A deformation electron density study of potassium oxalate monohydrate at 100 K

The deformation electron density in K2C2O4.H2O at 100 K has been studied using Hirshfeld-type deformation density functions [Hirshfeld (1971). Acta Cryst. B27, 769-781]. K2C2O4.H2O, Mr=184.24, monoclinic, C2/c, a=9.0687(5), b=6.2128(3), c=10.5941(5)A, β=110.820(1)0, V=557.92A3, Z=4, Dx=2.193 Mg m-3, λ(Mo Kα)=0.71069A, μ=1.610 mm-1, F(000)=368, T=100K. wR(F2) values for 3543 Fa2>0 reflections: 0.0568 (deformation refinement); 0.0623 (conventional refinement). The static deformation density for the H2O molecule shows an O-H bond maximum of 0.25 eA-3 and an oxygen lone-pair maximum of 0.35 e A-3. The static peak maxima at the midpoints of the C-C and C=O bonds are 0.25-0.30 eA-3. Δρ maps exhibit clear π-bonding character in these bonds. The results from this work are compared with those from earlier room temperature, X-ray and neutron diffraction refinements. (orig./BHO)