MgCu4(SO5)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(2), one O(3), and one O(5) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one S(2)O4 tetrahedra,  a cornercorner with one Cu(2)O5 trigonal bipyramid, and  an edgeedge with one S(1)O4 tetrahedra. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted square co-planar geometry to one O(10), one O(2), one O(3), and one O(6) atom. In the second Cu site, Cu(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(9) atom to form CuO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one S(1)O4 tetrahedra, and corners with two equivalent S(2)O4 tetrahedra. In the third Cu site, Cu(3) is bonded in a 4-coordinate geometry to one O(1), one O(5), one O(6), and one O(7) atom. In the fourth Cu site, Cu(4) is bonded in a 4-coordinate geometry to one O(4), one O(5), one O(6), and one O(7) atom. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(2), one O(3), one O(8), and one O(9) atom to form SO4 tetrahedra that share  a cornercorner with one Cu(2)O5 trigonal bipyramid and  an edgeedge with one Mg(1)O4 tetrahedra. In the second S site, S(2) is bonded to one O(1), one O(10), one O(4), and one O(7) atom to form SO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra and corners with two equivalent Cu(2)O5 trigonal bipyramids. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Cu(2), one Cu(3), and one S(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 S(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one S(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Cu(2), one Cu(4), and one S(2) atom. In the fifth O site, O(5) is bonded to one Mg(1), one Cu(2), one Cu(3), and one Cu(4) atom to form distorted corner-sharing OMgCu3 tetrahedra. In the sixth O site, O(6) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Cu(4) atom to form corner-sharing OCu4 tetrahedra. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Cu(3), one Cu(4), and one S(2) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one S(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Cu(2) and one S(1) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one S(2) atom.
MgCu4(SO5)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(2), one O(3), and one O(5) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one S(2)O4 tetrahedra,  a cornercorner with one Cu(2)O5 trigonal bipyramid, and  an edgeedge with one S(1)O4 tetrahedra. The Mg(1)-O(10) bond length is 1.95 Å. The Mg(1)-O(2) bond length is 2.06 Å. The Mg(1)-O(3) bond length is 2.06 Å. The Mg(1)-O(5) bond length is 1.93 Å. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted square co-planar geometry to one O(10), one O(2), one O(3), and one O(6) atom. The Cu(1)-O(10) bond length is 2.18 Å. The Cu(1)-O(2) bond length is 2.03 Å. The Cu(1)-O(3) bond length is 2.03 Å. The Cu(1)-O(6) bond length is 1.97 Å. In the second Cu site, Cu(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(9) atom to form CuO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one S(1)O4 tetrahedra, and corners with two equivalent S(2)O4 tetrahedra. The Cu(2)-O(1) bond length is 2.28 Å. The Cu(2)-O(4) bond length is 2.27 Å. The Cu(2)-O(5) bond length is 1.96 Å. The Cu(2)-O(6) bond length is 1.97 Å. The Cu(2)-O(9) bond length is 2.07 Å. In the third Cu site, Cu(3) is bonded in a 4-coordinate geometry to one O(1), one O(5), one O(6), and one O(7) atom. The Cu(3)-O(1) bond length is 2.19 Å. The Cu(3)-O(5) bond length is 1.94 Å. The Cu(3)-O(6) bond length is 1.87 Å. The Cu(3)-O(7) bond length is 2.53 Å. In the fourth Cu site, Cu(4) is bonded in a 4-coordinate geometry to one O(4), one O(5), one O(6), and one O(7) atom. The Cu(4)-O(4) bond length is 2.18 Å. The Cu(4)-O(5) bond length is 1.94 Å. The Cu(4)-O(6) bond length is 1.87 Å. The Cu(4)-O(7) bond length is 2.49 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(2), one O(3), one O(8), and one O(9) atom to form SO4 tetrahedra that share  a cornercorner with one Cu(2)O5 trigonal bipyramid and  an edgeedge with one Mg(1)O4 tetrahedra. The S(1)-O(2) bond length is 1.55 Å. The S(1)-O(3) bond length is 1.55 Å. The S(1)-O(8) bond length is 1.45 Å. The S(1)-O(9) bond length is 1.46 Å. In the second S site, S(2) is bonded to one O(1), one O(10), one O(4), and one O(7) atom to form SO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra and corners with two equivalent Cu(2)O5 trigonal bipyramids. The S(2)-O(1) bond length is 1.49 Å. The S(2)-O(10) bond length is 1.54 Å. The S(2)-O(4) bond length is 1.49 Å. The S(2)-O(7) bond length is 1.46 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Cu(2), one Cu(3), and one S(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 S(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one S(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Cu(2), one Cu(4), and one S(2) atom. In the fifth O site, O(5) is bonded to one Mg(1), one Cu(2), one Cu(3), and one Cu(4) atom to form distorted corner-sharing OMgCu3 tetrahedra. In the sixth O site, O(6) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Cu(4) atom to form corner-sharing OCu4 tetrahedra. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Cu(3), one Cu(4), and one S(2) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one S(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Cu(2) and one S(1) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one S(2) atom.