Dipotassium hexachloroiridate
[CAS# 16920-56-2]

Identification

• Classification: Food additive >> Nutrition supplements >> Inorganic salts
• Name: Dipotassium hexachloroiridate
• Synonyms: Iridium potassium chloride
• Molecular Formula: K₂IrCl₆
• Molecular Weight: 483.13
• CAS Registry Number: 16920-56-2
• EC Number: 240-976-7
• SMILES: Cl[Ir-2](Cl)(Cl)(Cl)(Cl)Cl.[K+].[K+]

Properties

• Melting point: >385 °C (Expl.)

Safety Data

• Hazard Symbols: GHS05;GHS07 Warning
• Risk Statements: H290-H302+H312+H332-H302-H312-H315-H319-H332-H335
• Safety Statements: P234-P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P319-P321-P330-P332+P317-P337+P317-P362+P364-P390-P403+P233-P405-P406-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Skin sensitization	Skin Sens.	1	H317

Discovery and Applications

Dipotassium hexachloroiridate is an inorganic coordination compound with the formula K₂[IrCl₆]. It consists of the hexachloroiridate(IV) anion [IrCl₆]²⁻, where an iridium ion in the +4 oxidation state is coordinated octahedrally by six chloride ligands. The negative charge of the complex anion is balanced by two potassium cations, resulting in a stable crystalline salt that typically appears as an orange to reddish-orange solid.

The synthesis of dipotassium hexachloroiridate commonly involves the oxidation of iridium metal or iridium(III) salts in the presence of hydrochloric acid and potassium chloride with a suitable oxidizing agent, such as chlorine or hydrogen peroxide. This process converts iridium to its +4 oxidation state and forms the hexachloroiridate(IV) complex ion. The resulting dipotassium salt can be isolated by crystallization from aqueous solution.

Structurally, the [IrCl₆]²⁻ anion exhibits an octahedral geometry, characteristic of d⁵ low-spin iridium(IV) complexes. The coordination by six chloride ions stabilizes the iridium center, imparting notable chemical robustness to the compound. The potassium ions interact ionically with the complex anion, forming an extended crystalline lattice.

Dipotassium hexachloroiridate serves as a key precursor in iridium chemistry, especially in the synthesis of a variety of iridium coordination complexes and catalysts. It is utilized in homogeneous catalysis, where iridium complexes derived from this compound participate in hydrogenation, oxidation, and C–H activation reactions. The compound’s stable and well-defined structure makes it valuable for controlled ligand substitution reactions to create catalysts with specific electronic and steric properties.

In materials science, K₂[IrCl₆] is employed as a source of iridium for the preparation of iridium-based thin films, nanoparticles, and other functional materials used in electronics, catalysis, and energy applications. It is used in processes such as chemical vapor deposition and solution-phase synthesis to fabricate iridium-containing materials with desirable properties.

The compound is generally stable under ambient conditions but should be handled with care. It may be irritant upon contact or inhalation, and appropriate personal protective equipment is recommended when working with this material. Storage in a dry, well-ventilated area away from reducing agents and incompatible substances helps maintain its stability.

In summary, dipotassium hexachloroiridate is an orange crystalline salt composed of the octahedral hexachloroiridate(IV) anion balanced by potassium cations. It is a significant iridium(IV) coordination compound widely used as a precursor for catalyst synthesis and materials fabrication, valued for its stability and versatile chemistry in both research and industrial applications.

References

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