Na6MgMo2(NO3)2 crystallizes in the monoclinic Pm space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to one N(1), one O(3), and two equivalent O(1) atoms to form NaNO3 tetrahedra that share corners with two equivalent Mo(1)NO3 tetrahedra, corners with two equivalent Mo(2)NO3 tetrahedra, and corners with four equivalent Na(2)NO3 tetrahedra. In the second Na site, Na(2) is bonded to one N(1), one O(1), one O(2), and one O(4) atom to form NaNO3 tetrahedra that share corners with two equivalent Na(1)NO3 tetrahedra, corners with two equivalent Na(2)NO3 tetrahedra, corners with two equivalent Mo(1)NO3 tetrahedra, and corners with two equivalent Mo(2)NO3 tetrahedra. In the third Na site, Na(3) is bonded in a rectangular see-saw-like geometry to one N(2), one O(1), one O(2), and one O(3) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one N(2), one O(4), and two equivalent O(2) atoms. Mg(1) is bonded in a 5-coordinate geometry to one N(2), two equivalent O(1), and two equivalent O(2) atoms. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one N(2), one O(4), and two equivalent O(1) atoms to form MoNO3 tetrahedra that share corners with two equivalent Na(1)NO3 tetrahedra and corners with four equivalent Na(2)NO3 tetrahedra. In the second Mo site, Mo(2) is bonded to one N(1), one O(3), and two equivalent O(2) atoms to form MoNO3 tetrahedra that share corners with two equivalent Na(1)NO3 tetrahedra and corners with four equivalent Na(2)NO3 tetrahedra. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Na(1), two equivalent Na(2), and one Mo(2) atom to form NNa3Mo tetrahedra that share corners with two equivalent O(4)Na3Mo tetrahedra and corners with four equivalent O(1)Na3MgMo trigonal bipyramids. In the second N site, N(2) is bonded to one Na(4), two equivalent Na(3), one Mg(1), and one Mo(1) atom to form distorted NNa3MgMo trigonal bipyramids that share corners with two equivalent O(4)Na3Mo tetrahedra, corners with two equivalent O(1)Na3MgMo trigonal bipyramids, and edges with two equivalent O(1)Na3MgMo trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Na(3), one Mg(1), and one Mo(1) atom to form distorted ONa3MgMo trigonal bipyramids that share corners with two equivalent N(1)Na3Mo tetrahedra, corners with two equivalent O(4)Na3Mo tetrahedra,  a cornercorner with one N(2)Na3MgMo trigonal bipyramid,  a cornercorner with one O(1)Na3MgMo trigonal bipyramid,  an edgeedge with one N(2)Na3MgMo trigonal bipyramid, and  an edgeedge with one O(1)Na3MgMo trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Na(4), one Mg(1), and one Mo(2) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), two equivalent Na(3), and one Mo(2) atom. In the fourth O site, O(4) is bonded to one Na(4), two equivalent Na(2), and one Mo(1) atom to form ONa3Mo tetrahedra that share corners with two equivalent N(1)Na3Mo tetrahedra, corners with two equivalent N(2)Na3MgMo trigonal bipyramids, and corners with four equivalent O(1)Na3MgMo trigonal bipyramids.
