Carboxonium Derivatives of closo-Decaborate Anion [2,6-B10H8O2CC6H4R]– Based on Aromatic Carboxylic Acids: Synthesis and Physicochemical Properties

The series of carboxonium derivatives of the closo-decaborate anion of the general form [2,6-B10H8O2CC6H4R]–, where R = F, CH3, C3H7, and C6H5, were prepared. To obtain the target systems, the reaction between the [B10H11]– anion and aromatic carboxylic acids was used. This process took place in two stages through the formation of a monosubstituted derivative of the general form [2-B10H9OC(OH)C6H4R]–, where R = F, CH3, C3H7, and C6H5, followed by intramolecular cyclization, leading to the formation of the target disubstituted carboxonium derivatives. The structure of the [2,6-B10H8O2CC6H4-C6H5]– anion was determined by single-crystal X-ray diffraction. The resulting carboxonium derivatives are capable of protonation to form neutral systems of the general form [2,6-B10H8O2CC6H4R(Hfac)]0, where R = F, CH3, C3H7, C6H5. When a protonated carboxonium derivative of acetonitrile is added to a solution, a trisubstituted derivative of the general form [B10H7O2CC6H4R(NCCH3)]0 is formed.