Lithium bis(trimethylsilyl)amide
| Lithium bis(trimethylsilyl)amide | |
|---|---|
 |
|
|
lithium bis(trimethylsilyl)azanide |
|
|
Other names
Lithium bis(trimethylsilyl)amide and lithium hexamethyldisilazide |
|
| Identifiers | |
| CAS number | 4039-32-1  |
| Jmol-3D images | Image 1 |
|
|
| Properties | |
| Molecular formula | C6H18LiNSi2 |
| Molar mass | 167.326 g/mol |
| Appearance | White solid |
| Melting point |
71-72 °C |
| Boiling point |
80 - 84 °C (0.001 mm Hg) |
| Solubility in water | decomposes in water |
| Solubility | THF, hexane |
| Hazards | |
| Main hazards | flammable |
| Related compounds | |
| Related compounds | Sodium bis(trimethylsilyl)amide, Potassium bis(trimethylsilyl)amide |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
|
| Infobox references | |
Lithium bis(trimethylsilyl)amide (commonly abbreviated as LiHMDS, Lithium HexaMethylDiSilazide) is the organosilicon compound with the formula [(CH3)3Si]2NLi. This colourless solid is a strong non-nucleophilic base used for deprotonation reactions and as a ligand. When solvent-free, this compound is dimeric in solution, and trimeric in solid state.[1]
Contents |
[edit] Preparation
LiHMDS is commercially available but can also be prepared by deprotonation of bis(trimethylsilyl)amine with n-butyllithium:[2]
- [(CH3)3Si]2NH + C4H9Li → [(CH3)3Si]2NLi + C4H10
The compound can be purified by sublimation.
LiHMDS can often be prepared in situ then reacted, as in the enolate preparation shown below under "reactions".[3]
[edit] Reactions
LiHMDS is used to generate coordination complexes with low-coordination numbers, taking advantage of the steric bulk of the (tms)2N- ligand. Examples include M[N(tms)2]3 for M = Sc, Ti, V, Fe (tms = (CH3)3Si).[4] Treatment with trimethylsilyl chloride gives tris(trimethylsilyl)amine, which features a planar, 3-coordinate nitrogen.
In organic chemistry, LiHMDS is often used as a strong base, for example to form lithium acetylide,[5] or to form a lithium enolate, as here with benzylideneacetone:[3]
[edit] See also
[edit] References
- ^ Mootz, D.; Zinnius, A.; Böttcher, B. (1969). "Assoziation im festen Zustand von Bis(trimethylsilyl)amidolithium und Methyltrimethylsilanolatoberyllium". Angew. Chem. 81 (10): 398–399. doi:10.1002/ange.19690811015.
- ^ Amonoo-Neizer, E. H.; Shaw, R. A.; Skovlin, D. O.; Smith, B. C.; Rosenthal, Joel W.; Jolly, William L. (1966). "Lithium Bis(Trimethylsilyl)Amide and Tris(Trimethylsilyl)Amine". Inorg. Synth.. Inorganic Syntheses 8: 19–22. doi:10.1002/9780470132395.ch6. ISBN 9780470132395.
- ^ a b Danheiser, R. L.; Miller, R. F.; Brisbois, R. G. (1990), "Detrifluoroacetylative Diazo Group Transfer: (E)-1-Diazo-4-phenyl-3-buten-2-one", Org. Synth. 73: 134, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV9P0197; Coll. Vol. 9: 197
- ^ Donald C. Bradley, Richard G. Copperthwaite “Transition Metal Complexes of Bis(Trimethyl-silyl)Amine (1,1,1,3,3,3-Hexamethyldisilazane)” Inorganic Syntheses 1978, Volume 18, 112. doi:10.1002/9780470132494.ch18
- ^ Reich, Melanie (Aug 24, 2001). "Addition of a lithium acetylide to an aldehyde; 1-(2-pentyn-4-ol)-cyclopent-2-en-1-ol". ChemSpider Synthetic Pages. p. 137. http://cssp.chemspider.com/137. Retrieved 5 September 2010.
