FeTh2S5 crystallizes in the monoclinic C2/c space group. Th(1) is bonded in a 8-coordinate geometry to two equivalent S(1), three equivalent S(2), and three equivalent S(3) atoms. Fe(1) is bonded to two equivalent S(2) and four equivalent S(3) atoms to form corner-sharing FeS6 octahedra. The corner-sharing octahedral tilt angles are 38°. There are three inequivalent S sites. In the first S site, S(1) is bonded to four equivalent Th(1) atoms to form STh4 trigonal pyramids that share corners with eight equivalent S(3)Th3Fe2 trigonal bipyramids, edges with two equivalent S(3)Th3Fe2 trigonal bipyramids, and edges with two equivalent S(1)Th4 trigonal pyramids. In the second S site, S(2) is bonded in a 4-coordinate geometry to three equivalent Th(1) and one Fe(1) atom. In the third S site, S(3) is bonded to three equivalent Th(1) and two equivalent Fe(1) atoms to form distorted STh3Fe2 trigonal bipyramids that share corners with two equivalent S(3)Th3Fe2 trigonal bipyramids, corners with four equivalent S(1)Th4 trigonal pyramids, edges with five equivalent S(3)Th3Fe2 trigonal bipyramids, and  an edgeedge with one S(1)Th4 trigonal pyramid.
FeTh2S5 crystallizes in the monoclinic C2/c space group. Th(1) is bonded in a 8-coordinate geometry to two equivalent S(1), three equivalent S(2), and three equivalent S(3) atoms. There is one shorter (2.85 Å) and one longer (2.86 Å) Th(1)-S(1) bond length. There are a spread of Th(1)-S(2) bond distances ranging from 2.78-3.12 Å. There are a spread of Th(1)-S(3) bond distances ranging from 2.89-2.94 Å. Fe(1) is bonded to two equivalent S(2) and four equivalent S(3) atoms to form corner-sharing FeS6 octahedra. The corner-sharing octahedral tilt angles are 38°. Both Fe(1)-S(2) bond lengths are 2.50 Å. There are two shorter (2.50 Å) and two longer (2.60 Å) Fe(1)-S(3) bond lengths. There are three inequivalent S sites. In the first S site, S(1) is bonded to four equivalent Th(1) atoms to form STh4 trigonal pyramids that share corners with eight equivalent S(3)Th3Fe2 trigonal bipyramids, edges with two equivalent S(3)Th3Fe2 trigonal bipyramids, and edges with two equivalent S(1)Th4 trigonal pyramids. In the second S site, S(2) is bonded in a 4-coordinate geometry to three equivalent Th(1) and one Fe(1) atom. In the third S site, S(3) is bonded to three equivalent Th(1) and two equivalent Fe(1) atoms to form distorted STh3Fe2 trigonal bipyramids that share corners with two equivalent S(3)Th3Fe2 trigonal bipyramids, corners with four equivalent S(1)Th4 trigonal pyramids, edges with five equivalent S(3)Th3Fe2 trigonal bipyramids, and  an edgeedge with one S(1)Th4 trigonal pyramid.