MgNbTlOBr4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one Tl(1), one Br(1), two equivalent Br(2), and two equivalent Br(3) atoms. Nb(1) is bonded to two equivalent O(1), one Br(1), one Br(2), one Br(3), and one Br(4) atom to form distorted corner-sharing NbBr4O2 octahedra. The corner-sharing octahedral tilt angles are 6°. Tl(1) is bonded in a 5-coordinate geometry to one Mg(1), two equivalent Br(1), and two equivalent Br(4) atoms. O(1) is bonded in a linear geometry to two equivalent Nb(1) atoms. There are four inequivalent Br sites. In the first Br site, Br(1) is bonded in a 4-coordinate geometry to one Mg(1), one Nb(1), and two equivalent Tl(1) atoms. In the second Br site, Br(2) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Nb(1) atom. In the third Br site, Br(3) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Nb(1) atom. In the fourth Br site, Br(4) is bonded in a distorted T-shaped geometry to one Nb(1) and two equivalent Tl(1) atoms.
MgNbTlOBr4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one Tl(1), one Br(1), two equivalent Br(2), and two equivalent Br(3) atoms. The Mg(1)-Tl(1) bond length is 3.25 Å. The Mg(1)-Br(1) bond length is 2.60 Å. There is one shorter (2.70 Å) and one longer (2.72 Å) Mg(1)-Br(2) bond length. There is one shorter (2.76 Å) and one longer (2.77 Å) Mg(1)-Br(3) bond length. Nb(1) is bonded to two equivalent O(1), one Br(1), one Br(2), one Br(3), and one Br(4) atom to form distorted corner-sharing NbBr4O2 octahedra. The corner-sharing octahedral tilt angles are 6°. Both Nb(1)-O(1) bond lengths are 1.99 Å. The Nb(1)-Br(1) bond length is 2.76 Å. The Nb(1)-Br(2) bond length is 2.93 Å. The Nb(1)-Br(3) bond length is 2.88 Å. The Nb(1)-Br(4) bond length is 2.68 Å. Tl(1) is bonded in a 5-coordinate geometry to one Mg(1), two equivalent Br(1), and two equivalent Br(4) atoms. There is one shorter (3.28 Å) and one longer (3.29 Å) Tl(1)-Br(1) bond length. There is one shorter (3.03 Å) and one longer (3.04 Å) Tl(1)-Br(4) bond length. O(1) is bonded in a linear geometry to two equivalent Nb(1) atoms. There are four inequivalent Br sites. In the first Br site, Br(1) is bonded in a 4-coordinate geometry to one Mg(1), one Nb(1), and two equivalent Tl(1) atoms. In the second Br site, Br(2) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Nb(1) atom. In the third Br site, Br(3) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Nb(1) atom. In the fourth Br site, Br(4) is bonded in a distorted T-shaped geometry to one Nb(1) and two equivalent Tl(1) atoms.