Photoinduced rac/meso interconversions of bridged bis(indenyl) zirconium dichlorides

Article abstract of DOI:10.1016/1381-1169(96)00240-3

Upon irradiation of a C₂-symmetric rac-isomer of an ansa-zirconocene dichloride, an interconversion into the C(s)-symmetric meso-form is observed until a photostationary state between the two diastereomers is reached. The final rac/meso-proportion and the interconversion rate depend on the structure of the different metallocenes. Results of α-olefin polymerization catalyzed by [Me₂Si(2-Me-4,6-(i)Pr₂ Ind)₂]ZrCl₂ rac and meso, respectively, and methylalumoxane (MAO) as cocatalyst are reported. In propene polymerization the rac-diastereomer shows the higher activity whereas in pentene, hexene, and octene polymerization the meso-isomer is significantly more active. For all polymers a lower molecular weight is found using the meso-diastereomer as catalyst.