Iron(II) chloride

Iron (II) chloride (Ferrofloc) is an active radical polymerization initiator, which is a transition metal chloride composed of Fe²⁺ and Cl⁻ ions. The ion association constant log_KFeCl2 of Iron (II) chloride is −0.89. In acidic aqueous solutions, Iron (II) chloride forms solvated Fe²⁺+2Cl⁻ ions as well as FeCl⁺+Cl⁻ ion pairs. Without the addition of aluminum compounds, Iron (II) chloride drives the living radical polymerization of methyl methacrylate by generating transient radical growing species through homolytic reversible cleavage of the carbon-halogen end groups of organic halide initiators^[1][2].