Silicon tetrabromide is a versatile starting compound, particularly for synthesising different silylenes. Although it is expensive to purchase directly, it can be easily prepared in small quantities. Traditional large-scale synthesis involves reacting elemental bromine with silicon at elevated temperatures, producing a product that is likely to be contaminated with bromine and must be distilled. An alternative synthesis for small scales (1–20 g) involves the reaction of silver bromide (AgBr) with silicon in a quartz ampoule at 650 °C over the course of several hours.
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The ampoule containing the AgBr/Si mixture must be evacuated at 300 °C for an hour before the reaction can begin in vacuo.
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There must be space outside the oven so that the SiBr₄ can condense and be collected (by bending the ampoule, using an ampoule with two chambers, or a Schlenk flask connected to the ampoule via a ground joint).
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Silver bromide can be prepared from elemental silver by dissolving it in nitric acid and precipitating AgBr with the addition of KBr or NaBr.
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Silver bromide is light sensitive.
[1] Herrman/Brauer, Synthetic Methods of Organometallic and Inorganic Chemistry, Volume 2, 1996.