KFe(SO4)2 crystallizes in the monoclinic C2/m space group. K(1) is bonded in a 10-coordinate geometry to four equivalent O(3) and six equivalent O(2) atoms. Fe(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent S(1)O4 tetrahedra. S(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-43°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(1) and one S(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to three equivalent K(1) and one S(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one K(1), one Fe(1), and one S(1) atom.
KFe(SO4)2 crystallizes in the monoclinic C2/m space group. K(1) is bonded in a 10-coordinate geometry to four equivalent O(3) and six equivalent O(2) atoms. All K(1)-O(3) bond lengths are 2.91 Å. There are two shorter (2.88 Å) and four longer (3.17 Å) K(1)-O(2) bond lengths. Fe(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent S(1)O4 tetrahedra. Both Fe(1)-O(1) bond lengths are 1.99 Å. All Fe(1)-O(3) bond lengths are 2.04 Å. S(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-43°. The S(1)-O(1) bond length is 1.49 Å. The S(1)-O(2) bond length is 1.46 Å. Both S(1)-O(3) bond lengths are 1.51 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(1) and one S(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to three equivalent K(1) and one S(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one K(1), one Fe(1), and one S(1) atom.