Bis(benzonitrile)palladium chloride
[CAS# 14220-64-5]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic palladium
• Name: Bis(benzonitrile)palladium chloride
• Synonyms: Bis(benzonitrile)palladium(II) chloride
• Molecular Formula: C₁₄H₁₀Cl₂N₂Pd
• Molecular Weight: 383.57
• CAS Registry Number: 14220-64-5
• EC Number: 238-085-3
• SMILES: C1=CC=C(C=C1)C#N.C1=CC=C(C=C1)C#N.Cl[Pd]Cl

Properties

• Melting point: 131 °C (Expl.)
• Solubility: Soluble acetone, chloroform (Expl.)

Safety Data

• Hazard Symbols: GHS06;GHS07 Danger
• Risk Statements: H301-H302-H311-H312-H315-H317-H319-H330-H331-H332-H413
• Safety Statements: P260-P261-P262-P264-P264+P265-P270-P271-P272-P273-P280-P284-P301+P316-P301+P317-P302+P352-P304+P340-P305+P351+P338-P316-P317-P320-P321-P330-P332+P317-P333+P317-P337+P317-P361+P364-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	3	H301
Acute toxicity	Acute Tox.	3	H331
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H332
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	3	H311
Skin sensitization	Skin Sens.	1	H317

Discovery and Applications

Bis(benzonitrile)palladium chloride is a coordination complex with the chemical formula PdCl₂(PhCN)₂, where PhCN represents benzonitrile (C₆H₅CN). In this complex, a palladium(II) center is coordinated by two chloride ligands and two benzonitrile molecules, forming a square planar geometry that is characteristic of d⁸ palladium(II) compounds. This compound is typically obtained as a yellow or pale orange crystalline solid that is moderately soluble in organic solvents such as dichloromethane and acetonitrile.

The preparation of bis(benzonitrile)palladium chloride generally involves dissolving palladium(II) chloride in benzonitrile under heating. Benzonitrile acts both as solvent and ligand in this process. As the palladium chloride dissolves, benzonitrile molecules coordinate to the metal center, displacing water or other ligands. The resulting PdCl₂(PhCN)₂ complex can be isolated by cooling and recrystallization. It is air-stable and can be stored for extended periods under ambient conditions.

Structurally, the palladium ion is situated in a square planar environment formed by two cis-positioned chloride ions and two benzonitrile ligands. The nitrile groups coordinate through the lone pair on the nitrogen atom, forming relatively labile Pd–N bonds. The lability of these ligands is a key feature of the complex, allowing for their easy displacement by stronger or more reactive ligands.

Because of this ligand lability, bis(benzonitrile)palladium chloride is widely used as a palladium source and catalyst precursor in organometallic chemistry. It serves as a soluble and easily handled palladium(II) compound for introducing palladium into catalytic systems. In many catalytic cycles, the benzonitrile ligands are readily replaced by phosphines, carbenes, or other ligands, generating active species for cross-coupling reactions such as Suzuki–Miyaura, Heck, and Stille couplings. These reactions are fundamental in the synthesis of complex organic molecules, including pharmaceuticals, agrochemicals, and polymers.

In addition to catalytic uses, PdCl₂(PhCN)₂ is employed in the synthesis of other palladium complexes. Its solubility and ligand exchange properties make it a convenient starting material for preparing a wide range of Pd(II) species. Ligand substitution with phosphines, bipyridines, or other donors provides access to complexes with finely tuned electronic and steric environments.

The compound is also of interest in fundamental research on palladium coordination chemistry. Studies on the kinetics and thermodynamics of ligand exchange involving PdCl₂(PhCN)₂ have provided insight into the behavior of palladium(II) in solution and the mechanisms of catalytic transformations.

From a safety standpoint, bis(benzonitrile)palladium chloride should be handled using standard laboratory precautions. Although it is stable under air and moisture, the compound can be harmful if ingested or inhaled, and it may cause skin or eye irritation. Palladium compounds should be handled with appropriate protective equipment and waste should be disposed of in accordance with environmental regulations.

In summary, bis(benzonitrile)palladium chloride is a square planar Pd(II) complex featuring two chloride ligands and two benzonitrile ligands. It is synthesized by dissolving palladium chloride in benzonitrile and is widely used as a catalyst precursor and starting material for other palladium complexes. Its ligand lability and solubility make it a valuable reagent in synthetic and catalytic chemistry.

References

2021. NOVEL PALLADIUM(II) COMPLEXES OF PYRAZOLE-CONTAINING SCHIFF BASE LIGANDS: SYNTHESIS, STRUCTURAL CHARACTERIZATION, AND CYTOTOXICITY OF THE PALLADIUM(II) COMPLEXES OF 2-{1-[2-(1,3-DIMETHYL-4-NITRO-1H-PYRAZOL-5-YL) HYDRAZONO]ETHYL} PYRIDINE (APHP) AND ITS ANALOGUE 2-{1-[2-(1,3-DIMETHYL-4-NITRO- 1H-PYRAZOL-5-YL)HYDRAZONO]METHYL} PYRIDINE (PCHP). Journal of Structural Chemistry, 62(7).
DOI: 10.1134/s0022476621070167

2019. Synthesis and Structure of Chloro Complex of Palladium(II) with {[6-Amino-2-(butylsulfanyl)pyrimidin-4-yl]oxy}acetic Acid. Russian Journal of General Chemistry, 89(9).
DOI: 10.1134/s1070363219090135

2020. Palladium (II) Complexes Containing 2-Phenylpyridine Derivatives: Synthesis, Molecular Structures, and Catalytic Activity for Suzuki-Miyaura Cross-Coupling Reactions. Journal of Structural Chemistry, 61(3).
DOI: 10.1134/s0022476620030130