Synthesis And Structural Characterization Of Novel Schiff-base Iron(Ⅱ) And Cobalt(Ⅱ) Complexes And Their Catalytic Behavior In Ethylene Oligomerization

In 1998, M. Brookhart group in American and V. C. Gibson group in England who demonstrated that N N N tridentate bis(imino)pyridyliron complexes showed high activity of ethylene oligomerization( > 10⁷g·mol^-1·h^-1), and the oligomers consist of > 95% linear a-olefins. Henceforth, the iron complexes for ethylene oligomerization and polymerization have attracted much attention in organometallic chemists, not only because of their high catalytic activities, but also because of their nontoxic properties.With rapid growth of petroleum chemical lines and great demands of linear a-olefins in china, linear a-olefins were obtained by catalytic ethylene oligomerization of catalysts, while excellent catalysts are protected by foreign potent, moreover,we must design and exploit new catalysts that belong to our country and act on our own interllectural property rights. Most recent, W.-H. Sun group reported the synthesis of 2-imino-l,10-phenanthrolinyl ligands and the high catalytic activities for ethylene oligomerization exhibited by their metal complexes. For the thesis basised on its work, ortho-6-heterocycle-2-iminopyridine derivatives would be our desired compounds which provide tridentate ligand in coordination with iron and cobalt halides. Three main parts are included in this dissertation:Part 1: The recent advances catalysts in the ethylene oligomerization and main in late transition metal catalysts have been reviewed.Part 2: A series of 2-quinoxalinyl-6-iminopyridine compounds (L1-L7) were designed and synthesized as alternative N^{^}N^{^}N tridentate ligands in their metal complexes, and the iron(â…¡) and cobalt(â…¡) complexes, LFeCl₂ (1-7) and LCoCl₂(8-14), were synthesized by the reaction of 2-quinoxalinyl-6-iminopyridines with metal chlorides. These compounds were characterized by elemental and spectroscopic analyses along with X-ray diffraction analysis. The metal complexes display distorted trigonal-bipyramidal geometry at the metal centers. Upon activation with methylaluminoxane (MAO), all these complexes are highly active for ethylene oligomerization with the dimmers and trimers of ethylene as the main products. The catalytic activities of these complexes were investigated by varying the structures of the complexes or reaction conditions.Part 3: 2,9-Diformyl-l,10-phenanthrolinebis(2,6-dimethylanlil) cobalt(II) per chlorate was synthesized and demonstrated to be [CoLzJtClO^by X-ray diffraction analysis. It crystallizes in the monoclinic system, space group C2Jc with a = 22.294(4), b = 15.122(3), c = 20.640(4) A, a=y= 90a, fi = 119.618(4)°, the final R = 0.0651 and wR = 0.1373 for 1734 observed reflections (/ > 2o(/)). In solid state the helical polymeric chains are supramolecularly associated through intermolecular and inter-ionic hydrogen bonding interactions.