Trinuclear Fe(II)/Ni(II) complexes as catalysts for ethylene polymerizations

A new trimetallic heterotrinuclear catalyst bearing two Fe and one Ni atoms of the general formula {(2,6-C12H17)Ndouble bond; length as m-dashC–(C7H9N)[FeCl2]C–Ndouble bond; length as m-dashC–(C23H34)–C}2double bond; length as m-dashN–C–(C10H6)–Cdouble bond; length as m-dashN[NiBr2] has been synthesized successfully. For comparison, monometallic Ni(II) and bimetallic Fe(II) complexes are also investigated. When activated with methylaluminoxane or common alkyl aluminums such as ethyl aluminum sesquichloride and triethylaluminum, all catalysts polymerize ethylene with activities exceeding 105 g-PE/mol-M h bar at 30 °C. The heteronuclear trimetallic complexes showed higher catalytic activity and longer life time, especially at high temperature, than monometallic Ni(II) and homonuclear bimetallic Fe analogues, due to the cooperative effect of the neighboring metals. The molecular weight, polydispersity and the degree of branching of polyethylene were drastically influenced by the type of the metal complex and experimental parameters.