A cis-divacant octahedral and mononuclear iron(IV) imide

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Inorganic Chemistry

Background:

• Iron imide complexes are crucial intermediates in various catalytic processes.
• Understanding the electronic structure and reactivity of high-valent iron species is key to designing new catalysts.
• The bis(pyrrolyl)pyridine (pyrr2py2-) ligand offers unique electronic and steric properties for stabilizing unusual metal oxidation states.

Purpose of the Study:

• To synthesize and characterize a novel low-spin iron(IV) imide complex.
• To investigate the electronic properties and coordination geometry of the iron center.
• To evaluate the redox behavior of the bis(pyrrolyl)pyridine ligand in the context of high-valent iron.

Main Methods:

• Synthesis of the iron(IV) imide complex via reduction of an azide precursor with an Fe(II) complex.
• Characterization using spectroscopic techniques (e.g., NMR, UV-Vis) and magnetic susceptibility measurements.
• Comparison with an analogous Fe(III) complex to assess ligand redox activity.

Main Results:

• Successful preparation of a rare low-spin Fe(IV) imide complex, [(pyrr2py)Fe=NAd].
• The complex adopts a cis-divacant octahedral geometry.
• The complex exhibits temperature-independent paramagnetism, consistent with a low-spin d4 configuration.
• The bis(pyrrolyl)pyridine ligand was found to be redox-innocent when compared to an Fe(III) complex.

Conclusions:

• The study demonstrates the successful synthesis of a stable low-spin Fe(IV) imide complex.
• The bis(pyrrolyl)pyridine ligand effectively stabilizes the high-valent iron center.
• This work provides insights into the electronic structure and coordination chemistry of iron-imide bonds, relevant for catalysis.