Icosahedral Carborane Superacids and their Conjugate Bases Comprising H, F, Cl, and CN Substituents: A Theoretical Investigation of Monomeric and Dimeric Cages

摘要

Abstract Theoretical investigation of the H(CHB 11 X 11 ) (X=H, F, Cl, CN), H(CHB 11 X n Y 11‐n ) (X,Y=F, Cl; n=1,5), and dimeric (H(CHB 11 X 11 )) 2 (X=F, Cl) carborane superacids performed at the B3LYP/6‐311++G(d,p) theory level revealed the similarity of their equilibrium structures and the possibility of nearly barrierless hydrogen atom migration among the substituents attached to one side of the icosahedral CB 11 cage. The vertical electron detachment energies predicted at the OVGF/6‐311++G(3df,2pd) theory level for the conjugate bases (CHB 11 X 11 ) ? were found to span the 5.82–9.00?ev range. The acid strengths (manifested by the Gibbs free deprotonation energies spanning the 213–266?kcal/mol range) predicted for the icosahedral H(CHB 11 X 11 ) carborane systems confirm their superacidic properties which might be increased?even further by the attachment of the second carborane H(CHB 11 X 11 ) unit that leads to a dimeric structure mimicking a part of an experimentally observed H‐bridged polymeric chain. The Gibbs free deprotonation energy of the dimeric (H(CHB 11 Cl 11 )) 2 acid was predicted to be smaller by 17?kcal/mol than that of the corresponding monomeric H(CHB 11 Cl 11 ) acid.