Crystal structure and electron density of diammonium hexaaquacopper(II) sulfate

An accurate set of X-ray data collected at 298 K was used to refine the structure and study the deformation density of the title compound [NH412[Cu(H20)6](SO4)2, M r=399.93, monoclinic, P21/a, a= 9.216 (3), b = 12.398 (3), c= 6.301 (2)A, fl= 106.12(2) ° , V=691.59A -3, Z=2, Dx= 1.920 Mg m -3, 2(Mo Ka) = 0-71069 A, p = 1.792 mm -~, F(000) = 414, R = 0.044, wR = 0.019 for 5007 reflections. A neutron structure confirmed the accuracy of bond lengths reported in an earlier determination. The radial structure of the deformation density near the Cu atom also varies, in a manner correlated with metal-oxygen bond length, and consistent with trends in the isomorphous magnesium and nickel structures. Large differences in bond lengths affected by Jahn-Teller distortion are influenced by interactions with neighbouring groups. The strengths of the metal-oxygen bonds are increased by hydrogen bonding of the ligating water molecules, and decreased by interaction between the oxygen lone pairs and the ammonium group.