Names | |||
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IUPAC name Tetrachlorosilane | |||
Other names Silicon tetrachloride Tetrachlorosilane | |||
Identifiers | |||
3D model (JSmol) | |||
ChemSpider | |||
ECHA InfoCard | 100.030.037 | ||
EC Number |
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PubChem CID | |||
RTECS number |
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UNII | |||
UN number | 1818 | ||
CompTox Dashboard (EPA) | |||
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Properties | |||
SiCl4 | |||
Molar mass | 169.90 g/mol | ||
Appearance | Colourless liquid | ||
Density | 1.483 g/cm3 | ||
Melting point | −68.74 °C (−91.73 °F; 204.41 K) | ||
Boiling point | 57.65 °C (135.77 °F; 330.80 K) | ||
Reacts to form silica | |||
Solubility | soluble in benzene, toluene, chloroform, ether [1] | ||
Vapor pressure | 25.9 kPa at 20 °C | ||
−88.3·10−6 cm3/mol | |||
Structure | |||
Tetrahedral | |||
4 | |||
Thermochemistry | |||
Std molar entropy (S⦵298) | 240 J·mol−1·K−1 [2] | ||
Std enthalpy of formation (ΔfH⦵298) | −687 kJ·mol−1 [2] | ||
Hazards | |||
GHS labelling: | |||
Warning | |||
H315, H319, H335 | |||
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501 | |||
NFPA 704 (fire diamond) | |||
Safety data sheet (SDS) | MSDS | ||
Related compounds | |||
Other anions | Silicon tetrafluoride Silicon tetrabromide Silicon tetraiodide | ||
Other cations | Carbon tetrachloride Germanium tetrachloride Tin(IV) chloride Titanium tetrachloride | ||
Related chlorosilanes | Chlorosilane Dichlorosilane Trichlorosilane | ||
Supplementary data page | |||
Silicon tetrachloride (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Silicon tetrachloride or tetrachlorosilane is the inorganic compound with the formula SiCl4. It is a colorless volatile liquid that fumes in air. It is used to produce high purity silicon and silica for commercial applications. It is a part of the chlorosilane family.
Silicon tetrachloride is prepared by the chlorination of various silicon compounds such as ferrosilicon, silicon carbide, or mixtures of silicon dioxide and carbon. The ferrosilicon route is most common. [3]
In the laboratory, SiCl4 can be prepared by treating silicon with chlorine at 600 °C (1,112 °F): [1]
It was first prepared by Jöns Jakob Berzelius in 1823. [4]
Brine can be contaminated with silica when the production of chlorine is a byproduct of a metal refining process from metal chloride ore. In rare occurrences, the silicon dioxide in silica is converted to silicon tetrachloride when the contaminated brine is electrolyzed. [5]
Like other chlorosilanes or silanes, silicon tetrachloride reacts readily with water:
In contrast, carbon tetrachloride does not hydrolyze readily. The reaction can be noticed on exposure of the liquid to air, the vapour produces fumes as it reacts with moisture to give a cloud-like aerosol of hydrochloric acid. [6]
With alcohols it reacts to give orthosilicate esters:
At higher temperatures homologues of silicon tetrachloride can be prepared by the reaction:
In fact, the chlorination of silicon is accompanied by the formation of hexachlorodisilane Si2Cl6. A series of compounds containing up to six silicon atoms in the chain can be separated from the mixture using fractional distillation. [1]
Silicon tetrachloride is a classic electrophile in its reactivity. [7] It forms a variety of organosilicon compounds upon treatment with Grignard reagents and organolithium compounds:
Reduction with hydride reagents afford silane.
SiH4 | SiF4 | SiCl4 | SiBr4 | SiI4 | |
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b.p. (˚C) [8] | -111.9 | -90.3 | 56.8 | 155.0 | 290.0 |
m.p. (˚C) [8] | -185 | -95.0 | -68.8 | 5.0 | 155.0 |
Si-X bond length (Å) | >0.74 [9] | 1.55 | 2.02 | 2.20 | 2.43 |
Si-X bond energy (kJ/mol) [10] | 384 | 582 | 391 | 310 | 234 |
Silicon tetrachloride is used as an intermediate in the manufacture of polysilicon, a hyper-pure form of silicon, [3] since it has a boiling point convenient for purification by repeated fractional distillation. It is reduced to trichlorosilane (HSiCl3) by hydrogen gas in a hydrogenation reactor, and either directly used in the Siemens process or further reduced to silane (SiH4) and injected into a fluidized bed reactor. Silicon tetrachloride reappears in both these two processes as a by-product and is recycled in the hydrogenation reactor. Vapor phase epitaxy of reducing silicon tetrachloride with hydrogen at approximately 1250 °C was done:
The produced polysilicon is used as wafers in large amounts by the photovoltaic industry for conventional solar cells made of crystalline silicon and also by the semiconductor industry.
Silicon tetrachloride can also be hydrolysed to fumed silica. High purity silicon tetrachloride is used in the manufacture of optical fibres. This grade should be free of hydrogen containing impurities like trichlorosilane. Optical fibres are made using processes like MCVD and OFD where silicon tetrachloride is oxidized to pure silica in the presence of oxygen.
