Chemistry:Tetrasilane

Tetrasilane

Names
IUPAC name Tetrasilane
Other names n-Tetrasilane
Identifiers
CAS Number	7783-29-1 Y
3D model (JSmol)	Interactive image
ChemSpider	122662
EC Number	616-515-4
PubChem CID	6327668
UNII	OI9DXJ0BL4
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
Density	0.792 g·cm−3
Melting point	−89.9 °C
Boiling point	108.1 °C
Solubility in water	reacts
Hazards
GHS pictograms
GHS Signal word	Danger
GHS 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.

$\mathrm{M}{\mathrm{g}}_{\mathrm{2}}\mathrm{S}\mathrm{i}\mathrm{+}\mathrm{4}{\mathrm{H}}^{\mathrm{+}}\mathrm{⟶}\mathrm{S}{\mathrm{i}}_{\mathrm{n}}{\mathrm{H}}_{\mathrm{2}\mathrm{n}\mathrm{+}\mathrm{2}}$

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. The mixture can be separated by fractional distillation.

In addition, higher silanes can also be obtained by discharges monosilane:

$\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{4}}\mathrm{\to }\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{+}{\mathrm{H}}_{\mathrm{2}}$

$\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{+}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{4}}\mathrm{\to }{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{3}}$

$\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{+}{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{3}}\mathrm{\to }{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{3}}$

$\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{+}{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{3}}\mathrm{\to }{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{3}}$

Properties

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

Reactions

Photochemical disproportionation of tetrasilane will produce 3-silylpentasilane and disilane.

$\mathrm{2}\mathrm{S}{\mathrm{i}}_{\mathrm{4}}{\mathrm{H}}_{\mathrm{1}\mathrm{0}}\mathrm{\to }\mathrm{S}{\mathrm{i}}_{\mathrm{2}}{\mathrm{H}}_{\mathrm{6}}\mathrm{+}{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}\mathrm{H}\mathrm{(}\mathrm{S}{\mathrm{i}}_{\mathrm{2}}{\mathrm{H}}_{\mathrm{6}}{\mathrm{)}}_{\mathrm{2}}$

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

$\mathrm{2}{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{2}}\mathrm{-}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{3}}\mathrm{⟶}{\mathrm{H}}_{\mathrm{3}}\mathrm{S}\mathrm{i}\mathrm{-}\mathrm{S}\mathrm{i}\mathrm{H}\mathrm{(}\mathrm{S}\mathrm{i}{\mathrm{H}}_{\mathrm{3}}{\mathrm{)}}_{\mathrm{2}}$