Na6MgMo2(NO3)2 crystallizes in the monoclinic Pm space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to one N(1), one O(3), and two equivalent O(1) atoms to form NaNO3 tetrahedra that share corners with two equivalent Mo(1)NO3 tetrahedra, corners with two equivalent Mo(2)NO3 tetrahedra, and corners with four equivalent Na(2)NO3 tetrahedra. The Na(1)-N(1) bond length is 2.37 Å. The Na(1)-O(3) bond length is 2.43 Å. Both Na(1)-O(1) bond lengths are 2.61 Å. In the second Na site, Na(2) is bonded to one N(1), one O(1), one O(2), and one O(4) atom to form NaNO3 tetrahedra that share corners with two equivalent Na(1)NO3 tetrahedra, corners with two equivalent Na(2)NO3 tetrahedra, corners with two equivalent Mo(1)NO3 tetrahedra, and corners with two equivalent Mo(2)NO3 tetrahedra. The Na(2)-N(1) bond length is 2.43 Å. The Na(2)-O(1) bond length is 2.37 Å. The Na(2)-O(2) bond length is 2.44 Å. The Na(2)-O(4) bond length is 2.27 Å. In the third Na site, Na(3) is bonded in a rectangular see-saw-like geometry to one N(2), one O(1), one O(2), and one O(3) atom. The Na(3)-N(2) bond length is 2.30 Å. The Na(3)-O(1) bond length is 2.32 Å. The Na(3)-O(2) bond length is 2.38 Å. The Na(3)-O(3) bond length is 2.20 Å. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one N(2), one O(4), and two equivalent O(2) atoms. The Na(4)-N(2) bond length is 2.36 Å. The Na(4)-O(4) bond length is 2.38 Å. Both Na(4)-O(2) bond lengths are 2.68 Å. Mg(1) is bonded in a 5-coordinate geometry to one N(2), two equivalent O(1), and two equivalent O(2) atoms. The Mg(1)-N(2) bond length is 2.08 Å. Both Mg(1)-O(1) bond lengths are 2.02 Å. Both Mg(1)-O(2) bond lengths are 2.55 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one N(2), one O(4), and two equivalent O(1) atoms to form MoNO3 tetrahedra that share corners with two equivalent Na(1)NO3 tetrahedra and corners with four equivalent Na(2)NO3 tetrahedra. The Mo(1)-N(2) bond length is 1.88 Å. The Mo(1)-O(4) bond length is 1.99 Å. Both Mo(1)-O(1) bond lengths are 2.06 Å. In the second Mo site, Mo(2) is bonded to one N(1), one O(3), and two equivalent O(2) atoms to form MoNO3 tetrahedra that share corners with two equivalent Na(1)NO3 tetrahedra and corners with four equivalent Na(2)NO3 tetrahedra. The Mo(2)-N(1) bond length is 1.73 Å. The Mo(2)-O(3) bond length is 1.87 Å. Both Mo(2)-O(2) bond lengths are 1.89 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Na(1), two equivalent Na(2), and one Mo(2) atom to form NNa3Mo tetrahedra that share corners with two equivalent O(4)Na3Mo tetrahedra and corners with four equivalent O(1)Na3MgMo trigonal bipyramids. In the second N site, N(2) is bonded to one Na(4), two equivalent Na(3), one Mg(1), and one Mo(1) atom to form distorted NNa3MgMo trigonal bipyramids that share corners with two equivalent O(4)Na3Mo tetrahedra, corners with two equivalent O(1)Na3MgMo trigonal bipyramids, and edges with two equivalent O(1)Na3MgMo trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Na(3), one Mg(1), and one Mo(1) atom to form distorted ONa3MgMo trigonal bipyramids that share corners with two equivalent N(1)Na3Mo tetrahedra, corners with two equivalent O(4)Na3Mo tetrahedra,  a cornercorner with one N(2)Na3MgMo trigonal bipyramid,  a cornercorner with one O(1)Na3MgMo trigonal bipyramid,  an edgeedge with one N(2)Na3MgMo trigonal bipyramid, and  an edgeedge with one O(1)Na3MgMo trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Na(4), one Mg(1), and one Mo(2) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), two equivalent Na(3), and one Mo(2) atom. In the fourth O site, O(4) is bonded to one Na(4), two equivalent Na(2), and one Mo(1) atom to form ONa3Mo tetrahedra that share corners with two equivalent N(1)Na3Mo tetrahedra, corners with two equivalent N(2)Na3MgMo trigonal bipyramids, and corners with four equivalent O(1)Na3MgMo trigonal bipyramids.