Potassium bis(trimethylsilyl)amide

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Potassium bis(trimethylsilyl)amide (commonly abbreviated as KHMDS, Potassium(K) HexaMethylDiSilazide) or potassium hexamethyldisilazane[1] is the chemical compound with the formula ((CH3)3Si)2NK. It is a strong, non-nucleophilic base with an approximate pKa of 26 (compare to lithium diisopropylamide, at 36).[citation needed]

Potassium bis(trimethylsilyl)amide
Stereo, skeletal formula of potassium bis(trimethylsilyl)amide dimer
Ball and stick model of potassium bis(trimethylsilyl)amide dimer
Names
Preferred IUPAC name
Potassium 1,1,1-trimethyl-N-(trimethylsilyl)silanaminide
Other names
Potassium hexamethyldisilazide Potassium hexamethylsilazane[1]
Identifiers
3D model (JSmol)
Abbreviations KHMDS
ChemSpider
ECHA InfoCard 100.102.263 Edit this at Wikidata
UN number 3263
  • InChI=1S/C6H18NSi2.K/c1-8(2,3)7-9(4,5)6;/h1-6H3;/q-1;+1 ☒N
    Key: IUBQJLUDMLPAGT-UHFFFAOYSA-N ☒N
  • C[Si](C)(C)N([K])[Si](C)(C)C
Properties
KSi
2
C
6
NH
18
Molar mass 199.4831 g mol−1
Appearance White, opaque crystals
Reacts
Hazards
GHS labelling:
GHS05: Corrosive
Danger
H314[2]
P280, P305+P351+P338, P310[2]
Related compounds
Other cations
Lithium bis(trimethylsilyl)amide

Sodium bis(trimethylsilyl)amide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure

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The methylsilyl groups give KHMDS good solubility in most organic solvents. Solution structures are either solvated monomers or dimers (or mixtures thereof) with this depending on the coordinating power, concentration, and temperature of the solvent.[3] In general, weakly coordinating solvents such as toluene and N,N-dimethylethylamine give dimers, where as THF and diglyme gave monomers at high dilution.[3] In the solid state, the unsolvated compound is dimeric, with two potassium and two nitrogen atoms forming a square.[4] KHMDS conducts electricity poorly in solution and in the melt, which is attributed to very strong ion pairing.

See also

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References

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  1. ^ a b "Potassium Hexamethyldisilazane". sigmaaldrich.com. Retrieved 1 April 2023.
  2. ^ a b Potassium bis(trimethylsilyl)amide, Sigma-Aldrich
  3. ^ a b Spivey, Jesse A.; Collum, David B. (20 June 2024). "Potassium Hexamethyldisilazide (KHMDS): Solvent-Dependent Solution Structures". Journal of the American Chemical Society. doi:10.1021/jacs.4c03418. PMC 11373885.
  4. ^ Tesh, Kris F.; Hanusa, Timothy P.; Huffman, John C. (1990). "Ion pairing in [bis(trimethylsilyl)amido]potassium: The x-ray crystal structure of unsolvated [KN(SiMe3)2]2". Inorg. Chem. 29 (8): 1584–1586. doi:10.1021/ic00333a029.