Rb4MgU4Cr4O24 crystallizes in the triclinic P1 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a distorted rectangular see-saw-like geometry to one O(11), one O(16), one O(3), and one O(9) atom. In the second Rb site, Rb(2) is bonded in a 9-coordinate geometry to one Mg(1), one O(12), one O(15), one O(16), one O(2), one O(21), one O(24), one O(4), and one O(9) atom. In the third Rb site, Rb(3) is bonded in a 11-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(14), one O(17), one O(2), one O(23), one O(3), one O(4), and one O(7) atom. In the fourth Rb site, Rb(4) is bonded in a 10-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(14), one O(18), one O(3), one O(4), one O(8), and one O(9) atom. Mg(1) is bonded in a distorted trigonal planar geometry to one Rb(2), one O(1), one O(10), and one O(15) atom. There are four inequivalent U sites. In the first U site, U(1) is bonded to one O(16), one O(19), one O(22), one O(24), one O(5), one O(6), and one O(9) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(2)O7 pentagonal bipyramids,  a cornercorner with one Cr(3)O5 trigonal bipyramid,  a cornercorner with one Cr(4)O5 trigonal bipyramid,  an edgeedge with one U(3)O7 pentagonal bipyramid,  an edgeedge with one Cr(1)O5 trigonal bipyramid, and  an edgeedge with one Cr(2)O5 trigonal bipyramid. In the second U site, U(2) is bonded to one O(10), one O(15), one O(20), one O(21), one O(23), one O(5), and one O(6) atom to form UO7 pentagonal bipyramids that share corners with two equivalent U(1)O7 pentagonal bipyramids,  a cornercorner with one Cr(3)O5 trigonal bipyramid,  a cornercorner with one Cr(4)O5 trigonal bipyramid,  an edgeedge with one U(4)O7 pentagonal bipyramid,  an edgeedge with one Cr(1)O5 trigonal bipyramid, and  an edgeedge with one Cr(2)O5 trigonal bipyramid. In the third U site, U(3) is bonded to one O(11), one O(14), one O(17), one O(19), one O(22), one O(7), and one O(8) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(4)O7 pentagonal bipyramids,  a cornercorner with one Cr(1)O5 trigonal bipyramid,  a cornercorner with one Cr(2)O5 trigonal bipyramid,  an edgeedge with one U(1)O7 pentagonal bipyramid,  an edgeedge with one Cr(3)O5 trigonal bipyramid, and  an edgeedge with one Cr(4)O5 trigonal bipyramid. In the fourth U site, U(4) is bonded to one O(12), one O(13), one O(18), one O(21), one O(23), one O(7), and one O(8) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(3)O7 pentagonal bipyramids,  a cornercorner with one Cr(1)O5 trigonal bipyramid,  a cornercorner with one Cr(2)O5 trigonal bipyramid,  an edgeedge with one U(2)O7 pentagonal bipyramid,  an edgeedge with one Cr(3)O5 trigonal bipyramid, and  an edgeedge with one Cr(4)O5 trigonal bipyramid. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(18), one O(19), one O(20), and one O(5) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(3)O7 pentagonal bipyramid,  a cornercorner with one U(4)O7 pentagonal bipyramid,  an edgeedge with one U(1)O7 pentagonal bipyramid,  an edgeedge with one U(2)O7 pentagonal bipyramid, and  an edgeedge with one Cr(3)O5 trigonal bipyramid. In the second Cr site, Cr(2) is bonded to one O(17), one O(2), one O(23), one O(24), and one O(6) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(3)O7 pentagonal bipyramid,  a cornercorner with one U(4)O7 pentagonal bipyramid,  an edgeedge with one U(1)O7 pentagonal bipyramid,  an edgeedge with one U(2)O7 pentagonal bipyramid, and  an edgeedge with one Cr(4)O5 trigonal bipyramid. In the third Cr site, Cr(3) is bonded to one O(18), one O(20), one O(22), one O(3), and one O(7) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(1)O7 pentagonal bipyramid,  a cornercorner with one U(2)O7 pentagonal bipyramid,  an edgeedge with one U(3)O7 pentagonal bipyramid,  an edgeedge with one U(4)O7 pentagonal bipyramid, and  an edgeedge with one Cr(1)O5 trigonal bipyramid. In the fourth Cr site, Cr(4) is bonded to one O(17), one O(21), one O(24), one O(4), and one O(8) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(1)O7 pentagonal bipyramid,  a cornercorner with one U(2)O7 pentagonal bipyramid,  an edgeedge with one U(3)O7 pentagonal bipyramid,  an edgeedge with one U(4)O7 pentagonal bipyramid, and  an edgeedge with one Cr(2)O5 trigonal bipyramid. