Enantioselective Alternating Olefin‐Carbon Monoxide Copolymerization: A new concept for activity and stereoselectivity

Abstract

Abstract Cationic Pd‐complexes modified by dicyclohexyl{( R )‐1‐[( S )‐2‐(diphenylphosphino)ferrocenyl]ethyl}phosphine ( 1a ) give very active catalytic systems for the regioregular isotactic specific copolymerization of propene with CO. Other alk‐1‐enes also give stereoregular and regioregular copolymers, even if with lower productivity. The copolymers are isolated as poly(4‐alkyl‐tetrahydrofuran‐2,2,5,5‐tetrayl‐2‐oxy‐2‐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 the related (ferrocenyl)diphosphine ligands 1b − e and 2 as the catalyst modifier shows that the presence of both elements of chirality and of large 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 activity.