Co2C2O7 crystallizes in the trigonal P321 space group. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1) and three equivalent O(2) atoms to form corner-sharing CoO4 tetrahedra. In the second Co site, Co(2) is bonded to one O(5) and three equivalent O(4) atoms to form corner-sharing CoO4 tetrahedra. In the third Co site, Co(3) is bonded to one O(5) and three equivalent O(3) atoms to form corner-sharing CoO4 tetrahedra. C(1) is bonded in a trigonal planar geometry to one O(2), one O(3), and one O(4) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Co(1) atoms. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Co(1) and one C(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Co(3) and one C(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Co(2) and one C(1) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Co(2) and one Co(3) atom.
Co2C2O7 crystallizes in the trigonal P321 space group. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1) and three equivalent O(2) atoms to form corner-sharing CoO4 tetrahedra. The Co(1)-O(1) bond length is 1.78 Å. All Co(1)-O(2) bond lengths are 1.88 Å. In the second Co site, Co(2) is bonded to one O(5) and three equivalent O(4) atoms to form corner-sharing CoO4 tetrahedra. The Co(2)-O(5) bond length is 1.78 Å. All Co(2)-O(4) bond lengths are 1.92 Å. In the third Co site, Co(3) is bonded to one O(5) and three equivalent O(3) atoms to form corner-sharing CoO4 tetrahedra. The Co(3)-O(5) bond length is 1.80 Å. All Co(3)-O(3) bond lengths are 1.92 Å. C(1) is bonded in a trigonal planar geometry to one O(2), one O(3), and one O(4) atom. The C(1)-O(2) bond length is 1.30 Å. The C(1)-O(3) bond length is 1.30 Å. The C(1)-O(4) bond length is 1.27 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Co(1) atoms. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Co(1) and one C(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Co(3) and one C(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Co(2) and one C(1) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Co(2) and one Co(3) atom.