Rb4CO4 crystallizes in the trigonal R3m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a distorted trigonal planar geometry to one O(2) and two equivalent O(1) atoms. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. C(1) is bonded in a tetrahedral geometry to one O(2) and three equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Rb(1), two equivalent Rb(2), and one C(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Rb(1) and one C(1) atom.
Rb4CO4 crystallizes in the trigonal R3m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a distorted trigonal planar geometry to one O(2) and two equivalent O(1) atoms. The Rb(1)-O(2) bond length is 2.54 Å. Both Rb(1)-O(1) bond lengths are 2.82 Å. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. There are three shorter (2.76 Å) and three longer (3.46 Å) Rb(2)-O(1) bond lengths. C(1) is bonded in a tetrahedral geometry to one O(2) and three equivalent O(1) atoms. The C(1)-O(2) bond length is 1.40 Å. All C(1)-O(1) bond lengths are 1.45 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Rb(1), two equivalent Rb(2), and one C(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Rb(1) and one C(1) atom.