MgNb2(OI3)2 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent I(3) and four equivalent I(1) atoms to form edge-sharing MgI6 octahedra. Nb(1) is bonded in a distorted linear geometry to two equivalent O(1), one I(1), one I(3), and two equivalent I(2) atoms. O(1) is bonded in a linear geometry to two equivalent Nb(1) atoms. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Nb(1) atom. In the second I site, I(2) is bonded in an L-shaped geometry to two equivalent Nb(1) atoms. In the third I site, I(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one Nb(1) atom.
MgNb2(OI3)2 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent I(3) and four equivalent I(1) atoms to form edge-sharing MgI6 octahedra. Both Mg(1)-I(3) bond lengths are 2.93 Å. There are two shorter (2.92 Å) and two longer (2.93 Å) Mg(1)-I(1) bond lengths. Nb(1) is bonded in a distorted linear geometry to two equivalent O(1), one I(1), one I(3), and two equivalent I(2) atoms. There is one shorter (1.86 Å) and one longer (2.14 Å) Nb(1)-O(1) bond length. The Nb(1)-I(1) bond length is 3.04 Å. The Nb(1)-I(3) bond length is 2.80 Å. There is one shorter (2.82 Å) and one longer (2.92 Å) Nb(1)-I(2) bond length. O(1) is bonded in a linear geometry to two equivalent Nb(1) atoms. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Nb(1) atom. In the second I site, I(2) is bonded in an L-shaped geometry to two equivalent Nb(1) atoms. In the third I site, I(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one Nb(1) atom.