Bis(piperazinium) Pentakis(trioxomolybdo)bis(ethylphosphonate) Dihydrate

The title compound, bis(piperazine-1,4-diylium) bis(ethylphosphonato)-1[kappa]O,2:3[kappa]²O',4:5[kappa]²O'';1:2[kappa]²O,3:4[kappa]²O',5[kappa]O''- penta-[mu]-oxo-1:2[kappa]²O;1:5[kappa]²O;2:3[kappa]²O;3:4[kappa]²O;4:5[kappa]²O-decaoxo-1[kappa]²O,2[kappa]²O,3[kappa]²O,4[kappa]²O,5[kappa]²O-pentamolybdenum(4-) dihydrate, (C₄H₁₂N₂)₂[Mo₅O₁₅(C₂H₅O₃P)₂].2H₂O, crystallizes as isolated five-unit rings of vertex- and edge-sharing distorted octahedral MoO₆ groups, doubly capped by PC₂H₅ entities {as [(C₂H₅)PO₃]^2- ethylphosphonate groups}, resulting in [(MoO₃)₅{(C₂H₅)PO₃}₂]^4- {or [Mo₅P₂O₂₁(C₂H₅)₂]^4-} anions. Doubly protonated piperazinium cations and water molecules complete the structure. This phase shows reversible dehydration/rehydration without loss of structure.

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