MgMo2O7 crystallizes in the monoclinic P2_1 space group. Mg(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Mo(2)O4 tetrahedra, corners with three equivalent Mo(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form MoO4 tetrahedra that share  a cornercorner with one Mo(2)O4 tetrahedra and corners with three equivalent Mg(1)O5 trigonal bipyramids. In the second Mo site, Mo(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form MoO4 tetrahedra that share  a cornercorner with one Mo(1)O4 tetrahedra and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Mo(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Mo(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Mo(1) and one Mo(2) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Mo(1) atom.
MgMo2O7 crystallizes in the monoclinic P2_1 space group. Mg(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Mo(2)O4 tetrahedra, corners with three equivalent Mo(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The Mg(1)-O(3) bond length is 2.00 Å. The Mg(1)-O(4) bond length is 2.05 Å. The Mg(1)-O(5) bond length is 2.00 Å. There is one shorter (2.01 Å) and one longer (2.61 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(2), one O(4), one O(6), and one O(7) atom to form MoO4 tetrahedra that share  a cornercorner with one Mo(2)O4 tetrahedra and corners with three equivalent Mg(1)O5 trigonal bipyramids. The Mo(1)-O(2) bond length is 1.82 Å. The Mo(1)-O(4) bond length is 1.78 Å. The Mo(1)-O(6) bond length is 1.92 Å. The Mo(1)-O(7) bond length is 1.72 Å. In the second Mo site, Mo(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form MoO4 tetrahedra that share  a cornercorner with one Mo(1)O4 tetrahedra and corners with two equivalent Mg(1)O5 trigonal bipyramids. The Mo(2)-O(1) bond length is 1.71 Å. The Mo(2)-O(3) bond length is 1.79 Å. The Mo(2)-O(5) bond length is 1.80 Å. The Mo(2)-O(6) bond length is 1.94 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Mo(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Mo(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Mo(1) and one Mo(2) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Mo(1) atom.