Carboxonium derivatives based on closo-dodecaborate anions [1,2-B₁₂H₁₀O₂CR]^-: synthesis and molecular orbital analysis

Borylated carboxonium ions based on closo-dodecaborate anions were obtained by studying the interaction of [B12H12](2-) with some carboxylic acids (RCOOH, R = CH3, C2H5, C3H7, and C6H5) in the presence of electrophilic inducers. Several electrophilic inducers were tested, and the best results were achieved with BF3*(C2H5)(2)O. It was established that, as in the case of closo-decaborate carboxonium derivatives, the process of [1,2-B12H10O2CR]- preparation occurs through the formation of the monosubstituted carboxonium derivative [B12H11OC(OR ' )R](-), where R ' = H and C2H5. The structures of the tetrabutylammonium salts of the carboxonium derivative ((C4H9)4N)[1,2-B12H10O2CR] were established with the help of X-ray structure analysis. Comprehensive molecular orbital (MO) analysis was also carried out, and the nature of the interaction between the cluster cage and organic moiety was analysed theoretically.