Nd2Mn17C2 crystallizes in the monoclinic C2/m space group. Nd(1) is bonded in a distorted bent 120 degrees geometry to one Mn(1), one Mn(4), two equivalent Mn(2), two equivalent Mn(5), three equivalent Mn(7), 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 Nd(1), one Mn(1), one Mn(4), one Mn(7), two equivalent Mn(2), two equivalent Mn(5), two equivalent Mn(6), and four equivalent Mn(3) atoms. In the second Mn site, Mn(2) is bonded to two equivalent Nd(1), two equivalent Mn(1), two equivalent Mn(3), two equivalent Mn(5), two equivalent Mn(6), and two equivalent Mn(7) atoms to form distorted MnNd2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with four equivalent C(1)Nd2Mn4 octahedra,  an edgeedge with one Mn(2)Nd2Mn10 cuboctahedra, edges with two equivalent Mn(5)Nd2Mn10 cuboctahedra, edges with two equivalent C(1)Nd2Mn4 octahedra,  a faceface with one Mn(2)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, and faces with four equivalent Mn(7)Nd3Mn9 cuboctahedra. The corner-sharing octahedral tilt angles range from 20-28°. In the third Mn site, Mn(3) is bonded in a single-bond geometry to one Mn(2), one Mn(4), one Mn(5), one Mn(7), two equivalent Mn(1), and one C(1) atom. In the fourth Mn site, Mn(4) is bonded in a 12-coordinate geometry to two equivalent Nd(1), two equivalent Mn(1), four equivalent Mn(3), and four equivalent Mn(6) atoms. In the fifth Mn site, Mn(5) is bonded to two equivalent Nd(1), two equivalent Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(6), and two equivalent Mn(7) atoms to form distorted MnNd2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with two equivalent C(1)Nd2Mn4 octahedra, edges with two equivalent Mn(2)Nd2Mn10 cuboctahedra, edges with two equivalent Mn(7)Nd3Mn9 cuboctahedra, faces with two equivalent Mn(2)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(7)Nd3Mn9 cuboctahedra, and faces with two equivalent C(1)Nd2Mn4 octahedra. The corner-sharing octahedral tilt angles are 47°. In the sixth Mn site, Mn(6) is bonded in a single-bond geometry to one Mn(1), one Mn(2), one Mn(4), one Mn(5), one Mn(7), and one C(1) atom. In the seventh Mn site, Mn(7) is bonded to three equivalent Nd(1), one Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(5), and two equivalent Mn(6) atoms to form distorted MnNd3Mn9 cuboctahedra that share corners with two equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with four equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with four equivalent C(1)Nd2Mn4 octahedra,  an edgeedge with one Mn(7)Nd3Mn9 cuboctahedra, edges with two equivalent Mn(5)Nd2Mn10 cuboctahedra,  a faceface with one Mn(7)Nd3Mn9 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, faces with four equivalent Mn(2)Nd2Mn10 cuboctahedra, and faces with two equivalent C(1)Nd2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 61-70°. C(1) is bonded to two equivalent Nd(1), two equivalent Mn(3), and two equivalent Mn(6) atoms to form CNd2Mn4 octahedra that share corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with four equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with four equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with two equivalent C(1)Nd2Mn4 octahedra, edges with two equivalent Mn(2)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, and faces with two equivalent Mn(7)Nd3Mn9 cuboctahedra. The corner-sharing octahedral tilt angles are 63°.
