Development of new rare earth metal polymerization catalysts

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1.1,4-Cis stereospecific polymerization of 1,3-butadiene by samarocene catalystsThe C_5Me_5R-ligated samarocene(II) complexes, (C_5Me_4R)_2Sm(THF)_x(1, R=Me ; 2, R=Et ; 3, R=i-Pr, 4, R=n-Bu, 5 ; R=TMS ; x=1 or 2), in combination with modified methylaluminoxane(MMAO) were examined in cyclohexane with respect to their catalytic performances for the polymerization of butadiene. Complexes 2-5 showed considerable promotion in both catalytic activity and regularity of the resulting polymer as compared to parent 1 : activity,3>>5〜4>2>1 ; 1,4-cis selectivity at 50℃,3〜5>4>2>1.2.1,4-Cis stereospecific polymerization of 1,3-butadiene by cationic rare earth metallocene catalystsCationic metallocene complexes[(C_5Me_5)_2Ln][B(C_6F_5)_4](Ln=Pr, Nd, Gd) in combination with ^iBu_3Al efficiently induce highly 1,4-cis specific polymerization of butadiene. The activity of the Gd complex/^iBu_3Al system is high enough to exhibit good catalytic activity even at low temperature. Polymerization at -78℃ gave … More polybutadiene with nearly perfect 1,4-cis microstructure (>99.9%) with sharp molecular weight distribution (M_w/M_n=1.45) and in reasonable yield.3.Synthesis, Structural Characterization, and Novel Catalysis of Rare Earth Alkyl Complexes Bearing Silylene-Linked Cyclopentadienyl-Phosphido LigandsThe reactions of Ln(CH_2SiMe_3)_3(THF_2)(Ln=Y, Yb, Lu) with 1 equiv of Me_2Si(C_5Me_4H)(PHR)(R=Ph, Cy) afforded the first silylene-linked cyclopentadienylphosphido rare earth alkyl complexes, [Me_2Si(C_5Me_4)(μ-PR)Ln(CH_2SiMe_3)]_2. In contrast with the analogous cyclopentadienyl-amido and metallocene complexes, these complexes adopt a dimeric structure through phosphide bridging, while the alkyl ligand is placed in a terminal position. Owing to their unique steric and electronic ligand environments, most of these complexes showed much higher activity for the polymerization of ethylene and hydrosilylation of olefins than that of the conventional metallocene or amido analogues. Moreover, when treated with [Ph_3C][B(C_6F_5)_4], these complexes showed extremely high regio- and stereoselectivity for the 3,4-polymerization of isoprene, which yielded the isotactic (>99% mmmm) 3,4-poly(isoprene) selectively. This is the first example of stereospecific 3,4-polymerization of isoprene. Less