What are the compounds of palladium?

Palladium (Pd) is a precious metal whose compounds, such as palladium(II) oxide (PdO), palladium(II) chloride (PdCl₂), palladium(II) acetate (Pd(OAc)₂), and palladium(II) nitrate (Pd(NO₃)₂), are widely used in catalysis, the electronics industry, and chemical synthesis. The main palladium compounds include the following categories：

1. Palladium oxides

Palladium(II) oxide (PdO)

Brown or black powder, the main oxide produced by heating palladium in air.

Uses: Commonly used as catalysts or precursors to catalysts.

2. Palladium halides

Palladium dichloride (PdCl₂)

Yellow powder, often dissolved in water to form [PdCl₄]²-complexes.

Uses: Used in the catalysis of organic reactions (e.g. cross-coupling reactions) and in the preparation of materials.

Tetrachloropalladium acid (H₂PdCl₄)

A complex formed by palladium and hydrochloric acid with good water solubility.

Uses: Precious metal plating and catalyst preparation.

Palladium bromide (PdBr₂) and palladium iodide (PdI₂)

Similar to palladium dichloride, solubility and stability vary depending on the halogen.

Uses: Catalysts and chemical synthesis.

3. Palladium complexes

Palladium acetylacetonate (Pd(acac)₂)

Yellow solid, a stable complex.

Uses: Catalyst for organic reactions, especially excellent in coupling reactions.

Bis(triphenylphosphine)dichloropalladium (Pd(PPh₃)₂Cl₂)

Commonly used as homogeneous catalysts, especially for cross-coupling reactions (e.g. Suzuki, Heck and Stille reactions).

Palladium acetate (Pd(OAc)₂)

Soluble in polar solvents, good stability.

Uses: Common palladium catalyst precursor for carbon-carbon and carbon-heteroatom bond forming reactions.

4. Nitrates of palladium

Palladium(II) nitrate (Pd(NO₃)₂)

White or light yellow crystal, soluble in water.

Uses: Electroplating, catalyst preparation, gas adsorption materials.

5. Palladium cyanides and hydroxides

Palladium cyanide (Pd(CN)₂)

White solid, insoluble in water.

Uses: Precious metal recovery and electroplating industry.

Palladium hydroxide (Pd(OH)₂)

Light brown or black powder, often used as an intermediate before catalyst preparation.

6. Organic compounds of palladium

Bis(vinylpalladium) compounds (Pd(allyl)₂)

Used in organic reactions, especially carbon-carbon bond forming reactions.

7. Palladium sulfides

Palladium sulfide (PdS) and palladium disulfide (PdS₂)

Uses: Research on high-temperature catalysts or semiconductor materials.

Palladium compounds are important in industry and research due to their chemical stability and high catalytic activity. The specific choice of compounds needs to be determined according to the application scenario.