Diiron Dithiolate Hydrides Complemented with Proton-Responsive Phosphine-Amine Ligands

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Bioinorganic Chemistry

Background:

• Iron-sulfur clusters are crucial in biological systems, particularly in hydrogenase enzymes.
• Understanding the reactivity and structure of synthetic iron complexes can provide insights into biological mechanisms.
• The development of new ligands for metal complexes is essential for catalysis and materials science.

Purpose of the Study:

• To synthesize and characterize novel iron complexes with amino-phosphine ligands.
• To investigate the structural and electronic properties of these complexes and their protonated/deprotonated forms.
• To explore the relevance of these synthetic complexes to the active sites of [NiFe]-hydrogenases.

Main Methods:

• Reaction of Fe₂(pdt)(CO)₆ with Ph₂PC₆H₄NH₂ (PNH₂) to form amido hydride complex.
• Isolation and characterization of intermediates using X-ray crystallography and NMR spectroscopy.
• FTIR spectroscopy to study vibrational changes upon protonation and deprotonation.

Main Results:

• Synthesis of HFe₂(pdt)(CO)₂(PNH₂)(PNH) ([H1H]⁰) and its protonated ([H₂1H]⁺) and deprotonated ([1H]^-) derivatives.
• X-ray crystallography revealed specific ligand coordination and hydrogen bonding in the protonated form.
• NMR and FTIR studies indicated rapid proton exchange and significant vibrational shifts (υ_CO) across the series.

Conclusions:

• The chelating amino/amido-phosphine ligands exhibit dynamic behavior, including proton exchange.
• The synthesized iron complexes display structural and spectroscopic features analogous to [NiFe]-hydrogenase active sites.
• This work contributes to the understanding of iron-sulfur cluster chemistry and biomimetic catalysis.