Diferrous cyanides as models for the Fe-only hydrogenases

Area of Science:

• Organometallic Chemistry
• Bioinorganic Chemistry
• Catalysis

Background:

• Iron-only hydrogenases are crucial enzymes for biological hydrogen metabolism.
• Understanding the structure and reactivity of iron-sulfur clusters is key to mimicking their function.
• Diferrous dicyano dithiolates provide a model system for studying these iron-sulfur environments.

Purpose of the Study:

• To systematically synthesize and characterize novel diferrous cyanide complexes.
• To investigate the structural and electronic relationships between these complexes and the H(ox)(air) state of iron-only hydrogenases.
• To explore the mechanisms of oxidative decarbonylation in these systems.

Main Methods:

• Synthesis of diferrous cyanide derivatives via oxidation reactions.
• Crystallographic analysis for structural determination.
• Density Functional Theory (DFT) calculations for electronic structure and stability.
• Spectroscopic characterization (e.g., IR spectroscopy) for mechanistic insights.

Main Results:

• A series of diferrous cyanide derivatives were synthesized, showing structural and electronic parallels to hydrogenase active sites.
• An unsymmetrical isomer of Fe2(S2C2H4)(mu-CO)(CN)2(PPh3)2(CO)2 was crystallographically characterized, featuring a semibridging carbonyl ligand.
• DFT calculations revealed that the most stable isomers possess cyanide ligands trans to the semibridging carbonyl.
• A new tetracyanide complex, [Fe2(S2C2H4)(mu-CO)(CN)4(CO)2]2-, was synthesized.
• Spectroscopic data provided insights into the oxidative decarbonylation mechanism, leading to the characterization of a tetracarbonyl intermediate and its adduct.

Conclusions:

• The synthesized diferrous cyanide complexes serve as valuable structural and electronic models for the H(ox)(air) state of iron-only hydrogenases.
• The study elucidates the role of semibridging carbonyl ligands and cyanide positioning in the stability and reactivity of these iron-sulfur clusters.
• The findings contribute to understanding the mechanisms of oxidative decarbonylation and the development of bio-inspired catalysts.