Pr2Co17 crystallizes in the trigonal R-3m space group. Pr(1) is bonded in a 19-coordinate geometry to one Co(4), three equivalent Co(1), six equivalent Co(2), and nine equivalent Co(3) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent Pr(1), two equivalent Co(4), four equivalent Co(2), and four equivalent Co(3) atoms to form CoPr2Co10 cuboctahedra that share corners with four equivalent Co(1)Pr2Co10 cuboctahedra, corners with eight equivalent Co(2)Pr2Co10 cuboctahedra, corners with ten equivalent Co(3)Pr3Co9 cuboctahedra, edges with four equivalent Co(2)Pr2Co10 cuboctahedra, edges with six equivalent Co(3)Pr3Co9 cuboctahedra, faces with four equivalent Co(1)Pr2Co10 cuboctahedra, faces with six equivalent Co(3)Pr3Co9 cuboctahedra, and faces with eight equivalent Co(2)Pr2Co10 cuboctahedra. In the second Co site, Co(2) is bonded to two equivalent Pr(1), two equivalent Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form distorted CoPr2Co10 cuboctahedra that share corners with four equivalent Co(1)Pr2Co10 cuboctahedra, corners with eight equivalent Co(3)Pr3Co9 cuboctahedra, corners with twelve equivalent Co(2)Pr2Co10 cuboctahedra,  an edgeedge with one Co(2)Pr2Co10 cuboctahedra, edges with two equivalent Co(1)Pr2Co10 cuboctahedra, edges with two equivalent Co(3)Pr3Co9 cuboctahedra, faces with four equivalent Co(1)Pr2Co10 cuboctahedra, faces with seven equivalent Co(2)Pr2Co10 cuboctahedra, and faces with ten equivalent Co(3)Pr3Co9 cuboctahedra. In the third Co site, Co(3) is bonded to three equivalent Pr(1), one Co(4), two equivalent Co(1), two equivalent Co(3), and four equivalent Co(2) atoms to form CoPr3Co9 cuboctahedra that share corners with five equivalent Co(1)Pr2Co10 cuboctahedra, corners with eight equivalent Co(2)Pr2Co10 cuboctahedra, corners with ten equivalent Co(3)Pr3Co9 cuboctahedra, edges with two equivalent Co(2)Pr2Co10 cuboctahedra, edges with three equivalent Co(1)Pr2Co10 cuboctahedra, edges with five equivalent Co(3)Pr3Co9 cuboctahedra, faces with three equivalent Co(1)Pr2Co10 cuboctahedra, faces with seven equivalent Co(3)Pr3Co9 cuboctahedra, and faces with ten equivalent Co(2)Pr2Co10 cuboctahedra. In the fourth Co site, Co(4) is bonded in a 14-coordinate geometry to one Pr(1), one Co(4), three equivalent Co(1), three equivalent Co(3), and six equivalent Co(2) atoms.
Pr2Co17 crystallizes in the trigonal R-3m space group. Pr(1) is bonded in a 19-coordinate geometry to one Co(4), three equivalent Co(1), six equivalent Co(2), and nine equivalent Co(3) atoms. The Pr(1)-Co(4) bond length is 3.05 Å. All Pr(1)-Co(1) bond lengths are 3.24 Å. All Pr(1)-Co(2) bond lengths are 3.02 Å. There are a spread of Pr(1)-Co(3) bond distances ranging from 3.06-3.17 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent Pr(1), two equivalent Co(4), four equivalent Co(2), and four equivalent Co(3) atoms to form CoPr2Co10 cuboctahedra that share corners with four equivalent Co(1)Pr2Co10 cuboctahedra, corners with eight equivalent Co(2)Pr2Co10 cuboctahedra, corners with ten equivalent Co(3)Pr3Co9 cuboctahedra, edges with four equivalent Co(2)Pr2Co10 cuboctahedra, edges with six equivalent Co(3)Pr3Co9 cuboctahedra, faces with four equivalent Co(1)Pr2Co10 cuboctahedra, faces with six equivalent Co(3)Pr3Co9 cuboctahedra, and faces with eight equivalent Co(2)Pr2Co10 cuboctahedra. Both Co(1)-Co(4) bond lengths are 2.58 Å. All Co(1)-Co(2) bond lengths are 2.38 Å. All Co(1)-Co(3) bond lengths are 2.40 Å. In the second Co site, Co(2) is bonded to two equivalent Pr(1), two equivalent Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form distorted CoPr2Co10 cuboctahedra that share corners with four equivalent Co(1)Pr2Co10 cuboctahedra, corners with eight equivalent Co(3)Pr3Co9 cuboctahedra, corners with twelve equivalent Co(2)Pr2Co10 cuboctahedra,  an edgeedge with one Co(2)Pr2Co10 cuboctahedra, edges with two equivalent Co(1)Pr2Co10 cuboctahedra, edges with two equivalent Co(3)Pr3Co9 cuboctahedra, faces with four equivalent Co(1)Pr2Co10 cuboctahedra, faces with seven equivalent Co(2)Pr2Co10 cuboctahedra, and faces with ten equivalent Co(3)Pr3Co9 cuboctahedra. Both Co(2)-Co(2) bond lengths are 2.38 Å. Both Co(2)-Co(4) bond lengths are 2.64 Å. There are two shorter (2.46 Å) and two longer (2.65 Å) Co(2)-Co(3) bond lengths. In the third Co site, Co(3) is bonded to three equivalent Pr(1), one Co(4), two equivalent Co(1), two equivalent Co(3), and four equivalent Co(2) atoms to form CoPr3Co9 cuboctahedra that share corners with five equivalent Co(1)Pr2Co10 cuboctahedra, corners with eight equivalent Co(2)Pr2Co10 cuboctahedra, corners with ten equivalent Co(3)Pr3Co9 cuboctahedra, edges with two equivalent Co(2)Pr2Co10 cuboctahedra, edges with three equivalent Co(1)Pr2Co10 cuboctahedra, edges with five equivalent Co(3)Pr3Co9 cuboctahedra, faces with three equivalent Co(1)Pr2Co10 cuboctahedra, faces with seven equivalent Co(3)Pr3Co9 cuboctahedra, and faces with ten equivalent Co(2)Pr2Co10 cuboctahedra. The Co(3)-Co(4) bond length is 2.57 Å. Both Co(3)-Co(3) bond lengths are 2.47 Å. In the fourth Co site, Co(4) is bonded in a 14-coordinate geometry to one Pr(1), one Co(4), three equivalent Co(1), three equivalent Co(3), and six equivalent Co(2) atoms. The Co(4)-Co(4) bond length is 2.28 Å.