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.
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| Names | |||
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| Other names silicon tetraiodide Tetraiodosilane | |||
| Identifiers | |||
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| ECHA InfoCard | 100.033.355 | ||
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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: | |||
Signal word | 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) | 2 0 0 | ||
| 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). verify (what is ?) Infobox references | |||
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:
- 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. 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 | |
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| b.p. (˚C) | −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) | 384 | 582 | 391 | 310 | 234 |
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