A new series of penta-coordinated Co(III)-, Fe(III)-, and Cr(III)- complexes (6–10) bearing N-salicylidineisopropylaniline and sodium N-(4-sulfonitsalicylidineisopropyl-aniline) ligands has been synthesized and utilized, after activation with methyl aluminoxane, as catalysts for the polymerization of tert-butylacrylate (t-BA). High molar mass P(t-BA) polymers with very low molecular weight distributions were produced (M w/M n = 1.06–1.09). Cobalt- and chromium-based precatalysts showed higher activity towards the polymerization reaction than those of the iron complexes. The presence of sulfonated groups on the para position of the aryl group in the backbone of the ligand decreases the catalytic activity of the complexes. The ortho alkyl substituents on the aryl groups of the ligand have a favorable influence on the polymerization activity compared to the alkyl-free analogue (11).