Publication YXY 2011
C. Descour, R. Duchateau, M. R. Mosia, G.-J. M. Gruter, J. R. Severn, S. Rastogi, Polym. Chem. 2011, 2, 2261.
1-Pentene and 4-methyl-1-pentene (4M1P) have been polymd. using several C2-sym. ansa-zirconocene catalysts rac-X(2-R1,4-R2-Ind)2ZrCl2 X = C2H4, R1 = R2 = H (I); X = SiMe2, R1 = R2 = H (II); X = SiMe2, R1 = Me, R2 = H (III); X = SiMe2, R1 = H, R2 = Ph (IV); X = SiMe2, R1 = Me, R2 = Ph (V) with MAO as cocatalyst. The effects of polymn. conditions as well as substituents on the indenyl ligand were studied. Except for the poly-1-pentenes synthesized with III and V at low temps., low mol. wt. isotactic polymers were generally obtained.
Compared to their behavior in propylene polymn., the relative activity and selectivity of catalysts I, II, III, IV, and V are considerably different for 1-pentene and 4M1P polymn. Of the five catalysts, I and IV showed the highest activities for both 1-pentene and 4M1P polymn., while V resulted in the lowest activities, esp. for 4M1P polymn. Subsequently, a Cs- and several C1-sym. zirconocenes, (R1)2C(3-R2-Cp)(2,7,-R3-Flu)ZrCl2 R1 = Me, R2 = R3 = H; R1 = R2 = Me, R3 = H; R1 = Me, R2 = tert-Bu, R3 = H; R1 = Me, R2 = R3 = tert-Bu; R1 = Ph, R2 = tert-Bu, R3 = H; and R1 = Ph, R2 = R3 = tert-Bu, were tested in 1-pentene and 4M1P polymn. with MAO as cocatalyst.
The effect of substituents on the bridge and the cyclopentadienyl (Cp) and fluorenyl (Flu) ligands was studied relative to the polymn. temp. and type of monomer. The mol. wts. of the polymers were considerably higher than those of the poly-1-pentenes and P4M1Ps obtained with the C2-sym. zirconocenes. The catalytic activities and polymer mol. wts. strongly depend on the fluorenyl substituent and the bridge, while the type of substituent on the Cp ligand has a strong influence on the tacticity of the polymers.