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 and bis(ammonia) complex Fe(NH3)2(dmpe)2 were identified by (15)N NMR spectroscopy as other species formed in the reaction mixture.