Silicon tetraiodide is the chemical compound with the formula SiI4. It is a tetrahedral molecule with Si-I bond lengths of 2.432(5) Å.
SiI4 is a precursor to silicon amides of the formula Si(NR2)4 (R = alkyl). It has also been of interest in the manufacture and etching of silicon in microelectronics.
Synthesis and reactions This compound is produced by treating silicon-copper mixture with iodine:
It reacts quickly with water and moisture in the air.
It can also be made on a large scale by reaction of silicon or silicon carbide with iodine on heating to about 200 °C. Of more academic interest is the reaction of silane with iodine vapour at 130 - 150 °C, as this produces a series of compounds ranging from iodosilane SiH3I to diiodosilane SiH2I2 and SiHI3 as well. These compounds are colourless liquids at room temperature. The last one can be readily distinguished from the similar carbon compound, iodoform which is a yellow solid at room temperature.
Comparison with other SiX4 compounds SiH4 SiF4 SiCl4 SiBr4 SiI4 b.p. (˚C)Silicon Compounds, Silicon Halides. Collins, W.: Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc, 2001. −111.9 −90.3 56.8 155.0 290.0 m.p. (˚C) −185 −95.0 −68.8 5.0 155.0 Si-X bond length (Å) >0.74 1.55 2.02 2.20 2.43 Si-X bond energy (kJ/mol)Ebsworth, E. A. V. In Volatile Silicon Compounds; Taube, H.; Maddock, A. G.; Inorganic Chemistry; Pergamon Press Book: New York, NY, 1963; Vol. 4. 384 582 391 310 234
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