Bis(μ-3-hydroxybenzoato)-κ2O1:O3;κ2O3:O1-bis[bis(1H-benzimidazole-κN3)(3-hydroxybenzoato-κO)nickel(II)] bis(1H-benzimidazole-κN3)bis(3-hydroxybenzoato-κO1)nickel(II) hexahydrate

The title compound, [Ni2(C7H5O3)4(C7H6N2)4][Ni(C7H5O3)2(C7H6N2)2]·6H2O, is a mononuclear/dinuclear nickel(II) cocrystal, the two mol­ecular species inter­acting through hydrogen bonds that involve the uncoordinated water mol­ecules. In the mononuclear species, the NiII ion, located on an inversion center, is coordinated by two 1H-benzimidazole (bzim) ligands and two 3-hydroxy­benzoate (hba) anions in a square-planar geometry. In the centrosymmetric dinuclear species, the NiII ion is coordinated by two bzim ligands and three hba anions in a square-pyramidal geometry; of the two independent hba anions, one bridges two NiII ions with both carboxylate and hydroxyl groups whereas the other coordin­ates in a unidentate manner to the NiII ion. The apical Ni—Ohydrox­yl bond is 0.39 A longer than the basal Ni—Ocarbox­yl bonds. The face-to-face separation of 3.326 (9) A indicates the existence of π–π stacking between parallel bzim ligands of adjacent dinuclear entities. Extensive N—H⋯O and O—H⋯O hydrogen bonds help to stabilize the crystal structure.