Dichloro(1,5-cyclooctadiene)palladium(II)
[CAS# 12107-56-1]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic palladium
• Name: Dichloro(1,5-cyclooctadiene)palladium(II)
• Synonyms: (cis,cis-1,5-Cyclooctadiene)palladium(II) chloride
• Molecular Formula: C₈H₁₂Cl₂Pd
• Molecular Weight: 285.51
• CAS Registry Number: 12107-56-1
• EC Number: 235-161-8
• SMILES: C1/C=CCC/C=CC1.Cl[Pd]Cl

Properties

• Melting point: 210 °C (dec.)
• Water solubility: insoluble

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
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	H302
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Flammable solids	Flam. Sol.	2	H228
Substances or mixtures corrosive to metals	Met. Corr.	1	H290

Discovery and Applications

Dichloro(1,5-cyclooctadiene)palladium(II), often abbreviated as PdCl₂(COD), is an organopalladium complex composed of a palladium(II) center coordinated to two chloride ligands and one 1,5-cyclooctadiene (COD) ligand. The COD ligand is a bidentate diene that coordinates through its two alkene groups, stabilizing the palladium center in a square planar geometry typical of d⁸ metal ions. The compound is usually a yellow to orange crystalline solid and is soluble in organic solvents such as dichloromethane, tetrahydrofuran, and chloroform.

This complex was first synthesized during the development of organometallic chemistry in the 20th century, when researchers sought stable palladium complexes with unsaturated hydrocarbons. The coordination of COD provides kinetic stability and modulates the reactivity of the palladium center, making PdCl₂(COD) a valuable precursor in catalysis and synthesis.

Dichloro(1,5-cyclooctadiene)palladium(II) is commonly prepared by the reaction of potassium tetrachloropalladate(II) (K₂PdCl₄) with 1,5-cyclooctadiene in aqueous or alcoholic solution under mild heating. The ligand exchange displaces two chloride ions, resulting in the formation of the chelated complex. The product can be isolated by filtration or crystallization.

The compound serves as a widely used precursor for palladium-catalyzed reactions, particularly in homogeneous catalysis. The COD ligand is readily displaced by other ligands such as phosphines, amines, or olefins, allowing the formation of tailored palladium complexes that are active catalysts for cross-coupling reactions (Suzuki, Heck, Sonogashira), allylic substitutions, and carbonylation reactions. Its solubility and stability facilitate handling and use in synthetic organic chemistry.

In addition to catalysis, PdCl₂(COD) is used in the synthesis of palladium-containing materials, coordination polymers, and as a starting point for the preparation of nanoparticles and functional materials for electronics and sensors.

Safety precautions are necessary when handling this compound due to the toxicity of palladium complexes. It may cause skin and respiratory irritation, and inhalation or ingestion should be avoided. Appropriate protective equipment, such as gloves and eye protection, and working in a well-ventilated area are recommended.

In summary, dichloro(1,5-cyclooctadiene)palladium(II) is a stable, square planar palladium(II) complex widely employed as a catalyst precursor and reagent in organometallic and synthetic chemistry. Its coordinated COD ligand facilitates ligand exchange and catalytic activity in numerous important transformations.

References

2020. Synthesis, characterization and antibacterial activity studies of new 2-pyrral-L-amino acid Schiff base palladium (II) complexes. Chemical Papers, 74(6).
DOI: 10.1007/s11696-019-00986-5

2019. Palladium nanoparticles supported on silica, alumina or titania: greener alternatives for Suzuki-Miyaura and other C-C coupling reactions. Environmental Chemistry Letters, 17(4).
DOI: 10.1007/s10311-019-00899-5

2018. Metal-catalyzed synthetic strategies toward coumarin derivatives. Chemistry of Heterocyclic Compounds, 54(3).
DOI: 10.1007/s10593-018-2262-6