Complexes featuring a linear [N≡U≡N] core isoelectronic to the uranyl cation.

Area of Science:

• Inorganic Chemistry
• Uranium Chemistry
• Coordination Chemistry

Background:

• The uranyl cation [UO2]2+ dominates uranium's aqueous chemistry.
• The isoelectronic analogue, molecular [UN2], has been limited to matrix isolation studies.
• Synthesis of stable [UN2] complexes is crucial for understanding uranium-nitrogen bonding.

Purpose of the Study:

• To synthesize and characterize novel molecular uranium nitride complexes.
• To investigate the coordination chemistry and bonding of the [UN2] moiety.
• To compare the structural and electronic properties with the uranyl cation.

Main Methods:

• Reaction of uranium pentahalides (UCl5 or UBr5) with anhydrous liquid ammonia.
• Characterization using single-crystal X-ray diffraction.
• Spectroscopic analysis (Raman, infrared) and 14N/15N isotope studies.
• Quantum chemical calculations.

Main Results:

• Three distinct [UN2] complexes were successfully synthesized.
• The [UN2] moieties are linear, exhibiting pentagonal bipyramidal coordination spheres.
• Formation of almost linear, trinuclear complex cations with U≡N triple bonds was observed.
• Lewis acidic ligands coordinate to nitrido ligands, forming supramolecular structures.

Conclusions:

• Stable molecular uranium nitride complexes ([UN2]) have been synthesized in solution.
• The [UN2] moiety displays bonding characteristics analogous to the uranyl cation.
• The findings provide new insights into uranium-nitrogen bonding and coordination chemistry.