MgCu2(SO5)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(2), one O(3), one O(5), and one O(6) atom to form distorted MgO5 trigonal bipyramids that share corners with two equivalent S(1)O4 tetrahedra,  a cornercorner with one Cu(1)O5 trigonal bipyramid,  an edgeedge with one S(2)O4 tetrahedra, and  an edgeedge with one Cu(1)O5 trigonal bipyramid. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(2), one O(4), one O(5), and one O(6) atom to form distorted CuO5 trigonal bipyramids that share  a cornercorner with one S(1)O4 tetrahedra, corners with two equivalent S(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(7), and one O(8) atom. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(3), one O(5), one O(7), and one O(9) atom to form SO4 tetrahedra that share  a cornercorner with one Cu(1)O5 trigonal bipyramid and corners with two equivalent Mg(1)O5 trigonal bipyramids. In the second S site, S(2) is bonded to one O(10), one O(4), one O(6), and one O(8) atom to form SO4 tetrahedra that share corners with two equivalent Cu(1)O5 trigonal bipyramids and  an edgeedge with one Mg(1)O5 trigonal bipyramid. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cu(1) and one Cu(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one Cu(2) atom. In the third O site, O(3) is bonded in a linear geometry to one Mg(1) and one S(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Cu(1) and one S(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one S(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one S(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Cu(2) and one S(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Cu(2) and one S(2) atom. In the ninth O site, O(9) is bonded in a single-bond geometry to one S(1) atom. In the tenth O site, O(10) is bonded in an L-shaped geometry to one Mg(1) and one S(2) atom.
MgCu2(SO5)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(2), one O(3), one O(5), and one O(6) atom to form distorted MgO5 trigonal bipyramids that share corners with two equivalent S(1)O4 tetrahedra,  a cornercorner with one Cu(1)O5 trigonal bipyramid,  an edgeedge with one S(2)O4 tetrahedra, and  an edgeedge with one Cu(1)O5 trigonal bipyramid. The Mg(1)-O(10) bond length is 2.19 Å. The Mg(1)-O(2) bond length is 1.98 Å. The Mg(1)-O(3) bond length is 1.99 Å. The Mg(1)-O(5) bond length is 2.18 Å. The Mg(1)-O(6) bond length is 2.08 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(2), one O(4), one O(5), and one O(6) atom to form distorted CuO5 trigonal bipyramids that share  a cornercorner with one S(1)O4 tetrahedra, corners with two equivalent S(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Cu(1)-O(1) bond length is 1.79 Å. The Cu(1)-O(2) bond length is 1.85 Å. The Cu(1)-O(4) bond length is 2.43 Å. The Cu(1)-O(5) bond length is 1.92 Å. The Cu(1)-O(6) bond length is 1.90 Å. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(7), and one O(8) atom. The Cu(2)-O(1) bond length is 1.79 Å. The Cu(2)-O(2) bond length is 1.85 Å. The Cu(2)-O(7) bond length is 1.88 Å. The Cu(2)-O(8) bond length is 1.91 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(3), one O(5), one O(7), and one O(9) atom to form SO4 tetrahedra that share  a cornercorner with one Cu(1)O5 trigonal bipyramid and corners with two equivalent Mg(1)O5 trigonal bipyramids. The S(1)-O(3) bond length is 1.47 Å. The S(1)-O(5) bond length is 1.57 Å. The S(1)-O(7) bond length is 1.52 Å. The S(1)-O(9) bond length is 1.44 Å. In the second S site, S(2) is bonded to one O(10), one O(4), one O(6), and one O(8) atom to form SO4 tetrahedra that share corners with two equivalent Cu(1)O5 trigonal bipyramids and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The S(2)-O(10) bond length is 1.48 Å. The S(2)-O(4) bond length is 1.45 Å. The S(2)-O(6) bond length is 1.58 Å. The S(2)-O(8) bond length is 1.50 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cu(1) and one Cu(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one Cu(2) atom. In the third O site, O(3) is bonded in a linear geometry to one Mg(1) and one S(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Cu(1) and one S(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one S(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one S(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Cu(2) and one S(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Cu(2) and one S(2) atom. In the ninth O site, O(9) is bonded in a single-bond geometry to one S(1) atom. In the tenth O site, O(10) is bonded in an L-shaped geometry to one Mg(1) and one S(2) atom.