PHOTOINDUCED RAC MESO INTERCONVERSIONS OF BRIDGED BIS(INDENYL) ZIRCONIUM DICHLORIDES/

Upon irradiation of a C-2-symmetric rac-isomer of an ansa-zirconocene dichloride, an interconversion into the C-5-symmetric meso-form is obs erved until a photostationary state between the two diastereomers is r eached. The final rac/meso-proportion and the interconversion rate dep end on the structure of the different metallocenes. Results of alpha-o lefin polymerization catalyzed by [Me(2)Si(2-Me-4,6-(i)Pr(2)Ind)(2)]Zr Cl2 rac and meso, respectively, and methylalumoxane (MAO) as cocatalys t are reported. In propene polymerization the rac-diastereomer shows t he higher activity whereas in pentene, hexene, and octene polymerizati on the meso-isomer is significantly more active. For all polymers a lo wer molecular weight is found using the meso-diastereomer as catalyst.