The rearrangement of dicarboranyl methyl cation: a possible synthetic strategy toward cationic closo-tricarbaboranes

Abstract

A quantitative study on cationic closo-tricarbaboranes proved their stability and a possible use for them as weakly coordinating ions due to the dispersal of positive charge throughout the cage. The current study explores computationally a synthetic strategy toward their realization in parallel with the benzyl cation-tropylium ion rearrangement. This study shows that cage expansion along with the incorporation of a carbon atom into the cage starting from the dicarboranyl methyl cation is in the realm of the possible. The rearrangements are found to have favorable energy barriers with one transition state. The geometry of the dicarboranyl methyl cations (benzyl cation analogues) with bent CH₂ groups favors the rearrangement into the tropylium analogues. Thus, the comparison of well-known benzyl ion-tropylium ion rearrangement with similar reactions among polyhedral boranes unravels the feasibility of cationic tricarboranes.