Abstract: Novel constrained-geometry-configuration(CGC) rare-earth metal complexes(IndCH₂-Py)₂Sc(CH₂SiMe₃)(1) and(FluCH₂-Py)Sc(CH₂SiMe₃)₂(2)(Py=Pyridyl,Ind=Indenyl,Flu=Fluorenyl) have been synthesized by treating rare-earth metal trisalkyls with CpCH₂-Py(Cp=Ind,Flu) compound,and fully characterized by NMR and X-ray diffraction analyses.Upon activation with AliBu₃ and[B(C₆F₅)₄],the two compounds showed different catalytic behavior towards copolymerization.A catalytic system containing complex 2 could initiate the copolymerization between styrene and ethylene while complex 1 was inert for the same purpose.Both gel permeation chromatography(GPC) curves and solvent extraction experiments corroborated that the products were mainly consisted of copolymers with negligible by product.The catalytic system based on complex 2,not only exhibited excellent activity(up to 1.21×10³ kg/(mol(Sc)·h) and selectivity for syndiospecific styrene polymerization and styrene-ethylene copolymerization,but also afforded syndiotactic styrene-styrene sequences with controllable styrene contents in the styrene-ethylene copolymers.These copolymers were further confirmed by the observation of an endothermic peak(Tm) at 237~253℃ in the differential scanning calorimetry(DSC) curves.These copolymers have moderate relative molecular mass(M_n=3.2×10⁴~10.7×10⁴) and relative molecular mass distributions(M_w/M_n=2.05~2.34).