Low-Coordinate Iron Chalcogenolates and Their Complexes with Diethyl Ether and Ammonia

Area of Science:

• Organometallic Chemistry
• Bioinorganic Chemistry

Background:

• Iron-sulfur complexes are crucial in biological nitrogen fixation.
• Understanding ligand binding in iron complexes informs catalyst design.

Purpose of the Study:

• Synthesize and characterize novel iron complexes with sterically hindered phenol and thiol ligands.
• Investigate the coordination behavior of these complexes with ether and ammonia.
• Relate the findings to the mechanism of nitrogenase enzymes.

Main Methods:

• Reaction of Fe{N(SiMe3)2}2 with phenols and thiols.
• Recrystallization to form ether complexes.
• Spectroscopic analysis (1H NMR) to study equilibria and ligand binding.
• Ammonia coordination studies.

Main Results:

• Dimeric iron phenolates and a monomeric iron dithiolate were synthesized.
• Ether complexes formed with phenolates but not dithiolates.
• Phenolates formed stable ammonia adducts, while dithiolates showed weak ammonia binding and ligand loss.
• NMR studies revealed equilibria between dimeric and monomeric/adduct forms.

Conclusions:

• Steric and electronic properties of phenol and thiol ligands significantly influence iron complex coordination.
• Weak ammonia binding in iron thiolates provides insight into nitrogenase active site function.
• These complexes serve as models for understanding iron-sulfur cluster reactivity.