BaSr2I6 crystallizes in the monoclinic P2_1/c space group. Ba(1) is bonded in a 8-coordinate geometry to one I(2), one I(3), one I(4), one I(5), two equivalent I(1), and two equivalent I(6) atoms. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one I(1), one I(2), one I(4), one I(5), one I(6), and two equivalent I(3) atoms. In the second Sr site, Sr(2) is bonded to one I(3), one I(4), one I(5), one I(6), and two equivalent I(2) atoms to form distorted corner-sharing SrI6 pentagonal pyramids. There are six inequivalent I sites. In the first I site, I(1) is bonded in a trigonal non-coplanar geometry to two equivalent Ba(1) and one Sr(1) atom. In the second I site, I(2) is bonded to one Ba(1), one Sr(1), and two equivalent Sr(2) atoms to form distorted corner-sharing IBaSr3 trigonal pyramids. In the third I site, I(3) is bonded to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms to form a mixture of corner and edge-sharing IBaSr3 trigonal pyramids. In the fourth I site, I(4) is bonded in a distorted trigonal planar geometry to one Ba(1), one Sr(1), and one Sr(2) atom. In the fifth I site, I(5) is bonded in a distorted trigonal non-coplanar geometry to one Ba(1), one Sr(1), and one Sr(2) atom. In the sixth I site, I(6) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Sr(1), and one Sr(2) atom.
BaSr2I6 crystallizes in the monoclinic P2_1/c space group. Ba(1) is bonded in a 8-coordinate geometry to one I(2), one I(3), one I(4), one I(5), two equivalent I(1), and two equivalent I(6) atoms. The Ba(1)-I(2) bond length is 3.58 Å. The Ba(1)-I(3) bond length is 3.63 Å. The Ba(1)-I(4) bond length is 3.51 Å. The Ba(1)-I(5) bond length is 3.59 Å. There is one shorter (3.49 Å) and one longer (3.55 Å) Ba(1)-I(1) bond length. There is one shorter (3.66 Å) and one longer (4.00 Å) Ba(1)-I(6) bond length. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one I(1), one I(2), one I(4), one I(5), one I(6), and two equivalent I(3) atoms. The Sr(1)-I(1) bond length is 3.33 Å. The Sr(1)-I(2) bond length is 3.54 Å. The Sr(1)-I(4) bond length is 3.36 Å. The Sr(1)-I(5) bond length is 3.41 Å. The Sr(1)-I(6) bond length is 3.58 Å. There is one shorter (3.56 Å) and one longer (3.57 Å) Sr(1)-I(3) bond length. In the second Sr site, Sr(2) is bonded to one I(3), one I(4), one I(5), one I(6), and two equivalent I(2) atoms to form distorted corner-sharing SrI6 pentagonal pyramids. The Sr(2)-I(3) bond length is 3.76 Å. The Sr(2)-I(4) bond length is 3.26 Å. The Sr(2)-I(5) bond length is 3.22 Å. The Sr(2)-I(6) bond length is 3.26 Å. There is one shorter (3.34 Å) and one longer (3.51 Å) Sr(2)-I(2) bond length. There are six inequivalent I sites. In the first I site, I(1) is bonded in a trigonal non-coplanar geometry to two equivalent Ba(1) and one Sr(1) atom. In the second I site, I(2) is bonded to one Ba(1), one Sr(1), and two equivalent Sr(2) atoms to form distorted corner-sharing IBaSr3 trigonal pyramids. In the third I site, I(3) is bonded to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms to form a mixture of corner and edge-sharing IBaSr3 trigonal pyramids. In the fourth I site, I(4) is bonded in a distorted trigonal planar geometry to one Ba(1), one Sr(1), and one Sr(2) atom. In the fifth I site, I(5) is bonded in a distorted trigonal non-coplanar geometry to one Ba(1), one Sr(1), and one Sr(2) atom. In the sixth I site, I(6) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Sr(1), and one Sr(2) atom.