Gallium trichloride is the chemical compound with the formula GaCl3. Solid gallium trichloride is a deliquescent white solid and exists as a dimer with the formula Ga2Cl6.[2] 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.[3]
Names | |
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Other names
Gallium(III) chloride, Trichlorogallium, Trichlorogallane
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Identifiers | |
3D model (JSmol)
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ChemSpider | |
ECHA InfoCard | 100.033.268 |
PubChem CID
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RTECS number |
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
GaCl 3 | |
Molar mass | 176.073 g/mol |
Appearance | colorless crystals |
Density | 2.47 g/cm3 |
Melting point | 77.9 °C (172.2 °F; 351.0 K) (anhydrous) 44.4 °C (hydrate) |
Boiling point | 201 °C (394 °F; 474 K) |
very soluble | |
Solubility | soluble in benzene, CCl4, CS2 |
−63.0·10−6 cm3/mol | |
Structure[1] | |
monoclinic | |
C2/m | |
a = 11.95 Å, b = 6.86 Å, c = 7.05 Å α = 90°, β = 125.7°, γ = 90°
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Lattice volume (V)
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469 Å3 |
Hazards | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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4700 mg/kg (rat, oral) |
Related compounds | |
Other anions
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Gallium(III) fluoride Gallium(III) bromide Gallium(III) iodide |
Other cations
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Aluminium chloride Indium(III) chloride Thallium(III) chloride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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As a Lewis acid, GaCl3 is milder than aluminium trichloride. It is also easier to reduce than aluminium trichloride. The coordination chemistry of Ga(III) and Fe(III) are similar, so gallium(III) chloride have been used as diamagnetic analogues of ferric chloride.
Preparation edit
Gallium trichloride can be prepared from the elements, heating gallium metal in a stream of chlorine, and purifying the product by sublimation under vacuum.[4]
- 2 Ga + 3 Cl2 → 2 GaCl3
It can also be prepared from by heating gallium oxide with thionyl chloride:[5]
- Ga2O3 + 3 SOCl2 → 2 GaCl3 + 3 SO2
Gallium metal reacts slowly with hydrochloric acid. This reaction produces hydrogen gas slowly.
Structure edit
As a solid, it adopts a bitetrahedral structure with two bridging chlorides. Its structure resembles that of aluminium tribromide. In contrast AlCl3 and InCl3 feature contain 6 coordinate metal centers. As a consequence of its molecular nature and associated low lattice energy, gallium trichloride has a lower melting point vs the aluminium and indium trihalides. The formula of Ga2Cl6 is often written as Ga2(μ-Cl)2Cl4.[1] In the gas phase the dimers dissociate to trigonal planar monomers.[citation needed]
Complexes edit
Gallium is the lightest member of Group 13 to have a full d shell, (gallium has the electronic configuration [Ar] 3d10 4s2 4p1) below the valence electrons that could take part in d-π bonding with ligands. The low oxidation state of Ga in Ga(III)Cl3, along with the low electronegativity and high polarisability, allow GaCl3 to behave as a "soft acid" in terms of the HSAB theory. The strength of the bonds between gallium halides and ligands have been extensively studied. What emerges is:
- GaCl3 is a weaker Lewis acid than AlCl3 towards N and O donors e.g. pyridine
- GaCl3 is a stronger Lewis acid than AlCl3 towards thioethers e.g. dimethyl sulfide, Me2S
With a chloride ion as ligand the tetrahedral GaCl4− ion is produced, the 6 coordinate GaCl63− cannot be made. Compounds like KGa2Cl7 that have a chloride bridged anion are known.[6] In a molten mixture of KCl and GaCl3, the following equilibrium exists:
- 2 GaCl4− ⇌ Ga2Cl7− + Cl−
Uses edit
Organic synthesis edit
Gallium trichloride is a Lewis acid catalyst, such as in the Friedel–Crafts reaction, and is also used in carbogallation reactions of compounds with a carbon-carbon triple bond. It is a precursor to organogallium reagents. It is also used as a catalyst in many organic reactions.[3]
Detection of solar neutrinos edit
110 tons of gallium trichloride aqueous solution was used in the GALLEX and GNO experiments performed at Laboratori Nazionali del Gran Sasso in Italy to detect solar neutrinos. In these experiments, germanium-71 was produced by neutrino interactions with the isotope gallium-71 (which has a natural abundance of 40%), and the subsequent beta decays of germanium-71 were measured.[7]
See also edit
References edit
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- "Gallium". WebElements Periodic Table.
- ^ a b Sergey I. Troyanov; Thoralf Krahl; Erhard Kemnitz (2004). "Crystal structures of GaX3 (X = Cl, Br, I) and AlI3". Zeitschrift für Kristallographie - Crystalline Materials. 219 (2): 88–92. doi:10.1524/zkri.219.2.88.26320.
- ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
- ^ a b Yamaguchi, Masahiko; Matsunaga, Shigeki; Shibasaki, Masakatsu; Michelet, Bastien; Bour, Christophe; Gandon, Vincent (2014), "Gallium Trichloride", Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, Ltd, pp. 1–8, doi:10.1002/047084289x.rn00118u.pub3, ISBN 9780470842898
- ^ Roger A. Kovar; J. A. Dilts (1977). "Gallium Trichloride". Inorganic Syntheses Volume 17. McGraw‐Hill. pp. 167–172. ISBN 9780470131794.
- ^ H.Hecht, G.Jander, H.Schlapmann Z. Anorg. Allgem. Chem. Vol.254, p.255 (1947)
- ^ J H von Barner Inorg Chem 1985 24 1686
- ^ David R. Lide, ed. Handbook of Chemistry and Physics, 85th Edition, Internet Version 2005. CRC Press, 2005.
External links edit
- "Emergency First Aid Treatment Guide - Gallium Trichloride". United States Environmental Protection Agency. Archived from the original on 2004-11-12.