As a feedstock in production of fused silica.
Pollution from the production of silicon tetrachloride has been reported in China associated with the increased demand for photovoltaic cells that has been stimulated by subsidy programs. [12] The MSDS notes that one should "avoid all contact! In all cases consult a doctor! ... inhalation causes sore throat and Burning sensation". [13]
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it. It is relatively unreactive.
Silane (Silicane) is an inorganic compound with chemical formula SiH4. It is a colourless, pyrophoric, toxic gas with a sharp, repulsive, pungent smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Silane with alkyl groups are effective water repellents for mineral surfaces such as concrete and masonry. Silanes with both organic and inorganic attachments are used as coupling agents. Silanes are commonly used to apply coatings to surfaces or as an adhesion promoter.
Trichlorosilane is an inorganic compound with the formula HCl3Si. It is a colourless, volatile liquid. Purified trichlorosilane is the principal precursor to ultrapure silicon in the semiconductor industry. In water, it rapidly decomposes to produce a siloxane polymer while giving off hydrochloric acid. Because of its reactivity and wide availability, it is frequently used in the synthesis of silicon-containing organic compounds.
Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as “tickle” or “tickle 4”, as a phonetic representation of the symbols of its molecular formula.
In inorganic chemistry, chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The parent chlorosilane is silicon tetrachloride.
Hafnium(IV) chloride is the inorganic compound with the formula HfCl4. This colourless solid is the precursor to most hafnium organometallic compounds. It has a variety of highly specialized applications, mainly in materials science and as a catalyst.
Tellurium tetrachloride is the inorganic compound with the empirical formula TeCl4. The compound is volatile, subliming at 200 °C at 0.1 mmHg. Molten TeCl4 is ionic, dissociating into TeCl3+ and Te2Cl102−.
Silicon tetrafluoride or tetrafluorosilane is a chemical compound with the formula SiF4. This colorless gas is notable for having a narrow liquid range: its boiling point is only 4 °C above its melting point. It was first prepared in 1771 by Carl Wilhelm Scheele by dissolving silica in hydrofluoric acid., later synthesized by John Davy in 1812. It is a tetrahedral molecule and is corrosive.
Silanes are saturated chemical compounds with the empirical formula SixHy. They are hydrosilanes, a class of compounds that includes compounds with Si−H and other Si−X bonds. All contain tetrahedral silicon and terminal hydrides. They only have Si−H and Si−Si single bonds. The bond lengths are 146.0 pm for a Si−H bond and 233 pm for a Si−Si bond. The structures of the silanes are analogues of the alkanes, starting with silane, SiH4, the analogue of methane, continuing with disilane Si2H6, the analogue of ethane, etc. They are mainly of theoretical or academic interest.
Titanium disilicide (TiSi2) is an inorganic chemical compound of titanium and silicon.
Hydrosilanes are tetravalent silicon compounds containing one or more Si-H bond. The parent hydrosilane is silane (SiH4). Commonly, hydrosilane refers to organosilicon derivatives. Examples include phenylsilane (PhSiH3) and triethoxysilane ((C2H5O)3SiH). Polymers and oligomers terminated with hydrosilanes are resins that are used to make useful materials like caulks.
Dichlorosilane, or DCS as it is commonly known, is a chemical compound with the formula H2SiCl2. In its major use, it is mixed with ammonia (NH3) in LPCVD chambers to grow silicon nitride in semiconductor processing. A higher concentration of DCS·NH3 (i.e. 16:1), usually results in lower stress nitride films.
Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si(CH3)2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made on an industrial scale as the principal precursor to dimethylsilicone and polysilane compounds.
Silicon tetrabromide, also known as tetrabromosilane, 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.
Selenium tetrachloride is the inorganic compound composed with the formula SeCl4. This compound exists as yellow to white volatile solid. It is one of two commonly available selenium chlorides, the other example being selenium monochloride, Se2Cl2. SeCl4 is used in the synthesis of other selenium compounds.
Polysilicon hydrides are polymers containing only silicon and hydrogen. They have the formula where 0.2 ≤ n ≤ 2.5 and x is the number of monomer units. The polysilicon hydrides are generally colorless or pale-yellow/ocher powders that are easily hydrolyzed and ignite readily in air. The surfaces of silicon prepared by MOCVD using silane (SiH4) consist of a polysilicon hydride.
Hexachlorodisilane is the inorganic compound with the chemical formula Si2Cl6. 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.
Chlorotrifluorosilane is an inorganic gaseous compound with formula SiClF3 composed of silicon, fluorine and chlorine. It is a silane that substitutes hydrogen with fluorine and chlorine atoms.
Khimprom Novocheboksarsk is a chemicals-producing company based in Novocheboksarsk, Russia. It is part of Orgsintez Group (Renova).
In organosilicon chemistry, silanes are a diverse class of charge-neutral organic compounds with the general formula SiR4. The R substituents can any combination of organic or inorganic groups. Most silanes contain Si-C bonds, and are discussed under organosilicon compounds. Some contain Si-H bonds and are discussed under hydrosilanes.