Enantioselective alternating terpolymerization of propene and ethene with carbon monoxide

Optically active poly(1,4-ketode)s were synthesized by alternating terpolymerization of carbon monoxide with ethene and propene using the dicationic palladium(II) complexes [Pd(P∧P)(H2O)2](OSO2 CF3)2 1-3 (where P∧P is a chelate diphosphine ligand) modified with the optically pure ligands (R)(Sp)-1-[2-(diphenylphosphino)-ferrocenyl]ethyl -dicyclohexylphosphine 1a, (R)-6,6′-(dimethoxybiphenyl-2,2′-diyl)bis(dicyclohexylphosphine) 2a and (S)-6,6′(dimethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine) 3a as catalyst precursors. The influence of different ethene to propene ratios in the reaction mixture on the productivity of the catalyst systems as well as on the composition and structure of the produced terpolymers was investigated. For all catalyst precursors, the distribution of the two olefin comonomers appears to be random. The productivity is more strongly increased by increasing the ethene concentration when the catalyst system is not regiospecific for propene, i.e. when 3 is used. The influence of the growing chain on the enantioface selection for propene appears to be of minor importance with respect to the enantioselectivity caused by the enantiomorphic site of the catalyst.