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]
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| Names | |
|---|---|
| Preferred IUPAC name Potassium 1,1,1-trimethyl-N-(trimethylsilyl)silanaminide | |
| Other names Potassium hexamethyldisilazidePotassium hexamethylsilazane[1] | |
| Identifiers | |
3D model (JSmol) | |
| Abbreviations | KHMDS |
| ChemSpider | |
| ECHA InfoCard | 100.102.263 |
PubChem CID | |
| UN number | 3263 |
CompTox Dashboard (EPA) | |
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| Properties | |
| KSi 2C 6NH 18 | |
| Molar mass | 199.4831 g mol−1 |
| Appearance | White, opaque crystals |
| Reacts | |
| Hazards | |
| GHS labelling: | |
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| Danger | |
| H314[2] | |
| P280, P305+P351+P338, P310[2] | |
| Related compounds | |
Other cations | Lithium bis(trimethylsilyl)amide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
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.