Disodium tetrachloropalladate
[CAS# 13820-53-6]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Inorganic ammonium salt
• Name: Disodium tetrachloropalladate
• Synonyms: Sodium tetrachloropalladate(II)
• Molecular Formula: Na₂PdCl₄
• Molecular Weight: 294.21
• CAS Registry Number: 13820-53-6
• EC Number: 237-502-6
• SMILES: [Na+].[Na+].Cl[Pd-2](Cl)(Cl)Cl

Properties

• Water solubility: SOLUBLE

Safety Data

• Hazard Symbols: GHS05;GHS07;GHS09 Danger
• Risk Statements: H290-H302-H317-H318-H319-H400-H410
• Safety Statements: P234-P261-P264-P264+P265-P270-P272-P273-P280-P301+P317-P302+P352-P305+P351+P338-P305+P354+P338-P317-P321-P330-P333+P317-P337+P317-P362+P364-P390-P391-P406-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Skin sensitization	Skin Sens.	1A	H317
Serious eye damage	Eye Dam.	1	H318
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315

Discovery and Applications

Disodium tetrachloropalladate is an inorganic coordination compound with the chemical formula Na₂[PdCl₄]. It consists of two sodium cations (Na⁺) and one tetrachloropalladate(II) anion [PdCl₄]^2–, where palladium is in the +2 oxidation state coordinated in a square planar geometry to four chloride ligands. This compound is an important and widely used palladium salt, especially as a precursor in various catalytic and synthetic applications in chemistry.

The synthesis of disodium tetrachloropalladate commonly involves the reaction of palladium(II) chloride with sodium chloride in aqueous solution. Under appropriate conditions, palladium chloride dissolves and forms the tetrachloropalladate complex ion by coordination of four chloride ions around the Pd(II) center. Subsequent addition of sodium ions from sodium chloride or sodium hydroxide leads to precipitation or crystallization of the disodium salt. The compound can be isolated as a yellow to orange crystalline solid and purified by recrystallization from water or suitable solvents.

Structurally, the tetrachloropalladate anion in Na₂[PdCl₄] exhibits a typical square planar coordination geometry, which is characteristic of d⁸ palladium(II) complexes. The palladium ion is centrally bound to four chloride ligands arranged symmetrically in a planar fashion. The sodium cations serve as charge-balancing counterions, and in the solid state, the ions arrange themselves in a crystalline lattice stabilized by ionic interactions.

Disodium tetrachloropalladate serves as a valuable palladium source in homogeneous and heterogeneous catalysis. It is often used as a precursor for the preparation of various palladium complexes and catalysts employed in cross-coupling reactions such as Suzuki-Miyaura, Heck, and Stille couplings. These palladium-catalyzed transformations are fundamental in organic synthesis, enabling the formation of carbon–carbon and carbon–heteroatom bonds critical for the construction of pharmaceuticals, agrochemicals, and advanced materials.

Due to its water solubility, disodium tetrachloropalladate facilitates easy handling and use in aqueous or mixed solvent systems. It can be converted into catalytically active species upon ligand exchange or reduction under reaction conditions. The tetrachloropalladate ion acts as a stable and convenient palladium reservoir that can release palladium centers in situ for catalytic cycles.

Besides its catalytic applications, disodium tetrachloropalladate finds use in electrochemical processes and in the preparation of palladium-containing materials. It can serve as a precursor for depositing palladium films on electrodes or substrates through electroplating or chemical reduction. These palladium coatings improve conductivity, catalytic activity, and corrosion resistance in electronic components and sensors.

The compound is also used in coordination chemistry as a starting material to synthesize a variety of palladium complexes by ligand substitution reactions. Replacement of chloride ligands with phosphines, amines, or other donor ligands allows fine-tuning of the electronic and steric environment around palladium, which is crucial for optimizing catalytic performance.

Handling disodium tetrachloropalladate requires appropriate safety precautions because palladium compounds can be hazardous if inhaled, ingested, or if they come in contact with skin. The compound is generally stable under normal laboratory conditions but should be stored away from strong reducing agents and moisture to prevent decomposition or hydrolysis.

Environmental considerations are important in the use and disposal of palladium salts such as disodium tetrachloropalladate. Palladium is a valuable metal and recycling of palladium-containing materials is widely practiced to reduce waste and minimize environmental impact. Proper treatment of waste streams containing palladium is essential to avoid contamination.

Research involving disodium tetrachloropalladate continues to expand, focusing on improving catalytic processes and developing new palladium-based materials. Modifications of reaction conditions, ligands, and supports aim to enhance catalyst efficiency, selectivity, and lifetime, contributing to more sustainable and cost-effective chemical manufacturing.

In summary, disodium tetrachloropalladate is a palladium(II) coordination compound composed of sodium cations and a square planar tetrachloropalladate anion. It is synthesized by coordination of chloride ions to palladium in the presence of sodium salts and is widely used as a palladium source in catalysis, material preparation, and coordination chemistry. Its solubility, stability, and reactivity make it a versatile and valuable reagent in chemical and industrial applications, while proper handling and recycling practices ensure safety and environmental responsibility.

References

2022. Low-dimensional compounds containing bioactive ligands. Part XVII: Synthesis, structural, spectral and biological properties of hybrid organic-inorganic complexes based on [PdCl4]2− with derivatives of 8-hydroxyquinolinium. Journal of Inorganic Biochemistry, 228.
DOI: 10.1016/j.jinorgbio.2021.111697

2007. Palladate Salts from Chiral Pyridinium Ionic Liquids: Synthesis and Crystal Structures. Molecules (Basel, Switzerland), 12(8).
DOI: 10.3390/12081940

2007. Sodium tetrachloropalladate (Na2[PdCl4]) as an improved test salt for palladium allergy patch testing. Contact Dermatitis, 57(6).
DOI: 10.1111/j.1600-0536.2007.01259.x