(Ni6Se4O15)2O2 crystallizes in the orthorhombic Cmc2_1 space group. The structure consists of four water atoms inside a Ni6Se4O15 framework. In the Ni6Se4O15 framework, there are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(6), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of face, corner, and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 29-59°. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), one O(5), one O(7), and two equivalent O(9) atoms to form a mixture of face, corner, and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 22-59°. In the third Ni site, Ni(3) is bonded to one O(1), one O(3), one O(5), one O(7), and two equivalent O(9) atoms to form a mixture of face, corner, and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 22-60°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(1) and two equivalent O(5) atoms. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(2), one O(3), and one O(4) atom. In the third Se site, Se(3) is bonded in a distorted T-shaped geometry to one O(6) and two equivalent O(7) atoms. There are nine inequivalent O sites. In the first O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to four equivalent Ni(1) atoms. In the second O site, O(9) is bonded in a rectangular see-saw-like geometry to two equivalent Ni(2) and two equivalent Ni(3) atoms. In the third O site, O(1) is bonded in a trigonal planar geometry to two equivalent Ni(3) and one Se(1) atom. In the fourth O site, O(2) is bonded in a trigonal planar geometry to one Ni(1), one Ni(2), and one Se(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one Se(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one Se(2) atom. In the seventh O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one Se(1) atom. In the eighth O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Ni(1) and one Se(3) atom. In the ninth O site, O(7) is bonded in a trigonal non-coplanar geometry to one Ni(2), one Ni(3), and one Se(3) atom.
(Ni6Se4O15)2O2 crystallizes in the orthorhombic Cmc2_1 space group. The structure consists of four water atoms inside a Ni6Se4O15 framework. In the Ni6Se4O15 framework, there are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(6), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of face, corner, and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 29-59°. The Ni(1)-O(2) bond length is 2.10 Å. The Ni(1)-O(6) bond length is 2.04 Å. There is one shorter (2.04 Å) and one longer (2.11 Å) Ni(1)-O(4) bond length. There is one shorter (2.05 Å) and one longer (2.10 Å) Ni(1)-O(8) bond length. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), one O(5), one O(7), and two equivalent O(9) atoms to form a mixture of face, corner, and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 22-59°. The Ni(2)-O(2) bond length is 2.08 Å. The Ni(2)-O(3) bond length is 2.04 Å. The Ni(2)-O(5) bond length is 2.13 Å. The Ni(2)-O(7) bond length is 2.04 Å. There is one shorter (2.06 Å) and one longer (2.08 Å) Ni(2)-O(9) bond length. In the third Ni site, Ni(3) is bonded to one O(1), one O(3), one O(5), one O(7), and two equivalent O(9) atoms to form a mixture of face, corner, and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 22-60°. The Ni(3)-O(1) bond length is 2.09 Å. The Ni(3)-O(3) bond length is 2.13 Å. The Ni(3)-O(5) bond length is 2.04 Å. The Ni(3)-O(7) bond length is 2.05 Å. There is one shorter (2.06 Å) and one longer (2.07 Å) Ni(3)-O(9) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(1) and two equivalent O(5) atoms. The Se(1)-O(1) bond length is 1.76 Å. Both Se(1)-O(5) bond lengths are 1.74 Å. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(2), one O(3), and one O(4) atom. The Se(2)-O(2) bond length is 1.76 Å. The Se(2)-O(3) bond length is 1.74 Å. The Se(2)-O(4) bond length is 1.74 Å. In the third Se site, Se(3) is bonded in a distorted T-shaped geometry to one O(6) and two equivalent O(7) atoms. The Se(3)-O(6) bond length is 1.74 Å. Both Se(3)-O(7) bond lengths are 1.74 Å. There are nine inequivalent O sites. In the first O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to four equivalent Ni(1) atoms. In the second O site, O(9) is bonded in a rectangular see-saw-like geometry to two equivalent Ni(2) and two equivalent Ni(3) atoms. In the third O site, O(1) is bonded in a trigonal planar geometry to two equivalent Ni(3) and one Se(1) atom. In the fourth O site, O(2) is bonded in a trigonal planar geometry to one Ni(1), one Ni(2), and one Se(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one Se(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one Se(2) atom. In the seventh O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one Se(1) atom. In the eighth O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Ni(1) and one Se(3) atom. In the ninth O site, O(7) is bonded in a trigonal non-coplanar geometry to one Ni(2), one Ni(3), and one Se(3) atom.