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 xSe2- 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.