Tb3Si2S8I crystallizes in the monoclinic C2/c space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 9-coordinate geometry to one S(3), two equivalent S(2), two equivalent S(4), three equivalent S(1), and one I(1) atom. In the second Tb site, Tb(2) is bonded in a 9-coordinate geometry to two equivalent S(2), two equivalent S(4), four equivalent S(3), and one I(1) atom. Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(4) atom. There are four inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to three equivalent Tb(1) and one Si(1) atom. In the second S site, S(2) is bonded to one Tb(2), two equivalent Tb(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing STb3Si trigonal pyramids. In the third S site, S(3) is bonded in a 4-coordinate geometry to one Tb(1), two equivalent Tb(2), and one Si(1) atom. In the fourth S site, S(4) is bonded to one Tb(2), two equivalent Tb(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing STb3Si trigonal pyramids. I(1) is bonded in a 3-coordinate geometry to one Tb(2) and two equivalent Tb(1) atoms.
Tb3Si2S8I crystallizes in the monoclinic C2/c space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 9-coordinate geometry to one S(3), two equivalent S(2), two equivalent S(4), three equivalent S(1), and one I(1) atom. The Tb(1)-S(3) bond length is 2.91 Å. There is one shorter (2.86 Å) and one longer (2.95 Å) Tb(1)-S(2) bond length. There is one shorter (2.98 Å) and one longer (3.03 Å) Tb(1)-S(4) bond length. There are a spread of Tb(1)-S(1) bond distances ranging from 2.87-2.95 Å. The Tb(1)-I(1) bond length is 3.48 Å. In the second Tb site, Tb(2) is bonded in a 9-coordinate geometry to two equivalent S(2), two equivalent S(4), four equivalent S(3), and one I(1) atom. Both Tb(2)-S(2) bond lengths are 2.84 Å. Both Tb(2)-S(4) bond lengths are 2.88 Å. There are two shorter (3.09 Å) and two longer (3.42 Å) Tb(2)-S(3) bond lengths. The Tb(2)-I(1) bond length is 3.12 Å. Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(4) atom. The Si(1)-S(1) bond length is 2.13 Å. The Si(1)-S(2) bond length is 2.12 Å. The Si(1)-S(3) bond length is 2.12 Å. The Si(1)-S(4) bond length is 2.12 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to three equivalent Tb(1) and one Si(1) atom. In the second S site, S(2) is bonded to one Tb(2), two equivalent Tb(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing STb3Si trigonal pyramids. In the third S site, S(3) is bonded in a 4-coordinate geometry to one Tb(1), two equivalent Tb(2), and one Si(1) atom. In the fourth S site, S(4) is bonded to one Tb(2), two equivalent Tb(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing STb3Si trigonal pyramids. I(1) is bonded in a 3-coordinate geometry to one Tb(2) and two equivalent Tb(1) atoms.