Palladium chloride is a dark brown powder, hygroscopic (absorbs moisture from the air). It is incompatible with acids, aluminium, ammonia, magnesium, nitrates, zinc, heat, thiocyanates, and organic solvents. Thermal decomposition of palladium chloride may release chlorine, hydrogen chloride, and oxides of palladium. It is used as a catalyst, photographic, and electroplating reagent. Palladium and its alloys are used as catalysts in the (petro)chemical and, above all, in the automotive industries. Applications of palladium compounds for electronics and electrical technology include use in metallisation processes (thick film paste), electrical contacts and switching systems, in the synthesis of semiconducting metal-containing polymers in which the polypyrrole backbone has a conformational energy minimum and is nearly planar. Palladium chloride is a stable chemical substance and is incompatible with strong oxidising agents.
Palladium chloride is a weak oxidizing agent. Palladium chloride is reduced in solution by hydrogen or carbon monoxide to metallic palladium. . Decomposed at high temperatures to metallic palladium and chlorine.
The anhydrous salt is insoluble in H2O and dissolves in HCl with difficulty. The dihydrate forms red hygroscopic crystals that are readily reduced to Pd. Dissolve it in conc HCl through which dry Cl2 is bubbled. Filter this solution which contains H2PdCl4 and H2PdCl6 and on evaporation it yields a residue of pure PdCl2. [Grube in Handbook of Preparative Inorganic Chemistry (Ed Brauer) Academic Press Vol II p 1582 1965, Mozingo Org Synth Coll Vol III 685 1955.]
Air & Water Reactions
Deliquescent. Water soluble.
Dark brown crystals.
Palladium dichloride dissolves in HCl forming tetrachloropalladate ion,
The complex ion catalyzes various types of organic reactions including oxidation of ethylene to acetaldehyde in aqueous solution (the Wacker Process):
PdCl42¯+ C2H4 + H2O → CH3CHO + Pd + 2HCl + 2Cl¯
Palladium dichloride forms polymeric carbonyl complexes when the dry chloride is heated in a stream of carbon monoxide charged with methane vapor. Such complexes include [PdCl2(CO)n] and [PdCl(CO)2]n. The reaction also occurs in aqueous phase resulting in decolorization of the solution.
When H2S is passed through palladium dichloride solution, it yields a brown-black precipitate of palladium monosulfide, PdS.
When heated with sulfur at 450 to 500°C, palladium dichloride forms palladium disulfide, PdS2, a grey-black crystalline compound, insoluble in strong acids but soluble in aqua regia, and which converts to monosulfide, PdS, on heating at 600°C.
When ammonia gas is passed through an aqueous solution of PdCl2, the product is tetrammine palladium(II) chloride, Pd(NH4)2Cl2. The same product also is obtained in dry state by passing ammonia gas over anhydrous PdCl2.
The palladium powder is added to the reactor containing hydrochloric acid, with stirring, passing the air, an oxidation reaction is performed, generating palladium chloride solution, the solution is purified, filtered, concentrated by evaporation, cooling and crystallization, centrifugal separation, and dried to obtain a palladium chloride finished products.
Flash point data for Palladium chloride are not available. Palladium chloride is probably combustible.
Palladium dichloride is a starting material for preparing several palladium compounds. It also is used for detection of carbon monoxide. For such detection, a paper is soaked in very dilute solution of PdCl2 which is decolorized by CO, methane and other reducing substances. It also is used in toning and electroplating solutions and in photography for porcelain pictures.
Palladium chloride is a commonly used precious metal catalysts, molecular formula is PaCl2, the appearance is brown-red needle-like crystals or powder, easily deliquescence, the relative density is 4.0 (18 ℃), melting point is 500 ℃ (decomposition), soluble in water, ethanol, acetone and hydrogen bromide. Decomposition in ammonia chloride, potassium iodide, ammonia solution, and precipitation of palladium.
(1)used as the analysis reagents, such as determination of trace palladium, mercury, thallium, iodine, etc.
(2) palladium test strips is used to test carbon monoxide.
(3) also used to search for cracks of buried underground gas pipeline cracks, study of agricultural plant resources, preparation of palladium catalyst, electroplating watch parts and photography, and so on.
[Preparation method] by melting palladium dichloride hydrate, make it lost part of chloride to get Palladium chlorine finished products.
Figure 1 the molecular structure of Palladium chloride.