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.

Mg2Si + 4 H+ → SinH2n+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:

SiH4 → SiH2 + H2

SiH2 + SiH4 → H3Si−SiH3

SiH2 + H3Si−SiH3 → H3Si−SiH2−SiH3

SiH2 + H3Si−SiH2−SiH3 → H3Si−SiH2−SiH2−SiH3

Properties

Tetrasilane is a colourless, pyrophoric liquid that has a disgusting odour. Even below 54 °C, it will still spontaneously 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.

2 Si4H10 → Si2H6 + H3Si−SiH(Si2H6)2

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

2 H3Si−SiH2−SiH2−SiH3 → H3Si−SiH(SiH3)2

See also

  • Binary silicon-hydrogen compounds