MgCu2(GeO3)2 crystallizes in the monoclinic P2/m space group. Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form MgO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra and edges with four equivalent Ge(1)O4 trigonal pyramids. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to four equivalent O(2) atoms. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to four equivalent O(3) atoms. Ge(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form GeO4 trigonal pyramids that share corners with two equivalent Ge(1)O4 trigonal pyramids and edges with two equivalent Mg(1)O6 octahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Ge(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one Ge(1) atom. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Cu(2), and one Ge(1) atom to form a mixture of distorted edge and corner-sharing OMg2Cu2Ge trigonal bipyramids.
MgCu2(GeO3)2 crystallizes in the monoclinic P2/m space group. Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form MgO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra and edges with four equivalent Ge(1)O4 trigonal pyramids. Both Mg(1)-O(1) bond lengths are 2.17 Å. All Mg(1)-O(3) bond lengths are 2.13 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to four equivalent O(2) atoms. All Cu(1)-O(2) bond lengths are 2.05 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to four equivalent O(3) atoms. All Cu(2)-O(3) bond lengths are 2.19 Å. Ge(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form GeO4 trigonal pyramids that share corners with two equivalent Ge(1)O4 trigonal pyramids and edges with two equivalent Mg(1)O6 octahedra. The Ge(1)-O(2) bond length is 1.74 Å. The Ge(1)-O(3) bond length is 1.87 Å. Both Ge(1)-O(1) bond lengths are 1.86 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Ge(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one Ge(1) atom. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Cu(2), and one Ge(1) atom to form a mixture of distorted edge and corner-sharing OMg2Cu2Ge trigonal bipyramids.