RESUMEN
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.
RESUMEN
Tetrametallic thorium compounds with a Th4E4 core (E = S, Se) having a distorted cubane structure can be prepared by ligand-based reductions of elemental E with thorium chalcogenolates, prepared by in situ oxidation of Th metal with a 3:1 mixture of PhEEPh and F5C6EEC6F5. Four compounds, (py)8Th4S4(µ2-SPh)4(SC6F5)4, (py)8Th4S4(µ2-SPh)4(SeC6F5)4, (py)8Th4Se4(µ2-SePh)4(SeC6F5)4, and (py)8Th4Se4(µ2-SePh)4(SC6F5)4, were isolated and characterized by NMR spectroscopy and X-ray diffraction. These compounds clearly demonstrate the chemical impact of ring fluorination, with the less-nucleophilic EC6F5 ligands occupying the terminal binding sites and the EPh ligands bridging two metal centers. For this series of compounds, crystal packing and intermolecular π···π and H-bonding interactions result in a consistent motif and crystallization in a body-centered tetragonal unit cell. Solution-state 77Se NMR spectroscopy reveals that the solid-state structures are maintained in pyridine.