MgV4TlO10 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(3), one O(6), one O(7), and two equivalent O(8) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one V(1)O5 trigonal bipyramid, corners with two equivalent Mg(1)O5 trigonal bipyramids, and edges with two equivalent V(1)O5 trigonal bipyramids. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(3), one O(8), one O(9), and two equivalent O(6) atoms to form distorted VO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent V(1)O5 trigonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. In the second V site, V(2) is bonded in a 5-coordinate geometry to one O(10), one O(4), one O(5), and two equivalent O(7) atoms. In the third V site, V(3) is bonded in a 5-coordinate geometry to one O(2), one O(6), one O(8), and two equivalent O(3) atoms. In the fourth V site, V(4) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(7), and two equivalent O(4) atoms. Tl(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(9) atoms. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one V(4) and two equivalent Tl(1) atoms. In the second O site, O(2) is bonded in a single-bond geometry to one V(3) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one V(1), and two equivalent V(3) atoms. In the fourth O site, O(4) is bonded in a T-shaped geometry to one V(2) and two equivalent V(4) atoms. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one V(2) and one V(4) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(1), one V(3), and two equivalent V(1) atoms. In the seventh O site, O(7) is bonded to one Mg(1), one V(4), and two equivalent V(2) atoms to form corner-sharing OMgV3 tetrahedra. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to two equivalent Mg(1), one V(1), and one V(3) atom. In the ninth O site, O(9) is bonded in a single-bond geometry to one V(1) and two equivalent Tl(1) atoms. In the tenth O site, O(10) is bonded in a single-bond geometry to one V(2) atom.
MgV4TlO10 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(3), one O(6), one O(7), and two equivalent O(8) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one V(1)O5 trigonal bipyramid, corners with two equivalent Mg(1)O5 trigonal bipyramids, and edges with two equivalent V(1)O5 trigonal bipyramids. The Mg(1)-O(3) bond length is 2.22 Å. The Mg(1)-O(6) bond length is 2.11 Å. The Mg(1)-O(7) bond length is 2.05 Å. Both Mg(1)-O(8) bond lengths are 2.01 Å. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(3), one O(8), one O(9), and two equivalent O(6) atoms to form distorted VO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent V(1)O5 trigonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The V(1)-O(3) bond length is 2.05 Å. The V(1)-O(8) bond length is 1.99 Å. The V(1)-O(9) bond length is 1.65 Å. Both V(1)-O(6) bond lengths are 2.00 Å. In the second V site, V(2) is bonded in a 5-coordinate geometry to one O(10), one O(4), one O(5), and two equivalent O(7) atoms. The V(2)-O(10) bond length is 1.62 Å. The V(2)-O(4) bond length is 1.96 Å. The V(2)-O(5) bond length is 1.77 Å. Both V(2)-O(7) bond lengths are 2.02 Å. In the third V site, V(3) is bonded in a 5-coordinate geometry to one O(2), one O(6), one O(8), and two equivalent O(3) atoms. The V(3)-O(2) bond length is 1.63 Å. The V(3)-O(6) bond length is 2.06 Å. The V(3)-O(8) bond length is 1.99 Å. There is one shorter (2.01 Å) and one longer (2.02 Å) V(3)-O(3) bond length. In the fourth V site, V(4) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(7), and two equivalent O(4) atoms. The V(4)-O(1) bond length is 1.64 Å. The V(4)-O(5) bond length is 1.92 Å. The V(4)-O(7) bond length is 2.05 Å. Both V(4)-O(4) bond lengths are 2.02 Å. Tl(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(9) atoms. There is one shorter (2.92 Å) and one longer (2.94 Å) Tl(1)-O(1) bond length. There is one shorter (2.81 Å) and one longer (2.86 Å) Tl(1)-O(9) bond length. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one V(4) and two equivalent Tl(1) atoms. In the second O site, O(2) is bonded in a single-bond geometry to one V(3) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one V(1), and two equivalent V(3) atoms. In the fourth O site, O(4) is bonded in a T-shaped geometry to one V(2) and two equivalent V(4) atoms. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one V(2) and one V(4) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(1), one V(3), and two equivalent V(1) atoms. In the seventh O site, O(7) is bonded to one Mg(1), one V(4), and two equivalent V(2) atoms to form corner-sharing OMgV3 tetrahedra. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to two equivalent Mg(1), one V(1), and one V(3) atom. In the ninth O site, O(9) is bonded in a single-bond geometry to one V(1) and two equivalent Tl(1) atoms. In the tenth O site, O(10) is bonded in a single-bond geometry to one V(2) atom.