Gold(I) chloride

Gold(I) chloride
Names
IUPAC name
Gold(I) chloride
Other names
Aurous chloride
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.583
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/Au.ClH/h;1H/q+1;/p-1 checkY
    Key: FDWREHZXQUYJFJ-UHFFFAOYSA-M checkY
  • InChI=1/Au.ClH/h;1H/q+1;/p-1
    Key: FDWREHZXQUYJFJ-REWHXWOFAM
SMILES
  • [Au]Cl
Properties
Chemical formula
 AuCl
Molar mass 232.423 g/mol
Appearance yellow solid[1]
Density 7.6 g/cm3[2]
Melting point 210 °C (410 °F; 483 K) (decomposition)[3]
Solubility in water
 Insoluble (cold water)
Reacts (warm water)[2]
Solubility Soluble in HCl, HBr organic solvents[2]
Magnetic susceptibility (χ)
 −67.0·10−6 cm3/mol[1]
Structure[4]
Crystal structure
 Tetragonal, tI16
Space group
 I41/amd, No. 141
Lattice constant
a = 6.734 Å, c = 8.674 Å
Thermochemistry
Std enthalpy of
formation (ΔfH⦵298)
 –34.7 kJ/mol[1]
Hazards
GHS labelling:
Pictograms
 GHS05: CorrosiveGHS07: Exclamation mark
Signal word
 Danger
Hazard statements
 H314, H317
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
3
1
0
Safety data sheet (SDS) MSDS (Fisher)
Related compounds
Other anions
 Gold(I) fluoride
Gold(I) bromide
Gold(I) iodide
Other cations
 Copper(I) chloride
Silver chloride
Related compounds
 Gold(I,III) chloride
Gold(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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Infobox references

Gold(I) chloride is a compound of gold and chlorine with the chemical formula AuCl. It is a metastable yellow solid that hydrolyses in warm water and decomposes to gold and chlorine gas at elevated temperatures. It has limited uses in organic chemistry as a Lewis acid.

History

Gold(I) chloride was first reported by Louis Jacques Thénard in 1814, who had carefully heated gold(III) chloride and isolated a yellow solid, claiming that it was the proto-muriate of gold. Joseph Proust disputed his claim, along with Thénard's other erroneous claims, such as of gold(I) oxide, later in the year.[5][6] However, gold(I) chloride was found to be a distinct compound from gold(III) chloride, as the synthesis was repeated by others, such as Hans Peter Jørgen Julius Thomsen. The structure was elucidated in 1974 by X-ray diffraction.[4][7]

Preparation

A modern synthesis entails the decomposition of gold(III) chloride under a chlorine atmosphere at 247 °C:[4]

AuCl3 → AuCl + Cl2

Gold(III) chloride can also be heated in air at 185 °C to produce gold(I) chloride with careful temperature control.[7]

Structure

The structure of gold(I) chloride, which crystallizes in the tetragonal crystal system, consists of zig-zag chains of gold and chlorine, similar to gold(I) bromide and gold(I) iodide. The Au-Cl bond length is 2.36 Å, and the chain bends at the Cl with a bond angle of 92°.[4][8][9]

Reactions

Gold(I) chloride decomposes to gold metal and chlorine gas at around 210 °C:[3][10]

2AuCl → 2Au + Cl2

Although a region of stability exists at higher temperatures and appropriate chlorine vapour pressures (254 to 282 °C at PCl2 = 1 atm), the compound remains metastable at ambient conditions. In warm water, the compound dispropotionates to metallic gold and gold(III) chloride in an autoredox reaction:[2][4][11][12]

3 AuCl → 2 Au + AuCl3

At still higher temperatures, around 500 °C, all gold chlorides convert to gold even under a chlorine atmosphere. This conversion is key to the Miller process, which is widely used for the purification of gold.[10][13]

In hydrochloric acid, gold(I) chloride dissolves to form the colorless dichloroaurate(I) (AuCl2–) ion. At higher pH, this complex hydrolyses to gold(I)-hydroxo complexes and disproportionates to gold and gold(III).[14] However, the salts of the dichloroaurate(I) ion, such as the tetrabutylammonium salt, are prepared from the respective tetrachloroaurate(III) ion instead from gold(I) chloride.[15]

