K4(NiO2)3 crystallizes in the monoclinic C2/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(2) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a square co-planar geometry to four equivalent O(1) atoms. In the second Ni site, Ni(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one K(1), three equivalent K(2), one Ni(1), and one Ni(2) atom to form a mixture of distorted edge, corner, and face-sharing OK4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-71°. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent K(1) and two equivalent Ni(2) atoms.
K4(NiO2)3 crystallizes in the monoclinic C2/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(2) atoms. Both K(1)-O(1) bond lengths are 2.66 Å. Both K(1)-O(2) bond lengths are 2.64 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. There are a spread of K(2)-O(1) bond distances ranging from 2.69-2.87 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a square co-planar geometry to four equivalent O(1) atoms. All Ni(1)-O(1) bond lengths are 1.83 Å. In the second Ni site, Ni(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. Both Ni(2)-O(1) bond lengths are 1.83 Å. Both Ni(2)-O(2) bond lengths are 1.82 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one K(1), three equivalent K(2), one Ni(1), and one Ni(2) atom to form a mixture of distorted edge, corner, and face-sharing OK4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 0-71°. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent K(1) and two equivalent Ni(2) atoms.