BaSr(FeO2)4 crystallizes in the trigonal P-31m space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share edges with six equivalent Ba(1)O12 cuboctahedra, edges with twelve equivalent Fe(1)O4 tetrahedra, and faces with two equivalent Sr(1)O6 octahedra. Sr(1) is bonded to six equivalent O(1) atoms to form SrO6 octahedra that share corners with twelve equivalent Fe(1)O4 tetrahedra and faces with two equivalent Ba(1)O12 cuboctahedra. Fe(1) is bonded to one O(2) and three equivalent O(1) atoms to form FeO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra, corners with four equivalent Fe(1)O4 tetrahedra, and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 58°. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Ba(1), one Sr(1), and two equivalent Fe(1) atoms to form a mixture of distorted corner and edge-sharing OBaSrFe2 trigonal pyramids. In the second O site, O(2) is bonded in a linear geometry to three equivalent Ba(1) and two equivalent Fe(1) atoms.
BaSr(FeO2)4 crystallizes in the trigonal P-31m space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share edges with six equivalent Ba(1)O12 cuboctahedra, edges with twelve equivalent Fe(1)O4 tetrahedra, and faces with two equivalent Sr(1)O6 octahedra. All Ba(1)-O(1) bond lengths are 3.05 Å. All Ba(1)-O(2) bond lengths are 3.21 Å. Sr(1) is bonded to six equivalent O(1) atoms to form SrO6 octahedra that share corners with twelve equivalent Fe(1)O4 tetrahedra and faces with two equivalent Ba(1)O12 cuboctahedra. All Sr(1)-O(1) bond lengths are 2.54 Å. Fe(1) is bonded to one O(2) and three equivalent O(1) atoms to form FeO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra, corners with four equivalent Fe(1)O4 tetrahedra, and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 58°. The Fe(1)-O(2) bond length is 1.88 Å. All Fe(1)-O(1) bond lengths are 1.91 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Ba(1), one Sr(1), and two equivalent Fe(1) atoms to form a mixture of distorted corner and edge-sharing OBaSrFe2 trigonal pyramids. In the second O site, O(2) is bonded in a linear geometry to three equivalent Ba(1) and two equivalent Fe(1) atoms.