New C₁-Symmetric Ethylene-bridged Indenyl Fluorenyl Zirconium Complexes: Synthesis, Characterization And The Catalytic Behavior On The Polymerization Of α-Olefins

A series of C1-symmetric new complexes were designed and synthesized, including 9 ethylene bridged 3-substituted indenyl fluorenyl zirconium complexes and three ethylene bridged 4-substituted indenyl fluorenyl zirconium complexes. All of them were characterized by 1H NMR,13C NMR and EA or HRMS. The molecular structure of complex C2 was further determined by X-ray single crystal diffraction. The catalytic system of the complexes/methylaluminoxane (MAO) were studied for a-olefin polymerization.1. Nine new ethylene bridged 3-substituted indenyl fluorenyl zirconium complexes C1-C9 were successfully synthesized. Complexes C1-C9/MAO were used for propylene polymerization but did not produce polypropylene as expected. Further studies showed that propylene dimer was obtained. The four sterically less encumbered complexes C1, C2, C7 and C8 can catalyze the dimerization of propylene with moderate activities and complex C2 showes the highest activity of 7.06×104g converted propylene/g Zr-h. The compound of 2-methyl-1-pentene as main dimer is highest up to 98.4% for complex C8. However, the three methoxyl substituted complexes C3, C6 and C9 have no activities for propylene dimerization. The mechanism of dimerization is suggested that it is probably the phenyl on ligand coordinated to the metal center and the hemilabile structure was formed in cationic zirconium complex.2. Three new ethylene bridged 4-substituted indenyl fluorenyl zirconium complexes C10-C12 were successfully synthesized. The systems of C10-C12/MAO exhibited high isotactic selectivities on polymerization of propylene. The complex C10 with 2-methyl substituent on indenyl displayed the highest isotactic selectivity of 93.6% at the polymerization temperature of 0℃and also showed the highest activity of 7.80 x 106 g PP/mol Zr-h at the temperature of 60℃. The influence of propylene pressure and ration of Al/Zr on the catalytic performance were investigated. Meanwhile, complexes C10-C12 also were studied for ethylene homopolymerization. The complex C12 with 4-isopropyl substituent on indenyl showed the highest activity of 3.45 x 106 g PE/mol Zr-h at low Al/Zr molar ratio of 500.13C NMR and GPC data revealed that the linear structure of obtained polyethylenes with high molecular weight and broad distributions.3. Attempting to obtain PE macromonomer with high vinyl end and low molecular, substituted phenyl bridged cyclopentadienyl indenyl zirconium complexes C13-C16 and substituted phenyl bridged cyclopentadienyl fluorenyl zirconium complexes C17-C18 were studied on ethylene polymerization. It is found controlling suitable ethylene polyerization conditions, the phenyl substituted bridged cyclopentadienyl indenyl zirconium complexes C13-C16 showed high catalytic activities and high vinyl terminated group selectivities with the activation of MAO. Polyethylene macromonomer with the highest vinyl selectivity of 94.9% and Mn=8900 g/mol which fully meet the requirement of polyethylene macromonomers is from two para-methyl bridged cyclopentadienyl indenyl complex C13. The substituted bridged cyclopentadienyl fluorenyl zirconium complexes C17-C18 displayed high activities for ethylene homopolymerization with large molecular weight linear polyethylenes. Copolymerization ethylene with macromonomer was proceeded but failed.4. Three new mixed salicyladiminato substituted cyclopentadienyl zirconium complexes C20-C22 and an unsubstituted Cp complex C19 were studied on ethylene polymerization. All of the three new complexes C20-C22 showed high activities for ethylene homopolymerization with the activation of methylaluminoxane, and complex C20 showed the highest activity up to 1.15×106 g PE/mol Zr·h at 70℃. The sterically more bulky complexes C21 and C22 exhibited lower catalytic activities than the unsbustituted Cp complex C19, indicating that suitable alkyl substituent on Cp ring is benefit to catalytic activity. The 13C NMR and GPC data showed that the obtained polymer is linear polyethylene with broad distributions. The substituted Cp complexes C20-C22 can catalyzed ethylene/1-hexene copolymerization with high activities and low 1-hexene incorporation level of 0.89-1.39% but much higher molecuar weight than unsubstituted Cp complex C19.