pi-Allyl-palladium complexes stabilized by tripodal oxygen ligands [(C5H5)Co{P(OMe)(2)O}(3)](-) .2. Elimination instead of C-C coupling in reaction with resonance-stabilized carbanions

The reaction of the complexes [L(OMe)Pd(propenyl)] (1) and [L(OMe)Pd(2-methyl-propenyl)] (2) (L(OMe)(-)=[(C5H5)Co{P(OMe)(2)O}(3)](-)) with sodium malonate results in the formation of the anticipated C-C coupling products (2-R-C3H5)CH(CO(2)Et)(2) while [L(OMe)Pd{4-6-eta-(3-oxo-cholestenyl))] (4) and [L(OMe)Pd(4-6-eta-(cholestenyl)}] (5) react with eliminination to give the corresponding cholestadienes. With sodium 2-acetylcyclopentanoate (Na acp), ligand substitution takes place in the reaction with 1-3 (3=[L(OMe)Pd(2-(t)butyl-propenyl)]) to give complexes of the type [(2-R-propenyl)Pd(acp)]. Their stability depends on the substituent of the allyl group. While [(propenyl)Pd(acp)] decomposes at room temperature, [(2-(t)butyl-propenyl)Pd(acp)] and [(2-methyl-propenyl)Pd(acp)] are air stable compounds which could be isolated.