Caesium auride is the
inorganic compound with the formula CsAu. It is the Cs+ salt of the unusual Au− anion.[2]
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.[3] 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.[4]
The compound hydrolyzes readily, yielding
caesium hydroxide, metallic gold, and hydrogen.[3]
2 CsAu + 2 H2O → 2 CsOH + 2 Au + H2
The solution in liquid
ammonia is brown, and the ammonia
adductCsAu·NH3 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]
References
^
abKienast, Gerhard; Verma, Jitendra; Klemm, Wilhelm (June 1961). "Das Verhalten der Alkalimetalle zu Kupfer, Silber und Gold". Zeitschrift für anorganische und allgemeine Chemie (in German). 310 (3): 143–169.
doi:
10.1002/zaac.19613100304.
^Peer, William J.;
Lagowski, J. J. (1978). "Metal-Ammonia Solutions. 11. Au−, a Solvated Transition Metal Anion". J. Am. Chem. Soc. 100: 6260–6261.
doi:
10.1021/ja00487a064.
^Norrby, Lars J. (February 1991). "Why is mercury liquid? Or, why do relativistic effects not get into chemistry textbooks?". Journal of Chemical Education. 68 (2): 110.
Bibcode:
1991JChEd..68..110N.
doi:
10.1021/ED068P110.
Further reading
Jansen, Martin (2008). "The chemistry of gold as an anion". Chemical Society Reviews. 37 (9): 1826–1835.
doi:
10.1039/B708844M.
PMID18762832.—includes photograph of the compound.