Syntheses and31P NMR Studies of Cyclic Oxothiomolybdate(V) Molecular Rings: Exchange Properties and Crystal Structures of the Monophosphate Decamer [(H2PO4)Mo10S10O10(OH)11(H2O)2]2− and the Diphosphate Dodecamer [(HPO4)2Mo12S12O12(OH)12(H2O)2]4−

Two oxothiophosphato anions are obtained from solutions containing the [Mo2S2O2]2+ precursor and phosphate ions. The monophosphato anion reveals a Mo10 decameric structure and the diphosphato anion, a Mo12 dodecameric one. Both compounds exhibit an open cavity containing the phosphate ions. A 31P NMR study in solution (see picture) shows that the two compounds are involved in the same equilibrium and that the inner phosphate groups are labile enough to be exchanged.