Ba3Mo2(O9I)2 crystallizes in the orthorhombic Fdd2 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(5), and four equivalent O(8) atoms to form BaO12 cuboctahedra that share edges with two equivalent Ba(1)O12 cuboctahedra and edges with two equivalent I(1)O6 octahedra. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to one O(1), one O(3), one O(4), two equivalent O(6), two equivalent O(9), and three equivalent O(7) atoms. Mo(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(9) atom. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(2), one Mo(1), and one I(1) atom. In the second O site, O(4) is bonded in a 3-coordinate geometry to one Ba(2), one Mo(1), and one I(1) atom. In the third O site, O(5) is bonded in a distorted water-like geometry to one Ba(1), one Mo(1), and one I(1) atom. In the fourth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Ba(2) and one I(1) atom. In the fifth O site, O(7) is bonded in a distorted single-bond geometry to three equivalent Ba(2) and one I(1) atom. In the sixth O site, O(8) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1) atoms. In the seventh O site, O(1) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one Mo(1) atom. In the eighth O site, O(9) is bonded in a 4-coordinate geometry to two equivalent Ba(2), one Mo(1), and one I(1) atom. In the ninth O site, O(2) is bonded in a distorted single-bond geometry to one Ba(1) and one Mo(1) atom. I(1) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(9) atom to form IO6 octahedra that share  an edgeedge with one Ba(1)O12 cuboctahedra.
Ba3Mo2(O9I)2 crystallizes in the orthorhombic Fdd2 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(5), and four equivalent O(8) atoms to form BaO12 cuboctahedra that share edges with two equivalent Ba(1)O12 cuboctahedra and edges with two equivalent I(1)O6 octahedra. Both Ba(1)-O(1) bond lengths are 3.28 Å. Both Ba(1)-O(2) bond lengths are 2.88 Å. Both Ba(1)-O(3) bond lengths are 2.98 Å. Both Ba(1)-O(5) bond lengths are 3.06 Å. There are two shorter (2.74 Å) and two longer (2.76 Å) Ba(1)-O(8) bond lengths. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to one O(1), one O(3), one O(4), two equivalent O(6), two equivalent O(9), and three equivalent O(7) atoms. The Ba(2)-O(1) bond length is 2.77 Å. The Ba(2)-O(3) bond length is 2.89 Å. The Ba(2)-O(4) bond length is 2.89 Å. There is one shorter (2.78 Å) and one longer (3.02 Å) Ba(2)-O(6) bond length. There is one shorter (2.86 Å) and one longer (3.04 Å) Ba(2)-O(9) bond length. There are a spread of Ba(2)-O(7) bond distances ranging from 3.04-3.26 Å. Mo(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(9) atom. The Mo(1)-O(1) bond length is 1.76 Å. The Mo(1)-O(2) bond length is 1.73 Å. The Mo(1)-O(3) bond length is 2.28 Å. The Mo(1)-O(4) bond length is 2.00 Å. The Mo(1)-O(5) bond length is 1.99 Å. The Mo(1)-O(9) bond length is 2.33 Å. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(2), one Mo(1), and one I(1) atom. The O(3)-I(1) bond length is 1.90 Å. In the second O site, O(4) is bonded in a 3-coordinate geometry to one Ba(2), one Mo(1), and one I(1) atom. The O(4)-I(1) bond length is 1.99 Å. In the third O site, O(5) is bonded in a distorted water-like geometry to one Ba(1), one Mo(1), and one I(1) atom. The O(5)-I(1) bond length is 2.00 Å. In the fourth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Ba(2) and one I(1) atom. The O(6)-I(1) bond length is 1.85 Å. In the fifth O site, O(7) is bonded in a distorted single-bond geometry to three equivalent Ba(2) and one I(1) atom. The O(7)-I(1) bond length is 1.84 Å. In the sixth O site, O(8) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1) atoms. In the seventh O site, O(1) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one Mo(1) atom. In the eighth O site, O(9) is bonded in a 4-coordinate geometry to two equivalent Ba(2), one Mo(1), and one I(1) atom. The O(9)-I(1) bond length is 1.90 Å. In the ninth O site, O(2) is bonded in a distorted single-bond geometry to one Ba(1) and one Mo(1) atom. I(1) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(9) atom to form IO6 octahedra that share  an edgeedge with one Ba(1)O12 cuboctahedra.