MgNb4(CoO6)2 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form MgO6 octahedra that share corners with two equivalent Nb(3)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, edges with two equivalent Nb(2)O6 octahedra, and faces with two equivalent Co(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with four equivalent Nb(3)O6 octahedra, corners with four equivalent Co(2)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra,  an edgeedge with one Co(1)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-52°. In the second Nb site, Nb(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form NbO6 octahedra that share corners with four equivalent Nb(4)O6 octahedra, corners with four equivalent Co(2)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra,  an edgeedge with one Co(1)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-52°. In the third Nb site, Nb(3) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, corners with four equivalent Co(1)O6 octahedra,  an edgeedge with one Nb(4)O6 octahedra, and  an edgeedge with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-52°. In the fourth Nb site, Nb(4) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, corners with four equivalent Co(1)O6 octahedra,  an edgeedge with one Nb(3)O6 octahedra, and  an edgeedge with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-52°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form CoO6 octahedra that share corners with four equivalent Nb(3)O6 octahedra, corners with four equivalent Nb(4)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-50°. In the second Co site, Co(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form CoO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra,  an edgeedge with one Nb(3)O6 octahedra,  an edgeedge with one Nb(4)O6 octahedra, and faces with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-52°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(3), and one Co(1) atom. In the second O site, O(2) is bonded to one Mg(1), one Nb(1), one Nb(2), and one Co(2) atom to form a mixture of distorted corner and edge-sharing OMgNb2Co trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(4), and one Co(1) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(3), and one Co(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Nb(3), one Nb(4), and one Co(1) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(2), one Nb(4), and one Co(2) atom.
MgNb4(CoO6)2 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form MgO6 octahedra that share corners with two equivalent Nb(3)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, edges with two equivalent Nb(2)O6 octahedra, and faces with two equivalent Co(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. Both Mg(1)-O(2) bond lengths are 1.96 Å. Both Mg(1)-O(4) bond lengths are 2.15 Å. Both Mg(1)-O(6) bond lengths are 2.15 Å. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with four equivalent Nb(3)O6 octahedra, corners with four equivalent Co(2)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra,  an edgeedge with one Co(1)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-52°. Both Nb(1)-O(1) bond lengths are 1.95 Å. Both Nb(1)-O(2) bond lengths are 2.10 Å. Both Nb(1)-O(4) bond lengths are 2.07 Å. In the second Nb site, Nb(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form NbO6 octahedra that share corners with four equivalent Nb(4)O6 octahedra, corners with four equivalent Co(2)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra,  an edgeedge with one Co(1)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-52°. Both Nb(2)-O(2) bond lengths are 2.10 Å. Both Nb(2)-O(3) bond lengths are 1.95 Å. Both Nb(2)-O(6) bond lengths are 2.07 Å. In the third Nb site, Nb(3) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, corners with four equivalent Co(1)O6 octahedra,  an edgeedge with one Nb(4)O6 octahedra, and  an edgeedge with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-52°. Both Nb(3)-O(1) bond lengths are 2.04 Å. Both Nb(3)-O(4) bond lengths are 2.07 Å. Both Nb(3)-O(5) bond lengths are 2.01 Å. In the fourth Nb site, Nb(4) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, corners with four equivalent Co(1)O6 octahedra,  an edgeedge with one Nb(3)O6 octahedra, and  an edgeedge with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-52°. Both Nb(4)-O(3) bond lengths are 2.04 Å. Both Nb(4)-O(5) bond lengths are 2.00 Å. Both Nb(4)-O(6) bond lengths are 2.08 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form CoO6 octahedra that share corners with four equivalent Nb(3)O6 octahedra, corners with four equivalent Nb(4)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-50°. Both Co(1)-O(1) bond lengths are 2.18 Å. Both Co(1)-O(3) bond lengths are 2.18 Å. Both Co(1)-O(5) bond lengths are 2.28 Å. In the second Co site, Co(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form CoO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra,  an edgeedge with one Nb(3)O6 octahedra,  an edgeedge with one Nb(4)O6 octahedra, and faces with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-52°. Both Co(2)-O(2) bond lengths are 2.28 Å. Both Co(2)-O(4) bond lengths are 2.14 Å. Both Co(2)-O(6) bond lengths are 2.15 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(3), and one Co(1) atom. In the second O site, O(2) is bonded to one Mg(1), one Nb(1), one Nb(2), and one Co(2) atom to form a mixture of distorted corner and edge-sharing OMgNb2Co trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(4), and one Co(1) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(3), and one Co(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Nb(3), one Nb(4), and one Co(1) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(2), one Nb(4), and one Co(2) atom.