We report the syntheses and characterizations of the first polyoxothiometalate complexes isolated from the reaction of the oxothiocationic [MoV2O2S2]2+ precursor and bisphosphonate ligands H2O3PCR(OH)PO3H2 (R = C4H5N2, zoledronic acid; R = C3H6NH2, alendronic acid). [(Mo2O2S2(H2O))4(O3PC(O)(C4H6N2)PO3)4]8− (Mo8S8(Zol)4) and [(Mo2O2S2(H2O))4(O3PC(O)(C3H6NH3)PO3)4]8− (Mo8S8(Ale)4) contain four MoV dimers connected via bisphosphonate ligands. These compounds offer a unique opportunity to compare the structures and properties of cyclic compounds obtained with [Mo2O2S2]2+ and with [Mo2O4]2+. The oxothio compounds appear less stable in solution than the oxo analogue, confirming the higher lability and versatility of [Mo2O2S2]-based compounds compared to [Mo2O4]-based POMs. Multinuclear and multidimensional solid-state NMR studies were carried out to complement X-ray diffraction analysis. Information on short-range interactions, dynamic behaviors, and local disorder within the crystalline materials are therefore reported. Furthermore, the electrocatalytic properties of Mo8S8(Ale)4 and of the analogous [(Mo2O4(H2O))4(O3PC(O)(C3H6NH3)PO3)4]8− (Mo8O8(Ale)4) immobilized onto the surface of a glassy carbon electrode were studied, thus evidencing the ability of [Mo2O2S2]-based cycles to promote the reduction of protons into hydrogen, whereas the oxo analogue appeared inactive.
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