Silicon tetrabromide

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Silicon tetrabromide
Stereo structural formula of silicon tetrabromide Silicon-tetrabromide-2D-A.png
Stereo structural formula of silicon tetrabromide
Space fill model of silicon tetrabromide Silicon-tetrabromide-3D-vdW.png
Space fill model of silicon tetrabromide
Silicon-tetrabromide-3D-balls.png
Names
IUPAC name
Silicon tetrabromide
Other names
Silicon bromide
Silicon(IV) bromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.257 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 232-182-4
PubChem CID
UNII
UN number 3264
  • InChI=1S/Br4Si/c1-5(2,3)4 Yes check.svgY
    Key: AIFMYMZGQVTROK-UHFFFAOYSA-N Yes check.svgY
  • Br[Si](Br)(Br)Br
Properties
Br4Si
Molar mass 347.701 g·mol−1
AppearanceColorless 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
1.5685
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg
Danger
H302, H312, H314, H332, H335
P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P322, P330, P363, 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
Related compounds
Related tetrahalosilanes
 Silicon tetrachloride
Silicon tetrafluoride
Silicon tetraiodide
Related compounds
 Platinum(IV) bromide
Tellurium tetrabromide
Tetrabromomethane
Tin(IV) bromide
Titanium tetrabromide
Zirconium(IV) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Silicon tetrabromide, also known as tetrabromosilane, is the inorganic compound with the formula SiBr4. [1] This colorless liquid has a suffocating odor due to its tendency to hydrolyze with release of hydrogen bromide. [2] The general properties of silicon tetrabromide closely resemble those of the more commonly used silicon tetrachloride. [2]

Contents

Comparison of SiX4

The properties of the tetrasilanes, 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.

SiH4SiF4SiCl4SiBr4SiI4
b.p. (˚C) [3] -111.9-90.356.8155.0290.0
m.p. (˚C) [3] -185-95.0-68.85.0155.0
Si-X bond length (Å)1.552.022.202.43
Si-X bond energy (kJ/mol) [4] 384582391310234

Lewis acidity

Covalently saturated silicon complexes like SiBr4, along with tetrahalides of germanium (Ge) and tin (Sn), are Lewis acids. [5] 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). [6] [7] [8] 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. [7] [4]

The strength of the Si-X bonds decrease in the order: Si-F > Si-Cl > Si-Br > Si-I. [4] [3]

Synthesis

Silicon tetrabromide is synthesized by the reaction of silicon with hydrogen bromide at 600 °C. [9]

Si + 4 HBr → SiBr4 + 2 H2

Side products include dibromosilane (SiH2Br2) and tribromosilane (SiHBr3). [9]

Si + 2 HBr → SiH2Br2
Si + 3 HBr → SiHBr3 + H2

It can also be produced by treating silicon-copper mixture with bromine: [10]

Si + Br2 → SiBr4

Reactivity

Like other halosilanes, SiBr4 can be converted to hydrides, alkoxides, amides, and alkyls, i.e., products with the following functional groups: Si-H, Si-OR, Si-NR2, Si-R, and Si-X bonds respectively. [2]

Silicon tetrabromide can be readily reduced by hydrides or complex hydrides. [3]

4 R2AlH + SiBr4 → SiH4 + 4 R2AlBr

Reactions with alcohols and amines proceed as follows: [3]

SiBr4 + 4 ROH → Si(OR)4 + 4 HBr
SiBr4 + 8 HNR2 → Si(NR2)4 + 4 HNR2HBr

Grignard reactions with metal alkyl halides are particularly important reactions due to their production of organosilicon compounds which can be converted to silicones. [3]

SiBr4 + n RMgX → RnSiBr4−n + n MgXBr

Redistribution reactions occur between two different silicon tetrahalides (as well as halogenated polysilanes) when heated to 100 ˚C, resulting in various mixed halosilanes. [2] [4] The melting points and boiling points of these mixed halosilanes generally increase as their molecular weights increase. [11] (Can occur with X= H, F, Cl, Br, and I)

