Potassium hexamethyldisilazide

Structural formula
General
Surname	Potassium hexamethyldisilazide
other names	KHMDS; Potassium bis (trimethylsilyl) amide;
Molecular formula	C 6 H 18 KNSi 2
Brief description	moisture-sensitive, light brown powder
External identifiers / databases
EC number	609-880-6
ECHA InfoCard	100.115.605
PubChem	3251421
ChemSpider	21171158
Wikidata	Q903636
properties
Molar mass	199.48 g mol −1
Physical state	firmly
Melting point	158-162 ° C
solubility	Decomposes with water; soluble in tetrahydrofuran, diethyl ether, benzene, toluene;
safety instructions
GHS labeling of hazardous substances danger
H and P phrases	H: 314
	P: 280-305 + 351 + 338-310
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium hexamethyldisilazide ( KHMDS for short ) is the potassium salt of hexamethyldisilazane . It is a strong, sterically hindered , non- nucleophilic base. It is often used for deprotonation, similar to LDA and lithium tetramethylpiperidide (LTMP). Its lithium analogue, lithium hexamethyldisilazide (LHMDS), has similar properties.

Presentation and extraction

KHMDS is made from hexamethyldisilazane (also bis (trimethylsilyl) amine ) by reaction with potassium hydride in THF , whereby hydrogen is released:

{\ displaystyle \ mathrm {(CH_ {3}) _ {3} {-} Si {-} NH {-} Si (CH_ {3}) _ {3} + KH \ longrightarrow}}

{\ displaystyle \ mathrm {(CH_ {3}) _ {3} {-} Si {-} N ^ {-} {-} Si (CH_ {3}) _ {3} + K ^ {+} + H_ {2} \}}

properties

KHMDS is a substance that is solid at room temperature and is decomposed by water with regression of the hexamethyldisilazane and potassium hydroxide . The substance is highly flammable and has a corrosive effect.

use

Potassium hexamethyldisilazide is used as a reagent in organic syntheses, for example in the stereoselective alkylation of amino acids in the Williams or Schöllkopf alkylation. Also in the synthesis of complexes of lanthanides it is used. On an industrial scale, KHMDS serves as an initiator in the production of polyethylene oxide .

literature

Encyclopedia of Reagents for Organic Synthesis , 1999-2013, John Wiley and Sons, Inc., entry for Potassium Hexamethyldisilazide, accessed September 13, 2017 .

Individual evidence

↑ ^a ^b ^c ^d e-EROS Encyclopedia of Reagents for Organic Synthesis , 1999-2013, John Wiley and Sons, Inc., entry for Potassium Hexamethyldisilazide, accessed September 13, 2017 .
↑ ^a ^b ^c ^d Jane Elizabeth Macintyre, Chapman, Hall: Dictionary of Inorganic Compounds , 1992, CRC Press , ISBN 0-412-30120-2 .
↑ ^a ^b ^c ^d data sheet Potassium bis (trimethylsilyl) amide from Sigma-Aldrich , accessed on November 3, 2016 ( PDF ).

[eEROS-1] -EROS Encyclopedia of Reagents for Organic Synthesis , 1999-2013, John Wiley and Sons, Inc., entry for Potassium Hexamethyldisilazide, accessed September 13, 2017 .

[dictoc-2] Jane Elizabeth Macintyre, Chapman, Hall: Dictionary of Inorganic Compounds , 1992, CRC Press , ISBN 0-412-30120-2 .

[Sigma-3] ta sheet Potassium bis (trimethylsilyl) amide from Sigma-Aldrich , accessed on November 3, 2016 ( PDF ).