Preparation of Palladium Catalyst

Powdered sodium borohydride (0.19 g, 5 mmol) is added portionwise at room temperature over a period of 5-10 minutes to a stirred suspension of 0.443 g (2.5 mmol) of powdered palladium chloride in 40 ml of absolute methanol. Stirring is continued until the evolution of hydrogen has ceased (about 20 minutes). The solvent is decanted from the black settled catalyst which is washed twice or three times with a solvent to be used in hydrogenations. 

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Sodium azide, reaction with l butyl chloroacetate, 46, 47 reaction with diazomum salt from o amino-f> -ni trobiphcny L, 46, 86 Sodium chlorodifluoroacetate, 47, SO reaction with tnphenylphosphme and benzaldehyde, 47, SO Sodium ethoxide, 46, 2S reaction with diethyl succinate, 46,2S Sodium formate as reducing agent in preparation of palladium catalyst, 46, 90... 

Sodium formate as reducing agent in preparation of palladium catalyst, 46,90... 

Among the important reagents for which preparative procedures are given are 2,2 -bipyridine (by nickel directed and catalyzed dehydrogenation of pyridine p. 5), formamidine acetate (p. 39), phenyltrichloromethylmercury (p. 98), and trimethyl- and triethyloxonium fluoroborate (pp. 120, 113). The preparation of palladium catalyst ( Lindlar ) for the selective reduction of acetylenes is described (p. 89), as is the use of di-phenyliodonium-2-carboxylate, as a precursor of benzyne in the synthesis of 1,2,3,4-tetraphenylnaphthalene (p. 107). 

A size-selective synthesis of nanostructured transition metal clusters (Pd, Ni) has been reported166, as has the preparation of colloidal palladium in organic solvents167, the latter of which is an active and stable catalyst for selective hydrogenation. The use of microwaves in the preparation of palladium catalysts on alumina and silica resulted in hydrogenation catalysts with improved crystallite size and activity168. 

Other possible carriers for catalysts are asbestos, pumice, kieselgur, silica gel, silica, active charcoal, and oxides, carbonates, and sulfates of magnesium, calcium, barium, zinc, aluminum, iron, chromium, and zirconium. Details for the preparation of palladium catalysts on barium sulfate have been recorded by Mozingo.137... 

The preparation of palladium catalysts from polyethyleneimine-silicagel composites was reported [65]. PEI is first absorbed on silica beads or silica gel. Then the absorbed... 

The preparation of palladium catalysts supported on carbon fibrils. 

Hong et al. [24] reported the preparation of palladium catalysts D1-D4 containing the chiral ADC ligands (Fig. 11.3) via the oxidative addition of several chloroamidinium salts to a palladium source. 

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