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.[1]
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| Names | |||
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| Other names silicon tetraiodide Tetraiodosilane | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChemSpider | |||
| ECHA InfoCard | 100.033.355 | ||
| EC Number |
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PubChem CID | |||
CompTox Dashboard (EPA) | |||
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| Properties | |||
| SiI4 | |||
| Molar mass | 535.7034 g/mol | ||
| Appearance | white powder | ||
| Density | 4.198 g/cm3 | ||
| Melting point | 120.5 °C (248.9 °F; 393.6 K) | ||
| Boiling point | 287.4 °C (549.3 °F; 560.5 K) | ||
| reacts | |||
| Solubility in organic solvents | soluble | ||
| Structure | |||
| tetrahedral | |||
| Hazards | |||
| GHS labelling: | |||
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| Danger | |||
| H301, H311, H314, H317, H334, H360 | |||
| P201, P202, P260, P261, P264, P270, P272, P280, P281, P285, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P304+P341, P305+P351+P338, P308+P313, P310, P312, P321, P322, P330, P333+P313, P342+P311, P361, P363, P405, P501 | |||
| NFPA 704 (fire diamond) | |||
| Related compounds | |||
Other anions | Silicon tetrafluoride Silicon tetrachloride Silicon tetrabromide | ||
Other cations | Carbon tetraiodide Germanium tetraiodide Tin(IV) iodide | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
SiI4 is a precursor to silicon amides of the formula Si(NR2)4 (R = alkyl).[2] 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:[3]
- Si + I2 → SiI4
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 triiodosilane SiHI3 as well. These compounds are colourless liquids at room temperature.[4] 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)[5] | -111.9 | -90.3 | 56.8 | 155.0 | 290.0 |
| m.p. (˚C)[5] | -185 | -95.0 | -68.8 | 5.0 | 155.0 |
| Si-X bond length (Å) | >0.74 [6] | 1.55 | 2.02 | 2.20 | 2.43 |
| Si-X bond energy (kJ/mol)[7] | 384 | 582 | 391 | 310 | 234 |