Ta6V3Ni3C2 crystallizes in the orthorhombic Imm2 space group. There are six inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 2-coordinate geometry to two equivalent V(2), two equivalent V(3), two equivalent Ni(3), and two equivalent C(1) atoms. In the second Ta site, Ta(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Ni(1), two equivalent Ni(2), and two equivalent C(2) atoms. In the third Ta site, Ta(3) is bonded in a distorted bent 150 degrees geometry to one V(2), one V(3), one Ni(1), one Ni(2), one Ni(3), one C(1), and one C(2) atom. In the fourth Ta site, Ta(4) is bonded in a distorted bent 150 degrees geometry to two equivalent V(2), two equivalent Ni(1), two equivalent Ni(2), and two equivalent C(1) atoms. In the fifth Ta site, Ta(5) is bonded in a distorted bent 150 degrees geometry to two equivalent V(3), two equivalent Ni(3), and two equivalent C(2) atoms. In the sixth Ta site, Ta(6) is bonded in a distorted bent 150 degrees geometry to one V(2), one V(3), one Ni(1), one Ni(2), one Ni(3), one C(1), and one C(2) atom. There are three inequivalent V sites. In the first V site, V(1) is bonded in a 5-coordinate geometry to one V(3), one Ni(2), two equivalent Ni(1), and two equivalent Ni(3) atoms. In the second V site, V(2) is bonded to one Ta(1), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), two equivalent V(3), one Ni(1), one Ni(3), and two equivalent Ni(2) atoms to form distorted VTa6V2Ni4 cuboctahedra that share corners with three equivalent Ni(1)Ta6V5Ni cuboctahedra, edges with two equivalent C(2)Ta6 octahedra, edges with four equivalent C(1)Ta6 octahedra, faces with two equivalent V(2)Ta6V2Ni4 cuboctahedra, faces with two equivalent V(3)Ta6V4Ni2 cuboctahedra, and faces with two equivalent Ni(1)Ta6V5Ni cuboctahedra. In the third V site, V(3) is bonded to one Ta(1), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one V(1), one V(3), two equivalent V(2), and two equivalent Ni(1) atoms to form distorted VTa6V4Ni2 cuboctahedra that share  a cornercorner with one V(3)Ta6V4Ni2 cuboctahedra, corners with two equivalent Ni(1)Ta6V5Ni cuboctahedra, corners with three equivalent C(1)Ta6 octahedra,  a faceface with one V(3)Ta6V4Ni2 cuboctahedra, faces with two equivalent V(2)Ta6V2Ni4 cuboctahedra, faces with two equivalent Ni(1)Ta6V5Ni cuboctahedra,  a faceface with one C(1)Ta6 octahedra, and faces with two equivalent C(2)Ta6 octahedra. The corner-sharing octahedral tilt angles range from 42-44°. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one Ta(2), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), one V(2), two equivalent V(1), two equivalent V(3), and one Ni(1) atom to form distorted NiTa6V5Ni cuboctahedra that share  a cornercorner with one Ni(1)Ta6V5Ni cuboctahedra, corners with two equivalent V(3)Ta6V4Ni2 cuboctahedra, corners with three equivalent V(2)Ta6V2Ni4 cuboctahedra, corners with three equivalent C(2)Ta6 octahedra,  a faceface with one Ni(1)Ta6V5Ni cuboctahedra, faces with two equivalent V(2)Ta6V2Ni4 cuboctahedra, faces with two equivalent V(3)Ta6V4Ni2 cuboctahedra,  a faceface with one C(2)Ta6 octahedra, and faces with two equivalent C(1)Ta6 octahedra. The corner-sharing octahedral tilt angles range from 44-46°. In the second Ni site, Ni(2) is bonded in a 12-coordinate geometry to one Ta(2), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), one V(1), two equivalent V(2), one Ni(2), and two equivalent Ni(3) atoms. In the third Ni site, Ni(3) is bonded in a 12-coordinate geometry to one Ta(1), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one V(2), two equivalent V(1), one Ni(3), and two equivalent Ni(2) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Ta(1), one