Controlled Incorporation of Nitrides into W-Fe-S Clusters

Area of Science:

• Bioinorganic Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• The incorporation of monatomic 2p ligands into iron-sulfur clusters is synthetically challenging.
• Interstitial carbide in the FeMo cofactor of Mo-dependent nitrogenase highlights the importance of such ligands.
• Understanding these clusters is crucial for nitrogenase research.

Purpose of the Study:

• To develop synthetic routes for installing nitride ligands into tungsten-iron-sulfur (W-Fe-S) clusters.
• To characterize the structure and electronic properties of novel nitride-ligated W-Fe-S clusters.
• To compare the behavior of nitride ligands with sulfide ligands in an iron-sulfur cluster environment.

Main Methods:

• Development of two distinct synthetic pathways for nitride ligand installation.
• Synthesis of novel nitride-ligated W-Fe-S clusters: [(Tp*)2 W2 Fe6(μ4-N)2S6L4]2-.
• 57Fe Mössbauer spectroscopy to determine metal oxidation states and electron distribution.

Main Results:

• Successful synthesis of unprecedented nitride-ligated W-Fe-S clusters.
• 57Fe Mössbauer study revealed WIV2 FeII4 FeIII2 oxidation states with localized electron distribution.
• Electron distribution is analogous to the mid-valent iron centers of the FeMo cofactor in its resting state.
• Nitrile ligands exhibit similar behavior to sulfide ligands in these Fe-S clusters.

Conclusions:

• The developed synthetic pathways provide access to novel nitride-ligated iron-sulfur clusters.
• The electronic structure of these clusters resembles that of the nitrogenase FeMo cofactor.
• Nitrile ligands can serve as effective mimics of sulfide ligands in nitrogenase-like environments.
• These findings offer valuable insights into the role of reduced nitrogen in nitrogenase catalysis.