K3(NiO2)2 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to four equivalent O(1) 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 distorted 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 four equivalent O(1) atoms. O(1) is bonded in a 6-coordinate geometry to one K(1), three equivalent K(2), one Ni(1), and one Ni(2) atom.
K3(NiO2)2 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to four equivalent O(1) atoms. All K(1)-O(1) 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 2.73-2.91 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted square co-planar geometry to four equivalent O(1) atoms. All Ni(1)-O(1) bond lengths are 1.90 Å. In the second Ni site, Ni(2) is bonded in a square co-planar geometry to four equivalent O(1) atoms. All Ni(2)-O(1) bond lengths are 1.85 Å. O(1) is bonded in a 6-coordinate geometry to one K(1), three equivalent K(2), one Ni(1), and one Ni(2) atom.