Atom-transfer radical polymerization by a recycable iron-amine catalyst

A trinuclear iron(II) catalyst (1) is found to be a good catalyst for well-controlled atom-transfer radical polymerization (ATRP) of styrene, whereas an mononuclear iron (III) catalyst (2) is effective for well-controlled reverse-ATRP of MMA initiated by AIBN. The formed polymers have a terminal chloride, which is useful for post-polymerization to form block-copolymers. The iron species can be removed from the formed polymers by precipitation of the polymer from methanol, and the iron species recovered can be reusable for ATRP. ¹H NMR spectrum of the recovered iron species from ATRP of styrene suggested to be identical with the initial iron compound 1; the recovered iron catalyst can be recycled for at least five runs of ATRP of styrene.