Appearance black crystals
|Molar mass 1,071.488 g/mol|
Gold(I,III) chloride is a black solid with the chemical formula Au4Cl8. It is an example of a mixed valence compound as it contains gold in two different oxidation states; square-planar gold(III) and almost linear gold(I). The compound must be handled carefully as it is photosensitive as well as extremely air and moisture sensitive.
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 Au2Cl6 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 bidging chlorides (2.33 Å) being slightly longer than those of terminal chlorides (2.24 Å).