Rb4P2Se9 crystallizes in the monoclinic C2/c space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(3), two equivalent Se(2), and four equivalent Se(4) atoms. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to one Se(1), one Se(4), one Se(5), two equivalent Se(2), and three equivalent Se(3) atoms. P(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. There are five inequivalent Se sites. In the first Se site, Se(5) is bonded in a distorted see-saw-like geometry to two equivalent Rb(2) and two equivalent Se(1) atoms. In the second Se site, Se(1) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(2), one P(1), and one Se(5) atom. In the third Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), and one P(1) atom. In the fourth Se site, Se(3) is bonded to one Rb(1), three equivalent Rb(2), and one P(1) atom to form a mixture of distorted corner and edge-sharing SeRb4P square pyramids. In the fifth Se site, Se(4) is bonded in a 6-coordinate geometry to one Rb(2), four equivalent Rb(1), and one P(1) atom.
Rb4P2Se9 crystallizes in the monoclinic C2/c space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(3), two equivalent Se(2), and four equivalent Se(4) atoms. The Rb(1)-Se(1) bond length is 3.71 Å. The Rb(1)-Se(3) bond length is 3.48 Å. There is one shorter (3.50 Å) and one longer (3.74 Å) Rb(1)-Se(2) bond length. There are a spread of Rb(1)-Se(4) bond distances ranging from 3.66-3.72 Å. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to one Se(1), one Se(4), one Se(5), two equivalent Se(2), and three equivalent Se(3) atoms. The Rb(2)-Se(1) bond length is 3.81 Å. The Rb(2)-Se(4) bond length is 3.74 Å. The Rb(2)-Se(5) bond length is 3.67 Å. There is one shorter (3.62 Å) and one longer (3.66 Å) Rb(2)-Se(2) bond length. There are a spread of Rb(2)-Se(3) bond distances ranging from 3.62-3.66 Å. P(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. The P(1)-Se(1) bond length is 2.35 Å. The P(1)-Se(2) bond length is 2.17 Å. The P(1)-Se(3) bond length is 2.16 Å. The P(1)-Se(4) bond length is 2.18 Å. There are five inequivalent Se sites. In the first Se site, Se(5) is bonded in a distorted see-saw-like geometry to two equivalent Rb(2) and two equivalent Se(1) atoms. Both Se(5)-Se(1) bond lengths are 2.35 Å. In the second Se site, Se(1) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(2), one P(1), and one Se(5) atom. In the third Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), and one P(1) atom. In the fourth Se site, Se(3) is bonded to one Rb(1), three equivalent Rb(2), and one P(1) atom to form a mixture of distorted corner and edge-sharing SeRb4P square pyramids. In the fifth Se site, Se(4) is bonded in a 6-coordinate geometry to one Rb(2), four equivalent Rb(1), and one P(1) atom.