Sc3OsC4 crystallizes in the monoclinic C2/m space group. There are four inequivalent Sc sites. In the first Sc site, Sc(1) is bonded to four equivalent C(1) and four equivalent C(2) atoms to form distorted ScC8 hexagonal bipyramids that share corners with four equivalent C(1)Sc5OsC pentagonal bipyramids, corners with four equivalent C(2)Sc5OsC pentagonal bipyramids, and faces with two equivalent Sc(2)Os4C8 cuboctahedra. In the second Sc site, Sc(2) is bonded to four equivalent Os(1), four equivalent C(1), and four equivalent C(2) atoms to form distorted ScOs4C8 cuboctahedra that share corners with four equivalent C(1)Sc5OsC pentagonal bipyramids, corners with four equivalent C(2)Sc5OsC pentagonal bipyramids, edges with two equivalent Sc(2)Os4C8 cuboctahedra, edges with four equivalent C(1)Sc5OsC pentagonal bipyramids, edges with four equivalent C(2)Sc5OsC pentagonal bipyramids, and faces with two equivalent Sc(1)C8 hexagonal bipyramids. In the third Sc site, Sc(3) is bonded in a 6-coordinate geometry to two equivalent C(1) and four equivalent C(2) atoms. In the fourth Sc site, Sc(4) is bonded in a 6-coordinate geometry to two equivalent C(2) and four equivalent C(1) atoms. Os(1) is bonded in a distorted square co-planar geometry to two equivalent Sc(2), two equivalent C(1), and two equivalent C(2) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Sc(1), one Sc(2), one Sc(3), two equivalent Sc(4), one Os(1), and one C(1) atom to form distorted CSc5OsC pentagonal bipyramids that share  a cornercorner with one Sc(2)Os4C8 cuboctahedra,  a cornercorner with one Sc(1)C8 hexagonal bipyramid, corners with six equivalent C(1)Sc5OsC pentagonal bipyramids, corners with seven equivalent C(2)Sc5OsC pentagonal bipyramids,  an edgeedge with one Sc(2)Os4C8 cuboctahedra,  an edgeedge with one C(1)Sc5OsC pentagonal bipyramid, edges with four equivalent C(2)Sc5OsC pentagonal bipyramids,  a faceface with one C(2)Sc5OsC pentagonal bipyramid, and faces with two equivalent C(1)Sc5OsC pentagonal bipyramids. In the second C site, C(2) is bonded to one Sc(1), one Sc(2), one Sc(4), two equivalent Sc(3), one Os(1), and one C(2) atom to form distorted CSc5OsC pentagonal bipyramids that share  a cornercorner with one Sc(2)Os4C8 cuboctahedra,  a cornercorner with one Sc(1)C8 hexagonal bipyramid, corners with six equivalent C(2)Sc5OsC pentagonal bipyramids, corners with seven equivalent C(1)Sc5OsC pentagonal bipyramids,  an edgeedge with one Sc(2)Os4C8 cuboctahedra,  an edgeedge with one C(2)Sc5OsC pentagonal bipyramid, edges with four equivalent C(1)Sc5OsC pentagonal bipyramids,  a faceface with one C(1)Sc5OsC pentagonal bipyramid, and faces with two equivalent C(2)Sc5OsC pentagonal bipyramids.
Sc3OsC4 crystallizes in the monoclinic C2/m space group. There are four inequivalent Sc sites. In the first Sc site, Sc(1) is bonded to four equivalent C(1) and four equivalent C(2) atoms to form distorted ScC8 hexagonal bipyramids that share corners with four equivalent C(1)Sc5OsC pentagonal bipyramids, corners with four equivalent C(2)Sc5OsC pentagonal bipyramids, and faces with two equivalent Sc(2)Os4C8 cuboctahedra. All Sc(1)-C(1) bond lengths are 2.42 Å. All Sc(1)-C(2) bond lengths are 2.43 Å. In the second Sc site, Sc(2) is bonded to four equivalent Os(1), four equivalent C(1), and four equivalent C(2) atoms to form distorted ScOs4C8 cuboctahedra that share corners with four equivalent C(1)Sc5OsC pentagonal bipyramids, corners with four equivalent C(2)Sc5OsC pentagonal bipyramids, edges with two equivalent Sc(2)Os4C8 cuboctahedra, edges with four equivalent C(1)Sc5OsC pentagonal bipyramids, edges with four equivalent C(2)Sc5OsC pentagonal bipyramids, and faces with two equivalent Sc(1)C8 hexagonal bipyramids. All Sc(2)-Os(1) bond lengths are 2.74 Å. All Sc(2)-C(1) bond lengths are 2.41 Å. All Sc(2)-C(2) bond lengths are 2.42 Å. In the third Sc site, Sc(3) is bonded in a 6-coordinate geometry to two equivalent C(1) and four equivalent C(2) atoms. Both Sc(3)-C(1) bond lengths are 2.39 Å. There are two shorter (2.36 Å) and two longer (2.39 Å) Sc(3)-C(2) bond lengths. In the fourth Sc site, Sc(4) is bonded in a 6-coordinate geometry to two equivalent C(2) and four equivalent C(1) atoms. Both Sc(4)-C(2) bond lengths are 2.39 Å. There are two shorter (2.35 Å) and two longer (2.39 Å) Sc(4)-C(1) bond lengths. Os(1) is bonded in a distorted square co-planar geometry to two equivalent Sc(2), two equivalent C(1), and two equivalent C(2) atoms. Both Os(1)-C(1) bond lengths are 2.20 Å. Both Os(1)-C(2) bond lengths are 2.20 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Sc(1), one Sc(2), one Sc(3), two equivalent Sc(4), one Os(1), and one C(1) atom to form distorted CSc5OsC pentagonal bipyramids that share  a cornercorner with one Sc(2)Os4C8 cuboctahedra,  a cornercorner with one Sc(1)C8 hexagonal bipyramid, corners with six equivalent C(1)Sc5OsC pentagonal bipyramids, corners with seven equivalent C(2)Sc5OsC pentagonal bipyramids,  an edgeedge with one Sc(2)Os4C8 cuboctahedra,  an edgeedge with one C(1)Sc5OsC pentagonal bipyramid, edges with four equivalent C(2)Sc5OsC pentagonal bipyramids,  a faceface with one C(2)Sc5OsC pentagonal bipyramid, and faces with two equivalent C(1)Sc5OsC pentagonal bipyramids. The C(1)-C(1) bond length is 1.44 Å. In the second C site, C(2) is bonded to one Sc(1), one Sc(2), one Sc(4), two equivalent Sc(3), one Os(1), and one C(2) atom to form distorted CSc5OsC pentagonal bipyramids that share  a cornercorner with one Sc(2)Os4C8 cuboctahedra,  a cornercorner with one Sc(1)C8 hexagonal bipyramid, corners with six equivalent C(2)Sc5OsC pentagonal bipyramids, corners with seven equivalent C(1)Sc5OsC pentagonal bipyramids,  an edgeedge with one Sc(2)Os4C8 cuboctahedra,  an edgeedge with one C(2)Sc5OsC pentagonal bipyramid, edges with four equivalent C(1)Sc5OsC pentagonal bipyramids,  a faceface with one C(1)Sc5OsC pentagonal bipyramid, and faces with two equivalent C(2)Sc5OsC pentagonal bipyramids. The C(2)-C(2) bond length is 1.44 Å.