BIS(PIPERAZINIUM) PENTAKIS(TRIOXOMOLYBDO)BIS(ETHYLPHOSPHONATE) DIHYDRATE

The title compound, bis(piperazine-1,4-diylium) bis(ethylphosphonato)- 1 kappa O,2:3 kappa(2)O',4:5 kappa(2)O ''; 1:2 kappa(2)O,3:4 kappa(2)O ',5 kappa O ''-penta-mu-oxo-1:2 kappa(2)O; 1:5 kappa(2)O; 2:3 kappa(2) O; 3:4 kappa(2)O; 4:5 kappa(2)O-decaoxo-1 kappa(2)O,2 kappa(2)O,3 kapp a(2)O,4 kappa(2)O,5 kappa(2)O-penta-molybdenum(4-) dihydrate, (C4H12N2 )(2)[Mo5O15(C2H5O3P)(2)].2H(2)O, crystallizes as isolated five-unit ri ngs of vertex- and edge-sharing distorted-octahedral MoO6 groups, doub ly capped by PC2H5 entities {as [(C2H5)PO3](2-) ethylphosphonate group s}, resulting in [MoO3)(5){(C2H5)PO3}(2)](4-) {or [Mo5P2O21(C2H5)(2)]( 4-)) anions. Doubly protonated piperazinium cations and water molecule s complete the structure. This phase shows reversible dehydration/rehy dration without loss of structure.