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Rb(4), one Mg(1), and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Rb(2), one Rb(3), and one Cr(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(3), one Rb(4), and one Cr(3) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Rb(2), one Rb(3), one Rb(4), and one Cr(4) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Cr(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Cr(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Rb(3), one U(3), one U(4), and one Cr(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Rb(4), one U(3), one U(4), and one Cr(4) atom. In the ninth O site, O(9) is bonded in a 1-coordinate geometry to one Rb(1), one Rb(2), one Rb(4), and one U(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Rb(3), one Mg(1), and one U(2) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(3), one Rb(4), and one U(3) atom. In the twelfth O site, O(12) is bonded in a single-bond geometry to one Rb(2), one Rb(3), one Rb(4), and one U(4) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one Rb(3), one Rb(4), and one U(4) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Rb(3), one Rb(4), and one U(3) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Rb(2), one Mg(1), and one U(2) atom. In the sixteenth O site, O(16) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(2), and one U(1) atom. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to one Rb(3), one U(3), one Cr(2), and one Cr(4) atom. In the eighteenth O site, O(18) is bonded in a 3-coordinate geometry to one Rb(4), one U(4), one Cr(1), and one Cr(3) atom. In the nineteenth O site, O(19) is bonded in a 3-coordinate geometry to one U(1), one U(3), and one Cr(1) atom. In the twentieth O site, O(20) is bonded in a 3-coordinate geometry to one U(2), one Cr(1), and one Cr(3) atom. In the twenty-first O site, O(21) is bonded in a 3-coordinate geometry to one Rb(2), one U(2), one U(4), and one Cr(4) atom. In the twenty-second O site, O(22) is bonded in a 3-coordinate geometry to one U(1), one U(3), and one Cr(3) atom. In the twenty-third O site, O(23) is bonded in a 3-coordinate geometry to one Rb(3), one U(2), one U(4), and one Cr(2) atom. In the twenty-fourth O site, O(24) is bonded in a distorted trigonal pyramidal geometry to one Rb(2), one U(1), one Cr(2), and one Cr(4) atom.
Rb4MgU4Cr4O24 crystallizes in the triclinic P1 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a distorted rectangular see-saw-like geometry to one O(11), one O(16), one O(3), and one O(9) atom. The Rb(1)-O(11) bond length is 2.74 Å. The Rb(1)-O(16) bond length is 2.85 Å. The Rb(1)-O(3) bond length is 2.91 Å. The Rb(1)-O(9) bond length is 2.72 Å. In the second Rb site, Rb(2) is bonded in a 9-coordinate geometry to one Mg(1), one O(12), one O(15), one O(16), one O(2), one O(21), one O(24), one O(4), and one O(9) atom. The Rb(2)-Mg(1) bond length is 3.32 Å. The Rb(2)-O(12) bond length is 3.28 Å. The Rb(2)-O(15) bond length is 3.37 Å. The Rb(2)-O(16) bond length is 2.86 Å. The Rb(2)-O(2) bond length is 2.82 Å. The Rb(2)-O(21) bond length is 3.44 Å. The Rb(2)-O(24) bond length is 2.82 Å. The Rb(2)-O(4) bond length is 2.79 Å. The Rb(2)-O(9) bond length is 3.46 Å. In the third Rb site, Rb(3) is bonded in a 11-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(14), one O(17), one O(2), one O(23), one O(3), one O(4), and one