Nb12N11 crystallizes in the monoclinic C2/m space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent N(2), two equivalent N(3), and two equivalent N(5) atoms to form NbN6 octahedra that share corners with six equivalent Nb(2)N5 square pyramids, edges with two equivalent Nb(1)N6 octahedra, edges with two equivalent Nb(4)N6 octahedra, edges with four equivalent Nb(5)N6 octahedra, edges with two equivalent Nb(2)N5 square pyramids, and edges with two equivalent Nb(3)N5 square pyramids. In the second Nb site, Nb(2) is bonded to one N(1), one N(2), one N(3), one N(4), and one N(5) atom to form NbN5 square pyramids that share corners with three equivalent Nb(1)N6 octahedra, corners with two equivalent Nb(3)N5 square pyramids, corners with four equivalent Nb(2)N5 square pyramids,  an edgeedge with one Nb(1)N6 octahedra, edges with two equivalent Nb(5)N6 octahedra, edges with three equivalent Nb(4)N6 octahedra,  an edgeedge with one Nb(2)N5 square pyramid, and  an edgeedge with one Nb(3)N5 square pyramid. The corner-sharing octahedral tilt angles range from 3-4°. In the third Nb site, Nb(3) is bonded to one N(3), two equivalent N(1), and two equivalent N(2) atoms to form NbN5 square pyramids that share corners with two equivalent Nb(4)N6 octahedra, corners with three equivalent Nb(5)N6 octahedra, corners with four equivalent Nb(2)N5 square pyramids,  an edgeedge with one Nb(5)N6 octahedra, edges with two equivalent Nb(1)N6 octahedra, edges with two equivalent Nb(4)N6 octahedra,  an edgeedge with one Nb(3)N5 square pyramid, and edges with two equivalent Nb(2)N5 square pyramids. The corner-sharing octahedral tilt angles range from 0-4°. In the fourth Nb site, Nb(4) is bonded to one N(4), one N(5), two equivalent N(1), and two equivalent N(2) atoms to form NbN6 octahedra that share  a cornercorner with one Nb(4)N6 octahedra, corners with three equivalent Nb(5)N6 octahedra, corners with two equivalent Nb(3)N5 square pyramids,  an edgeedge with one Nb(4)N6 octahedra,  an edgeedge with one Nb(5)N6 octahedra, edges with two equivalent Nb(1)N6 octahedra, edges with two equivalent Nb(3)N5 square pyramids, and edges with six equivalent Nb(2)N5 square pyramids. The corner-sharing octahedral tilt angles range from 0-5°. In the fifth Nb site, Nb(5) is bonded to one N(3), one N(5), and four equivalent N(2) atoms to form NbN6 octahedra that share corners with three equivalent Nb(4)N6 octahedra, corners with three equivalent Nb(3)N5 square pyramids,  an edgeedge with one Nb(4)N6 octahedra, edges with two equivalent Nb(5)N6 octahedra, edges with four equivalent Nb(1)N6 octahedra,  an edgeedge with one Nb(3)N5 square pyramid, and edges with four equivalent Nb(2)N5 square pyramids. The corner-sharing octahedral tilt angles range from 1-5°. There are five inequivalent N sites. In the first N site, N(5) is bonded to one Nb(4), one Nb(5), two equivalent Nb(1), and two equivalent Nb(2) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the second N site, N(1) is bonded to two equivalent Nb(2), two equivalent Nb(3), and two equivalent Nb(4) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 2-7°. In the third N site, N(2) is bonded to one Nb(1), one Nb(2), one Nb(3), one Nb(4), and two equivalent Nb(5) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the fourth N site, N(3) is bonded to one Nb(3), one Nb(5), two equivalent Nb(1), and two equivalent Nb(2) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the fifth N site, N(4) is bonded to two equivalent Nb(4) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 4-7°.
