Tetrasilane

Names
IUPAC name Tetrasilane
Other names n-Tetrasilane
Identifiers
CAS Number	7783-29-1 Y
3D model (JSmol)	Interactive image
ChemSpider	122662
ECHA InfoCard	100.132.456
EC Number	616-515-4
PubChem CID	6327668
UNII	OI9DXJ0BL4
CompTox Dashboard (EPA)	DTXSID30999039
InChI InChI=1S/H10Si4/c1-3-4-2/h3-4H2,1-2H3 Key: MBDFFBCLMHNNID-UHFFFAOYSA-N
SMILES [SiH3][SiH2][SiH2][SiH3]
Properties
Chemical formula	H10Si4
Molar mass	122.420 g·mol−1
Appearance	colourless liquid that self ignite in air[1]
Density	0.792 g·cm−3[2]
Melting point	−89.9 °C[2]
Boiling point	108.1 °C[2]
Solubility in water	reacts[1]
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H250
Related compounds
Related compounds	butane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Tetrasilane is a silane with the structure formula SiH₃–(SiH₂)₂–SiH₃. It is the silane analog of butane.

Preparation

Tetrasilane can be prepared by reacting magnesium silicide (Mg₂Si) with acids like 20% phosphoric acid in 50–60 °C.^[3]

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

The reaction can produce silanes up to n=15. The reaction of magnesium silicide with 25% hydrochloric acid produces 40% monosilane, 30% disilane, 15% trisilane, 10% tetrasilane and 5% higher silanes.^[4] The mixture can be separated by fractional distillation.

In addition, higher silanes can also be obtained by discharges monosilane:^[3]

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

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

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

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

Properties

Tetrasilane is a colourless, pyrophoric liquid that has a disgusting odour. Even below 54 °C, it will still spontaneous combust.^[1] It is even more unstable than trisilane, slowly decomposing at room temperature, releasing hydrogen and forming shorter chain silanes.^[5]

Reactions

Photochemical disproportionation of tetrasilane will produce 3-silylpentasilane and disilane.^[6]

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

With the presence of aluminium chloride, heating tetrasilane in xylene will allow isomerization to isotetrasilane.^[7]

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

References