Potassium hexanitritocobaltate(III)

Potassium hexanitritocobaltate(III) is a salt with the formula K₃[Co(NO₂)₆]. It is a yellow solid that is poorly soluble in water. The compound finds some use as a yellow pigment under the name Indian Yellow.

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Potassium cobaltinitrite

Names
IUPAC name Potassium hexanitritocobaltate(III)
Other names Potassium cobaltinitrite
Identifiers
CAS Number	13782-01-9 Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.034.018
PubChem CID	25022080
UNII	40W79B48SV Y
CompTox Dashboard (EPA)	DTXSID60929905
InChI InChI=1S/Co.3K.6HNO2.H2O/c;;;;6*2-1-3;/h;;;;6*(H,2,3);1H2/q+3;3*+1;;;;;;;/p-6
SMILES N(=O)[O-].N(=O)[O-].N(=O)[O-].N(=O)[O-].N(=O)[O-].N(=O)[O-].[K+].[K+].[K+].[Co]
Properties
Chemical formula	K3[Co(NO2)6] (anhydrous) K3[Co(NO2)6]·1.5H2O (sesquihydrate)
Molar mass	452.26 g/mol (anhydrous) 479.284 g/mol (sesquihydrate)
Appearance	yellow cubic crystals (sesquihydrate)
Density	2.6 g/cm3 (sesquihydrate)
Solubility in water	slightly soluble in water (sesquihydrate)
Solubility	reacts with acids, insoluble in ethanol (sesquihydrate)[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

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The salt features potassium cations and an trianionic coordination complex. In the anion, cobalt is bound by six nitrito ligands, the overall complex having octahedral molecular geometry. The oxidation state of cobalt is 3+. Its low-spin d⁶ configuration confers kinetic stability and diamagnetism. The compound is prepared by combining cobalt(II) and nitrite salts in the presence of oxygen. The corresponding sodium cobaltinitrite is significantly more soluble in water.^[2]

The compound was first described in 1848 by Nikolaus Wolfgang Fischer in Breslau,^[3] and it is used as a yellow pigment called Aureolin.^[4][5]