The interaction of the [B10H10](2-) cage with Lewis acids and the formation of decaborane derivatives by cage-opening reactions

The interaction of hydroborates M-2[B10H10] (M = NH4, Et4N, Bu4N, etc.) or Et4N[B10H9-NH2COCH3] with Lewis acids AIX(3) (X = Cl, Br, I) in the solid state is sufficiently strong to produce an increase of more than 85 cm(-1) of the BH stretching vibrations. A similar interaction was not observed for the hydroborate (NH4)(2)[B10H9I] owing to the electronegativity of the iodine substituent which hampers the electron donor properties of the cage. Hydrolysis of (AlX3)(n)-[B10H10](2-) adducts under mild conditions results in opening of the boron cage with the formation of halodecaboranes 6-B10H13X. It seems that this reaction proceeds only when the above adducts can form in a preliminary step. Pure hexane solutions of 6-B10H13X were easily obtained with a 45% yield for X = Cl or Br and a 30% yield when X = I.