Reaction with potassium bromide yields potassium auric bromide and potassium chloride with separation of metallic gold:[2]

3 AuCl + 4 KBr → KAuBr4 + 2 Au + 3 KCl

Carbon monoxide reduces gold(I) chloride at 110 °C to form phosgene:

2AuCl + CO → 2Au + COCl2

However, under benzene, it forms carbonylchlorogold(I) (COAuCl) instead.[16][17]

Organogold(I) complexes

Various gold(I) chloride complexes are known, such as Ph3PAuCl and Me2SAuCl. However, the synthesis of these does not utilize gold(I) chloride, but instead goes through a direct reduction from Au(III) in the presence of the ligand. These complexes are the major gateways to other organogold(I) complexes.[18][19][20]

Applications

Gold(I) chloride mostly only has applications in organogold catalyzed organic reactions. It is used as a Lewis acid to activate alkenes, alkynes, and allenes. For example, acetylenic acids cycloisomerize in the presence of gold(I) chloride:[21][22]

AuCl catalyzed cycloisomerization

Safety

Generally, gold(I) compounds are less toxic than gold(III) compounds. However, gold(I) chloride is a skin sensitizer that may irritate the skin and eyes.[13][23]

References

  1. ^ a b c Haynes, W. M., ed. (2015). CRC Handbook of Chemistry and Physics (95th ed.). Boca Raton, Florida: CRC Press/Taylor & Francis. ISBN 978-1482208672.
  2. ^ a b c d e Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  3. ^ a b Ya-jie Zheng; Wei Guo; Meng Bai; Xing-wen Yang (2006). "Preparation of chloroauric acid and its thermal decomposition". The Chinese Journal of Nonferrous Metals (in Chinese). 16 (11): 1976–1982. Archived from the original on March 27, 2024.
  4. ^ a b c d e E. M. W. Janssen; J. C. W. Folmer; G. A. Wiegers (1974). "The preparation and crystal structure of gold monochloride, AuCl". Journal of the Less Common Metals. 38 (1): 71–76. doi:10.1016/0022-5088(74)90204-5.
  5. ^ Louis Jacques Thénard (1814). "Muriate d'Or". Traité de chimie élémentaire, théorique et pratique, Vol. 2 [Treatise on Elementary Chemistry, Theoretical and Practical, Volume 2] (in French). Lyon Public Library: Chez Crochard. pp. 594–597.
  6. ^ Joseph Proust (1814). "Seconde Lettre sur L'Incertitude de Quelques Oxidations". Journal de physique, de chimie, d'histoire naturelle et des arts (in French). 74: 321–342. Retrieved 13 February 2026.
  7. ^ a b Julius Thomsen (1876). "Darstellung und Eigenschaften der Chlor- und Bromverbindungen und des Oxyds des Goldes". Journal für Praktische Chemie (in German). 13 (1): 337–347. doi:10.1002/prac.18760130119.
  8. ^ Janssen, E.M.W.; Wiegers, G.A. (1978). "Crystal growth and the crystal structures of two modifications of gold monobromide, I-AuBr and P-AuBr". Journal of the Less Common Metals. 57 (2): P47–P57. doi:10.1016/0022-5088(78)90248-5. Retrieved 2026-02-13.
  9. ^ Tang, Zhongjia; Litvinchuk, A. P.; Lee, Hye-G.; Guloy, Arnold M. (1998-09-01). "Crystal Structure and Vibrational Spectra of a New Viologen Gold(I) Iodide". Inorganic Chemistry. 37 (19): 4752–4753. doi:10.1021/ic980141q. ISSN 0020-1669. Retrieved 2026-02-13.
