 | |
 | |
 Solution of CsAu(left), pure CsAu(right) | |
| Names | |
|---|---|
| IUPAC name Caesium auride | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| |
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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] | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Caesium auride is theinorganic compound with the formula CsAu. It is the Cs+ salt of the unusual Au− anion.[2]
CsAu is obtained by heating astoichiometric mixture ofcaesium andgold. 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 withband gap 2.6 eV.[4]
The compound hydrolyzes readily, yieldingcaesium hydroxide, metallic gold, and hydrogen.[3]
The solution in liquidammonia is brown, and the ammoniaadductCsAu·NH3 is blue; the latter has ammonia moleculesintercalated between layers of the CsAu crystal parallel to the (110) plane. Solutions undergo metathesis withtetramethylammonium loaded ion exchange resin to givetetramethylammonium auride.[3]
Caesium auride has a cubic lattice structure of theCsCl type. Each caesium atom is octahedrally coordinated with 8 gold atoms, and vice versa. Thelattice constant at ambient conditions is approximately4.24 Å, close to that of CsCl but slightly larger due to the largerAu−
ionic radius compared toCl−
. The bonding is predominantlyionic,[5] as found byX-ray photoelectron spectroscopy, because gold has a much higher electronegativity than caesium.
