MgNb4(NO)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one N(2), two equivalent N(4), one O(1), and one O(4) atom to form MgN3O2 square pyramids that share  a cornercorner with one Nb(1)N3O3 octahedra,  a cornercorner with one Nb(3)N4O2 octahedra, corners with two equivalent Mg(1)N3O2 square pyramids,  an edgeedge with one Nb(2)N4O2 octahedra, edges with two equivalent Nb(1)N3O3 octahedra, and edges with two equivalent Nb(3)N4O2 octahedra. The corner-sharing octahedral tilt angles range from 8-20°. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one N(1), one N(2), one N(4), one O(2), and two equivalent O(1) atoms to form distorted NbN3O3 octahedra that share  a cornercorner with one Nb(2)N4O2 octahedra,  a cornercorner with one Nb(3)N4O2 octahedra, corners with two equivalent Nb(1)N3O3 octahedra,  a cornercorner with one Mg(1)N3O2 square pyramid,  an edgeedge with one Nb(2)N4O2 octahedra, edges with two equivalent Nb(3)N4O2 octahedra, and edges with two equivalent Mg(1)N3O2 square pyramids. The corner-sharing octahedral tilt angles range from 3-13°. In the second Nb site, Nb(2) is bonded to one N(1), one N(2), two equivalent N(3), one O(2), and one O(4) atom to form distorted NbN4O2 octahedra that share  a cornercorner with one Nb(1)N3O3 octahedra, corners with two equivalent Nb(2)N4O2 octahedra,  an edgeedge with one Nb(1)N3O3 octahedra, edges with two equivalent Nb(3)N4O2 octahedra, and  an edgeedge with one Mg(1)N3O2 square pyramid. The corner-sharing octahedral tilt angles range from 3-25°. In the third Nb site, Nb(3) is bonded to one N(3), one N(4), two equivalent N(2), one O(1), and one O(3) atom to form NbN4O2 octahedra that share  a cornercorner with one Nb(1)N3O3 octahedra, corners with two equivalent Nb(3)N4O2 octahedra,  a cornercorner with one Mg(1)N3O2 square pyramid, edges with two equivalent Nb(1)N3O3 octahedra, edges with two equivalent Nb(2)N4O2 octahedra, and edges with two equivalent Mg(1)N3O2 square pyramids. The corner-sharing octahedral tilt angles range from 3-13°. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one N(1), one N(3), one N(4), one O(3), and two equivalent O(4) atoms. There are four inequivalent N sites. In the first N site, N(1) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(4) atom. In the second N site, N(2) is bonded to one Mg(1), one Nb(1), one Nb(2), and two equivalent Nb(3) atoms to form NMgNb4 square pyramids that share  a cornercorner with one N(4)Mg2Nb3 square pyramid, corners with two equivalent N(2)MgNb4 square pyramids, edges with two equivalent N(4)Mg2Nb3 square pyramids, and edges with two equivalent N(3)Nb4 trigonal pyramids. In the third N site, N(3) is bonded to one Nb(3), one Nb(4), and two equivalent Nb(2) atoms to form NNb4 trigonal pyramids that share corners with two equivalent N(3)Nb4 trigonal pyramids,  an edgeedge with one N(4)Mg2Nb3 square pyramid, and edges with two equivalent N(2)MgNb4 square pyramids. In the fourth N site, N(4) is bonded to two equivalent Mg(1), one Nb(1), one Nb(3), and one Nb(4) atom to form distorted NMg2Nb3 square pyramids that share  a cornercorner with one N(2)MgNb4 square pyramid, corners with two equivalent N(4)Mg2Nb3 square pyramids, edges with two equivalent N(2)MgNb4 square pyramids, and  an edgeedge with one N(3)Nb4 trigonal pyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(3), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the third O site, O(3) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Nb(2), and two equivalent Nb(4) atoms.
