Pb₆Co₉(TeO₆)₅, hexa­lead(II) nona­cobalt(II) penta­tellur­ate(VI), is isotypic with its nickel(II) analogue. The asymmetric unit contains two Pb atoms (site symmetries .2., ..2), four Co atoms (..2, ..2, 3.., 3.2) two Te atoms (..2, 3..) and six O atoms (all in general positions), with the Te and Co sites in octa­hedral coordination environments. The crystal structure can be subdivided into two types of layers parallel to (001). The first layer at z ≃ 0.25 is made up of edge-sharing [CoO₆] and [TeO₆] octa­hedra, with 1/6 of the octa­hedral holes not occupied. The second layer, situated at z ≃ 0, consist of an alternating arrangement of Pb^II atoms and of double octa­hedra that are made up from face-sharing [CoO₆] and [TeO₆] octa­hedra. The two types of layers are linked together through corner-sharing of [CoO₆] and [TeO₆] octa­hedra. The Pb^II atoms are situated in the cavities of the framework and are stereochemically active with one-sided [4]- and [6]-coordinations, respectively.

The melaminium (2,4,6-triamino-1,3,5-triazin-1-ium) cation in the title compound, C₃H₇N₆⁺·C₃H₃O₄⁻, is essentially planar, with a r.m.s. deviation of the non-H atoms of 0.0085 Å. Extensive hydrogen bonding of the types N—HN and N—HO between cations and cations and between cations and hydrogen malonate (2-carb­oxy­ethano­ate) anions leads to the formation of supra­molecular layers parallel to (1-2-1). An intra­molecular O—HO hydrogen bond in the single deprotonated malonate anion also occurs.

The asymmetric unit of the solvated title salt, 2C₃H₇N₆⁺·C₄H₄O₄²⁻·C₄H₆O₄·2H₂O, contains one essentially planar melaminium (2,4,6-triamino-1,3,5-triazin-1-ium) cation (r.m.s. deviation of the non-H atoms = 0.0097 Å), one-half of a succinate anion, one-half of a succinic acid solvent mol­ecule and one water molecule of crystallization; full mol­ecules are generated by inversion symmetry. Supra­molecular layers parallel to (12-1) are formed through extensive inter­molecular hydrogen bonding of the types O—HO, N—HN and N—HO between the components.