Systematic studies of early actinide complexes: uranium(IV) fluoroketimides

Area of Science:

• Organometallic Chemistry
• Uranium Chemistry
• Coordination Chemistry

Background:

• Uranium complexes are of interest due to their unique electronic structures and potential applications.
• Ketimide ligands offer tunable steric and electronic properties for metal complexation.
• Fluorine substitution can significantly alter the properties of organic ligands and their metal complexes.

Purpose of the Study:

• To synthesize and characterize novel fluorinated uranium(IV) bis(ketimide) complexes.
• To investigate the structural effects of fluorine substitution on these uranium complexes.
• To explore the electronic, electrochemical, and magnetic properties of the synthesized compounds.

Main Methods:

• Synthesis of uranium(IV) bis(ketimide) complexes via reaction of (C5Me5)2U(CH3)2 with fluorinated nitriles.
• Characterization using single-crystal X-ray diffraction, NMR spectroscopy (1H, 19F), cyclic voltammetry, UV-Vis-NIR absorption spectroscopy, and variable-temperature magnetic susceptibility.
• Computational analysis using Density Functional Theory (DFT) for selected complexes.

Main Results:

• Successfully synthesized a series of fluorinated uranium(IV) bis(ketimide) complexes.
• Observed significant out-of-plane rotation of fluorinated aryl groups in complexes with ortho-fluorine atoms due to steric interactions with the methyl group.
• Correlated structural distortions with changes in electrochemical behavior (irreversible UIV/UIII couple) and magnetic properties (reduced temperature-independent paramagnetism).

Conclusions:

• Fluorine substitution, particularly ortho-fluorine atoms, induces significant structural perturbations in uranium(IV) bis(ketimide) complexes.
• These structural changes influence the electronic transitions and redox potentials of the uranium complexes.
• The observed phenomena provide insights into structure-property relationships in f-element organometallic chemistry.