Ammonium hexachloroiridate(IV)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.037.264 Edit this at Wikidata
EC Number
  • 241-007-0
  • InChI=1S/6ClH.Ir.2H3N/h6*1H;;2*1H3/q;;;;;;+4;;/p-4
    Key: LWNOUTCTZQNGEN-UHFFFAOYSA-J
  • [NH4+].[NH4+].Cl[Ir-2](Cl)(Cl)(Cl)(Cl)Cl
Properties
Cl6H8IrN2
Molar mass 441.01
Appearance red solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Ammonium hexachloroiridate(IV) is the inorganic compound with the formula (NH4)2[IrCl6]. This dark red solid is the ammonium salt of the iridium(IV) complex [IrCl6]2−. It is a commercially important iridium compound[1] one of the most common complexes of iridium(IV). A related but ill-defined compound is iridium tetrachloride, which is often used interchangeably.[2]

Structure and synthesis

The compound has been characterized by X-ray crystallography. The salt crystallizes in a cubic motif like that of ammonium hexachloroplatinate. The [IrCl6]2− centers adopt octahedral molecular geometry.[3]

The compound is prepared in the laboratory by the addition of ammonium chloride to an aqueous solution of sodium hexachloroiridate. The salt is poorly soluble, like most other ammonium hexachlorometallates.[4]

Uses

It is a key intermediate in the isolation of iridium from ores. Most other metals form insoluble sulfides when aqueous solutions of their chlorides are treated with hydrogen sulfide, but [IrCl6]2− resists ligand substitution. Upon heating under hydrogen, the solid salt converts to the metal:[1]

(NH4)2[IrCl6] + 2 H2 → Ir + 6 HCl + 2 NH3

Bonding

The electronic structure of ammonium hexachloroiridate(IV) has attracted much attention. Its magnetic moment is less than that calculated for one electron. This result is interpreted as the result of antiferromagnetic coupling between Ir centers mediated by Cl---Cl interactions. Electron spin resonance, studies reveal that more than half of the spin density resides on chloride, thus the description of the complex as Ir(IV) is an oversimplification.[5]

References

  1. ^ a b Renner, H.; Schlamp, G.; Kleinwächter, I.; Drost, E.; Lüschow, H. M.; Tews, P.; Panster, P.; Diehl, M.; et al. (2002). "Platinum group metals and compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley. doi:10.1002/14356007.a21_075. ISBN 9783527303854.
  2. ^ Thomas R. B. Mitchell (2001). "Iridium(IV) Chloride". E-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.ri050. ISBN 0471936235.
  3. ^ Bokii, G.B.; Ussikov, P.I. "Roentgenographische Untersuchung der Struktur des Ammonium-Chlor-Iridats (N H4)2IrCl6 Doklady Akademii Nauk SSSR 1940, vol. 26, p782-p784.
  4. ^ H. L. Grube (1963). "Sodium Hexachloroiridate(VI)". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2pages=1594. NY, NY: Academic Press.
  5. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1121. ISBN 978-0-08-037941-8.
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