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

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) ?, ß 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) ?, 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.