Палладий(II) хлорид

Описание

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.
[Uses]
(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.

Химические свойства

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.

Физические свойства

l Properties Red rhombohedral crystal; hygroscopic; density 4.0g/cm³; melts at 679°C; dissolves slowly in water; also soluble in ethanol and acetone; dissolves rapidly in hydrochloric acid.

Использование

Palladium chloride is used in photography; toning solutions; electroplating parts of docks and watches; detecting carbon monoxide leaks in buried gas pipes; manufacture of indelible ink; preparation of metal for use as a catalyst; catalyst in jewelry; in dental alloys.

Подготовка

Palladium dichloride is prepared by dissolving palladium metal in aqua regia or hydrochloric acid in the presence of chlorine. Alternatively, it may be prepared by heating palladium sponge with chlorine gas at 500°C.

Методы производства

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.
Pd+2HCl+0.5O2→PdCl2+H2O

Реакции

Palladium dichloride dissolves in HCl forming tetrachloropalladate ion,
PdCl2+2Cl¯→ [PdCl4]2¯
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.

Общее описание

Dark brown crystals.

Реакции воздуха и воды

Deliquescent. Water soluble.

Профиль реактивности

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.

Пожароопасность

Flash point data for Palladium chloride are not available. Palladium chloride is probably combustible.

Профиль безопасности

Poison by intraperitoneat, intravenous, and intratracheal routes. Moderately toxic by ingestion. Experimental reproductive effects. A skin irritant. Questionable carcinogen with experimental carcinogenic data. Human mutation data reported. When heated to decomposition it emits highly toxic fumes of Cl-. See also PALLADIUM

Методы очистки

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.]