Living radical polymerization of para-substituted styrenes and synthesis of styrene-based copolymers with rhenium and iron complex catalysts

Living radical polymerizations of para-substituted styrenes (p-chloro, p-methyl, p-acetoxy, p-acetoxymethyl) were examined with the ore-complex of rhenium(V) [ReO2I: ReO2I(PPh3)(2)] and half-metallocene carbonyl complexes of iron(II)[FeCpI: FeCpI(CO)(2)] and iron(I) [Fe2Cp2: Fe2Cp2(CO)(4)] (Cp cyclopentadienyl), all coupled with an iodoester initiator [(CK3)(2)C(CO2Et)I] in the presence of metal alkoxides. Living polymers with narrow molecular weight distributions (MWDs) were obtained from p-chlorostyrene (pClSt) with ReO2I and FeCpI ((M) over bar(w)/(M) over bar(n) = 1.29 and 1.09, respectively). ReO2I proved effective also for the living polymerization of p-methylstyrene (p-MeSt), while FeCpI failed, probably due to the beta-H elimination from the omega-end. In the absence of metal alkoxides, Fe2Cp2 led to living polymerization of p-acetoxystyrene (p-AcOSt) with narrow MWDs ((M) over bar(w)/(M) over bar(n) similar to 1.2) and gave long-lived poly-[p-(acetoxymethyl)styrene]. p-MeSt- and p-AcOSt- styrene block copolymers were synthesized by sequential polymerizations with ReO2I and Fe2Cp2, respectively. The recovered polystyrene with an iodine omega-end (prepared with ReO2I) efficiently initiated the living polymerization of methyl acrylate in the presence of RuCl2(PPh3)(3) to give block copolymers.