Gallium(III) chloride
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| Other names
Gallium trichloride, Trichlorogallium, Trichlorogallane
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.033.268 |
PubChemCID
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CompTox Dashboard(EPA)
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| Properties | |
| GaCl 3 | |
| Molar mass | 176.073 g/mol (anhydrous) 194.10 g/mol (monohydrate) |
| Appearance | colorless crystals |
| Density | 2.47 g/cm3(anhydrous) |
| Melting point | 77.9 °C (172.2 °F; 351.0 K) (anhydrous) 44.4 °C (monohydrate) |
| Boiling point | 201 °C (394 °F; 474 K) (anhydrous) |
| very soluble | |
| Solubility | soluble inbenzene,CCl4,CS2,andalkanes |
| −63.0·10−6cm3/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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| 469 Å3 | |
| Hazards | |
| GHSlabelling: | |
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| Danger | |
| H314 | |
| NFPA 704(fire diamond) | |
| Flash point | Non-flammable |
| Lethal doseor concentration (LD, LC): | |
LD50(median dose)
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4700 mg/kg (rat, oral) |
| Related compounds | |
Otheranions
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Gallium(III) fluoride Gallium(III) bromide Gallium(III) iodide |
Othercations
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Aluminium chloride Indium(III) chloride Thallium(III) chloride |
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).
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Gallium(III) chlorideis aninorganic chemical compoundwith the formula GaCl3which forms a monohydrate, GaCl3·H2O. Solid gallium(III) chloride is adeliquescentwhite solid and exists as adimerwith 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 ofgalliumand a reagent inorganic synthesis.[3]
As aLewis acid,GaCl3is milder thanaluminium chloride.It is also easier to reduce than aluminium chloride. The coordination chemistry of Ga(III) and Fe(III) are similar, so gallium(III) chloride has been used as a diamagnetic analogue offerric chloride.
Preparation
[edit]Gallium(III) chloride can be prepared from the elements by heatinggalliummetal in a stream ofchlorineat 200 °C and purifying the product by sublimation under vacuum.[4][5]
- 2 Ga + 3 Cl2→ 2 GaCl3
It can also be prepared from by heatinggallium oxidewiththionyl chloride:[6]
- Ga2O3+ 3 SOCl2→ 2 GaCl3+ 3 SO2
Gallium metal reacts slowly with hydrochloric acid, producinghydrogengas.[7]Evaporation of this solution produces the monohydrate.[8]
Structure
[edit]As a solid, it adopts a bitetrahedral structure with two bridging chlorides. Its structure resembles that ofaluminium tribromide.In contrastAlCl3andInCl3feature contain 6 coordinate metal centers. As a consequence of its molecular nature and associated lowlattice energy,gallium(III) chloride has a lower melting point vs the aluminium and indium trihalides. The formula of Ga2Cl6is often written as Ga2(μ-Cl)2Cl4.[1]
In the gas-phase, the dimeric (Ga2Cl6) andtrigonal planarmonomeric (GaCl3) are in a temperature-dependent equilibrium, with higher temperatures favoring the monomeric form. At 870 K, all gas-phase molecules are effectively in the monomeric form.[9]
In the monohydrate, the gallium is tetrahedrally coordinated with threechlorinemolecules and one water molecule.[8]
Properties
[edit]Physical
[edit]Gallium(III) chloride is adiamagneticanddeliquescentcolorless white solid that melts at 77.9 °C and boils at 201 °C without decomposition to the elements. This low melting point results from the fact that it forms discrete Ga2Cl6molecules in the solid state. Gallium(III) chloride dissolves in water with the release of heat to form a colorless solution, which when evaporated, produces a colorless monohydrate, which melts at 44.4 °C.[8][10][11]
Chemical
[edit]Galliumis the lightest member of Group 13 to have a fulldshell, (gallium has the electronic configuration [Ar] 3d104s24p1) below the valence electrons that could take part ind-π bonding with ligands. The low oxidation state of Ga in Ga(III)Cl3,along with the lowelectronegativityand highpolarisability,allow GaCl3to behave as a "soft acid" in terms of theHSAB theory.[12]The strength of the bonds between gallium halides and ligands have been extensively studied. What emerges is:[13]
- GaCl3is a weakerLewis acidthan AlCl3towards N and O donors e.g.pyridine
- GaCl3is a strongerLewis acidthan AlCl3towardsthioetherse.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 KGa2Cl7that have a chloridebridgedanion are known.[14] In a molten mixture of KCl and GaCl3,the following equilibrium exists:
- 2 GaCl4−⇌ Ga2Cl7−+ Cl−
When dissolved in water, gallium(III) chloride dissociates into the octahederal [Ga(H2O)6]3+and Cl-ions forming an acidic solution, due to the hydrolysis of the hexaaquogallium(III) ion:[15]
- [Ga(H2O)6]3+→ [Ga(H2O)5OH]2++ H+(pKa= 3.0)
In basic solution, it hydrolyzes togallium(III) hydroxide,which redissolves with the addition of morehydroxide,possibly to form Ga(OH)4-.[15]
Uses
[edit]Organic synthesis
[edit]Gallium(III) chloride is aLewis acid catalyst,such as in theFriedel–Crafts reaction,which is able to substitute more common lewis acids such asferric chloride.Gallium complexes strongly with π-donors, especiallysilylethynes,producing a strongly electrophilic complex. These complexes are used as an alkylating agent for aromatic hydrocarbons.[3]
It is also used incarbogallation reactionsof compounds with a carbon-carbon triple bond. It is also used as a catalyst in many organic reactions.[3]
Organogallium compounds
[edit]It is a precursor toorganogallium reagents.For example,trimethylgallium,an organogallium compound used inMOCVDto produce various gallium-containingsemiconductors,is produced by the reaction of gallium(III) chloride with various alkylating agents, such asdimethylzinc,trimethylaluminium,ormethylmagnesium iodide.[16][17][18]
Purification of gallium
[edit]Gallium(III) chloride is an intermediate in various gallium purification processes, where gallium(III) chloride isfractionally distilledor extracted from acid solutions.[7]
Detection of solar neutrinos
[edit]110 tons of gallium(III) chloride aqueous solution was used in theGALLEXand GNO experiments performed atLaboratori Nazionali del Gran Sassoin Italy to detectsolar 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.[10]
See also
[edit]References
[edit]- ^abSergey 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.ISBN0-19-855370-6.
