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

Ethylene polymerization was explored by using the racemic SiMe2(2‐SiMe3‐4‐tBuC5H2)2Sm(THF)2 complex (1), meso type Me2Si(Me2SiOSiMe2)(3‐tBuC5H2)2Sm‐(THF)2 complex (2), and C1‐symmetric SiMe2[2,4‐(SiMe3)2C5H2][3,4‐(SiMe3)2C5H2]‐Sm(THF)2 complex (3) in the absence of methylaluminoxane. As a result, the meso isomer exhibits highest initiating activity, but the number‐average molecular weight is relatively low (Mn = 50000). In contrast to these complexes, the C1‐symmetric complex provides the highest molecular weight of polyethylene, Mn > 1000000, with relatively narrow molecular weight distribution (Mw/Mn = 1.60). Only the racemic complex exhibits good activity for the polymerization of propylene, 1‐pentene and 1‐hexene.