Na2Sn4O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. Na(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NaO6 octahedra that share corners with three equivalent Sn(1)O6 octahedra, corners with six equivalent Sn(2)O6 pentagonal pyramids, edges with three equivalent Sn(1)O6 octahedra, and  a faceface with one Na(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted SnO6 octahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Sn(1)O6 octahedra, corners with three equivalent Sn(2)O6 pentagonal pyramids, edges with three equivalent Na(1)O6 octahedra, and  a faceface with one Sn(2)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 51-52°. In the second Sn site, Sn(2) is bonded to six equivalent O(2) atoms to form distorted SnO6 pentagonal pyramids that share corners with three equivalent Sn(1)O6 octahedra, corners with six equivalent Na(1)O6 octahedra, edges with three equivalent Sn(2)O6 pentagonal pyramids, and  a faceface with one Sn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-67°. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1) and two equivalent Sn(1) atoms to form a mixture of distorted corner and edge-sharing ONa2Sn2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Na(1), one Sn(1), and two equivalent Sn(2) atoms.
Na2Sn4O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. Na(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NaO6 octahedra that share corners with three equivalent Sn(1)O6 octahedra, corners with six equivalent Sn(2)O6 pentagonal pyramids, edges with three equivalent Sn(1)O6 octahedra, and  a faceface with one Na(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. All Na(1)-O(1) bond lengths are 2.39 Å. All Na(1)-O(2) bond lengths are 2.32 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted SnO6 octahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Sn(1)O6 octahedra, corners with three equivalent Sn(2)O6 pentagonal pyramids, edges with three equivalent Na(1)O6 octahedra, and  a faceface with one Sn(2)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 51-52°. All Sn(1)-O(1) bond lengths are 2.04 Å. All Sn(1)-O(2) bond lengths are 2.23 Å. In the second Sn site, Sn(2) is bonded to six equivalent O(2) atoms to form distorted SnO6 pentagonal pyramids that share corners with three equivalent Sn(1)O6 octahedra, corners with six equivalent Na(1)O6 octahedra, edges with three equivalent Sn(2)O6 pentagonal pyramids, and  a faceface with one Sn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-67°. There are three shorter (2.07 Å) and three longer (2.18 Å) Sn(2)-O(2) bond lengths. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1) and two equivalent Sn(1) atoms to form a mixture of distorted corner and edge-sharing ONa2Sn2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Na(1), one Sn(1), and two equivalent Sn(2) atoms.