ISSN:
1600-5740
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Diammonium hexaaquacopper(II) disulfate-d20, [ND4]2[Cu(D2O)6](SO4)2, Mr = 419.7, monoclinic, P21/a, a = 9.399 (2), b = 12.673 (2), c = 6.071 (1) Å, β= 107.13 (1)°, V= 691.1 (4) Å3, Z = 2, Dx= 2.02 Mg m−3, Mo Kα radiation, λ = 0.71069 Å, μ = 2.008 mm−1, F(000) = 415.3, T= 85 (2) K, R(I) = 0.020,R(F) = 0.014 for 7287 reflections. The CuO6 octahedron has a large Jahn–Teller distortion; Cu—O(8) 2.301 (1), Cu—O(7) 2.010 (1), Cu—O(9) 1.960 (1) Å. It was necessary to use quartic anharmonic thermal parameters at the CuII site. These modelled potential softening associated with the Jahn–Teller distortions, important even at this temperature. At the ammonium, the sulfate and the hexaaqua-ion sites the charge densities, at this experimental accuracy, can be described by simple valence functions which reflect only local symmetry. Large lower-symmetry densities are not observed; any small such effects are comparable with uncertainties in the treatment of the thermal motion. The valence refinement gave Cu 3d populations of 3d^{1.58 (6)}_{xy}3d^{2.12 (3)}_{xz, yz}3d^{2.18(6)}_{z^{2}}3d^{0.82 (7)}_{x^{2} - y^{2}}. This shows the hole expected in 3d_{x^{2}_y^{2}}, modified, taking overlap into account, by a covalent or acceptance of 0.52 (1) and π back donation of 0.18 (10) e. The rhombic distortion causes 3d_{z^2}/3d_{x^{2} - y^{2}} mixing corresponding to a 3d_{z^2} coefficient of −0.21 (7) in a spin-hole wavefunction. Ionic charges from the model are Cu(OD2)^{17+}_{6}, ND^{6+}_{\xB0} and SO^{1.5-}_{4}. These are more ionic than for the isomorphous CrII salt, where σ and π charge flows are both to the metal, not opposed as here. Qualitatively these results agree with the conclusions from ESR, NMR and optical spectra.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S010876819101323X
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