MgTl4(NiO3)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 4-coordinate geometry to one O(11), one O(12), one O(3), one O(4), and one O(6) atom. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(10), one O(2), one O(5), one O(7), and one O(8) atom to form NiO5 trigonal bipyramids that share corners with four equivalent Ni(4)O6 octahedra and  a cornercorner with one Ni(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-48°. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(4), one O(6), and one O(8) atom to form corner-sharing NiO5 trigonal bipyramids. In the third Ni site, Ni(3) is bonded to one O(1), one O(12), one O(3), one O(4), and one O(9) atom to form NiO5 trigonal bipyramids that share  a cornercorner with one Ni(4)O6 octahedra and corners with three equivalent Ni(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 42°. In the fourth Ni site, Ni(4) is bonded to one O(10), one O(11), one O(2), one O(5), one O(7), and one O(9) atom to form corner-sharing NiO6 octahedra. There are four inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(2), one O(4), one O(5), and one O(6) atom. In the second Tl site, Tl(2) is bonded in a 6-coordinate geometry to one O(10), one O(12), one O(3), one O(7), one O(8), and one O(9) atom. In the third Tl site, Tl(3) is bonded in a 7-coordinate geometry to one O(10), one O(12), one O(2), one O(3), one O(7), one O(8), and one O(9) atom. In the fourth Tl site, Tl(4) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(2), one O(5), one O(6), and one O(7) atom. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ni(2), one Ni(3), one Tl(1), and one Tl(4) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ni(1), one Ni(4), one Tl(1), one Tl(3), and one Tl(4) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Mg(1), one Ni(2), one Ni(3), one Tl(2), and one Tl(3) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Ni(2), one Ni(3), and one Tl(1) atom to form distorted OMgTlNi2 tetrahedra that share  a cornercorner with one O(6)MgTl2Ni trigonal pyramid,  a cornercorner with one O(8)Tl2Ni2 trigonal pyramid,  a cornercorner with one O(9)Tl2Ni2 trigonal pyramid,  an edgeedge with one O(12)MgTl2Ni trigonal pyramid, and  an edgeedge with one O(6)MgTl2Ni trigonal pyramid. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ni(1), one Ni(4), one Tl(1), and one Tl(4) atom. In the sixth O site, O(6) is bonded to one Mg(1), one Ni(2), one Tl(1), and one Tl(4) atom to form OMgTl2Ni trigonal pyramids that share  a cornercorner with one O(4)MgTlNi2 tetrahedra,  a cornercorner with one O(12)MgTl2Ni trigonal pyramid,  a cornercorner with one O(8)Tl2Ni2 trigonal pyramid, and  an edgeedge with one O(4)MgTlNi2 tetrahedra. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ni(1), one Ni(4), one Tl(2), one Tl(3), and one Tl(4) atom. In the eighth O site, O(8) is bonded to one Ni(1), one Ni(2), one Tl(2), and one Tl(3) atom to form distorted OTl2Ni2 trigonal pyramids that share  a cornercorner with one O(4)MgTlNi2 tetrahedra,  a cornercorner with one O(6)MgTl2Ni trigonal pyramid, corners with two equivalent O(12)MgTl2Ni trigonal pyramids, corners with two equivalent O(9)Tl2Ni2 trigonal pyramids, and corners with three equivalent O(10)Tl2Ni2 trigonal pyramids. In the ninth O site, O(9) is bonded to one Ni(3), one Ni(4), one Tl(2), and one Tl(3) atom to form distorted OTl2Ni2 trigonal pyramids that share  a cornercorner with one O(4)MgTlNi2 tetrahedra,  a cornercorner with one O(12)MgTl2Ni trigonal pyramid,  a cornercorner with one O(10)Tl2Ni2 trigonal pyramid, corners with two equivalent O(8)Tl2Ni2 trigonal pyramids,  an edgeedge with one O(12)MgTl2Ni trigonal pyramid, and  an edgeedge with one O(10)Tl2Ni2 trigonal pyramid. In the tenth O site, O(10) is bonded to one