MgNb4(NO)4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a distorted hexagonal planar geometry to two equivalent N(1) and four equivalent O(2) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one N(2), two equivalent N(1), one O(2), and two equivalent O(1) atoms to form distorted NbN3O3 pentagonal pyramids that share corners with two equivalent Nb(2)N4O2 octahedra, corners with two equivalent Nb(1)N3O3 pentagonal pyramids, edges with three equivalent Nb(2)N4O2 octahedra, and  an edgeedge with one Nb(1)N3O3 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 35-41°. In the second Nb site, Nb(2) is bonded to one N(1), three equivalent N(2), one O(1), and one O(2) atom to form distorted NbN4O2 octahedra that share corners with two equivalent Nb(2)N4O2 octahedra, corners with two equivalent Nb(1)N3O3 pentagonal pyramids, edges with two equivalent Nb(2)N4O2 octahedra, and edges with three equivalent Nb(1)N3O3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 21°. There are two inequivalent N sites. In the first N site, N(1) is bonded in a distorted square co-planar geometry to one Mg(1), one Nb(2), and two equivalent Nb(1) atoms. In the second N site, N(2) is bonded to one Nb(1) and three equivalent Nb(2) atoms to form distorted NNb4 trigonal pyramids that share corners with four equivalent O(2)Mg2Nb2 tetrahedra, corners with two equivalent N(2)Nb4 trigonal pyramids, and edges with two equivalent N(2)Nb4 trigonal pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Nb(2) and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Nb(1), and one Nb(2) atom to form distorted OMg2Nb2 tetrahedra that share corners with four equivalent O(2)Mg2Nb2 tetrahedra, corners with four equivalent N(2)Nb4 trigonal pyramids, and  an edgeedge with one O(2)Mg2Nb2 tetrahedra.
MgNb4(NO)4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a distorted hexagonal planar geometry to two equivalent N(1) and four equivalent O(2) atoms. Both Mg(1)-N(1) bond lengths are 2.38 Å. All Mg(1)-O(2) bond lengths are 2.41 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one N(2), two equivalent N(1), one O(2), and two equivalent O(1) atoms to form distorted NbN3O3 pentagonal pyramids that share corners with two equivalent Nb(2)N4O2 octahedra, corners with two equivalent Nb(1)N3O3 pentagonal pyramids, edges with three equivalent Nb(2)N4O2 octahedra, and  an edgeedge with one Nb(1)N3O3 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 35-41°. The Nb(1)-N(2) bond length is 2.13 Å. Both Nb(1)-N(1) bond lengths are 2.08 Å. The Nb(1)-O(2) bond length is 2.15 Å. There is one shorter (2.02 Å) and one longer (2.09 Å) Nb(1)-O(1) bond length. In the second Nb site, Nb(2) is bonded to one N(1), three equivalent N(2), one O(1), and one O(2) atom to form distorted NbN4O2 octahedra that share corners with two equivalent Nb(2)N4O2 octahedra, corners with two equivalent Nb(1)N3O3 pentagonal pyramids, edges with two equivalent Nb(2)N4O2 octahedra, and edges with three equivalent Nb(1)N3O3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 21°. The Nb(2)-N(1) bond length is 2.11 Å. There are two shorter (2.06 Å) and one longer (2.27 Å) Nb(2)-N(2) bond length. The Nb(2)-O(1) bond length is 2.17 Å. The Nb(2)-O(2) bond length is 1.95 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded in a distorted square co-planar geometry to one Mg(1), one Nb(2), and two equivalent Nb(1) atoms. In the second N site, N(2) is bonded to one Nb(1) and three equivalent Nb(2) atoms to form distorted NNb4 trigonal pyramids that share corners with four equivalent O(2)Mg2Nb2 tetrahedra, corners with two equivalent N(2)Nb4 trigonal pyramids, and edges with two equivalent N(2)Nb4 trigonal pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Nb(2) and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Nb(1), and one Nb(2) atom to form distorted OMg2Nb2 tetrahedra that share corners with four equivalent O(2)Mg2Nb2 tetrahedra, corners with four equivalent N(2)Nb4 trigonal pyramids, and  an edgeedge with one O(2)Mg2Nb2 tetrahedra.