Dy2Fe17C crystallizes in the monoclinic C2/m space group. Dy(1) is bonded in a distorted single-bond geometry to one Fe(1), one Fe(6), two equivalent Fe(7), four equivalent Fe(5), six equivalent Fe(3), and one C(1) atom. There are seven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 14-coordinate geometry to one Dy(1), one Fe(1), one Fe(2), one Fe(6), two equivalent Fe(3), two equivalent Fe(4), two equivalent Fe(7), and four equivalent Fe(5) atoms. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and one C(1) atom. In the third Fe site, Fe(3) is bonded to three equivalent Dy(1), one Fe(1), one Fe(2), one Fe(3), one Fe(4), one Fe(6), one Fe(7), and three equivalent Fe(5) atoms to form FeDy3Fe9 cuboctahedra that share  a cornercorner with one Fe(6)Dy2Fe10 cuboctahedra, corners with four equivalent Fe(7)Dy2Fe10 cuboctahedra, corners with seven equivalent Fe(3)Dy3Fe9 cuboctahedra, corners with two equivalent C(1)Dy2Fe4 octahedra,  an edgeedge with one Fe(6)Dy2Fe10 cuboctahedra, edges with two equivalent Fe(7)Dy2Fe10 cuboctahedra, edges with three equivalent Fe(3)Dy3Fe9 cuboctahedra,  a faceface with one Fe(6)Dy2Fe10 cuboctahedra, faces with two equivalent Fe(7)Dy2Fe10 cuboctahedra, faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra, and  a faceface with one C(1)Dy2Fe4 octahedra. The corner-sharing octahedral tilt angles range from 65-70°. In the fourth Fe site, Fe(4) is bonded in a single-bond geometry to two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and one C(1) atom. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to two equivalent Dy(1), one Fe(2), one Fe(4), one Fe(5), one Fe(6), one Fe(7), two equivalent Fe(1), and three equivalent Fe(3) atoms. In the sixth Fe site, Fe(6) is bonded to two equivalent Dy(1), two equivalent Fe(1), four equivalent Fe(3), and four equivalent Fe(5) atoms to form FeDy2Fe10 cuboctahedra that share corners with four equivalent Fe(7)Dy2Fe10 cuboctahedra, corners with four equivalent Fe(3)Dy3Fe9 cuboctahedra, corners with two equivalent C(1)Dy2Fe4 octahedra, edges with four equivalent Fe(3)Dy3Fe9 cuboctahedra, faces with four equivalent Fe(7)Dy2Fe10 cuboctahedra, and faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. In the seventh Fe site, Fe(7) is bonded to two equivalent Dy(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and two equivalent Fe(5) atoms to form distorted FeDy2Fe10 cuboctahedra that share corners with two equivalent Fe(6)Dy2Fe10 cuboctahedra, corners with two equivalent Fe(7)Dy2Fe10 cuboctahedra, corners with eight equivalent Fe(3)Dy3Fe9 cuboctahedra, edges with four equivalent Fe(3)Dy3Fe9 cuboctahedra, faces with two equivalent Fe(6)Dy2Fe10 cuboctahedra, faces with two equivalent Fe(7)Dy2Fe10 cuboctahedra, faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra, and faces with two equivalent C(1)Dy2Fe4 octahedra. C(1) is bonded to two equivalent Dy(1), two equivalent Fe(2), and two equivalent Fe(4) atoms to form CDy2Fe4 octahedra that share corners with two equivalent Fe(6)Dy2Fe10 cuboctahedra, corners with eight equivalent Fe(3)Dy3Fe9 cuboctahedra, faces with four equivalent Fe(7)Dy2Fe10 cuboctahedra, and faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra.
