Ethylenebis triphenylphosphine palladium

Ethylene (tert-phosphine) complexes of zero-valent nickeP and platinum have been known for years. Analogous palladium complexes can be synthesized along the same lines as those reported for the nickel compounds, using ethoxy-diethylaluminum(III) as the reducing agent in the presence of ethylene. These palladium-ethylene complexes may serve as starting materials for oxidative addition reactions, since the ethylene ligand is loosely bonded.  

Inorganic Syntheses, Volume XVI Edited by Fred Basolo Copyright 1976 by McGraw-Hill, Inc. 

Stirring, 6.3 ml (5.3 g, 41 mmoles) of ethoxydiethylaluminum(III) in 30 ml of diethyl ether is added from the dropping funnel over a 15-min period. The resulting reaction mixture is then stirred for 24 hr at room temperature while it is kept saturated with ethylene. The reaction mixture is then cooled again to 0° for 2 hr (stirring is continued) to complete crystallization. By means of a siphon and a slight overpressure of argon, the contents of the flask are transferred onto a frit cooled to 0°, as depicted in Fig. 13. The precipitate is 

The purity can be checked conveniently by complexometric titration of palladium - after destruction of the complex with sulfuric and nitric acids and by volumetric determination of the ethylene upon displacement with triphenyl phosphite. Anal. Calcd. for C38Hs4P2Pd Pd, 16.1 C2H4, 4.26 C, 69.3 H, 5.2. Found Pd, 16.2 C2H4, 4.06 C, 68.9 H, 4.9. 

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Ethylenebis(triphenylphosphine)palladium, however, decomposes under this treatment with the formation of metallic palladium. For infrared data, see Table I. 

Ethylenebis( e/ /-phosphine)palladium(0) complexes are air-sensitive but can be kept for months, when dry and pure, under inert gas in a refrigerator. They are soluble in organic solvents like benzene and toluene palladium may precipitate from the solutions, especially that of the triphenylphosphine complex, unless they are saturated with ethylene. Therefore, the complexes may be crystallized from toluene-diethyl ether mixtures saturated with ethylene. 

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