Ni(1), one Ni(4), one Tl(2), and one Tl(3) atom to form distorted OTl2Ni2 trigonal pyramids that share  a cornercorner with one O(9)Tl2Ni2 trigonal pyramid, corners with three equivalent O(8)Tl2Ni2 trigonal pyramids,  an edgeedge with one O(12)MgTl2Ni trigonal pyramid, and  an edgeedge with one O(9)Tl2Ni2 trigonal pyramid. In the eleventh O site, O(11) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ni(4), one Tl(1), and one Tl(4) atom. In the twelfth O site, O(12) is bonded to one Mg(1), one Ni(3), one Tl(2), and one Tl(3) atom to form distorted OMgTl2Ni trigonal pyramids that share  a cornercorner with one O(6)MgTl2Ni trigonal pyramid,  a cornercorner with one O(9)Tl2Ni2 trigonal pyramid, corners with two equivalent O(8)Tl2Ni2 trigonal pyramids,  an edgeedge with one O(4)MgTlNi2 tetrahedra,  an edgeedge with one O(10)Tl2Ni2 trigonal pyramid, and  an edgeedge with one O(9)Tl2Ni2 trigonal pyramid.
MgTl4(NiO3)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 4-coordinate geometry to one O(11), one O(12), one O(3), one O(4), and one O(6) atom. The Mg(1)-O(11) bond length is 2.03 Å. The Mg(1)-O(12) bond length is 1.97 Å. The Mg(1)-O(3) bond length is 2.69 Å. The Mg(1)-O(4) bond length is 1.96 Å. The Mg(1)-O(6) bond length is 1.98 Å. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(10), one O(2), one O(5), one O(7), and one O(8) atom to form NiO5 trigonal bipyramids that share corners with four equivalent Ni(4)O6 octahedra and  a cornercorner with one Ni(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-48°. The Ni(1)-O(10) bond length is 1.98 Å. The Ni(1)-O(2) bond length is 2.01 Å. The Ni(1)-O(5) bond length is 1.95 Å. The Ni(1)-O(7) bond length is 1.96 Å. The Ni(1)-O(8) bond length is 2.16 Å. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(4), one O(6), and one O(8) atom to form corner-sharing NiO5 trigonal bipyramids. The Ni(2)-O(1) bond length is 2.05 Å. The Ni(2)-O(3) bond length is 2.12 Å. The Ni(2)-O(4) bond length is 2.07 Å. The Ni(2)-O(6) bond length is 2.02 Å. The Ni(2)-O(8) bond length is 2.05 Å. In the third Ni site, Ni(3) is bonded to one O(1), one O(12), one O(3), one O(4), and one O(9) atom to form NiO5 trigonal bipyramids that share  a cornercorner with one Ni(4)O6 octahedra and corners with three equivalent Ni(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 42°. The Ni(3)-O(1) bond length is 1.88 Å. The Ni(3)-O(12) bond length is 1.98 Å. The Ni(3)-O(3) bond length is 1.89 Å. The Ni(3)-O(4) bond length is 2.00 Å. The Ni(3)-O(9) bond length is 2.05 Å. In the fourth Ni site, Ni(4) is bonded to one O(10), one O(11), one O(2), one O(5), one O(7), and one O(9) atom to form corner-sharing NiO6 octahedra. The Ni(4)-O(10) bond length is 2.11 Å. The Ni(4)-O(11) bond length is 2.08 Å. The Ni(4)-O(2) bond length is 2.26 Å. The Ni(4)-O(5) bond length is 2.04 Å. The Ni(4)-O(7) bond length is 2.09 Å. The Ni(4)-O(9) bond length is 2.02 Å. There are four inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(2), one O(4), one O(5), and one O(6) atom. The Tl(1)-O(1) bond length is 2.68 Å. The Tl(1)-O(11) bond length is 2.26 Å. The Tl(1)-O(2) bond length is 2.19 Å. The Tl(1)-O(4) bond length is 2.24 Å. The Tl(1)-O(5) bond length is 2.53 Å. The Tl(1)-O(6) bond length is 2.34 Å. In the second Tl site, Tl(2) is bonded in a 6-coordinate geometry to one O(10), one O(12), one O(3), one O(7), one O(8), and one O(9) atom. The Tl(2)-O(10) bond length is 2.41 Å. The Tl(2)-O(12) bond length is 2.33 Å. The Tl(2)-O(3) bond length is 2.33 Å. The Tl(2)-O(7) bond length is 2.28 Å. The Tl(2)-O(8) bond length is 2.22 Å. The Tl(2)-O(9) bond length is 2.40 Å. In the third Tl site, Tl(3) is bonded in a 7-coordinate geometry to one O(10), one O(12), one O(2), one O(3), one O(7), one O(8), and one