Spectroscopic and Computational Evidence of Uranium Dihydrogen Complexes

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Dihydrogen complexation is well-established in transition metal chemistry.
• Previous studies have not demonstrated dihydrogen complexation in the 5f series (actinides).

Purpose of the Study:

• To spectroscopically detect and characterize dihydrogen complexation in a uranium(III) complex.
• To investigate the electronic structure and bonding in uranium-f-element dihydrogen complexes.
• To compare findings with lanthanide metallocenes for broader implications in f-element chemistry.

Main Methods:

• Synthesis and characterization of a uranium(III) complex, (C5H4SiMe3)3U.
• Spectroscopic detection of dihydrogen complexation using NMR spectroscopy.
• Density Functional Theory (DFT) calculations to elucidate electronic structure and bonding.

Main Results:

• Reversible dihydrogen complexation was observed for the uranium(III) complex, forming (C5H4SiMe3)3U-H2 (complex 1).
• The f3 center's paramagnetism facilitated NMR detection of the dihydrogen complex.
• DFT calculations revealed significant delocalization of 5f electron density onto the dihydrogen ligand, indicating an unusual bonding mode.

Conclusions:

• Dihydrogen complexation is demonstrated for the first time in the 5f series with a uranium(III) complex.
• The bonding involves an unusual delocalization of f-electron density, distinct from typical actinide acid-base complexes.
• This work expands the scope of f-element dihydrogen complexation and provides insights for future research in f-element organometallic chemistry.