Radical Coordination Chemistry and Its Relevance to Metal‐Mediated Radical Polymerization

The reactions engaged by organic radicals with transition‐metal complexes are reviewed with a particular focus on how they can interplay with and affect the results of radical polymerization. Radicals can either add to a metal centre to establish metal–carbon bonds, abstract an atom or group, be abstracted by an atom or group, undergo associative exchange, transfer a β‐H atom or add to existing ligands in the metal coordination sphere. Reversibility is key for certain controlled polymerization methods. The various ways in which metal complexes can play a role in radical polymerization lead to atom‐transfer radical polymerization (ATRP), organometallic‐mediated radical polymerization by either reversible termination (OMRP‐RT) or degenerative transfer (OMRP‐DT) and chain‐transfer‐catalysed radical polymerization (CTCRP).