Nb4Mo11B20 crystallizes in the orthorhombic Immm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent B(1), two equivalent B(4), four equivalent B(6), and four equivalent B(9) atoms to form a mixture of face and edge-sharing NbB12 cuboctahedra. In the second Nb site, Nb(2) is bonded to two equivalent B(2), two equivalent B(3), four equivalent B(7), and four equivalent B(8) atoms to form a mixture of face and edge-sharing NbB12 cuboctahedra. There are six inequivalent Mo sites. In the first Mo site, Mo(1) is bonded in a 7-coordinate geometry to one B(1), two equivalent B(10), and four equivalent B(5) atoms. In the second Mo site, Mo(2) is bonded in a 7-coordinate geometry to one B(2), two equivalent B(9), and four equivalent B(4) atoms. In the third Mo site, Mo(3) is bonded in a 7-coordinate geometry to two equivalent B(8) and five equivalent B(3) atoms. In the fourth Mo site, Mo(4) is bonded in a 7-coordinate geometry to one B(4), two equivalent B(7), and four equivalent B(2) atoms. In the fifth Mo site, Mo(5) is bonded in a 7-coordinate geometry to one B(5), two equivalent B(6), and four equivalent B(1) atoms. In the sixth Mo site, Mo(6) is bonded to four equivalent B(5) and eight equivalent B(10) atoms to form a mixture of face and edge-sharing MoB12 cuboctahedra. There are ten inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Nb(1), one Mo(1), four equivalent Mo(5), and two equivalent B(6) atoms. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Nb(2), one Mo(2), four equivalent Mo(4), and two equivalent B(7) atoms. In the third B site, B(3) is bonded in a 9-coordinate geometry to two equivalent Nb(2), five equivalent Mo(3), and two equivalent B(8) atoms. In the fourth B site, B(4) is bonded in a 9-coordinate geometry to two equivalent Nb(1), one Mo(4), four equivalent Mo(2), and two equivalent B(9) atoms. In the fifth B site, B(5) is bonded in a 9-coordinate geometry to one Mo(5), two equivalent Mo(6), four equivalent Mo(1), and two equivalent B(10) atoms. In the sixth B site, B(6) is bonded in a 9-coordinate geometry to four equivalent Nb(1), two equivalent Mo(5), one B(9), and two equivalent B(1) atoms. In the seventh B site, B(7) is bonded in a 9-coordinate geometry to four equivalent Nb(2), two equivalent Mo(4), one B(8), and two equivalent B(2) atoms. In the eighth B site, B(8) is bonded in a 9-coordinate geometry to four equivalent Nb(2), two equivalent Mo(3), one B(7), and two equivalent B(3) atoms. In the ninth B site, B(9) is bonded in a 9-coordinate geometry to four equivalent Nb(1), two equivalent Mo(2), one B(6), and two equivalent B(4) atoms. In the tenth B site, B(10) is bonded in a 9-coordinate geometry to two equivalent Mo(1), four equivalent Mo(6), one B(10), and two equivalent B(5) atoms.
