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

Abstract

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)₂O. 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.