Ni2B is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Ni+1.50+ is bonded in a 4-coordinate geometry to four equivalent B3- atoms. All Ni–B bond lengths are 2.13 Å. B3- is bonded in a 10-coordinate geometry to eight equivalent Ni+1.50+ and two equivalent B3- atoms. Both B–B bond lengths are 2.13 Å.