Gallium(III) bromide

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Gallium(III) bromide (dimer)
Gallium-bromide-3D-balls.png
Gallium-bromide-3D-vdW.png
Names
Other names
gallium tribromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.267 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 236-609-5
PubChem CID
  • InChI=1S/3BrH.Ga/h3*1H;/q;;;+3/p-3 Yes check.svgY
    Key: SRVXDMYFQIODQI-UHFFFAOYSA-K Yes check.svgY
  • InChI=1/3BrH.Ga/h3*1H;/q;;;+3/p-3
    Key: SRVXDMYFQIODQI-DFZHHIFOAJ
  • Br[Ga](Br)Br
Properties
GaBr3
Molar mass 309.435 g/mol
Appearancewhite powder
Density 3.69 g/cm3
Melting point 121.5 °C (250.7 °F; 394.6 K)
Boiling point 278.8 °C (533.8 °F; 552.0 K)
soluble
Hazards
GHS labelling:
GHS-pictogram-acid.svg
Danger
H314
P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
0
0
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 ?)

Gallium(III) bromide (Ga Br3) is a chemical compound, and one of four gallium trihalides.

Contents

Introduction

Gallium(III) bromide is, at room temperature and atmospheric pressure, a white, crystalline powder which reacts favorably and exothermically with water. [1] Solid gallium tribromide is stable at room temperature and can be found primarily in its dimeric form. [2] GaBr3 can form an intermediate halide, Ga2Br7; however, this is not as common as with GaCl3. It is a member of the gallium trihalide group and is similar to GaCl3, and GaI3, but not GaF3, in its preparation and uses. [2] GaBr3 is a milder Lewis acid than AlBr3, and has more versatile chemistry due to the comparative ease of reducing gallium, but is more reactive than GaCl3. [3]

GaBr3 is similar spectroscopically to aluminum, indium, and thallium trihalides excluding trifluorides. [4]

Preparation

One method of preparing GaBr3 is to heat elemental gallium in the presence of bromine liquid under vacuum. [5] Following the highly exothermic reaction, the mixture is allowed to rest and then subjected to various purifying steps. This method from the turn of the twentieth century remains a useful way of preparing GaBr3. Historically, gallium was obtained by electrolysis of its hydroxide in solution of potassium hydroxide, however today it is obtained as a byproduct of aluminium and zinc production.

GaBr3 can be synthesized by exposing gallium to bromine in an environment free of water, oxygen and grease. [5] [6] The result is a gas which must be crystallized in order to form bromide purchased by laboratories. Below is the equation:

2 Ga(s) + 3 Br2(l) → 2 GaBr3(g)

Structure

Extended crystal structure of GaBr3 Extended Crystal Structure.png
Extended crystal structure of GaBr3

The GaBr3 monomer has trigonal planar geometry, but when it forms the dimer Ga2Br6 the geometry around the gallium center distorts to become roughly tetrahedral. As a solid, GaBr3 forms a monoclinic crystalline structure with a unit cell volume of 524.16 Å3. Additional specifications for this unit cell are as follows: a = 8.87 Å, b = 5.64 Å, c =11.01 Å, α = 90˚, β = 107.81˚, γ = 90˚. [7]

Complexes

Gallium is the lightest group 13 metal with a filled d-shell, and has an electronic configuration of ([Ar] 3d10 4s2 4p1) below the valence electrons that could take part in d-π bonding with ligands. The somewhat high oxidation state of Ga in Ga(III)Br3, low electronegativity, and high polarizability allow GaBr3 to behave as a "soft acid" in terms of the Hard-Soft-Acid-Base (HSAB) theory. The Lewis acidity of all the gallium trihalides, GaBr3 included, has been extensively studied thermodynamically, and the basicity of GaBr3 has been established with a number of donors. [2]

GaBr3 is capable of accepting an additional Br ion or unevenly splitting its dimer to form [GaBr4], a tetrahedral ion of which crystalline salts can be obtained. [2] [8] This ionic complex is further capable of binding to . The Br ion can be just as easily substituted with a neutral ligand. Typically these neutral ligands, with form GaBr3 L and sometimes GaBr3L2, will form a tetrahedral bipyramidal geometric structure with the Br in an equatorial position due to their large effective nuclear charge. [2] Additionally, GaBr3 can be used as a catalyst in certain oxidative addition reactions.

