Intermolecular dihydrogen- and hydrogen-bonding interactions in diammonium closo-decahydrodecaborate sesquihydrate.

The asymmetric unit of the title salt, 2NH(4)(+).B(10)H(10)(2-).1.5H(2)O or (NH(4))(2)B(10)H(10).1.5H(2)O, (I), contains two B(10)H(10)(2-) anions, four NH(4)(+) cations and three water molecules. (I) was converted to the anhydrous compound (NH(4))(2)B(10)H(10), (II), by heating to 343 K and its X-ray powder pattern was obtained. The extended structure of (I) shows two types of hydrogen-bonding interactions (N-H...O and O-H...O) and two types of dihydrogen-bonding interactions (N-H...H-B and O-H...H-B). The N-H...H-B dihydrogen bonding forms a two-dimensional sheet structure, and hydrogen bonding (N-H...O and O-H...O) and O-H...H-B dihydrogen bonding link the respective sheets to form a three-dimensional polymeric network structure. Compound (II) has been shown to form a polymer with the accompanying loss of H(2) at a faster rate than (NH(4))(2)B(12)H(12) and we believe that this is due to the stronger dihydrogen-bonding interactions shown in the hydrate (I).