Nb12N11 crystallizes in the monoclinic C2/m space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent N(2), two equivalent N(3), and two equivalent N(5) atoms to form NbN6 octahedra that share corners with six equivalent Nb(2)N5 square pyramids, edges with two equivalent Nb(1)N6 octahedra, edges with two equivalent Nb(4)N6 octahedra, edges with four equivalent Nb(5)N6 octahedra, edges with two equivalent Nb(2)N5 square pyramids, and edges with two equivalent Nb(3)N5 square pyramids. Both Nb(1)-N(2) bond lengths are 2.20 Å. Both Nb(1)-N(3) bond lengths are 2.23 Å. Both Nb(1)-N(5) bond lengths are 2.27 Å. In the second Nb site, Nb(2) is bonded to one N(1), one N(2), one N(3), one N(4), and one N(5) atom to form NbN5 square pyramids that share corners with three equivalent Nb(1)N6 octahedra, corners with two equivalent Nb(3)N5 square pyramids, corners with four equivalent Nb(2)N5 square pyramids,  an edgeedge with one Nb(1)N6 octahedra, edges with two equivalent Nb(5)N6 octahedra, edges with three equivalent Nb(4)N6 octahedra,  an edgeedge with one Nb(2)N5 square pyramid, and  an edgeedge with one Nb(3)N5 square pyramid. The corner-sharing octahedral tilt angles range from 3-4°. The Nb(2)-N(1) bond length is 2.23 Å. The Nb(2)-N(2) bond length is 2.20 Å. The Nb(2)-N(3) bond length is 2.22 Å. The Nb(2)-N(4) bond length is 2.22 Å. The Nb(2)-N(5) bond length is 2.31 Å. In the third Nb site, Nb(3) is bonded to one N(3), two equivalent N(1), and two equivalent N(2) atoms to form NbN5 square pyramids that share corners with two equivalent Nb(4)N6 octahedra, corners with three equivalent Nb(5)N6 octahedra, corners with four equivalent Nb(2)N5 square pyramids,  an edgeedge with one Nb(5)N6 octahedra, edges with two equivalent Nb(1)N6 octahedra, edges with two equivalent Nb(4)N6 octahedra,  an edgeedge with one Nb(3)N5 square pyramid, and edges with two equivalent Nb(2)N5 square pyramids. The corner-sharing octahedral tilt angles range from 0-4°. The Nb(3)-N(3) bond length is 2.29 Å. Both Nb(3)-N(1) bond lengths are 2.23 Å. Both Nb(3)-N(2) bond lengths are 2.23 Å. In the fourth Nb site, Nb(4) is bonded to one N(4), one N(5), two equivalent N(1), and two equivalent N(2) atoms to form NbN6 octahedra that share  a cornercorner with one Nb(4)N6 octahedra, corners with three equivalent Nb(5)N6 octahedra, corners with two equivalent Nb(3)N5 square pyramids,  an edgeedge with one Nb(4)N6 octahedra,  an edgeedge with one Nb(5)N6 octahedra, edges with two equivalent Nb(1)N6 octahedra, edges with two equivalent Nb(3)N5 square pyramids, and edges with six equivalent Nb(2)N5 square pyramids. The corner-sharing octahedral tilt angles range from 0-5°. The Nb(4)-N(4) bond length is 2.18 Å. The Nb(4)-N(5) bond length is 2.21 Å. Both Nb(4)-N(1) bond lengths are 2.24 Å. Both Nb(4)-N(2) bond lengths are 2.20 Å. In the fifth Nb site, Nb(5) is bonded to one N(3), one N(5), and four equivalent N(2) atoms to form NbN6 octahedra that share corners with three equivalent Nb(4)N6 octahedra, corners with three equivalent Nb(3)N5 square pyramids,  an edgeedge with one Nb(4)N6 octahedra, edges with two equivalent Nb(5)N6 octahedra, edges with four equivalent Nb(1)N6 octahedra,  an edgeedge with one Nb(3)N5 square pyramid, and edges with four equivalent Nb(2)N5 square pyramids. The corner-sharing octahedral tilt angles range from 1-5°. The Nb(5)-N(3) bond length is 2.27 Å. The Nb(5)-N(5) bond length is 2.23 Å. There are two shorter (2.20 Å) and two longer (2.23 Å) Nb(5)-N(2) bond lengths. There are five inequivalent N sites. In the first N site, N(5) is bonded to one Nb(4), one Nb(5), two equivalent Nb(1), and two equivalent Nb(2) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the second N site, N(1) is bonded to two equivalent Nb(2), two equivalent Nb(3), and two equivalent Nb(4) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 2-7°. In the third N site, N(2) is bonded to one Nb(1), one Nb(2), one Nb(3), one Nb(4), and two equivalent Nb(5) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the fourth N site, N(3) is bonded to one Nb(3), one Nb(5), two equivalent Nb(1), and two equivalent Nb(2) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the fifth N site, N(4) is bonded to two equivalent Nb(4) and four equivalent Nb(2) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 4-7°.