Radical Polymerization Reaction of Styrene Catalyzed by β-Aminoketonato Complex of Iron

beta-Aminoketone (1-H) was prepared by the reaction between acetylacetone and N, N-diethylethylenediamine. Divalent iron complexes (2) bearing monoanionic tridentate beta-aminoketonato and halide ligands were prepared by the reaction of FeX(2) (X = Cl, Br) with the Li (beta-aminoketonato) (1-Li), which was generated by the reaction of 1-H with n-BuLi in situ. The X-ray analyses of iron complexes revealed that the iron fragment containing the beta-aminoketonato ligand has a planar geometry. Radical polymerization of styrene catalyzed by the iron complex (2) coupled with a halide initiator was examined. The influence of halogen atoms contained in the iron complex and/or in the initiator on the polymerization of styrene was investigated. The combination of the iron complex 2-Br and (1-bromoethyl) benzene (1-PEBr) as an initiator was found to be an efficient catalyst for the controlled radical polymerization of styrene. The linear correlation between the conversion and the molecular weight of the polymer in the polymerization of styrene catalyzed by 2-Br with 1-PEBr was observed. The macroinitiator isolated from the polymerization of styrene mediated by this system also polymerized styrene to give polystyrene with a larger molecular weight than that of the macroinitiator itself.