Nitrogen Fixation Revisited on Iron(0) Dinitrogen
Phosphine Complexes
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Abstract
A reinvestigation of the treatment
of [Fe(N<sub>2</sub>)(PP)<sub>2</sub>] (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(N<sub>2</sub>)(dmpe)<sub>2</sub>] with methylating agents such
as methyl triflate or methyl tosylate resulted in methylation of the
metal center to afford [FeMe(N<sub>2</sub>)(dmpe)<sub>2</sub>]<sup>+</sup>. Treatment of [Fe(N<sub>2</sub>)(dmpe)<sub>2</sub>] with trimethylsilyl triflate, however, resulted in reaction at
dinitrogen affording NH<sub>4</sub><sup>+</sup> on subsequent treatment
with acid. The side-on bound hydrazine complex [Fe(N<sub>2</sub>H<sub>4</sub>)(dmpe)<sub>2</sub>]<sup>2+</sup> and bis(ammonia) complex
[Fe(NH<sub>3</sub>)<sub>2</sub>(dmpe)<sub>2</sub>]<sup>2+</sup> were identified by <sup>15</sup>N NMR spectroscopy as other species
formed in the reaction mixture
