Crystal structure and Hirshfeld surface analysis of poly[[bis­[μ(4)-N,N′-(1,3,5-oxadiazinane-3,5-di­yl)bis(carbamoyl­methano­ato)]nickel(II)tetra­potassium] 4.8-hydrate]

The title compound, {[K(4)Ni(2)(C(7)H(6)N(4)O(7))(2)]·4.8H(2)O}(n), was obtained as a result of a template reaction between oxalohydrazide­hydroxamic acid, formaldehyde and nickel(II) nitrate followed by partial hydrolysis of the formed inter­mediate. The two independent [Ni(C(7)H(6)N(4)O(7))](2–) complex anions exhibit pseudo-C (S) symmetry and consist of an almost planar metal-containing fragment and a 1,3,5-oxadiazinane ring with a chair conformation disposed nearly perpendicularly with respect to the former. The central Ni(II) atom has a square-planar N(2)O(2) coordination arrangement formed by two amide N and two carboxyl­ate O atoms. In the crystal, the nickel(II) complex anions form layers parallel to the ab plane. Neighboring complex anion layers are connected by layers of potassium cations for which two of the four independent cations are disordered over two sites [ratios of 0.54 (3):0.46 (3) and 0.9643 (15):0.0357 (15)]. The framework is stabilized by an extensive system of hydrogen bonds where the water mol­ecules act as donors and the carb­oxy­lic O atoms, the amide O atoms and the oxadiazinane N atoms act as acceptors.