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Structural and spectroscopic characterization of an Fe(VI) bis(imido) complex
Jorge L Martinez1, Sean A Lutz1, Hao Yang2
1Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
Science (New York, N.Y.)
|October 16, 2020
Summary
Researchers synthesized a stable hexavalent iron (Fe(VI)) complex, a rare oxidation state. This Fe(VI) compound, featuring a unique seesaw geometry, was characterized using advanced spectroscopic and structural methods.
Area of Science:
- Inorganic Chemistry
- Bioinorganic Chemistry
- Coordination Chemistry
Background:
- High-valent iron species are crucial in biological oxidation reactions.
- Hexavalent iron complexes, excluding ferrate, are exceptionally uncommon in chemistry.
- Understanding these species provides insight into oxidative biological mechanisms.
Purpose of the Study:
- To synthesize and characterize a stable hexavalent iron (Fe(VI)) complex.
- To investigate the structural and electronic properties of Fe(V) and Fe(VI) bis(imido) complexes.
- To elucidate the factors governing the unique geometry observed in these iron complexes.
Main Methods:
- Synthesis of Fe(V) and Fe(VI) bis(imido) complexes via one-electron oxidation.
- Single-crystal X-ray diffraction for structural determination.
- 57Fe Mössbauer, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and electron-nuclear double resonance (ENDOR) for electronic characterization.
- Computational electronic structure calculations.
Main Results:
- A stable Fe(VI) complex (3) was successfully synthesized from an Fe(V) precursor (2).
- Both Fe(V) and Fe(VI) complexes exhibit a rare four-coordinate iron center with a distinctive 'seesaw' geometry.
- Spectroscopic data and calculations confirm a low-spin d3 Fe(V) configuration (S=1/2) in 2 and a diamagnetic d2 Fe(VI) configuration (S=0) in 3.
- The observed seesaw geometry is attributed to the interplay of Fe-imido sigma and pi bonding interactions.
Conclusions:
- Stable Fe(VI) complexes can be prepared through controlled oxidation of lower-valent iron precursors.
- The 'seesaw' geometry is a recurring structural motif in these bis(imido) iron complexes, dictated by electronic factors.
- This work expands the known chemistry of high-valent iron, offering insights into their electronic structure and bonding.
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