Phenoxy / Heterocyclic Ligands For Transition Metal Complexes Synthesis And Catalytic Olefin Polymerization Study

In this dissertation, a series of new olefin polymerization catalysts, includingearly transition metal complexes, such as titanium, zirconium, vanadium, and latetransition metal complexes based on nickel or copper, have been synthesized andcharacterized, ten molecular structures of which have been confirmed by singlecrystal X-ray analyses. Mainly, catalytic activities of these complexes for ethyleneand norbornene were investigated. The effects of catalyst structures, polymerizationconditions such as Al/M molar ratio, reaction temperature and ethylene pressure onolefin polymerization behaviour have been discussed in detail. Moreover, thesignificant differences between homogeneous non-bridged half-metallocene catalystsand their corresponding supported catalysts on SBA-15 have also been compared bythe catalytic activities, molecular weights and morphologies of polymers. The fulldissertation was summarized as follows:1. Three half-sandwich titanium catalysts bearing non-symmetrical phenoxy-oxazole ligands have been synthesized. After activated by methylaluminoxane (MAO),these catalytic precursors could polymerize ethylene with high catalytic activities upto 1.23×10⁶gPEmol^-1Tih^-1 and produce narrow, unimodal molecular weightsdistribution (MWD) and high molecular weight polymers(M_w/M_n=1-3, 10⁵-10⁶).Herein, it is noteworthy that the steric bulk effect of the ortho substitued group (R₁) ofthe phenoxy-oxygen on catalytic activity and molecular weight of polymers issignificant. At the similar reaction condition, the catalytic activities rink in descendingorder R₁=Me＞H＞^tBu, however, the molecular weight in the order H＞Me＞^tBu.Further, immobilizing these kinds of catalysts on SBA-15, the nanofibrouspolyetnylene (diameter for 40-80nm) can be obtained, which possess higher molecularweitght (up to 2.90×10⁶) than that of homogeneous counterpart(9.38×10⁵).2. The supported catalysts have been prepared by immobilizing the non-bridgedhalf-titanocene and zirconocene on mesoporous molecular sieve SBA-15, which cancatalyize the ethylene polymerization and successfully obtain the nano-polyethylenefibers with high molecular weights. The effect of the immobilized titanium orzirconium catalyst with different catalytic activity on polymerization reaction hasbeen exhibited by their polymerization behaviour. For supported titanium catalyst,different morphologic polyethylene fibers can be given via the modulation of reactiontemperature under definite condition. Analogous phenomena cannot be observed for supported zirconium catalyst, However, the catalytic activities have always increasedas the reaction temperature rises till 100℃.3. Two special formative nickel(â…¡) and copper (â…¡) complexes with non-symmetric phenoxy-imidazole ligands have been prepared and characterized. Thevery high catalytic activities for norbomene polymerization have been provided bythem at the activation of MAO. In particular, the superhigh catalytic activity can beacquired by nickel catalyst and the highest value is up to2.29×10⁸gPNBmol^-1Nih^-1.The moderate catalytic activity has also been produced by copper catalyst, the highestvalue for 3.16×10⁵ gPNBmol^-1Cuh^-1. This is one of catalysts possessing highestactivities for vinyl addition polymerization of norbomene in literatures reported. Inaddition, the molecular weights of all polymers are very high in grade 10⁶.4. The bis(benzimidazole) pyridine vanadium (â…¢) (1) and bis(benzoxazole)pyridine vanadium(â…¢) (2) complexes have been prepared and their ethylenepolymerization activities have been investigated in detail. The highest catalyticactivities is up to 1.12×10⁶gPEmol^-1Vh^-1 for 1 and 2.36×10⁵gPEmol^-1Vh^-1 for 2,respectively. Moreover, within the reach of whole detected temperature (15-75℃),the steady catalytic activities can be maintained for them, indicating that this type ofcatalyst possesses very good thermal stability.5. Four binuclear or multinuclear titanium-based complexes withμ-oxygen-bridged linkage have been synthesized and characterized. The rich and colorfulstructural features have been analyzed.