Subsequently, the bidentate halogen bond donors (m/p-1) were coordinated with halides (chloride, bromide, iodide) as representative anions. In all cases, a bidentate binding motif was obtained. A comparison with the analogous data of the fluorinated XB donors 2 confirmed the superior Lewis acidity of the carborane derivatives. In tetrahydrofuran (a likely choice of solvent due to solubility considerations), strong exergonic binding was observed for the halides, with an unexpected maximum for the bromide complexes (Table , entries 5-7 vs. entries 8-10, as well as entries 11-13 vs. entries 14-16). The carborane-based XB-donors also coordinated reasonably strongly to the neutral substrates acetone and acetonitrile in simulated toluene ( [a] with low-frequency entropy corrections by Grimme.