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.

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.

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 C2h 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).