Gold(I,III) chloride

Gold(I,III) chloride is the inorganic compound with the chemical formula Au₄Cl₈. It is an example of a mixed valence compound as it contains gold in two oxidation states; square-planar gold(III) and almost linear gold(I). The compound, which is black, is photosensitive as well as air- and moisture-sensitive.

Gold(I,III) chloride

Names
Systematic IUPAC name tetra-μ-chlorotetrachlorotetragold
Other names Mixed gold chloride, Tetragold octachloride
Identifiers
CAS Number	62792-24-9 Y
3D model (JSmol)	Interactive image Interactive image
PubChem CID	139092506
InChI InChI=1S/4Au.4ClH.4Cl/h;;;;4*1H;;;;/q;;2*+2;;;;;;;;/p-4 N Key: NWBJVUUFMJPGPV-UHFFFAOYSA-J N
SMILES Cl[Au]1(Cl)[Cl][Au][Cl][Au](Cl)(Cl)[Cl][Au][Cl]1 [Cl-].[Cl-].[Cl-].[Cl-].[Cl-].[Cl-].[Cl-].[Cl-].[Au+].[Au+].[Au+3].[Au+3]
Properties
Chemical formula	Au 4Cl 8
Molar mass	1071.490 g mol−1
Appearance	black crystals
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Synthesis

According to the procedure by Calderazzo et al., gold(I,III) chloride may be prepared by the reaction of gold(III) chloride with gold carbonyl chloride or carbon monoxide at room temperature in thionyl chloride.

Au₂(CO)Cl₄ + Au₂Cl₆ → COCl₂ + Au₄Cl₈

2 Au₂Cl₆ + 2 CO → Au₄Cl₈ + 2 COCl₂

Structure and properties

Single crystals of gold(I,III) chloride are triclinic with a P1 space group and consist of discrete Au₄Cl₈ molecules with idealised C_2h symmetry. Within this the Au(I) centers are linearly coordinated with a Cl-Au-Cl bond angle of 175.0° (close to the ideal value of 180°) and an average bond length of 2.30 Å. The Au(III) centers adopt a slightly irregular square-planar conformation with the Au-Cl bond lengths for bridging chlorides (2.33 Å) being slightly longer than those of terminal chlorides (2.24 Å).