A New Type of Anionic Framework in Microporous Potassium Iron(II) Phosphate K[Fe(PO4)]

A new iron(II) orthophosphate KFe(PO₄)] has been obtained by hydrothermal synthesis and its crystal structure was determined by single‐crystal X‐ray diffraction: space group P2₁/n, Z = 8, a = 9.6199(10), b = 8.6756(8), c = 10.8996(13) Å, β = 115.577(8)° at 193 K, R = 0.023. Fe^II shows coordination numbers (CN) 4 (distorted tetrahedral) and CN 5 (distorted trigonal bipyramidal). The FeO₄] and FeO₅] units form together with the PO₄] tetrahedra a microporous 3D para‐framework with open channels along the a and b directions. The potassium ions positioned in the channels show CN 7 and 8. The structural relations within the morphotropic row of non‐isotypic KM(PO₄)] structures (M = Zn, Ni, Mn, Fe) are discussed on the basis of common basic structural units.