Ta6Cr3Ni3C2 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 Cr(2), two equivalent Cr(3), two equivalent Ni(3), and two equivalent C(1) atoms. In the second Ta site, Ta(2) is bonded in a 2-coordinate geometry to two equivalent Cr(1), 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 2-coordinate geometry to one Cr(1), one Cr(2), one Cr(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 Cr(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 Cr(1), two equivalent Cr(3), two equivalent Ni(3), and two equivalent C(2) atoms. In the sixth Ta site, Ta(6) is bonded in a 2-coordinate geometry to one Cr(1), one Cr(2), one Cr(3), one Ni(1), one Ni(2), one Ni(3), one C(1), and one C(2) atom. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Ta(2), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one Cr(3), one Ni(2), two equivalent Ni(1), and two equivalent Ni(3) atoms to form distorted CrTa6CrNi5 cuboctahedra that share corners with three equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra, edges with two equivalent C(1)Ta6 octahedra, edges with four equivalent C(2)Ta6 octahedra, faces with two equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra, faces with two equivalent Cr(1)Ta6CrNi5 cuboctahedra, and faces with four equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra. In the second Cr site, Cr(2) is bonded to one Ta(1), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), two equivalent Cr(3), one Ni(1), one Ni(3), and two equivalent Ni(2) atoms to form distorted CrTa6Cr2Ni4 cuboctahedra that share edges with two equivalent C(2)Ta6 octahedra, edges with four equivalent C(1)Ta6 octahedra, faces with two equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, faces with two equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra, and faces with four equivalent Cr(1)Ta6CrNi5 cuboctahedra. In the third Cr site, Cr(3) is bonded to one Ta(1), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one Cr(1), one Cr(3), two equivalent Cr(2), and two equivalent Ni(1) atoms to form distorted CrTa6Cr4Ni2 cuboctahedra that share  a cornercorner with one Cr(3)Ta6Cr4Ni2 cuboctahedra, corners with three equivalent Cr(1)Ta6CrNi5 cuboctahedra, corners with three equivalent C(1)Ta6 octahedra,  a faceface with one Cr(3)Ta6Cr4Ni2 cuboctahedra, faces with two equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, faces with two equivalent Cr(1)Ta6CrNi5 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 43-44°. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 12-coordinate geometry to one Ta(2), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), one Cr(2), two equivalent Cr(1), two equivalent Cr(3), and one Ni(1) atom. 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 Cr(1), two equivalent Cr(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 Cr(2), two equivalent Cr(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 Cr(3)Ta6Cr4Ni2 cuboctahedra, corners with two equivalent C(1)Ta6 octahedra, corners with four equivalent C(2)Ta6 octahedra, edges with two equivalent Cr(1)Ta6CrNi5 cuboctahedra, edges with four equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, and  a faceface with one Cr(3)Ta6Cr4Ni2 cuboctahedra. The corner-sharing octahedral tilt angles range from 42-44°. 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 two equivalent C(2)Ta6 octahedra, corners with four equivalent C(1)Ta6 octahedra, edges with two equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, edges with four equivalent Cr(1)Ta6CrNi5 cuboctahedra, and faces with two equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra. The corner-sharing octahedral tilt angles range from 42-43°.
Ta6Cr3Ni3C2 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 Cr(2), two equivalent Cr(3), two equivalent Ni(3), and two equivalent C(1) atoms. Both Ta(1)-Cr(2) bond lengths are 2.84 Å. Both Ta(1)-Cr(3) bond lengths are 2.89 Å. Both Ta(1)-Ni(3) bond lengths are 2.75 Å. Both Ta(1)-C(1) bond lengths are 2.20 Å. In the second Ta site, Ta(2) is bonded in a 2-coordinate geometry to two equivalent Cr(1), two equivalent Ni(1), two equivalent Ni(2), and two equivalent C(2) atoms. Both Ta(2)-Cr(1) bond lengths are 2.91 Å. Both Ta(2)-Ni(1) bond lengths are 2.89 Å. Both Ta(2)-Ni(2) bond lengths are 2.78 Å. Both Ta(2)-C(2) bond lengths are 2.15 Å. In the third Ta site, Ta(3) is bonded in a 2-coordinate geometry to one Cr(1), one Cr(2), one Cr(3), one Ni(1), one Ni(2), one Ni(3), one C(1), and one C(2) atom. The Ta(3)-Cr(1) bond length is 2.88 Å. The Ta(3)-Cr(2) bond length is 2.91 Å. The Ta(3)-Cr(3) bond length is 2.88 Å. The Ta(3)-Ni(1) bond length is 2.90 Å. The Ta(3)-Ni(2) bond length is 2.77 Å. The Ta(3)-Ni(3) bond length is 2.77 Å. The