MgCr4(CuO4)2 crystallizes in the orthorhombic F222 space group. Mg(1) is bonded to four equivalent Cr(1) and four equivalent O(2) atoms to form distorted MgCr4O4 tetrahedra that share corners with four equivalent Cu(2)O4 tetrahedra. Cr(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent O(1), and three equivalent O(2) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a tetrahedral geometry to four equivalent O(1) atoms. In the second Cu site, Cu(2) is bonded to four equivalent O(2) atoms to form CuO4 tetrahedra that share corners with four equivalent Mg(1)Cr4O4 tetrahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to three equivalent Cr(1) and one Cu(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Mg(1), three equivalent Cr(1), and one Cu(2) atom.
MgCr4(CuO4)2 crystallizes in the orthorhombic F222 space group. Mg(1) is bonded to four equivalent Cr(1) and four equivalent O(2) atoms to form distorted MgCr4O4 tetrahedra that share corners with four equivalent Cu(2)O4 tetrahedra. All Mg(1)-Cr(1) bond lengths are 2.24 Å. All Mg(1)-O(2) bond lengths are 1.85 Å. Cr(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent O(1), and three equivalent O(2) atoms. There are two shorter (1.98 Å) and one longer (2.00 Å) Cr(1)-O(1) bond length. There are a spread of Cr(1)-O(2) bond distances ranging from 2.12-2.52 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a tetrahedral geometry to four equivalent O(1) atoms. All Cu(1)-O(1) bond lengths are 2.28 Å. In the second Cu site, Cu(2) is bonded to four equivalent O(2) atoms to form CuO4 tetrahedra that share corners with four equivalent Mg(1)Cr4O4 tetrahedra. All Cu(2)-O(2) bond lengths are 2.13 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to three equivalent Cr(1) and one Cu(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Mg(1), three equivalent Cr(1), and one Cu(2) atom.