Pr2Fe20Si2C crystallizes in the triclinic P-1 space group. Pr(1) is bonded in a distorted single-bond geometry to one Fe(10), one Fe(11), two equivalent Fe(3), two equivalent Fe(4), two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), two equivalent Fe(9), and one C(1) atom. There are eleven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a single-bond geometry to one Fe(10), one Fe(11), one Fe(3), one Fe(4), one Fe(5), one Fe(7), one Fe(8), one Fe(9), and one C(1) atom. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Fe(10), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), one Fe(9), one Si(1), and one C(1) atom. In the third Fe site, Fe(3) is bonded to two equivalent Pr(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(4), one Fe(5), one Fe(6), one Fe(9), and two equivalent Fe(7) atoms to form distorted FePr2Fe10 cuboctahedra that share  a cornercorner with one Fe(10)Pr2Fe10 cuboctahedra, corners with two equivalent Fe(3)Pr2Fe10 cuboctahedra, corners with two equivalent C(1)Pr2Fe4 octahedra,  an edgeedge with one Fe(11)Pr2Fe10 cuboctahedra,  an edgeedge with one C(1)Pr2Fe4 octahedra,  a faceface with one Fe(10)Pr2Fe10 cuboctahedra,  a faceface with one Fe(11)Pr2Fe10 cuboctahedra, and  a faceface with one Fe(3)Pr2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles range from 27-71°. In the fourth Fe site, Fe(4) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(10), one Fe(2), one Fe(3), one Fe(5), one Fe(6), one Fe(9), two equivalent Fe(8), and one Si(1) atom. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(11), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(6), and one Si(2) atom. In the sixth Fe site, Fe(6) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(2), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(5), one Si(1), and one Si(2) atom. In the seventh Fe site, Fe(7) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(11), one Fe(2), one Fe(5), one Fe(6), one Fe(8), one Fe(9), two equivalent Fe(3), and one Si(2) atom. In the eighth Fe site, Fe(8) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(2), one Fe(5), one Fe(6), one Fe(7), one Fe(9), two equivalent Fe(4), one Si(1), and one Si(2) atom. In the ninth Fe site, Fe(9) is bonded in a 14-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(3), one Fe(4), one Fe(5), one Fe(6), one Fe(7), one Fe(8), one Si(1), and one Si(2) atom. In the tenth Fe site, Fe(10) is bonded to two equivalent Pr(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and two equivalent Fe(9) atoms to form distorted FePr2Fe10 cuboctahedra that share corners with two equivalent Fe(11)Pr2Fe10 cuboctahedra, corners with two equivalent Fe(3)Pr2Fe10 cuboctahedra, faces with two equivalent Fe(11)Pr2Fe10 cuboctahedra, faces with two equivalent Fe(3)Pr2Fe10 cuboctahedra, and faces with two equivalent C(1)Pr2Fe4 octahedra. In the eleventh Fe site, Fe(11) is bonded to two equivalent Pr(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Fe(9) atoms to form distorted FePr2Fe10 cuboctahedra that share corners with two equivalent Fe(10)Pr2Fe10 cuboctahedra, edges with two equivalent Fe(3)Pr2Fe10 cuboctahedra, edges with two equivalent C(1)Pr2Fe4 octahedra, faces with two equivalent Fe(10)Pr2Fe10 cuboctahedra, and faces with two equivalent Fe(3)Pr2Fe10 cuboctahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to two equivalent Fe(2), two equivalent Fe(4), two equivalent Fe(6), two equivalent Fe(8), and two equivalent Fe(9) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), and two equivalent Fe(9) atoms. C(1) is bonded to two equivalent Pr(1), two equivalent Fe(1), and two equivalent Fe(2) atoms to form CPr2Fe4 octahedra that share corners with four equivalent Fe(3)Pr2Fe10 cuboctahedra, edges with two equivalent Fe(11)Pr2Fe10 cuboctahedra, edges with two equivalent Fe(3)Pr2Fe10 cuboctahedra, and faces with two equivalent Fe(10)Pr2Fe10 cuboctahedra.
