Mg2Cu2CH2O9 crystallizes in the monoclinic C2/c space group. Mg(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted edge-sharing MgO5 square pyramids. Cu(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(5) atoms. C(1) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(3) atoms. H(1) is bonded in a distorted linear geometry to one O(2) and one O(4) atom. There are five inequivalent O sites. In the first O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Cu(1), and one H(1) atom. In the second O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(1) atom. In the third O site, O(4) is bonded in a 3-coordinate geometry to one C(1) and two equivalent H(1) atoms. In the fourth O site, O(5) is bonded in a water-like geometry to two equivalent Cu(1) atoms. In the fifth O site, O(1) is bonded in a trigonal non-coplanar geometry to two equivalent Mg(1) and one Cu(1) atom.
Mg2Cu2CH2O9 crystallizes in the monoclinic C2/c space group. Mg(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted edge-sharing MgO5 square pyramids. The Mg(1)-O(3) bond length is 2.01 Å. There is one shorter (2.00 Å) and one longer (2.07 Å) Mg(1)-O(1) bond length. There is one shorter (2.09 Å) and one longer (2.10 Å) Mg(1)-O(2) bond length. Cu(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(5) atoms. The Cu(1)-O(1) bond length is 1.83 Å. The Cu(1)-O(2) bond length is 1.90 Å. Both Cu(1)-O(5) bond lengths are 1.81 Å. C(1) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(3) atoms. The C(1)-O(4) bond length is 1.30 Å. Both C(1)-O(3) bond lengths are 1.29 Å. H(1) is bonded in a distorted linear geometry to one O(2) and one O(4) atom. The H(1)-O(2) bond length is 1.01 Å. The H(1)-O(4) bond length is 1.58 Å. There are five inequivalent O sites. In the first O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Cu(1), and one H(1) atom. In the second O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(1) atom. In the third O site, O(4) is bonded in a 3-coordinate geometry to one C(1) and two equivalent H(1) atoms. In the fourth O site, O(5) is bonded in a water-like geometry to two equivalent Cu(1) atoms. In the fifth O site, O(1) is bonded in a trigonal non-coplanar geometry to two equivalent Mg(1) and one Cu(1) atom.