Palladous chloride in preparation

Palladous chloride in preparation of hydrogenation catalyst, 46, 89 Paraformaldehyde, conversion to form aldoximc, 46,13 Pelargonyl fluoride 46, 6 1-Pentalenecaeboxylic acid, octa hydro-, 47,10... 

IMailfert 2 prepared palladium dioxide free from alkali by the action of ozone in the cold on palladous chloride in dilute alkaline solution. The product, however, contained traces of basic salt. The reaction probably takes place according to the following equation ... 

COCH3 - Preparation by isomerization of 3-allyl-2-hy-droxy-acetophenone using bis(benzonitrile)-palladous chloride in refluxing toluene (90%) [1897,3165],... 

The catalyst is previously prepared in an apparatus for catalytic hydrogenation, in which are placed 0.5 g. of palladous chloride, 3.0 g. of Norite, and 20 ml. of distilled water. The bottle is swept out with hydrogen and then shaken with hydrogen for 2-3 hours at 2-3 atmospheres (40 lb.) pressure. The palladium on carbon is collected on a Biichner funnel, washed with five 50-ml. portions of distilled water, then with five 50-ml. portions of 95% ethanol, and finally twice with ether. Upon drying, about 3 g. of the catalyst is obtained. It is stored in a vacuum desiccator over solid sodium hydroxide. If the reduction of the chloro-lepidine does not proceed normally, the used catalyst should be removed by suction filtration and a fresh 3-g. portion of catalyst added. Failure of the reduction step is usually due to an inactive catalyst or to impurities in the acetic acid or chlorolepidine. The palladium catalysts, prepared as described elsewhere in this volume, are presumably also satisfactory for the reduction of 2-chlorolepidine (p. 77). 

A substitute may be prepared thus 0 05 gram palladous chloride is placed in a special shaking flask with 50 c.c, of 50 per cent, alcohol and 1 or 2 c c. of 1 per cent, aqueous solution of gum-arabic, the weight of gum being about one-fourth the weight of the palladous chloride. On shaking this mixture in an atmosphere of hydrogen the chloride is reduced with formation of a black solution of colloidal platinum, which is rendered stable by the small quantity of gum present. 

The catalyst is prepared by suspending 5 kg of catalyst grade charcoal in 200 liters of water, in a pressure vessei, and adding thereto 25 liters of 4% (as Pd metal) aqueous palladous chloride. Air is displaced from the vessel and then hydrogen is passed into the aqueous mixture at a pressure of 3 to 5 psi, while stirring, until no further absorption is noted and the chloride is completely reduced to metal. 

Palladous oxide,3/ PdO, may be prepared by the fusion of palladous chloride with sodium nitrate, and is an effective catalyst in hydrogenation, the most active form being produced when the fusion temperature is 600°,... 

A convenient method of preparing the salt consists in adding potassium iodide to a slight excess of palladous chloride solution,1 when it is precipitated as a black mass, readily soluble in excess of potassium iodide. When dried in air it contains one molecule of water heated to 300-360° C. it decomposes, evolving iodine. In order to remove the last traces of iodine, however, it is necessary to heat to redness in a current of hydrogen. 

Calcium carbonate is prepared by precipitation with sodium carbonate from a hot aqueous calcium chloride solution. Fifty grams of the washed calcium carbonate is suspended in water, and an aqueous solution containing 1 g. of palladous chloride is added. The mixture is warmed gently until the color of the palladous chloride is gone from the aqueous solution, indicating conversion of the palladous chloride to the insoluble hydroxide. The solid material is washed by decantation a few times with distilled water, followed by suction filtration, and then washed until the wash water is free of chloride ion. No more wash water than necessary should be used since some of the palladous hydroxide may be lost by washing with large volumes of water. 

Palladium chlorophthalocyanine is formed when phthalonitrile is heated with palladous chloride. Like other nuclear halogen-substituted phthalocyanines, it will not sublime (11, 278). The unsubstituted derivative may be prepared by the dehydrogenation of tetracyclohexenotetrazaporphin with palladium black (113), or by the action of palladous chloride on lithium phthalocyanine in absolute alcohol (11). It is also possible to prepare the complex by dissolving palladium black in boiling phthalonitrile, a really remarkable reaction. 

Palladous chloride/sodium tetrahydridoborate Preferential stereospecific ring hydrogenation with catalyst prepared in situ... 

Butyrolactones are prepared by intramolecular reaction of haloallylic 2-alkynoates. The a-chloromethylenebutyrolactone 301 is prepared by the intramolecular reaction of300[150,151]. 4 -Hydroxy-2 -alkenyl 2-alkynoates can be used instead of haloallylic 2-alkynoates, and in this reaction, Pd(II) is regenerated by elimination of the hydroxy group[152]. As a related reaction, the q-(chloromethylene)-7-butyrolactone 304 is obtained from the cinnamyl 2-alkynoate 302 in the presence of LiCl and CuCbflSS]. Isohinokinin (305) has been synthesized by this reaction[l 54]. The reaction is explained by chloro-palladation of the triple bond, followed by intramolecular alkene insertion to generate the alkylpalladium chloride 303. Then PdCb is regenerated by attack of CuCb on the alkylpalladium bond as a key step in the catalytic reaction. 

The palladized strontium carbonate is prepared as follows. Suspend 33 g. of strontium carbonate in 350 ml. of water at 70°. Add 2 g. of palladium chloride dissolved in 10 ml. of concentrated hydrochloric acid, and stir the mixture at 70° for 15 minutes. Filter the mixture, wash the product thoroughly with hot water, and dry the product at 110°. 

The bromide, [Pd(NH3)4]Br2, is prepared like the chloride from palladous bromide and excess of ammonia. It crystallises in almost colourless rhombic prisms which are soluble in water and stable.in air. 

---