Mg(MoO2)2 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted MgO6 pentagonal pyramids that share corners with six equivalent Mo(1)O6 octahedra, edges with two equivalent Mo(1)O6 octahedra, and edges with four equivalent Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-17°. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form MoO6 octahedra that share corners with three equivalent Mg(1)O6 pentagonal pyramids, edges with two equivalent Mo(1)O6 octahedra, edges with four equivalent Mo(2)O6 octahedra, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. In the second Mo site, Mo(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MoO6 octahedra that share edges with two equivalent Mo(2)O6 octahedra, edges with four equivalent Mo(1)O6 octahedra, and edges with two equivalent Mg(1)O6 pentagonal pyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mo(1), and two equivalent Mo(2) atoms. In the second O site, O(2) is bonded to one Mg(2), one Mo(1), and two equivalent Mo(2) atoms to form OMgMo3 trigonal pyramids that share corners with four equivalent O(3)Mg2Mo3 trigonal bipyramids, corners with three equivalent O(2)MgMo3 trigonal pyramids, and edges with four equivalent O(3)Mg2Mo3 trigonal bipyramids. In the third O site, O(3) is bonded to one Mg(1), one Mg(2), one Mo(2), and two equivalent Mo(1) atoms to form OMg2Mo3 trigonal bipyramids that share corners with five equivalent O(3)Mg2Mo3 trigonal bipyramids, corners with two equivalent O(2)MgMo3 trigonal pyramids, edges with four equivalent O(3)Mg2Mo3 trigonal bipyramids, and edges with two equivalent O(2)MgMo3 trigonal pyramids.
Mg(MoO2)2 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted MgO6 pentagonal pyramids that share corners with six equivalent Mo(1)O6 octahedra, edges with two equivalent Mo(1)O6 octahedra, and edges with four equivalent Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-17°. Both Mg(1)-O(1) bond lengths are 2.05 Å. All Mg(1)-O(3) bond lengths are 2.39 Å. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. Both Mg(2)-O(2) bond lengths are 2.15 Å. All Mg(2)-O(3) bond lengths are 2.39 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form MoO6 octahedra that share corners with three equivalent Mg(1)O6 pentagonal pyramids, edges with two equivalent Mo(1)O6 octahedra, edges with four equivalent Mo(2)O6 octahedra, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. The Mo(1)-O(1) bond length is 2.19 Å. The Mo(1)-O(2) bond length is 2.13 Å. There are two shorter (2.14 Å) and two longer (2.29 Å) Mo(1)-O(3) bond lengths. In the second Mo site, Mo(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MoO6 octahedra that share edges with two equivalent Mo(2)O6 octahedra, edges with four equivalent Mo(1)O6 octahedra, and edges with two equivalent Mg(1)O6 pentagonal pyramids. Both Mo(2)-O(1) bond lengths are 2.12 Å. Both Mo(2)-O(2) bond lengths are 2.21 Å. Both Mo(2)-O(3) bond lengths are 2.22 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mo(1), and two equivalent Mo(2) atoms. In the second O site, O(2) is bonded to one Mg(2), one Mo(1), and two equivalent Mo(2) atoms to form OMgMo3 trigonal pyramids that share corners with four equivalent O(3)Mg2Mo3 trigonal bipyramids, corners with three equivalent O(2)MgMo3 trigonal pyramids, and edges with four equivalent O(3)Mg2Mo3 trigonal bipyramids. In the third O site, O(3) is bonded to one Mg(1), one Mg(2), one Mo(2), and two equivalent Mo(1) atoms to form OMg2Mo3 trigonal bipyramids that share corners with five equivalent O(3)Mg2Mo3 trigonal bipyramids, corners with two equivalent O(2)MgMo3 trigonal pyramids, edges with four equivalent O(3)Mg2Mo3 trigonal bipyramids, and edges with two equivalent O(2)MgMo3 trigonal pyramids.