A Uranium(II) Arene Complex That Acts as a Uranium(I) Synthon

Area of Science:

• Organometallic Chemistry
• Uranium Chemistry
• Actinide Chemistry

Background:

• Amidate-supported uranium complexes offer unique electronic properties.
• Understanding the reduction states and reactivity of uranium is crucial for catalysis and materials science.

Purpose of the Study:

• To synthesize and characterize novel anionic uranium complexes.
• To investigate the electronic structure and redox behavior of these complexes.
• To explore the reactivity of reduced uranium species with various substrates.

Main Methods:

• Synthesis of uranium and thorium amidate complexes.
• Two-electron reduction using KC8.
• Spectroscopic characterization (EPR).
• Magnetic susceptibility measurements.
• Computational studies (DFT, CASSCF).
• Reactivity studies with iodine, cycloheptatriene, and cyclooctatetraene.

Main Results:

• Formation of an anionic bis(arene) complex [K[2.2.2]cryptand][U(TDA)2] (3) with a U(II) center and monoreduced arene.
• Complex 3 acts as a U(I) synthon, reducing I2 to U(III)-U(III) species and CHT to a U(IV) complex.
• Reaction with COT yields U(III) and U(COT)2, while complex 2 yields a U(IV)-U(IV) inverse sandwich complex.
• Reduction of Th(TDA)4 (4) yields [K[2.2.2]cryptand][Th(TDA)3(THF)] (5) with a direduced arene.

Conclusions:

• The electronic structure of complex 3 is a U(II) center with a monoreduced arene, behaving as a U(I) synthon.
• The reactivity studies demonstrate the versatile reducing capabilities of the U(I) species.
• The thorium complex 5 features a direduced arene bound to Th(IV), showcasing different redox behavior.