Pr2Fe20Si2C crystallizes in the triclinic P-1 space group. Pr(1) is bonded in a distorted single-bond geometry to one Fe(10), one Fe(11), two equivalent Fe(3), two equivalent Fe(4), two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), two equivalent Fe(9), and one C(1) atom. The Pr(1)-Fe(10) bond length is 3.48 Å. The Pr(1)-Fe(11) bond length is 3.49 Å. There is one shorter (3.15 Å) and one longer (3.24 Å) Pr(1)-Fe(3) bond length. There is one shorter (3.16 Å) and one longer (3.26 Å) Pr(1)-Fe(4) bond length. There is one shorter (3.11 Å) and one longer (3.21 Å) Pr(1)-Fe(5) bond length. There is one shorter (3.15 Å) and one longer (3.22 Å) Pr(1)-Fe(6) bond length. There is one shorter (3.12 Å) and one longer (3.33 Å) Pr(1)-Fe(7) bond length. There is one shorter (3.13 Å) and one longer (3.34 Å) Pr(1)-Fe(8) bond length. There is one shorter (3.17 Å) and one longer (3.23 Å) Pr(1)-Fe(9) bond length. The Pr(1)-C(1) bond length is 2.66 Å. There are eleven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a single-bond geometry to one Fe(10), one Fe(11), one Fe(3), one Fe(4), one Fe(5), one Fe(7), one Fe(8), one Fe(9), and one C(1) atom. The Fe(1)-Fe(10) bond length is 2.41 Å. The Fe(1)-Fe(11) bond length is 2.41 Å. The Fe(1)-Fe(3) bond length is 2.62 Å. The Fe(1)-Fe(4) bond length is 2.44 Å. The Fe(1)-Fe(5) bond length is 2.63 Å. The Fe(1)-Fe(7) bond length is 2.49 Å. The Fe(1)-Fe(8) bond length is 2.57 Å. The Fe(1)-Fe(9) bond length is 2.72 Å. The Fe(1)-C(1) bond length is 1.86 Å. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Fe(10), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), one Fe(9), one Si(1), and one C(1) atom. The Fe(2)-Fe(10) bond length is 2.40 Å. The Fe(2)-Fe(3) bond length is 2.46 Å. The Fe(2)-Fe(4) bond length is 2.62 Å. The Fe(2)-Fe(6) bond length is 2.61 Å. The Fe(2)-Fe(7) bond length is 2.59 Å. The Fe(2)-Fe(8) bond length is 2.48 Å. The Fe(2)-Fe(9) bond length is 2.69 Å. The Fe(2)-Si(1) bond length is 2.40 Å. The Fe(2)-C(1) bond length is 1.87 Å. In the third Fe site, Fe(3) is bonded to two equivalent Pr(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(4), one Fe(5), one Fe(6), one Fe(9), and two equivalent Fe(7) atoms to form distorted FePr2Fe10 cuboctahedra that share  a cornercorner with one Fe(10)Pr2Fe10 cuboctahedra, corners with two equivalent Fe(3)Pr2Fe10 cuboctahedra, corners with two equivalent C(1)Pr2Fe4 octahedra,  an edgeedge with one Fe(11)Pr2Fe10 cuboctahedra,  an edgeedge with one C(1)Pr2Fe4 octahedra,  a faceface with one Fe(10)Pr2Fe10 cuboctahedra,  a faceface with one Fe(11)Pr2Fe10 cuboctahedra, and  a faceface with one Fe(3)Pr2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles range from 27-71°. The Fe(3)-Fe(10) bond length is 2.47 Å. The Fe(3)-Fe(11) bond length is 2.41 Å. The Fe(3)-Fe(4) bond length is 2.64 Å. The Fe(3)-Fe(5) bond length is 2.51 Å. The Fe(3)-Fe(6) bond length is 2.55 Å. The Fe(3)-Fe(9) bond length is 2.72 Å. There is one shorter (2.52 Å) and one longer (2.60 Å) Fe(3)-Fe(7) bond length. In the fourth Fe site, Fe(4) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(10), one Fe(2), one Fe(3), one Fe(5), one Fe(6), one Fe(9), two equivalent Fe(8), and one Si(1) atom. The Fe(4)-Fe(10) bond length is 2.49 Å. The Fe(4)-Fe(5) bond length is 2.54 Å. The Fe(4)-Fe(6) bond length is 2.47 Å. The Fe(4)-Fe(9) bond length is 2.73 Å. There is one shorter (2.52 Å) and one longer (2.59 Å) Fe(4)-Fe(8) bond length. The Fe(4)-Si(1) bond length is 2.40 Å. