Tetrasilane is a silane with the structure formula SiH<sub>3</sub>âÂÂ(SiH<sub>2</sub>)<sub>2</sub>âÂÂSiH<sub>3</sub>. It is the silane analog of butane.
Tetrasilane can be prepared by reacting magnesium silicide (Mg<sub>2</sub>Si) with acids like 20% phosphoric acid in 50âÂÂ60 ðC.
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:
Tetrasilane is a colourless, pyrophoric liquid that has a disgusting odour. Even below 54 ðC, it will still spontaneously combust. It is even more unstable than trisilane, slowly decomposing at room temperature, releasing hydrogen and forming shorter chain silanes.
Photochemical disproportionation of tetrasilane will produce 3-silylpentasilane and disilane.
With the presence of aluminium chloride, heating tetrasilane in xylene will allow isomerization to isotetrasilane.