Mg2CuN2 crystallizes in the monoclinic C2/m 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 trigonal pyramids. In the second Mg site, Mg(2) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form a mixture of edge and corner-sharing MgN4 trigonal pyramids. Cu(1) is bonded in a distorted T-shaped 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 two equivalent Mg(2), three equivalent Mg(1), and one Cu(1) atom to form NMg5Cu octahedra that share corners with two equivalent N(1)Mg5Cu octahedra, corners with three equivalent N(2)Mg3Cu2 trigonal bipyramids, edges with three equivalent N(1)Mg5Cu octahedra, and edges with three equivalent N(2)Mg3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 23°. In the second N site, N(2) is bonded to one Mg(1), two equivalent Mg(2), and two equivalent Cu(1) atoms to form distorted NMg3Cu2 trigonal bipyramids that share corners with three equivalent N(1)Mg5Cu octahedra, corners with two equivalent N(2)Mg3Cu2 trigonal bipyramids, edges with three equivalent N(1)Mg5Cu octahedra, and  an edgeedge with one N(2)Mg3Cu2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 21-76°.
Mg2CuN2 crystallizes in the monoclinic C2/m 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 trigonal pyramids. The Mg(1)-N(2) bond length is 2.14 Å. There are two shorter (2.08 Å) and one longer (2.25 Å) Mg(1)-N(1) bond length. In the second Mg site, Mg(2) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form a mixture of edge and corner-sharing MgN4 trigonal pyramids. There is one shorter (2.10 Å) and one longer (2.23 Å) Mg(2)-N(1) bond length. Both Mg(2)-N(2) bond lengths are 2.11 Å. Cu(1) is bonded in a distorted T-shaped geometry to one N(1) and two equivalent N(2) atoms. The Cu(1)-N(1) bond length is 1.93 Å. There is one shorter (1.84 Å) and one longer (2.16 Å) Cu(1)-N(2) bond length. There are two inequivalent N sites. In the first N site, N(1) is bonded to two equivalent Mg(2), three equivalent Mg(1), and one Cu(1) atom to form NMg5Cu octahedra that share corners with two equivalent N(1)Mg5Cu octahedra, corners with three equivalent N(2)Mg3Cu2 trigonal bipyramids, edges with three equivalent N(1)Mg5Cu octahedra, and edges with three equivalent N(2)Mg3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 23°. In the second N site, N(2) is bonded to one Mg(1), two equivalent Mg(2), and two equivalent Cu(1) atoms to form distorted NMg3Cu2 trigonal bipyramids that share corners with three equivalent N(1)Mg5Cu octahedra, corners with two equivalent N(2)Mg3Cu2 trigonal bipyramids, edges with three equivalent N(1)Mg5Cu octahedra, and  an edgeedge with one N(2)Mg3Cu2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 21-76°.