Study On Catalysis For Conjugated Dienes Polymerization Of New Confined Geometry Rare-earth Metal Complexes

In this thesis,a series of new fluorene-based constrained-geometry rare-earth center metal complexes have been designed and synthesized.They achieved highly selectivity polymerization of conjugated diene monomers.Moreover,we also deeply study the interaction between the complexes structure and polymer selectivity.The specific work content is as follows:(1)A series of novel constrained-geometry rare-earth metal complexes(CGC)bearing the ligand fluorenyl-methylene-tetrahydrofuranyl(η5-Flu CH2-THF)Y(CH2Si Me3)2(THF)and(η5-Flu CH2-THF)Lu(CH2Si Me3)2(THF)have been designed and synthesized by the alkane elimination reaction between the Flu CH2-THF ligand and the rare-earth metal trialkyls,and their single crystals were obtained.And their chemical properties and structure were fully characterized by NMR and X-ray diffraction analyses.Complexes 1 and 2 are monomeric THF solvates,in which the CGC ligand adopts a η5/κ1 bonding mode with the central metals via coordination of five carbon atoms from the fluorenyl fragment and the tetrahydrofuranyl oxygen atom.Through DFT calculation and buried volume calculation,we explained the relationship between the ligand chelating side arm species,steric hindrance,Lewis acidity,etc.of the cationic active species of the complex and the polymerization selectivity and polymerization activity.(2)We used a three-component catalytic system composed of complexes 1 or 2 with cocatalyst [Ph3C][B(C6F5)4] and alkyl aluminum additive Al R3,to study the behavior of coordination polymerization of butadiene.Upon activation with AliBu3 and [Ph3C][B(C6F5)4],complex 1 showed high activity toward conjugated diene polymerization,to afford up to cis-1,4-polybutadiene(98.5%).Through the NMR tracking tests of the mixtures generated by different ratios of AliBu3 and complex 1,we revealed the special effects of alkyl aluminum additives on our designed novel complexes,and the effect of the types of alkyl aluminum additives on the selectivity of butadiene polymerization catalyzed by complex 1 was also explained.(3)We used a three-component catalytic system composed of complexes 1 or 2 with cocatalyst [Ph3C][B(C6F5)4] and alkyl aluminum additive Al R3,to study the behavior of coordination polymerization of isoprene.Upon activation with AliBu3 and [Ph3C][B(C6F5)4],complex 1 showed high activity toward conjugated diene polymerization,to afford up to3,4-unit enriched polyisoprene(69%).The effects of different types and contents of alkyl aluminum additives Al R3 on the polymerization behavior of isoprene were explored and explained,and the possible mechanism of complex 1 regulating the selectivity of isoprene polymerization was also elucidated.