Ba2Mg2Tl2Sn3O10 crystallizes in the triclinic P1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 6-coordinate geometry to one O(6), one O(9), and four equivalent O(7) atoms. In the second Ba site, Ba(2) is bonded in a 5-coordinate geometry to one O(4) and four equivalent O(2) atoms. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(10), two equivalent O(1), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share corners with four equivalent Mg(1)O5 trigonal bipyramids and edges with four equivalent Sn(1)O5 trigonal bipyramids. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one O(10), one O(6), two equivalent O(5), and two equivalent O(8) atoms. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a distorted T-shaped geometry to one O(4) and two equivalent O(9) atoms. In the second Tl site, Tl(2) is bonded in a 3-coordinate geometry to one O(9) and two equivalent O(4) atoms. There are three inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one O(2), two equivalent O(1), and two equivalent O(3) atoms to form distorted SnO5 trigonal bipyramids that share corners with four equivalent Sn(1)O5 trigonal bipyramids and edges with four equivalent Mg(1)O5 trigonal bipyramids. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to one O(5), one O(7), two equivalent O(6), and two equivalent O(8) atoms. In the third Sn site, Sn(3) is bonded in a trigonal non-coplanar geometry to one O(5) and two equivalent O(10) atoms. There are ten inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1) and two equivalent Sn(1) atoms to form a mixture of distorted edge and corner-sharing OMg2Sn2 trigonal pyramids. In the second O site, O(2) is bonded in a 5-coordinate geometry to four equivalent Ba(2) and one Sn(1) atom. In the third O site, O(3) is bonded to two equivalent Mg(1) and two equivalent Sn(1) atoms to form a mixture of distorted edge and corner-sharing OMg2Sn2 trigonal pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ba(2), one Tl(1), and two equivalent Tl(2) atoms. In the fifth O site, O(5) is bonded to two equivalent Mg(2), one Sn(2), and one Sn(3) atom to form distorted OMg2Sn2 trigonal pyramids that share  a cornercorner with one O(7)Ba4Sn trigonal bipyramid and corners with two equivalent O(5)Mg2Sn2 trigonal pyramids. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ba(1), one Mg(2), and two equivalent Sn(2) atoms. In the seventh O site, O(7) is bonded to four equivalent Ba(1) and one Sn(2) atom to form distorted OBa4Sn trigonal bipyramids that share corners with four equivalent O(7)Ba4Sn trigonal bipyramids,  a cornercorner with one O(5)Mg2Sn2 trigonal pyramid, and edges with four equivalent O(7)Ba4Sn trigonal bipyramids. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to two equivalent Mg(2) and two equivalent Sn(2) atoms. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Ba(1), one Tl(2), and two equivalent Tl(1) atoms. In the tenth O site, O(10) is bonded in a distorted see-saw-like geometry to one Mg(1), one Mg(2), and two equivalent Sn(3) atoms.
Ba2Mg2Tl2Sn3O10 crystallizes in the triclinic P1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 6-coordinate geometry to one O(6), one O(9), and four equivalent O(7) atoms. The Ba(1)-O(6) bond length is 3.00 Å. The Ba(1)-O(9) bond length is 2.57 Å. There are a spread of Ba(1)-O(7) bond distances ranging from 2.83-2.96 Å. In the second Ba site, Ba(2) is bonded in a 5-coordinate geometry to one O(4) and four equivalent O(2) atoms. The Ba(2)-O(4) bond length is 2.35 Å. There are a spread of Ba(2)-O(2) bond distances ranging from 2.93-3.05 Å. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(10), two equivalent O(1), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share corners with four equivalent Mg(1)O5 trigonal bipyramids and edges with four equivalent Sn(1)O5 trigonal bipyramids. The Mg(1)-O(10) bond length is 2.08 Å. There is one shorter (2.18 Å) and one longer (2.20 Å) Mg(1)-O(1) bond length. Both Mg(1)-O(3) bond lengths are 2.16 Å. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one O(10), one O(6), two equivalent O(5), and two equivalent O(8) atoms. The Mg(2)-O(10) bond length is 2.16 Å. The Mg(2)-O(6) bond length is 2.21 Å. There is one shorter (2.17 Å) and one longer (2.30 Å) Mg(2)-O(5) bond length. There is one shorter (2.14 Å) and one longer (2.41 Å) Mg(2)-O(8) bond length. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a distorted T-shaped geometry to one O(4) and two equivalent O(9) atoms. The Tl(1)-O(4) bond length is 2.40 Å. There is one shorter (2.52 Å) and one longer (2.64 Å) Tl(1)-O(9) bond length. In the second Tl site, Tl(2) is bonded in a 3-coordinate geometry to one O(9) and two equivalent O(4) atoms. The Tl(2)-O(9) bond length is 2.37 Å. There is one shorter (2.61 Å) and one longer (2.71 Å) Tl(2)-O(4) bond length. There are three inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one O(2), two equivalent O(1), and two equivalent O(3) atoms to form distorted SnO5 trigonal bipyramids that share corners with four equivalent Sn(1)O5 trigonal bipyramids and edges with four equivalent Mg(1)O5 trigonal bipyramids. The Sn(1)-O(2) bond length is 2.00 Å. Both Sn(1)-O(1) bond lengths are 2.12 Å. There is one shorter (2.14 Å) and one longer (2.15 Å) Sn(1)-O(3) bond length. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to one O(5), one O(7), two equivalent O(6), and two equivalent O(8) atoms. The Sn(2)-O(5) bond length is 2.35 Å. The Sn(2)-O(7) bond length is 2.03 Å. There is one shorter (2.06 Å) and one longer (2.07 Å) Sn(2)-O(6) bond length. There is one shorter (2.07 Å) and one longer (2.13 Å) Sn(2)-O(8) bond length. In the third Sn site, Sn(3) is bonded in a trigonal non-coplanar geometry to one O(5) and two equivalent O(10) atoms. The Sn(3)-O(5) bond length is 2.01 Å. There is one shorter (2.29 Å) and one longer (2.35 Å) Sn(3)-O(10) bond length. There are ten inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1) and two equivalent Sn(1) atoms to form a mixture of distorted edge and corner-sharing OMg2Sn2 trigonal pyramids. In the second O site, O(2) is bonded in a 5-coordinate geometry to four equivalent Ba(2) and one Sn(1) atom. In the third O site, O(3) is bonded to two equivalent Mg(1) and two equivalent Sn(1) atoms to form a mixture of distorted edge and corner-sharing OMg2Sn2 trigonal pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ba(2), one Tl(1), and two equivalent Tl(2) atoms. In the fifth O site, O(5) is bonded to two equivalent Mg(2), one Sn(2), and one Sn(3) atom to form distorted OMg2Sn2 trigonal pyramids that share  a cornercorner with one O(7)Ba4Sn trigonal bipyramid and corners with two equivalent O(5)Mg2Sn2 trigonal pyramids. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ba(1), one Mg(2), and two equivalent Sn(2) atoms. In the seventh O site, O(7) is bonded to four equivalent Ba(1) and one Sn(2) atom to form distorted OBa4Sn trigonal bipyramids that share corners with four equivalent O(7)Ba4Sn trigonal bipyramids,  a cornercorner with one O(5)Mg2Sn2 trigonal pyramid, and edges with four equivalent O(7)Ba4Sn trigonal bipyramids. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to two equivalent Mg(2) and two equivalent Sn(2) atoms. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Ba(1), one Tl(2), and two equivalent Tl(1) atoms. In the tenth O site, O(10) is bonded in a distorted see-saw-like geometry to one Mg(1), one Mg(2), and two equivalent Sn(3) atoms.