Structure and properties of NaBH4•2H2O and NaBH4

NaBH4 center dot 2H(2)O and NaBH4 were studied by single-crystal Xray diffraction and vibrational spectroscopy. In NaBH4 center dot 2H(2)O, the BH4- anion has a nearly ideal tetrahedral geometry and is bridged with two Na+ ions through the tetrahedral edges. The structure does not contain classical hydrogen bonds, but reveals strong dihydrogen bonds of 1.77-1.95 angstrom. Crystal structures and vibrational spectra of NaBr center dot 2H(2)O and NaBH4 center dot 2H(2)O reveal many similarities. The unit Cell volume of NaBH4 center dot 2H(2)O increases linearly with temperature between 200 and 313 K. At 313-315 K, the hydrate decomposes into NaBH4 and H2O, which react to release hydrogen. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).