Roles α-diimine iron catalysts play

• Iron is inexpensive, environmentally benign and has an accessible Fe^II/Fe^III redox couple
• ATRP: Atom transfer radical polymerisation, radicals are generated via a reversible redox process initiated by an alkyl halide, forming a metal halogen bond.
• OMRP: Organometallic mediated radical polymerisation, involving equilibrium trapping of a radical to form a metal-C bond.
• CCT: Catalytic chain transfer; low molecular weight polymer generation via β-hydrogen elimination of a growing chain
• The simultaneous competition between these equilibria establishes the polymer characteristics.