Caesium auride explained
Caesium auride is the inorganic compound with the formula CsAu. It is the Cs+ salt of the unusual Au− anion.[1]
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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. Despite being a compound of two metals, CsAu lacks metallic properties since it is a salt with localized charges; it instead behaves as a semiconductor with band gap 2.6 eV.[2]
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.[3]
Further reading
- Chemical Society Reviews . 37 . 9 . 2008 . The chemistry of gold as an anion . Martin . Jansen . 1826–1835 . 10.1039/B708844M . 18762832 . —includes photograph of the compound.
Notes and References
- William J. . Peer . J. J. . Lagowski . J J Lagowski . 1978 . J. Am. Chem. Soc. . 100 . 6260–6261 . Metal-Ammonia Solutions. 11. Au−, a Solvated Transition Metal Anion . 10.1021/ja00487a064 .
- Norrby . Lars J. . Why is mercury liquid? Or, why do relativistic effects not get into chemistry textbooks? . Journal of Chemical Education . February 1991 . 68 . 2 . 110 . 10.1021/ED068P110. 1991JChEd..68..110N .
- Effects of relativistic motion of electrons on the chemistry of gold and platinum. Solid State Sciences. 2005-11-30. 7. 12. 1464–1474. 10.1016/j.solidstatesciences.2005.06.015. Jansen. Martin. 2005SSSci...7.1464J. free.
