Even stronger binding was anticipated for the tridentate system 3, which was likewise readily accessible from 1,3,5tribromo-benzene via a Sonogashira coupling, followed by carborane formation, and subsequent iodination (Scheme 1). The enthalpic contribution to the association was indeed higher for the bromide and iodide complex (Table , entries 18-19), with approximately 10 kcal/mol vs. roughly 8-9 kcal/mol for m-1. However, this was counterbalanced by a now unfavorable entropic contribution of about 2 kcal/mol, which led overall to even slightly lower Gibbs free energies of binding. The carborane moieties in 3 can still rotate, so coordination to a halide will reduce the rotational degrees of freedom, which might explain the adverse entropic effect. In the titrations with chloride, a second weak binding event was found when a large excess of XB donor 3 was present, which is likely the coordination of one chloride to two molecules of 3. The much stronger 1:1 binding between chloride and Lewis acid 3 is overall noticeably stronger than the one of bromide and iodide. In this case, the entropy contribution is minor, and the complexation enthalpy is markedly stronger compared to the other halides (Table , entry 17).