2 SiBr4 + 2 SiCl4 → SiBr3Cl + 2 SiBr2Cl2 + SiBrCl3
Si2Cl6 + Si2Br6 → Si2ClnBr6−n

Silicon tetrabromide hydrolyzes readily when exposed to air causing it to fume: [12]

SiBr4 + 2 H2O → SiO2 + 4 HBr

Silicon tetrabromide is stable in the presence of oxygen at room temperature, but bromosiloxanes form at 670–695 ˚C . [12]

2 SiBr4 + 1⁄2 O2 → Br3SiOSiBr3 + Br2

Uses

Due to its close similarity to silicon tetrachloride, there are few applications unique to SiBr4. The pyrolysis of SiBr4 does have the advantage of depositing silicon at faster rates than that of SiCl4, however SiCl4 is usually preferred due to its availability in high purity. [13] Pyrolysis of SiBr4 followed by treatment with ammonia yields silicon nitride (Si3N4) coatings, a hard compound used for ceramics, sealants, and the production of many cutting tools. [13]

Related Research Articles

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

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.

<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.

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

Hydrogen bromide is the inorganic compound with the formula HBr. It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temperature. Aqueous solutions that are 47.6% HBr by mass form a constant-boiling azeotrope mixture that boils at 124.3 °C. Boiling less concentrated solutions releases H2O until the constant-boiling mixture composition is reached.

Tin(IV) chloride, also known as tin tetrachloride or stannic chloride, is an inorganic compound with the formula SnCl4. It is a colorless hygroscopic liquid, which fumes on contact with air. It is used as a precursor to other tin compounds. It was first discovered by Andreas Libavius (1550–1616) and was known as spiritus fumans libavii.

<span class="mw-page-title-main">Organotin chemistry</span> Branch of organic chemistry

Organotin chemistry is the scientific study of the synthesis and properties of organotin compounds or stannanes, which are organometallic compounds containing tin carbon bonds. The first organotin compound was diethyltin diiodide, discovered by Edward Frankland in 1849. The area grew rapidly in the 1900s, especially after the discovery of the Grignard reagents, which are useful for producing Sn–C bonds. The area remains rich with many applications in industry and continuing activity in the research laboratory.

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

Aluminium bromide is any chemical compound with the empirical formula AlBrx. Aluminium tribromide is the most common form of aluminium bromide. It is a colorless, sublimable hygroscopic solid; hence old samples tend to be hydrated, mostly as aluminium tribromide hexahydrate (AlBr3·6H2O).

<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.

Vanadium tetrachloride is the inorganic compound with the formula VCl4. This reddish-brown liquid serves as a useful reagent for the preparation of other vanadium compounds.

<span class="mw-page-title-main">Molybdenum(V) chloride</span> Chemical compound

Molybdenum(V) chloride is the inorganic compound with the empirical formula MoCl5. This dark volatile solid is used in research to prepare other molybdenum compounds. It is moisture-sensitive and soluble in chlorinated solvents.

Zirconium(IV) bromide is the inorganic compound with the formula ZrBr4. This colourless solid is the principal precursor to other Zr–Br compounds.

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

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.

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

Titanium tetrabromide is the chemical compound with the formula TiBr4. It is the most volatile transition metal bromide. The properties of TiBr4 are an average of TiCl4 and TiI4. Some key properties of these four-coordinated Ti(IV) species are their high Lewis acidity and their high solubility in nonpolar organic solvents. TiBr4 is diamagnetic, reflecting the d0 configuration of the metal centre.

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

Tellurium tetrabromide (TeBr4) is an inorganic chemical compound. It has a similar tetrameric structure to TeCl4. It can be made by reacting bromine and tellurium. In the vapour TeBr4 dissociates:

Tin(II) bromide is a chemical compound of tin and bromine with a chemical formula of SnBr2. Tin is in the +2 oxidation state. The stability of tin compounds in this oxidation state is attributed to the inert pair effect.

