Catalytic N-N coupling of aryl azides to yield azoarenes via trigonal bipyramid iron-nitrene intermediates

Article abstract of DOI:10.1021/ja910224c

(Figure Presented) The reactivity of the trigonal bipyramidal iron(I) complex [SiP^iPr₃]Fe(N₂) ([SiP ^iPr₃] = (2-iPr₂PC₆H ₄)₃Si^-) toward organoazides has been examined. 1-Adamantylazide was found to coordinate the Iron center to form stable [SiP^iPr₃]Fe(η¹-N₃Ad). Aryl azides instead afforded unstable [SiP^iPr₃]Fe(N ₃Ar) species that decayed gradually to regenerate [SiP ^iPr₃]Fe(N₂) with release of azoarenes (ArN=NAr). The conversion of aryl azides to azoarenes can thus be achieved catalytically. Competitive trapping experiments strongly suggest the intermediacy of reactive nitrene complexes of the type [SiP^iPr ₃]Fe(NAr) that couple bimolecularly in the N-N bond forming step. Evidence for one such intermediate was provided by electron paramagnetic resonance spectroscopy via photolysis of [SiP^iPr₃] Fe(N₃Ar) in a frozen glass. The electronic structures of these putative nitrene intermediates have been examined by DFT methods. Copyright