Caesium auride
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 Solution of CsAu(left), pure CsAu(right)
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| Names | |
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| IUPAC name
Caesium auride
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| Identifiers | |
3D model (
JSmol ) |
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PubChem CID
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| Properties | |
| AuCs | |
| Molar mass | 329.872022 g·mol−1 |
| Appearance | Yellow crystals |
| Melting point | 580 °C (1,076 °F; 853 K)[1] |
| reacts violently | |
| Structure | |
| CsCl | |
a = 4.24 Å[1]
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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 adduct CsAu·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
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Further reading
- Jansen, Martin (2008). "The chemistry of gold as an anion". Chemical Society Reviews. 37 (9): 1826–1835. PMID 18762832.—includes photograph of the compound.