Hf3CoS6 crystallizes in the trigonal R-3 space group. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to six equivalent S(1) atoms to form HfS6 octahedra that share corners with six equivalent Co(1)S6 octahedra and edges with six equivalent Hf(2)S6 octahedra. The corner-sharing octahedral tilt angles are 47°. In the second Hf site, Hf(2) is bonded to six equivalent S(1) atoms to form HfS6 octahedra that share corners with three equivalent Co(1)S6 octahedra, edges with three equivalent Hf(1)S6 octahedra, edges with three equivalent Hf(2)S6 octahedra, and  a faceface with one Co(1)S6 octahedra. The corner-sharing octahedral tilt angles are 49°. Co(1) is bonded to six equivalent S(1) atoms to form CoS6 octahedra that share corners with six equivalent Hf(1)S6 octahedra, corners with six equivalent Hf(2)S6 octahedra, and faces with two equivalent Hf(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 47-49°. S(1) is bonded in a rectangular see-saw-like geometry to one Hf(1), two equivalent Hf(2), and one Co(1) atom.
Hf3CoS6 crystallizes in the trigonal R-3 space group. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to six equivalent S(1) atoms to form HfS6 octahedra that share corners with six equivalent Co(1)S6 octahedra and edges with six equivalent Hf(2)S6 octahedra. The corner-sharing octahedral tilt angles are 47°. All Hf(1)-S(1) bond lengths are 2.56 Å. In the second Hf site, Hf(2) is bonded to six equivalent S(1) atoms to form HfS6 octahedra that share corners with three equivalent Co(1)S6 octahedra, edges with three equivalent Hf(1)S6 octahedra, edges with three equivalent Hf(2)S6 octahedra, and  a faceface with one Co(1)S6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are three shorter (2.54 Å) and three longer (2.57 Å) Hf(2)-S(1) bond lengths. Co(1) is bonded to six equivalent S(1) atoms to form CoS6 octahedra that share corners with six equivalent Hf(1)S6 octahedra, corners with six equivalent Hf(2)S6 octahedra, and faces with two equivalent Hf(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 47-49°. All Co(1)-S(1) bond lengths are 2.43 Å. S(1) is bonded in a rectangular see-saw-like geometry to one Hf(1), two equivalent Hf(2), and one Co(1) atom.