MgTb2W2(O4Cl)2 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent Cl(1) atoms to form distorted MgCl2O4 octahedra that share edges with two equivalent W(1)O4 trigonal pyramids. Tb(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and one Cl(1) atom. W(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted WO4 trigonal pyramids that share  an edgeedge with one Mg(1)Cl2O4 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Tb(1) and one W(1) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Tb(1), and one W(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to two equivalent Tb(1) and one W(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Tb(1), and one W(1) atom to form distorted corner-sharing OTb2MgW tetrahedra. Cl(1) is bonded in a 2-coordinate geometry to one Mg(1) and one Tb(1) atom.
MgTb2W2(O4Cl)2 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent Cl(1) atoms to form distorted MgCl2O4 octahedra that share edges with two equivalent W(1)O4 trigonal pyramids. Both Mg(1)-O(2) bond lengths are 2.18 Å. Both Mg(1)-O(4) bond lengths are 2.12 Å. Both Mg(1)-Cl(1) bond lengths are 2.48 Å. Tb(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and one Cl(1) atom. The Tb(1)-O(1) bond length is 2.25 Å. The Tb(1)-O(2) bond length is 2.26 Å. There is one shorter (2.30 Å) and one longer (2.47 Å) Tb(1)-O(3) bond length. There is one shorter (2.29 Å) and one longer (2.48 Å) Tb(1)-O(4) bond length. The Tb(1)-Cl(1) bond length is 2.94 Å. W(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted WO4 trigonal pyramids that share  an edgeedge with one Mg(1)Cl2O4 octahedra. The W(1)-O(1) bond length is 1.83 Å. The W(1)-O(2) bond length is 1.88 Å. The W(1)-O(3) bond length is 1.88 Å. The W(1)-O(4) bond length is 1.99 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Tb(1) and one W(1) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Tb(1), and one W(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to two equivalent Tb(1) and one W(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Tb(1), and one W(1) atom to form distorted corner-sharing OTb2MgW tetrahedra. Cl(1) is bonded in a 2-coordinate geometry to one Mg(1) and one Tb(1) atom.