Novel Polyethylenes via Late Transition Metal Complex Pre-catalysts

Abstract

Late-transition metal complex pre-catalysts provide alternative promising catalytic systems for ethylene oligomerization and/or polymerization. Ethylene oligomerization using either iron or cobalt complex pre-catalysts is recognized as one of most active catalytic systems with high selectivity for α-olefins (up to 99%). New characteristic features are observed for the polyethylenes obtained from such late-transition metal catalytic systems. Highly linear polyethylene is usually obtained using the iron or cobalt complex pre-catalysts, whereas highly branched polyethylene is commonly formed by the nickel or palladium complex pre-catalysts. The causes for production of linear or branched polyethylenes are briefly explained according to the polymerization mechanism. Driven by demanding for new promising catalytic processes, the discussion is divided on the basis of models of complex pre-catalysts: a section on iron and cobalt complexes and another section on nickel and palladium complexes. The iron and nickel complex pre-catalysts receive more attention due to the relatively cheap and low toxicity metals from which they are derived.