A Uranium(VI)-Oxo-Imido Dimer Complex Derived from a Sterically Demanding Triamidoamine

Area of Science:

• Organometallic Chemistry
• Uranium Chemistry
• Coordination Chemistry

Background:

• Uranyl(VI) compounds typically feature robust U=O bonds.
• Activation of these bonds is crucial for synthesizing novel uranium complexes.
• Imido ligands offer unique coordination possibilities in uranium chemistry.

Purpose of the Study:

• To synthesize and characterize a novel uranium(VI) oxo-imido complex.
• To investigate the mechanism of N-Si bond cleavage and U=O bond activation.
• To explore the electronic structure and bonding in the resulting uranium complex.

Main Methods:

• Reaction of [UO2(μ-Cl)4{K(18-crown-6)}2] with [{N(CH2CH2NSiPr i3)3}Li3].
• Single crystal X-ray diffraction, multinuclear NMR, IR, Raman, and optical spectroscopies.
• Cyclic voltammetry and Density Functional Theory (DFT) analyses.

Main Results:

• Formation of oxo-imido complex [{UO(μ-NCH2CH2N[CH2CH2NSiPr i3]2)}2] (1) in a 1:2:2 ratio with byproducts.
• Cleavage of N-Si bond and activation of a U=O bond, forming uranium(VI)-imido and siloxide linkages.
• DFT analysis indicates a σ > π orbital energy ordering for U=N and U=O bonds, characteristic of uranyl.

Conclusions:

• A novel uranium(VI) oxo-imido complex was successfully synthesized and characterized.
• The reaction mechanism involves unprecedented U=O bond activation.
• The electronic structure confirms the uranyl-like nature of the U=N and U=O bonds in the complex.