Na3Mg(CuO2)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 4-coordinate geometry to one O(1), one O(3), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(2), one O(4), and two equivalent O(1) atoms. Mg(1) is bonded to one O(2), one O(3), and two equivalent O(4) atoms to form distorted corner-sharing MgO4 tetrahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(4) atoms. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), two equivalent Na(3), and two equivalent Cu(2) atoms to form ONa4Cu2 octahedra that share corners with two equivalent O(2)Na3MgCu2 octahedra, edges with two equivalent O(1)Na4Cu2 octahedra, and edges with three equivalent O(2)Na3MgCu2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second O site, O(2) is bonded to one Na(3), two equivalent Na(2), one Mg(1), and two equivalent Cu(2) atoms to form distorted ONa3MgCu2 octahedra that share corners with two equivalent O(1)Na4Cu2 octahedra, edges with two equivalent O(2)Na3MgCu2 octahedra, and edges with three equivalent O(1)Na4Cu2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), one Mg(1), and two equivalent Cu(1) atoms. In the fourth O site, O(4) is bonded in a 7-coordinate geometry to one Na(3), two equivalent Na(1), two equivalent Mg(1), and two equivalent Cu(1) atoms.
Na3Mg(CuO2)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 4-coordinate geometry to one O(1), one O(3), and two equivalent O(4) atoms. The Na(1)-O(1) bond length is 2.20 Å. The Na(1)-O(3) bond length is 2.29 Å. Both Na(1)-O(4) bond lengths are 2.54 Å. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Na(2)-O(1) bond length is 2.24 Å. Both Na(2)-O(2) bond lengths are 2.41 Å. Both Na(2)-O(3) bond lengths are 2.52 Å. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(2), one O(4), and two equivalent O(1) atoms. The Na(3)-O(2) bond length is 2.63 Å. The Na(3)-O(4) bond length is 2.72 Å. Both Na(3)-O(1) bond lengths are 2.33 Å. Mg(1) is bonded to one O(2), one O(3), and two equivalent O(4) atoms to form distorted corner-sharing MgO4 tetrahedra. The Mg(1)-O(2) bond length is 2.00 Å. The Mg(1)-O(3) bond length is 2.04 Å. Both Mg(1)-O(4) bond lengths are 2.03 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(4) atoms. Both Cu(1)-O(3) bond lengths are 1.98 Å. Both Cu(1)-O(4) bond lengths are 2.28 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. Both Cu(2)-O(1) bond lengths are 2.03 Å. Both Cu(2)-O(2) bond lengths are 2.05 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), two equivalent Na(3), and two equivalent Cu(2) atoms to form ONa4Cu2 octahedra that share corners with two equivalent O(2)Na3MgCu2 octahedra, edges with two equivalent O(1)Na4Cu2 octahedra, and edges with three equivalent O(2)Na3MgCu2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second O site, O(2) is bonded to one Na(3), two equivalent Na(2), one Mg(1), and two equivalent Cu(2) atoms to form distorted ONa3MgCu2 octahedra that share corners with two equivalent O(1)Na4Cu2 octahedra, edges with two equivalent O(2)Na3MgCu2 octahedra, and edges with three equivalent O(1)Na4Cu2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), one Mg(1), and two equivalent Cu(1) atoms. In the fourth O site, O(4) is bonded in a 7-coordinate geometry to one Na(3), two equivalent Na(1), two equivalent Mg(1), and two equivalent Cu(1) atoms.