Synthesis of Palladium tetrakis(triphenylphosphine)

Chemicals Used

Palladium dichloride (1g, 1 equiv.) Triphenylphosphine (7.4g, 5 equiv.) Dimethylsulphoxide (distilled, 12mL/mmol, 68mL) Hydrazine hydrate (1.1mL, 4 equiv.)

Procedure

Palladium chloride is placed in a 3 necked round bottomed flask which is fitted with a thermometer and a filter stick attached to a second inverted 3 necked round bottomed flask. DMSO is added, followed by triphenylphosphine. The mixture is heated to 140C using an oil bath with stirring in order to dissolve all the solid (a small amount of solid does not seem to dissolve). The oil bath is then removed and the mixture stirred for a further 15 minutes. Hydrazine hydrate is rapidly added causing evolution of nitrogen. The resulting dark solution is immediately cooled with a water bath until crystallisation begins to occur (~125C) at which point it is allowed to cool without external cooling. Once the mixture has reached room temperature, the apparatus is inverted in order to filter and the solid is washed succesively with absolute ethanol (2 x 10 mL) and dry ether (2 x 10 mL) (this is achieved by adding the solvent from a syringe through a side arm). The resulting yellow solid is then dried under vacuum for 3-4 hours.

Note:

All glassware should be oven or flame dried prior to use, and the entire procedure should be carried out under nitrogen. If care is taken in the preparation, the material should have a bench life of many months (>8), and should be stored under nitrogen in a freezer. 5-6g of catalyst is atttainable starting from 1g palladium dichloride. Analysis of the compound is not really required; if it's a yellow solid, it should work (although melting point determination should give a decomposition point of 115C, but this has not been checked)! On exposure to air, the material will slowly turn orange, this seems to be a result of reaction with water.

Reference:

D.R Coulson, Inorganic Syntheses XIII, p.121