CoSeO5 crystallizes in the monoclinic C2/c space group. Co(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CoO6 octahedra that share corners with two equivalent Co(1)O6 octahedra and corners with four equivalent Se(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 28°. Se(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form SeO4 tetrahedra that share corners with four equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-56°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Co(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Co(1) atoms. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Co(1) and one Se(1) atom.
CoSeO5 crystallizes in the monoclinic C2/c space group. Co(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CoO6 octahedra that share corners with two equivalent Co(1)O6 octahedra and corners with four equivalent Se(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 28°. Both Co(1)-O(1) bond lengths are 2.02 Å. Both Co(1)-O(2) bond lengths are 1.81 Å. Both Co(1)-O(3) bond lengths are 2.03 Å. Se(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form SeO4 tetrahedra that share corners with four equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-56°. Both Se(1)-O(1) bond lengths are 1.68 Å. Both Se(1)-O(3) bond lengths are 1.69 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Co(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Co(1) atoms. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Co(1) and one Se(1) atom.