Synthesis,Catalytic Ethylene Polymerization Of Multidentate Aminophenolate Titanium,Zirconium Complexes And Synthesis Of Ansa-bis (3-chiral Group Substituted Indenyl) Zirconium Complexes

Twenty three titanium （IV） and zirconium （IV） complexes supported by aminophenolate ligands containing aryl ether or aryl or aminoaryl as the pendant group and ethylene dimethylamine or ethylene ether as the side chain, and two ansa-bis（3-chiral group substituted indenyl） zirconocene complexes were synthesized and fully characterized by NMR spectroscopy and elemental analyses （or HRMS）. The molecular structures of seven typical complexes were further determined by X-ray single crystal diffraction studies. With MMAO as cocatalyst,the catalytic behavior of the aminophenolate titanium and zirconium complexes for ethylene polymerization was also investigated in detail.Titanium and zirconium complexes T1-T4, T7-T10 and Z8 bearing [ONNO]-type aminophenolate ligands with aryl ether as the pendant group and ethylene dimethylamine as the side chain, were prepared from the reaction of TiCl₄（THF）₂ or ZiCl₄（THF）₂ and one equivalent of aminophenol proligands L1-11H in the presence of triethylamine in moderate yields. The tridentate, cis-chelating mode of the multidentate aminophenolate ligand in these complexes was further confirmed by the X-ray diffraction studies of typical complexes T2,T9, and T8b, where only the phenoxy oxygen, two nitrogen donors of the ligand coordinate with the metal center and the pendant aryl ether moiety the ligand is located far away from the metal center. These complexes have a cis-, C1-symmetrical octahedral configuration around the metal center in the solid state. In solution, there exist two kinds of configurational isomers（cis-, and trans-）, with the cis-isomer dominant. Upon activation with MMAO, titanium complexes T1-4, T7-10 and zirconium Z8 are moderately to highly active for ethylene polymerization at high temperature of 120 ℃, resulting in linear polyethylenes with high molecular weights and molecular weight distributions. The steric and electronic effects of the substituents on the ortho- and para-positions of phenolate ring of the ligand have significant influence on the catalytic activities of the complexes. The introduction of electron withdrawing halo groups on ortho- and para- positions of phenolate ring increases the catalytic activity and substituents of moderately steric bulkiness are beneficial to the activity.Complex T8 with bromo groups on the ortho- and para- positions of phenolate ring showed the highest catalytic activity of 1.55 × 107 g/（mol-Ti h） at 120 ℃,resulting in linear polyethylenes with Mη =63～407 kg/mol and very wide molecular weight distributions（Mw/Mn = 10.2～16.8）. The catalytic activity of these series of titanium complexes increases consistently with increasing polymerization temperature. High activity was obtained even at 160 ℃, proving that complex T8 has excellent thermal stability. Zirconium complex Z8 displayed lower thermal stability than titanium analogues, and showed the highest activity at 80 ℃. With the increase of Al/Ti molar ratio, the increase of the catalytic activity of the complexes and the decrease of the molecular weight of the resultant polymers could be observed in all cases. On the basis of a polymer end group analysis, the dominant chain transfer reaction in ethylene polymerization catalyzed by these complexes is suggested to be a chain transfer to the aluminum center.Using [ONN]-type aminophenol proligands L12-16H,six titanium and zirconium complexes T12-T16, Z14 bearing aminophenolate ligands with phenyl or o-fluorophenyl as the pendant group and ethylene dimethylamine as the side chain,were prepared via the same strategy. By comparing their 1H NMR spectra with those of complexes reported above, two kinds of configurational isomers, cis- and tranw-isomers, are conceivable for complexes T12-T16, and the cis-isomer is suggested to be dominant in solution. With MMAO as cocatalyst, complexes T12-T16 could catalyze the polymerization of ethylene with moderate to high activities. Complexes T12 and T13 bearing pendant phenyl group are superior to complexes T14-T16 bearing pendant o-fluorophenyl in thermal stability and catalytic activity.Among them, complex T12 showed good thermal stability and a long life time, and high activities could be reached at high Al/Ti ratios. At 120 0C,Al/Ti = 10000, after one hour’s polymerization, the activity of complex T12 was still up to 1.00 × 106 g/（mol-Ti·h）, and linear polyethylenes with ultra-high molecular weight were resulted.Using [ONNN]-type aminophenol proligand L17-22 H, six titanium complexes T17-T22 bearing aminophenolate ligands with aminoaryl as the pendant group and ethylene dimethylamine as the side chain,were prepared by the same procedures. The structures of these complexes are similar to those of complexes reported in the previous two chapters and was confirmed by X-ray diffraction study of complex T17, where the aromatic nitrogen atom in the pendant group of the ligand does not coordinate with the metal center and the ligand coordinates to titanium metal center in a tridentate cis-fashion in the solid state. Complexes T17-T22 were found to be active for catalytic ethylene polymerization with moderate activities, resulting in linear polyethylene with high molecular weight and broad molecular weight distributions （typically, Mw/Mn = 5.9）. Similarly, increasing the steric hindrance of substituents on the ortho- and para- positions of phenolate ring of the ligand lead to first an increase then a decrease of the activity. This series of complexes show poor thermal stability and their maximum activities were reached at 50 ℃. The increase of Al/Ti molar ratio also leads to an increase of the catalytic activity of the complexes and a decrease of the molecular weight of the resultant polymers.Three titanium complexes T23,T25 and T26 bearing [ONNX]-type aminophenolate ligands with aryl ether or aminoaryl as the pendant group and ethylene ether as the side chain,were prepared from the reaction of TiCl₄ and one equivalent of the aminophenol proligands L23-26H in relatively low yields. The ligand coordinates to the titanium metal center in a tridentate trans-fashion as confirmed by the X-ray diffraction studies of complexes T23 and T26. The methoxy or dimethylamine attached on the phenyl moiety of the ligand does not coordinate with the metal center in the solid state. Complex T25 with chloro substituted at the ortho- and para-positions of the phenolate ring shows a fluxional structure. Upon activation with MMAO, complexes T23, T25-T26 were found to be active for ethylene polymerization with moderate to high activities, resulting in linear high molecular weight polyethylene. With a fluxional structure, complex T25 showed significantly higher activity than complexes T23 and T26, as well as better thermal stability and a longer life time. At 80 ℃, Al/Ti = 10000,after one hour’s polymerization, the activity of complex T25 was still up to 1.42 × 106 g/（mol-Ti·h）, and liner polyethylene with ultra-high molecular weight and wide molecular weight distribution（Mw/Mn = 10.2） could be obtained. Furthermore, with the increase of Al/Ti ratio, an increase of activity and a decrease of the molecular weight of resultant polymer could be observed for T25.Due to the excellent controllability of metallocene catalysts in olefin polymerization, the synthesis of chiral metallocene complexes were also carried out. Ethylene or methylene bridged bis（indenyl） compounds L29-31H2 bearing chiral substituent were obtained by introducing （+）-neomenthyl or （+）-isocamphyl to the 3-position of indenyl ring. Two C2-symmetric ethylene bridged bis（indenyl） zirconium complexes R,R-Z30 and R,R-Z31 were isolated readily from the reaction of the dilithium salts of these compounds with zirconium tetrachloride. The purification of corresponding meso-like, C1-symmetric complexes meso-like-Z30 and meso-like-Z31 was however not successful. All of the proligand compounds and zirconium complexes have been characterized by 1H NMR,13CNMR spectra and elemental analysis （or HRMS）. The molecular structure of meso-like-Z30 was further determined by the X-ray single crystal diffraction analysis.