Rb4MgMo2(SO)4 crystallizes in the monoclinic C2 space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 6-coordinate geometry to two equivalent S(1), two equivalent S(2), one O(1), and one O(2) atom. In the second Rb site, Rb(2) is bonded in a 2-coordinate geometry to one S(2), two equivalent S(1), one O(1), and one O(2) atom. Mg(1) is bonded to two equivalent S(1) and two equivalent O(2) atoms to form distorted MgS2O2 tetrahedra that share corners with two equivalent Mo(1)S2O2 tetrahedra and  an edgeedge with one Mo(2)S2O2 tetrahedra. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to two equivalent S(1) and two equivalent O(1) atoms to form distorted MoS2O2 tetrahedra that share corners with two equivalent Mg(1)S2O2 tetrahedra. In the second Mo site, Mo(2) is bonded to two equivalent S(2) and two equivalent O(2) atoms to form distorted MoS2O2 tetrahedra that share  an edgeedge with one Mg(1)S2O2 tetrahedra. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 6-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), one Mg(1), and one Mo(1) atom. In the second S site, S(2) is bonded in a 4-coordinate geometry to one Rb(2), two equivalent Rb(1), and one Mo(2) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Rb(1), one Rb(2), and one Mo(1) atom. In the second O site, O(2) is bonded to one Rb(1), one Rb(2), one Mg(1), and one Mo(2) atom to form distorted edge-sharing ORb2MgMo tetrahedra.
Rb4MgMo2(SO)4 crystallizes in the monoclinic C2 space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 6-coordinate geometry to two equivalent S(1), two equivalent S(2), one O(1), and one O(2) atom. There is one shorter (3.61 Å) and one longer (3.68 Å) Rb(1)-S(1) bond length. There is one shorter (3.36 Å) and one longer (3.63 Å) Rb(1)-S(2) bond length. The Rb(1)-O(1) bond length is 2.76 Å. The Rb(1)-O(2) bond length is 2.87 Å. In the second Rb site, Rb(2) is bonded in a 2-coordinate geometry to one S(2), two equivalent S(1), one O(1), and one O(2) atom. The Rb(2)-S(2) bond length is 3.46 Å. There is one shorter (3.50 Å) and one longer (3.57 Å) Rb(2)-S(1) bond length. The Rb(2)-O(1) bond length is 2.74 Å. The Rb(2)-O(2) bond length is 2.82 Å. Mg(1) is bonded to two equivalent S(1) and two equivalent O(2) atoms to form distorted MgS2O2 tetrahedra that share corners with two equivalent Mo(1)S2O2 tetrahedra and  an edgeedge with one Mo(2)S2O2 tetrahedra. Both Mg(1)-S(1) bond lengths are 2.49 Å. Both Mg(1)-O(2) bond lengths are 2.02 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to two equivalent S(1) and two equivalent O(1) atoms to form distorted MoS2O2 tetrahedra that share corners with two equivalent Mg(1)S2O2 tetrahedra. Both Mo(1)-S(1) bond lengths are 2.40 Å. Both Mo(1)-O(1) bond lengths are 1.78 Å. In the second Mo site, Mo(2) is bonded to two equivalent S(2) and two equivalent O(2) atoms to form distorted MoS2O2 tetrahedra that share  an edgeedge with one Mg(1)S2O2 tetrahedra. Both Mo(2)-S(2) bond lengths are 2.26 Å. Both Mo(2)-O(2) bond lengths are 1.89 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 6-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), one Mg(1), and one Mo(1) atom. In the second S site, S(2) is bonded in a 4-coordinate geometry to one Rb(2), two equivalent Rb(1), and one Mo(2) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Rb(1), one Rb(2), and one Mo(1) atom. In the second O site, O(2) is bonded to one Rb(1), one Rb(2), one Mg(1), and one Mo(2) atom to form distorted edge-sharing ORb2MgMo tetrahedra.