Regio‐ and stereo‐selective alternating copolymerization of carbon monoxide with propene

Compounds of palladium with ten different chelated bisphosphine ligands were investigated for their catalysis of alternating copolymerization of propene with carbon monoxide. The bisphosphine structure and chelate ring size influence strongly the activity, regio‐ and stereo‐selectivity of the catalysts. Molecular mechanics calculations on the π‐olefin complex showed that the non‐bonded interaction between propene and the ligands on Pd is both regio‐ and stereo‐selective. Primary insertion is about seven times more probable than secondary insertion for the Pd complex of bis(diphenylphosphino)butane ligand. The enantioselective catalysts favor the meso enchainment of propene. Gas chromatography/mass spectrometry (GC‐MS) of oligomers showed that most chains are initiated by PdH species with less frequent initiation by PdOCH3 complexes; β‐hydrogen elimination is the dominant chain termination process.