Caesium auride

Caesium auride is the inorganic compound with the formula CsAu. It is the Cs⁺ salt of the unusual Au⁻ anion.^[2]

Caesium auride

Solution of CsAu(left), pure CsAu(right)
Names
IUPAC name Caesium auride
Identifiers
CAS Number	12256-37-0 Y
3D model (JSmol)	covalent form: Interactive image ionic form: Interactive image
ChemSpider	65322210
PubChem CID	71308168
InChI InChI=1S/Au.Cs N Key: COOMJVRPVOQALF-UHFFFAOYSA-N N
SMILES covalent form: [Cs][Au] ionic form: [Cs+].[Au-]
Properties
Chemical formula	AuCs
Molar mass	329.872022 g·mol−1
Appearance	Yellow crystals
Melting point	580 °C (1,076 °F; 853 K)[1]
Solubility in water	reacts violently
Structure
Crystal structure	CsCl
Lattice constant	a = 4.24 Å[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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]