Ethylene polymerization activity under practical conditions displayed by zirconium complexes having two phenoxy-imine chelate ligands

Ethylene polymerization using zirconium complexes having two phenoxy-imine chelate ligands was investigated at 50 and 75 degreesC at 0.9 MPa ethylene pressure. The activity of the proto-catalyst, N-[(3-t-butylsalicylidene)anilinato]zirconium(IV)-dichloride (1), decreased by increasing the polymerization temperature (50 degreesC: 1192kg-PE/mmol-Zr.h, 75 degreesC: 209kg-PE/mmol-Zr.h). The introduction of an electron donating group, such as an n-hexyl and a methoxy group. on the imine nitrogen or at the para-position of phenoxy oxygen in a benzene ring suppressed the activity decrease, however, the activity at 75 degreesC was still lower than that at 50 degreesC. The combination of an n-hexyl or a cyclohexyl group on the imine nitrogen and a methoxy group at the para-position of the phenoxy oxygen enhanced activity at 75 degreesC. Thus, N-[(3-t-butyl-5-methoxysalicylidene)-n-hexylaminato] zirconium(Iv)dichloride (5) and N-[(3-t-butyl-5 -methoxysalicylidene)cyclohexylaminato] zirconium(Iv)dichloride (6) displayed activities of greater than 1000 kg-PE/mmol-Zr.h. Moreover, the introduction of an adamantyl or a cumyl group at the position adjacent to the phenoxy oxygen further increased the activity. N-[(3-Adamantyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (7), N- [(3-cumyl-5-methoxysalicylidene)-n-hexylaminato]zirconium(IV)dichloride (8), and N-[(3-cumyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (9) displayed exceptionally high activity (7: 3052 kg-PE/mmol-Zr.h, 8: 7078 kg-PE/mmol-Zr.h, 9: 7224kg-PE/mmol-Zr.h). (C) 2001 Published by Elsevier Science B.V.