Atom transfer radical polymerization (ATRP) catalyzed by high oxidation state metal salts of FeX3 is developed for the first time in the absence of both external initiator and reducing agent. Methyl methacrylate (MMA) and styrene are polymerized successfully using FeX3/Phosphorous ligands with well‐controlled molecular weight distributions (=1.5). The molecular weight of the polymers increases with monomer consumption with the progress of time and the polymerization behaviors show a decent ATRP trend. Activators and initiators are suggested to generate in situ by the addition reaction of MMA and one equivalent of FeX3. The PMMA synthesized from without‐initiator system is characterized by 1H, 13C and DEPT (distortionless enhancement by polarization transfer nuclear magnetic resonance) nuclear magnetic resonance spectroscopy. Chain extension and copolymerization experiments prove the livingness of the obtained polymer.
