Mo9Se11 crystallizes in the orthorhombic Cmcm space group. There are four inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one Se(1), one Se(3), one Se(4), and two equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing MoSe5 square pyramids. In the second Mo site, Mo(2) is bonded to one Se(1), one Se(3), one Se(5), and two equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing MoSe5 square pyramids. In the third Mo site, Mo(3) is bonded in a distorted see-saw-like geometry to two equivalent Se(3) and two equivalent Se(4) atoms. In the fourth Mo site, Mo(4) is bonded in a distorted see-saw-like geometry to one Se(4), one Se(5), and two equivalent Se(2) atoms. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a 3-coordinate geometry to one Mo(2) and two equivalent Mo(1) atoms. In the second Se site, Se(2) is bonded in a 4-coordinate geometry to one Mo(2), one Mo(4), and two equivalent Mo(1) atoms. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one Mo(2), one Mo(3), and two equivalent Mo(1) atoms. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to one Mo(3), one Mo(4), and two equivalent Mo(1) atoms. In the fifth Se site, Se(5) is bonded in a 4-coordinate geometry to two equivalent Mo(2) and two equivalent Mo(4) atoms.
Mo9Se11 crystallizes in the orthorhombic Cmcm space group. There are four inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one Se(1), one Se(3), one Se(4), and two equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing MoSe5 square pyramids. The Mo(1)-Se(1) bond length is 2.56 Å. The Mo(1)-Se(3) bond length is 2.61 Å. The Mo(1)-Se(4) bond length is 2.73 Å. Both Mo(1)-Se(2) bond lengths are 2.63 Å. In the second Mo site, Mo(2) is bonded to one Se(1), one Se(3), one Se(5), and two equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing MoSe5 square pyramids. The Mo(2)-Se(1) bond length is 2.52 Å. The Mo(2)-Se(3) bond length is 2.68 Å. The Mo(2)-Se(5) bond length is 2.69 Å. Both Mo(2)-Se(2) bond lengths are 2.60 Å. In the third Mo site, Mo(3) is bonded in a distorted see-saw-like geometry to two equivalent Se(3) and two equivalent Se(4) atoms. Both Mo(3)-Se(3) bond lengths are 2.55 Å. Both Mo(3)-Se(4) bond lengths are 2.60 Å. In the fourth Mo site, Mo(4) is bonded in a distorted see-saw-like geometry to one Se(4), one Se(5), and two equivalent Se(2) atoms. The Mo(4)-Se(4) bond length is 2.56 Å. The Mo(4)-Se(5) bond length is 2.60 Å. Both Mo(4)-Se(2) bond lengths are 2.57 Å. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a 3-coordinate geometry to one Mo(2) and two equivalent Mo(1) atoms. In the second Se site, Se(2) is bonded in a 4-coordinate geometry to one Mo(2), one Mo(4), and two equivalent Mo(1) atoms. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one Mo(2), one Mo(3), and two equivalent Mo(1) atoms. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to one Mo(3), one Mo(4), and two equivalent Mo(1) atoms. In the fifth Se site, Se(5) is bonded in a 4-coordinate geometry to two equivalent Mo(2) and two equivalent Mo(4) atoms.