Bis(dimethyl-malonato-κO,O')bis-[4-(4-pyridylamino-κN)pyridinium]nickel(II) hexa-hydrate.

In the title compound, [Ni(C(5)H(6)O(4))(2)(C(10)H(10)N(3))(2)]·6H(2)O, divalent nickel ions situated on the crystallographic twofold axis are octa-hedrally coordinated by four O atoms from two dimethyl-malonate ligands in a 1,3-chelating mode and two N atoms from two protonated monodentate 4,4'-dipyridylamine mol-ecules. The mol-ecules link into chains via N-H⋯O hydrogen bonding mediated by protonated pyridyl groups. The chains form layer patterns via π-π stacking [centroid-centroid distance = 3.777 (2) Å] . Water mol-ecule hexa-mers are generated from the unligated water mol-ecules (three per asymmetric unit) by inversion centers at Wyckoff position d. These clusters are situated between the pseudolayers, providing hydrogen-bonding pathways that build up the three-dimensional structure.