Studies On Synthesis, Characterization And Catalysis For Olefin Polymerization Of Novel Metallocene Catalysts

Heterogeneous chromium-based catalysts are an important class of catalysts for producing polyethylenes in industry. The silica-supported chromium-based Phillips and Union Carbide catalysts have been used for the industrial production of high-density polyethylene for decades. The development of homogeneous chromium-based catalysts for olefin polymerization has also attracted intensive research interest in the past decade. To understand the nature of the active species of the Phillips and Union Carbide catalysts, a considerable amount of efforts have been dedicated to design well-defined chromium-based catalysts and to explore their catalytic performance for homogeneous model systems. It is difficulty to study the chemistry of Cr(III) because is paramagnetic nature. The chromium-based olefin polymerization systems have been largely ignored in develop homogeneous methylalumoxane(MAO)-activated systems which have attracted so much attention in the past decade. Recently, a great number of the most significant advances in Cp contained chromium-based catalyzed olefin polymerization systems have been made using as precatalysts, this chromium complexes bear additional neutral donors. Before this, this is only a little papers has reported the catalyst that the Cp ring bearing a imine-nitrogen atom and benzyl alcohol-oxygen atom, so we have desired a series of chromium-base complex contain nitrogen atom and oxygen atoms according to the different coordination ability of nitrogen and oxygen atom. A larger number of constrained geometry metallocene catalysts have been reported, those complexes have chelated a heteroatom donor constituent on the cyclopentadienyl ligand which have received extensive attention in this years. D?hring et al reported the isopropylimino functionalized cyclopentadienyl chromium(III) complex was reported having been synthesized and tested as ethylene polymerization catalyst.In this paper, we have successfully desired and synthesized series of contain imine-nitrogen and benzyl achol-oxygen atom coordinated constrained geometry chromium olefin polymerization catalyst, the catalytic olefin homopolymer and copolymer capacity of these catalysts in a different role of catalyst has been studied. At same time, structural features of the catalyst affect the catalytic activity of the polymerization conditions were studied. Complexes with a diimine ligand show good catalytic activity for ethylene polymerization and their catalytic property of those complexes can be easily tuned by changing the constituent on the imine groups.In chapter 3, access to the different electronic effect and stereo effect of ligands, we obtained 4 corresponding constrained geometry metallocene chromium catalysts according to modify the constituent on the imine nitrogen atom below the cyclopentadienyl ring. These complexes have been analyzed by LC/MS, elemental analysis and single crystal X-ray diffraction analysis. X-ray crystallographic analysis indicates that these half-metallocene chromium(III) complexes adopt a pseudo-octahedral coordination environment with the imine N coordinated to the Cr metal center. The ability of ethylene polymerization under different catalysis systems have been examined, the influence of different substituents, the ratio of Al/Cr and the polymerization time has been studied. Upon activation with AlR₃ (R=Me, Et and iBu) or AlR₃/Ph₃CB(C₆F₅)₄, these complexes exhibit good to high catalytic activity for catalyzed ethylene polymerization and the produced polyethylene with high molecular weight under mild conditions. The highest catalytic activity of 9120 kg PE mol Cr^-1 h^-1 and the highest molecular weight (Mη) PE of 1.14×10⁶ g mol^-1 were obtained with complex 1 activated by AlR₃, and 15600 kg PE mol Cr^-1 and the highest molecular weight (Mη) PE of 1.14×10⁶ g mol^-1 were obtained with complex 1 activated by AlR₃/Ph₃CB(C₆F₅)₄ systems. The catalytic activity of these complexes and the molecular weight of the produced polyethylene vary in a broad range with the variation in the Ar group and the AlR₃ cocatalyst. The catalyst with a bulkier Ar group shows lower catalytic activity and produces polyethylene with higher molecular weight. In addition, the AlR₃/Ph₃CB(C₆F₅)₄ activated catalyst systems show higher catalytic activity in comparison to the AlR₃ activated catalyst systems. The PE products were obtained with these catalyst systems as spherical particles while those complexes activated with AlR₃ or AlR₃/Ph3CB(C6F5)4 systems, and the property of this spherical polyethylene was depended on the complexes structure, AlR₃ and the ratio of Al/Cr.This was only a littler article have reported the Cp ring of constrained geometry metallocene chromium catalysts bearing oxygen atom, on the basis of the previous work, five oxygen functionalized constrained geometry of the chromium complexes have been synthesized according to modification with tetramethylcyclopentadienylbenzaldehyde. These complexes have been analyzed by LC/MS, elemental analysis and single crystal X-ray diffraction analysis. X-ray crystallographic analysis indicates that these half-metallocene chromium(III) complexes adopt a pseudo-octahedral coordination environment with a three-legged piano stool geometry and the O atom coordinated to the Cr metal center. The complexes was synthezied by react the lithium salt of ligand with CrCl₃(THF)₃.The ability of ethylene polymerization under different catalysis systems have been examined, the influence of different substituent, the ratio of Al/Cr and the polymerization time have been studied. Upon activation with AlR₃ these complexes exhibit moderate catalytic activity for ethylene polymerization and the produced polyethylene with high molecular weight under mild conditions. The catalytic activity of these complexes and the molecular weight of the produced polyethylene vary in a broad range with the variation in the substituent group on the bridged carbon atom and the AlR₃ cocatalyst. Upon activation with a small amount of AlR₃, all complexes show moderate catalytic activity for ethylene polymerization, producing high molecular weight polyethylene. The effects of polymerization conditions such as polymerization temperature, alkyl aluminum cocatalyst, and Al/Cr molar ratio on the catalytic activity and properties of the produced polyethylene were investigated. The strong electron withdrawing trifluomethylphenyl group introduced in the complex enhanced the activity for the ethylene polymerization. The catalytic activity of these complexes is relatively low when activated with AlMe₃ and AliBu₃. Both the catalytic activity of these catalyst systems and the molecular weight of the produced PE can be tuned in a broad range by changing the ligands and the AlR₃ cocatalyst. The life time of the catalyst is quite long, the activity of the complex did not show obvious decrease while the polymerization produced up to 2.5 hours.In chapter 5, a series of imine functionalized Fe, Co and Ni complexes have been synthesized. Those complexes have been analyzed by LC/MS, elemental analysis and single crystal X-ray diffraction analysis. X-ray crystallographic analysis indicates that these half-metallocene complexes with the N atom coordinated to the metal center. Those complexes catalyzed olefin polymerization under different AlR₃ systems have been studied.Ether-O atom modified chromium complex has been prepared and characterized by elemental analysis, and single crystal X-ray diffraction. X-ray crystallographic analysis indicates that these half-metallocene chromium(III) complexes adopt a pseudo-octahedral coordination environment with the free O atom coordinated to the Cr metal center. The ethylene, propylene, butadiene, isoprene, 1-hexene and norbornene polymerization, enthylene/1-hexene copolymerization have been studied.A new oxygen coordinated chromium complex has been synthesized and characterized by elemental analysis, NMR spectra, and single crystal X-ray diffraction...