Radical chemistry of iron carbonyls

It is shown that catalytic carbonylation of various compounds using iron carbonyl complexes is based on two types of reactions [redox disproportionation of iron carbonyl induced by Lewis bases and oxidative addition of Brønsted and Lewis acids to (hydrido)carbonylferrate anions] comprising single-electron initiation steps and subsequent radical chain reactions. The role of iron carbonyl radical anions as catalysts for carbonylation processes with controlled reduction potential of the medium is noted. Characteristic features of the radical chemistry of iron and other transition metal carbonyls is analysed.