A capped trigonal prismatic cadmium complex with tetra- and tridentate ligands: bis­(tri­ethanol­amine)-κ³N,O,O′;κ⁴N,O,O′,O′′-cadmium(II) squarate monohydrate

In the crystal structure of the title compound, [Cd(C₆H₁₅NO₃)₂](C₄O₄)·H₂O, a supramolecular structure is observed. The asymmetric unit consists of one unit of the cationic Cd complex, one water mol­ecule and two half-squarate anions, each sitting on a crystallographic inversion center. The different coordinations of the two triethanolamine (TEA) ligands results in an unusual example of coordination number seven for the Cd^II ion. Both TEA ligands coordinate to the Cd^II ion, forming a distorted monocapped trigonal prismatic geometry with approximate C_2v symmetry. One of the TEA ligands acts as an N,O,O′-tridentate ligand, whereas the other behaves as an N,O,O′,O′′-tetradentate donor. The anions and cations are linked to one another by hydrogen bonds between hydroxy H atoms of the TEA ligands and squarate O atoms. The crystal structure is stabilized by O—H⋯O hydrogen bonds between the unligated water mol­ecule and a squarate O atom, together with a weak π–ring interaction between the ethyl­ene group of a TEA ligand and a squarate anion.