Styrene polymerization using nickel(II) complexes as catalysts

Styrene polymerization is investigated with neutral and cationic Ni(II) complexes, i.e. Ni(bipy)Me2, 1, Ni(bipy)Br2, 2, Ni(phen)Br2, 3, or Ni(Me2phen)Br2, 4, Ni(acac)2, 5, (bipy = 2,2′-bipyridine, phen = phenanthroline, Me2phen = 2,9-dimethyl-1,10-phenanthroline, acac = acetylacetonate), activated by [NHMe2Ph][B(C6F5)4] or B(C6F5)3 as cocatalysts, in the presence of AlMe3. The influence on the polystyrene features and the reaction kinetics of the nickel complex and boron activator, the Al/Ni or B/Ni molar ratios as well as the monomer concentration are studied. Catalytic systems derived from 2, 3 or 5 and [NHMe2Ph][B(C6F5)4] at a Ni:B:Al ratio of 1:1:5 are the most efficient at room temperature.