Bis(acetonitrile)palladium(II) chloride
[CAS# 14592-56-4]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic palladium
• Name: Bis(acetonitrile)palladium(II) chloride
• Synonyms: Bis(acetonitrile)dichloropalladium(II)
• Molecular Formula: C₄H₆Cl₂N₂Pd
• Molecular Weight: 259.43
• CAS Registry Number: 14592-56-4
• EC Number: 238-637-3
• SMILES: CC#N.CC#N.Cl[Pd]Cl

Properties

• Melting point: 300 °C
• Water solubility: insoluble

Safety Data

• Hazard Symbols: GHS06;GHS07 Danger
• Risk Statements: H301-H302-H311-H312-H315-H319-H331-H332-H335
• Safety Statements: P261-P262-P264-P264+P265-P270-P271-P280-P301+P316-P301+P317-P302+P352-P304+P340-P305+P351+P338-P316-P317-P319-P321-P330-P332+P317-P337+P317-P361+P364-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	3	H331
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	3	H301
Acute toxicity	Acute Tox.	4	H302
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Skin sensitization	Skin Sens.	1	H317
Flammable solids	Flam. Sol.	2	H228

• Transport Information: UN 3077

Discovery and Applications

Bis(acetonitrile)palladium(II) chloride, with the chemical formula [PdCl₂(CH₃CN)₂], is a square-planar palladium(II) coordination complex composed of one palladium ion coordinated by two chloride ligands and two acetonitrile ligands. It is typically isolated as a yellow or pale orange crystalline solid and is soluble in organic solvents such as acetonitrile, dichloromethane, and acetone.

The complex is prepared by dissolving palladium(II) chloride in an excess of acetonitrile, often under reflux. The acetonitrile acts both as solvent and ligand, facilitating the replacement of bridging chlorides in polymeric PdCl₂ with monodentate CH₃CN ligands. The resulting compound features monomeric square-planar geometry around the d⁸ palladium center, with the ligands arranged cis to one another in the coordination sphere.

The acetonitrile ligands are relatively labile and readily displaced by stronger donor ligands such as phosphines, isocyanides, and N-heterocyclic carbenes. This ligand exchange property makes [PdCl₂(CH₃CN)₂] a highly valuable precursor in coordination and organometallic chemistry, where it serves as a convenient and soluble source of palladium(II) for the synthesis of a wide range of complexes.

In catalysis, bis(acetonitrile)palladium(II) chloride is employed as a pre-catalyst in many palladium-mediated transformations. It can be used in the preparation of active catalysts for carbon–carbon bond-forming reactions such as Suzuki–Miyaura, Heck, and Sonogashira couplings. The presence of weakly bound acetonitrile ligands allows for rapid activation under reaction conditions, often enabling in situ formation of catalytically active species with added ligands or substrates.

The complex has also been used in the synthesis of luminescent and redox-active palladium complexes for use in materials chemistry. It serves as a starting material in the preparation of mono- and polynuclear palladium compounds featuring tailored ligand environments, which can be used in molecular electronics, sensing, or as building blocks for supramolecular assemblies.

From an analytical perspective, [PdCl₂(CH₃CN)₂] has been used as a palladium standard in solution chemistry and as a reagent in studies of ligand substitution kinetics and mechanisms. Its simple structure and well-defined reactivity profile make it an ideal model system for investigating fundamental aspects of square-planar palladium chemistry.

The handling and storage of bis(acetonitrile)palladium(II) chloride require standard precautions. Although it is stable under normal conditions, prolonged exposure to light or air can cause slow degradation. It should be stored in a dry, cool environment, preferably under an inert atmosphere if purity is to be maintained over time. Like many palladium compounds, it may cause skin and respiratory irritation and should be handled with appropriate protective equipment.

In summary, bis(acetonitrile)palladium(II) chloride is a square-planar palladium(II) complex with labile acetonitrile ligands that confer high utility in synthetic chemistry. It is used as a precursor in the formation of diverse palladium complexes and serves as an effective starting material in the development of palladium catalysts for cross-coupling and other organometallic reactions. Its solubility, ligand exchangeability, and air stability make it a valuable compound in both academic and industrial settings.

References

2023. Synthesis of new π-stabilized organophosphorane bis-ylide ligands. Russian Chemical Bulletin, 72(6).
DOI: 10.1007/s11172-023-3919-6

2021. Features of the Liquid-Phase Oxidation of Alkenes to Carbonyl Compounds in the Presence of Palladium Compounds. Catalysis in Industry, 13(3).
DOI: 10.1134/s2070050421030041

2021. Palladium Nanoparticles from Different Reducing Systems as Heck Catalysts. Catalysis Letters, 151(12).
DOI: 10.1007/s10562-021-03613-9