Potassium bis(trimethylsilyl)amide

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 pK_a of 26 (compare to lithium diisopropylamide, at 36).^{[citation needed]}

Potassium bis(trimethylsilyl)amide

Names
Preferred IUPAC name Potassium 1,1,1-trimethyl-N-(trimethylsilyl)silanaminide
Other names Potassium hexamethyldisilazide Potassium hexamethylsilazane[1]
Identifiers
CAS Number	40949-94-8 Y
3D model (JSmol)	Interactive image
Abbreviations	KHMDS
ChemSpider	21171158 N
ECHA InfoCard	100.102.263
PubChem CID	3251421
UN number	3263
CompTox Dashboard (EPA)	DTXSID00390655
InChI InChI=1S/C6H18NSi2.K/c1-8(2,3)7-9(4,5)6;/h1-6H3;/q-1;+1 N Key: IUBQJLUDMLPAGT-UHFFFAOYSA-N N
SMILES C[Si](C)(C)N([K])[Si](C)(C)C
Properties
Chemical formula	KSi 2C 6NH 18
Molar mass	199.4831 g mol−1
Appearance	White, opaque crystals
Solubility in water	Reacts
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314[2]
Precautionary statements	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). N verify (what is YN ?) Infobox references

Structure

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

• Metal bis(trimethylsilyl)amides

References

1. "Potassium Hexamethyldisilazane". sigmaaldrich.com. Retrieved 1 April 2023.
2. Potassium bis(trimethylsilyl)amide, Sigma-Aldrich
3. 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.