Hexa­aqua­nickel diorotate(1–) dihydrate at 150 K

In hexa­aqua­nickel bis(2,6‐di­oxo‐1,2,3,6‐tetrahydro­pyrimidine‐4‐carboxyl­ate) dihydrate, [Ni(H₂O)₆](C₅H₃N₂O₄)₂·2H₂O, the nickel cation is coordinated by six aqua ligands and only associated with the two orotate ions through hydrogen bonds. The structure is isotypic with the magnesium and zinc analogues. The metal cation sits on a crystallographic center of inversion that relates the water mol­ecules and the organic anions. The orotate moieties form an unbonded one‐dimensional chain mediated by a hydrogen‐bonded self‐recognition interaction. The hexa­aqua­nickel complex molecules bridge these chains laterally, acting as molecular clamps that bring neighboring layers nearer than expected. As a result of this three‐dimensional arrangement, a short contact of 3.166 (5) Å is observed between two C atoms of two adjacent ribbons.