Probing f-Block Covalency at the Limits of Hard-Metal/Soft-Ligand Interactions through Chalcogenoether Complexes

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Actinide and Lanthanide Chemistry

Background:

• Understanding f-block metal-ligand interactions is crucial for catalysis and materials science.
• Covalency in these interactions influences electronic structure and reactivity.
• Systematic comparisons between actinides and lanthanides are needed to elucidate trends.

Purpose of the Study:

• To systematically probe covalency in f-block hard-metal/soft-ligand interactions.
• To compare early to middle trivalent actinides (U, Np, Pu, Am) with lanthanide counterparts (La, Ce, Pr, Nd).
• To define actinide selenoether and thioether bonds and assess their covalent character.

Main Methods:

• Synthesis and single-crystal X-ray diffraction of isostructural actinide and lanthanide complexes.
• Employing monoanionic ligands with neutral chalcogen donors (S, Se).
• Computational analyses to support structural findings and electronic structure insights.

Main Results:

• Metrical definition of the first transuranium actinide selenoether bonds (Np, Pu, Am) and first Pr, Nd selenoether complexes.
• Shorter metal-chalcogen bonds observed in actinide complexes compared to lanthanides, suggesting stronger covalent interactions.
• Computational data indicates increased metal-ligand orbital participation in actinides, especially with Se donors.

Conclusions:

• Actinide-chalcogen bonds exhibit stronger covalent character than their lanthanide analogs.
• Covalency diminishes across the f-block series, with the Am-Nd comparison showing less pronounced differences.
• Valence shell orbital participation increases with heavier chalcogens (Se vs. S) in these f-block complexes.