Convenient Route to Monocarba-closo-dodecaborate Anions

Monocarba-closo-dodecaborate anion [HCB₁₁H₁₁]⁻ (1) and its derivatives are superb anionic species with remarkably high chemical stability and low nucleophilicity. Here we report a convenient two-step synthesis of 1, starting from nido-decaborane­(14) (2) through the formation of arachno-[CB₉H₁₄]⁻ (3). In this protocol, the use of Me₃NH⁺ as a countercation of 1 and 3 enables facile cation exchange, thus greatly enhancing access to the carbaborate anions. We also demonstrate an efficient perchlorination reaction of 1 into [HCB₁₁Cl₁₁]⁻ (4). The detailed synthetic protocols as well as the full analytical data presented herein should provide a general and reliable recipe for the synthesis of these anionic species.