Gold(III) bromide

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Gold(III) bromide
Gold-tribromide-dimer-3D-balls.png
Gold-tribromide-dimer-3D-vdW.png
Names
Other names
Auric bromide
Gold bromide
Gold(III) bromide
Gold tribromide
Digold hexabromide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.582 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-654-2
164245
PubChem CID
UNII
  • InChI=1S/Au.3BrH/h;3*1H/q+3;;;/p-3 Yes check.svgY
    Key: OVWPJGBVJCTEBJ-UHFFFAOYSA-K Yes check.svgY
  • InChI=1S/Au.3BrH/h;3*1H/q+3;;;/p-3
    Key: OVWPJGBVJCTEBJ-DFZHHIFOAK
  • Key: OVWPJGBVJCTEBJ-UHFFFAOYSA-K
  • ionic form:[Au+3].[Br-].[Br-].[Br-]
  • covalent form:Br[Au-]1(Br)[Br+][Au-]([Br+]1)(Br)Br
Properties
AuBr3
Molar mass 436.679 g·mol−1
Appearancedark red to black crystals
Melting point 97.5 °C (207.5 °F; 370.6 K)
Slightly soluble [1]
Hazards
GHS labelling: [2]
GHS-pictogram-acid.svg
Danger
H314
P260, P264, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability (red): no hazard codeInstability (yellow): no hazard codeSpecial hazards (white): no code
3
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 ?)

Gold(III) bromide is a dark-red to black crystalline solid. [3] [4] [5] It has the empirical formula AuBr3, but exists as a dimer with the molecular formula Au2Br6 in which two gold atoms are bridged by two bromine atoms. [4] [5] [6] It is commonly referred to as gold(III) bromide, gold tribromide, and rarely but traditionally auric bromide, and sometimes as digold hexabromide. The analogous copper or silver tribromides do not exist. [7]

Contents

History

The first mention of any research or study of the gold halides dates back to the early-to-mid-19th century, and there are three primary researchers associated with the extensive investigation of this particular area of chemistry: Thomsen, Schottländer, and Krüss. [8] [9] [10] [11]

Structure

Gold(III) bromide adopts structures seen for the other gold(III) trihalide dimeric compounds, such as the chloride. The gold centers exhibit square planar coordination with bond angles of roughly 90 degrees. [5] [6]

Calculations indicate that in the hypothetical monomeric forms of the gold trihalides, the Jahn-Teller effect causes differences to arise in the structures of the gold halide complexes. For instance, gold(III) bromide contains one long and two short gold-bromine bonds whereas gold(III) chloride and gold(III) fluoride consist of two long and one short gold-halogen bonds. [6] Moreover, gold tribromide does not exhibit the same coordination around the central gold atom as gold trichloride or gold trifluoride. In the latter complexes, the coordination exhibits a T-conformation, but in gold tribromide the coordination exists as more of a dynamic balance between a Y-conformation and a T-conformation. This coordination difference can be attributed to the Jahn-Teller effect but more so to the decrease in π-back bonding of the gold atoms with the bromine ligands compared to the π-back bonding found with fluorine and chlorine ligands. It is also this decrease in π-back bonding which explains why gold tribromide is less stable than its trifluoride and trichloride counterparts. [6]

Gold bromide.svg

Preparation

The most common synthesis method of gold(III) bromide is heating gold and excess liquid bromine at 140 °C: [3]

2 Au + 3 Br2 → Au2Br6

Alternatively, the halide-exchange reaction of gold(III) chloride with hydrobromic acid has also been proven successful in synthesizing gold(III) bromide: [12]

Au2Cl6 + 6 HBr → 6 HCl + Au2Br6

Chemical properties

Gold(III) displays square planar coordination geometry. [5]

Gold(III) trihalides form a variety of four-coordinate adducts. [4] One example is the hydrate AuBr3·H2O. Another well known adduct is that with tetrahydrothiophene. [13] The tetrabromide is also known:

HBr + AuBr3 → H+[AuBr4]−

Uses

Catalytic chemistry

Gold(III) bromide catalyzes a variety of reactions. In one example, it catalyzes the Diels-Alder reaction of an enynal unit and carbonyl. [14]

Gold bromide in Diels-Alder reaction.svg

Another catalytic use of gold tribromide is in the nucleophilic substitution reaction of propargylic alcohols. In this reaction, the gold complex serves as an alcohol-activating agent to facilitate the substitution. [15]

Propargylic Alcohol Nucleophilic Substitution.svg

Ketamine detection

Gold(III) bromide can be used as a testing reagent for the presence of ketamine. [16]

0.25% AuBr3 0.1M NaOH is prepared to give a brownish-yellow solution. Two drops of this are added to a spotting plate and a small amount of ketamine is added. The mixture gives a deep purple color within approximately one minute, which turns to a dark, blackish-purple color within approximately two minutes.

Acetaminophen, ascorbic acid, heroin, lactose, mannitol, morphine, and sucrose all cause an instant colour change to purple, as do other compounds with phenol and hydroxyl groups.

Nothing commonly found in conjunction with ketamine gave the same colour change in the same time.

