Na4MgTi2(GeO5)2 crystallizes in the monoclinic Cm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(5), two equivalent O(2), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(6) atom to form distorted NaO5 square pyramids that share  a cornercorner with one Na(2)O5 square pyramid, corners with two equivalent Na(3)O5 square pyramids, corners with four equivalent Ge(1)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. In the third Na site, Na(3) is bonded to one O(5), two equivalent O(1), and two equivalent O(4) atoms to form distorted NaO5 square pyramids that share corners with four equivalent Na(2)O5 square pyramids and corners with four equivalent Ge(1)O4 tetrahedra. Mg(1) is bonded to one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share corners with six equivalent Na(2)O5 square pyramids and edges with two equivalent Ge(1)O4 tetrahedra. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 5-coordinate geometry to one O(6), two equivalent O(1), and two equivalent O(2) atoms. In the second Ti site, Ti(2) is bonded in a 5-coordinate geometry to one O(5), two equivalent O(3), and two equivalent O(4) atoms. Ge(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form GeO4 tetrahedra that share corners with two equivalent Na(3)O5 square pyramids, corners with four equivalent Na(2)O5 square pyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Na(2), one Na(3), one Ti(1), and one Ge(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Mg(1), one Ti(1), and one Ge(1) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Mg(1), one Ti(2), and one Ge(1) atom to form distorted ONa2MgTiGe square pyramids that share corners with two equivalent O(4)Na2TiGe tetrahedra,  an edgeedge with one O(4)Na2TiGe tetrahedra, and  a faceface with one O(3)Na2MgTiGe square pyramid. In the fourth O site, O(4) is bonded to one Na(2), one Na(3), one Ti(2), and one Ge(1) atom to form distorted ONa2TiGe tetrahedra that share corners with two equivalent O(3)Na2MgTiGe square pyramids,  an edgeedge with one O(3)Na2MgTiGe square pyramid, and  an edgeedge with one O(4)Na2TiGe tetrahedra. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(3), and one Ti(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Na(2), one Mg(1), and one Ti(1) atom.
Na4MgTi2(GeO5)2 crystallizes in the monoclinic Cm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(5), two equivalent O(2), and two equivalent O(3) atoms. The Na(1)-O(5) bond length is 2.27 Å. Both Na(1)-O(2) bond lengths are 2.37 Å. Both Na(1)-O(3) bond lengths are 2.55 Å. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(6) atom to form distorted NaO5 square pyramids that share  a cornercorner with one Na(2)O5 square pyramid, corners with two equivalent Na(3)O5 square pyramids, corners with four equivalent Ge(1)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. The Na(2)-O(1) bond length is 2.37 Å. The Na(2)-O(2) bond length is 2.60 Å. The Na(2)-O(3) bond length is 2.58 Å. The Na(2)-O(4) bond length is 2.33 Å. The Na(2)-O(6) bond length is 2.64 Å. In the third Na site, Na(3) is bonded to one O(5), two equivalent O(1), and two equivalent O(4) atoms to form distorted NaO5 square pyramids that share corners with four equivalent Na(2)O5 square pyramids and corners with four equivalent Ge(1)O4 tetrahedra. The Na(3)-O(5) bond length is 2.44 Å. Both Na(3)-O(1) bond lengths are 2.44 Å. Both Na(3)-O(4) bond lengths are 2.37 Å. Mg(1) is bonded to one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share corners with six equivalent Na(2)O5 square pyramids and edges with two equivalent Ge(1)O4 tetrahedra. The Mg(1)-O(6) bond length is 2.01 Å. Both Mg(1)-O(2) bond lengths are 2.09 Å. Both Mg(1)-O(3) bond lengths are 2.00 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 5-coordinate geometry to one O(6), two equivalent O(1), and two equivalent O(2) atoms. The Ti(1)-O(6) bond length is 1.84 Å. Both Ti(1)-O(1) bond lengths are 1.97 Å. Both Ti(1)-O(2) bond lengths are 2.26 Å. In the second Ti site, Ti(2) is bonded in a 5-coordinate geometry to one O(5), two equivalent O(3), and two equivalent O(4) atoms. The Ti(2)-O(5) bond length is 1.75 Å. Both Ti(2)-O(3) bond lengths are 2.24 Å. Both Ti(2)-O(4) bond lengths are 2.05 Å. Ge(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form GeO4 tetrahedra that share corners with two equivalent Na(3)O5 square pyramids, corners with four equivalent Na(2)O5 square pyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Ge(1)-O(1) bond length is 1.78 Å. The Ge(1)-O(2) bond length is 1.81 Å. The Ge(1)-O(3) bond length is 1.85 Å. The Ge(1)-O(4) bond length is 1.77 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Na(2), one Na(3), one Ti(1), and one Ge(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Mg(1), one Ti(1), and one Ge(1) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Mg(1), one Ti(2), and one Ge(1) atom to form distorted ONa2MgTiGe square pyramids that share corners with two equivalent O(4)Na2TiGe tetrahedra,  an edgeedge with one O(4)Na2TiGe tetrahedra, and  a faceface with one O(3)Na2MgTiGe square pyramid. In the fourth O site, O(4) is bonded to one Na(2), one Na(3), one Ti(2), and one Ge(1) atom to form distorted ONa2TiGe tetrahedra that share corners with two equivalent O(3)Na2MgTiGe square pyramids,  an edgeedge with one O(3)Na2MgTiGe square pyramid, and  an edgeedge with one O(4)Na2TiGe tetrahedra. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(3), and one Ti(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Na(2), one Mg(1), and one Ti(1) atom.