Gallium halides

Last updated

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.

Contents

Trihalides

All four trihalides are known. They all contain gallium in the +3 oxidation state. Their proper names are gallium(III) fluoride, gallium(III) chloride, gallium(III) bromide and gallium(III) iodide.

GaF3
GaF3 is a white solid which sublimes before it melts, with an estimated melting point above 1000 °C. It contains 6 co-ordinate gallium atoms with a three-dimensional network of GaF6 octahedra sharing common corners.
GaCl3, GaBr3 and GaI3
These all have lower melting points than GaF3, (GaCl3 mp 78 °C, GaBr3 mp 122 °C, GaI3 mp 212 °C) reflecting the fact that their structures all contain dimers with 4 coordinate gallium atoms and 2 bridging halogen atoms. Thus, this halides have molecular formula Ga2Cl6, Ga2Br6, Ga2I6, respectively. They are all Lewis acids, forming mainly 4 co-ordinate adducts. GaCl3 is the most commonly used trihalide.

Intermediate halides

Intermediate chlorides, bromides and iodides exist. They contain gallium in oxidation states +1, +2 and +3.

Ga3Cl7
This compound contains the Ga2Cl7− ion, which has a structure similar to the dichromate, Cr2O72−, ion with two tetrahedrally coordinated gallium atoms sharing a corner. The compound can be formulated as gallium(I) heptachlorodigallate(III), GaI GaIII2Cl7. [1]
Ga3Cl7-unit-cell-3D-balls.png Ga3Cl7-xtal-3D-balls.png Heptachlorodigallate-anion-from-Ga3Cl7-xtal-3D-balls.png
unit cell of Ga3Cl7part of the crystal structure structure of [Ga2Cl7]−
GaCl2, GaBr2 and GaI2
These are the best known and most studied intermediate halides. They contain gallium in oxidation states +1 and +3 and are formulated GaIGaIIIX4. The dihalides are unstable in the presence of water disproportionating to gallium metal and gallium(III) entities. They are soluble in aromatic solvents, where arene complexes have been isolated and the arene is η6 coordinated to the Ga+ ion. With some ligands, L, e.g. dioxane, a neutral complex, Ga2X2L2, with a gallium-gallium bond is produced. These compounds have been used as a route into gallium chain and cluster compounds. [2]
Ga2Br3 and Ga2I3
These are formulated GaI2 GaII2Br6 and GaI2 GaII2I6 respectively. Both anions contain a gallium-gallium bond where gallium has a formal oxidation state of +2. The Ga2Br62− anion is eclipsed like the In2Br62− anion in In2Br3 whereas the Ga2I62− anion is isostructural with Si2Cl6 with a staggered conformation.

Monohalides

None of the monohalides are stable at room temperature. The previously reported GaBr and GaI produced from fusing gallium with the trihalide have been shown to be mixtures of metallic gallium with, respectively, Ga2Br3 and Ga2I3.

GaCl and GaBr
GaCl and GaBr have been produced in the gas form from the reaction of HX and molten gallium using a special reactor. They have been isolated by quenching the high temperature gas at 77 K. GaCl is reported as a red solid that disproportionates above 0 °C. Both GaCl and GaBr produced in this way can be stabilised in suitable solvents. The metastable solutions formed in this way have been used as precursors to numerous gallium cluster compounds.
In the HVPE production of GaN, GaCl is produced by passing HCl gas over molten gallium which is then reacted with NH3 gas. [3]
GaI
GaI is produced as a reactive green powder, which has been hailed as a "versatile reagent for the synthetic chemist". [4] The chemical structure of the reagent termed Solid "GaI" Precursor[ citation needed ] produced from reacting gallium metal with iodine in toluene using ultrasound has only recently been investigated using 69/71Ga solid-state NMR and a tentative structure assigned which includes gallium metal atoms, [Ga0]2[Ga]+[GaI4]−. [5]

Anionic halide complexes

Salts containing GaCl4−, GaBr4− and GaI4− are all known. Gallium is very different from indium in that it is only known to form 6 coordinate complexes with the fluoride ion. This can be rationalised by the smaller size of gallium (ionic radii of Ga(III) 62 pm, In(III) 80 pm).

Salts containing the Ga2Cl62− anion, where gallium has an oxidation state of +2, are known.

