Mg3(BiN2)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one N(2) and three equivalent N(1) atoms to form a mixture of distorted edge and corner-sharing MgN4 tetrahedra. In the second Mg site, Mg(2) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form distorted corner-sharing MgN4 tetrahedra. Bi(1) is bonded in a 3-coordinate geometry to one N(1) and two equivalent N(2) atoms. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Mg(2), three equivalent Mg(1), and one Bi(1) atom to form NMg4Bi trigonal bipyramids that share corners with five equivalent N(2)Mg2Bi2 tetrahedra, corners with three equivalent N(1)Mg4Bi trigonal bipyramids,  an edgeedge with one N(2)Mg2Bi2 tetrahedra, and edges with two equivalent N(1)Mg4Bi trigonal bipyramids. In the second N site, N(2) is bonded to one Mg(1), one Mg(2), and two equivalent Bi(1) atoms to form distorted NMg2Bi2 tetrahedra that share corners with three equivalent N(2)Mg2Bi2 tetrahedra, corners with five equivalent N(1)Mg4Bi trigonal bipyramids, and  an edgeedge with one N(1)Mg4Bi trigonal bipyramid.
Mg3(BiN2)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one N(2) and three equivalent N(1) atoms to form a mixture of distorted edge and corner-sharing MgN4 tetrahedra. The Mg(1)-N(2) bond length is 2.10 Å. There are a spread of Mg(1)-N(1) bond distances ranging from 2.09-2.22 Å. In the second Mg site, Mg(2) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form distorted corner-sharing MgN4 tetrahedra. Both Mg(2)-N(1) bond lengths are 2.29 Å. Both Mg(2)-N(2) bond lengths are 2.19 Å. Bi(1) is bonded in a 3-coordinate geometry to one N(1) and two equivalent N(2) atoms. The Bi(1)-N(1) bond length is 2.23 Å. There is one shorter (2.29 Å) and one longer (2.32 Å) Bi(1)-N(2) bond length. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Mg(2), three equivalent Mg(1), and one Bi(1) atom to form NMg4Bi trigonal bipyramids that share corners with five equivalent N(2)Mg2Bi2 tetrahedra, corners with three equivalent N(1)Mg4Bi trigonal bipyramids,  an edgeedge with one N(2)Mg2Bi2 tetrahedra, and edges with two equivalent N(1)Mg4Bi trigonal bipyramids. In the second N site, N(2) is bonded to one Mg(1), one Mg(2), and two equivalent Bi(1) atoms to form distorted NMg2Bi2 tetrahedra that share corners with three equivalent N(2)Mg2Bi2 tetrahedra, corners with five equivalent N(1)Mg4Bi trigonal bipyramids, and  an edgeedge with one N(1)Mg4Bi trigonal bipyramid.