NiC2O4 crystallizes in the monoclinic P2_1/c space group. Ni(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 51°. C(1) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(2) atom. There are two inequivalent O sites. In the first O site, O(2) is bonded in a bent 120 degrees geometry to one Ni(1) and one C(1) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one C(1) atom.
NiC2O4 crystallizes in the monoclinic P2_1/c space group. Ni(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 51°. Both Ni(1)-O(2) bond lengths are 1.99 Å. There are two shorter (2.14 Å) and two longer (2.25 Å) Ni(1)-O(1) bond lengths. C(1) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(2) atom. The C(1)-O(1) bond length is 1.28 Å. The C(1)-O(2) bond length is 1.26 Å. There are two inequivalent O sites. In the first O site, O(2) is bonded in a bent 120 degrees geometry to one Ni(1) and one C(1) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one C(1) atom.