General references

  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN   0-471-19957-5

Footnotes

  1. ↑ Die Kristallstruktur von Ga3Cl7 Frank W., Hönle W., Simon A., Z. Naturforsch. Teil B (1990) 45B 1
  2. ↑ G.Garton; H.M.Powell (1956). "The crystal structure of gallium dichloride". Journal of Inorganic and Nuclear Chemistry. 4 (2): 84–89. doi:10.1016/0022-1902(57)80088-8.
  3. ↑ T.F. Kuech; Shulin Gu; Ramchandra Wate; Ling Zhang; Jingxi Sun; J.A. Dumesic; J.M. Redwing (2000). "The Chemistry of GaN Growth". MRS Online Proceedings Library. 639. Cambridge University Press. doi:10.1557/PROC-639-G1.1.
  4. ↑ Baker R.J., Jones C. Dalton Trans. 2005 Apr 21;(8):1341-8
  5. ↑ Widdifield, Cory M.; Jurca, Titel; Richeson, Darrin S.; Bryce, David L. (2012). "Using 69/71Ga solid-state NMR and 127I NQR as probes to elucidate the composition of "GaI"". Polyhedron. 35 (1): 96–100. doi:10.1016/j.poly.2012.01.003. ISSN   0277-5387.

Related Research Articles

In chemistry, an interhalogen compound is a molecule which contains two or more different halogen atoms and no atoms of elements from any other group.

<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.

In chemistry, there are three series of binary phosphorus halides, containing phosphorus in the oxidation states +5, +3 and +2. All compounds have been described, in varying degrees of detail, although serious doubts have been cast on the existence of PI5. Mixed chalcogen halides also exist.

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

Gallium(III) bromide (GaBr3) is a chemical compound, and one of four gallium trihalides.

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

Gold compounds are compounds by the element gold (Au). Although gold is the most noble of the noble metals, it still forms many diverse compounds. The oxidation state of gold in its compounds ranges from −1 to +5, but Au(I) and Au(III) dominate its chemistry. Au(I), referred to as the aurous ion, is the most common oxidation state with soft ligands such as thioethers, thiolates, and organophosphines. Au(I) compounds are typically linear. A good example is Au(CN)−2, which is the soluble form of gold encountered in mining. The binary gold halides, such as AuCl, form zigzag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives.

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">Gallium(III) chloride</span> Chemical compound

Gallium(III) chloride is an inorganic chemical compound with the formula GaCl3 which forms a monohydrate, GaCl3·H2O. Solid gallium(III) chloride is a deliquescent white solid and 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.

Organoantimony chemistry is the chemistry of compounds containing a carbon to antimony (Sb) chemical bond. Relevant oxidation states are SbV and SbIII. The toxicity of antimony limits practical application in organic chemistry.

Polyhalogen ions are a group of polyatomic cations and anions containing halogens only. The ions can be classified into two classes, isopolyhalogen ions which contain one type of halogen only, and heteropolyhalogen ions with more than one type of halogen.

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.

Gallium monoiodide is an inorganic gallium compound with the formula GaI or Ga4I4. It is a pale green solid and mixed valent gallium compound, which can contain gallium in the 0, +1, +2, and +3 oxidation states. It is used as a pathway for many gallium-based products. Unlike the gallium(I) halides first crystallographically characterized, gallium monoiodide has a more facile synthesis allowing a synthetic route to many low-valent gallium compounds.

<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(III) 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.

Einsteinium compounds are compounds that contain the element einsteinium (Es). These compounds largely have einsteinium in the +3 oxidation state, or in some cases in the +2 and +4 oxidation states. Although einsteinium is relatively stable, with half-lives ranging from 20 days upwards, these compounds have not been studied in great detail.

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

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

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

Zirconium(III) iodide is an inorganic compound with the formula ZrI3.

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).

Ytterbium compounds are chemical compounds that contain the element ytterbium (Yb). The chemical behavior of ytterbium is similar to that of the rest of the lanthanides. Most ytterbium compounds are found in the +3 oxidation state, and its salts in this oxidation state are nearly colorless. Like europium, samarium, and thulium, the trihalides of ytterbium can be reduced to the dihalides by hydrogen, zinc dust, or by the addition of metallic ytterbium. The +2 oxidation state occurs only in solid compounds and reacts in some ways similarly to the alkaline earth metal compounds; for example, ytterbium(II) oxide (YbO) shows the same structure as calcium oxide (CaO).

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.