Hf(Nb2B3)4 crystallizes in the orthorhombic Immm space group. Hf(1) is bonded to four equivalent B(6) and eight equivalent B(3) atoms to form a mixture of edge and face-sharing HfB12 cuboctahedra. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to one B(4), two equivalent B(3), and four equivalent B(6) atoms. In the second Nb site, Nb(2) is bonded in a 7-coordinate geometry to two equivalent B(2) and five equivalent B(5) atoms. In the third Nb site, Nb(3) is bonded in a 7-coordinate geometry to one B(6), two equivalent B(1), and four equivalent B(4) atoms. In the fourth Nb site, Nb(4) is bonded to two equivalent B(4), two equivalent B(5), four equivalent B(1), and four equivalent B(2) atoms to form a mixture of edge and face-sharing NbB12 cuboctahedra. There are six inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Nb(3), four equivalent Nb(4), one B(2), and two equivalent B(4) atoms. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Nb(2), four equivalent Nb(4), one B(1), and two equivalent B(5) atoms. In the third B site, B(3) is bonded in a 9-coordinate geometry to four equivalent Hf(1), two equivalent Nb(1), one B(3), and two equivalent B(6) atoms. In the fourth B site, B(4) is bonded in a 9-coordinate geometry to one Nb(1), two equivalent Nb(4), four equivalent Nb(3), and two equivalent B(1) atoms. In the fifth B site, B(5) is bonded in a 9-coordinate geometry to two equivalent Nb(4), five equivalent Nb(2), and two equivalent B(2) atoms. In the sixth B site, B(6) is bonded in a 9-coordinate geometry to two equivalent Hf(1), one Nb(3), four equivalent Nb(1), and two equivalent B(3) atoms.
Hf(Nb2B3)4 crystallizes in the orthorhombic Immm space group. Hf(1) is bonded to four equivalent B(6) and eight equivalent B(3) atoms to form a mixture of edge and face-sharing HfB12 cuboctahedra. All Hf(1)-B(6) bond lengths are 2.53 Å. All Hf(1)-B(3) bond lengths are 2.48 Å. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to one B(4), two equivalent B(3), and four equivalent B(6) atoms. The Nb(1)-B(4) bond length is 2.58 Å. Both Nb(1)-B(3) bond lengths are 2.40 Å. All Nb(1)-B(6) bond lengths are 2.42 Å. In the second Nb site, Nb(2) is bonded in a 7-coordinate geometry to two equivalent B(2) and five equivalent B(5) atoms. Both Nb(2)-B(2) bond lengths are 2.39 Å. There are four shorter (2.42 Å) and one longer (2.59 Å) Nb(2)-B(5) bond length. In the third Nb site, Nb(3) is bonded in a 7-coordinate geometry to one B(6), two equivalent B(1), and four equivalent B(4) atoms. The Nb(3)-B(6) bond length is 2.58 Å. Both Nb(3)-B(1) bond lengths are 2.39 Å. All Nb(3)-B(4) bond lengths are 2.42 Å. In the fourth Nb site, Nb(4) is bonded to two equivalent B(4), two equivalent B(5), four equivalent B(1), and four equivalent B(2) atoms to form a mixture of edge and face-sharing NbB12 cuboctahedra. Both Nb(4)-B(4) bond lengths are 2.51 Å. Both Nb(4)-B(5) bond lengths are 2.51 Å. All Nb(4)-B(1) bond lengths are 2.48 Å. All Nb(4)-B(2) bond lengths are 2.48 Å. There are six inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Nb(3), four equivalent Nb(4), one B(2), and two equivalent B(4) atoms. The B(1)-B(2) bond length is 1.82 Å. Both B(1)-B(4) bond lengths are 1.85 Å. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Nb(2), four equivalent Nb(4), one B(1), and two equivalent B(5) atoms. Both B(2)-B(5) bond lengths are 1.85 Å. In the third B site, B(3) is bonded in a 9-coordinate geometry to four equivalent Hf(1), two equivalent Nb(1), one B(3), and two equivalent B(6) atoms. The B(3)-B(3) bond length is 1.84 Å. Both B(3)-B(6) bond lengths are 1.85 Å. In the fourth B site, B(4) is bonded in a 9-coordinate geometry to one Nb(1), two equivalent Nb(4), four equivalent Nb(3), and two equivalent B(1) atoms. In the fifth B site, B(5) is bonded in a 9-coordinate geometry to two equivalent Nb(4), five equivalent Nb(2), and two equivalent B(2) atoms. In the sixth B site, B(6) is bonded in a 9-coordinate geometry to two equivalent Hf(1), one Nb(3), four equivalent Nb(1), and two equivalent B(3) atoms.