Synthesis of the complexes [PdCIR(cod)] (R equals benzyl, ethyl; cod equals 1,5-cyclooctadiene). beta-elimination from [PdClEt(cod)] to give the eta(1),eta(2), and eta(3) isomers of [Pd-2(mu-Cl)(2)(C8H13)(2)]

Treatment of [PdCl2(cod)] with tetrabenzyltin gives the benzylpalladium complex [PdCl(CH(2)Ph)(cod)] (cod = 1,5-cyclooctadiene), 1a, whose structure has been determined by X-ray crystallography. It adopts approximate square-planar geometry, with the double bonds perpendicular to the square plane. The corresponding ethylpalladium derivative 1b has been prepared by a similar method, but it is considerably less stable. It decomposes by beta-elimination to produce ethene and a transient hydride complex, which either undergoes migratory insertion to give [Pd-2(mu-Cl)(2)(eta(1),eta(2)-C8H13)(2)], 2a, or dinuclear reductive elimination with a second molecule of 1b to produce ethane, [PdCl2(cod)], free cyclooctadiene, and palladium metal. Complex 2a has also been prepared by reaction of [PdCl2(cod)] with NaBH4. At higher temperatures 2a converts to an equilibrium mixture with its eta(3)-allyl isomer, 2b. Reactions of [PdCl2(cod)] or K2PdCl4 in the presence of cyclooctadiene in aqueous solution to produce 2a or 2b have also been investigated.