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

Abstract

We describe the successful synthesis of the first mixed-cation (pseudoternary) amidoborane, Na[Li(NH(2)BH(3))(2)], with theoretical hydrogen capacity of 11.1 wt%. Na[Li(NH(2)BH(3))(2)] crystallizes triclinic (P1) 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) Å(3) (Z = 2), as additionally confirmed by Density Functional Theory calculations. Its crystal structure is topologically different from those of its orthorhombic LiNH(2)BH(3) and NaNH(2)BH(3) constituents, with distinctly different coordination spheres of Li (3 N atoms and 1 hydride anion) and Na (6 hydride anions). Na[Li(NH(2)BH(3))(2)], which may be viewed as a product of a Lewis acid (LiNH(2)BH(3))/Lewis base (NaNH(2)BH(3)) 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.

Mixed-metal (Li, Al) amidoborane: synthesis and enhanced hydrogen storage properties

“…7), which are similar to the behaviour of other metallic amidoboranes. [10][11][12][13][14][15][16][17][18][19][20] In particular, upon decomposition, Li 3 AlH 6 -4AB exhibits a small exothermic peak at around 57 C, which is proposed to be the reaction of residual Li 3 AlH 6 (Fig. 1) with ammonia borane, and then a major hydrogen release peak at around 100 C, followed by some small peaks in the region of 116-150 C, consistent with the hydrogen release results from the mass spectra.…”

“…Apparently, the affinity of H dÀ in Li 3 AlH 6 and H d+ in NH 3 of AB is one of the main driving forces for this solid-phase reaction, accompanied by the release of H 2 , comparable to the mechanism for the formation of other metallic amidoboranes. [10][11][12][13][14][15][18][19][20] In order to acquire better information on the reaction products derived from Li 3 AlH 6 and AB, chemical bonds of the samples were detected by solid-state 11 B NMR and FTIR spectra. The 11 B NMR results ( Fig.…”

“…This result indicates the superior effects of the as-prepared mixed-metal (Li, Al) amidoborane on suppressing ammonia release compared with other dual-metal amidoboranes. [18][19][20] With regard to the Li 3 AlH 6 -5AB composite, the total weight loss is around 12 wt% over the whole decomposition, corresponding to 12 equiv. H 2 , which is also consistent with the volumetric results ($12.32 equiv.…”

Monoammoniate of Calcium Amidoborane: Synthesis, Structure, and Hydrogen-Storage Properties

“…As results of the introduction of a functional group by reacting ammonia borane with a stronger Lewis acid, that is, metal hydrides, a series of single-metal and double-metal amidoboranes consisting of metal cations and amidoborane anions were developed, including amidoboranes of Li, 7,8 Na, 7 K, 9 Ca, 10,11 Sr, 12 Y, 13 Na 2 Mg, 14 NaMg, 15 and NaLi. 16 These metal amidoboranes are found to exhibit significant improvement over the parent AB, including reduced dehydrogenation temperature with moderate dehydrogenation thermodynamics, improved dehydrogenation kinetics, and suppression of the release of volatile byproduct. In addition, intensive mechanistic investigations were also studied to understand the role of metal cation in the improved dehydrogenation properties.…”

Li–Na ternary amidoborane for hydrogen storage: experimental and first-principles study

“…It would be interesting to employ the "multicomponent" strategy onto the metal amidoborane systems to obtain an optimal combination of thermodynamic and kinetic properties. More recently, Fijalkowski et al 37 synthesized the Li-Na mixed amidoborane, Na[Li(NH 2 BH 3 ) 2 ]…”