MgNb2(NO)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to two equivalent N(2), one O(2), and two equivalent O(1) atoms to form MgN2O3 trigonal bipyramids that share  a cornercorner with one Nb(2)N3O3 octahedra, corners with two equivalent Nb(1)N3O3 octahedra, corners with four equivalent Mg(1)N2O3 trigonal bipyramids, edges with two equivalent Nb(1)N3O3 octahedra, and edges with four equivalent Nb(2)N3O3 octahedra. The corner-sharing octahedral tilt angles range from 4-79°. 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(1), and two equivalent O(2) atoms to form distorted NbN3O3 octahedra that share corners with four equivalent Nb(1)N3O3 octahedra, corners with two equivalent Mg(1)N2O3 trigonal bipyramids, edges with four equivalent Nb(2)N3O3 octahedra, and edges with two equivalent Mg(1)N2O3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 13-26°. In the second Nb site, Nb(2) is bonded to one N(1), two equivalent N(2), one O(2), and two equivalent O(1) atoms to form NbN3O3 octahedra that share corners with four equivalent Nb(2)N3O3 octahedra,  a cornercorner with one Mg(1)N2O3 trigonal bipyramid, edges with four equivalent Nb(1)N3O3 octahedra, and edges with four equivalent Mg(1)N2O3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 3-14°. There are two inequivalent N sites. In the first N site, N(1) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(1) atoms. In the second N site, N(2) is bonded to two equivalent Mg(1), one Nb(1), and two equivalent Nb(2) atoms to form NMg2Nb3 trigonal bipyramids that share  a cornercorner with one O(1)Mg2Nb3 square pyramid, corners with four equivalent N(2)Mg2Nb3 trigonal bipyramids, and edges with four equivalent O(1)Mg2Nb3 square pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), one Nb(1), and two equivalent Nb(2) atoms to form distorted OMg2Nb3 square pyramids that share corners with four equivalent O(1)Mg2Nb3 square pyramids,  a cornercorner with one N(2)Mg2Nb3 trigonal bipyramid, and edges with four equivalent N(2)Mg2Nb3 trigonal bipyramids. In the second O site, O(2) is bonded in a square co-planar geometry to one Mg(1), one Nb(2), and two equivalent Nb(1) atoms.
MgNb2(NO)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to two equivalent N(2), one O(2), and two equivalent O(1) atoms to form MgN2O3 trigonal bipyramids that share  a cornercorner with one Nb(2)N3O3 octahedra, corners with two equivalent Nb(1)N3O3 octahedra, corners with four equivalent Mg(1)N2O3 trigonal bipyramids, edges with two equivalent Nb(1)N3O3 octahedra, and edges with four equivalent Nb(2)N3O3 octahedra. The corner-sharing octahedral tilt angles range from 4-79°. There is one shorter (2.10 Å) and one longer (2.11 Å) Mg(1)-N(2) bond length. The Mg(1)-O(2) bond length is 2.03 Å. Both Mg(1)-O(1) bond lengths are 2.18 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(1), and two equivalent O(2) atoms to form distorted NbN3O3 octahedra that share corners with four equivalent Nb(1)N3O3 octahedra, corners with two equivalent Mg(1)N2O3 trigonal bipyramids, edges with four equivalent Nb(2)N3O3 octahedra, and edges with two equivalent Mg(1)N2O3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 13-26°. The Nb(1)-N(2) bond length is 2.06 Å. There is one shorter (1.91 Å) and one longer (2.30 Å) Nb(1)-N(1) bond length. The Nb(1)-O(1) bond length is 2.43 Å. Both Nb(1)-O(2) bond lengths are 2.18 Å. In the second Nb site, Nb(2) is bonded to one N(1), two equivalent N(2), one O(2), and two equivalent O(1) atoms to form NbN3O3 octahedra that share corners with four equivalent Nb(2)N3O3 octahedra,  a cornercorner with one Mg(1)N2O3 trigonal bipyramid, edges with four equivalent Nb(1)N3O3 octahedra, and edges with four equivalent Mg(1)N2O3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 3-14°. The Nb(2)-N(1) bond length is 2.21 Å. Both Nb(2)-N(2) bond lengths are 2.17 Å. The Nb(2)-O(2) bond length is 2.13 Å. There is one shorter (2.06 Å) and one longer (2.07 Å) Nb(2)-O(1) bond length. There are two inequivalent N sites. In the first N site, N(1) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(1) atoms. In the second N site, N(2) is bonded to two equivalent Mg(1), one Nb(1), and two equivalent Nb(2) atoms to form NMg2Nb3 trigonal bipyramids that share  a cornercorner with one O(1)Mg2Nb3 square pyramid, corners with four equivalent N(2)Mg2Nb3 trigonal bipyramids, and edges with four equivalent O(1)Mg2Nb3 square pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), one Nb(1), and two equivalent Nb(2) atoms to form distorted OMg2Nb3 square pyramids that share corners with four equivalent O(1)Mg2Nb3 square pyramids,  a cornercorner with one N(2)Mg2Nb3 trigonal bipyramid, and edges with four equivalent N(2)Mg2Nb3 trigonal bipyramids. In the second O site, O(2) is bonded in a square co-planar geometry to one Mg(1), one Nb(2), and two equivalent Nb(1) atoms.