Novel Non-metallocene Transition Metal Complexes: Synthesis,Characterization And Their Catalytic Behavior

Polyolefin is one kind of widely used polymer materials and is closely related to our life,the requirement of polyolefin is gradually increased in recent years.Development and utilization of novel catalysts is not only the key to synthesize polyolefin materials with various properties but also the core power of the vigorous development of polyolefin industry.In chronological order,the development of polyolefin catalysts has undergone four main stages: Ziegler-Natta catalyst,chromium catalyst,metallocene catalyst and non-metallocene early transition metal and late transition metal catalyst.Among them,the relatively later developed non-metallocene transition metal(early transition metal and late transition metal)catalyst has attracted much more attention due to some of its own characteristics such as easy preparation,low price,space and stereo effect easy modification.So this article selected part of the fourth period of transition metal complexes,which bear anilido-imine and bulky salicylaldiminato ligands using in the olefin polymerization and successfully synthesized a series of different structures and properties of alkenes homopolymerization and copolymerization products.The research contents are summarized as follows:(1)The polymerization of norbornene was studied by using novel N,N,N-tridentate nickel complexes/MAO catalytic system.Among the four nickel complexes,the complex with bulky isopropyl group on imine-aryl ring showed highest catalytic activity and the activity could be up to 3.32×105 PNB mol(Ni)–1·h–1.In addition,the effects of Al/Ni ratio and reaction temperature on catalytic activity and molecular weight of obtained polymer were also investigated.Based on the infrared spectrum ofpolymers,we determined that the polymerization of norbornene was via vinyl-addition type.(2)A series of N,N,N-tridentate quinolinyl anilido-imide chromium(II)and chromium(III)complexes were synthesized and well characterized by elemental analysis,infrared spectrum and X-ray diffraction etc.We investigated the performance of ethylene polymerization catalyzed by all different valence of chromium complexes upon activation with MAO and also deduced that the prepared polyethylene was linear low molecular weight polymer with narrow molecular weight distribution by using high temperature GPC and 13 C NMR etc.Furthermore,the C-H activation reaction between excess nBu Li and ligand was studied and the central metal valence changing reaction was also investigated in the presence of halogenated alkane.(3)The new synthesis of iron(II)complexes bearing anilido-imine ligands were tested as catalysts for ATRP of methyl methacrylate(MMA)using benzyl chloride(Bn Cl)as initiator.The effects of different ratios of catalyst,initiator and monomer on polymerization reaction were investigated.Dynamic study showed that iron(II)complexes/Bn Cl catalytic systems had the features of “living”/controlled radical polymerization.(4)All the new copper(II)complexes bearing anilido-imine ligands were tested as catalysts for reverse ATRP of styrene using AIBN as radical initiator.The effects of initiator loading,monomer concentration and other factors on the polymerization rate were investigated,especially the difference of AIBN decomposition rate caused by different polymerization temperature had a great influence on the polymerization reaction.Dynamic study showed that Cu(II)complexes/AIBN catalytic systems exhibited significantly “living” features.(5)A series of trityl-substituted salicylaldiminato ligands and vanadium(III)complexes were synthesized and well characterized by NMR,elemental analysis and infrared spectroscopy etc.The performance of ethylene polymerization and copolymerization with hexene catalyzed by vanadium(III)complexes were investigated upon activation with different co-catalysts such as MAO and Al Et2 Cl.In the presence of Al Et2 Cl,These vanadium(III)complexes exhibited high catalytic activity and the activity could be up to 5.8×104 Kg of PE·mol(V)–1·h–1.Combination with high temperature GPC,13 C NMRand other instrucments,we concluded that the prepared polyethylene was linear structure without branching,and the poly(ethylene-co-1-hexene)exhibited relatively narrow PDI,moderate comonomer incorporation as well as molecular weight.However,when MAO or MMAO was used as the co-catalyst,the catalytic activity decreased obviously,but the molecular weight of polyethylenes could reach more than one million,which were ultra high molecular weight polymers,meanwhile the PDI of all the polymers was relatively narrow.In addition,the effects of catalyst amount,polymerization temperature,solvent and other factors on the polymerization were also studied.The catalyst loading is reduced to a very low level and the cost is also saved,so these catalysts have potential applications in industrial processes.