A mixed-cation mixed-anion borohydride NaY(BH 4) 2Cl 2
(2012) International Journal of Hydrogen Energy — Vol. 37, n° 10, p. 8428-8438 (2012)
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- A new sodium-yttrium borohydride-chloride, NaY(BH 4) 2Cl 2, is obtained by a combination of mechanochemical synthesis and annealing of NaBH 4-YCl 3 mixtures and is characterized by in-situ synchrotron radiation X-ray powder diffraction, density functional theory, thermal analysis and vibrational spectroscopy. Several simultaneous and coupled reactions occur during the synthesis, also yielding Na 3YCl 6 and Na(BH 4) 1-xCl x besides the title compound. The polymeric pseudo-orthorhombic crystal structure of NaY(BH 4) 2Cl 2 (space group P2/c) is built of edge- and corner-sharing octahedral coordination polyhedra of yttrium (4Cl + 2BH 4) and sodium (2Cl + 4BH 4). The structure is isomorphous to the high temperature polymorph of NaYCl 4. The BH 4 units in NaY(BH 4) 2Cl 2 are located only on the larger of the two independent anion sites in NaYCl 4. Density functional theory optimization of the experimental structure suggests that the BH 4 units act as η 3-ligands (face-sharing) towards yttrium and η 1-ligands (corner-sharing) towards sodium. Raman spectroscopy confirms this BH 4 configuration. NaY(BH 4) 2Cl 2 decomposes at ∼300°C under formation of Na 3YCl 6, while the latter compound at higher temperatures reacts with Na(BH 4) 1-xCl x to form NaCl and possibly amorphous products. The reactions are associated with mass losses of 2.62 and 3.78 wt% for the NaBH 4-YCl 3 (3:1) and (4:1) samples, respectively. © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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Ravnsbæk, D. B., Ley, M. B., Lee, Y.-S., Hagemann, H., D’Anna, V., Cho, Y. W., Filinchuk, Y., & Jensen, T. R. (2012). A mixed-cation mixed-anion borohydride NaY(BH 4) 2Cl 2. International Journal of Hydrogen Energy, 37(10), 8428-8438. https://doi.org/10.1016/j.ijhydene.2012.02.130 (Original work published 2012)