FeB6O6 crystallizes in the monoclinic C2/m space group. Fe(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(1) atoms. There are two inequivalent B sites. In the first B site, B(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form edge-sharing BO4 tetrahedra. In the second B site, B(2) is bonded in a distorted L-shaped geometry to two equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Fe(1), one B(1), and two equivalent B(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Fe(1) and two equivalent B(1) atoms.
FeB6O6 crystallizes in the monoclinic C2/m space group. Fe(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(1) atoms. Both Fe(1)-O(2) bond lengths are 2.11 Å. All Fe(1)-O(1) bond lengths are 2.31 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form edge-sharing BO4 tetrahedra. Both B(1)-O(1) bond lengths are 1.49 Å. There is one shorter (1.46 Å) and one longer (1.48 Å) B(1)-O(2) bond length. In the second B site, B(2) is bonded in a distorted L-shaped geometry to two equivalent O(1) atoms. There is one shorter (1.59 Å) and one longer (1.70 Å) B(2)-O(1) bond length. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Fe(1), one B(1), and two equivalent B(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Fe(1) and two equivalent B(1) atoms.