Iridium(III) acetylacetonate
[CAS# 15635-87-7]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic iridium
• Name: Iridium(III) acetylacetonate
• Synonyms: Tris(pentane-2,4-dionato-O,O')iridium
• Molecular Formula: C₁₅H₂₁IrO₆
• Molecular Weight: 489.54
• CAS Registry Number: 15635-87-7
• EC Number: 239-711-8
• SMILES: CC(=O)C=C(C)O[Ir](OC(C)=C/C(C)=O)OC(C)=C/C(C)=O

Properties

• Melting point: 269-271 °C (Expl.)

Safety Data

• Hazard Symbols: GHS07;GHS08 Warning
• Risk Statements: H302-H312-H315-H319-H332-H335-H351
• Safety Statements: P203-P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P318-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H312
Specific target organ toxicity - single exposure	STOT SE	3	H335
Carcinogenicity	Carc.	2	H351
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Flammable solids	Flam. Sol.	2	H228

Discovery and Applications

Iridium(III) acetylacetonate, commonly represented as Ir(acac)₃, is a coordination complex consisting of an iridium ion in the +3 oxidation state chelated by three acetylacetonate ligands. Each acetylacetonate (acac) ligand is a bidentate ligand that coordinates to the iridium center through two oxygen atoms, forming stable five-membered chelate rings. The complex typically exists as a dark green or brown crystalline solid and is soluble in various organic solvents such as chloroform, benzene, and toluene.

The synthesis of Ir(acac)₃ usually involves the reaction of hydrated iridium(III) chloride or other iridium(III) salts with acetylacetone in the presence of a base, which facilitates the deprotonation of acetylacetone to generate the acetylacetonate anion. This anion then coordinates to the iridium center, replacing chloride or other ligands. The reaction is often carried out in refluxing organic solvents to improve yield and purity. The resulting Ir(acac)₃ complex can be isolated by filtration and recrystallization.

Structurally, Ir(acac)₃ features an octahedral geometry around the iridium(III) center, with the three acac ligands arranged to satisfy the six coordination sites. This arrangement imparts high stability to the complex due to the chelate effect and strong metal-oxygen bonding. The complex is low-spin d⁶, diamagnetic, and its electronic and steric properties make it an important compound in organometallic chemistry.

Iridium(III) acetylacetonate serves as a versatile precursor in the synthesis of a broad range of iridium complexes used in catalysis, materials science, and photophysics. It is often employed in homogeneous catalytic processes such as hydrogenation, C–H activation, and transfer hydrogenation reactions. Its ability to undergo ligand substitution allows for the preparation of complexes with phosphines, N-heterocyclic carbenes, or other ligands tailored to specific catalytic applications.

In materials chemistry, Ir(acac)₃ is used as a precursor for the fabrication of iridium-containing thin films and nanoparticles through chemical vapor deposition, thermal decomposition, or sol-gel methods. These materials are utilized in electronics, sensors, and as catalysts for oxygen evolution reactions in energy conversion devices.

The complex is also studied for its photophysical properties, including luminescence and redox behavior, making it useful in the design of light-emitting devices and sensors. Its stable coordination environment and electronic structure facilitate investigations into fundamental aspects of iridium chemistry.

Iridium(III) acetylacetonate should be handled with appropriate safety measures, including use of gloves and eye protection. It is generally stable under normal laboratory conditions but should be stored in a dry, cool place to prevent degradation. Exposure to strong acids, bases, or reducing agents may alter the complex.

In summary, iridium(III) acetylacetonate is a stable, octahedral iridium complex coordinated by three acetylacetonate ligands. It is widely used as a precursor in catalytic, materials, and photophysical chemistry due to its stability, solubility, and versatile reactivity.

References

2024. Efficient synthesis of IrPtPdNi/GO nanocatalysts for superior performance in water electrolysis. Nano Research, 17(8).
DOI: 10.1007/s12274-024-6900-6

2022. Breaking the activity limitation of iridium single-atom catalyst in hydrogenation of quinoline with synergistic nanoparticles catalysis. Nano Research, 15(6).
DOI: 10.1007/s12274-022-4235-4

1999. Synthesis and crystal structure determination of iridium(III) acetylacetonate and its Br-and I-substituted analogs. Journal of Structural Chemistry, 40(3).
DOI: 10.1007/bf02903657