Mg11(CN5)2 crystallizes in the tetragonal P4_2/mnm space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(4) and four equivalent N(1) atoms to form MgN6 octahedra that share edges with two equivalent Mg(1)N6 octahedra and edges with eight equivalent Mg(2)N5 trigonal bipyramids. In the second Mg site, Mg(2) is bonded to one N(1), two equivalent N(2), and two equivalent N(4) atoms to form distorted MgN5 trigonal bipyramids that share corners with three equivalent Mg(2)N5 trigonal bipyramids, corners with four equivalent Mg(4)N4 trigonal pyramids, edges with two equivalent Mg(1)N6 octahedra, edges with three equivalent Mg(2)N5 trigonal bipyramids, and  an edgeedge with one Mg(4)N4 trigonal pyramid. In the third Mg site, Mg(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent N(1) and two equivalent N(3) atoms. In the fourth Mg site, Mg(4) is bonded to one N(3) and three equivalent N(2) atoms to form distorted MgN4 trigonal pyramids that share corners with four equivalent Mg(2)N5 trigonal bipyramids, corners with seven equivalent Mg(4)N4 trigonal pyramids, and  an edgeedge with one Mg(2)N5 trigonal bipyramid. C(1) is bonded in a linear geometry to one N(3) and one N(4) atom. There are four inequivalent N sites. In the first N site, N(3) is bonded to two equivalent Mg(3), two equivalent Mg(4), and one C(1) atom to form distorted NMg4C trigonal bipyramids that share  a cornercorner with one N(4)Mg5C octahedra, corners with two equivalent N(1)Mg6 octahedra, corners with two equivalent N(3)Mg4C trigonal bipyramids, and  an edgeedge with one N(1)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second N site, N(4) is bonded to one Mg(1), four equivalent Mg(2), and one C(1) atom to form distorted NMg5C octahedra that share  a cornercorner with one N(4)Mg5C octahedra,  a cornercorner with one N(3)Mg4C trigonal bipyramid, edges with two equivalent N(4)Mg5C octahedra, and edges with four equivalent N(1)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the third N site, N(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mg(3) atoms to form NMg6 octahedra that share corners with two equivalent N(1)Mg6 octahedra, corners with two equivalent N(3)Mg4C trigonal bipyramids, edges with three equivalent N(1)Mg6 octahedra, edges with four equivalent N(4)Mg5C octahedra, and  an edgeedge with one N(3)Mg4C trigonal bipyramid. The corner-sharing octahedra are not tilted. In the fourth N site, N(2) is bonded in a 5-coordinate geometry to two equivalent Mg(2) and three equivalent Mg(4) atoms.
Mg11(CN5)2 crystallizes in the tetragonal P4_2/mnm space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(4) and four equivalent N(1) atoms to form MgN6 octahedra that share edges with two equivalent Mg(1)N6 octahedra and edges with eight equivalent Mg(2)N5 trigonal bipyramids. Both Mg(1)-N(4) bond lengths are 2.31 Å. All Mg(1)-N(1) bond lengths are 2.25 Å. In the second Mg site, Mg(2) is bonded to one N(1), two equivalent N(2), and two equivalent N(4) atoms to form distorted MgN5 trigonal bipyramids that share corners with three equivalent Mg(2)N5 trigonal bipyramids, corners with four equivalent Mg(4)N4 trigonal pyramids, edges with two equivalent Mg(1)N6 octahedra, edges with three equivalent Mg(2)N5 trigonal bipyramids, and  an edgeedge with one Mg(4)N4 trigonal pyramid. The Mg(2)-N(1) bond length is 2.06 Å. Both Mg(2)-N(2) bond lengths are 2.18 Å. Both Mg(2)-N(4) bond lengths are 2.41 Å. In the third Mg site, Mg(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent N(1) and two equivalent N(3) atoms. Both Mg(3)-N(1) bond lengths are 2.11 Å. Both Mg(3)-N(3) bond lengths are 2.20 Å. In the fourth Mg site, Mg(4) is bonded to one N(3) and three equivalent N(2) atoms to form distorted MgN4 trigonal pyramids that share corners with four equivalent Mg(2)N5 trigonal bipyramids, corners with seven equivalent Mg(4)N4 trigonal pyramids, and  an edgeedge with one Mg(2)N5 trigonal bipyramid. The Mg(4)-N(3) bond length is 2.69 Å. There are two shorter (2.10 Å) and one longer (2.11 Å) Mg(4)-N(2) bond length. C(1) is bonded in a linear geometry to one N(3) and one N(4) atom. The C(1)-N(3) bond length is 1.23 Å. The C(1)-N(4) bond length is 1.24 Å. There are four inequivalent N sites. In the first N site, N(3) is bonded to two equivalent Mg(3), two equivalent Mg(4), and one C(1) atom to form distorted NMg4C trigonal bipyramids that share  a cornercorner with one N(4)Mg5C octahedra, corners with two equivalent N(1)Mg6 octahedra, corners with two equivalent N(3)Mg4C trigonal bipyramids, and  an edgeedge with one N(1)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second N site, N(4) is bonded to one Mg(1), four equivalent Mg(2), and one C(1) atom to form distorted NMg5C octahedra that share  a cornercorner with one N(4)Mg5C octahedra,  a cornercorner with one N(3)Mg4C trigonal bipyramid, edges with two equivalent N(4)Mg5C octahedra, and edges with four equivalent N(1)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the third N site, N(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mg(3) atoms to form NMg6 octahedra that share corners with two equivalent N(1)Mg6 octahedra, corners with two equivalent N(3)Mg4C trigonal bipyramids, edges with three equivalent N(1)Mg6 octahedra, edges with four equivalent N(4)Mg5C octahedra, and  an edgeedge with one N(3)Mg4C trigonal bipyramid. The corner-sharing octahedra are not tilted. In the fourth N site, N(2) is bonded in a 5-coordinate geometry to two equivalent Mg(2) and three equivalent Mg(4) atoms.