SYNTHESES AND CHARACTERIZATION OF [(MU-CF 3CO2)(2)LN(MU-CF3CHO2)ALR(2)CENTER-DOT-2THF](2) AND THEIR CATALYTIC ACTIVITIES FOR POLYMERIZATIONOF SOME POLAR MONOMERS

Three new bimetallic complexes were synthesized and crystalized by rea ctions of (CF3CO2)(3)Ln With R(1) AlR(2)(Ln=Nd and Y, R(1)=H, R=i-C4H9 ; Ln=Eu, R=R(1)=C2H5) in tetrahydrofuran solution, and their crystal s tructures were determined using a X-ray diffraction method. The struct ures and the questions on valence state and noncoplanarity in the stru ctures were confirmed and cracked by means of H-1 NMR and C-13 NMR spe ctra, especially by C-13-H-1 COSY 2D NMR technique. A general formula of molecules of the three rare earth complexes was defined as follows: [(mu-CF3CO2)(2)Ln(mu-CF3CHO2)AlR(2) . 2THF](2) A mechanism on the for mation of the new complexes was also proposed through the following fi ve steps: alkylating, beta-elimination (or hydrogenation), hydrogen tr ansfer, linkage and association. Both Y-Al and Eu-Al complexes functio n as a catalyst in polymerization of MMA and ECH. The polymer obtained from the first monomer is mainly syndiotactic chain structure and the polymerization of the last monomer shows higher catalytic activity. T he Y-Al complex also capable of ring-opening polymerization of THF in case of adding-vary small amount of ECH and a oxonium ion mechanism of THF polymerization was suggested from the analysis of THF polymer ter minal.