Ta(3)-C(1) bond length is 2.17 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 Cr(2), two equivalent Ni(1), two equivalent Ni(2), and two equivalent C(1) atoms. Both Ta(4)-Cr(2) bond lengths are 2.92 Å. Both Ta(4)-Ni(1) bond lengths are 2.76 Å. Both Ta(4)-Ni(2) bond lengths are 2.92 Å. Both Ta(4)-C(1) bond lengths are 2.16 Å. In the fifth Ta site, Ta(5) is bonded in a distorted bent 150 degrees geometry to two equivalent Cr(1), two equivalent Cr(3), two equivalent Ni(3), and two equivalent C(2) atoms. Both Ta(5)-Cr(1) bond lengths are 2.90 Å. Both Ta(5)-Cr(3) bond lengths are 2.82 Å. Both Ta(5)-Ni(3) bond lengths are 2.89 Å. Both Ta(5)-C(2) bond lengths are 2.16 Å. In the sixth Ta site, Ta(6) is bonded in a 2-coordinate geometry to one Cr(1), one Cr(2), one Cr(3), one Ni(1), one Ni(2), one Ni(3), one C(1), and one C(2) atom. The Ta(6)-Cr(1) bond length is 2.89 Å. The Ta(6)-Cr(2) bond length is 2.91 Å. The Ta(6)-Cr(3) bond length is 2.81 Å. The Ta(6)-Ni(1) bond length is 2.77 Å. The Ta(6)-Ni(2) bond length is 2.89 Å. The Ta(6)-Ni(3) bond length is 2.91 Å. The Ta(6)-C(1) bond length is 2.16 Å. The Ta(6)-C(2) bond length is 2.17 Å. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Ta(2), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one Cr(3), one Ni(2), two equivalent Ni(1), and two equivalent Ni(3) atoms to form distorted CrTa6CrNi5 cuboctahedra that share corners with three equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra, edges with two equivalent C(1)Ta6 octahedra, edges with four equivalent C(2)Ta6 octahedra, faces with two equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra, faces with two equivalent Cr(1)Ta6CrNi5 cuboctahedra, and faces with four equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra. The Cr(1)-Cr(3) bond length is 2.45 Å. The Cr(1)-Ni(2) bond length is 2.43 Å. Both Cr(1)-Ni(1) bond lengths are 2.47 Å. Both Cr(1)-Ni(3) bond lengths are 2.43 Å. In the second Cr site, Cr(2) is bonded to one Ta(1), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), two equivalent Cr(3), one Ni(1), one Ni(3), and two equivalent Ni(2) atoms to form distorted CrTa6Cr2Ni4 cuboctahedra that share edges with two equivalent C(2)Ta6 octahedra, edges with four equivalent C(1)Ta6 octahedra, faces with two equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, faces with two equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra, and faces with four equivalent Cr(1)Ta6CrNi5 cuboctahedra. Both Cr(2)-Cr(3) bond lengths are 2.41 Å. The Cr(2)-Ni(1) bond length is 2.46 Å. The Cr(2)-Ni(3) bond length is 2.45 Å. Both Cr(2)-Ni(2) bond lengths are 2.46 Å. In the third Cr site, Cr(3) is bonded to one Ta(1), one Ta(5), two equivalent Ta(3), two equivalent Ta(6), one Cr(1), one Cr(3), two equivalent Cr(2), and two equivalent Ni(1) atoms to form distorted CrTa6Cr4Ni2 cuboctahedra that share  a cornercorner with one Cr(3)Ta6Cr4Ni2 cuboctahedra, corners with three equivalent Cr(1)Ta6CrNi5 cuboctahedra, corners with three equivalent C(1)Ta6 octahedra,  a faceface with one Cr(3)Ta6Cr4Ni2 cuboctahedra, faces with two equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, faces with two equivalent Cr(1)Ta6CrNi5 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 43-44°. The Cr(3)-Cr(3) bond length is 2.50 Å. Both Cr(3)-Ni(1) bond lengths are 2.52 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 12-coordinate geometry to one Ta(2), one Ta(4), two equivalent Ta(3), two equivalent Ta(6), one Cr(2), two equivalent Cr(1), two equivalent Cr(3), and one Ni(1) atom. The Ni(1)-Ni(1) bond length is 2.54 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 Cr(1), two equivalent Cr(2), one Ni(2), and two equivalent Ni(3) atoms. The Ni(2)-Ni(2) bond length is 2.58 Å. Both Ni(2)-Ni(3) bond lengths are 2.56 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 Cr(2), two equivalent Cr(1), one Ni(3), and two equivalent Ni(2) atoms. The Ni(3)-Ni(3) bond length is 2.55 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 Cr(3)Ta6Cr4Ni2 cuboctahedra, corners with two equivalent C(1)Ta6 octahedra, corners with four equivalent C(2)Ta6 octahedra, edges with two equivalent Cr(1)Ta6CrNi5 cuboctahedra, edges with four equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, and  a faceface with one Cr(3)Ta6Cr4Ni2 cuboctahedra. The corner-sharing octahedral tilt angles range from 42-44°. 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 two equivalent C(2)Ta6 octahedra, corners with four equivalent C(1)Ta6 octahedra, edges with two equivalent Cr(2)Ta6Cr2Ni4 cuboctahedra, edges with four equivalent Cr(1)Ta6CrNi5 cuboctahedra, and faces with two equivalent Cr(3)Ta6Cr4Ni2 cuboctahedra. The corner-sharing octahedral tilt angles range from 42-43°.