Iron(I) Complex Bearing an Open-Shell Diazenido Ligand

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Catalysis

Background:

• Low-valent transition-metal diazenido species are crucial intermediates in dinitrogen reduction.
• Previously, only closed-shell diazenido ligands were isolable; open-shell variants remained elusive.
• Understanding open-shell diazenido ligands is key to advancing nitrogen fixation research.

Purpose of the Study:

• To synthesize and characterize a novel open-shell silyldiazenido ligand complex.
• To investigate the electronic structure and spin state of the synthesized complex.
• To explore the reactivity of the novel iron complex in various chemical transformations.

Main Methods:

• Synthesis of the iron(I) complex via silylation of an iron(-I)-N2 precursor.
• Full characterization using spectroscopic methods (e.g., NMR, EPR, X-ray crystallography).
• Theoretical calculations (DFT) to determine electronic structure and spin state.
• Reactivity studies including disproportionation, alkene exchange, photolysis, and reactions with radicals and bromides.

Main Results:

• Successful synthesis and characterization of a unique iron(I) complex with an open-shell silyldiazenido ligand.
• Established an S=1/2 ground spin state, described as a quartet iron(I) center with an antiferromagnetically coupled triplet silyldiazenido ligand.
• Demonstrated facile ligand lability, disproportionation, alkene exchange, and light-induced Si-radical transfer.
• Showcased the complex's reducing nature and weak hydrogen-atom abstraction capabilities.

Conclusions:

• The study reports the first isolable iron complex featuring an open-shell silyldiazenido ligand.
• The complex exhibits rich and diverse reactivity, highlighting the potential of open-shell diazenido species in catalysis.
• Findings provide new insights into the fundamental chemistry of low-valent transition-metal diazenido complexes and dinitrogen reduction pathways.