Structure and Properties of NaBH₄·2H₂O and NaBH₄

Abstract

Abstract NaBH 4 · 2H 2 O and NaBH 4 were studied by single‐crystal X‐ray diffraction and vibrational spectroscopy. In NaBH 4 · 2H 2 O, the BH 4 – 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 Å. Crystal structures and vibrational spectra of NaBr · 2H 2 O and NaBH 4 · 2H 2 O reveal many similarities. The unit cell volume of NaBH 4 · 2H 2 O increases linearly with temperature between 200 and 313 K. At 313–315 K, the hydrate decomposes into NaBH 4 and H 2 O, which react to release hydrogen.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)