MgNb4(NO)4 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent N(2), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgN2O4 octahedra that share corners with two equivalent Nb(1)N4O3 pentagonal bipyramids, corners with four equivalent Nb(2)N4O2 pentagonal pyramids, edges with four equivalent Nb(1)N4O3 pentagonal bipyramids, and edges with two equivalent Nb(2)N4O2 pentagonal pyramids. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent N(1), two equivalent N(2), one O(2), and two equivalent O(1) atoms to form distorted NbN4O3 pentagonal bipyramids that share  a cornercorner with one Mg(1)N2O4 octahedra, corners with three equivalent Nb(2)N4O2 pentagonal pyramids, edges with two equivalent Mg(1)N2O4 octahedra, edges with three equivalent Nb(1)N4O3 pentagonal bipyramids, and edges with four equivalent Nb(2)N4O2 pentagonal pyramids. The corner-sharing octahedral tilt angles are 23°. In the second Nb site, Nb(2) is bonded to two equivalent N(1), two equivalent N(2), one O(1), and one O(2) atom to form distorted NbN4O2 pentagonal pyramids that share corners with two equivalent Mg(1)N2O4 octahedra, corners with three equivalent Nb(1)N4O3 pentagonal bipyramids,  an edgeedge with one Mg(1)N2O4 octahedra, edges with four equivalent Nb(1)N4O3 pentagonal bipyramids, and edges with two equivalent Nb(2)N4O2 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 51-74°. There are two inequivalent N sites. In the first N site, N(1) is bonded to two equivalent Nb(1) and two equivalent Nb(2) atoms to form NNb4 trigonal pyramids that share corners with four equivalent N(2)MgNb4 trigonal bipyramids, corners with six equivalent O(1)MgNb3 trigonal pyramids, edges with two equivalent N(2)MgNb4 trigonal bipyramids, and edges with two equivalent N(1)Nb4 trigonal pyramids. In the second N site, N(2) is bonded to one Mg(1), two equivalent Nb(1), and two equivalent Nb(2) atoms to form NMgNb4 trigonal bipyramids that share  a cornercorner with one N(2)MgNb4 trigonal bipyramid, corners with two equivalent O(1)MgNb3 trigonal pyramids, corners with four equivalent N(1)Nb4 trigonal pyramids, edges with two equivalent N(2)MgNb4 trigonal bipyramids, edges with two equivalent N(1)Nb4 trigonal pyramids, and edges with three equivalent O(1)MgNb3 trigonal pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Nb(2), and two equivalent Nb(1) atoms to form distorted OMgNb3 trigonal pyramids that share corners with two equivalent N(2)MgNb4 trigonal bipyramids,  a cornercorner with one O(1)MgNb3 trigonal pyramid, corners with six equivalent N(1)Nb4 trigonal pyramids, edges with three equivalent N(2)MgNb4 trigonal bipyramids, and  an edgeedge with one O(1)MgNb3 trigonal pyramid. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Nb(1), and one Nb(2) atom.
MgNb4(NO)4 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent N(2), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgN2O4 octahedra that share corners with two equivalent Nb(1)N4O3 pentagonal bipyramids, corners with four equivalent Nb(2)N4O2 pentagonal pyramids, edges with four equivalent Nb(1)N4O3 pentagonal bipyramids, and edges with two equivalent Nb(2)N4O2 pentagonal pyramids. Both Mg(1)-N(2) bond lengths are 2.39 Å. Both Mg(1)-O(1) bond lengths are 1.96 Å. Both Mg(1)-O(2) bond lengths are 2.07 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent N(1), two equivalent N(2), one O(2), and two equivalent O(1) atoms to form distorted NbN4O3 pentagonal bipyramids that share  a cornercorner with one Mg(1)N2O4 octahedra, corners with three equivalent Nb(2)N4O2 pentagonal pyramids, edges with two equivalent Mg(1)N2O4 octahedra, edges with three equivalent Nb(1)N4O3 pentagonal bipyramids, and edges with four equivalent Nb(2)N4O2 pentagonal pyramids. The corner-sharing octahedral tilt angles are 23°. There is one shorter (2.08 Å) and one longer (2.14 Å) Nb(1)-N(1) bond length. There is one shorter (2.20 Å) and one longer (2.21 Å) Nb(1)-N(2) bond length. The Nb(1)-O(2) bond length is 2.11 Å. There is one shorter (2.18 Å) and one longer (2.38 Å) Nb(1)-O(1) bond length. In the second Nb site, Nb(2) is bonded to two equivalent N(1), two equivalent N(2), one O(1), and one O(2) atom to form distorted NbN4O2 pentagonal pyramids that share corners with two equivalent Mg(1)N2O4 octahedra, corners with three equivalent Nb(1)N4O3 pentagonal bipyramids,  an edgeedge with one Mg(1)N2O4 octahedra, edges with four equivalent Nb(1)N4O3 pentagonal bipyramids, and edges with two equivalent Nb(2)N4O2 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 51-74°. There is one shorter (2.03 Å) and one longer (2.16 Å) Nb(2)-N(1) bond length. There is one shorter (2.16 Å) and one longer (2.24 Å) Nb(2)-N(2) bond length. The Nb(2)-O(1) bond length is 2.05 Å. The Nb(2)-O(2) bond length is 2.02 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded to two equivalent Nb(1) and two equivalent Nb(2) atoms to form NNb4 trigonal pyramids that share corners with four equivalent N(2)MgNb4 trigonal bipyramids, corners with six equivalent O(1)MgNb3 trigonal pyramids, edges with two equivalent N(2)MgNb4 trigonal bipyramids, and edges with two equivalent N(1)Nb4 trigonal pyramids. In the second N site, N(2) is bonded to one Mg(1), two equivalent Nb(1), and two equivalent Nb(2) atoms to form NMgNb4 trigonal bipyramids that share  a cornercorner with one N(2)MgNb4 trigonal bipyramid, corners with two equivalent O(1)MgNb3 trigonal pyramids, corners with four equivalent N(1)Nb4 trigonal pyramids, edges with two equivalent N(2)MgNb4 trigonal bipyramids, edges with two equivalent N(1)Nb4 trigonal pyramids, and edges with three equivalent O(1)MgNb3 trigonal pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Nb(2), and two equivalent Nb(1) atoms to form distorted OMgNb3 trigonal pyramids that share corners with two equivalent N(2)MgNb4 trigonal bipyramids,  a cornercorner with one O(1)MgNb3 trigonal pyramid, corners with six equivalent N(1)Nb4 trigonal pyramids, edges with three equivalent N(2)MgNb4 trigonal bipyramids, and  an edgeedge with one O(1)MgNb3 trigonal pyramid. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Nb(1), and one Nb(2) atom.