Development of new rare earth metal polymerization catalysts

在环己烷中考察了c_5me_5r -键合的samarocene（II）配合物（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或2）与改性甲基铝氧烷（MMAO）结合对丁二烯聚合的催化性能。与母体1相比，配合物2-5在催化活性和规律性上都有显著的提高：活性为3>>5 ~ 4>2>1；阳离子稀土茂金属催化剂在50℃下对1,4-顺式选择性聚合1,3-丁二烯。阳离子茂金属配合物[(C_5Me_5)_2Ln][B(C_6F_5)_4]（Ln=Pr, Nd, Gd）与^iBu_3Al结合可有效诱导高度1,4-顺式聚合丁二烯。Gd配合物/^iBu_3Al体系的活性足够高，即使在低温下也表现出良好的催化活性。在-78℃下聚合得到的聚丁二烯具有接近完美的1,4-顺式结构（>99.9%），分子量分布明显（M_w/M_n=1.45），产率合理。含硅基环戊二烯-磷酸配体稀土配合物的合成、结构表征及新型催化作用Ln(CH_2SiMe_3)_3(THF_2)（Ln=Y, Yb, Lu）与1等量的Me_2Si(C_5Me_4H)(PHR)（R=Ph, Cy）反应生成了第一个硅基环戊二烯-磷酸稀土配合物[Me_2Si(C_5Me_4)(μ-PR)Ln(CH_2SiMe_3)]_2。与类似的环戊二烯酰胺和茂金属配合物相比，这些配合物通过磷化物桥接采用二聚体结构，而烷基配体位于末端位置。由于其独特的空间和电子配体环境，这些配合物在乙烯聚合和烯烃氢硅化反应中表现出比传统的茂金属或酰胺类似物高得多的活性。此外，当用[Ph_3C][B(C_6F_5)_4]处理时，这些配合物对异戊二烯的3,4聚合表现出极高的区域选择性和立体选择性，从而选择性地得到等规（>99% mmmm） 3,4聚异戊二烯。这是异戊二烯立体定向聚合的第一个例子。少

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