Crystal structure of bis-(tri-ethano-lamine-κ(3) N,O,O')nickel(II) bis-(3-hy-droxy-benzoate) tetra-hydrate.

The reaction of 3-hy-droxy-benzoic (m-hy-droxy-benzoic) acid (MHBA), tri-ethano-lamine (TEA) and Ni(NO3)2 in aqueous solution led to formation of the hydrated title salt, Ni(C6H15NO3)2·4H2O. 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 NiN2O4 octa-hedron. 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 hy-droxy groups of the TEA ligands, the O atoms of the MHBA(-) anions and the water mol-ecules leads to the formation of a two-dimensional structure extending parallel to (010).