Synthesis of the phenoxonium cation of an α-tocopherol model compound crystallized with non-nucleophilic [B(C₆F₅) ₄]^- and (CB₁₁H₆Br₆) ^- anions

The phenoxonium cation of a vitamin E model compound has been crystallized using the non-nucleophilic carborane and tetrakis(pentafluorophenyl)borate counteranions. The crystal structures confirm the assignment of the unusually stable phenoxonium cation and indicate that there is a substantial shortening of the carbon-oxygen bond lengths of the para-carbon atoms in the phenolic ring and a substantial increase of the carbon-oxygen bond length at the quaternary carbon. The crystallographic data are in excellent agreement with structural predictions from molecular orbital calculations.