Synthesis Of Indenyl-Indenyl, Indenyl-Fluorenyl Zirconocene Complexes Based On3-Substituted Indenyl Group And Their Catalytic Behavior On Olefin Oligomerizations And Polymerizations

A series of zirconocene complexes were designed and synthesized, including10C1-symmetric ethylene bridged (3-substituted indenyl)(fluorenyl) zirconium complexes and4C2-symmetric ethylene bridged or non-bridged bis(3-substituted indenyl) zirconium complexes. All of them were characterized by1H NMR,13C NMR and EA (or HR-MS). The molecular structures of complexes C5and C8were further determined by X-ray single crystal diffraction. The catalytic properties of the complexes above for propylene dimerization and ethylene, styrene polymerization and copolymerization were tested. Ten ancillary directing ligands were synthesized and used for the diastereoselective synthesis of C2-symmetric bis(indenyl) zirconium complex rac-22.1. Four C1-symmetric ethylene bridged (3-pendent aryl substituted indenyl)(fluorenyl) zirconium complexes C1-C4were synthesized. They all exhibited moderate catalytic activities towards propylene dimerization to afford2-methyl-l-pentene as the major product at100℃or above. Complex C3displayed the highest dimerization activity of2.5x105g/(mol-Zr· h), and the selectivity for2-methyl-1-pentene up to97%. The main products of oligomerizations catalyzed by C4were wax-like polypropylenes with low molecule weights. The results indicated that the activities and selectivities of these complexes towards propylene dimerization were significantly influenced by the steric hindrance of pendent aryl group on the3-position of indenyl ring: a rigid bridge between aryl group and indenyl ring might lead to relative higher dimerization selectivities, in contrary, the soft bridge caused opposite results.C1-C4could also catalyze the polymerization of ethylene. The activities of these complexes were influenced by both the stetric hindrance of the pendent aryl group and the electric effect of the substitute on indenyl. Complex C3displayed the highest activity of5.5×106g/(mol-Zr-h) for ethylene polymerization. Those complexes bearing a rigid bridge between the pendent aryl group and indenyl ring, such as C1-C3, shown activity towards styrene polymerization, and the resultant polymers are syndiotactic diad enriched. However, C4bearing a soft bridge between the pendent aryl group and indenyl ring, are inactivity towards styrene polymerization. C2-C4, which are active for ethylene polymerization, could catalyze the copolymerization of ethylene and styrene, although with polyethylene as the major products.2. Six C1-symmetric ethylene bridged (3-non-aryl substituted indenyl)(fluorenyl) zirconium complexes C5～C10were synthesized. Complexes C5-C9could catalyze the dimerization of propylene at100℃or above, all except for C8produced2-methyl-2-pentene as the major product. The results indicated that the substituent of smaller steric bulkiness on3-position of indenyl might promote the higher activity towards propylene dimerization. The high selectivity towards propylene dimerization of C5-C7with pendent substituent on3-position of indenyl might be attributed to the steric repulsion between the pendent group and the growing oligomer chain. The propylene oligomerization catalyzed by complexes C8-C9was mainly a dynamic process controlled by temperature, with the increase of temperature, the selectivity towards dimerization increase and meanwhile the polymerization activity decreased.C5-C9are active for ethylene polymerization. The activities were greatly influenced by the steric hindrance of substituent on3-position of indenyl. Complexes C5and C6bearing a rigid bridge between the pendent alkyl and indenyl, shown activities towards styrene polymerization, and the resultant polymers tended to be syndiotactic. C5-C9could catalyze the copolymerization of ethylene and styrene, and the contents of styrene units in copolymer were influenced by the steric bulkiness of the substituent.3. Four C2-symmetric non-bridged or ethylene bridged bis(3-substituted indenyl) zirconium complexes C11-C13were synthesized. Complex rac-C12was further characterized by1H-1H COSY and H-’H NOESY spectroscopy to identified its structure.Cll could catalyze the oligomerization of propylene to give wax-like polymers. The composition of dimer and polymer in the product was influenced by both the steric hindrance on3-position of indenyl and the temperature. Rac-C12and C13could catalyze the dimerization of the propylene to produce2-methyl-l-pentene, the selectivity is up to>99%. The catalytic activities of all these complexes could be improved by changing the polymerization conditions.4. A series of directing ligands bearing N, S, O atoms were synthesized to assist the synthesis of C2-symmetric ethylene-bridged bis(indenyl) zirconocene diastereoselectively. Most of these directing ligands exhibited selectivity towards rac-isomer with rac:meso up to74:26. Steric hindrance and the electron effect of the donor were considered in this work. The result showed that the directing ligand had regularly small coordinating atom and bulky steric hindrance which was close to the metal center may optimize the diastereoselectivity to the rac-zirconocene.