Tb4C2Br3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to two equivalent C(2), one Br(1), and three equivalent Br(2) atoms to form distorted TbC2Br4 octahedra that share corners with two equivalent Tb(4)C3Br3 octahedra, corners with two equivalent Tb(2)C4Br2 octahedra,  an edgeedge with one Tb(2)C4Br2 octahedra, edges with two equivalent Tb(3)C3Br3 octahedra, edges with three equivalent Tb(4)C3Br3 octahedra, and edges with four equivalent Tb(1)C2Br4 octahedra. The corner-sharing octahedral tilt angles are 4°. In the second Tb site, Tb(2) is bonded to two equivalent C(1), two equivalent C(2), and two equivalent Br(3) atoms to form TbC4Br2 octahedra that share corners with two equivalent Tb(1)C2Br4 octahedra, corners with two equivalent Tb(2)C4Br2 octahedra,  an edgeedge with one Tb(1)C2Br4 octahedra, edges with two equivalent Tb(2)C4Br2 octahedra, edges with four equivalent Tb(3)C3Br3 octahedra, and edges with four equivalent Tb(4)C3Br3 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. In the third Tb site, Tb(3) is bonded to one C(2), two equivalent C(1), one Br(3), and two equivalent Br(1) atoms to form distorted TbC3Br3 octahedra that share corners with four equivalent Tb(4)C3Br3 octahedra,  an edgeedge with one Tb(4)C3Br3 octahedra, edges with two equivalent Tb(1)C2Br4 octahedra, edges with two equivalent Tb(3)C3Br3 octahedra, and edges with four equivalent Tb(2)C4Br2 octahedra. The corner-sharing octahedral tilt angles range from 1-22°. In the fourth Tb site, Tb(4) is bonded to one C(2), two equivalent C(1), one Br(3), and two equivalent Br(2) atoms to form distorted TbC3Br3 octahedra that share corners with two equivalent Tb(1)C2Br4 octahedra, corners with four equivalent Tb(3)C3Br3 octahedra,  an edgeedge with one Tb(3)C3Br3 octahedra, edges with two equivalent Tb(4)C3Br3 octahedra, edges with three equivalent Tb(1)C2Br4 octahedra, and edges with four equivalent Tb(2)C4Br2 octahedra. The corner-sharing octahedral tilt angles range from 1-22°. There are two inequivalent C sites. In the first C site, C(1) is bonded to two equivalent Tb(2), two equivalent Tb(3), and two equivalent Tb(4) atoms to form a mixture of corner and edge-sharing CTb6 octahedra. The corner-sharing octahedral tilt angles are 5°. In the second C site, C(2) is bonded to one Tb(3), one Tb(4), two equivalent Tb(1), and two equivalent Tb(2) atoms to form edge-sharing CTb6 octahedra. There are three inequivalent Br sites. In the first Br site, Br(3) is bonded in a distorted square co-planar geometry to one Tb(3), one Tb(4), and two equivalent Tb(2) atoms. In the second Br site, Br(1) is bonded in a 3-coordinate geometry to one Tb(1) and two equivalent Tb(3) atoms. In the third Br site, Br(2) is bonded in a 5-coordinate geometry to two equivalent Tb(4) and three equivalent Tb(1) atoms.
Tb4C2Br3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to two equivalent C(2), one Br(1), and three equivalent Br(2) atoms to form distorted TbC2Br4 octahedra that share corners with two equivalent Tb(4)C3Br3 octahedra, corners with two equivalent Tb(2)C4Br2 octahedra,  an edgeedge with one Tb(2)C4Br2 octahedra, edges with two equivalent Tb(3)C3Br3 octahedra, edges with three equivalent Tb(4)C3Br3 octahedra, and edges with four equivalent Tb(1)C2Br4 octahedra. The corner-sharing octahedral tilt angles are 4°. Both Tb(1)-C(2) bond lengths are 2.42 Å. The Tb(1)-Br(1) bond length is 2.77 Å. There is one shorter (2.90 Å) and two longer (3.16 Å) Tb(1)-Br(2) bond lengths. In the second Tb site, Tb(2) is bonded to two equivalent C(1), two equivalent C(2), and two equivalent Br(3) atoms to form TbC4Br2 octahedra that share corners with two equivalent Tb(1)C2Br4 octahedra, corners with two equivalent Tb(2)C4Br2 octahedra,  an edgeedge with one Tb(1)C2Br4 octahedra, edges with two equivalent Tb(2)C4Br2 octahedra, edges with four equivalent Tb(3)C3Br3 octahedra, and edges with four equivalent Tb(4)C3Br3 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. There is one shorter (2.68 Å) and one longer (2.72 Å) Tb(2)-C(1) bond length. Both Tb(2)-C(2) bond lengths are 2.59 Å. Both Tb(2)-Br(3) bond lengths are 2.96 Å. In the third Tb site, Tb(3) is bonded to one C(2), two equivalent C(1), one Br(3), and two equivalent Br(1) atoms to form distorted TbC3Br3 octahedra that share corners with four equivalent Tb(4)C3Br3 octahedra,  an edgeedge with one Tb(4)C3Br3 octahedra, edges with two equivalent Tb(1)C2Br4 octahedra, edges with two equivalent Tb(3)C3Br3 octahedra, and edges with four equivalent Tb(2)C4Br2 octahedra. The corner-sharing octahedral tilt angles range from 1-22°. The Tb(3)-C(2) bond length is 2.56 Å. Both Tb(3)-C(1) bond lengths are 2.50 Å. The Tb(3)-Br(3) bond length is 2.93 Å. Both Tb(3)-Br(1) bond lengths are 2.98 Å. In the fourth Tb site, Tb(4) is bonded to one C(2), two equivalent C(1), one Br(3), and two equivalent Br(2) atoms to form distorted TbC3Br3 octahedra that share corners with two equivalent Tb(1)C2Br4 octahedra, corners with four equivalent Tb(3)C3Br3 octahedra,  an edgeedge with one Tb(3)C3Br3 octahedra, edges with two equivalent Tb(4)C3Br3 octahedra, edges with three equivalent Tb(1)C2Br4 octahedra, and edges with four equivalent Tb(2)C4Br2 octahedra. The corner-sharing octahedral tilt angles range from 1-22°. The Tb(4)-C(2) bond length is 2.54 Å. Both Tb(4)-C(1) bond lengths are 2.45 Å. The Tb(4)-Br(3) bond length is 2.91 Å. Both Tb(4)-Br(2) bond lengths are 3.15 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded to two equivalent Tb(2), two equivalent Tb(3), and two equivalent Tb(4) atoms to form a mixture of corner and edge-sharing CTb6 octahedra. The corner-sharing octahedral tilt angles are 5°. In the second C site, C(2) is bonded to one Tb(3), one Tb(4), two equivalent Tb(1), and two equivalent Tb(2) atoms to form edge-sharing CTb6 octahedra. There are three inequivalent Br sites. In the first Br site, Br(3) is bonded in a distorted square co-planar geometry to one Tb(3), one Tb(4), and two equivalent Tb(2) atoms. In the second Br site, Br(1) is bonded in a 3-coordinate geometry to one Tb(1) and two equivalent Tb(3) atoms. In the third Br site, Br(2) is bonded in a 5-coordinate geometry to two equivalent Tb(4) and three equivalent Tb(1) atoms.