- ^abcYamaguchi, 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,ISBN9780470842898
- ^Roger A. Kovar; J. A. Dilts (1977). "Gallium Trichloride".Inorganic Syntheses Volume 17.McGraw‐Hill. pp. 167–172.ISBN9780470131794.
- ^Gray, Floyd (2013). "Gallium and Gallium Compounds".Kirk-Othmer Encyclopedia of Chemical Technology.doi:10.1002/0471238961.0701121219010215.a01.pub3.ISBN9780471238966.
- ^H. Hecht; G. Jander; H. Schlapmann (1947). "Über die Einwirkung von Thionylchlorid auf Oxyde" [On the effect of thionyl chloride on oxides].Zeitschrift für anorganische Chemie.254(5–6): 255–264.doi:10.1002/zaac.19472540501.
- ^abGreber, Jörg (2000). "Gallium and Gallium Compounds".Ullmann's Encyclopedia of Industrial Chemistry.doi:10.1002/14356007.a12_163.ISBN9783527306732.
- ^abcJacques Roziere; Marie-Thérèse Roziere-Bories; Alain Manteghetti; Antoine Potier (1974). "Hydrates des halogenures de gallium. II Spectroscopie de vibration des complexes coordinés GaX3•H2O (X = Cl ou Br)".Canadian Journal of Chemistry(in French).52(18): 3274–3280.doi:10.1139/v74-483.
- ^Viacheslav I. Tsirelnikov; Boris V. Lokshin; Petr Melnikov; Valter A. Nascimento (2012). "On the Existence of the Trimer of Gallium Trichloride in the Gaseous Phase".Zeitschrift für anorganische und allgemeine Chemie.638(14): 2335–2339.doi:10.1002/zaac.201200282.
- ^abDavid R. Lide, ed.Handbook of Chemistry and Physics, 85th Edition,Internet Version 2005. CRC Press, 2005.
- ^J. Burgess; J. Kijowski (1981). "Enthalpies of solution of chlorides and iodides of gallium(III), indium(III), thorium(IV) and uranium(IV)".Journal of Inorganic and Nuclear Chemistry.43(11): 2649–2652.doi:10.1016/0022-1902(81)80592-1.
- ^Housecroft, Catherine E.; Sharpe, Alan G. (2018) [2001].Inorganic Chemistry(5th ed.). Harlow, Essex:Pearson Education.ISBN978-1-292-13414-7.
- ^Greenwood, Norman N.;Earnshaw, Alan (1997).Chemistry of the Elements(2nd ed.).Butterworth-Heinemann.pp. 237–239.ISBN978-0-08-037941-8.
- ^Jens H. Von Barner (1985). "Potentiometric and Raman spectroscopic study of the complex formation of gallium(III) in potassium chloride-aluminum chloride melts at 300C".Inorganic Chemistry.24(11): 1686–1689.doi:10.1021/ic00205a019.
- ^abScott A. Wood; Iain M. Samson (2006). "The aqueous geochemistry of gallium, germanium, indium and scandium".Ore Geology Reviews.28(1): 57–102.doi:10.1016/j.oregeorev.2003.06.002.
- ^Kraus, C. A.; Toonder, F. E. (1933)."Trimethyl Gallium, Trimethyl Gallium Etherate and Trimethyl Gallium Ammine".PNAS.19(3): 292–8.Bibcode:1933PNAS...19..292K.doi:10.1073/pnas.19.3.292.PMC1085965.PMID16577510.
- ^Foster, Douglas F.; Cole-Hamilton, David J. (1997). "Electronic Grade Alkyls of Group 12 and 13 Elements".Inorganic Syntheses.Vol. 31. p. 29-66.doi:10.1002/9780470132623.ch7.ISBN978-0-471-15288-0.
- ^WO application 2014078263,Liam P. Spencer, James C. Stevens, Deodatta Vinayak Shenai-Khatkhate, "Methods of producing trimethylgallium", published 2014-05-22
Further reading
[edit]- Greenwood, Norman N.;Earnshaw, Alan (1997).Chemistry of the Elements(2nd ed.).Butterworth-Heinemann.ISBN978-0-08-037941-8.
External links
[edit]- "Emergency First Aid Treatment Guide - Gallium Trichloride".United States Environmental Protection Agency.Archived fromthe originalon 2004-11-12.