Iron complexes of bis(oxazoline) ligand as novel catalysts for efficient atom transfer radical polymerization of styrene

A study was conducted to demonstrate that the polymerization of styrene was mediated by the bis(oxazoline)iron complexes Fe(box)Cl2 and Fe(box)Cl3 proceeds throughout a classical ATRP mechanism. Polymerization of styrene catalyzed by Fe(box)Cl2 using the 1-phenylethyl bromide (1-PEBr) initiator were carried out at 120°C under an inert atmosphere. The molecular weights (Mn) of the polystyrenes increased linearly from 3 to 26 KDa when plotted against monomer-to-initiator ratio in the range 200-1000. The iron-(II) species Fe(box)Cl2 corresponding to the reduced form of the Iron(II)/Iron(III) redox couple was fully characterized by X-ray diffraction. It was observed that the 1H NMR spectrum of the polystyrene by Fe(box)Cl3 exhibited a broad signal at 4.4 ppm and attributed to the chlorobenzylic proton of the ClCH(Ph)CH2, which was the end group of the polymer chain.