MgCo2(MoO4)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(2), one O(4), one O(5), one O(7), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with two equivalent Mo(2)O6 octahedra,  an edgeedge with one Mo(2)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, edges with two equivalent Mo(1)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-71°. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form distorted MoO6 octahedra that share corners with four equivalent Co(1)O6 octahedra, corners with four equivalent Co(2)O6 octahedra, edges with two equivalent Mo(2)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 32-63°. In the second Mo site, Mo(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted MoO6 octahedra that share corners with four equivalent Co(1)O6 octahedra, corners with four equivalent Co(2)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Mo(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-66°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form distorted CoO6 octahedra that share corners with four equivalent Mo(1)O6 octahedra, corners with four equivalent Mo(2)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, edges with two equivalent Co(2)O6 octahedra, and  a faceface with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-66°. In the second Co site, Co(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form CoO6 octahedra that share corners with four equivalent Mo(1)O6 octahedra, corners with four equivalent Mo(2)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, edges with two equivalent Co(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 32-63°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Mo(1), one Co(1), and one Co(2) atom. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Mg(1), one Mo(1), one Co(1), and one Co(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mo(2), one Co(1), and one Co(2) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mo(2), one Co(1), and one Co(2) atom. In the fifth O site, O(5) is bonded to one Mg(1), one Mo(1), one Mo(2), and one Co(2) atom to form a mixture of corner and edge-sharing OMgCoMo2 trigonal pyramids. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mo(1), one Mo(2), and one Co(2) atom. In the seventh O site, O(7) is bonded to one Mg(1), one Mo(1), one Mo(2), and one Co(1) atom to form a mixture of distorted corner and edge-sharing OMgCoMo2 trigonal pyramids. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mo(1), one Mo(2), and one Co(1) atom.
MgCo2(MoO4)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(2), one O(4), one O(5), one O(7), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with two equivalent Mo(2)O6 octahedra,  an edgeedge with one Mo(2)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, edges with two equivalent Mo(1)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-71°. The Mg(1)-O(2) bond length is 2.07 Å. The Mg(1)-O(4) bond length is 2.10 Å. The Mg(1)-O(5) bond length is 1.93 Å. The Mg(1)-O(7) bond length is 1.93 Å. The Mg(1)-O(8) bond length is 2.17 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form distorted MoO6 octahedra that share corners with four equivalent Co(1)O6 octahedra, corners with four equivalent Co(2)O6 octahedra, edges with two equivalent Mo(2)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 32-63°. The Mo(1)-O(1) bond length is 1.83 Å. The Mo(1)-O(2) bond length is 1.99 Å. The Mo(1)-O(5) bond length is 2.14 Å. The Mo(1)-O(6) bond length is 1.96 Å. The Mo(1)-O(7) bond length is 2.14 Å. The Mo(1)-O(8) bond length is 2.17 Å. In the second Mo site, Mo(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted MoO6 octahedra that share corners with four equivalent Co(1)O6 octahedra, corners with four equivalent Co(2)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Mo(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-66°. The Mo(2)-O(3) bond length is 1.84 Å. The Mo(2)-O(4) bond length is 1.98 Å. The Mo(2)-O(5) bond length is 2.11 Å. The Mo(2)-O(6) bond length is 2.18 Å. The Mo(2)-O(7) bond length is 2.12 Å. The Mo(2)-O(8) bond length is 2.03 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form distorted CoO6 octahedra that share corners with four equivalent Mo(1)O6 octahedra, corners with four equivalent Mo(2)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, edges with two equivalent Co(2)O6 octahedra, and  a faceface with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-66°. The Co(1)-O(1) bond length is 2.05 Å. The Co(1)-O(2) bond length is 2.01 Å. The Co(1)-O(3) bond length is 2.07 Å. The Co(1)-O(4) bond length is 2.31 Å. The Co(1)-O(7) bond length is 2.14 Å. The Co(1)-O(8) bond length is 2.34 Å. In the second Co site, Co(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form CoO6 octahedra that share corners with four equivalent Mo(1)O6 octahedra, corners with four equivalent Mo(2)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, edges with two equivalent Co(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 32-63°. The Co(2)-O(1) bond length is 2.15 Å. The Co(2)-O(2) bond length is 2.20 Å. The Co(2)-O(3) bond length is 2.08 Å. The Co(2)-O(4) bond length is 2.10 Å. The Co(2)-O(5) bond length is 2.10 Å. The Co(2)-O(6) bond length is 2.26 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Mo(1), one Co(1), and one Co(2) atom. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Mg(1), one Mo(1), one Co(1), and one Co(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mo(2), one Co(1), and one Co(2) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mo(2), one Co(1), and one Co(2) atom. In the fifth O site, O(5) is bonded to one Mg(1), one Mo(1), one Mo(2), and one Co(2) atom to form a mixture of corner and edge-sharing OMgCoMo2 trigonal pyramids. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mo(1), one Mo(2), and one Co(2) atom. In the seventh O site, O(7) is bonded to one Mg(1), one Mo(1), one Mo(2), and one Co(1) atom to form a mixture of distorted corner and edge-sharing OMgCoMo2 trigonal pyramids. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mo(1), one Mo(2), and one Co(1) atom.