Between imide, imidyl and nitrene - an imido iron complex in two oxidation states

Imidyl and nitrene metal species play an important role in the N-functionalisation of unreactive C-H bonds as well as the aziridination of olefines. We report on the synthesis of the trigonal imido iron complexes [Fe(NMes)L-2](0,-) (L = -N{Dipp}SiMe3); Dipp = 2,6-diisopropyl-phenyl; Mes = (2,4,6-trimethylphenyl) via reaction of mesityl azide (MesN(3)) with the linear iron precursors [FeL2](0,-). UV-vis-, EPR-, Fe-57 Mossbauer spectroscopy, magnetometry, and computational methods suggest for the reduced form an electronic structure as a ferromagnetically coupled iron(ii) imidyl radical, whereas oxidation leads to mixed iron(iii) imidyl and electrophilic iron(ii) nitrene character. Reactivity studies show that both complexes are capable of H atom abstraction from C-H bonds. Further, the reduced form [Fe(NMes)L-2](-) reacts nucleophilically with CS2 by inserting into the imido iron bond, as well as electrophilically with CO under nitrene transfer. The neutral [Fe(NMes)L-2] complex shows enhanced electrophilic behavior as evidenced by nitrene transfer to a phosphine, yet in combination with an overall reduced reactivity.

Automated summary

Imidyl and nitrene metal species are important in chemical reactions such as N-functionalisation and aziridination. This article reports on the synthesis and properties of trigonal imido iron complexes, which exhibit different characteristics in their reduced and oxidized forms. Reactivity studies show the ability of these complexes to interact with C-H bonds and other molecules.