Nb6C5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one C(1), two equivalent C(2), and two equivalent C(3) atoms to form a mixture of corner and edge-sharing NbC5 square pyramids. In the second Nb site, Nb(2) is bonded to one C(1), two equivalent C(2), and two equivalent C(3) atoms to form a mixture of corner and edge-sharing NbC5 square pyramids. There are three inequivalent C sites. In the first C site, C(1) is bonded to two equivalent Nb(1) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles are 5°. In the second C site, C(2) is bonded to two equivalent Nb(1) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles range from 5-7°. In the third C site, C(3) is bonded to two equivalent Nb(1) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles range from 6-7°.
Nb6C5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one C(1), two equivalent C(2), and two equivalent C(3) atoms to form a mixture of corner and edge-sharing NbC5 square pyramids. The Nb(1)-C(1) bond length is 2.12 Å. Both Nb(1)-C(2) bond lengths are 2.24 Å. Both Nb(1)-C(3) bond lengths are 2.25 Å. In the second Nb site, Nb(2) is bonded to one C(1), two equivalent C(2), and two equivalent C(3) atoms to form a mixture of corner and edge-sharing NbC5 square pyramids. The Nb(2)-C(1) bond length is 2.29 Å. There is one shorter (2.22 Å) and one longer (2.23 Å) Nb(2)-C(2) bond length. There is one shorter (2.15 Å) and one longer (2.28 Å) Nb(2)-C(3) bond length. There are three inequivalent C sites. In the first C site, C(1) is bonded to two equivalent Nb(1) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles are 5°. In the second C site, C(2) is bonded to two equivalent Nb(1) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles range from 5-7°. In the third C site, C(3) is bonded to two equivalent Nb(1) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing CNb6 octahedra. The corner-sharing octahedral tilt angles range from 6-7°.