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	{{#if:C[Si](C)(C)N([Na])[Si](C)(C)C|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 to 175 °C; 340 to 347 °F; 444 to 448 K
Boiling point	170 °C; 338 °F; 443 K (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 (77 °F), 100 kPa)
Infobox references

Sodium bis(trimethylsilyl)amide is the organosilicon 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 commercially available as a solid and it is soluble not only in ethers, such as THF or diethyl ether, but also in aromatic solvents, like 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.

Structure

Although the N-Na bond is polar covalent as a solid, when dissolved in nonpolar solvents this compound is trimeric, consisting of a central Na₃N₃ ring.^[2]

Applications in synthesis

NaHMDS is used as a base in organic synthesis. Typical reactions:

• To deprotonate ketones and esters to generate enolate derivatives.^[3]
• Generate carbenes by dehydrohalogenation of halocarbons. These carbene reagents add to alkenes to give substituted cyclopropanes and cyclopropenes.^[4]
• To deprotonation of phosphonium salts, generating Wittig reagents.

NaHMDS is also used as a base to deprotonate other compounds containing weakly acidic O-H, S-H, and N-H bonds. These include cyanohydrins and thiols.^[5]

NaHMDS is reagent to convert alkyl halides to amines in a two step process that begins with N-alkylation followed by hydrolysis of the N-Si bonds.

((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.

See also

• Metal bis(trimethylsilyl)amides

References