Regio- and stereoregular copolymerisation of propene with carbon monoxide catalysed by palladium complexes containing atropisomeric diphosphine ligands

The use of palladium catalysts, modified by chelate diphosphine ligands based on a diphenyl atropisomeric moiety, permits a good control of regio- and stereochemistry in the alternating copolymerisation of propene with carbon monoxide. The completely aromatic ligands (S)-(6,6'-dimethoxybiphenyl-2,2'-diyl)bis(diphenylphosphine) and (S)-(6,6'-di- methylbiphenyl-2,2'-diyl)bis(diphenylphosphine) give regioirregular materials. Their stereoregularity cannot be easily evaluated but appears to be rather low on the basis of optical activity determinations. Using ligands containing sterically hindered alkyl substi- tuents on the phosphorus atoms (such as cyclohexyl or isopropyl) completely regioregular copolymerisation takes place. The produced copolymers show a high degree of stereoregularity approaching 96% of I-diads. Ligands lacking C, symmetry show only a small decrease in regioregularity and stereoregularity. Very high catalytic activity is observed with the ligand (all S) (R,)-(6,6'-dimethoxybiphenyl-2,2'-diyl)bis(2,5-dimethylphospholane). This ligand allows the production of a completely regioregular copolymer that shows almost complete atacticity.