Th2Co17 crystallizes in the trigonal R-3m space group. Th(1) is bonded in a 19-coordinate geometry to one Co(2), three equivalent Co(3), six equivalent Co(4), and nine equivalent Co(1) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to three equivalent Th(1), one Co(2), two equivalent Co(1), two equivalent Co(3), and four equivalent Co(4) atoms to form CoTh3Co9 cuboctahedra that share corners with five equivalent Co(3)Th2Co10 cuboctahedra, corners with ten equivalent Co(1)Th3Co9 cuboctahedra, edges with three equivalent Co(3)Th2Co10 cuboctahedra, edges with five equivalent Co(1)Th3Co9 cuboctahedra, faces with three equivalent Co(3)Th2Co10 cuboctahedra, and faces with seven equivalent Co(1)Th3Co9 cuboctahedra. In the second Co site, Co(2) is bonded in a 14-coordinate geometry to one Th(1), one Co(2), three equivalent Co(1), three equivalent Co(3), and six equivalent Co(4) atoms. In the third Co site, Co(3) is bonded to two equivalent Th(1), two equivalent Co(2), four equivalent Co(1), and four equivalent Co(4) atoms to form distorted CoTh2Co10 cuboctahedra that share corners with four equivalent Co(3)Th2Co10 cuboctahedra, corners with ten equivalent Co(1)Th3Co9 cuboctahedra, edges with six equivalent Co(1)Th3Co9 cuboctahedra, faces with four equivalent Co(3)Th2Co10 cuboctahedra, and faces with six equivalent Co(1)Th3Co9 cuboctahedra. In the fourth Co site, Co(4) is bonded in a 12-coordinate geometry to two equivalent Th(1), two equivalent Co(2), two equivalent Co(3), two equivalent Co(4), and four equivalent Co(1) atoms.
Th2Co17 crystallizes in the trigonal R-3m space group. Th(1) is bonded in a 19-coordinate geometry to one Co(2), three equivalent Co(3), six equivalent Co(4), and nine equivalent Co(1) atoms. The Th(1)-Co(2) bond length is 3.02 Å. All Th(1)-Co(3) bond lengths are 3.23 Å. All Th(1)-Co(4) bond lengths are 3.02 Å. There are a spread of Th(1)-Co(1) bond distances ranging from 2.99-3.19 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to three equivalent Th(1), one Co(2), two equivalent Co(1), two equivalent Co(3), and four equivalent Co(4) atoms to form CoTh3Co9 cuboctahedra that share corners with five equivalent Co(3)Th2Co10 cuboctahedra, corners with ten equivalent Co(1)Th3Co9 cuboctahedra, edges with three equivalent Co(3)Th2Co10 cuboctahedra, edges with five equivalent Co(1)Th3Co9 cuboctahedra, faces with three equivalent Co(3)Th2Co10 cuboctahedra, and faces with seven equivalent Co(1)Th3Co9 cuboctahedra. The Co(1)-Co(2) bond length is 2.58 Å. Both Co(1)-Co(1) bond lengths are 2.46 Å. Both Co(1)-Co(3) bond lengths are 2.39 Å. There are two shorter (2.50 Å) and two longer (2.61 Å) Co(1)-Co(4) bond lengths. In the second Co site, Co(2) is bonded in a 14-coordinate geometry to one Th(1), one Co(2), three equivalent Co(1), three equivalent Co(3), and six equivalent Co(4) atoms. The Co(2)-Co(2) bond length is 2.32 Å. All Co(2)-Co(3) bond lengths are 2.56 Å. All Co(2)-Co(4) bond lengths are 2.61 Å. In the third Co site, Co(3) is bonded to two equivalent Th(1), two equivalent Co(2), four equivalent Co(1), and four equivalent Co(4) atoms to form distorted CoTh2Co10 cuboctahedra that share corners with four equivalent Co(3)Th2Co10 cuboctahedra, corners with ten equivalent Co(1)Th3Co9 cuboctahedra, edges with six equivalent Co(1)Th3Co9 cuboctahedra, faces with four equivalent Co(3)Th2Co10 cuboctahedra, and faces with six equivalent Co(1)Th3Co9 cuboctahedra. All Co(3)-Co(4) bond lengths are 2.37 Å. In the fourth Co site, Co(4) is bonded in a 12-coordinate geometry to two equivalent Th(1), two equivalent Co(2), two equivalent Co(3), two equivalent Co(4), and four equivalent Co(1) atoms. Both Co(4)-Co(4) bond lengths are 2.34 Å.