Lithium amide

Lithium amide or lithium azanide is an inorganic compound with the chemical formula LiNH2. It is a white solid with a tetragonal crystal structure.[1] Lithium amide can be made by treating lithium metal with liquid ammonia:[2]

2 Li + 2 NH3 → 2 LiNH2 + H2
Lithium amide

__ Li+
      __ N3−
      __ H+
Names
IUPAC name
Lithium amide
Other names
Lithium azanide
Lithamide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.062
UNII
  • InChI=1S/Li.H2N/h;1H2/q+1;-1 checkY
    Key: AFRJJFRNGGLMDW-UHFFFAOYSA-N checkY
  • InChI=1/Li.H2N/h;1H2/q+1;-1
    Key: AFRJJFRNGGLMDW-UHFFFAOYAO
  • [Li+].[NH2-]
Properties
LiNH2
Molar mass 22.96 g·mol−1
Appearance white solid
Density 1.178 g/cm3
Melting point 375 °C (707 °F; 648 K)
Boiling point 430 °C (806 °F; 703 K) decomposes
reacts
Solubility slightly soluble in ethanol
insoluble in ammonia
Thermochemistry
-182 kJ/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
3
1
2
W
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Other lithium amides

The conjugate bases of amines are known as amides. Thus, a lithium amide may also refer to any compound in the class of the lithium salt of an amine. These compounds have the general form LiNR2, with the chemical lithium amide itself as the parent structure. Common lithium amides include lithium diisopropylamide (LDA), lithium tetramethylpiperidide (LiTMP), and lithium hexamethyldisilazide (LiHMDS). They are produced by the reaction of Li metal with the appropriate amine:

2 Li + 2 R2NH → 2 LiNR2 + H2

Lithium amides are very reactive compounds. Specifically, they are strong bases.

Examples

Lithium tetramethylpiperidide has been crystallised as a tetramer.[3] On the other hand, the lithium derivative of bis(1-phenylethyl)amine crystallises as a trimer:[4]

Tetrameric lithium tetramethylpiperidide
Trimeric lithium bis(1-phenylethyl)amide

It is also possible to make mixed oligomers of metal alkoxides and amides.[5] These are related to the superbases, which are mixtures of metal alkoxides and alkyls. The cyclic oligomers form when the nitrogen of the amide forms a sigma bond to a lithium, while the nitrogen lone pair binds to another metal centre.

Other organolithium compounds (such as BuLi) are generally considered to exist in and function via high-order, aggregated species.

See also

References
  1. David, William I. F.; Jones, Martin O.; Gregory, Duncan H.; Jewell, Catherine M.; Johnson, Simon R.; Walton, Allan; Edwards, Peter P. (2007-02-01). "A Mechanism for Non-stoichiometry in the Lithium Amide/Lithium Imide Hydrogen Storage Reaction". Journal of the American Chemical Society. 129 (6): 1594–1601. doi:10.1021/ja066016s. ISSN 0002-7863. PMID 17243680.
  2. P. W. Schenk (1963). "Lithium amide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. p. 454.
  3. M.F. Lappert; M.J. Slade; A. Singh; J.L. Atwood; R.D. Rogers; R. Shakir (1983). "Structure and reactivity of sterically hindered lithium amides and their diethyl etherates: crystal and molecular structures of [Li{N(SiMe3)2}(OEt2)]2 and tetrakis(2,2,6,6-tetramethylpiperidinatolithium)". Journal of the American Chemical Society. 105 (2): 302–304. doi:10.1021/ja00340a031.
  4. D.R. Armstrong; K.W. Henderson; A.R. Kennedy; W.J. Kerr; F.S. Mair; J.H. Moir; P.H. Moran; R. Snaith (1999). "Structural studies of the chiral lithium amides [{PhC(H)Me}2NLi] and [PhCH2{PhC(H)Me}NLi·THF] derived from α-methylbenzylamine". Dalton Transactions: 4063–4068. doi:10.1039/A904725E.
  5. K.W. Henderson, D.S. Walther & P.G. Williard (1995). "Identification of a Unimetal Complex of Bases by 6Li NMR Spectroscopy and Single-Crystal Analysis". Journal of the American Chemical Society. 117 (33): 8680–8681. doi:10.1021/ja00138a030.
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