Crystal structure of bis­(tri­ethano­lamine-κ(3) N,O,O′)nickel(II) bis­(3-hy­droxy­benzoate) tetra­hydrate

The reaction of 3-hy­droxy­benzoic (m-hy­droxy­benzoic) acid (MHBA), tri­ethano­lamine (TEA) and Ni(NO(3))(2) in aqueous solution led to formation of the hydrated title salt, [Ni(C(6)H(15)NO(3))(2)](C(7)H(5)O(3))·4H(2)O. In the complex cation, the Ni(2+) ion is located on an inversion centre. Two symmetry-related TEA ligands occupy all coordination sites in an N,O,O′-tridentate coordination, leading to a slightly distorted NiN(2)O(4) octa­hedron. Two ethanol groups of each TEA ligand form two five-membered chelate rings around Ni(2+), while the third ethanol group does not coordinate to the metal atom. Two MHBA(−) anions in the benzoate form are situated in the outer coordination sphere for charge compensation. An intricate network of hydrogen bonds between the free and coordinating hy­droxy groups of the TEA ligands, the O atoms of the MHBA(−) anions and the water mol­ecules leads to the formation of a two-dimensional structure extending parallel to (010).