Monosilane

Structural formula
General
Surname	Monosilane
other names	Silicon hydride Silakan Silicon hydride Silane
Molecular formula	SiH 4
Brief description	colorless gas with an unpleasant odor
External identifiers / databases
CAS number 7803-62-5 EC number 232-263-4 ECHA InfoCard 100.029.331 PubChem 23953 Wikidata Q410572
properties
Molar mass	32.12 g mol −1
Physical state	gaseous
density	1.44 g l −1 (1013 h Pa , 0 ° C)
Melting point	−185 ° C
boiling point	−112 ° C
solubility	rapid hydrolysis in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 220-280 P: 210-377-381-410 + 403
MAK	Switzerland: 0.5 ml m −3 or 0.7 mg m −3
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Monosilane is the simplest representative of the silanes (also called silicon hydrides) and thus the silicon analogue of methane , CH ₄ . In contrast to methane, it has an unpleasant, repulsive odor.

Manufacturing

Monosilane can be made in the laboratory by reacting magnesium silicide with hydrochloric acid . Technical manufacturing process based on the hydrogenation of silicon tetrachloride with lithium in lithium chloride / potassium chloride - eutectic ,

${\displaystyle \mathrm {SiCl_{4}\ +\ 4\ LiH\longrightarrow \ SiH_{4}\ +\ 4\ LiCl} }$

or on the dismutation of hydrogenchlorosilanes, such as. B. trichlorosilane .

Chemical properties

Monosilane is highly flammable and pyrophoric, i. That is, monosilane self-ignites in air. Escaping monosilane cannot be extinguished. The combustion produces silicon dioxide and water vapor.

${\displaystyle \mathrm {SiH_{4}+2\,O_{2}\rightarrow SiO_{2}+2\,H_{2}O\ \quad \Delta H\ll 0} }$

In water at a pH value above 7, silanes decompose to silica and hydrogen:

${\displaystyle \mathrm {SiH_{4}+4\,H_{2}O\ _{\overrightarrow {\mathrm {pH\ >\ 7} }}\ Si(OH)_{4}+4\,H_{2}} }$

Monosilane and water form silica and hydrogen.

When air and moisture are excluded, monosilane is stable up to approx. 300 ° C. Above this, silicon and hydrogen decompose.

${\displaystyle \mathrm {SiH_{4}\rightarrow Si+2\,H_{2}\ } }$

The hydrogen atoms can be successively replaced by exposure to halogens or hydrogen halides in the presence of aluminum chloride .

${\displaystyle \mathrm {SiH_{4}+\ HCl\ {\xrightarrow {>100\,{}^{\circ }C}}\ ClSiH_{3}+\,H_{2}} }$

When reacting monosilane with alkali metals z. B. in ethylene glycol dimethyl ether form the silyl compounds of the corresponding metals:

${\displaystyle \mathrm {SiH_{4}+\ K\ {\xrightarrow {}}\ KSiH_{3}+\,0.5\ H_{2}} }$

${\displaystyle \mathrm {SiH_{4}+\ 2\ K\ {\xrightarrow {}}\ KSiH_{3}+\,KH} }$

The UN number of monosilane is 2203, the label 2.1.

use

Monosilane is used to deposit silicon, silicon oxide and silicon nitride layers. Therefore, monosilane is mainly used in semiconductor manufacturing or in the manufacture of solar cells.

Individual evidence

1. ↑ ^{a b} entry on silanes. In: Römpp Online . Georg Thieme Verlag, accessed on July 14, 2014.
2. ↑ ^{a b c d e f} Entry on monosilane in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
3. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 7803-62-5 or monosilane ), accessed on November 2, 2015.
4. ↑ Wolfgang Legrum: Fragrances, between stink and fragrance , Vieweg + Teubner Verlag (2011) pp. 68–69, ISBN 978-3-8348-1245-2 .
5. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 91st – 100th, improved and greatly expanded edition. Walter de Gruyter, Berlin 1985, ISBN 3-11-007511-3 .
6. ^ Egon Wiberg: Textbook of Inorganic Chemistry: With an appendix: History of chemistry . Walter de Gruyter, 2011, ISBN 978-3-11-023832-7 , p. 319-320 ( limited preview ).
7. ↑ Barry Arkles: Silanes. (PDF) Reprint from Kirk-Othmer Encyclopedia of Chemical Technology, Forth Edition, Volume 22, Page 38-69. In: Gelest. P. 53 , accessed on December 10, 2016 (English).