O(9) atom. The Tl(3)-O(10) bond length is 2.25 Å. The Tl(3)-O(12) bond length is 2.29 Å. The Tl(3)-O(2) bond length is 2.75 Å. The Tl(3)-O(3) bond length is 2.54 Å. The Tl(3)-O(7) bond length is 2.64 Å. The Tl(3)-O(8) bond length is 2.27 Å. The Tl(3)-O(9) bond length is 2.23 Å. In the fourth Tl site, Tl(4) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(2), one O(5), one O(6), and one O(7) atom. The Tl(4)-O(1) bond length is 2.51 Å. The Tl(4)-O(11) bond length is 2.21 Å. The Tl(4)-O(2) bond length is 2.28 Å. The Tl(4)-O(5) bond length is 2.27 Å. The Tl(4)-O(6) bond length is 2.22 Å. The Tl(4)-O(7) bond length is 2.47 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ni(2), one Ni(3), one Tl(1), and one Tl(4) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ni(1), one Ni(4), one Tl(1), one Tl(3), and one Tl(4) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Mg(1), one Ni(2), one Ni(3), one Tl(2), and one Tl(3) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Ni(2), one Ni(3), and one Tl(1) atom to form distorted OMgTlNi2 tetrahedra that share  a cornercorner with one O(6)MgTl2Ni trigonal pyramid,  a cornercorner with one O(8)Tl2Ni2 trigonal pyramid,  a cornercorner with one O(9)Tl2Ni2 trigonal pyramid,  an edgeedge with one O(12)MgTl2Ni trigonal pyramid, and  an edgeedge with one O(6)MgTl2Ni trigonal pyramid. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ni(1), one Ni(4), one Tl(1), and one Tl(4) atom. In the sixth O site, O(6) is bonded to one Mg(1), one Ni(2), one Tl(1), and one Tl(4) atom to form OMgTl2Ni trigonal pyramids that share  a cornercorner with one O(4)MgTlNi2 tetrahedra,  a cornercorner with one O(12)MgTl2Ni trigonal pyramid,  a cornercorner with one O(8)Tl2Ni2 trigonal pyramid, and  an edgeedge with one O(4)MgTlNi2 tetrahedra. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ni(1), one Ni(4), one Tl(2), one Tl(3), and one Tl(4) atom. In the eighth O site, O(8) is bonded to one Ni(1), one Ni(2), one Tl(2), and one Tl(3) atom to form distorted OTl2Ni2 trigonal pyramids that share  a cornercorner with one O(4)MgTlNi2 tetrahedra,  a cornercorner with one O(6)MgTl2Ni trigonal pyramid, corners with two equivalent O(12)MgTl2Ni trigonal pyramids, corners with two equivalent O(9)Tl2Ni2 trigonal pyramids, and corners with three equivalent O(10)Tl2Ni2 trigonal pyramids. In the ninth O site, O(9) is bonded to one Ni(3), one Ni(4), one Tl(2), and one Tl(3) atom to form distorted OTl2Ni2 trigonal pyramids that share  a cornercorner with one O(4)MgTlNi2 tetrahedra,  a cornercorner with one O(12)MgTl2Ni trigonal pyramid,  a cornercorner with one O(10)Tl2Ni2 trigonal pyramid, corners with two equivalent O(8)Tl2Ni2 trigonal pyramids,  an edgeedge with one O(12)MgTl2Ni trigonal pyramid, and  an edgeedge with one O(10)Tl2Ni2 trigonal pyramid. In the tenth O site, O(10) is bonded to one Ni(1), one Ni(4), one Tl(2), and one Tl(3) atom to form distorted OTl2Ni2 trigonal pyramids that share  a cornercorner with one O(9)Tl2Ni2 trigonal pyramid, corners with three equivalent O(8)Tl2Ni2 trigonal pyramids,  an edgeedge with one O(12)MgTl2Ni trigonal pyramid, and  an edgeedge with one O(9)Tl2Ni2 trigonal pyramid. In the eleventh O site, O(11) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ni(4), one Tl(1), and one Tl(4) atom. In the twelfth O site, O(12) is bonded to one Mg(1), one Ni(3), one Tl(2), and one Tl(3) atom to form distorted OMgTl2Ni trigonal pyramids that share  a cornercorner with one O(6)MgTl2Ni trigonal pyramid,  a cornercorner with one O(9)Tl2Ni2 trigonal pyramid, corners with two equivalent O(8)Tl2Ni2 trigonal pyramids,  an edgeedge with one O(4)MgTlNi2 tetrahedra,  an edgeedge with one O(10)Tl2Ni2 trigonal pyramid, and  an edgeedge with one O(9)Tl2Ni2 trigonal pyramid.