Assessing structure and dynamics of iron complexes supported by tris(amidate)amine ligands

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Computational Chemistry

Background:

• Tris(2-aminoethyl)amine (TREN) derivatives offer tunable steric and electronic properties for stabilizing metal complexes.
• Low-coordinate metal complexes are crucial for understanding fundamental reactivity and catalysis.

Purpose of the Study:

• To investigate the stabilization of low-coordinate trivalent iron complexes using novel tris(amidate)amine ligands.
• To explore the influence of secondary coordination sphere macrocycles on complex stability and dynamics.
• To utilize molecular dynamics simulations for detailed analysis of coordination sphere behavior.

Main Methods:

• Synthesis and characterization of novel tris(amidate)amine ligands.
• Isolation and structural determination of low-coordinate iron complexes.
• Oxidation reactions to form high-valent iron species.
• Molecular dynamics (MD) simulations to probe coordination sphere dynamics.

Main Results:

• A cavitand-inspired ligand enabled the isolation of a four-coordinate iron complex, FeLOCH2O, via oxidation.
• Comparison with a non-macrocyclized ligand revealed the macrocycle's role in maintaining an open coordination site.
• MD simulations provided insights into how the macrocycle affects primary and secondary coordination sphere dynamics.
• Four- and five-coordinate iron complexes were identified as synthons for trigonal bipyramidal ferric fluoride complexes.

Conclusions:

• Tris(amidate)amine ligands, particularly macrocyclic variants, are effective in stabilizing low-coordinate iron complexes.
• The secondary coordination sphere plays a critical role in controlling the coordination number and reactivity of metal centers.
• MD simulations are valuable tools for understanding dynamic processes in coordination complexes.