Lithium nitride

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Lithium nitride
Image:Lithium nitride.jpg
Systematic name Lithium nitride
Other names trilithium nitride
Molecular formula Li3N
Molar mass 34.83 g/mol
Density 1.270 g/cm³
Solubility (water)
Melting point 813°C
Boiling point
CAS number [26134-62-3]
Disclaimer and references

Lithium nitride is a compound of lithium and nitrogen with the formula Li3N. It is the only stable alkali metal nitride. The solid is a red or purple color, has a high melting point and is ionic. It has an unusual crystal structure which consists of two different types of layer, one sheet, composition Li2N, containing 6 coordinate lithium ions and the other consisting only of lithium ions. Solid lithium nitride is a fast ion conductor and has the highest conductivity of any inorganic lithium salt. It has been studied extensively as a solid electrolyte and an anode material for use in batteries. [1]. It can be formed by direct reaction of the elements, either by burning lithium metal in pure nitrogen gas or by reacting nitrogen gas with lithium dissolved in liquid sodium metal [2]. The second method gives a purer product. Lithium nitride reacts violently with water to produce ammonia:

Li3N (s) + 3 H2O (l) → 3 LiOH (aq) + NH3 (g)

All ionic nitrides display this pattern, due to the N3− ion being an extremely strong Bronsted base. It easily qualifies as a superbase. It is, in fact, a stronger base than the hydride ion, so deprotonates hydrogen itself:

Li3N (s) + 2 H2 (g) → LiNH2 (s) + 2 LiH (s).

Lithium nitride is being investigated as a potential storage medium for hydrogen gas, as the reaction is reversible at 270oC. Up to 11.5% by weight absorption of hydrogen has been achieved [3].

[edit] General references

[edit] Footnotes

  1. ^ US patent 4888258 (1989)
  2. ^ Barker M.G., Blake A.J, Edwards P.P., Gregory D.H., Hamor T. A., Siddons D. J., Smith S. E. Chem. Commun., 1999, 1187–1188
  3. ^ Zhitao Xiong, Jizhong Luo, Jianyi Lin and Kuang Lee Tan. Nature, November 21, 2002.

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