[CFC(OH)][SbF]盐和[CFC(OH)][AsF]盐的质子NMR共振分别出现在前所未有的16.0和15.7 ppm处，从而将观察到的质子NMR化学位移范围的上限从14 ppm扩展到了16 ppm。
