Extended Data Table 4 HOMO–LUMO gaps (in eV) for free halosilylium ions and their adducts with the counteranion [HCB₁₁H₅Br₆]⁻ at the one-component X2C-PBE0/x2c-TZVPall-2c level of theory.^a

Me₂FSi⁺

7.77

5.56

Me₂ClSi⁺

6.84

5.53

Me₂BrSi⁺

6.16

5.42

Me₂ISi⁺

5.23

5.17

Et₂FSi⁺

6.44

5.56

Et₂ClSi⁺

6.03

5.50

Et₂BrSi⁺

5.78

5.39

Et₂ISi⁺

5.13

5.15

iPr₂FSi⁺

6.10

5.48

iPr₂ClSi⁺

5.67

5.42

iPr₂BrSi⁺

5.48

5.36

iPr₂ISi⁺

5.02

5.16

tBu₂FSi⁺

5.92

5.42

tBu₂ClSi⁺

5.48

5.34

tBu₂BrSi⁺

5.33

5.28

tBu₂ISi⁺

4.97

5.13