Nb4Mo11B20 crystallizes in the orthorhombic Immm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent B(1), two equivalent B(4), four equivalent B(6), and four equivalent B(9) atoms to form a mixture of face and edge-sharing NbB12 cuboctahedra. Both Nb(1)-B(1) bond lengths are 2.49 Å. Both Nb(1)-B(4) bond lengths are 2.48 Å. All Nb(1)-B(6) bond lengths are 2.42 Å. All Nb(1)-B(9) bond lengths are 2.42 Å. In the second Nb site, Nb(2) is bonded to two equivalent B(2), two equivalent B(3), four equivalent B(7), and four equivalent B(8) atoms to form a mixture of face and edge-sharing NbB12 cuboctahedra. Both Nb(2)-B(2) bond lengths are 2.48 Å. Both Nb(2)-B(3) bond lengths are 2.48 Å. All Nb(2)-B(7) bond lengths are 2.42 Å. All Nb(2)-B(8) bond lengths are 2.42 Å. There are six inequivalent Mo sites. In the first Mo site, Mo(1) is bonded in a 7-coordinate geometry to one B(1), two equivalent B(10), and four equivalent B(5) atoms. The Mo(1)-B(1) bond length is 2.54 Å. Both Mo(1)-B(10) bond lengths are 2.30 Å. All Mo(1)-B(5) bond lengths are 2.33 Å. In the second Mo site, Mo(2) is bonded in a 7-coordinate geometry to one B(2), two equivalent B(9), and four equivalent B(4) atoms. The Mo(2)-B(2) bond length is 2.52 Å. Both Mo(2)-B(9) bond lengths are 2.32 Å. All Mo(2)-B(4) bond lengths are 2.34 Å. In the third Mo site, Mo(3) is bonded in a 7-coordinate geometry to two equivalent B(8) and five equivalent B(3) atoms. Both Mo(3)-B(8) bond lengths are 2.31 Å. There are four shorter (2.34 Å) and one longer (2.52 Å) Mo(3)-B(3) bond length. In the fourth Mo site, Mo(4) is bonded in a 7-coordinate geometry to one B(4), two equivalent B(7), and four equivalent B(2) atoms. The Mo(4)-B(4) bond length is 2.51 Å. Both Mo(4)-B(7) bond lengths are 2.32 Å. All Mo(4)-B(2) bond lengths are 2.34 Å. In the fifth Mo site, Mo(5) is bonded in a 7-coordinate geometry to one B(5), two equivalent B(6), and four equivalent B(1) atoms. The Mo(5)-B(5) bond length is 2.51 Å. Both Mo(5)-B(6) bond lengths are 2.32 Å. All Mo(5)-B(1) bond lengths are 2.34 Å. In the sixth Mo site, Mo(6) is bonded to four equivalent B(5) and eight equivalent B(10) atoms to form a mixture of face and edge-sharing MoB12 cuboctahedra. All Mo(6)-B(5) bond lengths are 2.48 Å. All Mo(6)-B(10) bond lengths are 2.41 Å. There are ten inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Nb(1), one Mo(1), four equivalent Mo(5), and two equivalent B(6) atoms. Both B(1)-B(6) bond lengths are 1.83 Å. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Nb(2), one Mo(2), four equivalent Mo(4), and two equivalent B(7) atoms. Both B(2)-B(7) bond lengths are 1.83 Å. In the third B site, B(3) is bonded in a 9-coordinate geometry to two equivalent Nb(2), five equivalent Mo(3), and two equivalent B(8) atoms. Both B(3)-B(8) bond lengths are 1.83 Å. In the fourth B site, B(4) is bonded in a 9-coordinate geometry to two equivalent Nb(1), one Mo(4), four equivalent Mo(2), and two equivalent B(9) atoms. Both B(4)-B(9) bond lengths are 1.83 Å. In the fifth B site, B(5) is bonded in a 9-coordinate geometry to one Mo(5), two equivalent Mo(6), four equivalent Mo(1), and two equivalent B(10) atoms. Both B(5)-B(10) bond lengths are 1.84 Å. In the sixth B site, B(6) is bonded in a 9-coordinate geometry to four equivalent Nb(1), two equivalent Mo(5), one B(9), and two equivalent B(1) atoms. The B(6)-B(9) bond length is 1.85 Å. In the seventh B site, B(7) is bonded in a 9-coordinate geometry to four equivalent Nb(2), two equivalent Mo(4), one B(8), and two equivalent B(2) atoms. The B(7)-B(8) bond length is 1.85 Å. In the eighth B site, B(8) is bonded in a 9-coordinate geometry to four equivalent Nb(2), two equivalent Mo(3), one B(7), and two equivalent B(3) atoms. In the ninth B site, B(9) is bonded in a 9-coordinate geometry to four equivalent Nb(1), two equivalent Mo(2), one B(6), and two equivalent B(4) atoms. In the tenth B site, B(10) is bonded in a 9-coordinate geometry to two equivalent Mo(1), four equivalent Mo(6), one B(10), and two equivalent B(5) atoms. The B(10)-B(10) bond length is 1.81 Å.