Is There a Single Ideal Parameter for Halogen-Bonding-Based Lewis Acidity?

16 In the context of our studies to utilise halogen bonding in organocatalysis, we had performed orientating computations on simple halogen‐bond donors (halogen‐based Lewis acids) and had found an unexpected trend in the series of complexes CX 3 I⋅⋅⋅Cl − and CX 3 I⋅⋅⋅NH 3 (X=F, Cl, Br, I). 17 For instance, the trifluoromethyl group is surely more electronegative than the triiodomethyl group, and thus CF 3 I ( 2 ) should feature a deeper σ‐hole than CI 4 (CI 3 I, 5 ) and should consequently also form stronger complexes to both Lewis bases (Figure 2 ).

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