Synthesis,Characterization And Catalytic Properties Of Thiophenol Imine Vanadium And Zirconium Complexes

Polyolefins are widely used in various fields due to their easy availability of raw materials,easy processing and excellent corrosion resistance.With the development of the times,the demand for polyolefins is increasing day by day all over the world.Therefore,it is particularly important to develop new catalysts and improve the performance of polyolefins.At present,a large number of metal catalysts with salicylaldimine as a backbone have been reported,but the reports of metal catalysts supported by thiophenol-imine ligands are rather limited,which may be due to the complex synthesis of thiophenol-imine ligands and the irritating odour of thiophenol.When studying NCN pincer cobalt complexes,we found that elemental sulfur can be inserted directly into C–Co and C–Li bonds in situ forming a cobalt complex with thiophenol-imine ligand.Based on this,in this thesis a series of vanadium（III）metal complexes 1–10 and zirconium（IV）metal complexes 11–15 containing thiophenol imine ligands were synthesized by a one-pot method via inserting sulfur monomers directly between the C–Li bonds.A detailed study of these complexes was also carried out for the catalytic polymerization of ethylene.Specifically,in the third chapter of this thesis the elemental sulfur was inserted into the C–Li bonds of o-bromoimide ligand precursor to form the thiophenol-imine lithium salt 2-（Ar¹N=CH）Ar²SLi（Ar²=C₆H₄,Ar¹=2,6-Me₂C₆H₃;Ar²=C₆H₄,Ar¹=2,6-Et₂C₆H₃;Ar²=C₆H₄,Ar¹=2,6-ⁱPr₂C₆H₃;Ar²=4,6-^tBu₂C₆H₂,Ar¹=2,6-Me₂C₆H₃;Ar²=4,6-^tBu₂C₆H₂,Ar¹=2,6-ⁱPr₂C₆H₃）.A series of vanadium（III）metal complexes with thiophenol imine as ligands were synthesized by in-situ addition of a certain equiv of VCl₃（THF）₃.The above complexes were characterized in detail by elemental analysis and infrared spectroscopy.Molecular structure of 1,2,9 were confirmed by X-ray single crystal diffraction.In ethylene polymerization,all the complexes showed moderate to high activities with Et₂Al Cl as cocatalyst and Cl₃CCO₂Et as an activator affording linear polyethene with moderate molecular weight and narrow PDI distribution.The best catalytic performance was achieved with 1 as catalyst and Al/V ratio of 5000 at 50°C,and the activity up to 2.94×10⁸ g PE·（mol M）^–1·h^–1 was obtained.When the temperature was raised to 70°C,the activity decreased slightly indicating the good thermal stability of the catalyst.Besides,when the polymerization time was extended from 5 min to 180 min,the polymer obtained was increasing,and it still maintained a certain catalytic activity,indicating the life-time of the catalytic-system.In the fourth chapter of this thesis,we prepared a series of thiophenol-imine zirconium（IV）complexes[κ_N,S-（2-（Ar¹N=CH）Ar²S）]₂Zr Cl₂（Ar²=C₆H₄,Ar¹=2,6-Me₂C₆H₃（11）;Ar²=C₆H₄,Ar¹=2,6-Et₂C₆H₃（12）;Ar²=C₆H₄,Ar¹=2,6-ⁱPr₂C₆H₃（13）;Ar²=4,6-^tBu₂C₆H₂,Ar¹=2,6-Me₂C₆H₃（14）;Ar²=4,6-^tBu₂C₆H₂,Ar¹=2,6-ⁱPr₂C₆H₃（15））.All the zirconium（IV）complexes were characterized by NMR,elemental analysis,and infrared spectroscopy.All the zirconium complexes showed moderate to high activities in ethylene polymerization with MAO as cocatalyst.The highest activity was obtained with 11 at 60°C and an Al/Zr ratio of500 affording linear polyethene with medium catalytic activity and high molecular weight.