Structures of the potassium nitroprusside 2.5 and 0.8 hydrates

Potassium pentacyanonitrosylferrate hydrate (1/2.5), K2[Fe(CN)5NO]x2.5H2O, Mr=339.18, monoclinic, P21/n (No. 14), a=10.054(4), b=24.510(5), c=11.018(6) A, β=109.60(4)0, V=2558(3) A3, Z=8, Dm=1.75, Dx=1.762 g cm-3, Mo Kα radiation, λ=0.71073 A, μ(Mo Kα)=18 cm-1, F(000)=1352. Potassium pentacyanonitrosylferrate hydrate (1/0.8), K2[Fe(CN)5NO]x0.8H2O, Mr=311.98, orthorhombic, Pna21 (No. 33), a=30.000(8), b=11.272(3), c=16.053(4) A, V=5428(2) A3, Z=20, Dx=1.909 g cm-3, Mo Kα radiation, λ=0.71073 A, μ(Mo Kα)=21 cm-1, F(000)=3108. Both structures were solved by the heavy-atom technique and refined anisotropically to R factors 0.040 and 0.059, from 2805 and 3436 I≥3σ(I) independent reflections, respectively. In both structures the water molecules are not involved in strong hydrogen bonds. The low specificity of these interactions is probably responsible for the occurrence of the three different hydrates reported. (orig.)