Thorium Cubanes-Synthesis, Solid-State and Solution Structures, Thermolysis, and Chalcogen Exchange Reactions

Area of Science:

• Inorganic Chemistry
• Materials Science
• Organometallic Chemistry

Background:

• Thorium organometallic chemistry is underexplored.
• Chalcogenide clusters offer unique structural and electronic properties.

Purpose of the Study:

• Synthesize and characterize novel thorium cubane clusters with varying sulfur and selenium ligands.
• Investigate ligand exchange reactions and the formation of thorium sulfide selenide solid solutions.
• Determine the solution-state structure and dynamics of these thorium clusters using NMR spectroscopy.

Main Methods:

• Ligand-based redox reactions utilizing elemental sulfur (S) and selenium (Se) with thorium tetrakis(phenylchalcogenolates) (Th(EPh)4).
• Isolation and structural characterization of four distinct thorium cubane compounds: (py)8Th4(μ3-E')4(μ2-EPh)4(η-EPh)4, where E, E' = S, Se.
• Exploration of ligand exchange reactions and thermal treatment to form ThSxSe2-x solid solutions.
• Nuclear Magnetic Resonance (NMR) spectroscopy, including 77Se NMR, and computational analysis to probe solution structures and ligand dynamics.

Main Results:

• Successfully synthesized and structurally characterized all four possible combinations of sulfur and selenium in thorium cubane clusters.
• Demonstrated the formation of ThSxSe2-x solid solutions by heating heterochalcogen thorium cubanes.
• NMR studies revealed a static structure for (py)8Th4(μ3-Se)4(μ2-SePh)4(η-SePh)4 in pyridine solution, indicating no rapid exchange between bridging and terminal phenylselenolate ligands.
• Computational analysis of 77Se NMR shifts provided insights into the solution structures of the clusters and related monomeric chalcogenolates.

Conclusions:

• The synthesis of diverse thorium cubane clusters expands the scope of organothorium chemistry.
• The ability to form tunable ThSxSe2-x solid solutions from these clusters is significant for materials applications.
• NMR spectroscopy and computational methods are effective tools for elucidating the structural and dynamic properties of these complex thorium clusters in solution.