Na[Li(NH2BH3)2] – the first mixed-cation amidoborane with unusual crystal structure

Karol J. Fijalkowski, Radostina V. Genova, Yaroslav Filinchuk, Armand Budzianowski, Mariana Derzsi, Tomasz Jaroń, Piotr J. Leszczyński and Wojciech Grochala

Dalton Trans., 2011,40, 4407-4413 OI: 10.1039/C0DT01491E

Na[Li(NH2BH3)2] first mixed-cation amidoborane

We describe the successful synthesis of the first mixedcation (pseudoternary) amidoborane, Na[Li(NH2BH3)2], with theoretical hydrogen capacity of 11.1 wt%. Na[Li(NH2BH3)2] crystallizes triclinic (P[1 with combining macron]) with a=5.0197(4)Å, b=7.1203(7)Å, c=8.9198(9)Å, α=103.003(6)°, β=102.200(5)°, γ=103.575(5)°, and V=289.98(5)Å3 (Z=2), as additionally confirmed by Density Functional Theory calculations. Its crystal structure is topologically different from those of its orthorhombic LiNH2BH3 and NaNH2BH3 constituents, with distinctly different coordination spheres of Li (3 N atoms and 1 hydride anion) and Na (6 hydride anions). Na[Li(NH2BH3)2], which may be viewed as a product of a Lewis acid (LiNH2BH3)/Lewis base (NaNH2BH3) reaction, is an important candidate for a novel lightweight hydrogen storage material. The title material decomposes at low temperature (with onset at 75°C, 6.0% mass loss up to 110°C, and an additional 3.0% up to 200°C) while evolving hydrogen contaminated with ammonia.

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