Reactions of Dichloroacetyl Fluoride in Superacidic Media

Dichloroacetyl fluoride was investigated in the superacids HF/MF5 and DF/MF5 (M = As, Sb). The O-hemiprotonated species of dichloroacetyl fluoride is formed in the binary superacidic systems HF/MF5 and DF/MF5 (M = As, Sb) as hexafluoridoarsenates and hexafluoridoantimonates. With an excess of the strong Lewis acid SbF5 dichloroacetyl fluoride reacts under the formation of the oxonium salt [CCl2HCF2OX2][SbF6] in the superacidic system XF/SbF5 (X = H, D) after HF- or DF-addition, respectively. The colorless salts were characterized by low-temperature vibrational spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction. [CCl2HC(OH)F][(CCl2HCOF)2H][SbF6][Sb2F11] and [CCl2HCF2OH2][SbF6] crystallize in the monoclinic space groups P21/c and P21/m, respectively, with two formula units per unit cell each. The crystal structure of the oxonium salt shows strong O(-H)···F hydrogen bonds and strong F···F interactions. The experimental data are discussed together with quantum chemical calculations at the ωB97XD/aug-cc-pVTZ-level of theory.