Novel Group Ⅳ And Group Ⅵ Metal Catalysts For Olefin Polymerization

In this dissertation, a serial of half-sandwich titanium and half-sandwich chromium and zirconium complexes containing salicylbenzoxazole and salicylbenzothiazole [N,O] ligands; titanium complexes bearing new pyrrolide-benzoxazole ligands; nickel(II) and palladium(II) complexes based on new tridentate [N-NP] and [N-NS] ligands were synthesized and tested for olefin polymerization. The full dissertation was summarized as follows:1. A serials of salicylbenzoxazole and salicylbenzothiazole ligands were synthesized by using substituted salicylaldehyde, o-aminophenol and o-aminothiophenol, et al. Seven novel half-sandwich titanium complexes have been synthesized by the reaction of CpTiCl3with the corresponding lithium or sodium salts of salicylbenzoxazole and salicylbenzothiazole ligands in a1:1molar ratio in THF at-78℃. Single crystal X-ray analysis of two complexes has shown that the complexes adopt three-legged piano stool geometry with a pseudo-octahedral coordination environment. In the presence of MAO as co-catalyst, all the half-sandwich titanium complexes showed moderate to high activities (up to2.57×105g PE mol-1Ti h-1) for ethylene polymerization at1bar and produced high molecular weight polyethylenes (2.96-24.11×105g mol-1). When a suitable steric hindrance is in ortho-position of the phenoxy, higher activities can be obtained. However, when the para-position of the phenoxy is a chlorine atom, which is an electron-withdrawing group, complex show reduced activity for ethylene polymerization.2. Reaction of TiCl4or ZrCl4with the corresponding lithium or sodium salts of salicylbenzoxazole and salicylbenzothiazole ligands, which have large steric hindrance, resulted in the formation of three titanium and eleven zirconium complexes. A pseudo-octahedral coordination environment of the metal complexes is determined by single crystal X-ray diffraction methods. Upon activation with methylaluminoxane (MAO), the zirconium complexes bearing a bulky substitute on the ortho-position of the phenol ring show high activities for ethylene polymerization and produced high molecular weight polyethylenes, while for the titanium complexes, only trace polymers were obtained. 3. Twelve novel half-sandwich chromium(Ⅲ) complexes bearing salicylbenzoxazole and salicylbenzothiazole ligands have been synthesized by the reaction of CpCrCl2(THF) with the corresponding sodium salts of the salicylbenzoxazole and salicylbenzothiazole ligands in THF at-78℃. The molecular structures of two complexes have been confirmed by single crystal X-ray analysis. Upon activation with a small amount of AlEt3, half-sandwich chromium(Ⅲ) complexes bearing salicylbenzoxazole and salicylbenzothiazole ligands can produce high molecular weight PE (3.57-9.27×105g mol-1) with good activity (10.36×105g PE mol-1Crh-1(mol/L ethylene)-1) under mild conditions. It has been proved that introduction of a bulky group on the ortho-position and an electron-donating group on the para-position of phenol ring in the ligands has a positive influence to the catalytic activity.4. Four new pyrrolide-benzoxazole ligands were synthesized by using pyrrole-2-carbaldehyde and substituent o-aminophenol, and their titanium complexes were also synthesized. Five titanium complexes were obtained and three complexes have been confirmed by single crystal X-ray analysis. After being activated with methylaluminoxane (MAO), all the titanium complexes could polymerize ethylene with high catalytic activities at high pressure and produce polymers with high molecular weight.5. A serials of novel anilido-imine [N-NP] and [N-NS] tridentate nickel and palladium complexes were synthesized and three of them have been confirmed by single crystal X-ray analysis. Molecular structure analyses of these complexes reveal that the coordinated atoms and the nickel centers are almost coplanar. After activated with methylaluminoxane (MAO), the nickel complexes can be used as efficient catalysts for norbornene polymerization to produce vinyl addition-type polynorbornene (6.02-7.67×105g mol-1) with high catalytic activities up to5.82×107g PNB mol-1Ni h-1, while poor catalytic activities for the palladium complexes.