Nb16N9 crystallizes in the orthorhombic Immm space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a linear geometry to two equivalent N(1) atoms. In the second Nb site, Nb(2) is bonded to one N(2) and four equivalent N(1) atoms to form corner-sharing NbN5 square pyramids. In the third Nb site, Nb(3) is bonded in a square co-planar geometry to four equivalent N(1) atoms. In the fourth Nb site, Nb(4) is bonded in a T-shaped geometry to one N(2) and two equivalent N(1) atoms. In the fifth Nb site, Nb(5) is bonded in a square co-planar geometry to four equivalent N(1) atoms. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Nb(1), one Nb(2), one Nb(4), one Nb(5), and two equivalent Nb(3) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the second N site, N(2) is bonded to two equivalent Nb(2) and four equivalent Nb(4) atoms to form edge-sharing NNb6 octahedra.
Nb16N9 crystallizes in the orthorhombic Immm space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a linear geometry to two equivalent N(1) atoms. Both Nb(1)-N(1) bond lengths are 2.22 Å. In the second Nb site, Nb(2) is bonded to one N(2) and four equivalent N(1) atoms to form corner-sharing NbN5 square pyramids. The Nb(2)-N(2) bond length is 2.16 Å. All Nb(2)-N(1) bond lengths are 2.18 Å. In the third Nb site, Nb(3) is bonded in a square co-planar geometry to four equivalent N(1) atoms. There are two shorter (2.16 Å) and two longer (2.19 Å) Nb(3)-N(1) bond lengths. In the fourth Nb site, Nb(4) is bonded in a T-shaped geometry to one N(2) and two equivalent N(1) atoms. The Nb(4)-N(2) bond length is 2.22 Å. Both Nb(4)-N(1) bond lengths are 2.23 Å. In the fifth Nb site, Nb(5) is bonded in a square co-planar geometry to four equivalent N(1) atoms. All Nb(5)-N(1) bond lengths are 2.18 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Nb(1), one Nb(2), one Nb(4), one Nb(5), and two equivalent Nb(3) atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the second N site, N(2) is bonded to two equivalent Nb(2) and four equivalent Nb(4) atoms to form edge-sharing NNb6 octahedra.