Crystal structure of bis­­(tri­ethano­lamine-κ3N,O,O′)nickel(II) bis­­(3-hy­dr­oxy­benzoate) tetra­hydrate

The reaction of 3-hy­droxy­benzoic (m-hy­droxy­benzoic) acid (MHBA), tri­ethano­lamine (TEA) and Ni(NO3)2 in aqueous solution led to formation of the hydrated title salt, [Ni(C6H15NO3)2](C7H5O3)·4H2O. In the complex cation, the Ni2+ 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 NiN2O4 octa­hedron. Two ethanol groups of each TEA ligand form two five-membered chelate rings around Ni2+, 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).