"The initial purple color may be due to the formation of a complex between the gold and the ketamine. The cause for the change of color from purple to dark blackish-purple is unknown; however, it may be due to a redox reaction that produces a small amount of colloidal gold." [16]

Related Research Articles

<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 (255.7 °F). Boiling less concentrated solutions releases H2O until the constant-boiling mixture composition is reached.

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

Vanadium(III) bromide, also known as vanadium tribromide, describes the inorganic compounds with the formula VBr3 and its hydrates. The anhydrous material is a green-black solid. In terms of its structure, the compound is polymeric with octahedral vanadium(III) surrounded by six bromide ligands.

<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">Tungsten(V) bromide</span> Chemical compound

Tungsten(V) bromide is the inorganic compound with the empirical formula WBr5. The compound consists of bioctahedral structure, with two bridging bromide ligands, so its molecular formula is W2Br10.

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.

<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.

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.

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

Indium(I) bromide is a chemical compound of indium and bromine. It is a red crystalline compound that is isostructural with β-TlI and has a distorted rock salt structure. Indium(I) bromide is generally made from the elements, heating indium metal with InBr3. It has been used in the sulfur lamp. In organic chemistry, it has been found to promote the coupling of α, α-dichloroketones to 1-aryl-butane-1,4-diones. Oxidative addition reactions with for example alkyl halides to give alkyl indium halides and with NiBr complexes to give Ni-In bonds are known. It is unstable in water decomposing into indium metal and indium tribromide. When indium dibromide is dissolved in water, InBr is produced as a, presumably, insoluble red precipitate, that then rapidly decomposes.

<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.

<span class="mw-page-title-main">Metal halides</span>

Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride.

Scandium bromide, or ScBr3, is a trihalide, hygroscopic, water-soluble chemical compound of scandium and bromine.

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

Rhodium(III) bromide refers to inorganic compounds of the formula RhBr3(H2O)n where n = 0 or approximately three. Both forms are brown solids. The hydrate is soluble in water and lower alcohols. It is used to prepare rhodium bromide complexes. Rhodium bromides are similar to the chlorides, but have attracted little academic or commercial attention.

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

Ruthenium(III) bromide is a chemical compound of ruthenium and bromine with the formula RuBr3. It is a dark brown solid that decomposes above 400 °C.

<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.

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

Dysprosium(III) bromide is an inorganic compound of bromine and dysprosium, with the chemical formula of DyBr3.

<span class="mw-page-title-main">Tungsten hexabromide</span> Chemical compound

Tungsten hexabromide, also known as tungsten(VI) bromide, is a chemical compound of tungsten and bromine with the formula WBr6. It is an air-sensitive dark grey powder that decomposes above 200 °C to tungsten(V) bromide and bromine.

References

  1. ↑ "Gold(III) bromide 99.999% trace metals". Sigma Aldrich. Retrieved 27 May 2021.
  2. ↑ "Gold tribromide". pubchem.ncbi.nlm.nih.gov.
  3. 1 2 Macintyre, J. E. (ed.) Dictionary of Inorganic Compounds; Chapman & Hall: London, 1992; vol. 1, pp. 121
  4. 1 2 3 Greenwood, N.N.; Earnshaw, A. Chemistry of the Elements; Butterworth-Heineman: Oxford,1997; pp. 1183-1185
  5. 1 2 3 4 Cotton, F.A.; Wilkinson, G.; Murillo, C.A.; Bochmann, M. Advanced Inorganic Chemistry; John Wiley & Sons: New York, 1999; pp. 1101-1102
  6. 1 2 3 4 Schulz, A.; Hargittai, M. Chem. Eur. J. 2001, vol. 7, pp. 3657-3670
  7. ↑ Schwerdtfeger, P. J. Am. Chem. Soc. 1989, vol. 111, pp. 7261-7262
  8. ↑ Lengefield, F. J. Am. Chem. Soc. 1901, vol. 26, pp. 324
  9. ↑ Thomsen, J. J. prakt. Chem. 1876, vol. 13, pp. 337
  10. ↑ Schottländer, Justus Liebigs Ann. Chem. , vol. 217, pp. 312
  11. ↑ Krüss, G. Ber. Dtsch. Chem. Ges. 1887, vol. 20, pp. 2634
  12. ↑ Dell'Amico, D.B.; Calderazzo, F.; Morvillo, A.; Pelizzi, G; Robino, P. J. Chem. Soc., Dalton Trans. 1991, pp. 3009-3016
  13. ↑ Nottingham, Chris; Barber, Verity; Lloyd-Jonesjournal=Organic Syntheses, Guy C. (2019). "Gold-Catalyzed Oxidative Coupling of Arenes and Arylsilanes". Org. Synth. 96: 150–178. doi:10.15227/orgsyn.096.0150.
  14. ↑ Asao, N.; Aikawa, H.; Yamamoto, Y. J. Am. Chem. Soc. 2004, vol. 126, pp. 7458-7459
  15. ↑ Georgy, M.; Boucard, V.; Campagne, J. J. Am. Chem. Soc. 2005, vol. 127, pp. 14180-14181
  16. 1 2 Sarwar, Mohammad. "A New, Highly Specific Color Test for Ketamine". The Microgram. Drug Enforcement Administration. Archived from the original on 2010-10-17. Retrieved 2012-01-26.
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