Lithium amide

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Lithium amide
IUPAC name	Lithium amide
Other names	Lithamide
Identifiers
CAS number	[7782-89-0]
Properties
Molecular formula	LiNH₂
Molar mass	22.96 g/mol
Appearance	white solid
Density	1.178 g/cm³
Melting point	380 - 400 °C
Solubility in water	Reacts vigorously in water
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Lithium amide is an inorganic compound with the chemical formula Li⁺NH₂^-, i.e. it is composed of a lithium cation, and the conjugate base of ammonia. It is a white solid with a tetragonal crystal structure.

1 Lithium amides
- 1.1 Examples
2 See also
3 References
4 External links

[edit] Lithium amides

The anionic conjugate bases of amines are known as amides. Thus lithium amide may also refer to lithium salts of amines e.g. Li⁺NR₂^-. An example of a lithium amide is lithium diisopropylamide (LDA), which is quite commonly used.

Lithium amide can be made by adding lithium metal to liquid ammonia:

Li + NH₃ → LiNH₂ + 0.5 H₂

Lithium amides in general can be similarly formed, substituting ammonia with the appropriate amine:

Li + R₂NH → LiNR₂ + 0.5 H₂

Lithium amides are very reactive compounds and can act as strong bases. Unless the nitrogen atom is hindered, as in the case of LDA, they can also act as nucleophiles.

[edit] Examples

The lithium salt of 2,2,6,6-tetramethylpiperidine has been crystalised as a tetramer:

Tetrameric lithium amide.^[1]

On the other hand, the lithium derivative of di-(1-phenylethyl)amine crystallises as a trimer:

Trimeric lithium amide.^[2]

It is also possible to make mixed oligomers of metal alkoxides and amides. ^[3] These are related to the super bases 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.

[edit] See also

[edit] References

^ M.F. Lappert, M.J. Slade, A. Singh, J.L. Atwood, R.D. Rogers and 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.
^ D.R. Armstrong, K.W. Henderson, A.R. Kennedy, W.J. Kerr, F.S. Mair, J.H. Moir, P.H. Moran and R. Snaith, Dalton Transactions, 1999, 4063.
^ K.W. Henderson, D.S. Walther and 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.