Spin trapping of radicals formed during the photolysis of the dimeric iron carbonyl complexes [η 5-C 5H 5)Fe(CO) 2] 2 and [(η 5-C 5Me 5)Fe(CO) 2] 2

Abstract

The generation of free radicals by photolysis of dimeric iron complexes [(η 5-C 5H 5)Fe(CO) 2] 2 and [(η 5-C 5Me 5)Fe(CO) 2] 2 has been studied by EPR and spin trapping. Unlike [(η 5-C 5H 5)Fe(CO) 2] 2, no evidence for homolytic C 5Me 5Fe cleavage was found for [(η 5-C 5Me 5)Fe(CO) 2] 2. Photolytic scission of the FeFe bond appears to be the dominating free radical process in both complexes. The resulting iron-centered free radicals react readily with dioxygen to form iron peroxyl radicals which may abstract hydrogen from CH bonds. In addition, electron transfer has been observed between photoexcited [(η 5-C 5Me 5)Fe(CO) 2] 2 and the spin trap 2-methyl-2-nitrosopropane, which leads to a variety of secondary radicals. Unlike the situation with monohalocarbons, no carbon-centered radicals were detected when the photolysis was carried out in CCl 4 and CFCl 3, respectively.