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Updated: Sep 1, 2025

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
Characterization of a Proposed Terminal Iron(III) Nitride Intermediate of Nitrogen Fixation Stabilized by a
Dirk J Schild1, Lucie Nurdin1, Marc-Etienne Moret2
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Abstract:
Terminal iron nitrides (Fe≡N) have been proposed as intermediates of Fe-mediated nitrogen fixation, and well-defined synthetic iron nitrides have been characterized in high oxidation states, including FeIV , FeV , and FeVI . This study reports the generation and low temperature characterization of a terminally bound iron(III) nitride, P3 B Fe(N) (P3 B =tris(o-diisopropylphosphinophenyl)borane), which is a proposed intermediate of iron-mediated nitrogen fixation by the P3 B Fe-catalyst system. CW- and pulse EPR spectroscopy (HYSCORE and ENDOR), supported by DFT calculations, help to define a 2 A ground state electronic structure of this C3 -symmetric nitride species, placing the unpaired spin in a sigma orbital along the B-Fe-N vector; this electronic structure is distinct for an iron nitride. The unusual d5 -configuration is stabilized by significant delocalization (≈50 %) of the unpaired electron onto the axial boron and nitrogen ligands, with a majority of the spin residing on boron.
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