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(11), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(6), and one Si(2) atom. The Fe(5)-Fe(11) bond length is 2.47 Å. The Fe(5)-Fe(7) bond length is 2.62 Å. The Fe(5)-Fe(8) bond length is 2.48 Å. The Fe(5)-Fe(9) bond length is 2.69 Å. There is one shorter (2.53 Å) and one longer (2.56 Å) Fe(5)-Fe(6) bond length. The Fe(5)-Si(2) bond length is 2.42 Å. In the sixth Fe site, Fe(6) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(2), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(5), one Si(1), and one Si(2) atom. The Fe(6)-Fe(7) bond length is 2.47 Å. The Fe(6)-Fe(8) bond length is 2.62 Å. The Fe(6)-Fe(9) bond length is 2.69 Å. The Fe(6)-Si(1) bond length is 2.44 Å. The Fe(6)-Si(2) bond length is 2.41 Å. In the seventh Fe site, Fe(7) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(11), one Fe(2), one Fe(5), one Fe(6), one Fe(8), one Fe(9), two equivalent Fe(3), and one Si(2) atom. The Fe(7)-Fe(11) bond length is 2.40 Å. The Fe(7)-Fe(8) bond length is 2.58 Å. The Fe(7)-Fe(9) bond length is 2.65 Å. The Fe(7)-Si(2) bond length is 2.41 Å. In the eighth Fe site, Fe(8) is bonded in a 12-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(2), one Fe(5), one Fe(6), one Fe(7), one Fe(9), two equivalent Fe(4), one Si(1), and one Si(2) atom. The Fe(8)-Fe(9) bond length is 2.68 Å. The Fe(8)-Si(1) bond length is 2.40 Å. The Fe(8)-Si(2) bond length is 2.43 Å. In the ninth Fe site, Fe(9) is bonded in a 14-coordinate geometry to two equivalent Pr(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(3), one Fe(4), one Fe(5), one Fe(6), one Fe(7), one Fe(8), one Si(1), and one Si(2) atom. The Fe(9)-Fe(10) bond length is 2.64 Å. The Fe(9)-Fe(11) bond length is 2.68 Å. The Fe(9)-Si(1) bond length is 2.66 Å. The Fe(9)-Si(2) bond length is 2.61 Å. In the tenth Fe site, Fe(10) is bonded to two equivalent Pr(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and two equivalent Fe(9) atoms to form distorted FePr2Fe10 cuboctahedra that share corners with two equivalent Fe(11)Pr2Fe10 cuboctahedra, corners with two equivalent Fe(3)Pr2Fe10 cuboctahedra, faces with two equivalent Fe(11)Pr2Fe10 cuboctahedra, faces with two equivalent Fe(3)Pr2Fe10 cuboctahedra, and faces with two equivalent C(1)Pr2Fe4 octahedra. In the eleventh Fe site, Fe(11) is bonded to two equivalent Pr(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Fe(9) atoms to form distorted FePr2Fe10 cuboctahedra that share corners with two equivalent Fe(10)Pr2Fe10 cuboctahedra, edges with two equivalent Fe(3)Pr2Fe10 cuboctahedra, edges with two equivalent C(1)Pr2Fe4 octahedra, faces with two equivalent Fe(10)Pr2Fe10 cuboctahedra, and faces with two equivalent Fe(3)Pr2Fe10 cuboctahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to two equivalent Fe(2), two equivalent Fe(4), two equivalent Fe(6), two equivalent Fe(8), and two equivalent Fe(9) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), and two equivalent Fe(9) atoms. C(1) is bonded to two equivalent Pr(1), two equivalent Fe(1), and two equivalent Fe(2) atoms to form CPr2Fe4 octahedra that share corners with four equivalent Fe(3)Pr2Fe10 cuboctahedra, edges with two equivalent Fe(11)Pr2Fe10 cuboctahedra, edges with two equivalent Fe(3)Pr2Fe10 cuboctahedra, and faces with two equivalent Fe(10)Pr2Fe10 cuboctahedra.