O(7) atom. The Rb(3)-O(10) bond length is 3.30 Å. The Rb(3)-O(11) bond length is 3.47 Å. The Rb(3)-O(12) bond length is 3.35 Å. The Rb(3)-O(13) bond length is 2.97 Å. The Rb(3)-O(14) bond length is 3.03 Å. The Rb(3)-O(17) bond length is 3.44 Å. The Rb(3)-O(2) bond length is 2.97 Å. The Rb(3)-O(23) bond length is 3.58 Å. The Rb(3)-O(3) bond length is 3.37 Å. The Rb(3)-O(4) bond length is 3.55 Å. The Rb(3)-O(7) bond length is 3.41 Å. In the fourth Rb site, Rb(4) is bonded in a 10-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(14), one O(18), one O(3), one O(4), one O(8), and one O(9) atom. The Rb(4)-O(1) bond length is 3.16 Å. The Rb(4)-O(11) bond length is 3.23 Å. The Rb(4)-O(12) bond length is 3.53 Å. The Rb(4)-O(13) bond length is 3.06 Å. The Rb(4)-O(14) bond length is 3.06 Å. The Rb(4)-O(18) bond length is 3.33 Å. The Rb(4)-O(3) bond length is 3.39 Å. The Rb(4)-O(4) bond length is 3.28 Å. The Rb(4)-O(8) bond length is 3.45 Å. The Rb(4)-O(9) bond length is 3.32 Å. Mg(1) is bonded in a distorted trigonal planar geometry to one Rb(2), one O(1), one O(10), and one O(15) atom. The Mg(1)-O(1) bond length is 1.93 Å. The Mg(1)-O(10) bond length is 1.93 Å. The Mg(1)-O(15) bond length is 1.92 Å. There are four inequivalent U sites. In the first U site, U(1) is bonded to one O(16), one O(19), one O(22), one O(24), one O(5), one O(6), and one O(9) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(2)O7 pentagonal bipyramids,  a cornercorner with one Cr(3)O5 trigonal bipyramid,  a cornercorner with one Cr(4)O5 trigonal bipyramid,  an edgeedge with one U(3)O7 pentagonal bipyramid,  an edgeedge with one Cr(1)O5 trigonal bipyramid, and  an edgeedge with one Cr(2)O5 trigonal bipyramid. The U(1)-O(16) bond length is 1.85 Å. The U(1)-O(19) bond length is 2.32 Å. The U(1)-O(22) bond length is 2.30 Å. The U(1)-O(24) bond length is 2.33 Å. The U(1)-O(5) bond length is 2.38 Å. The U(1)-O(6) bond length is 2.43 Å. The U(1)-O(9) bond length is 1.85 Å. In the second U site, U(2) is bonded to one O(10), one O(15), one O(20), one O(21), one O(23), one O(5), and one O(6) atom to form UO7 pentagonal bipyramids that share corners with two equivalent U(1)O7 pentagonal bipyramids,  a cornercorner with one Cr(3)O5 trigonal bipyramid,  a cornercorner with one Cr(4)O5 trigonal bipyramid,  an edgeedge with one U(4)O7 pentagonal bipyramid,  an edgeedge with one Cr(1)O5 trigonal bipyramid, and  an edgeedge with one Cr(2)O5 trigonal bipyramid. The U(2)-O(10) bond length is 1.96 Å. The U(2)-O(15) bond length is 1.95 Å. The U(2)-O(20) bond length is 2.35 Å. The U(2)-O(21) bond length is 2.27 Å. The U(2)-O(23) bond length is 2.18 Å. The U(2)-O(5) bond length is 2.31 Å. The U(2)-O(6) bond length is 2.31 Å. In the third U site, U(3) is bonded to one O(11), one O(14), one O(17), one O(19), one O(22), one O(7), and one O(8) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(4)O7 pentagonal bipyramids,  a cornercorner with one Cr(1)O5 trigonal bipyramid,  a cornercorner with one Cr(2)O5 trigonal bipyramid,  an edgeedge with one U(1)O7 pentagonal bipyramid,  an edgeedge with one Cr(3)O5 trigonal bipyramid, and  an edgeedge with one Cr(4)O5 trigonal bipyramid. The U(3)-O(11) bond length is 1.86 Å. The U(3)-O(14) bond length is 1.85 Å. The U(3)-O(17) bond length is 2.36 Å. The U(3)-O(19) bond length is 2.25 Å. The U(3)-O(22) bond length is 2.36 Å. The U(3)-O(7) bond length is 2.42 Å. The U(3)-O(8) bond length is 2.38 Å. In the fourth U site, U(4) is bonded to one O(12), one O(13), one O(18), one O(21), one O(23), one O(7), and one O(8) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(3)O7 pentagonal bipyramids,  a cornercorner with one Cr(1)O5 trigonal bipyramid,  a cornercorner with one Cr(2)O5 trigonal bipyramid,  an edgeedge with one U(2)O7 pentagonal bipyramid,  an edgeedge with one Cr(3)O5 trigonal bipyramid, and  an edgeedge with one Cr(4)O5 trigonal bipyramid. The U(4)-O(12) bond length is 1.85 Å. The U(4)-O(13) bond length is 1.84 Å. The U(4)-O(18) bond length is 2.38 Å. The U(4)-O(21) bond length is 2.38 Å. The U(4)-O(23) bond length is 2.29 Å. The U(4)-O(7) bond length is 2.36 Å. The U(4)-O(8) bond length is 2.37 Å. