MgEu2Ag2(WO4)4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with four equivalent W(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. Eu(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent W sites. In the first W site, W(1) is bonded in a 6-coordinate geometry to one O(4), one O(5), two equivalent O(1), and two equivalent O(3) atoms. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted WO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra and  an edgeedge with one W(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. Ag(1) is bonded in a 4-coordinate geometry to one O(4), one O(5), and two equivalent O(3) atoms. There are five inequivalent O sites. In the first O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Eu(1), one W(1), and one Ag(1) atom. In the second O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Eu(1), one W(1), and one W(2) atom. In the third O site, O(2) is bonded in a bent 150 degrees geometry to one Eu(1) and one W(2) atom. In the fourth O site, O(3) is bonded to one Mg(1), one Eu(1), one W(1), and one Ag(1) atom to form distorted OEuMgAgW trigonal pyramids that share  a cornercorner with one O(3)EuMgAgW trigonal pyramid, edges with two equivalent O(4)MgAgW3 trigonal bipyramids,  an edgeedge with one O(3)EuMgAgW trigonal pyramid, and  a faceface with one O(3)EuMgAgW trigonal pyramid. In the fifth O site, O(4) is bonded to one Mg(1), one W(1), two equivalent W(2), and one Ag(1) atom to form distorted OMgAgW3 trigonal bipyramids that share  a cornercorner with one O(4)MgAgW3 trigonal bipyramid,  an edgeedge with one O(4)MgAgW3 trigonal bipyramid, and edges with four equivalent O(3)EuMgAgW trigonal pyramids.
MgEu2Ag2(WO4)4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with four equivalent W(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. Both Mg(1)-O(4) bond lengths are 2.35 Å. All Mg(1)-O(3) bond lengths are 2.04 Å. Eu(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. Both Eu(1)-O(1) bond lengths are 2.55 Å. Both Eu(1)-O(2) bond lengths are 2.41 Å. Both Eu(1)-O(3) bond lengths are 2.59 Å. Both Eu(1)-O(5) bond lengths are 2.86 Å. There are two inequivalent W sites. In the first W site, W(1) is bonded in a 6-coordinate geometry to one O(4), one O(5), two equivalent O(1), and two equivalent O(3) atoms. The W(1)-O(4) bond length is 2.23 Å. The W(1)-O(5) bond length is 1.83 Å. Both W(1)-O(1) bond lengths are 2.02 Å. Both W(1)-O(3) bond lengths are 1.91 Å. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted WO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra and  an edgeedge with one W(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. Both W(2)-O(1) bond lengths are 1.99 Å. Both W(2)-O(2) bond lengths are 1.80 Å. Both W(2)-O(4) bond lengths are 2.22 Å. Ag(1) is bonded in a 4-coordinate geometry to one O(4), one O(5), and two equivalent O(3) atoms. The Ag(1)-O(4) bond length is 2.64 Å. The Ag(1)-O(5) bond length is 2.24 Å. Both Ag(1)-O(3) bond lengths are 2.62 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Eu(1), one W(1), and one Ag(1) atom. In the second O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Eu(1), one W(1), and one W(2) atom. In the third O site, O(2) is bonded in a bent 150 degrees geometry to one Eu(1) and one W(2) atom. In the fourth O site, O(3) is bonded to one Mg(1), one Eu(1), one W(1), and one Ag(1) atom to form distorted OEuMgAgW trigonal pyramids that share  a cornercorner with one O(3)EuMgAgW trigonal pyramid, edges with two equivalent O(4)MgAgW3 trigonal bipyramids,  an edgeedge with one O(3)EuMgAgW trigonal pyramid, and  a faceface with one O(3)EuMgAgW trigonal pyramid. In the fifth O site, O(4) is bonded to one Mg(1), one W(1), two equivalent W(2), and one Ag(1) atom to form distorted OMgAgW3 trigonal bipyramids that share  a cornercorner with one O(4)MgAgW3 trigonal bipyramid,  an edgeedge with one O(4)MgAgW3 trigonal bipyramid, and edges with four equivalent O(3)EuMgAgW trigonal pyramids.