Sulfur-Ligated [2Fe-2C] Clusters as Synthetic Model Systems for Nitrogenase

Area of Science:

• Coordination chemistry
• Organometallic chemistry
• Bioinorganic chemistry

Background:

• Metal clusters with carbon and sulfur donors can mimic nitrogenase active sites.
• Nitrogenase enzymes are crucial for biological nitrogen fixation.

Purpose of the Study:

• To synthesize and characterize novel di-iron clusters supported by yldiide ligands.
• To investigate the electronic properties and reactivity of these clusters in different oxidation states.

Main Methods:

• Synthesis of di-iron clusters with {[Ph2P(S)]2C}2- ligands.
• Isolation of all-ferrous (Fe2II) and mixed-valence (FeIIFeIII) cluster forms.
• Characterization using Mössbauer spectroscopy, X-ray absorption, and resonant X-ray emission spectroscopy.
• Reactivity studies with Lewis bases (4-dimethylaminopyridine) and isocyanides (tBuNC).

Main Results:

• The [L2Fe2] cluster is isolable in Fe2II and FeIIFeIII oxidation states.
• Mössbauer spectra of the mixed-valence cluster indicate slow electron transfer.
• The Fe2II cluster shows selective coordination with one Fe site upon addition of 4-dimethylaminopyridine.
• Reaction with tBuNC leads to a monometallic complex with a new C-C bond.

Conclusions:

• The synthesized di-iron clusters serve as models for nitrogenase active sites.
• The electronic structure and reactivity are tunable based on oxidation state and ligand interactions.
• These findings advance the understanding of metal-sulfur cluster chemistry and potential applications.