Sodium bis(trimethylsilyl)amide

Sodium bis(trimethylsilyl)amide
Preferred IUPAC name Sodium bis(trimethylsilyl)amide
Systematic name Sodiobis(trimethylsilyl)amine
Other names Sodium hexamethyldisilazane Sodium hexamethyldisilazide
Identifiers
Abbreviations	NaHMDS
CAS number	1070-89-9 N
PubChem	2724254 Y
ChemSpider	21169873 Y
EC number	213-983-8
UN number	UN 3263
Beilstein Reference	3629917
Jmol-3D images	Image 1
SMILES C[Si](C)(C)N([Na])[Si](C)(C)C
InChI InChI=1S/C6H18NSi2.Na/c1-8(2,3)7- 9(4,5)6;/h1-6H3;/q-1;+1 N Key: WRIKHQLVHPKCJU-UHFFFAOYSA-N Y InChI=1/C6H18NSi2.Na/c1-8(2,3)7-9(4,5)6;/h1-6H3;/q-1;+1/rC6H18NNaSi2/c1-9(2,3)7(8)10(4,5)6/h1-6H3 Key: WRIKHQLVHPKCJU-JSJAVMDOAQ InChI=1S/C6H18NSi2.Na/c1-8(2,3)7-9(4,5)6;/h1-6H3;/q-1;+1 Key: WRIKHQLVHPKCJU-UHFFFAOYSA-N
Properties
Molecular formula	C6H18NNaSi2
Molar mass	183.37 g/mol
Appearance	off-white solid
Density	0.9 g/cm3, solid
Melting point	171-175 °C, 444-448 K, 340-347 °F
Boiling point	170 °C, 443 K, 338 °F (2 mmHg)
Solubility in water	reacts with water
Solubility in other solvents	THF, benzene toluene
Structure
Molecular shape	Triangular pyramidal
Hazards
R-phrases	R11 R15 R34
S-phrases	S16 S24/25
Main hazards	Highly flammable, corrosive
Related compounds
Other cations	Lithium bis(trimethylsilyl)amide (LiHMDS) Potassium bis(trimethylsilyl)amide
Related compounds	Lithium diisopropylamide (LDA) KH
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium bis(trimethylsilyl)amide is the chemical compound with the formula ((CH₃)₃Si)₂NNa. This species, usually called NaHMDS (sodium hexamethyldisilazide), is a strong base used for deprotonation reactions or base catalyzed reaction. Its advantages are that it is available as a solid and it is soluble in a wide range of nonpolar solvents such as THF, diethyl ether, benzene, and toluene by virtue of the lipophilic TMS groups.^[1]

NaHMDS is quickly destroyed by water to form sodium hydroxide and bis(trimethylsilyl)amine.

Contents 1 Structure 2 Applications in synthesis 3 See also 4 References

Structure

It is common that polar organometallic reagents are depicted as ions, when in fact such species are rarely ionic. The structure shown in the figure is a better representation - the sodium atom is attached to the nitrogen atom via a polar covalent bond. When unsolvated, this compound is trimeric in the solid state.^[2]

Applications in synthesis

NaHMDS is widely used as a base for C-H acids. Typical reactions:

• To deprotonate ketones and esters to generate enolate derivatives.
• Generate halocarbenes such as CHBr and CHI by dehydrohalogenation of the CH₂X₂ (X = Br, I). These carbene reagents add to alkenes to give substituted cyclopropanes.
• To generate Wittig reagents via deprotonation of phosphonium salts.
• Deprotonate cyanohydrins.

NaHMDS is also used as a base for N-H acids.

NaHMDS reacts with alkyl halides to give amine derivatives:

(CH₃)₃Si)₂NNa + RBr → (CH₃)₃Si)₂NR + NaBr

(CH₃)₃Si)₂NR + H₂O → (CH₃)₃Si)₂O + RNH₂

This method has been extended to aminomethylation via the reagent (CH₃)₃Si)₂NCH₂OMe, which contains a displaceable methoxy group.

• To deprotonate precursors to give stable carbenes.

See also

• Metal bis(trimethylsilyl)amides

References