CuBi5S8 crystallizes in the monoclinic C2 space group. Cu(1) is bonded to two equivalent S(3) and two equivalent S(4) atoms to form distorted CuS4 tetrahedra that share corners with two equivalent Bi(1)S6 octahedra, corners with six equivalent Bi(2)S5 square pyramids, and edges with two equivalent Bi(2)S5 square pyramids. The corner-sharing octahedral tilt angles are 51°. There are three inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one S(3), two equivalent S(2), and three equivalent S(1) atoms to form BiS6 octahedra that share corners with two equivalent Bi(3)S6 octahedra, corners with two equivalent Bi(2)S5 square pyramids,  a cornercorner with one Cu(1)S4 tetrahedra, edges with three equivalent Bi(3)S6 octahedra, and edges with four equivalent Bi(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. In the second Bi site, Bi(2) is bonded to two equivalent S(3) and three equivalent S(4) atoms to form BiS5 square pyramids that share corners with two equivalent Bi(1)S6 octahedra, corners with three equivalent Cu(1)S4 tetrahedra, edges with four equivalent Bi(2)S5 square pyramids, and  an edgeedge with one Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 70-71°. In the third Bi site, Bi(3) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form a mixture of edge and corner-sharing BiS6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Bi(3) and three equivalent Bi(1) atoms to form SBi5 square pyramids that share corners with two equivalent S(1)Bi5 square pyramids, corners with three equivalent S(3)CuBi3 trigonal pyramids, and edges with five equivalent S(1)Bi5 square pyramids. In the second S site, S(2) is bonded in a distorted T-shaped geometry to one Bi(3) and two equivalent Bi(1) atoms. In the third S site, S(3) is bonded to one Cu(1), one Bi(1), and two equivalent Bi(2) atoms to form distorted SCuBi3 trigonal pyramids that share corners with three equivalent S(1)Bi5 square pyramids and corners with three equivalent S(3)CuBi3 trigonal pyramids. In the fourth S site, S(4) is bonded in a distorted rectangular see-saw-like geometry to one Cu(1) and three equivalent Bi(2) atoms.
CuBi5S8 crystallizes in the monoclinic C2 space group. Cu(1) is bonded to two equivalent S(3) and two equivalent S(4) atoms to form distorted CuS4 tetrahedra that share corners with two equivalent Bi(1)S6 octahedra, corners with six equivalent Bi(2)S5 square pyramids, and edges with two equivalent Bi(2)S5 square pyramids. The corner-sharing octahedral tilt angles are 51°. Both Cu(1)-S(3) bond lengths are 2.35 Å. Both Cu(1)-S(4) bond lengths are 2.37 Å. There are three inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one S(3), two equivalent S(2), and three equivalent S(1) atoms to form BiS6 octahedra that share corners with two equivalent Bi(3)S6 octahedra, corners with two equivalent Bi(2)S5 square pyramids,  a cornercorner with one Cu(1)S4 tetrahedra, edges with three equivalent Bi(3)S6 octahedra, and edges with four equivalent Bi(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. The Bi(1)-S(3) bond length is 2.69 Å. There is one shorter (2.72 Å) and one longer (2.73 Å) Bi(1)-S(2) bond length. There are a spread of Bi(1)-S(1) bond distances ranging from 2.99-3.16 Å. In the second Bi site, Bi(2) is bonded to two equivalent S(3) and three equivalent S(4) atoms to form BiS5 square pyramids that share corners with two equivalent Bi(1)S6 octahedra, corners with three equivalent Cu(1)S4 tetrahedra, edges with four equivalent Bi(2)S5 square pyramids, and  an edgeedge with one Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 70-71°. There is one shorter (2.83 Å) and one longer (2.88 Å) Bi(2)-S(3) bond length. There are a spread of Bi(2)-S(4) bond distances ranging from 2.60-2.97 Å. In the third Bi site, Bi(3) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form a mixture of edge and corner-sharing BiS6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. Both Bi(3)-S(2) bond lengths are 2.83 Å. There are two shorter (2.83 Å) and two longer (2.84 Å) Bi(3)-S(1) bond lengths. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Bi(3) and three equivalent Bi(1) atoms to form SBi5 square pyramids that share corners with two equivalent S(1)Bi5 square pyramids, corners with three equivalent S(3)CuBi3 trigonal pyramids, and edges with five equivalent S(1)Bi5 square pyramids. In the second S site, S(2) is bonded in a distorted T-shaped geometry to one Bi(3) and two equivalent Bi(1) atoms. In the third S site, S(3) is bonded to one Cu(1), one Bi(1), and two equivalent Bi(2) atoms to form distorted SCuBi3 trigonal pyramids that share corners with three equivalent S(1)Bi5 square pyramids and corners with three equivalent S(3)CuBi3 trigonal pyramids. In the fourth S site, S(4) is bonded in a distorted rectangular see-saw-like geometry to one Cu(1) and three equivalent Bi(2) atoms.