Crystal structures of the simple monoclinic and orthorhombic polytypes of tripotassium hexacyanoferrate(III)

Abstract

The room-temperature (295 K) crystal structures of potassium ferricyanide, K3[Fe(CN)6], have been determined for the simplest monoclinic (a reinvestigation) and orthorhombic polytypes by single- crystal X-ray diffraction. The monoclinic form is P21/c, a 7.047(3), b 10.400(3), c 8.384(3) Ǻ, β 107.29(3)°, Z 2. The iron atoms lie on special positions with symmetry 1. In the orthorhombic form, Pnca, a 13.422(6), b 10.396(4), 8.381(4) Ǻ, Z4, the iron atoms now lie on special positions with symmetry 2 (parallel to c). Residuals are 0.036 and 0.048 for 1232 and 855 'observed' reflections respectively.

High‐pressure studies of the micro‐Raman spectra of iron cyanide complexes: Prussian blue (Fe4[Fe(CN)6]3), potassium ferricyanide (K3[Fe(CN)6]), and sodium nitroprusside (Na2[Fe(CN)5(NO)]·2H2O)

“…The peak initially at 383 cm −1 showed a change in slope from 10.4 to 16.2 cm −1 GPa −1 . These changes are consistent with a transition to an orthorhombic structure of higher symmetry 11. The other peaks, including the CN stretching modes, however, were not affected, and the pressure dependences of the wavenumbers were linear throughout the pressure range.…”

“…Potassium ferricyanide exhibits a second‐order phase transition10 at about 130 K from a room‐temperature monoclinic phase, space group P 2 1 / c , Z = 2, to another monoclinic phase P 2 1 / n , Z = 4, involving a doubling of the a ‐axis length 11. A room‐temperature orthorhombic phase has also been reported 12.…”

Design of single cyanide-bridged tetranuclear bimetallic rectangles exhibiting ferromagnetic coupling

“…The iron-copper separations along the edges are 4.8223 (1)/5.211 (2) [Fe(1)Á Á ÁCu (1a); (a) = Àx + 2, Ày + 1, Àz + 1 (1) and Àx + 2, Ày + 1, Àz + 2 (2)] and 4.991 (1) The iron atom in 1 and 2 is bound to six cyanide ligands in a distorted octahedral surrounding. The Fe-C distances vary in the very narrow range of 1.922(4)-1.957 (3) (1) and 1.930(5)-1.947(4) Å (2), which are approximately equal to those observed in the low-spin iron(III) complex K 3 [Fe(CN) 6 ] (1.93-1.95 Å ) [10]. The coordination geometry of the copper atom can be regarded as a somewhat distorted square pyramidal with three nitrogen atoms of the tridentate bpcam (1) and bpca (2) ligands and a cyanide-nitrogen in the basal plane [Cu-N eq bonds varying in the ranges 1.992 (3) Fig.…”

The First Example of a True “Turnbull’s Blue” Family Compound with Trapped Iron Oxidation States

“…Indeed, comparison of the FeϪC bond lengths in UR with those in K 3 [Fe(CN) 6 ] [25] shows no significant differences. In the potassium salt, all the FeϪC distances are approximately equal (1.93Ϫ1.95 Å ), whereas in UR these values vary within slightly larger limits (1.91 and 1.95 Å ).…”

“…[24] In UR, they are also within these limits and the mean [Fe(CN) 6 ] 3Ϫ radius (the distance between Fe and N) in UR is close to that in K 3 [Fe(CN) 6 ]. [25] Previously, a dynamic JahnϪTeller effect in K 3 [Fe(CN) 6 ] was detected by magnetic circular dichroism [26] and Mössbauer spectroscopy, [27] while a static JahnϪTeller distortion was demonstrated for [Fe([9]ane- Table 2) leave room for speculation about the existence of a JahnϪTeller distortion in this compound.…”