Tetra­kis(2,4,6-triamino-1,3,5-triazin-1-ium) tris­(pyridine-2,6-dicarboxyl­ato)calcate(II) hexa­hydrate

The title compound, (C(3)H(7)N(6))(4)[Ca(C(7)H(3)NO(4))(3)]·6H(2)O or (tataH)(4)[Ca(pydc)(3)]·6H(2)O (where tata is 2,4,6-triamino-1,3,5-triazine and pydcH(2) is pyridine-2,6-dicarboxylic acid), was obtained by reaction of Ca(NO(3))(2)·4H(2)O with the proton-transfer compound (tataH)(2)(pydc) in aqueous solution. The [Ca(pydc)(3)](4−) anion has twofold crystallographic symmetry. It is a nine-coordinate Ca(II) complex with a distorted tricapped trigonal-prismatic coordination geometry. The structure also contains four tataH(+) cations and six uncoordinated water mol­ecules. There are extensive O—H⋯O, O—H⋯N, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds in the crystal structure.