Structural\nInvestigation of Diprotonated Glycine,\nDiprotonated Glycine Methyl Ester, and Monoprotonated Glycinoyl Fluoride

Glycine and its methyl\nester hydrochloride were investigated\nin\nsuperacidic media HF/<i>M</i>F<sub>5</sub> (<i>M</i> = As, Sb). The diprotonated species were obtained as [<i>M</i>F<sub>6</sub>]<sup>−</sup> salts (<i>M</i> = As,\nSb). The colorless salts were characterized by vibrational spectroscopy,\nNMR spectroscopy, and single-crystal diffraction. Glycinoyl fluoride\nwas isolated for the first time as a solid and characterized by vibrational\nspectroscopy, NMR spectroscopy, and single X-ray diffraction. Glycinoyl\nfluoride was investigated in the superacidic medium HF/MF<sub>5</sub> (<i>M</i> = As, Sb). The salts of the diprotonated species\nwere obtained and characterized by vibrational spectroscopy. The experimental\ndata are discussed together with quantum chemical calculations at\nthe M06-2X/aug-cc-pVTZ level of theory.