Sodium bis(trimethylsilyl)amide

Chemical compound From Wikipedia, the free encyclopedia

Sodium bis(trimethylsilyl)amide is the organosilicon compound with the formula NaN(Si(CH3)3)2. This species, usually called NaHMDS (sodium hexamethyldisilylamide), is a strong base used for deprotonation reactions or base-catalyzed reactions. 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]

Quick facts Names, Identifiers ...
Sodium bis(trimethylsilyl)amide
Names
Preferred IUPAC name
Sodium 1,1,1-trimethyl-N-(trimethylsilyl)silanaminide
Other names
Sodium hexamethyldisilazide
Sodium hexamethyldisilazane
Identifiers
3D model (JSmol)
Abbreviations NaHMDS
3629917
ChemSpider
ECHA InfoCard 100.012.713 Edit this at Wikidata
EC Number
  • 213-983-8
UNII
UN number 3263
  • InChI=1S/C6H18NSi2.Na/c1-8(2,3)7-
    9(4,5)6;/h1-6H3;/q-1;+1 X markN
    Key: WRIKHQLVHPKCJU-UHFFFAOYSA-N checkY
  • 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
  • C[Si](C)(C)N([Na])[Si](C)(C)C
Properties
NaN(Si(CH3)3)2
Molar mass 183.377 g·mol−1
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 202 °C (396 °F; 475 K) 2 mmHg
Reacts with water
Solubility in other solvents THF, benzene
toluene
Structure
Triangular pyramidal
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Highly flammable, corrosive
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation mark
Danger
H302, H312, H314, H332, H412
P260, P264, P270, P271, P273, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P322, P330, P363, P405, P501
Related compounds
Other cations
 Lithium bis(trimethylsilyl)amide
(LiHMDS)
Potassium bis(trimethylsilyl)amide
Related compounds
 Lithium diisopropylamide (LDA)
Sodium hydride
Potassium hydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X markN verify (what is checkYX markN ?)
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NaHMDS is quickly destroyed by water to form sodium hydroxide and bis(trimethylsilyl)amine.

Structure

Although the Na–N 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 strong base in organic synthesis. Typical reactions:

NaHMDS deprotonates compounds containing weakly acidic O–H, S–H, and N–H bonds. These include cyanohydrins and thiols.[5]

NaHMDS converts alkyl halides to amines in a two step process that begins with N-alkylation followed by hydrolysis of the N–Si bonds:

NaN(Si(CH3)3)2 + RX → RN(Si(CH3)3)2 + NaX
RN(Si(CH3)3)2 + H2O → O(Si(CH3)3)2 + RNH2

where X is a halogen and R is an alkyl.

This method has been extended to aminomethylation via the reagent CH3OCH2N(Si(CH3)3)2, which contains a displaceable methoxy group CH3O–.

See also

References

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