Uses

GaBr3 is used as a catalyst in organic synthesis, with similar mechanism to GaCl3. However, due to its greater reactivity, it is sometimes disfavored because of the greater versatility of GaCl3. [2] GaBr3 as well as other gallium trihalides and group 13 metal trihalides can be used as catalysts in the oxidative addition of organic compounds. It has been verified that the GaBr3 dimer cleaves unevenly into [GaBr4] and [GaBr2]+. [8] The entire mechanism is uncertain partly because intermediate states are not always stable enough for study, and partially because GaBr3 is studied less frequently than GaCl3. Ga(III) itself is a useful Lewis acid for organic reactions because its full d-electron shell makes it able to accept variable numbers of ligands, but will readily give up ligands if conditions prove favorable.

See also

Related Research Articles

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

Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula AlCl3. It forms a hexahydrate with the formula [Al(H2O)6]Cl3, containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour.

<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">Gold(III) bromide</span> Chemical compound

Gold(III) bromide is a dark-red to black crystalline solid. It has the empirical formula AuBr3, but exists primarily as a dimer with the molecular formula Au2Br6 in which two gold atoms are bridged by two bromine atoms. It is commonly referred to as gold(III) bromide, gold tribromide, and rarely but traditionally auric bromide, and sometimes as digold hexabromide. As is similar with the other gold halides, this compound is unique for being a coordination complex of a group 11 transition metal that is stable in an oxidation state of +3 whereas copper or silver complexes persist in oxidation states of +1 or +2.

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

Indium(III) chloride is the chemical compound with the formula InCl3 which forms a tetrahydrate. This salt is a white, flaky solid with applications in organic synthesis as a Lewis acid. It is also the most available soluble derivative of indium. This is one of three known indium chlorides.

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.

<span class="mw-page-title-main">Indium(III) bromide</span> Chemical compound

Indium(III) bromide, (indium tribromide), InBr3, is a chemical compound of indium and bromine. It is a Lewis acid and has been used in organic synthesis.

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

Gallium trichloride is the chemical compound with the formula GaCl3. Solid gallium trichloride exists as a dimer with the formula Ga2Cl6. It is colourless and soluble in virtually all solvents, even alkanes, which is truly unusual for a metal halide. It is the main precursor to most derivatives of gallium and a reagent in organic synthesis.

The thallium halides include monohalides, where thallium has oxidation state +1, trihalides in which thallium generally has oxidation state +3, and some intermediate halides containing thallium with mixed +1 and +3 oxidation states. These salts find use in specialized optical settings, such as focusing elements in research spectrophotometers. Compared to the more common zinc selenide-based optics, materials such as thallium bromoiodide enable transmission at longer wavelengths. In the infrared, this allows for measurements as low as 350 cm−1 (28 μm), whereas zinc selenide is opaque by 21.5 μm, and ZnSe optics are generally only usable to 650 cm−1 (15 μm).

There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide and indium(I) iodide.

There are three sets of gallium halides, the trihalides where gallium has oxidation state +3, the intermediate halides containing gallium in oxidation states +1, +2 and +3 and some unstable monohalides, where gallium has oxidation state +1.

<span class="mw-page-title-main">Organogallium chemistry</span> Chemistry of Organogallium compounds

Organogallium chemistry is the chemistry of organometallic compounds containing a carbon to gallium (Ga) chemical bond. Despite their high toxicity, organogallium compounds have some use in organic synthesis. The compound trimethylgallium is of some relevance to MOCVD as a precursor to gallium arsenide via its reaction with arsine at 700 °C:

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

Bismuth tribromide is an inorganic compound of bismuth and bromine with the chemical formula BiBr3.

In chemistry, aluminium(I) refers to monovalent aluminium (+1 oxidation state) in both ionic and covalent bonds. Along with aluminium(II), it is an extremely unstable form of aluminium.

