Chloropalladous acid

Pallado-. palladous, palladium (II). -chlorid, n. palladous chloride, palladium(II) chloride, -chlorwasserstoffsaure, /. chloropalladous acid, chloropalladic(II) acid, -hydro d, n. palladous hydroxide, palladium(II) hydroxide. 

Palladous chloride (1 48 g, 0 0083 mole) (Note 1) is placed in a 10-ml. Erlenmeyer flask, and 3.6 ml. (0 043 mole) of 37% hydrochloric acid is added. The flask is shaken at about 30° until the palladous chloride is dissolved. The chloropalladous acid solution is transferred to a 150-ml. beaker with 45 ml of... 

In principle, the same methods used for the preparation of platinum catalysts may be applied for palladium catalysts. When palladium chloride is used as a starting material, it is usually dissolved into an aqueous solution as chloropalladic acid by adding hydrochloric acid prior to reduction or formation of precipitates. Unsupported and supported palladium catalysts have been prepared by reduction of palladium salts with alkaline formaldehyde,139 168 sodium formate,169 hydrazine,150 hydrogen,170,171 sodium borohydride,146,172 or sodium hydride-t-AmOH,173 or by reduction of palladium hydroxide174,175 or palladium oxide176 with hydrogen. 

Lead-Poisoned Pd-CaCQs (Lindlar Catalyst))82 Palladium chloride (1.48 g, 0.0083 mol) is placed in a 10-ml Erlenmeyer flask, and 3.6 ml (0.043 mol) of 37% hydrochloric acid is added. The flask is shaken at about 30°C until the palladium chloride is dissolved. The chloropalladic acid solution is transferred to a 150-ml beaker with 45 ml of distilled water. The pH of the solution is brought to 4.0-4.5 by slow addition of aqueous 3M sodium hydroxide. The solution is diluted to approximately 100 ml and placed in a 200- or 250-ml three-necked, round-bottomed flask equipped with a mechanical stirrer and a thermometer. Precipitated calcium carbonate (18 g) is added. The well-stirred suspension is heated to 75-85°C and held... 

The principal compounds of palladium are the salts of chloropalladous acid, H2PdCl4, and chloropalladic acid, H2PdCl6. The chloropalladite ion PdCl4, is a planar ion, consisting of the palladium atom with four coplanar chlorine atoms arranged about it at the corners of a square. The chloropalladate ion, PdCle, is an octahedral covalent complex ion. 

More simple, but so far of less general use, is the formation of isocoumarins by cyclization of o-alkenyl-benzoic acids [(159)->(160)], using lithium tetra-chloropalladate in aqueous dioxan at room temperature/" "... 

In 2009, Li et al. reported a palladium-catalyzed intramolecular carboesterifica-tion of unactivated olefins under mild conditions [94] (Scheme 6.70). The authors envisioned that chloropalladation of a propiolic acid could generate a palladium-carboxylate intermediate 264. Subsequent iyn-oxopalladation would afford a palladacycle intermediate 265, followed by reductive elimination to produce the final products, 263. The active Pd(II) catalyst was regenerated by oxidation of the Pd(0) with CuCl. This reaction could proceed efficiently in the presence of moisture and air at low catalyst loadings. 

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