Co15O28 crystallizes in the triclinic P-1 space group. There are nine inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(3), one O(5), one O(8), and two equivalent O(12) atoms to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. In the second Co site, Co(2) is bonded to one O(11), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. In the third Co site, Co(3) is bonded to one O(1), one O(10), one O(12), one O(4), one O(5), and one O(6) atom to form edge-sharing CoO6 octahedra. In the fourth Co site, Co(4) is bonded to one O(10), one O(13), one O(14), one O(4), one O(7), and one O(9) atom to form edge-sharing CoO6 octahedra. In the fifth Co site, Co(5) is bonded to one O(11), one O(13), one O(14), one O(3), one O(5), and one O(6) atom to form edge-sharing CoO6 octahedra. In the sixth Co site, Co(6) is bonded to one O(1), one O(10), one O(7), one O(8), and two equivalent O(2) atoms to form edge-sharing CoO6 octahedra. In the seventh Co site, Co(7) is bonded to two equivalent O(13), two equivalent O(4), and two equivalent O(6) atoms to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. In the eighth Co site, Co(8) is bonded to two equivalent O(11), two equivalent O(14), and two equivalent O(9) atoms to form edge-sharing CoO6 octahedra. In the ninth Co site, Co(9) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Co(1), one Co(3), one Co(6), and one Co(9) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Co(2) and two equivalent Co(6) atoms. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Co(1), one Co(2), and one Co(5) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Co(3), one Co(4), one Co(7), and one Co(9) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Co(1), one Co(3), and one Co(5) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Co(3), one Co(5), and one Co(7) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Co(2), one Co(4), one Co(6), and one Co(9) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Co(1), one Co(2), and one Co(6) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(4), and one Co(8) atom. In the tenth O site, O(10) is bonded in a distorted T-shaped geometry to one Co(3), one Co(4), and one Co(6) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(5), and one Co(8) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Co(3) and two equivalent Co(1) atoms. In the thirteenth O site, O(13) is bonded in a distorted trigonal non-coplanar geometry to one Co(4), one Co(5), and one Co(7) atom. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Co(4), one Co(5), and one Co(8) atom.
Co15O28 crystallizes in the triclinic P-1 space group. There are nine inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(3), one O(5), one O(8), and two equivalent O(12) atoms to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. The Co(1)-O(1) bond length is 1.96 Å. The Co(1)-O(3) bond length is 1.88 Å. The Co(1)-O(5) bond length is 1.87 Å. The Co(1)-O(8) bond length is 1.88 Å. There is one shorter (1.89 Å) and one longer (1.90 Å) Co(1)-O(12) bond length. In the second Co site, Co(2) is bonded to one O(11), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. The Co(2)-O(11) bond length is 1.91 Å. The Co(2)-O(2) bond length is 1.85 Å. The Co(2)-O(3) bond length is 1.88 Å. The Co(2)-O(7) bond length is 1.97 Å. The Co(2)-O(8) bond length is 1.87 Å. The Co(2)-O(9) bond length is 1.90 Å. In the third Co site, Co(3) is bonded to one O(1), one O(10), one O(12), one O(4), one O(5), and one O(6) atom to form edge-sharing CoO6 octahedra. The Co(3)-O(1) bond length is 1.89 Å. The Co(3)-O(10) bond length is 1.87 Å. The Co(3)-O(12) bond length is 1.87 Å. The Co(3)-O(4) bond length is 1.91 Å. The Co(3)-O(5) bond length is 1.91 Å. The Co(3)-O(6) bond length is 1.87 Å. In the fourth Co site, Co(4) is bonded to one O(10), one O(13), one O(14), one O(4), one O(7), and one O(9) atom to form edge-sharing CoO6 octahedra. The Co(4)-O(10) bond length is 1.87 Å. The Co(4)-O(13) bond length is 1.88 Å. The Co(4)-O(14) bond length is 1.90 Å. The Co(4)-O(4) bond length is 1.92 Å. The Co(4)-O(7) bond length is 1.90 Å. The Co(4)-O(9) bond length is 1.86 Å. In the fifth Co site, Co(5) is bonded to one O(11), one O(13), one O(14), one O(3), one O(5), and one O(6) atom to form edge-sharing CoO6 octahedra. The Co(5)-O(11) bond length is 1.87 Å. The Co(5)-O(13) bond length is 1.90 Å. The Co(5)-O(14) bond length is 1.89 Å. The Co(5)-O(3) bond length is 1.89 Å. The Co(5)-O(5) bond length is 1.89 Å. The Co(5)-O(6) bond length is 1.90 Å. In the sixth Co site, Co(6) is bonded to one O(1), one O(10), one O(7), one O(8), and two equivalent O(2) atoms to form edge-sharing CoO6 octahedra. The Co(6)-O(1) bond length is 1.92 Å. The Co(6)-O(10) bond length is 1.91 Å. The Co(6)-O(7) bond length is 1.92 Å. The Co(6)-O(8) bond length is 1.88 Å. There is one shorter (1.87 Å) and one longer (1.89 Å) Co(6)-O(2) bond length. In the seventh Co site, Co(7) is bonded to two equivalent O(13), two equivalent O(4), and two equivalent O(6) atoms to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. Both Co(7)-O(13) bond lengths are 1.87 Å. Both Co(7)-O(4) bond lengths are 1.98 Å. Both Co(7)-O(6) bond lengths are 1.88 Å. In the eighth Co site, Co(8) is bonded to two equivalent O(11), two equivalent O(14), and two equivalent O(9) atoms to form edge-sharing CoO6 octahedra. Both Co(8)-O(11) bond lengths are 1.89 Å. Both Co(8)-O(14) bond lengths are 1.89 Å. Both Co(8)-O(9) bond lengths are 1.89 Å. In the ninth Co site, Co(9) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles are 13°. Both Co(9)-O(1) bond lengths are 2.13 Å. Both Co(9)-O(4) bond lengths are 2.12 Å. Both Co(9)-O(7) bond lengths are 2.12 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Co(1), one Co(3), one Co(6), and one Co(9) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Co(2) and two equivalent Co(6) atoms. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Co(1), one Co(2), and one Co(5) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Co(3), one Co(4), one Co(7), and one Co(9) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Co(1), one Co(3), and one Co(5) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Co(3), one Co(5), and one Co(7) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Co(2), one Co(4), one Co(6), and one Co(9) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Co(1), one Co(2), and one Co(6) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(4), and one Co(8) atom. In the tenth O site, O(10) is bonded in a distorted T-shaped geometry to one Co(3), one Co(4), and one Co(6) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(5), and one Co(8) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Co(3) and two equivalent Co(1) atoms. In the thirteenth O site, O(13) is bonded in a distorted trigonal non-coplanar geometry to one Co(4), one Co(5), and one Co(7) atom. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Co(4), one Co(5), and one Co(8) atom.