Ta(4), two equivalent Ta(3), and two equivalent Ta(6) atoms to form CTa6 octahedra that share corners with three equivalent V(3)Ta6V4Ni2 cuboctahedra, corners with two equivalent C(1)Ta6 octahedra, corners with four equivalent C(2)Ta6 octahedra, edges with four equivalent V(2)Ta6V2Ni4 cuboctahedra,  a faceface with one V(3)Ta6V4Ni2 cuboctahedra, and faces with two equivalent Ni(1)Ta6V5Ni cuboctahedra. The corner-sharing octahedral tilt angles range from 38-42°. In the second C site, C(2) is bonded to one Ta(2), one Ta(5), two equivalent Ta(3), and two equivalent Ta(6) atoms to form CTa6 octahedra that share corners with three equivalent Ni(1)Ta6V5Ni cuboctahedra, corners with two equivalent C(2)Ta6 octahedra, corners with four equivalent C(1)Ta6 octahedra, edges with two equivalent V(2)Ta6V2Ni4 cuboctahedra,  a faceface with one Ni(1)Ta6V5Ni cuboctahedra, and faces with two equivalent V(3)Ta6V4Ni2 cuboctahedra. The corner-sharing octahedral tilt angles range from 37-42°.
Ta6V3Ni3C2 crystallizes in the orthorhombic Imm2 space group. There are six inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 2-coordinate geometry to two equivalent V(2), two equivalent V(3), two equivalent Ni(3), and two equivalent C(1) atoms. Both Ta(1)-V(2) bond lengths are 2.97 Å. Both Ta(1)-V(3) bond lengths are 2.93 Å. Both Ta(1)-Ni(3) bond lengths are 2.78 Å. Both Ta(1)-C(1) bond lengths are 2.19 Å. In the second Ta site, Ta(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Ni(1), two equivalent Ni(2), and two equivalent C(2) atoms. Both Ta(2)-Ni(1) bond lengths are 2.99 Å. Both Ta(2)-Ni(2) bond lengths are 2.80 Å. Both Ta(2)-C(2) bond lengths are 2.15 Å. In the third Ta site, Ta(3) is bonded in a distorted bent 150 degrees geometry to one V(2), one V(3), one Ni(1), one Ni(2), one Ni(3), one C(1), and one C(2) atom. The Ta(3)-V(2) bond length is 2.94 Å. The Ta(3)-V(3) bond length is 2.95 Å. The Ta(3)-Ni(1) bond length is 2.98 Å. The Ta(3)-Ni(2) bond length is 2.81 Å. The Ta(3)-Ni(3) bond length is 2.78 Å. The Ta(3)-C(1) bond length is 2.18 Å. The Ta(3)-C(2) bond length is 2.17 Å. In the fourth Ta site, Ta(4) is bonded in a distorted bent 150 degrees geometry to two equivalent V(2), two equivalent Ni(1), two equivalent Ni(2), and two equivalent C(1) atoms. Both Ta(4)-V(2) bond lengths are 2.94 Å. Both Ta(4)-Ni(1) bond lengths are 2.81 Å. Both Ta(4)-Ni(2) bond lengths are 3.02 Å. Both Ta(4)-C(1) bond lengths are 2.15 Å. In the fifth Ta site, Ta(5) is bonded in a distorted bent 150 degrees geometry to two equivalent V(3), two equivalent Ni(3), and two equivalent C(2) atoms. Both Ta(5)-V(3) bond lengths are 2.77 Å. Both Ta(5)-Ni(3) bond lengths are 2.95 Å. Both Ta(5)-C(2) bond lengths are 2.17 Å. In the sixth Ta site, Ta(6) is bonded in a distorted bent 150 degrees geometry to one V(2), one V(3), one Ni(1), one Ni(2), one Ni(3), one C(1), and one C(2) atom. The Ta(6)-V(2) bond length is 2.98 Å. The Ta(6)-V(3) bond length is 2.78 Å. The Ta(6)-Ni(1) bond length is 2.80 Å. The Ta(6)-Ni(2) bond length is 2.96 Å. The Ta(6)-Ni(3) bond length is 2.96 Å. The Ta(6)-C(1) bond length is 2.17 Å. The Ta(6)-C(2) bond length is 2.16 Å. There are three inequivalent V sites. In the first V site, V(1) is bonded in a 5-coordinate geometry to one V(3), one Ni(2), two equivalent Ni(1), and two equivalent Ni(3) atoms. The V(1)-V(3) bond length is 2.54 Å. The V(1)-Ni(2) bond length is 2.39 Å. Both V(1)-Ni(1) bond lengths are 2.47 Å. Both V(1)-Ni(3) bond lengths are 2.46 Å. In the second V site, V(2) is bonded to one Ta(1), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), two equivalent V(3), one Ni(1), one Ni(3), and two equivalent