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 ThSxSe2–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.