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Aminoiminate metal complexes: Novel catalysts for alpha-olefin polymerizations
Two series of aminoiminate compounds, the aminotroponimines (ATI) and the β-iminoamines (β-IAM), were synthesized and used for the design of new catalysts for α-olefin polymerizations. The obtained aminoirninate complexes of titanium and zirconium were found to be highly active catalysts for ethylene polymerization. In contrast, the amimoiminate palladium complexes were inactive in ethylene polymerization. A novel and simple route has been developed to prepare a series of N,N ′-dialkyl aminotroponimine compounds and one β-iminoamine compound, N,N′-diphenyl-β-IAM. During the titanium metallation of a bulky N,N′-di(2,6-diisopropylphenyl)-β-IAM compound, the β-IAM was found to be dimerized to produce a potential ligand for the dimetallic complex. A series of β-IAM-Zr complexes were successfully synthesized through simple reactions between deprotonated b-IAM and ZrCl4·2THR. The ATI-Zr, ATI-Ti and β-IAM-Ti complexes were obtained from the amine elimination reaction of dimethylamino metal complexes with the aminoimine compounds. The β-IAM palladium complexes were prepared through the reactions between deprotonated β-IAM and (COD)Pd(Me)CI. A Full structure analysis of a β-IAM-Zr complex was achieved through X-ray analysis. Activated by methyl aluminoxane, all of the aminoirninate titanium and zirconium complexes are active catalysts. The activity of the ATI-Zr complex is close to that of the β-IAM-Zr complexes and the β-IAM titanium catalysts are more active than their zirconium analogues. The molecular weight distribution of polyethylene from aminoirninate Zr complexes is trimodal. In contrast, the polymer from titanium catalyst is close to a single mode distribution. Steric factors appear to be the over-ridding criteria in determining both of the activities of the β-IAM-Zr catalysts and molecular weight distribution of the obtained polyethylene. The steric crowding of the ligands decreases the polymerization activities and increases the molecular weight dispersities. The β-IAM zirconium catalysts are very stable and maintain constant activities during polymerization for long time periods. Polymerization temperature, solvents and catalyst/cocatalyst ratio strongly affect the polymerization activities of zirconium and titanium catalysts. The NMR and DSC studies indicate that chain-transfer to aluminum is the predominant chain termination reaction. The β-IAM Zr and Ti complexes are also active for propylene and 1-hexene polymerization; however, the activities are much lower than ethylene polymerization.
Jin, Xin, "Aminoiminate metal complexes: Novel catalysts for alpha-olefin polymerizations" (2000). Doctoral Dissertations Available from Proquest. AAI9988801.