Iron—arene complexes as free radical and cationic photoinitiators

Abstract

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 η 6-thioxanthene-η 5-cyclopentadienyliron hexafluorophosphate is thioxanth-9-one suggests that peroxyl radicals are produced during reaction.