Poisoning effect of CO on ethylene polymerization with Ni(II)-diimine/MAO

CO was not a comonomer but an inhibitor in ethylene polymerization catalyzed over [1,2-bis(2,6-diisopropylphenylimino)]acenaphthene nickel(II) dibromide (1)/MAO. The average number of active sites, [C¯*], and the average rate constant for chain propagation, k¯p of the (1)/MAO system was determined using CO inhibition method based on the assumption that two molecules of CO coordinate to each active center. At 0 °C, the average number of active centers, C¯*, was increased with the Al/Ni ratio, and k¯p, was not influenced by the Al/Ni ratio. Up to Al/Ni ratio of 3000, the average number of active sites was saturated. Single active site was present at the high ratio of Al/Ni and its reactivity with CO is uniform at 0 °C. The maximum average activity was 5262.07 (kg-PE/mol-Ni/atm/hr) and 65.7% of (1) was converted to form active cation complexes at 0 °C and Al/Ni molar ratio of 5000, while 36.5% of (1) was activated at the Al/Ni molar ratio of 250. Above 30 °C, the complicated CO poisoning behavior was observed because the reactivity and stoichiometry of active centers with CO were not uniform and their thermal stability was very poor.