Nd2Mn17C2 crystallizes in the monoclinic C2/m space group. Nd(1) is bonded in a distorted bent 120 degrees geometry to one Mn(1), one Mn(4), two equivalent Mn(2), two equivalent Mn(5), three equivalent Mn(7), and two equivalent C(1) atoms. The Nd(1)-Mn(1) bond length is 3.18 Å. The Nd(1)-Mn(4) bond length is 3.42 Å. Both Nd(1)-Mn(2) bond lengths are 3.14 Å. Both Nd(1)-Mn(5) bond lengths are 3.33 Å. There are a spread of Nd(1)-Mn(7) bond distances ranging from 3.00-3.39 Å. Both Nd(1)-C(1) bond lengths are 2.54 Å. There are seven inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 14-coordinate geometry to one Nd(1), one Mn(1), one Mn(4), one Mn(7), two equivalent Mn(2), two equivalent Mn(5), two equivalent Mn(6), and four equivalent Mn(3) atoms. The Mn(1)-Mn(1) bond length is 2.27 Å. The Mn(1)-Mn(4) bond length is 2.65 Å. The Mn(1)-Mn(7) bond length is 2.64 Å. Both Mn(1)-Mn(2) bond lengths are 2.58 Å. Both Mn(1)-Mn(5) bond lengths are 2.66 Å. Both Mn(1)-Mn(6) bond lengths are 2.56 Å. There are two shorter (2.67 Å) and two longer (2.68 Å) Mn(1)-Mn(3) bond lengths. In the second Mn site, Mn(2) is bonded to two equivalent Nd(1), two equivalent Mn(1), two equivalent Mn(3), two equivalent Mn(5), two equivalent Mn(6), and two equivalent Mn(7) atoms to form distorted MnNd2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with four equivalent C(1)Nd2Mn4 octahedra,  an edgeedge with one Mn(2)Nd2Mn10 cuboctahedra, edges with two equivalent Mn(5)Nd2Mn10 cuboctahedra, edges with two equivalent C(1)Nd2Mn4 octahedra,  a faceface with one Mn(2)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, and faces with four equivalent Mn(7)Nd3Mn9 cuboctahedra. The corner-sharing octahedral tilt angles range from 20-28°. Both Mn(2)-Mn(3) bond lengths are 2.39 Å. Both Mn(2)-Mn(5) bond lengths are 2.41 Å. Both Mn(2)-Mn(6) bond lengths are 2.53 Å. Both Mn(2)-Mn(7) bond lengths are 2.72 Å. In the third Mn site, Mn(3) is bonded in a single-bond geometry to one Mn(2), one Mn(4), one Mn(5), one Mn(7), two equivalent Mn(1), and one C(1) atom. The Mn(3)-Mn(4) bond length is 2.41 Å. The Mn(3)-Mn(5) bond length is 2.43 Å. The Mn(3)-Mn(7) bond length is 2.58 Å. The Mn(3)-C(1) bond length is 1.89 Å. In the fourth Mn site, Mn(4) is bonded in a 12-coordinate geometry to two equivalent Nd(1), two equivalent Mn(1), four equivalent Mn(3), and four equivalent Mn(6) atoms. All Mn(4)-Mn(6) bond lengths are 2.41 Å. In the fifth Mn site, Mn(5) is bonded to two equivalent Nd(1), two equivalent Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(6), and two equivalent Mn(7) atoms to form distorted MnNd2Mn10 cuboctahedra that share corners with two equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with two equivalent C(1)Nd2Mn4 octahedra, edges with two equivalent Mn(2)Nd2Mn10 cuboctahedra, edges with two equivalent Mn(7)Nd3Mn9 cuboctahedra, faces with two equivalent Mn(2)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(7)Nd3Mn9 cuboctahedra, and faces with two equivalent C(1)Nd2Mn4 octahedra. The corner-sharing octahedral tilt angles are 47°. Both Mn(5)-Mn(6) bond lengths are 2.42 Å. Both Mn(5)-Mn(7) bond lengths are 2.45 Å. In the sixth Mn site, Mn(6) is bonded in a single-bond geometry to one Mn(1), one Mn(2), one Mn(4), one Mn(5), one Mn(7), and one C(1) atom. The Mn(6)-Mn(7) bond length is 2.67 Å. The Mn(6)-C(1) bond length is 1.91 Å. In the seventh Mn site, Mn(7) is bonded to three equivalent Nd(1), one Mn(1), two equivalent Mn(2), two equivalent Mn(3), two equivalent Mn(5), and two equivalent Mn(6) atoms to form distorted MnNd3Mn9 cuboctahedra that share corners with two equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with four equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with four equivalent C(1)Nd2Mn4 octahedra,  an edgeedge with one Mn(7)Nd3Mn9 cuboctahedra, edges with two equivalent Mn(5)Nd2Mn10 cuboctahedra,  a faceface with one Mn(7)Nd3Mn9 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, faces with four equivalent Mn(2)Nd2Mn10 cuboctahedra, and faces with two equivalent C(1)Nd2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 61-70°. C(1) is bonded to two equivalent Nd(1), two equivalent Mn(3), and two equivalent Mn(6) atoms to form CNd2Mn4 octahedra that share corners with two equivalent Mn(5)Nd2Mn10 cuboctahedra, corners with four equivalent Mn(2)Nd2Mn10 cuboctahedra, corners with four equivalent Mn(7)Nd3Mn9 cuboctahedra, corners with two equivalent C(1)Nd2Mn4 octahedra, edges with two equivalent Mn(2)Nd2Mn10 cuboctahedra, faces with two equivalent Mn(5)Nd2Mn10 cuboctahedra, and faces with two equivalent Mn(7)Nd3Mn9 cuboctahedra. The corner-sharing octahedral tilt angles are 63°.