Tetrasilane

Structural formula
General
Surname	Tetrasilane
other names	n -Tetrasilane
Molecular formula	Si 4 H 10
Brief description	colorless liquid which can spontaneously ignite in air
External identifiers / databases
CAS number 7783-29-1 EC number 616-515-4 ECHA InfoCard 100.132.456 PubChem 6327668 Wikidata Q16705844
properties
Molar mass	122.42 g mol −1
Physical state	liquid
density	0.792 g cm −3
Melting point	−89.9 ° C
boiling point	108.1 ° C
Vapor pressure	27 Torr (20 ° C)
solubility	Decomposes in water
safety instructions
GHS labeling of hazardous substances H and P phrases H: 250 P: ?
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Tetrasilane is a chemical compound from the group of silanes with the semi- structural formula SiH ₃ - (SiH ₂ ) ₂ –SiH ₃ . It is the silicon analog of n-butane and is constitutional isomer to iso- tetrasilane .

Presentation and reactions

Tetrasilane can be mixed with other silanes by reacting magnesium silicide (Mg ₂ Si) with aqueous acids, e.g. B. obtained with 20% phosphoric acid at 50-60 ° C.

${\displaystyle \mathrm {Mg_{2}Si+\ 4H^{+}\ \longrightarrow \ Si_{n}H_{2n+2}} }$

Silanes up to n = 15 can be isolated in the obtained raw silane , whereby the mixture contains not only the linear n -tetrasilane but also iso -tetrasilane . The reaction of magnesium silicide with 25% hydrochloric acid results in 40% monosilane , 30% disilane , 15% trisilane , 10% tetrasilane and 5% higher silanes. The mixture can be separated by fractional distillation.

In addition, higher silanes can also be obtained through the action of silent electrical discharges on monosilane:

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

${\displaystyle \mathrm {SiH_{2}\ +\ SiH_{4}\rightarrow \ H_{3}Si{-}SiH_{3}} }$

${\displaystyle \mathrm {SiH_{2}\ +\ H_{3}Si{-}SiH_{3}\rightarrow \ H_{3}Si{-}SiH_{2}{-}SiH_{3}} }$

${\displaystyle \mathrm {SiH_{2}\ +\ H_{3}Si{-}SiH_{2}{-}SiH_{3}\rightarrow \ H_{3}Si{-}SiH_{2}{-}SiH_{2}{-}SiH_{3}} }$

properties

Tetrasilane is a colorless, pyrophoric liquid with a disgusting odor, which tends to self-ignite below 54 ° C. Compared to trisilane , pure tetrasilane is less stable and slowly decomposes at room temperature in daylight, releasing hydrogen and forming the shorter homologues.

Reactions

Tetrasilane is converted into 3-silylpentasilane and disilane through photochemical disproportionation :

${\displaystyle \mathrm {2\ Si_{4}H_{10}\rightarrow \ Si_{2}H_{6}\ +H_{3}Si{-}SiH(Si_{2}H_{6})_{2}} }$

Iso- tetrasilane can be obtained by heating n- tetrasilane in xylene in the presence of aluminum chloride .

${\displaystyle \mathrm {2\ H_{3}Si{-}SiH_{2}{-}SiH_{2}{-}SiH_{3}\longrightarrow \ H_{3}Si{-}SiH(SiH_{3})_{2}} }$

Individual evidence

1. ↑ ^{a b c d e} Material Safety Data Sheet for Tetrasilane (Si ₄ H ₁₀ ) ( PDF file )
2. ↑ ^{a b c} David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . Internet version 2005th edition. (Internet version:), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Inorganic Compounds, pp. 4-81 - 4-81.
3. ↑ There is not yet a harmonized classification for this substance . A labeling of tetrasilane in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), which was accessed on December 3, 2016, is reproduced from a self-classification by the distributor .
4. ↑ ^{a b} Ralf Steudel : Chemistry of Non-Metals: Syntheses - Structures - Binding - Use . De Gruyter, 2014, ISBN 978-3-11-030797-9 , pp. 294–295 ( limited preview ).
5. ^ 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 ).
6. ↑ Alfred Stock, Paul Stiebeler, Friedrich Zeidler: Siliciumwasserstoffe, XVI .: The higher silicon hydrides . In: Reports of the German Chemical Society . tape 56 , no. 7 , July 4, 1923, p. 1695-1705 , doi : 10.1002 / cber.19230560735 .
7. ^ F. Fehér, I. Fischer: Contributions to the chemistry of silicon and germanium, XXVIII. The photochemical disproportionation of n-tetrasilane, representation and properties of 3-silylpentasilane . In: Journal of Inorganic and General Chemistry . tape 421 , no. 1 , March 1976, p. 9-14 , doi : 10.1002 / zaac.19764210103 .
8. ↑ Franz Fehér , Franz Ocklenburg and Dieter Skrodzki: contributions to the chemistry of silicon and germanium, XXXII, isomerization of higher silanes with aluminum chloride. In: Journal of Nature Research B . 35, 1980, pp. 869-872 ( PDF , free full text).