<span class="mw-page-title-main">Aluminium compounds</span>

Aluminium (British and IUPAC spellings) or aluminum (North American spelling) combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier group 13 congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances. Furthermore, as Al3+ is a small and highly charged cation, it is strongly polarizing and aluminium compounds tend towards covalency; this behaviour is similar to that of beryllium (Be2+), an example of a diagonal relationship. However, unlike all other post-transition metals, the underlying core under aluminium's valence shell is that of the preceding noble gas, whereas for gallium and indium it is that of the preceding noble gas plus a filled d-subshell, and for thallium and nihonium it is that of the preceding noble gas plus filled d- and f-subshells. Hence, aluminium does not suffer the effects of incomplete shielding of valence electrons by inner electrons from the nucleus that its heavier congeners do. Aluminium's electropositive behavior, high affinity for oxygen, and highly negative standard electrode potential are all more similar to those of scandium, yttrium, lanthanum, and actinium, which have ds2 configurations of three valence electrons outside a noble gas core: aluminium is the most electropositive metal in its group. Aluminium also bears minor similarities to the metalloid boron in the same group; AlX3 compounds are valence isoelectronic to BX3 compounds (they have the same valence electronic structure), and both behave as Lewis acids and readily form adducts. Additionally, one of the main motifs of boron chemistry is regular icosahedral structures, and aluminium forms an important part of many icosahedral quasicrystal alloys, including the Al–Zn–Mg class.

<span class="mw-page-title-main">Californium(III) bromide</span> Chemical compound

Californium(III) bromide is an inorganic compound, a salt with a chemical formula CfBr3. Like in californium oxide (Cf2O3) and other californium halides, including californium(III) fluoride (CfF3), californium(III) chloride, and californium(III) iodide (CfI3), the californium atom has an oxidation state of +3.

<span class="mw-page-title-main">Curium(III) bromide</span> Chemical compound

Curium(III) bromide is the bromide salt of curium. It has an orthorhombic crystal structure.

<span class="mw-page-title-main">Zirconium(III) bromide</span> Chemical compound

Zirconium(III) bromide is an inorganic compound with the formula ZrBr3.

Gallium compounds are compounds containing the element gallium. These compounds are found primarily in the +3 oxidation state. The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium. For example, the very stable GaCl2 contains both gallium(I) and gallium(III) and can be formulated as GaIGaIIICl4; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga24+(S2−)2) and the dioxan complex Ga2Cl4(C4H8O2)2. There are also compounds of gallium with negative oxidation states, ranging from -5 to -1, most of these compounds being magnesium gallides (MgxGay).

Arene complexes of univalent gallium, indium, and thallium are complexes featuring the centric (η6) coordination of the metal to the arene. Although arene complexes of transitional metals have long been reported, arene complexes of the main group elements remain scarce. This might be partly explained by the difference in energy of the d and p orbitals.

References

  1. "Gallium(III) bromide". Sigma Aldrich Catalogue. Sigma Aldrich Company.
  2. 1 2 3 4 5 6 King, Bruce R. (1994). Encyclopedia of Inorganic Chemistry. New York: Wiley. pp. 1265–1267. ISBN   978-0-471-93620-6.
  3. Kiyokawa, Kensuke; Yasuda, Makoto; Baba, Akio (2010-04-02). "Cyclopropylmethylation of Benzylic and Allylic Chlorides with Cyclopropylmethylstannane Catalyzed by Gallium or Indium Halide". Organic Letters. 12 (7): 1520–1523. doi:10.1021/ol100240b. ISSN   1523-7060. PMID   20218636.
  4. Downs, A.J. (199). Chemistry of Aluminium Gallium Indium and Thallium. Springer Science & Business Media. p. 133.
  5. 1 2 Johnson, W. C.; Parsons, J. B. (1929-01-01). "The Preparation of Gallium Tribromide and Gallium Triiodide". The Journal of Physical Chemistry. 34 (6): 1210–1214. doi:10.1021/j150312a007. ISSN   0092-7325.
  6. Downs, A.J. (199). Chemistry of Aluminium Gallium Indium and Thallium. Springer Science & Business Media. p. 133.
  7. Troyanov, S.I.; Krahl, T.; Kemnitz, E. (2004). "Crystal structures of GaX3 (X = Cl, Br, I) and AlI3". Zeitschrift für Kristallographie. 219 (2): 88–92. doi:10.1524/zkri.219.2.88.26320. S2CID   101603507.
  8. 1 2 El-Hellani, Ahmad; Monot, Julien; Guillot, Régis; Bour, Christophe; Gandon, Vincent (2013-01-07). "Molecular versus Ionic Structures in Adducts of GaX3 with Monodentate Carbon-Based Ligands". Inorganic Chemistry. 52 (1): 506–514. doi:10.1021/ic302440g. ISSN   0020-1669. PMID   23256783.