Protonation of p -Benzoquinone in Superacidic Solutions

Abstract

The reaction of p-benzoquinone in the binary superacidic systems XF/MF5 (M = As, Sb;X = H, D) leads to the formation of the corresponding salts [OC6H4(OX)][MF6] (M = As, Sb;X = H, D). Threefold excess of Lewis acid in relation to p-benzoquinone is required to form these salts quantitatively. The salts are characterized by infrared spectroscopy and in the case of [OC6H4(OH)][SbF6] (2) by a single-crystal X-ray structure analysis, according to which it is more correctly described as a double hemi-protonated salt of p-benzoquinone. The salt crystallizes in the triclinic space group P1 with one formula unit per unit cell. In the solid state the cations are arranged in chains, linked via O center dot center dot center dot(H)center dot center dot center dot O bonds. The vibrational spectra were compared to quantum chemical calculations of the cation [OC6H4(OH)](+).