SYNTHESIS AND OLEFIN POLYMERIZATION CATALYSIS OF NEW BIVALENT SAMARIUM COMPLEXES WITH BRIDGING BIS(CYCLOPENTADIENYL) LIGANDS

This paper deals with the preparation and olefin polymerization cataly sis of six new divalent samarium complexes. These bridged bis(cyclopen tadienyl) (Cp) complexes exhibit various structures with regard to the bridging group and the position of substituents on the Cp rings: rac- tBu, Me2Si(2-Me3Si-4-tBuC(5)H(2))(2)Sm(THF)(2) (7); rac-tBuMe(2)Si, Me 2Si(2-Me3Si-4-tBuMe(2)SiC(5)H(2))(2)Sm(THF)(3) (8); C-1 symmetric, 2,4 -(Me3Si)(2)C5H2][3,4-(Me3Si)(2)C5H2]-Sm(THF)(2) (9); meso, -(Me2Si)(Me 2SiOSiMe2)](3-tBuC(5)H(2))(2)Sm(THF)(2) (10); C-2v symmetric (Ph2Si), Ph2Si[3,4-(Me3Si)(2)C5H2](2)Sm(THF)(2) (11); C-2v symmetric [(SiOSi)(2 )], ,2-(Me-2-SiOSiMe2)(2)](3-tBuC(5)H(2))(2)Sm(THF)(2) (12). The struc tures of 7, 8, 10, and 12 were confirmed by X-ray crystallographic ana lysis. Among these divalent complexes, meso type complex 10 showed the highest activity for polymerizations of ethylene (5 x 10(5) g of PE/( mol h)) and C-1-symmetric 9 afforded the highest molecular weight of p olyethylene (M-n = 145 x 10(4)). Only racemic complexes 7 and 8 could polymerize l-olefins such as l-pentene and l-hexene, giving highly iso tactic polymers. Moreover, rac-7 induces catalytic cyclopolymerization of 1,5-hexadiene to give poly(methylene-1,3-cyclopentane).