Synthesis and structure of -2,5-di-methyl-piperazine-1,4-diium di-hydrogen diphosphate.

In the title salt, CHN ·HPO , the complete dication is generated by a crystallographic centre of symmetry with the methyl groups in equatorial orientations. The complete dianion is generated by a crystallographic twofold axis with the central O atom lying on the axis: the P-O-P bond angle is 135.50 (12)°.

Bis(2-meth-oxy-benzyl-ammonium) di-aqua-bis-(di-hydrogen diphosphato-κ(2) O,O')cobaltate(II) dihydrate.

The title compound, (C8H12NO)2[Co(H2P2O7)2(H2O)2]·2H2O, crystallizes isotypically with its Mn(II) analogue. It consists of alternating layers of organic cations and inorganic complex anions, extending parallel to (100). The complex cobaltate(II) anion exhibits -1 symmetry.

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.

Bis(2-meth-oxy-benzyl-ammonium) di-aqua-bis-(di-hydrogen diphosphato-κ(2) O,O')manganate(II) dihydrate.

The asymmetric unit of the title compound, (C8H12NO)2[Mn(H2P2O7)2(H2O)2]·2H2O, consists of half an Mn(II) complex anion, a 2-meth-oxy-benyl-ammonium cation and a solvent water mol-ecule. The Mn(II) complex anion lies across an inversion center, and has a slightly distorted octa-hedral coordination environment for the Mn(II) ion, formed by two bidentate dihydrogendiphosphate ligands and two water mol-ecules. In the crystal, the components are linked by O-H⋯O and N-H⋯O hydrogen bonds, forming layers parallel to (100).

m-Xylylenediaminium di-aqua-bis-[di-hydrogen diphosphato(2-)]cobaltate(II) dihydrate.

In the title complex, (C8H14N2)[Co(H2P2O7)2(H2O)2]·2H2O, the Co(II) ion lies on an inversion center and is coordinated by two bidentate diphosphate ligands and two water mol-ecules in a slightly distorted octa-hedral coordination geometry. The m-xylylenediaminium cation is located on a twofold rotation axis. In the crystal, a three-dimensional supra-molecular assembly is constructed by O-H⋯O and N-H⋯O hydrogen bonds between the organic cations, complex anions and uncoordin-ated water mol-ecules.

Bis(4-meth-oxy-benzyl-ammonium) dihydrogen diphosphate.

In the title compound, 2C(8)H(12)NO(+)·H(2)P(2)O(7) (2-), the linked PO(4) groups of the diphosphate anion are almost eclipsed and the P-O-P angle is 134.45 (7)°. In the crystal, infinite ribbons of H(2)P(2)O(7) (2-) anions propagate in [100], being linked by strong O-H⋯O hydrogen bonds.

2-Amino-pyrimidinium hydrogen sulfate.

In the crystal structure of the title compound, C(4)H(6)N(3) (+)·HSO(4) (-), hydrogen sulfate anions self-assemble through O-H⋯O hydrogen bonds, forming chains along the b axis, while the cations form centrosymmetric pairs via N-H⋯N hydrogen bonds. The 2-amino-pyrimidinium pairs are linked to the sulfate anions via N-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (10[Formula: see text]). In addition, weak inter-molecular C-H⋯O contacts generate a three-dimensional network.