MgNb4(CoO6)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(2), one O(4), one O(5), one O(8), and one O(9) atom to form distorted MgO6 octahedra that share  a cornercorner with one Co(1)O6 octahedra, corners with two equivalent Co(2)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-52°. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(11), one O(2), one O(3), one O(4), and one O(9) atom to form distorted NbO6 octahedra that share corners with two equivalent Co(2)O6 octahedra, corners with three equivalent Co(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-58°. In the second Nb site, Nb(2) is bonded to one O(12), one O(2), one O(3), one O(6), one O(7), and one O(8) atom to form NbO6 octahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(2)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-64°. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(11), one O(5), one O(6), and one O(7) atom. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(8) atom. 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(5), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-64°. In the second Co site, Co(2) is bonded to one O(1), one O(12), one O(4), one O(6), one O(7), and one O(9) atom to form CoO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, and  an edgeedge with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-58°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(3), one Co(1), and one Co(2) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Co(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Co(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal pyramidal geometry to one Mg(1), one Nb(1), one Nb(4), and one Co(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(1), one Nb(3), one Nb(4), and one Co(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Co(2) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Nb(2), one Nb(3), and one Co(2) atom. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to one Mg(1), one Nb(2), one Nb(4), and one Co(1) atom. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Co(1), and one Co(2) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Mg(1), one Nb(1), one Nb(3), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Nb(4) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(4), and one Co(2) atom.
MgNb4(CoO6)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(2), one O(4), one O(5), one O(8), and one O(9) atom to form distorted MgO6 octahedra that share  a cornercorner with one Co(1)O6 octahedra, corners with two equivalent Co(2)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-52°. The Mg(1)-O(10) bond length is 1.97 Å. The Mg(1)-O(2) bond length is 1.96 Å. The Mg(1)-O(4) bond length is 2.06 Å. The Mg(1)-O(5) bond length is 2.07 Å. The Mg(1)-O(8) bond length is 2.23 Å. The Mg(1)-O(9) bond length is 2.15 Å. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(11), one O(2), one O(3), one O(4), and one O(9) atom to form distorted NbO6 octahedra that share corners with two equivalent Co(2)O6 octahedra, corners with three equivalent Co(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-58°. The Nb(1)-O(10) bond length is 2.04 Å. The Nb(1)-O(11) bond length is 2.28 Å. The Nb(1)-O(2) bond length is 1.99 Å. The Nb(1)-O(3) bond length is 1.90 Å. The Nb(1)-O(4) bond length is 2.31 Å. The Nb(1)-O(9) bond length is 1.91 Å. In the second Nb site, Nb(2) is bonded to one O(12), one O(2), one O(3), one O(6), one O(7), and one O(8) atom to form NbO6 octahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(2)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-64°. The Nb(2)-O(12) bond length is 2.13 Å. The Nb(2)-O(2) bond length is 2.27 Å. The Nb(2)-O(3) bond length is 2.20 Å. The Nb(2)-O(6) bond length is 2.04 Å. The Nb(2)-O(7) bond length is 2.03 Å. The Nb(2)-O(8) bond length is 2.00 Å. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(11), one O(5), one O(6), and one O(7) atom. The Nb(3)-O(1) bond length is 1.85 Å. The Nb(3)-O(10) bond length is 2.19 Å. The Nb(3)-O(11) bond length is 2.21 Å. The Nb(3)-O(5) bond length is 2.46 Å. The Nb(3)-O(6) bond length is 2.02 Å. The Nb(3)-O(7) bond length is 2.03 Å. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(8) atom. The Nb(4)-O(10) bond length is 2.68 Å. The Nb(4)-O(11) bond length is 1.88 Å. The Nb(4)-O(12) bond length is 1.91 Å. The Nb(4)-O(4) bond length is 2.01 Å. The Nb(4)-O(5) bond length is 1.97 Å. The Nb(4)-O(8) bond length is 2.20 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(5), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-64°. The Co(1)-O(1) bond length is 1.97 Å. The Co(1)-O(2) bond length is 2.41 Å. The Co(1)-O(3) bond length is 2.00 Å. The Co(1)-O(5) bond length is 2.14 Å. The Co(1)-O(8) bond length is 2.14 Å. The Co(1)-O(9) bond length is 2.13 Å. In the second Co site, Co(2) is bonded to one O(1), one O(12), one O(4), one O(6), one O(7), and one O(9) atom to form CoO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, and  an edgeedge with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-58°. The Co(2)-O(1) bond length is 2.04 Å. The Co(2)-O(12) bond length is 2.16 Å. The Co(2)-O(4) bond length is 2.21 Å. The Co(2)-O(6) bond length is 2.10 Å. The Co(2)-O(7) bond length is 2.10 Å. The Co(2)-O(9) bond length is 2.22 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(3), one Co(1), and one Co(2) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Co(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Co(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal pyramidal geometry to one Mg(1), one Nb(1), one Nb(4), and one Co(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(1), one Nb(3), one Nb(4), and one Co(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Co(2) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Nb(2), one Nb(3), and one Co(2) atom. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to one Mg(1), one Nb(2), one Nb(4), and one Co(1) atom. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Co(1), and one Co(2) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Mg(1), one Nb(1), one Nb(3), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Nb(4) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(4), and one Co(2) atom.