Nitrogen Fixation Revisited on Iron(0) Dinitrogen Phosphine Complexes

Abstract

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 (15)N NMR spectroscopy as other species formed in the reaction mixture.

Leveraging molecular metal–support interactions for H2 and N2 activation

“…Table 1 displays the degree of N 2 activation for various bimetallics. The range of N 2 activation in our bimetallic complexes (1925 to 2144 cm -1 ) is consistent with marginal activation and an intact N 2 triple-bonded unit, and falls within the range reported for monometallic Fe-N 2 and Co-N 2 complexes [40,58,59].…”

N2‐to‐NH3 Conversion by a triphos–Iron Catalyst and Enhanced Turnover under Photolysis

“…[22] These facts have motivated our group and others to develop single (or multiple) site Fe complexes that can bind and activate dinitrogen. [15,17,18,[23][24][25][26][27] To this end, we have reported the catalytic reduction of nitrogen to ammonia using Fe complexes supported by atetradentate P 3 E ligand scaffold (E = B, C, or Si). [17,20,[28][29][30][31][32] Using the P 3 B Fe catalyst, significant turnover to generate NH 3 has been demonstrated.…”

Testing the Push–Pull Hypothesis: Lewis Acid Augmented N2 Activation at Iron

“…9 While Lewis acids (LAs) such as SiMe 3 + and H + have been reported to react with structural analogues of 1 to provide ill-defined mixtures, 10 their excessive electrophilicity make them inadequate models for noncovalent interactions in the secondary-sphere of nitrogenase. In contrast, neutral boranes are a highly tunable class of LAs 11 that are ideal for modeling these interactions.…”