Sm2Mn17C2 crystallizes in the monoclinic C2/m space group. Sm(1) is bonded in a distorted bent 120 degrees geometry to one Mn(1), one Mn(6), two equivalent Mn(2), two equivalent Mn(7), three equivalent Mn(5), and two equivalent C(1) atoms. There are seven inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 14-coordinate geometry to one Sm(1), one Mn(1), one Mn(5), one Mn(6), two equivalent Mn(2), two equivalent Mn(4), two equivalent Mn(7), and four equivalent Mn(3) atoms. In the second Mn site, Mn(2) is bonded to two equivalent Sm(1), two equivalent Mn(1), two equivalent Mn(3), two equivalent Mn(4), two equivalent Mn(5), and two equivalent Mn(7) atoms to form distorted MnSm2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Sm2Mn10 cuboctahedra, corners with two equivalent Mn(7)Sm2Mn10 cuboctahedra, corners with four equivalent C(1)Sm2Mn4 octahedra,  an edgeedge with one Mn(2)Sm2Mn10 cuboctahedra, edges with two equivalent Mn(7)Sm2Mn10 cuboctahedra, edges with two equivalent C(1)Sm2Mn4 octahedra,  a faceface with one Mn(2)Sm2Mn10 cuboctahedra, and faces with two equivalent Mn(7)Sm2Mn10 cuboctahedra. The corner-sharing octahedral tilt angles range from 22-28°. In the third Mn site, Mn(3) is bonded in a single-bond geometry to one Mn(2), one Mn(5), one Mn(6), one Mn(7), two equivalent Mn(1), and one C(1) atom. In the fourth Mn site, Mn(4) is bonded in a single-bond geometry to one Mn(1), one Mn(2), one Mn(5), one Mn(6), one Mn(7), and one C(1) atom. In the fifth Mn site, Mn(5) is bonded in a 12-coordinate geometry to three equivalent Sm(1), one Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(4), and two equivalent Mn(7) atoms. In the sixth Mn site, Mn(6) is bonded in a 12-coordinate geometry to two equivalent Sm(1), two equivalent Mn(1), four equivalent Mn(3), and four equivalent Mn(4) atoms. In the seventh Mn site, Mn(7) is bonded to two equivalent Sm(1), two equivalent Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(4), and two equivalent Mn(5) atoms to form distorted MnSm2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Sm2Mn10 cuboctahedra, corners with two equivalent Mn(7)Sm2Mn10 cuboctahedra, corners with two equivalent C(1)Sm2Mn4 octahedra, edges with two equivalent Mn(2)Sm2Mn10 cuboctahedra, faces with two equivalent Mn(2)Sm2Mn10 cuboctahedra, faces with two equivalent Mn(7)Sm2Mn10 cuboctahedra, and faces with two equivalent C(1)Sm2Mn4 octahedra. The corner-sharing octahedral tilt angles are 48°. C(1) is bonded to two equivalent Sm(1), two equivalent Mn(3), and two equivalent Mn(4) atoms to form CSm2Mn4 octahedra that share corners with two equivalent Mn(7)Sm2Mn10 cuboctahedra, corners with four equivalent Mn(2)Sm2Mn10 cuboctahedra, corners with two equivalent C(1)Sm2Mn4 octahedra, edges with two equivalent Mn(2)Sm2Mn10 cuboctahedra, and faces with two equivalent Mn(7)Sm2Mn10 cuboctahedra. The corner-sharing octahedral tilt angles are 63°.