  10. ^ a b Yiqin Chen; Xuezeng Tian; Wei Zeng; Xupeng Zhu; Hailong Hu; Huigao Duan (2015). "Vapor-phase preparation of gold nanocrystals by chloroauric acid pyrolysis". Journal of Colloid and Interface Science. 439. Elsevier: 21–27. Bibcode:2015JCIS..439...21C. doi:10.1016/j.jcis.2014.10.017. PMID 25463171.
  11. ^ Housecroft, C. E.; Sharpe, A. G. (2018). Inorganic Chemistry (5th ed.). Prentice Hall. p. 863. ISBN 978-1292134147.
  12. ^ E.M.W. Janssen; F. Pohlmann; G. A. Wiegers (1976). "The phase diagram of the gold-chlorine system". Journal of the Less Common Metals. 45 (2): 261–273. doi:10.1016/0022-5088(76)90272-1.
  13. ^ a b Renner, Hermann; Schlamp, Günther; Hollmann, Dieter; Lüschow, Hans Martin; Tews, Peter; Rothaut, Josef; Dermann, Klaus; Knödler, Alfons; Hecht, Christian; Schlott, Martin; Drieselmann, Ralf; Peter, Catrin; Schiele, Rainer (2000). "Gold, Gold Alloys, and Gold Compounds". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a12_499. ISBN 3527306730.
  14. ^ Christopher H. Gammons; Yunmei Yu; A. E. Williams-Jones (1997). "The disproportionation of gold(I) chloride complexes at 25 to 200°C". Geochimica et Cosmochimica Acta. 61 (10): 1971–1983. doi:10.1016/S0016-7037(97)00060-4.
  15. ^ Edwards, D. A. (1991). "Synthesis of Complex Halides Derived from Monohalides of Group‐IB". Inorganic Reactions and Methods. Vol. 4. Wiley. p. 127–133. doi:10.1002/9780470145180.ch72. ISBN 978-0-471-18657-1. Retrieved 2026-02-13.
  16. ^ T.A. Ryan; E.A. Seddon; K.R. Seddon; C. Ryan (1996). Phosgene And Related Carbonyl Halides. Elsevier Science. pp. 242–243. ISBN 9780080538808.
  17. ^ M. S. Kharasch; H. S. Isbell (1930). "The Chemistry of Organic Gold Compounds. I. Aurous Chloride Carbonyl and a Method of Linking Carbon to Carbon". Journal of the American Chemical Society. 52 (7): 2919–2927. doi:10.1021/ja01370a052.
  18. ^ Pierre Braunstein; Hans Lehner; Dominique Matt (1990). A Platinum-Gold Cluster: Chloro-1κCl-Bis(Triethylphosphine-1κP)Bis(Triphenylphosphine)-2κP, 3κP-Triangulo- Digold-Platinum(1 +) Trifluoromethanesulfonate. Inorganic Syntheses. Vol. 27. pp. 218–221. doi:10.1002/9780470132586.ch42.
  19. ^ Marie-Claude Brandys, Michael C. Jennings and Richard J. Puddephatt (2000). "Luminescent gold(I) macrocycles with diphosphine and 4,4-bipyridyl ligands". J. Chem. Soc., Dalton Trans. (24): 4601–4606. doi:10.1039/b005251p.
  20. ^ de Orbe, M. Elena; Echavarren, Antonio M. (2016). "Intermolecular [2+2] Cycloaddition of Alkynes with Alkenes Catalyzed by Gold(I)". Org. Synth. 93: 115. doi:10.15227/orgsyn.093.0115.
  21. ^ Li, Changkun; Wang, Jianbo (2009). "Gold Chloride". Encyclopedia of Reagents for Organic Synthesis. Chichester, UK: John Wiley & Sons, Ltd. doi:10.1002/047084289x.rn01001. ISBN 978-0-471-93623-7.
  22. ^ Genin, Emilie; Toullec, Patrick Yves; Antoniotti, Sylvain; Brancour, Célia; Genêt, Jean-Pierre; Michelet, Véronique (2006-03-01). "Room Temperature Au(I)-Catalyzed exo -Selective Cycloisomerization of Acetylenic Acids: An Entry to Functionalized γ-Lactones". Journal of the American Chemical Society. 128 (10): 3112–3113. doi:10.1021/ja056857j. ISSN 0002-7863.
  23. ^ "SAFETY DATA SHEET Gold(I) chloride". Fisher Scientific. ThermoFisher Scientific. Retrieved 13 February 2026.
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