ENANTIOSELECTIVE ALTERNATING OLEFIN CARBON-MONOXIDE COPOLYMERIZATION - A NEW CONCEPT FOR ACTIVITY AND STEREOSELECTIVITY

Cationic Pd-complexes modified by S)-2-(diphenylphosphino)ferrocenyl]e thyl}phosphine (1a) give very active catalytic systems for the regiore gular isotactic specific copolymerization of propene with CO. Other al k-1-enes also give stereoregular and regioregular copolymers, even if with lower productivity. The copolymers are isolated as -tetrahydrofur an-2,2,5,5-tetrayl-2-oxy-methylenes) B in the solid state and give the isomeric poly(2-alkyl-1-oxopropane-1,3-diyls) A by dissolution in (CF 3)(2)CHOH. Solid polymer A (R = Et) is formed back at least partially when the dissolved material is reprecipitated from MeOH. The use of th e related (ferrocenyl)diphosphine ligands 1b-e and 2 as the catalyst m odifier shows that the presence of both elements of chirality and of l arge substituents on the P-atoms of the ligand is necessary to achieve good stereocontrol, and that the large difference in basicity between the two P-atoms is probably the reason for the good catalytic activit y.