Synthesis and chemistry of diphenyl-2-pyridylphosphine complexes of palladium(0). X-ray characterisation of Pd(Ph(2)Ppy)(2)-(eta(2)-DMAD) and trans-Pd(Ph(2)Ppy)(2)(PhC = CH2)(CF3CO2)

The zerovalent complexes Pd(Ph(2)Ppy)(3) 1 and Pd(Ph(2)Ppy)(2)(dba) 2, wher e Ph(2)Ppy is diphenyl-2-pyridylphosphine and dba=trans,trans-dibenzylidene acetone, have been synthesized and characterised. Reactions of 1 with alkyn es have been studied and the dimethyl acetylenedicarboxylate complex Pd(Ph( 2)Ppy)(2)(eta(2)-DMAD) 3, where DMAD is dimethyl acetylenedicarboxylate, is olated and structurally characterised. The complexes trans-Pd(Ph(2)Ppy)(2)( PhC=CH2)X, X=CF3CO2- 4 or Cl- 5, and trans-Pd(Ph(2)Ppy)(2){CO(CH3)C=CH2}Cl 6 result from oxidative addition of phenylacetylene/CF3CO2H, phenylacetylen e/Et3NHCl and methacryloyl chloride respectively to 1, and the crystal stru cture of 4 is presented. The alkenyl ligand is bound to palladium through t he alpha carbon in 4. Insertions into the M-C bond of the vinyl complexes h ave been studied. No isolable insertion product is obtained with carbon mon oxide although the complex is active for the catalytic alkoxycarbonylation of phenylacetylene to 2-phenylpropenoate. Propadiene inserts into the Pd-C bond in 4 to give the cationic pi-allyl complex [Pd(Ph(2)Ppy)(2){eta(3)-C3H 4C(Ph)=CH2}][CF3CO2] 7. The complex Pd(Ph(2)Ppy)(3) is found to catalyse th e vinylation of Ph(2)Ppy to the corresponding 2-propenylphosphonium trifluo romethanesulfonate.