Dy2Fe17C crystallizes in the monoclinic C2/m space group. Dy(1) is bonded in a distorted single-bond geometry to one Fe(1), one Fe(6), two equivalent Fe(7), four equivalent Fe(5), six equivalent Fe(3), and one C(1) atom. The Dy(1)-Fe(1) bond length is 3.03 Å. The Dy(1)-Fe(6) bond length is 3.26 Å. Both Dy(1)-Fe(7) bond lengths are 3.31 Å. There are two shorter (3.02 Å) and two longer (3.07 Å) Dy(1)-Fe(5) bond lengths. There are a spread of Dy(1)-Fe(3) bond distances ranging from 3.06-3.28 Å. The Dy(1)-C(1) bond length is 2.50 Å. There are seven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 14-coordinate geometry to one Dy(1), one Fe(1), one Fe(2), one Fe(6), two equivalent Fe(3), two equivalent Fe(4), two equivalent Fe(7), and four equivalent Fe(5) atoms. The Fe(1)-Fe(1) bond length is 2.40 Å. The Fe(1)-Fe(2) bond length is 2.64 Å. The Fe(1)-Fe(6) bond length is 2.61 Å. Both Fe(1)-Fe(3) bond lengths are 2.65 Å. Both Fe(1)-Fe(4) bond lengths are 2.73 Å. Both Fe(1)-Fe(7) bond lengths are 2.62 Å. All Fe(1)-Fe(5) bond lengths are 2.75 Å. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and one C(1) atom. Both Fe(2)-Fe(3) bond lengths are 2.52 Å. Both Fe(2)-Fe(5) bond lengths are 2.55 Å. Both Fe(2)-Fe(7) bond lengths are 2.47 Å. The Fe(2)-C(1) bond length is 1.91 Å. In the third Fe site, Fe(3) is bonded to three equivalent Dy(1), one Fe(1), one Fe(2), one Fe(3), one Fe(4), one Fe(6), one Fe(7), and three equivalent Fe(5) atoms to form FeDy3Fe9 cuboctahedra that share  a cornercorner with one Fe(6)Dy2Fe10 cuboctahedra, corners with four equivalent Fe(7)Dy2Fe10 cuboctahedra, corners with seven equivalent Fe(3)Dy3Fe9 cuboctahedra, corners with two equivalent C(1)Dy2Fe4 octahedra,  an edgeedge with one Fe(6)Dy2Fe10 cuboctahedra, edges with two equivalent Fe(7)Dy2Fe10 cuboctahedra, edges with three equivalent Fe(3)Dy3Fe9 cuboctahedra,  a faceface with one Fe(6)Dy2Fe10 cuboctahedra, faces with two equivalent Fe(7)Dy2Fe10 cuboctahedra, faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra, and  a faceface with one C(1)Dy2Fe4 octahedra. The corner-sharing octahedral tilt angles range from 65-70°. The Fe(3)-Fe(3) bond length is 2.50 Å. The Fe(3)-Fe(4) bond length is 2.54 Å. The Fe(3)-Fe(6) bond length is 2.46 Å. The Fe(3)-Fe(7) bond length is 2.46 Å. There are a spread of Fe(3)-Fe(5) bond distances ranging from 2.55-2.63 Å. In the fourth Fe site, Fe(4) is bonded in a single-bond geometry to two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and one C(1) atom. Both Fe(4)-Fe(5) bond lengths are 2.46 Å. Both Fe(4)-Fe(7) bond lengths are 2.42 Å. The Fe(4)-C(1) bond length is 1.84 Å. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to two equivalent Dy(1), one Fe(2), one Fe(4), one Fe(5), one Fe(6), one Fe(7), two equivalent Fe(1), and three equivalent Fe(3) atoms. The Fe(5)-Fe(5) bond length is 2.49 Å. The Fe(5)-Fe(6) bond length is 2.42 Å. The Fe(5)-Fe(7) bond length is 2.43 Å. In the sixth Fe site, Fe(6) is bonded to two equivalent Dy(1), two equivalent Fe(1), four equivalent Fe(3), and four equivalent Fe(5) atoms to form FeDy2Fe10 cuboctahedra that share corners with four equivalent Fe(7)Dy2Fe10 cuboctahedra, corners with four equivalent Fe(3)Dy3Fe9 cuboctahedra, corners with two equivalent C(1)Dy2Fe4 octahedra, edges with four equivalent Fe(3)Dy3Fe9 cuboctahedra, faces with four equivalent Fe(7)Dy2Fe10 cuboctahedra, and faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. In the seventh Fe site, Fe(7) is bonded to two equivalent Dy(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and two equivalent Fe(5) atoms to form distorted FeDy2Fe10 cuboctahedra that share corners with two equivalent Fe(6)Dy2Fe10 cuboctahedra, corners with two equivalent Fe(7)Dy2Fe10 cuboctahedra, corners with eight equivalent Fe(3)Dy3Fe9 cuboctahedra, edges with four equivalent Fe(3)Dy3Fe9 cuboctahedra, faces with two equivalent Fe(6)Dy2Fe10 cuboctahedra, faces with two equivalent Fe(7)Dy2Fe10 cuboctahedra, faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra, and faces with two equivalent C(1)Dy2Fe4 octahedra. C(1) is bonded to two equivalent Dy(1), two equivalent Fe(2), and two equivalent Fe(4) atoms to form CDy2Fe4 octahedra that share corners with two equivalent Fe(6)Dy2Fe10 cuboctahedra, corners with eight equivalent Fe(3)Dy3Fe9 cuboctahedra, faces with four equivalent Fe(7)Dy2Fe10 cuboctahedra, and faces with four equivalent Fe(3)Dy3Fe9 cuboctahedra.