Nitrogen Fixation Revisited on Iron(0) Dinitrogen Phosphine Complexes

A reinvestigation of the treatment of [Fe­(N₂)­(PP)₂] (PP = depe, dmpe) with acid revealed no ammonium formation. Instead, rapid protonation at the metal center to give hydride complexes was observed. Treatment of [Fe­(N₂)­(dmpe)₂] with methylating agents such as methyl triflate or methyl tosylate resulted in methylation of the metal center to afford [FeMe­(N₂)­(dmpe)₂]⁺. Treatment of [Fe­(N₂)­(dmpe)₂] with trimethylsilyl triflate, however, resulted in reaction at dinitrogen affording NH₄⁺ on subsequent treatment with acid. The side-on bound hydrazine complex [Fe­(N₂H₄)­(dmpe)₂]²⁺ and bis­(ammonia) complex [Fe­(NH₃)₂­(dmpe)₂]²⁺ were identified by ¹⁵N NMR spectroscopy as other species formed in the reaction mixture