Piperazine-1,4-diium bis-(hexa-hydroxido-hepta-oxidohexa-borato-κ(3) O,O',O'')cobaltate(II) hexa-hydrate.

In the title hydrate, (C4H12N2)[Co{B6O7(OH)6}2]·6H2O, both the dication and dianion are generated by crystallographic inversion symmetry. The Co(2+) ion in the dianion adopts a fairly regular CoO6 octa-hedral coordination geometry arising from the two O,O',O''-tridentate ligands. In the crystal, the dianions and water mol-ecules are linked by O-H⋯O hydrogen bonds, generating a framework with large [100] channels, which are occupied by the organic dications. N-H⋯O and C-H⋯O hydrogen bonds consolidate the structure.

Bis[tris-(phenanthroline-κ(2) N,N')cobalt(II)] undeca-tungsto(VI)vanado(V)phosphate dihydrate.

In the title hydrated salt, [Co(C12H8N2)3]2[PVW11O40]·2H2O, the complete Kegggin ion is generated by crystallographic inversion symmetry, which imposes statistical disorder on the O atoms of its central PO4 group. The V atom is statistically disordered over all the metal sites of the anion. In the cation, the Co(2+) ion is coordinated by three bidentate 1,10-phenanthroline (phen) ligands, generating a distorted CoN6 octa-hedron. Possible very weak intra-molecular C-H⋯π inter-actions occur in the cation. In the crystal, the components are linked by O-H⋯O and C-H⋯O inter-actions, building a three-dimensional network featuring one-dimensional voids along the c-axis direction.

Bis(benzyl-ammonium) di-hydrogen diphosphate.

The asymmetric unit of the title salt, 2C6H5CH2NH3 (+)·H2P2O7 (2-), contains two independent benzyl-ammonium cations and a di-hydrogen diphosphate dianion. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the cations and anions, forming a two-dimensional network parallel to (010). Within this network, weak C-H⋯O hydrogen bonds are observed.

Tetra-quinolinium ditelluro(VI)octa-vanadate(V) octa-hydrate.

In the title compound, (C9H8N)4[Te2V8O28]·8H2O, the com-plete heteropolyanion is generated by a crystallographic inversion centre. One of the two quniolinium ions forms an N-H⋯Op (p = polyoxidometallate) hydrogen bond and the other an N-H⋯Ow (w = water) hydrogen bond. The water mol-ecules further link the components by O-H⋯Op and O-H⋯Ow hydrogen bonds. A number of C-H⋯O inter-actions and aromatic π-π stacking inter-actions [shortest centroid-centroid separation = 3.541 (7) Å] are also observed. Together, these generate a three-dimensional network.

Bis(4-amino-pyridinium) µ6-oxido-dodeca-µ2-oxido-hexaoxido[rhenium(VII)tetratungsten(VI)vanadium(V)]ate hepta-hydrate.

In the title organic-inorganic hybrid compound, (C5H7N2)2[ReVW4O19]·7H2O, the Lindqvist-type polyoxido anion has crystallographically imposed mm2 symmetry and is built up by six MO6 (M = W, V, Re) edge-sharing distorted octa-hedra. The Re and V atoms share the same crystallographic site in a 0.5:0.5 ratio. The 4-amino-pyridinium cations lie on a mirror plane. Three of the four independent water O atoms in the asymmetric unit are located on a mirror plane whereas the remaining O atom has mm2 site symmetry. In the crystal, the cations, anions and water mol-ecules are linked into a three-dimensional network through O-H⋯O and N-H⋯O hydrogen-bonding inter-actions.