MgNb4(NO)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one N(2), two equivalent N(4), one O(1), and one O(4) atom to form MgN3O2 square pyramids that share  a cornercorner with one Nb(1)N3O3 octahedra,  a cornercorner with one Nb(3)N4O2 octahedra, corners with two equivalent Mg(1)N3O2 square pyramids,  an edgeedge with one Nb(2)N4O2 octahedra, edges with two equivalent Nb(1)N3O3 octahedra, and edges with two equivalent Nb(3)N4O2 octahedra. The corner-sharing octahedral tilt angles range from 8-20°. The Mg(1)-N(2) bond length is 2.16 Å. Both Mg(1)-N(4) bond lengths are 2.10 Å. The Mg(1)-O(1) bond length is 2.05 Å. The Mg(1)-O(4) bond length is 2.07 Å. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one N(1), one N(2), one N(4), one O(2), and two equivalent O(1) atoms to form distorted NbN3O3 octahedra that share  a cornercorner with one Nb(2)N4O2 octahedra,  a cornercorner with one Nb(3)N4O2 octahedra, corners with two equivalent Nb(1)N3O3 octahedra,  a cornercorner with one Mg(1)N3O2 square pyramid,  an edgeedge with one Nb(2)N4O2 octahedra, edges with two equivalent Nb(3)N4O2 octahedra, and edges with two equivalent Mg(1)N3O2 square pyramids. The corner-sharing octahedral tilt angles range from 3-13°. The Nb(1)-N(1) bond length is 2.38 Å. The Nb(1)-N(2) bond length is 2.23 Å. The Nb(1)-N(4) bond length is 2.09 Å. The Nb(1)-O(2) bond length is 1.85 Å. Both Nb(1)-O(1) bond lengths are 2.10 Å. In the second Nb site, Nb(2) is bonded to one N(1), one N(2), two equivalent N(3), one O(2), and one O(4) atom to form distorted NbN4O2 octahedra that share  a cornercorner with one Nb(1)N3O3 octahedra, corners with two equivalent Nb(2)N4O2 octahedra,  an edgeedge with one Nb(1)N3O3 octahedra, edges with two equivalent Nb(3)N4O2 octahedra, and  an edgeedge with one Mg(1)N3O2 square pyramid. The corner-sharing octahedral tilt angles range from 3-25°. The Nb(2)-N(1) bond length is 1.87 Å. The Nb(2)-N(2) bond length is 2.22 Å. Both Nb(2)-N(3) bond lengths are 2.15 Å. The Nb(2)-O(2) bond length is 2.05 Å. The Nb(2)-O(4) bond length is 2.37 Å. In the third Nb site, Nb(3) is bonded to one N(3), one N(4), two equivalent N(2), one O(1), and one O(3) atom to form NbN4O2 octahedra that share  a cornercorner with one Nb(1)N3O3 octahedra, corners with two equivalent Nb(3)N4O2 octahedra,  a cornercorner with one Mg(1)N3O2 square pyramid, edges with two equivalent Nb(1)N3O3 octahedra, edges with two equivalent Nb(2)N4O2 octahedra, and edges with two equivalent Mg(1)N3O2 square pyramids. The corner-sharing octahedral tilt angles range from 3-13°. The Nb(3)-N(3) bond length is 2.10 Å. The Nb(3)-N(4) bond length is 2.06 Å. Both Nb(3)-N(2) bond lengths are 2.10 Å. The Nb(3)-O(1) bond length is 2.25 Å. The Nb(3)-O(3) bond length is 2.15 Å. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one N(1), one N(3), one N(4), one O(3), and two equivalent O(4) atoms. The Nb(4)-N(1) bond length is 2.02 Å. The Nb(4)-N(3) bond length is 2.14 Å. The Nb(4)-N(4) bond length is 2.52 Å. The Nb(4)-O(3) bond length is 1.83 Å. Both Nb(4)-O(4) bond lengths are 2.13 Å. There are four inequivalent N sites. In the first N site, N(1) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(4) atom. In the second N site, N(2) is bonded to one Mg(1), one Nb(1), one Nb(2), and two equivalent Nb(3) atoms to form NMgNb4 square pyramids that share  a cornercorner with one N(4)Mg2Nb3 square pyramid, corners with two equivalent N(2)MgNb4 square pyramids, edges with two equivalent N(4)Mg2Nb3 square pyramids, and edges with two equivalent N(3)Nb4 trigonal pyramids. In the third N site, N(3) is bonded to one Nb(3), one Nb(4), and two equivalent Nb(2) atoms to form NNb4 trigonal pyramids that share corners with two equivalent N(3)Nb4 trigonal pyramids,  an edgeedge with one N(4)Mg2Nb3 square pyramid, and edges with two equivalent N(2)MgNb4 square pyramids. In the fourth N site, N(4) is bonded to two equivalent Mg(1), one Nb(1), one Nb(3), and one Nb(4) atom to form distorted NMg2Nb3 square pyramids that share  a cornercorner with one N(2)MgNb4 square pyramid, corners with two equivalent N(4)Mg2Nb3 square pyramids, edges with two equivalent N(2)MgNb4 square pyramids, and  an edgeedge with one N(3)Nb4 trigonal pyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(3), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the third O site, O(3) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Nb(2), and two equivalent Nb(4) atoms.