U2Ni21B6 crystallizes in the cubic Fm-3m space group. U(1) is bonded in a distorted tetrahedral geometry to four equivalent Ni(2) atoms. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted bent 150 degrees geometry to one Ni(3) and two equivalent B(1) atoms. In the second Ni site, Ni(2) is bonded to one U(1) and three equivalent B(1) atoms to form a mixture of distorted corner and edge-sharing NiUB3 tetrahedra. In the third Ni site, Ni(3) is bonded in a cuboctahedral geometry to twelve equivalent Ni(1) atoms. B(1) is bonded in a 8-coordinate geometry to four equivalent Ni(1) and four equivalent Ni(2) atoms.
U2Ni21B6 crystallizes in the cubic Fm-3m space group. U(1) is bonded in a distorted tetrahedral geometry to four equivalent Ni(2) atoms. All U(1)-Ni(2) bond lengths are 2.47 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted bent 150 degrees geometry to one Ni(3) and two equivalent B(1) atoms. The Ni(1)-Ni(3) bond length is 2.54 Å. Both Ni(1)-B(1) bond lengths are 2.06 Å. In the second Ni site, Ni(2) is bonded to one U(1) and three equivalent B(1) atoms to form a mixture of distorted corner and edge-sharing NiUB3 tetrahedra. All Ni(2)-B(1) bond lengths are 2.13 Å. In the third Ni site, Ni(3) is bonded in a cuboctahedral geometry to twelve equivalent Ni(1) atoms. B(1) is bonded in a 8-coordinate geometry to four equivalent Ni(1) and four equivalent Ni(2) atoms.