Co2(SnSe)3 is Sylvanite-like structured and crystallizes in the trigonal R-3 space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one Sn(1), two equivalent Sn(2), one Se(2), and two equivalent Se(1) atoms to form CoSn3Se3 octahedra that share corners with two equivalent Co(2)Sn3Se3 octahedra, corners with four equivalent Co(1)Sn3Se3 octahedra, and corners with four equivalent Se(2)Co2Sn2 tetrahedra. The corner-sharing octahedral tilt angles range from 51-56°. In the second Co site, Co(2) is bonded to three equivalent Sn(1) and three equivalent Se(2) atoms to form corner-sharing CoSn3Se3 octahedra. The corner-sharing octahedral tilt angles range from 51-56°. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 4-coordinate geometry to one Co(1), one Co(2), and two equivalent Se(1) atoms. In the second Sn site, Sn(2) is bonded in a 4-coordinate geometry to two equivalent Co(1) and two equivalent Se(2) atoms. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to two equivalent Co(1) and two equivalent Sn(1) atoms. In the second Se site, Se(2) is bonded to one Co(1), one Co(2), and two equivalent Sn(2) atoms to form distorted SeCo2Sn2 tetrahedra that share corners with four equivalent Co(1)Sn3Se3 octahedra, corners with two equivalent Se(2)Co2Sn2 tetrahedra, and  an edgeedge with one Se(2)Co2Sn2 tetrahedra. The corner-sharing octahedral tilt angles range from 68-74°.
Co2(SnSe)3 is Sylvanite-like structured and crystallizes in the trigonal R-3 space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one Sn(1), two equivalent Sn(2), one Se(2), and two equivalent Se(1) atoms to form CoSn3Se3 octahedra that share corners with two equivalent Co(2)Sn3Se3 octahedra, corners with four equivalent Co(1)Sn3Se3 octahedra, and corners with four equivalent Se(2)Co2Sn2 tetrahedra. The corner-sharing octahedral tilt angles range from 51-56°. The Co(1)-Sn(1) bond length is 2.50 Å. There is one shorter (2.48 Å) and one longer (2.52 Å) Co(1)-Sn(2) bond length. The Co(1)-Se(2) bond length is 2.41 Å. There is one shorter (2.38 Å) and one longer (2.41 Å) Co(1)-Se(1) bond length. In the second Co site, Co(2) is bonded to three equivalent Sn(1) and three equivalent Se(2) atoms to form corner-sharing CoSn3Se3 octahedra. The corner-sharing octahedral tilt angles range from 51-56°. All Co(2)-Sn(1) bond lengths are 2.50 Å. All Co(2)-Se(2) bond lengths are 2.39 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 4-coordinate geometry to one Co(1), one Co(2), and two equivalent Se(1) atoms. There is one shorter (2.72 Å) and one longer (2.90 Å) Sn(1)-Se(1) bond length. In the second Sn site, Sn(2) is bonded in a 4-coordinate geometry to two equivalent Co(1) and two equivalent Se(2) atoms. There is one shorter (2.71 Å) and one longer (2.89 Å) Sn(2)-Se(2) bond length. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to two equivalent Co(1) and two equivalent Sn(1) atoms. In the second Se site, Se(2) is bonded to one Co(1), one Co(2), and two equivalent Sn(2) atoms to form distorted SeCo2Sn2 tetrahedra that share corners with four equivalent Co(1)Sn3Se3 octahedra, corners with two equivalent Se(2)Co2Sn2 tetrahedra, and  an edgeedge with one Se(2)Co2Sn2 tetrahedra. The corner-sharing octahedral tilt angles range from 68-74°.