Bis(imino)pyridyl iron and cobalt complexes: the effect of nitrogen substituents on ethylene oligomerisation and polymerisation

The synthesis and characterisation of 2,6-bis(imino)pyridyl iron and cobalt complexes [(2,6-(RN=CMe)(2)C5H3N)MCl2] containing nitrogen substituents of the type R=NPh2, NPhMe, NMe2 or 2,5-dimethylpyrrolyl are described. These complexes, in combination with the co-catalyst MAO, give active catalysts f or the oligomerisation or polymerisation of ethylene. The catalytic activit y is strongly affected by the substituents R and the polymerisation conditi ons used. The polymer properties are also a function of the R substituents. With R=NPhMe or NMe2, toluene soluble alpha -olefins are obtained, whereas the bulkier substituents (R=NPh2 or 2,5-dimethylpyrrolyl) give low molecul ar weight solid polyethylene.