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

Thorium cubanes (py)₈Th₄(μ₃-E')₄(μ₂-EPh)₄(η-EPh)₄ (E, E' = S, Se) were prepared from ligand-based redox reactions of elemental E' with Th(EPh)₄. Products with all four possible E/E' combinations (E,E' = S,S; Se,Se; S,Se; Se,S) were isolated and structurally characterized, ligand exchange reactions were explored, and the heterochalcogen compounds (py)₈Th₄(μ₃-S)₄(μ₂-SePh)₄(η-SePh)₄ and (py)₈Th₄(μ₃-Se)₄(μ₂-SPh)₄(η-SPh)₄ were heated to deliver solid solutions of ThS _xSe_{2- x}. NMR spectroscopy indicated that the structure of (py)₈Th₄(μ₃-Se)₄(μ₂-SePh)₄(η-SePh)₄ is static in pyridine solution, with no exchange between bridging and terminal PhE^- ligands on the NMR time scale. A computational analysis of ⁷⁷Se NMR shifts provides insight into the solution structure of both clusters and monomeric chalcogenolates.