Synthesis of Ti(IV) complexes of donor-functionalised phenoxy-imine tridentates and their evaluation in ethylene oligomerisation and polymerisation

A number of analogues of the Mitsui Chemicals ethylene trimerisation system (IV) have been explored, in which one of the donor atoms have been modified. Thus, a series of mono-anionic tridentate phenoxyimine (3-(t-butyl)-2-(OH)-C₆H₄C=N(C(CH₃)₂CH₂OMe) 1, 3-(adamantyl)-2-(OH)-C₆H₄C=N(2’-(2’’-(SMe)- C₆H₄)-C₆H₄) 2, 3-(t-butyl)-2-(OSiMe₃)-C₆H₄C=N(C(CH₃)₂CH₂OMe) 3) or phenoxy-amine (3,5-di(t-butyl)-2-(OH)-C₆H₄CH₂-N(2’-(2’’-(OMe)C₆H₄)-C₆H₄) 4) ligands have been prepared and reacted with TiCl₄ or TiCl₄(thf)₂ to give the mono-ligand complexes 5–7. The solid state structures of compounds 4–6 have been determined. Complexes 5–7 have been tested for their potential as ethylene oligomerisation/polymerisation systems in conjunction with MAO activator and benchmarked against the Mitsui phenoxyimine trimerisation system IV. While the phenoxy-amine complex 6 shows a propensity for polymer formation, the phenoxy-imine complexes 5 and 7 show somewhat increased formation of short chain LAOs. Complex 5 is selective for 1-butene in the oligomeric fraction, while 7 displays liquid phase selectivity to 1-hexene. As such 7, which is a sulfur substituted analogue of the Mitsui system IV, displays similar characteristics to the parent catalyst. However, its utility is limited by the lower activity and predominant formation of polyethylene.