Bidentate [N, N] nickel complexes with salen type ligands for polymerization of methyl methacrylate RAPID COMMUNICATION Summary-Nickel complexes with bidentate [N,N] salen type ligands activated by different organoaluminium compounds, within which methylalumoxane (MAO) turned out to be the best, were studied in methyl methacrylate (MMA) polymerization. Activity of the investigated complexes was found to increase with increasing Al/Ni molar ratio. The studied catalytic systems were found to produce high molecular weight (Mw = 280 000-560 000) poly(methyl methacrylate) (PMMA) with rich syndiotactic microstructure. Activity of the catalyst as well as Mw and glass transition temperature (Tg) of poly(methyl methacrylate) (PMMA) are dependent on polymerization temperature and they reach maximum values for reaction temperature about 30 o C.