Caesium auride

Preparation and reactions

CsAu is obtained by heating a stoichiometric mixture of caesium and gold. The two metallic-yellow liquids react to give a transparent yellow product.

The compound hydrolyzes readily, yielding caesium hydroxide, metallic gold, and hydrogen.

:2 CsAu + 2 H2O → 2 CsOH + 2 Au + H2

The solution in liquid ammonia is brown, and the ammonia adduct is blue; the latter has ammonia molecules intercalated between layers of the CsAu crystal parallel to the (110) plane. Solutions undergo metathesis with tetramethylammonium loaded ion exchange resin to give tetramethylammonium auride.

Crystal structure

Caesium auride has a cubic lattice structure of the CsCl type. Each caesium atom is octahedrally coordinated with 8 gold atoms, and vice versa. The lattice constant at ambient conditions is approximately , close to that of CsCl but slightly larger due to the larger ionic radius compared to . The bonding is predominantly ionic, as found by X-ray photoelectron spectroscopy, because gold has a much higher electronegativity than caesium.

References

References

1. (June 1961). "Das Verhalten der Alkalimetalle zu Kupfer, Silber und Gold". Zeitschrift für anorganische und allgemeine Chemie.
2. (1978). "Metal-Ammonia Solutions. 11. Au⁻, a Solvated Transition Metal Anion". J. Am. Chem. Soc..
3. (February 1991). "Why is mercury liquid? Or, why do relativistic effects not get into chemistry textbooks?". Journal of Chemical Education.
4. Jansen, Martin. (2005-11-30). "Effects of relativistic motion of electrons on the chemistry of gold and platinum". Solid State Sciences.
5. "Cesium Compounds".