NaSc(BH4)4: A novel scandium-based borohydride
(2010) Journal of Physical Chemistry C — Vol. 114, n° 2, p. 1357-1364 (2010)
Files
No attached file found for this publication.
Details
- Authors
- Abstract
- A new alkaline transition-metal borohydride, NaSc(BH4) 4, is presented. The compound has been studied using a combination of in situ synchrotron radiation powder X-ray diffraction, thermal analysis, and vibrational and NMR spectroscopy. NaSc(BH4)4 forms at ambient conditions in ball-milled mixtures of sodium borohydride and ScCl 3. A new ternary chloride Na3ScCl6 (P2 1/n, a = 6.7375(3) Å, b = 7.1567(3) Å, c = 9.9316(5) Å, β = 90.491(3)°, V = 478.87(4) Å3), isostructural to Na3TiCl6, was identified as an additional phase in all samples. This indicates that the formation of NaSc(BH 4)4 differs from a simple metathesis reaction, and the highest scandium borohydride yield (22 wt %) was obtained with a reactant ratio of ScCl3/NaBH4 of 1:2. NaSc(BH4)4 crystallizes in the orthorhombic crystal system with the space group symmetry Cmcm (a = 8.170(2) Å, b = 11.875(3) Å, c = 9.018(2) Å, V = 874.9(3) Å3). The structure of NaSc(BH4)4 consists of isolated homoleptic scandium tetraborohydride anions, [Sc(BH 4)4]-, located inside slightly distorted trigonal Na6 prisms (each second prism is empty, triangular angles of 55.5 and 69.1°). The experimental results show that each Sc3+ is tetrahedrally surrounded by four BH4 tetrahedra with a 12-fold coordination of H to Sc, while Na+ is surrounded by six BH4 tetrahedra in a quite regular octahedral coordination with a (6 + 12)-fold coordination of H to Na. The packing of Na+ cations and [Sc(BH4)4]- anions in NaSc(BH4)4 is a deformation variant of the hexagonal NiAs structure type. NaSc(BH4)4 is stable from RT up to ∼410 K, where the compound melts and then releases hydrogen in two rapidly occurring steps between 440 and 490 K and 495 and 540 K. Thermal expansion of NaSc(BH4)4 between RT and 408 K is anisotropic, and lattice parameter b shows strong anomaly close to the melting temperature. © 2010 American Chemical Society.
- Affiliations
ESRF, Grenoble (France) Chimie
Citations
Cerný, R., Severa, G., Ravnsbæk, D. B., Filinchuk, Y., D’Anna, V., Hagemann, H., Haase, D., Jensen, C. M., & Jensen, T. R. (2010). NaSc(BH4)4: A novel scandium-based borohydride. Journal of Physical Chemistry C, 114(2), 1357-1364. https://doi.org/10.1021/jp908397w (Original work published 2010)