B12C2Mg crystallizes in the orthorhombic Imma space group. Mg(1) is bonded in a 2-coordinate geometry to eight equivalent B(3) and two equivalent C(1) atoms. There are four inequivalent B sites. In the first B site, B(1) is bonded in a distorted single-bond geometry to one B(4), two equivalent B(3), and one C(1) atom. In the second B site, B(2) is bonded in a distorted single-bond geometry to one B(4), two equivalent B(3), and one C(1) atom. In the third B site, B(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), one B(2), one B(4), two equivalent B(1), and two equivalent B(3) atoms. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(2), one B(4), two equivalent B(1), and two equivalent B(3) atoms. C(1) is bonded in a 5-coordinate geometry to one Mg(1), one B(2), two equivalent B(1), and one C(1) atom.
B12C2Mg crystallizes in the orthorhombic Imma space group. Mg(1) is bonded in a 2-coordinate geometry to eight equivalent B(3) and two equivalent C(1) atoms. There are four shorter (2.59 Å) and four longer (2.64 Å) Mg(1)-B(3) bond lengths. Both Mg(1)-C(1) bond lengths are 2.28 Å. There are four inequivalent B sites. In the first B site, B(1) is bonded in a distorted single-bond geometry to one B(4), two equivalent B(3), and one C(1) atom. The B(1)-B(4) bond length is 1.76 Å. Both B(1)-B(3) bond lengths are 1.78 Å. The B(1)-C(1) bond length is 1.66 Å. In the second B site, B(2) is bonded in a distorted single-bond geometry to one B(4), two equivalent B(3), and one C(1) atom. The B(2)-B(4) bond length is 1.75 Å. Both B(2)-B(3) bond lengths are 1.80 Å. The B(2)-C(1) bond length is 1.64 Å. In the third B site, B(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), one B(2), one B(4), two equivalent B(1), and two equivalent B(3) atoms. The B(3)-B(4) bond length is 1.75 Å. There is one shorter (1.73 Å) and one longer (1.81 Å) B(3)-B(3) bond length. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(2), one B(4), two equivalent B(1), and two equivalent B(3) atoms. The B(4)-B(4) bond length is 1.63 Å. C(1) is bonded in a 5-coordinate geometry to one Mg(1), one B(2), two equivalent B(1), and one C(1) atom. The C(1)-C(1) bond length is 1.73 Å.