Ethylene polymerization in supercritical carbon dioxide with binuclear nickel(II) catalysts.

A series of new, highly fluorinated neutral (kappa(2)-N,O) chelated Ni(II) binuclear complexes based on salicylaldimines bridged in p-position of the N-aryl group were prepared. The complexes are single-component catalyst precursors for ethylene polymerization in supercritical carbon dioxide and toluene. Solubility of the catalyst precursors in supercritical carbon dioxide is effected by a large number of up to 18 trifluoromethyl groups per molecule. Semicrystalline polyethylene with a low degree of branching is formed (ca. 10 branches/1000 carbon atoms). Polymer microstructures are independent of the nature of the bridging moiety, while stability of the catalysts appears to differ.