Tm12(OsC3)5 crystallizes in the hexagonal P-62m space group. There are three inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a rectangular see-saw-like geometry to two equivalent C(2) and two equivalent C(4) atoms. In the second Tm site, Tm(2) is bonded to one C(1), one C(2), one C(3), and two equivalent C(4) atoms to form distorted TmC5 square pyramids that share corners with three equivalent Tm(2)C5 square pyramids,  a cornercorner with one C(3)Tm4C trigonal bipyramid, and  an edgeedge with one Tm(2)C5 square pyramid. In the third Tm site, Tm(3) is bonded in a 8-coordinate geometry to two equivalent C(1), two equivalent C(3), and four equivalent C(4) atoms. There are two inequivalent Os sites. In the first Os site, Os(1) is bonded in a 3-coordinate geometry to one C(1) and two equivalent C(2) atoms. In the second Os site, Os(2) is bonded in a trigonal planar geometry to three equivalent C(4) atoms. There are four inequivalent C sites. In the first C site, C(1) is bonded in a 6-coordinate geometry to two equivalent Tm(2), two equivalent Tm(3), one Os(1), and one C(3) atom. In the second C site, C(2) is bonded to two equivalent Tm(1), two equivalent Tm(2), and two equivalent Os(1) atoms to form CTm4Os2 octahedra that share corners with four equivalent C(2)Tm4Os2 octahedra, edges with four equivalent C(4)Tm5Os octahedra, and  an edgeedge with one C(3)Tm4C trigonal bipyramid. The corner-sharing octahedral tilt angles range from 2-34°. In the third C site, C(3) is bonded to two equivalent Tm(2), two equivalent Tm(3), and one C(1) atom to form distorted CTm4C trigonal bipyramids that share corners with four equivalent C(4)Tm5Os octahedra, corners with two equivalent Tm(2)C5 square pyramids, corners with two equivalent C(3)Tm4C trigonal bipyramids,  an edgeedge with one C(2)Tm4Os2 octahedra, and edges with four equivalent C(4)Tm5Os octahedra. The corner-sharing octahedral tilt angles are 87°. In the fourth C site, C(4) is bonded to one Tm(1), two equivalent Tm(2), two equivalent Tm(3), and one Os(2) atom to form CTm5Os octahedra that share corners with five equivalent C(4)Tm5Os octahedra, corners with two equivalent C(3)Tm4C trigonal bipyramids, edges with two equivalent C(2)Tm4Os2 octahedra, edges with three equivalent C(4)Tm5Os octahedra, and edges with two equivalent C(3)Tm4C trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-50°.
Tm12(OsC3)5 crystallizes in the hexagonal P-62m space group. There are three inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a rectangular see-saw-like geometry to two equivalent C(2) and two equivalent C(4) atoms. Both Tm(1)-C(2) bond lengths are 2.48 Å. Both Tm(1)-C(4) bond lengths are 2.44 Å. In the second Tm site, Tm(2) is bonded to one C(1), one C(2), one C(3), and two equivalent C(4) atoms to form distorted TmC5 square pyramids that share corners with three equivalent Tm(2)C5 square pyramids,  a cornercorner with one C(3)Tm4C trigonal bipyramid, and  an edgeedge with one Tm(2)C5 square pyramid. The Tm(2)-C(1) bond length is 2.49 Å. The Tm(2)-C(2) bond length is 2.33 Å. The Tm(2)-C(3) bond length is 2.48 Å. Both Tm(2)-C(4) bond lengths are 2.48 Å. In the third Tm site, Tm(3) is bonded in a 8-coordinate geometry to two equivalent C(1), two equivalent C(3), and four equivalent C(4) atoms. Both Tm(3)-C(1) bond lengths are 2.70 Å. Both Tm(3)-C(3) bond lengths are 2.49 Å. There are two shorter (2.60 Å) and two longer (2.85 Å) Tm(3)-C(4) bond lengths. There are two inequivalent Os sites. In the first Os site, Os(1) is bonded in a 3-coordinate geometry to one C(1) and two equivalent C(2) atoms. The Os(1)-C(1) bond length is 1.87 Å. Both Os(1)-C(2) bond lengths are 2.02 Å. In the second Os site, Os(2) is bonded in a trigonal planar geometry to three equivalent C(4) atoms. All Os(2)-C(4) bond lengths are 1.91 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded in a 6-coordinate geometry to two equivalent Tm(2), two equivalent Tm(3), one Os(1), and one C(3) atom. The C(1)-C(3) bond length is 1.33 Å. In the second C site, C(2) is bonded to two equivalent Tm(1), two equivalent Tm(2), and two equivalent Os(1) atoms to form CTm4Os2 octahedra that share corners with four equivalent C(2)Tm4Os2 octahedra, edges with four equivalent C(4)Tm5Os octahedra, and  an edgeedge with one C(3)Tm4C trigonal bipyramid. The corner-sharing octahedral tilt angles range from 2-34°. In the third C site, C(3) is bonded to two equivalent Tm(2), two equivalent Tm(3), and one C(1) atom to form distorted CTm4C trigonal bipyramids that share corners with four equivalent C(4)Tm5Os octahedra, corners with two equivalent Tm(2)C5 square pyramids, corners with two equivalent C(3)Tm4C trigonal bipyramids,  an edgeedge with one C(2)Tm4Os2 octahedra, and edges with four equivalent C(4)Tm5Os octahedra. The corner-sharing octahedral tilt angles are 87°. In the fourth C site, C(4) is bonded to one Tm(1), two equivalent Tm(2), two equivalent Tm(3), and one Os(2) atom to form CTm5Os octahedra that share corners with five equivalent C(4)Tm5Os octahedra, corners with two equivalent C(3)Tm4C trigonal bipyramids, edges with two equivalent C(2)Tm4Os2 octahedra, edges with three equivalent C(4)Tm5Os octahedra, and edges with two equivalent C(3)Tm4C trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-50°.