Uranium versus Thorium: A Case Study on a Base-Free Terminal Uranium Imido Metallocene

Area of Science:

• Organometallic Chemistry
• Actinide Chemistry
• Inorganic Chemistry

Background:

• Base-free terminal actinide imido metallocenes are crucial for understanding actinide bonding and reactivity.
• Comparing uranium and thorium complexes provides insights into f-orbital participation in chemical bonding.

Purpose of the Study:

• To compare the structure, bonding, and reactivity of uranium and thorium imido metallocenes.
• To elucidate the influence of steric and electronic factors on the behavior of these actinide complexes.

Main Methods:

• Synthesis and characterization of uranium and thorium imido metallocenes.
• Density Functional Theory (DFT) calculations to analyze electronic structure and bonding.
• Reactivity studies involving various organic and inorganic reagents.

Main Results:

• Uranium imido metallocene (1) is sterically more crowded and exhibits greater 5f orbital contribution to bonding compared to the thorium analog (1').
• Complex 1 displays diverse reactivity, including Lewis base adduct formation, cycloadditions with unsaturated compounds (e.g., CS2, ketones), and single/two-electron transfer processes.
• Reactions of complex 1 with aldehydes and carbodiimides lead to unique multinuclear complexes or metallaheterocycles, while it remains unreactive towards DCC.

Conclusions:

• Steric and electronic properties significantly dictate the reactivity patterns of actinide imido metallocenes.
• The enhanced covalent character of the U-N bond in complex 1 contributes to its unique reaction pathways.
• These findings advance the understanding of f-element organometallic chemistry and potential applications.