Gold(I,III) chloride is the inorganic compound with the chemical formula Au4Cl8. It is 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 chloride1 or carbon monoxide2 at room temperature in thionyl chloride.
Au2(CO)Cl4 + Au2Cl6 → COCl2 + Au4Cl8 2 Au2Cl6 + 2 CO → Au4Cl8 + 2 COCl2Structure 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.3 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).
References
Dell'Amico, Daniela Belli; Calderazzo, Fausto; Marchetti, Fabio; Merlino, Stefano; Perego, Giovanni (1977). "X-Ray crystal and molecular structure of Au4Cl8, the product of the reduction of Au2Cl6 by Au(CO)Cl". Journal of the Chemical Society, Chemical Communications (1): 31. doi:10.1039/C39770000031. /wiki/Doi_(identifier) ↩
Dell'Amico, Daniela Belli; Calderazzo, Fausto; Marchetti, Fabio; Merlino, Stefano (1982). "Synthesis and molecular structure of [Au4Cl8], and the isolation of [Pt(CO)Cl5]− in thionyl chloride". Journal of the Chemical Society, Dalton Transactions (11): 2257. doi:10.1039/DT9820002257. /wiki/Doi_(identifier) ↩
Dell'Amico, Daniela Belli; Calderazzo, Fausto; Marchetti, Fabio; Merlino, Stefano; Perego, Giovanni (1977). "X-Ray crystal and molecular structure of Au4Cl8, the product of the reduction of Au2Cl6 by Au(CO)Cl". Journal of the Chemical Society, Chemical Communications (1): 31. doi:10.1039/C39770000031. /wiki/Doi_(identifier) ↩