Synthesis and Structural Investigation of Protonated Haloacetyl Fluorides

Herein, we report the O ‐monoprotonated species of chloroacetyl fluoride and fluoroacetyl fluoride in the binary superacidic systems HF/ M F 5 and DF/ M F 5 ( M =As, Sb) as hexafluoridoarsenates and hexafluoridostibates. The colorless salts were characterized by low temperature vibrational spectroscopy, low temperature NMR spectroscopy and single‐crystal X‐ray diffraction. [CClH 2 C(OH)F][SbF 6 ] crystallizes in the monoclinic space group P 2 1 /c with four formula units per unit cell and [CH 2 FC(OD)F][SbF 6 ] in the triclinic space group P 1 ‾ with two formula units per cell. The experimental data are discussed together with quantum chemical calculations at the ω B97XD/aug‐cc‐pVTZ‐level of theory. Protonation leads to significant shortening of the C−F bond due to back‐donation of fluorine lone‐pair electrons.