Y12(OsC3)5 crystallizes in the hexagonal P-62m space group. There are three inequivalent Y sites. In the first Y site, Y(1) is bonded in a rectangular see-saw-like geometry to two equivalent C(2) and two equivalent C(4) atoms. In the second Y site, Y(2) is bonded to one C(1), one C(2), one C(3), and two equivalent C(4) atoms to form distorted YC5 square pyramids that share corners with three equivalent Y(2)C5 square pyramids,  a cornercorner with one C(3)Y4C trigonal bipyramid, and  an edgeedge with one Y(2)C5 square pyramid. In the third Y site, Y(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 Y(2), two equivalent Y(3), one Os(1), and one C(3) atom. In the second C site, C(2) is bonded to two equivalent Y(1), two equivalent Y(2), and two equivalent Os(1) atoms to form CY4Os2 octahedra that share corners with four equivalent C(2)Y4Os2 octahedra, edges with four equivalent C(4)Y5Os octahedra, and  an edgeedge with one C(3)Y4C trigonal bipyramid. The corner-sharing octahedral tilt angles range from 0-36°. In the third C site, C(3) is bonded to two equivalent Y(2), two equivalent Y(3), and one C(1) atom to form distorted CY4C trigonal bipyramids that share corners with four equivalent C(4)Y5Os octahedra, corners with two equivalent Y(2)C5 square pyramids, corners with two equivalent C(3)Y4C trigonal bipyramids,  an edgeedge with one C(2)Y4Os2 octahedra, and edges with four equivalent C(4)Y5Os octahedra. The corner-sharing octahedral tilt angles are 88°. In the fourth C site, C(4) is bonded to one Y(1), two equivalent Y(2), two equivalent Y(3), and one Os(2) atom to form CY5Os octahedra that share corners with five equivalent C(4)Y5Os octahedra, corners with two equivalent C(3)Y4C trigonal bipyramids, edges with two equivalent C(2)Y4Os2 octahedra, edges with three equivalent C(4)Y5Os octahedra, and edges with two equivalent C(3)Y4C trigonal bipyramids. The corner-sharing octahedral tilt angles range from 6-47°.
Y12(OsC3)5 crystallizes in the hexagonal P-62m space group. There are three inequivalent Y sites. In the first Y site, Y(1) is bonded in a rectangular see-saw-like geometry to two equivalent C(2) and two equivalent C(4) atoms. Both Y(1)-C(2) bond lengths are 2.54 Å. Both Y(1)-C(4) bond lengths are 2.51 Å. In the second Y site, Y(2) is bonded to one C(1), one C(2), one C(3), and two equivalent C(4) atoms to form distorted YC5 square pyramids that share corners with three equivalent Y(2)C5 square pyramids,  a cornercorner with one C(3)Y4C trigonal bipyramid, and  an edgeedge with one Y(2)C5 square pyramid. The Y(2)-C(1) bond length is 2.53 Å. The Y(2)-C(2) bond length is 2.40 Å. The Y(2)-C(3) bond length is 2.55 Å. Both Y(2)-C(4) bond lengths are 2.54 Å. In the third Y site, Y(3) is bonded in a 8-coordinate geometry to two equivalent C(1), two equivalent C(3), and four equivalent C(4) atoms. Both Y(3)-C(1) bond lengths are 2.75 Å. Both Y(3)-C(3) bond lengths are 2.55 Å. There are two shorter (2.66 Å) and two longer (2.87 Å) Y(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 1.90 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded in a 6-coordinate geometry to two equivalent Y(2), two equivalent Y(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 Y(1), two equivalent Y(2), and two equivalent Os(1) atoms to form CY4Os2 octahedra that share corners with four equivalent C(2)Y4Os2 octahedra, edges with four equivalent C(4)Y5Os octahedra, and  an edgeedge with one C(3)Y4C trigonal bipyramid. The corner-sharing octahedral tilt angles range from 0-36°. In the third C site, C(3) is bonded to two equivalent Y(2), two equivalent Y(3), and one C(1) atom to form distorted CY4C trigonal bipyramids that share corners with four equivalent C(4)Y5Os octahedra, corners with two equivalent Y(2)C5 square pyramids, corners with two equivalent C(3)Y4C trigonal bipyramids,  an edgeedge with one C(2)Y4Os2 octahedra, and edges with four equivalent C(4)Y5Os octahedra. The corner-sharing octahedral tilt angles are 88°. In the fourth C site, C(4) is bonded to one Y(1), two equivalent Y(2), two equivalent Y(3), and one Os(2) atom to form CY5Os octahedra that share corners with five equivalent C(4)Y5Os octahedra, corners with two equivalent C(3)Y4C trigonal bipyramids, edges with two equivalent C(2)Y4Os2 octahedra, edges with three equivalent C(4)Y5Os octahedra, and edges with two equivalent C(3)Y4C trigonal bipyramids. The corner-sharing octahedral tilt angles range from 6-47°.