Fluoride crystal structures. Part XIX. Dipotassium aquopentafluoroferrate(III)

Abstract

Crystals of dipotassium aquopentafluoroferrate(III) are monoclinic, space-group C2/c, a= 9·71, b= 7·79, c= 7·95 Å, β= 96·5°, Z= 4. The structure was refined by three-dimensional least-squares methods to R 0·074 for 615 reflections. The structure consists of separate K⁺ and [FeF₅(H₂O)]^2– ions. In the anion the co-ordinated oxygen atom is further from the iron atom (Fe–O 2·07 Å) than the fluorine atoms (mean Fe–F 1·92 Å) but the angles at the iron atom are all very close to 90°. The anions are linked into chains by strong hydrogen bonds (O ⋯ F 2·54 Å).