Ammonium hexachloroiridate(IV)
{{Chembox
| ImageFile1 = (NH4)2IrCl6.svg
| ImageSize1 = 260 px
| ImageFile2 = (NH4)2PtCl6Xray.tif
| ImageSize2 = 260 px
| IUPACName = Ammonium hexachloroiridate(IV)
| OtherNames =
|Section1={{Chembox Identifiers
| CASNo = 16940-92-4
| PubChem = 16211476
| EC_number = 241-007-0
| ChEBI = 60132
| ChemSpiderID = 10791939
| InChI=1S/6ClH.Ir.2H3N/h6*1H;;2*1H3/q;;;;;;+4;;/p-4
| InChIKey = LWNOUTCTZQNGEN-UHFFFAOYSA-J
| SMILES = [NH4+].[NH4+].Cl[Ir-2](Cl)(Cl)(Cl)(Cl)Cl }}
|Section2={{Chembox Properties
| H=8|N=2|Cl=6|Ir=1
| MolarMass = 441.01
| Appearance = red solid
| Density =
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|Section3={{Chembox Hazards
| MainHazards =
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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, one of the most common complexes of iridium(IV). A related but ill-defined compound is iridium tetrachloride, which has been used interchangeably.{{cite journal|title=Iridium(IV) Chloride|author=Thomas R. B. Mitchell|year=2001|doi=10.1002/047084289X.ri050|journal=E-EROS Encyclopedia of Reagents for Organic Synthesis|isbn=0471936235 }}
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.{{cite journal|last1=Bokii|first1=G. B.|last2=Ussikov|first2=P.I.|title=Roentgenographische Untersuchung der Struktur des Ammonium-Chlor-Iridats (NH4)2IrCl6|journal=Doklady Akademii Nauk SSSR|year=1940|volume=26|page=782-784}}
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 diammonium hexachlorometallates.{{cite book|author1=H. L. Grube|chapter=Sodium Hexachloroiridate(VI)|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=2pages=1594}}
Uses
It is an 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:{{cite book|display-authors=8|author=Renner, H.|author2=Schlamp, G.|author3=Kleinwächter, I.|author4=Drost, E.|author5=Lüschow, H. M.|author6=Tews, P.|author7=Panster, P.|author8=Diehl, M.|author9=Lang, J.|author10=Kreuzer, T.|author11=Knödler, A.|author12=Starz, K. A.|author13=Dermann, K.|author14=Rothaut, J.|author15=Drieselman, R.|chapter=Platinum Group Metals and Compounds|title=Ullmann's Encyclopedia of Industrial Chemistry|publisher=Wiley|date=2002|doi=10.1002/14356007.a21_075|isbn=9783527303854 }}
:{{chem2|(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 attributed to 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.{{Greenwood&Earnshaw2nd|page=1121}}
References
{{reflist}}
{{Iridium compounds}}
{{Ammonium salts}}