Uranium(III) and Uranium(IV) meta-Terphenylthiolate Complexes

Area of Science:

• Organometallic Chemistry
• Uranium Chemistry
• Coordination Chemistry

Background:

• Uranium complexes are of interest for their unique electronic properties and potential applications.
• The development of novel ligand systems is crucial for controlling the reactivity and structure of uranium compounds.
• Bulky ligands can stabilize unusual oxidation states and coordination geometries.

Purpose of the Study:

• To synthesize and characterize new crystalline uranium complexes supported by the bulky m-terphenylthiolate ligand system, SAr.
• To investigate the reactivity of uranium precursors with the SAr ligand under various conditions.
• To explore the structural diversity and bonding characteristics of these novel uranium complexes.

Main Methods:

• Synthesis of uranium complexes using various uranium precursors (UCl4, U(BH4)4, U(BH3)3(toluene)) and the SAr ligand (KSAr, HSAr).
• Characterization techniques including single-crystal and powder X-ray diffraction, multinuclear NMR, IR, UV-Vis-NIR spectroscopy, SQUID magnetometry, and elemental analysis.
• Quantum chemical calculations to elucidate U-S bonding interactions.

Main Results:

• Successful synthesis of five crystalline uranium complexes (1-5) with varying uranium oxidation states (U(IV) and U(III)) and ligand coordination.
• Isolation of [UIV(SAr)2(Cl)2] (1), [UIV(μ-SAr)(BH4)2(μ-BH4)(μ3-BH4)K]2 (2), [UIII(H3B·SAr κS,H,H)(BH4)2] (3), a mixture of [UIII(SAr)(BH4)2] (4a) and [{UIII(SAr)(BH4)}2{μ-B2H6}] (4b), and [UIII(SAr)2(BH4)] (5).
• Identification of complex 4b as a rare example of a nido-metalloborane.
• Detailed characterization of the structural, spectroscopic, magnetic, and electronic properties of the synthesized complexes.
• Computational analysis provided insights into the nature of uranium-sulfur bonds.

Conclusions:

• The bulky SAr ligand effectively supports the synthesis of diverse uranium complexes across different oxidation states.
• The study demonstrates the versatility of uranium precursors in reactions with terphenylthiolate ligands.
• The characterization of these complexes, including the nido-metalloborane, expands the understanding of uranium coordination chemistry and bonding.
• Quantum chemical calculations are valuable tools for interpreting bonding in complex uranium systems.