Iron(II) Chloride Complex for Living Radical Polymerization of Methyl Methacrylate1

TLDR: In this article, it was shown that the Fe(II) complex is effective in the homolytic and reversible cleavage of the carbon−halogen terminal originating from the halide initiators into a transient radical growing species to induce living MMA polymerization.

Abstract: Iron(II) bis(triphenylphosphine)dichloride [FeCl2(PPh3)2] induced living radical polymerization of methyl methacrylate (MMA) in conjunction with organic halides as initiators [R−X:  CCl4, CHCl2COPh, (CH3)2CBrCO2C2H5, and CH3CBr(CO2C2H5)2] in the absence or presence of Al(OiPr)3 in toluene at 80 °C. The added aluminum compounds were not needed for the Fe(II)-mediated living polymerization unlike the RuCl2(PPh3)3-based counterpart. With CH3CBr(CO2C2H5)2 as initiator, the number-average molecular weights of polymers increased in direct proportion to monomer conversion, and the MWDs were narrow throughout the reactions (Mw/Mn = 1.1−1.3). The polymers possessed one initiator moiety at the α-end per one polymer chain. The tacticity was similar to that prepared by AIBN. These results indicate that the Fe(II) complex is effective in the homolytic and reversible cleavage of the carbon−halogen terminal originating from the halide initiators into a transient radical growing species to induce living MMA polymerization.