γ-Diimine palladium(II) based complexes mediated polymerization of methyl methacrylate

The synthesis of new palladium(II) complexes of the type [Pd(A–NC–ph–CN–A)Cl2] (4a–e) (A=cyclohexyl (a), 2-isoprpropyl (b), pyrenyl (c), naphthyl (d), and 2,6-diisopropyl (e)) is described. The isolated γ-diimine ligands and their corresponding palladium(II) complexes were characterized by their physical properties, elemental analysis, 1H NMR-, 13C NMR, and infrared spectroscopy. The palladium(II) complexes (4a–e) were employed successfully as catalysts for atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in the presence of ethyl-2-bromoisobutyrate (EBIB) as initiator at 90°C. Polymerization with these catalyst systems afforded polymers with low molecular weight distribution (Mw/Mn) and syndio-rich atactic poly (MMA) with relatively higher [rr] diads.