Sr2NiSe2(O3Cl)2 crystallizes in the monoclinic P2_1/c space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and three equivalent Cl(1) atoms. Ni(1) is bonded in an octahedral geometry to two equivalent O(1), two equivalent O(2), and two equivalent Cl(1) atoms. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), one Ni(1), and one Se(1) atom to form distorted corner-sharing OSr2NiSe tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Sr(1), one Ni(1), and one Se(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Sr(1) and one Se(1) atom. Cl(1) is bonded in a 4-coordinate geometry to three equivalent Sr(1) and one Ni(1) atom.
Sr2NiSe2(O3Cl)2 crystallizes in the monoclinic P2_1/c space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and three equivalent Cl(1) atoms. There is one shorter (2.57 Å) and one longer (2.87 Å) Sr(1)-O(1) bond length. There is one shorter (2.66 Å) and one longer (2.76 Å) Sr(1)-O(2) bond length. There is one shorter (2.52 Å) and one longer (2.63 Å) Sr(1)-O(3) bond length. There are a spread of Sr(1)-Cl(1) bond distances ranging from 3.03-3.38 Å. Ni(1) is bonded in an octahedral geometry to two equivalent O(1), two equivalent O(2), and two equivalent Cl(1) atoms. Both Ni(1)-O(1) bond lengths are 2.07 Å. Both Ni(1)-O(2) bond lengths are 2.06 Å. Both Ni(1)-Cl(1) bond lengths are 2.43 Å. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.72 Å. The Se(1)-O(2) bond length is 1.73 Å. The Se(1)-O(3) bond length is 1.68 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), one Ni(1), and one Se(1) atom to form distorted corner-sharing OSr2NiSe tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Sr(1), one Ni(1), and one Se(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Sr(1) and one Se(1) atom. Cl(1) is bonded in a 4-coordinate geometry to three equivalent Sr(1) and one Ni(1) atom.