Fig. 4. Computed apical and equatorial isomers of Me₂PhSi⁺[CHB₁₁H₅Br₆]^– (top), Me₃Si⁺[CHB₁₁H₅Br₆]^– (middle) and MePh₂Si⁺[CHB₁₁H₅Br₆]^– (bottom). Si–Br bond lengths are given in Å and relative free energy differences (kcal mol^–1) are shown in parentheses.