Ni(2) atoms to form distorted VTa6V2Ni4 cuboctahedra that share corners with three equivalent Ni(1)Ta6V5Ni cuboctahedra, edges with two equivalent C(2)Ta6 octahedra, edges with four equivalent C(1)Ta6 octahedra, faces with two equivalent V(2)Ta6V2Ni4 cuboctahedra, faces with two equivalent V(3)Ta6V4Ni2 cuboctahedra, and faces with two equivalent Ni(1)Ta6V5Ni cuboctahedra. Both V(2)-V(3) bond lengths are 2.53 Å. The V(2)-Ni(1) bond length is 2.50 Å. The V(2)-Ni(3) bond length is 2.46 Å. Both V(2)-Ni(2) bond lengths are 2.41 Å. In the third V site, V(3) is bonded to one Ta(1), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one V(1), one V(3), two equivalent V(2), and two equivalent Ni(1) atoms to form distorted VTa6V4Ni2 cuboctahedra that share  a cornercorner with one V(3)Ta6V4Ni2 cuboctahedra, corners with two equivalent Ni(1)Ta6V5Ni cuboctahedra, corners with three equivalent C(1)Ta6 octahedra,  a faceface with one V(3)Ta6V4Ni2 cuboctahedra, faces with two equivalent V(2)Ta6V2Ni4 cuboctahedra, faces with two equivalent Ni(1)Ta6V5Ni cuboctahedra,  a faceface with one C(1)Ta6 octahedra, and faces with two equivalent C(2)Ta6 octahedra. The corner-sharing octahedral tilt angles range from 42-44°. The V(3)-V(3) bond length is 2.64 Å. Both V(3)-Ni(1) bond lengths are 2.59 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one Ta(2), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), one V(2), two equivalent V(1), two equivalent V(3), and one Ni(1) atom to form distorted NiTa6V5Ni cuboctahedra that share  a cornercorner with one Ni(1)Ta6V5Ni cuboctahedra, corners with two equivalent V(3)Ta6V4Ni2 cuboctahedra, corners with three equivalent V(2)Ta6V2Ni4 cuboctahedra, corners with three equivalent C(2)Ta6 octahedra,  a faceface with one Ni(1)Ta6V5Ni cuboctahedra, faces with two equivalent V(2)Ta6V2Ni4 cuboctahedra, faces with two equivalent V(3)Ta6V4Ni2 cuboctahedra,  a faceface with one C(2)Ta6 octahedra, and faces with two equivalent C(1)Ta6 octahedra. The corner-sharing octahedral tilt angles range from 44-46°. The Ni(1)-Ni(1) bond length is 2.52 Å. In the second Ni site, Ni(2) is bonded in a 12-coordinate geometry to one Ta(2), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), one V(1), two equivalent V(2), one Ni(2), and two equivalent Ni(3) atoms. The Ni(2)-Ni(2) bond length is 2.56 Å. Both Ni(2)-Ni(3) bond lengths are 2.57 Å. In the third Ni site, Ni(3) is bonded in a 12-coordinate geometry to one Ta(1), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one V(2), two equivalent V(1), one Ni(3), and two equivalent Ni(2) atoms. The Ni(3)-Ni(3) bond length is 2.59 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Ta(1), one Ta(4), two equivalent Ta(3), and two equivalent Ta(6) atoms to form CTa6 octahedra that share corners with three equivalent V(3)Ta6V4Ni2 cuboctahedra, corners with two equivalent C(1)Ta6 octahedra, corners with four equivalent C(2)Ta6 octahedra, edges with four equivalent V(2)Ta6V2Ni4 cuboctahedra,  a faceface with one V(3)Ta6V4Ni2 cuboctahedra, and faces with two equivalent Ni(1)Ta6V5Ni cuboctahedra. The corner-sharing octahedral tilt angles range from 38-42°. In the second C site, C(2) is bonded to one Ta(2), one Ta(5), two equivalent Ta(3), and two equivalent Ta(6) atoms to form CTa6 octahedra that share corners with three equivalent Ni(1)Ta6V5Ni cuboctahedra, corners with two equivalent C(2)Ta6 octahedra, corners with four equivalent C(1)Ta6 octahedra, edges with two equivalent V(2)Ta6V2Ni4 cuboctahedra,  a faceface with one Ni(1)Ta6V5Ni cuboctahedra, and faces with two equivalent V(3)Ta6V4Ni2 cuboctahedra. The corner-sharing octahedral tilt angles range from 37-42°.