Structures of diethylenetriaminecopper(II) cations. Part III. Crystal structure of oxalatodiethylenetriamine copper(II) tetrahydrate

Abstract

The crystal structure of oxalatodiethylenetriaminecopper(II) tetrahydrate has been determined by X-ray diffraction methods; refinement has been carried out by a full-matrix least-squares procedure with three-dimensional counter data. There are four molecules in the monoclinic unit cell, space group P2₁/c, with a= 12·287, b= 6·559, c= 17·541 Å, β= 108·38°. The diethylenetriamine ligand is tridentate, co-ordinating with the terminal nitrogen atoms trans to each other. The oxalate ion co-ordinates to the copper atom in a 1,2-cis-conformation. One oxygen atom co-ordinates at 1·965 Å in the plane of the three equal copper–nitrogen bonds (2·009 Å) and the second oxygen atom at 2·230 Å completes a distorted square-based pyramidal arrangement about the copper atom. The sixth position of a distorted octahedral copper environment is occupied by an oxygen atom of the oxalate ion of another molecule at 2·994 Å. The water molecules are present as lattice molecules and an extensive hydrogen bond system exists in the crystal.