Polymorphism of nickel sulfate hexahydrate

NiSO4.6H2O, Mr=262.85; data collections with Mo Kα radiation, λ=0.7093 A, room temperature. Monoclinic polymorph: C2/c, a=9.880(3), b=7.228(2), c=24.130(3) A, β=98.38(2)0, V=1704.7(6) A3, Z=8, Dx=2.05 g cm-3, μ=25.54 cm-1, F(000)=1088, R=0.031 (wR=0.038) for 2176 observed reflections. Tetragonal polymorph: P41212, a=6.780 (1), c=18.285 (2) A, V=840.5 (3) A3, Z=4, Dx=2.07 g cm-3, μ=25.81 cm-1, F(000)=544, R=0.045 (wR=0.050) for 2102 observed reflections. The structure of the tetragonal polymorph originally determined (without H positions) by Beevers and Lipson and refined by O'Connor and Dale and Stadnicka, Glazer and Koralewski, is confirmed by refinement of X-ray diffraction data. The structure of the monoclinic polymorph is confirmed as being isostructural with NiSO4.6D2O, and a number of other hexahydrate sulfates, e.g. MgSO4.6H2O. Both structures contain isolated [Ni(H2O6] octahedra and [SO4] tetrahedra linked by hydrogen bonding. (orig.)