Study of Proton-Deuterium Exchange in Ten-Vertex Boron Hydrides

The effect of electron-donating and electron-withdrawing substituents on the proton-deuterium exchange in derivatives of the closo-decaborate anion in methanol-d₄ was studied. Introduction of the electron-donating hydroxy (alkoxy) group into the apical position of the boron cage strongly promotes the H-D exchange at the antipodal apical vertex, whereas introduction of the electron-withdrawing diazonium group stops the H-D exchange completely. The general order of the proton-deuterium exchange in equatorially-substituted derivatives [2-B₁₀H₉R]^n- is 10 > 1 >> 7,8 > 4 > 3,5 ≈ 6,9. Formation of dihydrogen bonds between 1- and 2-hydroxy derivatives of the closo-decaborate anion and alcohols was investigated and their possible role in the H-D exchange was discussed.