Silicon tetrachloride

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Silicon tetrachloride
Silicon tetrachloride.svg
Silicon-tetrachloride-3D-vdW.png
Silicon tetrachloride.png
Names
IUPAC name
Tetrachlorosilane
Other names
Silicon tetrachloride
Tetrachlorosilane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.037 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-054-0
PubChem CID
RTECS number
  • VW0525000
UNII
UN number 1818
  • InChI=1S/Cl4Si/c1-5(2,3)4 Yes check.svgY
    Key: FDNAPBUWERUEDA-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/Cl4Si/c1-5(2,3)4
  • [Si](Cl)(Cl)(Cl)Cl
Properties
SiCl4
Molar mass 169.90 g/mol
AppearanceColourless 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
(S298)
240 J·mol−1·K−1 [2]
−687 kJ·mol−1 [2]
Hazards
GHS labelling:
GHS-pictogram-exclam.svg
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)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
3
0
2
W
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).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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.

Contents

Preparation

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]

Si + 2 Cl2 → SiCl4

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]

Reactions

Like other chlorosilanes or silanes, silicon tetrachloride reacts readily with water:

SiCl4 + 2 H2O → SiO2 + 4 HCl

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:

SiCl4 + 4 ROH → Si(OR)4 + 4 HCl

Polysilicon chlorides

At higher temperatures homologues of silicon tetrachloride can be prepared by the reaction:

Si + 2 SiCl4 → Si3Cl8

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]

Reactions with other nucleophiles

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:

4 RLi + SiCl4 → R4Si + 4 LiCl

Reduction with hydride reagents afford silane.

Comparison with other SiX4 compounds

SiH4SiF4SiCl4SiBr4SiI4
b.p. (˚C) [8] -111.9-90.356.8155.0290.0
m.p. (˚C) [8] -185-95.0-68.85.0155.0
Si-X bond length (Å)>0.74 [9] 1.552.022.202.43
Si-X bond energy (kJ/mol) [10] 384582391310234

Uses

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:

SiCl
4
(g) + 2 H
2
(g) → Si(s) + 4 HCl(g) at 1250°C [11]

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.

Safety and environmental issues

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]

See also

Related Research Articles

<span class="mw-page-title-main">Silicon</span> Chemical element, symbol Si and atomic number 14

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.

<span class="mw-page-title-main">Trichlorosilane</span> Chemical compound

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.

<span class="mw-page-title-main">Titanium tetrachloride</span> Inorganic chemical compound

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.

<span class="mw-page-title-main">Hafnium tetrachloride</span> Chemical compound

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.

<span class="mw-page-title-main">Tellurium tetrachloride</span> Chemical compound

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−.

<span class="mw-page-title-main">Silicon tetrafluoride</span> Chemical compound

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.

<span class="mw-page-title-main">Binary silicon-hydrogen compounds</span>

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.

<span class="mw-page-title-main">Dichlorosilane</span> Chemical compound

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.

<span class="mw-page-title-main">Silicon tetrabromide</span> Chemical compound

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.

<span class="mw-page-title-main">Selenium tetrachloride</span> Chemical compound

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.

<span class="mw-page-title-main">Hexachlorodisilane</span> Chemical compound

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.

References

  1. 1 2 3 P. W. Schenk (1963). "Phosphorus(V) fluoride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY,NY: Academic Press. pp. 282–683.
  2. 1 2 Zumdahl, S. S. (2009). Chemical Principles (6th ed.). Houghton Mifflin. p. A22. ISBN   978-0-618-94690-7.
  3. 1 2 Simmler, W. "Silicon Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a24_001.
  4. Berzelius, Jac. (1824). "Undersökning af flusspatssyran och dess märkvärdigaste föreningar" [Examination of hydrofluoric acid and its most significant compounds]. Kongliga Vetenskapsakademiens Nya Handlingar [New Proceedings of the Royal Academy of Sciences]. 3rd series (in Swedish). 12: 46–98. From pp. 57-58: "Då silicium upphettas i en ström ab chlor, tänder det sig och brinner, samt om gasen innehöll atm. luft, lemnar det kiseljord i form af ett ullikt skelett. […] Silicium glödgadt i en ström af iodgas, har icke kunnat fås att dermed förbinda sig." (When silicon is heated in a stream of chlorine, it ignites and burns, as well as if the gas contained atmospheric air, it leaves silica in the form of an odd "skeleton". If the silicon was previously oxidized to some extent, then the siliceous earth also remains. Silicon burns in chlorine with equal slowness, whether it has lost its flammability in air or not. The product of the combustion is condensed and forms a liquid, which, when freed from it, should be colorless. This liquid is quite volatile and easy-flowing; it evaporates in the open air, almost instantly, with the emission of a white smoke and with a residue of siliceous earth. It has a pungent smell, somewhat like cyanide; precipitated in water, it quickly floats up, dissolves for the most part, but leaves a little siliceous earth undissolved; if the quantity of water is small, e.g., a drop of each, then the chlorosilicon floats around and the silica becomes undissolved in an exfoliated, semi-transparent state. This liquid is analogous to the compound of other electronegative substances with chlorine. Reacts like acid with litmus paper, so that, by its volatility, the paper reddens quite a distance from the point of contact. It is the second known example of a compound in which silicon is volatile. At the ordinary temperature of the air, potassium does not act on it; but if it is heated in the gas of chlorosilicon, it ignites and burns, with a residue of silicon-bound potassium. Silicon heated in a stream of iodine gas, could not be made to bond with it.)
  5. White, George Clifford (1986). The handbook of chlorination (2nd ed.). New York: Van Nostrand Reinhold. pp. 33–34. ISBN   0-442-29285-6.
  6. Clugston, M.; Flemming, R. (2000). Advanced Chemistry. Oxford University Press. p. 342. ISBN   978-0199146338.
  7. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  8. 1 2 Silicon Compounds, Silicon Halides. Collins, W.: Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc, 2001.
  9. "What is the bond length of the H-H bond?". Answers.com .
  10. Ebsworth, E. A. V. In Volatile Silicon Compounds; Taube, H.; Maddock, A. G.; Inorganic Chemistry; Pergamon Press Book: New York, NY, 1963; Vol. 4.
  11. Morgan, D. V.; Board, K. (1991). An Introduction To Semiconductor Microtechnology (2nd ed.). Chichester, West Sussex, England: John Wiley & Sons. p. 23. ISBN   0471924784.
  12. "Solar Energy Firms Leave Waste Behind in China". The Washington Post. 9 March 2008.
  13. "International Chemical Safety Cards Tetrachlorosilane".