Nb2Co2O9 crystallizes in the hexagonal P6_3/mcm space group. Nb(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with six equivalent Co(1)O6 octahedra and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. Co(1) is bonded to six equivalent O(1) atoms to form CoO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and edges with three equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1) and two equivalent Co(1) atoms. In the second O site, O(2) is bonded in an L-shaped geometry to two equivalent Nb(1) atoms.
Nb2Co2O9 crystallizes in the hexagonal P6_3/mcm space group. Nb(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with six equivalent Co(1)O6 octahedra and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Nb(1)-O(1) bond lengths are 2.10 Å. All Nb(1)-O(2) bond lengths are 1.95 Å. Co(1) is bonded to six equivalent O(1) atoms to form CoO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and edges with three equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Co(1)-O(1) bond lengths are 1.90 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1) and two equivalent Co(1) atoms. In the second O site, O(2) is bonded in an L-shaped geometry to two equivalent Nb(1) atoms.