Tetrasilane is a

silane Silane is an inorganic compound with chemical formula, . It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Sila ...

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

Preparation

Tetrasilane can be prepared by reacting

magnesium silicide Magnesium silicide, Mg2Si, is an inorganic compound consisting of magnesium and silicon. As-grown Mg2Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators. C ...

(Mg₂Si) with acids like 20%

phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...

in 50–60 °C. :

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The reaction can produce silanes up to n=15. The reaction of magnesium silicide with 25%

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

produces 40%

monosilane Silane is an inorganic compound with chemical formula, . It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Sila ...

, 30%

disilane Disilane is a chemical compound with chemical formula Si2H6 that was identified in 1902 by Henri Moissan and Samuel Smiles (1877–1953). Moissan and Smiles reported disilane as being among the products formed by the action of dilute acids on meta ...

, 15%

trisilane Trisilane is the silane with the formula H2Si(SiH3)2. A liquid at standard temperature and pressure, it is a silicon analogue of propane. The contrast with propane however trisilane ignites spontaneously in air. Synthesis Trisilane was characte ...

, 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: :

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Properties

Tetrasilane is a colourless,

pyrophoric A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolit ...

liquid that has a disgusting odour. Even below 54 °C, it will still spontaneous combust. It is even more unstable than

, slowly decomposing at room temperature, releasing hydrogen and forming shorter chain silanes.

Reactions

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

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With the presence of

aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...

, heating tetrasilane in

xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are s ...

will allow isomerization to isotetrasilane. :

\mathrm{2 \ H_3Si{-}SiH_2{-}SiH_2{-}SiH_3 \longrightarrow \ H_3Si{-}SiH(SiH_3)_2 }

References

Silanes