Single site polymerization of ethylene and 1-olefins initiated by rare earth metal complexes

Ethylene polymerization was explored by using the racemic SiMe(2)(2-SiMe(3)-4-tBuC(5)H(2))(2)Sm(THF)(2) complex (1), meso type Me(2)Si(Me(2)SiOSiMe(2))(3-tBuC(5)H(2))(2)Sm(THF)(2) complex (2), and C-1-symmetric SiMe(2)[2,4-(SiMe(3))(2)C5H2][3,4-(SiMe(3))(2)C5H2]Sm(THF)2 complex (3) in the absence of methylaluminoxane. As a result, the mese isomer exhibits highest initiating activity, but the number-average molecular weight is relatively low ((M) over bar(n) = 50000). In contrast to these complexes, the C-1-symmetric complex provides the highest molecular weight of polyethylene, (M) over bar(n) > 1000000, with relatively narrow molecular weight distribution ((M) over bar(w)/(M) over bar(n) = 1.60). Only the racemic complex exhibits good activity for the polymerization of propylene, 1-pentene and 1-hexene.