Fe(BO2)2 crystallizes in the monoclinic C2/c space group. Fe(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form FeO6 octahedra that share corners with twelve equivalent B(1)O4 tetrahedra and edges with two equivalent Fe(1)O6 octahedra. B(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form BO4 tetrahedra that share corners with six equivalent Fe(1)O6 octahedra, corners with two equivalent B(1)O4 tetrahedra, and  an edgeedge with one B(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-63°. There are two inequivalent O sites. In the first O site, O(2) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent B(1) atoms. In the second O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Fe(1) and two equivalent B(1) atoms.
Fe(BO2)2 crystallizes in the monoclinic C2/c space group. Fe(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form FeO6 octahedra that share corners with twelve equivalent B(1)O4 tetrahedra and edges with two equivalent Fe(1)O6 octahedra. Both Fe(1)-O(2) bond lengths are 2.11 Å. There are two shorter (2.09 Å) and two longer (2.24 Å) Fe(1)-O(1) bond lengths. B(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form BO4 tetrahedra that share corners with six equivalent Fe(1)O6 octahedra, corners with two equivalent B(1)O4 tetrahedra, and  an edgeedge with one B(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-63°. There is one shorter (1.51 Å) and one longer (1.53 Å) B(1)-O(1) bond length. Both B(1)-O(2) bond lengths are 1.44 Å. There are two inequivalent O sites. In the first O site, O(2) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent B(1) atoms. In the second O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Fe(1) and two equivalent B(1) atoms.