Mn3(Ni10B3)2 crystallizes in the cubic Fm-3m space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to twelve equivalent Ni(2) atoms to form MnNi12 cuboctahedra that share edges with twenty-four equivalent Ni(1)MnNi6B3 tetrahedra and faces with eight equivalent Mn(2)Ni16 tetrahedra. In the second Mn site, Mn(2) is bonded to four equivalent Ni(1) and twelve equivalent Ni(2) atoms to form distorted MnNi16 tetrahedra that share edges with six equivalent Mn(2)Ni16 tetrahedra, edges with twelve equivalent Ni(1)MnNi6B3 tetrahedra, faces with four equivalent Mn(1)Ni12 cuboctahedra, and faces with four equivalent Ni(1)MnNi6B3 tetrahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one Mn(2), six equivalent Ni(2), and three equivalent B(1) atoms to form NiMnNi6B3 tetrahedra that share corners with three equivalent Ni(1)MnNi6B3 tetrahedra, edges with three equivalent Mn(1)Ni12 cuboctahedra, edges with three equivalent Mn(2)Ni16 tetrahedra, edges with three equivalent Ni(1)MnNi6B3 tetrahedra,  a faceface with one Mn(2)Ni16 tetrahedra, and faces with six equivalent Ni(1)MnNi6B3 tetrahedra. In the second Ni site, Ni(2) is bonded in a 14-coordinate geometry to one Mn(1), two equivalent Mn(2), four equivalent Ni(1), five equivalent Ni(2), and two equivalent B(1) atoms. B(1) is bonded in a 8-coordinate geometry to four equivalent Ni(1) and four equivalent Ni(2) atoms.
Mn3(Ni10B3)2 crystallizes in the cubic Fm-3m space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to twelve equivalent Ni(2) atoms to form MnNi12 cuboctahedra that share edges with twenty-four equivalent Ni(1)MnNi6B3 tetrahedra and faces with eight equivalent Mn(2)Ni16 tetrahedra. All Mn(1)-Ni(2) bond lengths are 2.50 Å. In the second Mn site, Mn(2) is bonded to four equivalent Ni(1) and twelve equivalent Ni(2) atoms to form distorted MnNi16 tetrahedra that share edges with six equivalent Mn(2)Ni16 tetrahedra, edges with twelve equivalent Ni(1)MnNi6B3 tetrahedra, faces with four equivalent Mn(1)Ni12 cuboctahedra, and faces with four equivalent Ni(1)MnNi6B3 tetrahedra. All Mn(2)-Ni(1) bond lengths are 2.37 Å. All Mn(2)-Ni(2) bond lengths are 2.86 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one Mn(2), six equivalent Ni(2), and three equivalent B(1) atoms to form NiMnNi6B3 tetrahedra that share corners with three equivalent Ni(1)MnNi6B3 tetrahedra, edges with three equivalent Mn(1)Ni12 cuboctahedra, edges with three equivalent Mn(2)Ni16 tetrahedra, edges with three equivalent Ni(1)MnNi6B3 tetrahedra,  a faceface with one Mn(2)Ni16 tetrahedra, and faces with six equivalent Ni(1)MnNi6B3 tetrahedra. All Ni(1)-Ni(2) bond lengths are 2.58 Å. All Ni(1)-B(1) bond lengths are 2.09 Å. In the second Ni site, Ni(2) is bonded in a 14-coordinate geometry to one Mn(1), two equivalent Mn(2), four equivalent Ni(1), five equivalent Ni(2), and two equivalent B(1) atoms. There is one shorter (2.36 Å) and four longer (2.50 Å) Ni(2)-Ni(2) bond lengths. Both Ni(2)-B(1) bond lengths are 2.06 Å. B(1) is bonded in a 8-coordinate geometry to four equivalent Ni(1) and four equivalent Ni(2) atoms.