Pure and Applied Chemistry

Abstract: After a brief introduction to the electronic structure of the three-dimensionally aromatic icosahedral closo-monocarbadodecaborate anion CB₁₁H₁₂^-, some recent results for its permethylated version, CB₁₁Me₁₂^- and three highly reactive electroneutral analogs are presented and discussed. These are the radical CB₁₁Me₁₂^·, the boronium ylide CB₁₁Me₁₁ with a naked boron vertex, and the isomeric carbonium ylide with a naked carbon vertex. These ylides are probably better viewed as unusual types of singlet borylene and carbene, respectively.