Theoretical study of exopolyhedral substitution in the hexahydro-closo-hexaborate anion

摘要

The proximity of values of the electronic chemical potential A mu of the [B6H6](2-) and OH- anions allows us to assume the possibility of participation of [B6H6](2-), instead of OH-, in chemical reactions proceeding in a basic medium. A theoretical study of reactions of the [B6H6](2-) anion with halogenoalkanes has been carried out with chloromethane and 2-chlorobutane as examples using the B3LYP/6-311G* approach. The interaction of [B6H6](2-) with CH3Cl in a certain sense is similar to the reaction of formation of primary alcohols from primary halogenoalkanes under the influence of an alkali and results in substituted product [B6H6CH3](-), i. e. the protonated form of anion [B6H5CH3](2-). At the same time, interaction of [B6H6](2-) with 2-chlorobutane has to proceed similar to the reactions of elimination of secondary and tertiary halogenoalkanes in an alkaline medium to form unsaturated compounds and according to the calculations has to result in 2-butene. Transition states (TSs) have been located and the energy profiles of reactions have been calculated. In the course of the interaction with CH3Cl, the exopolyhedral substitution in the [B6H6](2-) anion can proceed practically without the activation barrier (h similar to 1.8 kcal/mol), whereas the elimination reaction of 2-chlorobutane under the influence of [B6H6](2-) has to overcome an insignificant threshold of h similar to 4.2 kcal/mol.