Sr2TlI5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to two equivalent I(2), two equivalent I(3), two equivalent I(4), and two equivalent I(5) atoms. In the second Sr site, Sr(2) is bonded to one I(2), one I(3), one I(4), two equivalent I(1), and two equivalent I(5) atoms to form distorted edge-sharing SrI7 pentagonal bipyramids. Tl(1) is bonded in a 1-coordinate geometry to two equivalent I(1) atoms. There are five inequivalent I sites. In the first I site, I(1) is bonded in a 4-coordinate geometry to two equivalent Sr(2) and two equivalent Tl(1) atoms. In the second I site, I(2) is bonded in a distorted T-shaped geometry to one Sr(2) and two equivalent Sr(1) atoms. In the third I site, I(3) is bonded in a distorted trigonal non-coplanar geometry to one Sr(2) and two equivalent Sr(1) atoms. In the fourth I site, I(4) is bonded in a distorted trigonal non-coplanar geometry to one Sr(2) and two equivalent Sr(1) atoms. In the fifth I site, I(5) is bonded to two equivalent Sr(1) and two equivalent Sr(2) atoms to form a mixture of distorted edge and corner-sharing ISr4 trigonal pyramids.
Sr2TlI5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to two equivalent I(2), two equivalent I(3), two equivalent I(4), and two equivalent I(5) atoms. There is one shorter (3.45 Å) and one longer (3.64 Å) Sr(1)-I(2) bond length. There is one shorter (3.40 Å) and one longer (3.49 Å) Sr(1)-I(3) bond length. There is one shorter (3.44 Å) and one longer (3.45 Å) Sr(1)-I(4) bond length. There is one shorter (3.46 Å) and one longer (3.52 Å) Sr(1)-I(5) bond length. In the second Sr site, Sr(2) is bonded to one I(2), one I(3), one I(4), two equivalent I(1), and two equivalent I(5) atoms to form distorted edge-sharing SrI7 pentagonal bipyramids. The Sr(2)-I(2) bond length is 3.38 Å. The Sr(2)-I(3) bond length is 3.39 Å. The Sr(2)-I(4) bond length is 3.49 Å. There is one shorter (3.25 Å) and one longer (3.36 Å) Sr(2)-I(1) bond length. There is one shorter (3.30 Å) and one longer (3.36 Å) Sr(2)-I(5) bond length. Tl(1) is bonded in a 1-coordinate geometry to two equivalent I(1) atoms. There is one shorter (3.44 Å) and one longer (3.58 Å) Tl(1)-I(1) bond length. There are five inequivalent I sites. In the first I site, I(1) is bonded in a 4-coordinate geometry to two equivalent Sr(2) and two equivalent Tl(1) atoms. In the second I site, I(2) is bonded in a distorted T-shaped geometry to one Sr(2) and two equivalent Sr(1) atoms. In the third I site, I(3) is bonded in a distorted trigonal non-coplanar geometry to one Sr(2) and two equivalent Sr(1) atoms. In the fourth I site, I(4) is bonded in a distorted trigonal non-coplanar geometry to one Sr(2) and two equivalent Sr(1) atoms. In the fifth I site, I(5) is bonded to two equivalent Sr(1) and two equivalent Sr(2) atoms to form a mixture of distorted edge and corner-sharing ISr4 trigonal pyramids.