THE CRYSTAL-STRUCTURE ANALYSIS OF IRON NITROPRUSSIDE, FE[FE(CN)5NO].3H2O

The crystal structure of iron(II) pentacyanonitrosylferrate trihydrate has been determined from three dimensional, single-crystal X-ray diffraction data. Fe[Fe(CN)5NO].3H2O crystallizes in the monoclinic space group P2l/n with lattice constants, a = 7.205(1), b = 14.641(2), c = 10.680(1) angstron, beta = 91.14(1)-degrees and Z = 4, D(m) = 1.89(1) g cm-3 and D(x) = 1.92 g cm-3. Final full-matrix least-squares refinement of 1691 unique reflections yielded R = 0.024 and R(w) = 0.028. Both iron atomic centers have distorted octahedral symmetries. The cation iron center is coordinated by five cyanide ligands and one water molecule, while the second iron center is coordinated by five cyanide ligands and one nitrosyl group. Cyanide bridging links the metal centers. Two uncoordinated water molecules, O(2) and O(3), are hydrogen bonded to the coordinated water molecule, O(1), and occupy channels in the crystal lattice. Important mean bond distances for iron nitroprusside are: Fe(cation)-N = 2.159(17), Fe-C = 1.936(4) and C = N = 1.144(6) angstron. Other notable bond lengths include: Fe-O(1) = 2.152(2), Fe-NO = 1.669(2) and N = O = 1.131(3) angstron. The distances between the coordinated water molecule and two uncoordinated water molecules are 2.855(3) and 2.740(3) angstron.