Na2Mo2Se2O11 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to two equivalent O(4) and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form NaO7 pentagonal bipyramids that share corners with four equivalent Mo(1)O6 octahedra and edges with two equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-46°. Mo(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted MoO6 octahedra that share  a cornercorner with one Mo(1)O6 octahedra, corners with two equivalent Na(2)O7 pentagonal bipyramids, and  an edgeedge with one Na(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 38°. Se(1) is bonded in a trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. There are six inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Na(2) and two equivalent Mo(1) atoms. In the second O site, O(4) is bonded in a trigonal planar geometry to one Na(1), one Mo(1), and one Se(1) atom. In the third O site, O(5) is bonded in a 3-coordinate geometry to one Na(2), one Mo(1), and one Se(1) atom. In the fourth O site, O(6) is bonded in a distorted trigonal planar geometry to one Na(1), one Mo(1), and one Se(1) atom. In the fifth O site, O(1) is bonded in a linear geometry to one Na(2) and one Mo(1) atom. In the sixth O site, O(2) is bonded in a 2-coordinate geometry to one Na(2) and one Mo(1) atom.
Na2Mo2Se2O11 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to two equivalent O(4) and two equivalent O(6) atoms. Both Na(1)-O(4) bond lengths are 2.45 Å. Both Na(1)-O(6) bond lengths are 2.57 Å. In the second Na site, Na(2) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form NaO7 pentagonal bipyramids that share corners with four equivalent Mo(1)O6 octahedra and edges with two equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-46°. The Na(2)-O(3) bond length is 2.50 Å. Both Na(2)-O(1) bond lengths are 2.46 Å. Both Na(2)-O(2) bond lengths are 2.52 Å. Both Na(2)-O(5) bond lengths are 2.47 Å. Mo(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted MoO6 octahedra that share  a cornercorner with one Mo(1)O6 octahedra, corners with two equivalent Na(2)O7 pentagonal bipyramids, and  an edgeedge with one Na(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 38°. The Mo(1)-O(1) bond length is 1.74 Å. The Mo(1)-O(2) bond length is 1.76 Å. The Mo(1)-O(3) bond length is 1.94 Å. The Mo(1)-O(4) bond length is 2.05 Å. The Mo(1)-O(5) bond length is 2.19 Å. The Mo(1)-O(6) bond length is 2.32 Å. Se(1) is bonded in a trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. The Se(1)-O(4) bond length is 1.78 Å. The Se(1)-O(5) bond length is 1.72 Å. The Se(1)-O(6) bond length is 1.72 Å. There are six inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Na(2) and two equivalent Mo(1) atoms. In the second O site, O(4) is bonded in a trigonal planar geometry to one Na(1), one Mo(1), and one Se(1) atom. In the third O site, O(5) is bonded in a 3-coordinate geometry to one Na(2), one Mo(1), and one Se(1) atom. In the fourth O site, O(6) is bonded in a distorted trigonal planar geometry to one Na(1), one Mo(1), and one Se(1) atom. In the fifth O site, O(1) is bonded in a linear geometry to one Na(2) and one Mo(1) atom. In the sixth O site, O(2) is bonded in a 2-coordinate geometry to one Na(2) and one Mo(1) atom.