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 C 5 H 2 ][3,4‐(SiMe 3 ) 2 C 5 H 2 ]‐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 ( M n = 50000). In contrast to these complexes, the C 1 ‐symmetric complex provides the highest molecular weight of polyethylene, M n > 1, with relatively narrow molecular weight distribution ( M w / M n = 1.60). Only the racemic complex exhibits good activity for the polymerization of propylene, 1‐pentene and 1‐hexene.