Synthesis Of ⅣB,Ⅷ Group Complexes Of Pyridine Monoimines And Their Catalystic Properties In Ethylene Oligomerization And Polymerization

In the past decade, late-transition metal complex catalysts for ethylene oligomerization and polymerization have drawn much attention. The pioneer works with diimine-based and 2,6-bis(imino)pyridyl-based cationic catalysts were the causes for this research. Driven by the industrial applications, there are many academic and industrial research laboratories engaged in exploring various complexes catalysts containing [O-N], [N-N], [N-P], and [N-N-N] ligands. This dissertation focuses on the investigation of new late-transition metal complexes for ethylene oligomerization and polymerization. A series of ligands and their corresponding late transition metal complexes were designed and successfully prepared. Upon activation with aluminum compounds, these complexes are active for ethylene oligomerization and/or polymerization. The correlation among the electronic capability of the groups on the ligand, the stereo- resistance and location of the groups were investigated, as well as the influence of polymerization conditions on their activities.Six kinds of the ester substituted pyridine monoimine ligands(L1-L6) were initially synthesized. The corresponding Fe(II) complexes Fe-1- Fe-6, Co(II) complexes Co-1-Co-6 and the Ni(II) complexes Ni-1-Ni-6 were prepared by the coordination L1-L6 with FeC-b, CoCl₂, NiCl₂. X-ray crystal determination of the six complexes verified that the geometries around the metal centers are distorted tetrahedron, square pyramid or octahedron. Employing MAO as cocatalyst, the catalytic behaviors of these complexes were tested. The results show that most of the Fe(II) complexes possess ethylene oligomerizaiton and polymerization activities simultaneously. The highest oligomerizaiton activity is 1.33x10 g·mol^-1 (Fe)·h^-1 . The selectivity for linear a-olefin(LAO) is over 97. 1 %. The Co(II) complexes display high ethylene oligomerizaiton activities with activity value up to 1.87×l0⁵ g·mol^-1(Co)·h^-1. The selectivity for LAO is over 86.5%. The highest ethylene oligomerization activity of the Ni(II) complexes is 9. 15×10⁵ g·mol^-1(Ni)·h^-1. The major oligmeric products are between C₄-C₆.At present, mostly applicable catalysts for broad MWD polyethylene are conventional high efficient supported Ti catalyst. One way to produce broad MWD PE is to use binary catalysts with two transition metal active sites. However, two kinds of active sites poison each other to lower the activity of catalyst and flexibility of hydrogen pressure control decreases therefore it is hard to control the MWD.