Sm2Mn17C2 crystallizes in the monoclinic C2/m space group. Sm(1) is bonded in a distorted bent 120 degrees geometry to one Mn(1), one Mn(6), two equivalent Mn(2), two equivalent Mn(7), three equivalent Mn(5), and two equivalent C(1) atoms. The Sm(1)-Mn(1) bond length is 3.18 Å. The Sm(1)-Mn(6) bond length is 3.42 Å. Both Sm(1)-Mn(2) bond lengths are 3.15 Å. Both Sm(1)-Mn(7) bond lengths are 3.37 Å. There are a spread of Sm(1)-Mn(5) bond distances ranging from 3.00-3.39 Å. Both Sm(1)-C(1) bond lengths are 2.53 Å. There are seven inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 14-coordinate geometry to one Sm(1), one Mn(1), one Mn(5), one Mn(6), two equivalent Mn(2), two equivalent Mn(4), two equivalent Mn(7), and four equivalent Mn(3) atoms. The Mn(1)-Mn(1) bond length is 2.34 Å. The Mn(1)-Mn(5) bond length is 2.62 Å. The Mn(1)-Mn(6) bond length is 2.65 Å. Both Mn(1)-Mn(2) bond lengths are 2.61 Å. Both Mn(1)-Mn(4) bond lengths are 2.57 Å. Both Mn(1)-Mn(7) bond lengths are 2.64 Å. There are two shorter (2.68 Å) and two longer (2.70 Å) Mn(1)-Mn(3) bond lengths. In the second Mn site, Mn(2) is bonded to two equivalent Sm(1), two equivalent Mn(1), two equivalent Mn(3), two equivalent Mn(4), two equivalent Mn(5), and two equivalent Mn(7) atoms to form distorted MnSm2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Sm2Mn10 cuboctahedra, corners with two equivalent Mn(7)Sm2Mn10 cuboctahedra, corners with four equivalent C(1)Sm2Mn4 octahedra,  an edgeedge with one Mn(2)Sm2Mn10 cuboctahedra, edges with two equivalent Mn(7)Sm2Mn10 cuboctahedra, edges with two equivalent C(1)Sm2Mn4 octahedra,  a faceface with one Mn(2)Sm2Mn10 cuboctahedra, and faces with two equivalent Mn(7)Sm2Mn10 cuboctahedra. The corner-sharing octahedral tilt angles range from 22-28°. Both Mn(2)-Mn(3) bond lengths are 2.41 Å. Both Mn(2)-Mn(4) bond lengths are 2.54 Å. Both Mn(2)-Mn(5) bond lengths are 2.68 Å. Both Mn(2)-Mn(7) bond lengths are 2.41 Å. In the third Mn site, Mn(3) is bonded in a single-bond geometry to one Mn(2), one Mn(5), one Mn(6), one Mn(7), two equivalent Mn(1), and one C(1) atom. The Mn(3)-Mn(5) bond length is 2.58 Å. The Mn(3)-Mn(6) bond length is 2.43 Å. The Mn(3)-Mn(7) bond length is 2.41 Å. The Mn(3)-C(1) bond length is 1.89 Å. In the fourth Mn site, Mn(4) is bonded in a single-bond geometry to one Mn(1), one Mn(2), one Mn(5), one Mn(6), one Mn(7), and one C(1) atom. The Mn(4)-Mn(5) bond length is 2.68 Å. The Mn(4)-Mn(6) bond length is 2.42 Å. The Mn(4)-Mn(7) bond length is 2.43 Å. The Mn(4)-C(1) bond length is 1.90 Å. In the fifth Mn site, Mn(5) is bonded in a 12-coordinate geometry to three equivalent Sm(1), one Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(4), and two equivalent Mn(7) atoms. Both Mn(5)-Mn(7) bond lengths are 2.44 Å. In the sixth Mn site, Mn(6) is bonded in a 12-coordinate geometry to two equivalent Sm(1), two equivalent Mn(1), four equivalent Mn(3), and four equivalent Mn(4) atoms. In the seventh Mn site, Mn(7) is bonded to two equivalent Sm(1), two equivalent Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(4), and two equivalent Mn(5) atoms to form distorted MnSm2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Sm2Mn10 cuboctahedra, corners with two equivalent Mn(7)Sm2Mn10 cuboctahedra, corners with two equivalent C(1)Sm2Mn4 octahedra, edges with two equivalent Mn(2)Sm2Mn10 cuboctahedra, faces with two equivalent Mn(2)Sm2Mn10 cuboctahedra, faces with two equivalent Mn(7)Sm2Mn10 cuboctahedra, and faces with two equivalent C(1)Sm2Mn4 octahedra. The corner-sharing octahedral tilt angles are 48°. C(1) is bonded to two equivalent Sm(1), two equivalent Mn(3), and two equivalent Mn(4) atoms to form CSm2Mn4 octahedra that share corners with two equivalent Mn(7)Sm2Mn10 cuboctahedra, corners with four equivalent Mn(2)Sm2Mn10 cuboctahedra, corners with two equivalent C(1)Sm2Mn4 octahedra, edges with two equivalent Mn(2)Sm2Mn10 cuboctahedra, and faces with two equivalent Mn(7)Sm2Mn10 cuboctahedra. The corner-sharing octahedral tilt angles are 63°.