Sc2Al4(CO)3 crystallizes in the trigonal R3m space group. There are two inequivalent Sc sites. In the first Sc site, Sc(1) is bonded in a 6-coordinate geometry to three equivalent C(1) and three equivalent C(2) atoms. In the second Sc site, Sc(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent C(3) and one O(2) atom to form AlC3O trigonal pyramids that share corners with three equivalent Al(3)C4 tetrahedra and corners with six equivalent Al(1)C3O trigonal pyramids. In the second Al site, Al(2) is bonded in a 4-coordinate geometry to one C(2), one O(1), and three equivalent O(3) atoms. In the third Al site, Al(3) is bonded to one C(3) and three equivalent C(1) atoms to form distorted AlC4 tetrahedra that share corners with six equivalent Al(3)C4 tetrahedra and corners with three equivalent Al(1)C3O trigonal pyramids. In the fourth Al site, Al(4) is bonded to three equivalent C(2) and one O(3) atom to form distorted corner-sharing AlC3O trigonal pyramids. There are three inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Sc(1) and three equivalent Al(3) atoms to form CSc3Al3 octahedra that share corners with three equivalent C(3)Al4 trigonal pyramids and edges with six equivalent C(1)Sc3Al3 octahedra. In the second C site, C(2) is bonded in a 7-coordinate geometry to three equivalent Sc(1), one Al(2), and three equivalent Al(4) atoms. In the third C site, C(3) is bonded to one Al(3) and three equivalent Al(1) atoms to form distorted CAl4 trigonal pyramids that share corners with three equivalent C(1)Sc3Al3 octahedra, corners with three equivalent O(2)Sc3Al tetrahedra, and corners with six equivalent C(3)Al4 trigonal pyramids. The corner-sharing octahedral tilt angles are 63°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Sc(2) and one Al(2) atom. In the second O site, O(2) is bonded to three equivalent Sc(2) and one Al(1) atom to form OSc3Al tetrahedra that share corners with six equivalent O(2)Sc3Al tetrahedra and corners with three equivalent C(3)Al4 trigonal pyramids. In the third O site, O(3) is bonded to one Al(4) and three equivalent Al(2) atoms to form corner-sharing OAl4 trigonal pyramids.
Sc2Al4(CO)3 crystallizes in the trigonal R3m space group. There are two inequivalent Sc sites. In the first Sc site, Sc(1) is bonded in a 6-coordinate geometry to three equivalent C(1) and three equivalent C(2) atoms. All Sc(1)-C(1) bond lengths are 2.26 Å. All Sc(1)-C(2) bond lengths are 2.66 Å. In the second Sc site, Sc(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All Sc(2)-O(1) bond lengths are 2.31 Å. All Sc(2)-O(2) bond lengths are 2.06 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent C(3) and one O(2) atom to form AlC3O trigonal pyramids that share corners with three equivalent Al(3)C4 tetrahedra and corners with six equivalent Al(1)C3O trigonal pyramids. All Al(1)-C(3) bond lengths are 1.97 Å. The Al(1)-O(2) bond length is 1.91 Å. In the second Al site, Al(2) is bonded in a 4-coordinate geometry to one C(2), one O(1), and three equivalent O(3) atoms. The Al(2)-C(2) bond length is 2.48 Å. The Al(2)-O(1) bond length is 1.75 Å. All Al(2)-O(3) bond lengths are 1.96 Å. In the third Al site, Al(3) is bonded to one C(3) and three equivalent C(1) atoms to form distorted AlC4 tetrahedra that share corners with six equivalent Al(3)C4 tetrahedra and corners with three equivalent Al(1)C3O trigonal pyramids. The Al(3)-C(3) bond length is 1.92 Å. All Al(3)-C(1) bond lengths are 2.18 Å. In the fourth Al site, Al(4) is bonded to three equivalent C(2) and one O(3) atom to form distorted corner-sharing AlC3O trigonal pyramids. All Al(4)-C(2) bond lengths are 1.97 Å. The Al(4)-O(3) bond length is 1.91 Å. There are three inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Sc(1) and three equivalent Al(3) atoms to form CSc3Al3 octahedra that share corners with three equivalent C(3)Al4 trigonal pyramids and edges with six equivalent C(1)Sc3Al3 octahedra. In the second C site, C(2) is bonded in a 7-coordinate geometry to three equivalent Sc(1), one Al(2), and three equivalent Al(4) atoms. In the third C site, C(3) is bonded to one Al(3) and three equivalent Al(1) atoms to form distorted CAl4 trigonal pyramids that share corners with three equivalent C(1)Sc3Al3 octahedra, corners with three equivalent O(2)Sc3Al tetrahedra, and corners with six equivalent C(3)Al4 trigonal pyramids. The corner-sharing octahedral tilt angles are 63°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Sc(2) and one Al(2) atom. In the second O site, O(2) is bonded to three equivalent Sc(2) and one Al(1) atom to form OSc3Al tetrahedra that share corners with six equivalent O(2)Sc3Al tetrahedra and corners with three equivalent C(3)Al4 trigonal pyramids. In the third O site, O(3) is bonded to one Al(4) and three equivalent Al(2) atoms to form corner-sharing OAl4 trigonal pyramids.