Palladium(ii) complexes of new OPN phosphine ligands and their application in homogeneously catalysed reactions of CO with alkenes or alkynes

Abstract

Palladium complexes of a series of functionalised phosphines bearing the OPN donor set [2-pyCH₂P(Ph)CH₂(CHOCH₂CH₂CH₂), 1; 2-py CH₂P(Ph)–CH₂CH₂(CHOCH₂CH₂O), 2; 2-pyCH₂P(Ph)CH₂CH₂CO₂Me, 3; 2-pyP(Ph)CH₂(CHOCH₂CH₂CH₂), 4; 2-py = 2-pyridyl] have been prepared and characterised. Ligands 1–3 form five membered P–N chelates which is confirmed for PdCl₂ complexes of 1 and 3 by X-ray crystallography. O-coordination appears to be generally disfavoured although there is evidence of transient O-coordination for selected Pd complexes of 4. Palladium methyl and acetate complexes of all four ligands have been tested for catalytic activity in ethene/CO copolymerisation as well as alkoxy-carbonylation of propyne. Complexes of 1 and 4 show some activity in the copolymerisation reaction and complexes of 4 are active in the methoxy carbonylation of propyne. Unlike related pyridyl(diaryl)phosphines, 4 produces a much more stable catalyst system that does not require large excesses of ligand to maintain activity.