Hexachlorodisilane is the inorganic compound with the chemical formula Si2Cl6.Simmler, W. "Silicon Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH. It is a colourless liquid that fumes in moist air. It has specialty applications in as a reagent and as a volatile precursor to silicon metal.
Structure and synthesis The molecule adopts a structure like ethane, with a single Si-Si bond length of 233 pm.T.L. Cottrell, "The Strengths of Chemical Bonds," 2nd ed., Butterworths, London, 1958
Hexachlorodisilane is produced in the chlorination of silicides such as e.g. calcium silicide. Idealized syntheses are as follows: CaSi2 + 4 Cl2 → Si2Cl6 + CaCl2
A more selective synthesis is the decomposition of silicon tetrachloride to perchloropolysilanes via glow discharge, followed by rechlorination. See also Schmeisser, Martin and Voss, Peter (December 1964) "Über das Siliciumdichlorid [SiCl2]x" (in German), Zeitschrift für anorganische und allgemeine Chemie, , as cited in Molnar et al. Higher homologues (i.e., the bromide and iodide) cannot be produced this way, requiring instead dephenylation (Friedel-Crafts ipso substitution) of hexaphenyldisilane by the appropriate acyl halide with a catalytic aluminum salt.
Reactions and uses Hexachlorodisilane is stable under air or nitrogen at temperatures of at least up to 400°C for several hours, but decomposes to dodecachloroneopentasilane and silicon tetrachloride in presence of Lewis bases even at room temperature.Emeleus, H. J., and Muhammad Tufail. "Reaction of Hexachlorodisilane with Bases and Alkyl Halides." Journal of Inorganic and Nuclear Chemistry 29.8 (1967): 2081-084
4 Si2Cl6 → 3 SiCl4 + Si5Cl12
This conversion is useful in making silicon-based components of use in semiconducting devices including photovoltaic cells.
The compound is also useful reagent for the deoxygenation reactions, such as this general process involving a phosphine oxide: Si2Cl6 + OPR3 → OSi2Cl6 + PR3
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