Carbonylation studies of Pd-methyl complexes modified with 1,4-Cs-symmetrical diphosphine ligands

Neutral palladium methyl chloride 2a–d [PdCH3(PˆP′)Cl] and cationic palladium methyl acetonitrile mono-triflate 3a–d [PdCH3(PˆP′)(CH3CN)](CF3SO3) complexes were synthesized and fully characterized (PˆP′ = 1a–d). All the neutral and cationic complexes containing a Cs-symmetric diphosphine exist in solution as a mixture of geometric isomers. The carbonylation at atmospheric pressure of the neutral and cationic complexes revealed that migratory insertion of carbon monoxide is not stereospecific in these systems. The neutral and cationic acyl complexes were formed in situ as mixtures of stereoisomers, which were characterized by means of NMR spectroscopy. The crystal structures of [Pd(1a)Cl]2(OTf)2 and 2d are described.