| Abstract
| - New trivalent samarium and yttrium complexes with bridging bis(cyclopentadienyl) ligandswere synthesized, and olefin polymerization catalysis of the complexes having an alkyl group[R = CH(SiMe3)2] on the metal was investigated. Three types of the rare earth halides (rac,C1, and meso) whose structures differed with respect to the bridging group and the positionsof substituents on the cyclopentadienyl (Cp) rings were prepared: rac-Sm−Cl, Me2Si[2,4-(Me3Si)2C5H2]2SmCl2Li(THF)2 (1a); C1-Sm−Cl, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]SmCl2Li(THF)2 (2a); C1(Ph2Si)−Sm−Cl, Ph2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]SmCl2Li(THF)2 (3); meso-Sm−Cl, [1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3CC5H2)2SmCl2Li(THF)2 (4a);rac-Y−Cl, Me2Si[2,4-(Me3Si)2C5H2]2YCl2Li(THF)2 (5a); C1-Y−Cl, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]YCl2Li(THF)2 (6a); meso-Y−Cl, [1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3SiC5H2)2YCl(THF) (7a). Although the rac and C1 complexes (1a, 2a and 5a, 6a) were obtained as anisomeric mixture by the reaction of LnCl3 (Ln = Sm, Y) with a dilithium salt of the ligandMe2Si[(Me3Si)2C5H3]2, it could be separated into both the pure complexes by utilizing thedifference of solubility in hexane in each case. Structural data were obtained on 1a, 2a, 3,and 7a to confirm the structures expected from NMR spectroscopy. The (ring centroid)−metal−(ring centroid) angles in these complexes are ca. 10−20° smaller than those innonbridging bis(cyclopentadienyl) rare earth complexes. The rare earth halides 1a, 2a, 4a,5a, 6a, and 7a reacted with LiCH(SiMe3)2 to afford rare earth alkyl complexes, rac-Sm−R,Me2Si[2,4-(Me3Si)2C5H2]2SmCH(SiMe3)2 (1b); C1-Sm−R, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]SmCH(SiMe3)2 (2b); meso-Sm−R, [1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3CC5H2)2SmCH(SiMe3)2 (4b); rac-Y−R, Me2Si[2,4-(Me3Si)2C5H2]2YCH(SiMe3)2 (5b); C1-Y−R, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]YCH(SiMe3)2 (6b); meso-Y−R, and [1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3SiC5H2)2YCH(SiMe3)2 (7b), respectively. Only C1 type alkyl complexes (2b and6b) polymerize ethylene, giving high molecular weight polyethylenes, and the precisestructure of the active Sm complex 2b was determined by X-ray crystallography.
- Three types (rac, C1 symmetry, and meso) of new trivalent samarium and yttrium complexes bearing a bridged bis-Cp ligand were prepared, and their olefin polymerization catalyses were investigated. C1 symmetric alkyl complexes Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]LnCH(SiMe3)2 [Ln = Sm (2b), Y (6b)] exhibited high ethylene polymerization activities, and the structure of 2b was revealed by a single-crystal X-ray diffraction study.
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