Hydrogen bond energy spectroscopic determination of decachlorocarboran with different bases

To test whether one intensity rule proposed by Johansen was applicable to carboranes, a thermodynamic determination of ΔH was made by studying the temperature dependence of the equilibrium constant of the reaction =C-H+B yields reversibly =C-H...B. The equilibrium constants were determined by i.r. spectroscopy on the basis of the intensity of bands of valence C-H oscillations of free C-methyl-B-decachlorine-o-carborane (MedChC) and MedChC in an N-complex. It is shown that in the case of N-complexes of carboranes as well as of all other N-complexes, a linear dependence is observed between ΔH and ΔAsup(1/2), but in this equation the proportionality coefficient is higher than in the canonical form of the intensity rule, having a value of 3.39. (author)