Deciphering Iron‐Catalyzed C−H Amination with Organic Azides: N2 Cleavage from a Stable Organoazide Complex

Abstract Catalytic C−N bond formation by direct activation of C−H bonds offers wide synthetic potential. En route to C−H amination, complexes with organic azides are critical precursors towards the reactive nitrene intermediate. Despite their relevance, α ‐N coordinated organoazide complexes are scarce in general, and elusive with iron, although iron complexes are by far the most active catalysts for C−H amination with organoazides. Herein, we report the synthesis of a stable iron α ‐N coordinated organoazide complex from [Fe(N(SiMe 3 ) 2 ) 2 ] and AdN 3 (Ad=1‐adamantyl) and its crystallographic, IR, NMR and zero‐field 57 Fe Mössbauer spectroscopic characterization. These analyses revealed that the organoazide is in fast equilibrium between the free and coordinated state ( K eq =62). Photo‐crystallography experiments showed gradual dissociation of N 2 , which imparted an Fe−N bond shortening and correspond to structural snapshots of the formation of an iron imido/nitrene complex. Reactivity of the organoazide complex in solution showed complete loss of N 2 , and subsequent formation of a C−H aminated product via nitrene insertion into a C−H bond of the N(SiMe 3 ) 2 ligand. Monitoring this reaction by 1 H NMR spectroscopy indicates the transient formation of the imido/nitrene intermediate, which was supported by Mössbauer spectroscopy in frozen solution.