C-2V-SYMMETRICAL AND C-2-SYMMETRICAL ANSA-BIS(FLUORENYL)ZIRCONOCENE CATALYSTS - SYNTHESIS AND ALPHA-OLEFIN POLYMERIZATION CATALYSIS

C-2v-symmetric ethylenebis(9-fluorenyl)zirconium dichloride (1) and it s C-2-symmetric bis[9-(1-methyl)fluoreny1] derivative (2) have been sy nthesized in good yields using a convenient synthetic route. Precursor 1 activated with triphenylcarbenium tetrakis(pentafluorophenyl)borate (3) catalyzes propylene polymerization with a constant activity of (6 .28 +/- 1.63) x 10(7) g of PP/((mol of Zr).[C3H6]. h) between -20 and +70 degrees C. The polypropylene is ideally atactic and has the same ( $) over bar M(W) of (6.03 +/- 1.19) x 10(5). The above system catalyze s ethylene polymerization with a maximum activity of 1.4 x 10(10) g of PE/((mol of Zr).[C2H4]. h) at -20 degrees C which decreases exponenti ally with an increase of T-p. All the polyethylenes produced between - 20 and +50 degrees C have the same ($) over bar M(W) of (5.57 +/- 0.49 ) x 10(5). In contrast, precursor 2 catalyzed the formation of anisota ctic polypropylene of low stereoregularity. Molecular mechanics calcul ations indicated that substituents on the fluorenyl rings have little effect on both diastereomeric ratios in the synthesis and stereoselect ivities in the polymerization.