Iron Arene Complexes As Free-Radical And Cationic Photoinitiators

Evidence is presented that iron (II)-arene complexes can initiate free radical polymerization reactions with low efficiency. Oxygen appears to play a positive role; probably by oxidizing the iron (II) to an iron (III) species. Cationic curing of an epoxide by an iron-arene complex was monitored by photodifferential scanning calorimetry and again oxygen was found to play a positive role. The finding that a decomposition product of eta6-thioxanthene-eta5-cyclopentadienyliron hexafluorophosphate is thioxanth-9-one suggests that peroxyl radicals are produced during reaction.