Synthesis Of Transition Mental Complexes Containing β-Hydroxy Imino Ligands And Their Catalysis For Olefin Polymerizations

A series of novel transition metal complexes Ti/Ni containingβ-hydroxy imino ligands were synthesized successfully. With titanium complexes/MAO as catalyst systems, the polymerization of ethylene was investigated.Firstly,β-hydroxy imino ligands L1, L2 and L3 were synthesized as follows: 2,6-diisopropyl aniline reacted with acetophenone to form imine precursor PhMeC=N(2,6-iPr2C6H3) in addition to water by acid catalyzed. PhMeC=N(2,6-iPr2C6H3) reacted with LDA to form [PhCH2C=N(2,6-iPr2C6H3)]-Li+. Then [PhCH2C=N(2,6-iPr2C6H3)]-Li+ reacted with benzaldehyde, diphenyl ketone and fluorenone to formβ-hydroxy imino ligands. The structures of them were characterized by 1H NMR, IR and MS.Secondly,β-hydroxy imino ligands L1, L2 and L3 reacted with 2:1 equivalent of TiCl4 toluene solution to form bis-ligated complexes (C1, C2 and C3); reacted with 1:1 equivalent of TiCl4 toluene solution to form mono-ligated complexes (C4, C5 and C6). The structures of C1, C2, C4 and C5 were characterized by 1H NMR, IR and MS-ESI.Finally, the polymerization of ethylene was investigated with C2/MAO as catalyst system, the C2 complex showed good activity for ethylene polymerization. The best polymerization conditions:polymerization temperature 45℃, polymerization pressure 2.7MPa, reactiont time 0.5h, Al/Ti=150, catalyst 20μmol, and with 40mL toluene. The obtained PE was ultra high molecular weight polyethylene from the datas of DSC and viscosity average molecular weight. With moderate steric substituent in theβ-crbon, the complex/MAO gave the highest catalytic activity on polymerization of ethylene of reaching 3.9×104gPE·mol-1Ti·h-1, and provided the hightest molecular weight Mηis 2.15×106.Moreover, mono-ligated nickel complexes (C7, C8 and C9) were tried to prepared by the reaction ofβ-hydroxy imino ligands (L1,L2 and L3) with trans-Ni(Ph)(Cl)(PPh3)2. But the result is not very satisfactory, further study was needed.