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-2nu 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 pi-ring interaction between the ethylene group of a TEA ligand and a squarate anion.