MgMo2(HO2)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(5), and two equivalent O(2) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Mo(2)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 75-78°. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(3), one O(5), one O(7), and two equivalent O(4) atoms to form distorted MoO6 octahedra that share corners with two equivalent Mo(1)O6 octahedra, edges with two equivalent Mo(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 32°. In the second Mo site, Mo(2) is bonded to one O(2), one O(4), one O(6), one O(8), and two equivalent O(3) atoms to form distorted MoO6 octahedra that share corners with two equivalent Mo(2)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, and edges with two equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(7) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(8) atom. In the third H site, H(3) is bonded in a distorted linear geometry to one O(2) and one O(7) atom. In the fourth H site, H(4) is bonded in a distorted linear geometry to one O(1) and one O(8) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mo(1), and one H(4) atom. In the second O site, O(2) is bonded to two equivalent Mg(1), one Mo(2), and one H(3) atom to form distorted corner-sharing OMg2MoH trigonal pyramids. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mo(1) and two equivalent Mo(2) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Mo(2) and two equivalent Mo(1) atoms. In the fifth O site, O(5) is bonded in an L-shaped geometry to one Mg(1) and one Mo(1) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one Mo(2) atom. In the seventh O site, O(7) is bonded in a distorted water-like geometry to one Mo(1), one H(1), and one H(3) atom. In the eighth O site, O(8) is bonded in a water-like geometry to one Mo(2), one H(2), and one H(4) atom.
MgMo2(HO2)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(5), and two equivalent O(2) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Mo(2)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 75-78°. The Mg(1)-O(1) bond length is 2.00 Å. The Mg(1)-O(5) bond length is 2.06 Å. There is one shorter (2.09 Å) and one longer (2.12 Å) Mg(1)-O(2) bond length. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(3), one O(5), one O(7), and two equivalent O(4) atoms to form distorted MoO6 octahedra that share corners with two equivalent Mo(1)O6 octahedra, edges with two equivalent Mo(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 32°. The Mo(1)-O(1) bond length is 1.89 Å. The Mo(1)-O(3) bond length is 2.22 Å. The Mo(1)-O(5) bond length is 1.80 Å. The Mo(1)-O(7) bond length is 2.25 Å. There is one shorter (2.02 Å) and one longer (2.03 Å) Mo(1)-O(4) bond length. In the second Mo site, Mo(2) is bonded to one O(2), one O(4), one O(6), one O(8), and two equivalent O(3) atoms to form distorted MoO6 octahedra that share corners with two equivalent Mo(2)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, and edges with two equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. The Mo(2)-O(2) bond length is 2.02 Å. The Mo(2)-O(4) bond length is 2.10 Å. The Mo(2)-O(6) bond length is 1.73 Å. The Mo(2)-O(8) bond length is 2.32 Å. There is one shorter (2.01 Å) and one longer (2.02 Å) Mo(2)-O(3) bond length. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(7) atom. The H(1)-O(7) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(8) atom. The H(2)-O(8) bond length is 0.98 Å. In the third H site, H(3) is bonded in a distorted linear geometry to one O(2) and one O(7) atom. The H(3)-O(2) bond length is 1.63 Å. The H(3)-O(7) bond length is 1.01 Å. In the fourth H site, H(4) is bonded in a distorted linear geometry to one O(1) and one O(8) atom. The H(4)-O(1) bond length is 1.60 Å. The H(4)-O(8) bond length is 1.02 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mo(1), and one H(4) atom. In the second O site, O(2) is bonded to two equivalent Mg(1), one Mo(2), and one H(3) atom to form distorted corner-sharing OMg2MoH trigonal pyramids. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mo(1) and two equivalent Mo(2) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Mo(2) and two equivalent Mo(1) atoms. In the fifth O site, O(5) is bonded in an L-shaped geometry to one Mg(1) and one Mo(1) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one Mo(2) atom. In the seventh O site, O(7) is bonded in a distorted water-like geometry to one Mo(1), one H(1), and one H(3) atom. In the eighth O site, O(8) is bonded in a water-like geometry to one Mo(2), one H(2), and one H(4) atom.