Cadaverinium dichloride: a case of centro-non-centrosymmetric ambiguity.

In the title salt, also known as pentane-1,5-diammonium dichloride, C(5)H(16)N(2)(2+)x2Cl(-), the cation exists in an ideal fully extended conformation and lies on a mirror plane in the space group Pbam. In the crystal structure, layers of cations are hydrogen bonded with Cl(-) anions, which occupy the space between the layers. This kind of packing leads to a short unit-cell parameter of 4.463 (1) Angstrom. This structure is another case of centro-non-centrosymmetric ambiguity; the best results were obtained in a centrosymmetric space group, with the disordered NH(3) groups accounting for the non-centrosymmetric 'component'.