Silicon tetrabromide
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| Names | |||
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IUPAC name
Silicon tetrabromide
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| Other names
Silicon bromide
Silicon(IV) bromide |
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| Identifiers | |||
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3D model (Jmol)
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| ChemSpider | |||
| ECHA InfoCard | 100.029.257 | ||
| EC Number | 232-182-4 | ||
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PubChem CID
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| UN number | 3264 | ||
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| Properties | |||
| Br4Si | |||
| Molar mass | 347.70 g·mol−1 | ||
| Appearance | Colorless liquid | ||
| Density | 2.79 g·cm−3 | ||
| Melting point | 5 °C (41 °F; 278 K) | ||
| Boiling point | 153 °C (307 °F; 426 K) | ||
| −-128.6·10−6 cm3/mol | |||
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Refractive index (nD)
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1.5685 | ||
| Hazards | |||
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EU classification (DSD) (outdated)
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 C |
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| R-phrases (outdated) | R34 | ||
| S-phrases (outdated) | S26, S27, S28, S36/37/39 | ||
| NFPA 704 | |||
| Related compounds | |||
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Related tetrahalosilanes
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Silicon tetrachloride Silicon tetrafluoride Silicon tetraiodide |
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Related compounds
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Platinum(IV) bromide Tellurium tetrabromide Tetrabromomethane Tin(IV) bromide Titanium tetrabromide Zirconium(IV) bromide |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |||
Silicon tetrabromide is the inorganic compound with the formula SiBr4. This colorless liquid has a suffocating odor due to its tendency to hydrolyze with release of hydrogen bromide. The general properties of silicon tetrabromide closely resemble those of the more commonly used silicon tetrachloride.
The properties of the tetrahalosilanes, all of which are tetrahedral, are significantly affected by nature of the halide. These trends apply also to the mixed halides. Melting points, boiling points, and bond lengths increase with the atomic mass of the halide. The opposite trend is observed for the Si-X bond energies.
Covalently saturated silicon complexes like SiBr4, along with tetrahalides of germanium (Ge) and tin (Sn), are Lewis acids. Although silicon tetrahalides obey the octet rule, they add Lewis basic ligands to give adducts with the formula SiBr4L and SiBr4L2 (where L is a Lewis base). The Lewis acidic properties of the tetrahalides tend to increase as follows: SiI4 < SiBr4 < SiCl4 < SiF4. This trend is attributed to the relative electronegativities of the halogens.
The strength of the Si-X bonds decrease in the order: Si-F > Si-Cl > Si-Br > Si-I.
Silicon tetrabromide is synthesized by the reaction of silicon with hydrogen bromide at 600 °C.
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Wikipedia