Bromine compounds are compounds containing the element bromine (Br). These compounds usually form the -1, +1, +3 and +5 oxidation states. Bromine is intermediate in reactivity between chlorine and iodine, and is one of the most reactive elements. Bond energies to bromine tend to be lower than those to chlorine but higher than those to iodine, and bromine is a weaker oxidising agent than chlorine but a stronger one than iodine. This can be seen from the standard electrode potentials of the X2/X− couples (F, +2.866 V; Cl, +1.395 V; Br, +1.087 V; I, +0.615 V; At, approximately +0.3 V). Bromination often leads to higher oxidation states than iodination but lower or equal oxidation states to chlorination. Bromine tends to react with compounds including M–M, M–H, or M–C bonds to form M–Br bonds.

In chemistry, redistribution usually refers to the exchange of anionic ligands bonded to metal and metalloid centers. The conversion does not involve redox, in contrast to disproportionation reactions. Some useful redistribution reactions are conducted at higher temperatures; upon cooling the mixture, the product mixture is kinetically frozen and the individual products can be separated. In cases where redistribution is rapid at mild temperatures, the reaction is less useful synthetically but still important mechanistically.

Polysilicon halides are silicon-backbone polymeric solids. At room temperature, the polysilicon fluorides are colorless to yellow solids while the chlorides, bromides, and iodides are, respectively, yellow, amber, and red-orange. Polysilicon dihalides (perhalo-polysilenes) have the general formula (SiX2)n while the polysilicon monohalides (perhalo-polysilynes) have the formula (SiX)n, where X is F, Cl, Br, or I and n is the number of monomer units in the polymer.

Molybdenum(IV) bromide, also known as molybdenum tetrabromide, is the inorganic compound with the formula MoBr4. It is a black solid. MoBr4 has been prepared by treatment of molybdenum(V) chloride with hydrogen bromide:

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

Germanium tetrabromide is the inorganic compound with the formula GeBr4. It is a colorless solid that melts near room temperature. It can be formed by treating solid germanium with bromine.It can also be produced by treating silicon-copper mixture with bromine:

Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known.

References

  1. ↑ PubChem. "Tetrabromosilane". pubchem.ncbi.nlm.nih.gov. Retrieved 2022-12-22.
  2. 1 2 3 4 Encyclopedia of Inorganic Chemistry; King, B. R.; John Wiley & Sons Ltd.: New York, NY, 1994; Vol 7, pp 3779–3782.
  3. 1 2 3 4 5 6 Silicon Compounds, Silicon Halides. Collins, W.: Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc, 2001.
  4. 1 2 3 4 Ebsworth, E. A. V. In Volatile Silicon Compounds; Taube, H.; Maddock, A. G.; Inorganic Chemistry; Pergamon Press Book: New York, NY, 1963; Vol. 4.
  5. ↑ Davydova, E. I.; Timoshkin, A. Y.; Sevastianova, T. N.; Suvorov, A. V.; Frenking, G. J. Mol. Struct.2006, vol, 767-1-3. doi : 10.1016/j.theochem.2006.05.011
  6. ↑ Beattie, I. R.; Gilson, T.; Webster, M.; (in part) McQuillan, G. P. J. Chem. Soc.1964, 238-244. doi : 10.1039/JR9640000238
  7. 1 2 Mironov, S. L.; Gorlov, Y. I.; Chuiko, A. A. Theor. Exp. Chem.1979, vol, 14–16. doi : 10.1007/BF00519073
  8. ↑ Beattie, I. R.; Ozin, G. A. J. Chem. Soc., Inorg. Phys. Theor.1969, 2267–2269
  9. 1 2 Schumb, W. B. Silicobromoform" Inorganic Syntheses 1939, volume 1, pp 38-42. doi : 10.1002/9780470132326.
  10. ↑ P. W. Schenk (1963). "Silicon and Germanium". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2page=687. NY,NY: Academic Press.
  11. ↑ Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements; Pergamon Press Inc.: New York, NY, 1984; pp 391-393.
  12. 1 2 Silicon Compounds, Silanes. Arkles, B.; Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc, 2001.
  13. 1 2 Silicon Compounds, Inorganic. Simmler W.; Ullmann's Encyclopedia of Industrial Chemistry; Wiley-VCH, 2002. doi : 10.1002/14356007.a24_001
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