Studies On Synthesis, Characterization And Catalysis For Olefin Polymerization Of Novel Nitrogen-Functionalized Constrained Geometry Metallocene Catalysts

Since Kaminsky and Sinn firstly discovered the highly active zirconcene dichloride/methylaluminoxane catalytic system for olefin polymerization in 1980's , intensive research work has been focused on developing new metallocene catalysts for improving catalytic activities and polymer properties. Compared with the conventional Ziegler-Natta Catalysts, the most outstanding advantages of metallocene as catalysts for olefins polymerization are that the modification of the cyclopentadienyl ligand is an effective means of optimizing the catalyst performance as well as polymer properties such as molecular weight, stereoregularity and microstructure. Up to now, various metallocene catalysts have been synthesized and widely studied both in industry and academy, and enormous special polyolefin products have been developed. Among reported metallocene catalysts, the constrained geometry metallocene catalysts have attracted particular attention because of their applications as catalysts in olefin polymerization. Among cyclopentadienyl ligands , there are a few systems where another electronical donor is appended to the five-membered ring by a side chain. If the second functionality interacts only weakly with the metal center, this system is a so-called semilabile ligand. This type of compound is of great current interest since it is possible to modify the properties of organometallic catalysts for stereoselective synthesis. Amines can serve only as donor units; in many cases they interact only weakly or not at all with transition metal centers.The coordination can be improved by using aromatic amines ,especially when they are part of a chelating system.There are several examples where an amine or a pyridyl unit is fixed to a cyclopentadiene. To ensure good chelating properties,a C2 or a C3 moiety between the nitrogen atom and cyclopentadiene is required . If the spacer is an alkyl chain, several conformations are possible due to its flexibility. The molecule can only act as a chelating ligand when it adopts a suitable conformation. If the donor group does not interact with the metal, the "side arm"moves freely and the compounds are often obtained as liquids of non-crystalline solids .The interesting feature of this system is the fact that the C2 spacer between the nitrogen atom and the cyclopentadienyl is fixed in the planar heterocyclic ring system. Therefore only rotation about one carbon-carbon bond is possible. Based on the aforementioned reasons, in chapter three, I attached great importance to the contents as follows:I synthesized three ligands by introducing N,N-dimethylaniline into the 3,4-diphenylcyclopent-2-enone, 2,3,4,5-tetra -methylcyclopent-2-enone and 6,6-dimetylfulvene,which are 1-(2-N, N-dimethyl-aminophenyl)-2,3,4,5-tetramethylcyclopentadiene(I), 1-(2-N,N-dimethyl-aminophenyl)-3,4-diphenylcyclopentadiene (II) and 1-(2-N,N-...