FeB4 crystallizes in the orthorhombic Pnnm space group. Fe(1) is bonded to six equivalent B(1) and six equivalent B(2) atoms to form a mixture of edge and face-sharing FeB12 cuboctahedra. There are two inequivalent B sites. In the first B site, B(1) is bonded in a 8-coordinate geometry to three equivalent Fe(1), one B(1), and four equivalent B(2) atoms. In the second B site, B(2) is bonded in a 7-coordinate geometry to three equivalent Fe(1) and four equivalent B(1) atoms.
FeB4 crystallizes in the orthorhombic Pnnm space group. Fe(1) is bonded to six equivalent B(1) and six equivalent B(2) atoms to form a mixture of edge and face-sharing FeB12 cuboctahedra. There are two shorter (2.09 Å) and four longer (2.24 Å) Fe(1)-B(1) bond lengths. There are two shorter (1.99 Å) and four longer (2.12 Å) Fe(1)-B(2) bond lengths. There are two inequivalent B sites. In the first B site, B(1) is bonded in a 8-coordinate geometry to three equivalent Fe(1), one B(1), and four equivalent B(2) atoms. The B(1)-B(1) bond length is 1.98 Å. There are a spread of B(1)-B(2) bond distances ranging from 1.70-1.88 Å. In the second B site, B(2) is bonded in a 7-coordinate geometry to three equivalent Fe(1) and four equivalent B(1) atoms.