Mg(MoO2)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to one O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO5 square pyramids that share corners with two equivalent Mo(1)O6 octahedra, corners with four equivalent Mo(2)O6 octahedra, edges with three equivalent Mo(1)O6 octahedra, edges with two equivalent Mg(1)O5 square pyramids, and  a faceface with one Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-59°. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form MoO6 octahedra that share corners with four equivalent Mo(2)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids, edges with four equivalent Mo(1)O6 octahedra, and edges with three equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 49-56°. In the second Mo site, Mo(2) is bonded to one O(1), two equivalent O(2), and three equivalent O(4) atoms to form distorted MoO6 octahedra that share corners with four equivalent Mo(1)O6 octahedra, corners with four equivalent Mg(1)O5 square pyramids, edges with four equivalent Mo(2)O6 octahedra, and  a faceface with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 49-56°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mo(2), and two equivalent Mo(1) atoms to form OMgMo3 trigonal pyramids that share corners with two equivalent O(3)Mg2Mo3 square pyramids, corners with two equivalent O(1)MgMo3 trigonal pyramids, and edges with three equivalent O(3)Mg2Mo3 square pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mo(1) and two equivalent Mo(2) atoms. In the third O site, O(3) is bonded to two equivalent Mg(1) and three equivalent Mo(1) atoms to form OMg2Mo3 square pyramids that share corners with two equivalent O(1)MgMo3 trigonal pyramids, edges with four equivalent O(3)Mg2Mo3 square pyramids, and edges with three equivalent O(1)MgMo3 trigonal pyramids. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Mg(1) and three equivalent Mo(2) atoms.
Mg(MoO2)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to one O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO5 square pyramids that share corners with two equivalent Mo(1)O6 octahedra, corners with four equivalent Mo(2)O6 octahedra, edges with three equivalent Mo(1)O6 octahedra, edges with two equivalent Mg(1)O5 square pyramids, and  a faceface with one Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-59°. The Mg(1)-O(1) bond length is 2.10 Å. Both Mg(1)-O(3) bond lengths are 2.12 Å. Both Mg(1)-O(4) bond lengths are 2.14 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form MoO6 octahedra that share corners with four equivalent Mo(2)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids, edges with four equivalent Mo(1)O6 octahedra, and edges with three equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 49-56°. The Mo(1)-O(2) bond length is 2.10 Å. Both Mo(1)-O(1) bond lengths are 2.11 Å. There are two shorter (2.27 Å) and one longer (2.32 Å) Mo(1)-O(3) bond length. In the second Mo site, Mo(2) is bonded to one O(1), two equivalent O(2), and three equivalent O(4) atoms to form distorted MoO6 octahedra that share corners with four equivalent Mo(1)O6 octahedra, corners with four equivalent Mg(1)O5 square pyramids, edges with four equivalent Mo(2)O6 octahedra, and  a faceface with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 49-56°. The Mo(2)-O(1) bond length is 2.18 Å. Both Mo(2)-O(2) bond lengths are 2.09 Å. There is one shorter (2.19 Å) and two longer (2.33 Å) Mo(2)-O(4) bond lengths. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mo(2), and two equivalent Mo(1) atoms to form OMgMo3 trigonal pyramids that share corners with two equivalent O(3)Mg2Mo3 square pyramids, corners with two equivalent O(1)MgMo3 trigonal pyramids, and edges with three equivalent O(3)Mg2Mo3 square pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mo(1) and two equivalent Mo(2) atoms. In the third O site, O(3) is bonded to two equivalent Mg(1) and three equivalent Mo(1) atoms to form OMg2Mo3 square pyramids that share corners with two equivalent O(1)MgMo3 trigonal pyramids, edges with four equivalent O(3)Mg2Mo3 square pyramids, and edges with three equivalent O(1)MgMo3 trigonal pyramids. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Mg(1) and three equivalent Mo(2) atoms.