Very Active Neutral P,O-Chelated Nickel Catalysts for Ethylene Polymerization

A series of highly active nickel-based neutral catalysts for ethylene polymerization is presented. These catalysts are obtained by direct complexation of simple fluorinated ketoylides onto bis(1,5-cyclooctadiene)nickel. Catalyst formation readily occurs in the presence of an olefin, but due to the electron deficiency of the ligand, it hardly happens in the absence of an olefin or another Lewis base. Activities greater than 2 × 106 (gPE/gNi)/h and productivities higher than 15 × 106 gPE/molNi are typically observed. These catalysts are also active for the polymerization of α-olefins such as 1-hexene and 1-propene. Polymer characterization indicates that highly linear, low molecular weight PEHD is formed by these complexes.