Co2Mo3O8 crystallizes in the hexagonal P6_3mc space group. Mo(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO6 octahedra that share corners with two equivalent Co(2)O6 octahedra, corners with three equivalent Co(1)O4 tetrahedra,  an edgeedge with one Co(2)O6 octahedra, and edges with four equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(4) and three equivalent O(2) atoms to form CoO4 tetrahedra that share corners with three equivalent Co(2)O6 octahedra and corners with nine equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-68°. In the second Co site, Co(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form CoO6 octahedra that share corners with six equivalent Mo(1)O6 octahedra, corners with three equivalent Co(1)O4 tetrahedra, and edges with three equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Mo(1) and one Co(2) atom. In the second O site, O(2) is bonded to two equivalent Mo(1), one Co(1), and one Co(2) atom to form OCo2Mo2 tetrahedra that share  a cornercorner with one O(4)CoMo3 tetrahedra, corners with two equivalent O(2)Co2Mo2 tetrahedra,  an edgeedge with one O(4)CoMo3 tetrahedra, and edges with two equivalent O(2)Co2Mo2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to three equivalent Mo(1) atoms. In the fourth O site, O(4) is bonded to three equivalent Mo(1) and one Co(1) atom to form a mixture of distorted edge and corner-sharing OCoMo3 tetrahedra.
Co2Mo3O8 crystallizes in the hexagonal P6_3mc space group. Mo(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO6 octahedra that share corners with two equivalent Co(2)O6 octahedra, corners with three equivalent Co(1)O4 tetrahedra,  an edgeedge with one Co(2)O6 octahedra, and edges with four equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. The Mo(1)-O(3) bond length is 2.06 Å. The Mo(1)-O(4) bond length is 2.18 Å. Both Mo(1)-O(1) bond lengths are 1.99 Å. Both Mo(1)-O(2) bond lengths are 2.11 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(4) and three equivalent O(2) atoms to form CoO4 tetrahedra that share corners with three equivalent Co(2)O6 octahedra and corners with nine equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-68°. The Co(1)-O(4) bond length is 1.97 Å. All Co(1)-O(2) bond lengths are 2.00 Å. In the second Co site, Co(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form CoO6 octahedra that share corners with six equivalent Mo(1)O6 octahedra, corners with three equivalent Co(1)O4 tetrahedra, and edges with three equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. All Co(2)-O(1) bond lengths are 2.05 Å. All Co(2)-O(2) bond lengths are 2.18 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Mo(1) and one Co(2) atom. In the second O site, O(2) is bonded to two equivalent Mo(1), one Co(1), and one Co(2) atom to form OCo2Mo2 tetrahedra that share  a cornercorner with one O(4)CoMo3 tetrahedra, corners with two equivalent O(2)Co2Mo2 tetrahedra,  an edgeedge with one O(4)CoMo3 tetrahedra, and edges with two equivalent O(2)Co2Mo2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to three equivalent Mo(1) atoms. In the fourth O site, O(4) is bonded to three equivalent Mo(1) and one Co(1) atom to form a mixture of distorted edge and corner-sharing OCoMo3 tetrahedra.