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(18), one O(19), one O(20), and one O(5) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(3)O7 pentagonal bipyramid,  a cornercorner with one U(4)O7 pentagonal bipyramid,  an edgeedge with one U(1)O7 pentagonal bipyramid,  an edgeedge with one U(2)O7 pentagonal bipyramid, and  an edgeedge with one Cr(3)O5 trigonal bipyramid. The Cr(1)-O(1) bond length is 1.76 Å. The Cr(1)-O(18) bond length is 1.87 Å. The Cr(1)-O(19) bond length is 1.93 Å. The Cr(1)-O(20) bond length is 2.00 Å. The Cr(1)-O(5) bond length is 1.84 Å. In the second Cr site, Cr(2) is bonded to one O(17), one O(2), one O(23), one O(24), and one O(6) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(3)O7 pentagonal bipyramid,  a cornercorner with one U(4)O7 pentagonal bipyramid,  an edgeedge with one U(1)O7 pentagonal bipyramid,  an edgeedge with one U(2)O7 pentagonal bipyramid, and  an edgeedge with one Cr(4)O5 trigonal bipyramid. The Cr(2)-O(17) bond length is 1.88 Å. The Cr(2)-O(2) bond length is 1.70 Å. The Cr(2)-O(23) bond length is 1.97 Å. The Cr(2)-O(24) bond length is 2.01 Å. The Cr(2)-O(6) bond length is 1.86 Å. In the third Cr site, Cr(3) is bonded to one O(18), one O(20), one O(22), one O(3), and one O(7) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(1)O7 pentagonal bipyramid,  a cornercorner with one U(2)O7 pentagonal bipyramid,  an edgeedge with one U(3)O7 pentagonal bipyramid,  an edgeedge with one U(4)O7 pentagonal bipyramid, and  an edgeedge with one Cr(1)O5 trigonal bipyramid. The Cr(3)-O(18) bond length is 1.93 Å. The Cr(3)-O(20) bond length is 1.89 Å. The Cr(3)-O(22) bond length is 1.86 Å. The Cr(3)-O(3) bond length is 1.62 Å. The Cr(3)-O(7) bond length is 1.85 Å. In the fourth Cr site, Cr(4) is bonded to one O(17), one O(21), one O(24), one O(4), and one O(8) atom to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one U(1)O7 pentagonal bipyramid,  a cornercorner with one U(2)O7 pentagonal bipyramid,  an edgeedge with one U(3)O7 pentagonal bipyramid,  an edgeedge with one U(4)O7 pentagonal bipyramid, and  an edgeedge with one Cr(2)O5 trigonal bipyramid. The Cr(4)-O(17) bond length is 1.93 Å. The Cr(4)-O(21) bond length is 1.90 Å. The Cr(4)-O(24) bond length is 1.87 Å. The Cr(4)-O(4) bond length is 1.62 Å. The Cr(4)-O(8) bond length is 1.83 Å. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Rb(4), one Mg(1), and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Rb(2), one Rb(3), and one Cr(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(3), one Rb(4), and one Cr(3) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Rb(2), one Rb(3), one Rb(4), and one Cr(4) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Cr(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Cr(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Rb(3), one U(3), one U(4), and one Cr(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Rb(4), one U(3), one U(4), and one Cr(4) atom. In the ninth O site, O(9) is bonded in a 1-coordinate geometry to one Rb(1), one Rb(2), one Rb(4), and one U(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Rb(3), one Mg(1), and one U(2) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(3), one Rb(4), and one U(3) atom. In the twelfth O site, O(12) is bonded in a single-bond geometry to one Rb(2), one Rb(3), one Rb(4), and one U(4) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one Rb(3), one Rb(4), and one U(4) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Rb(3), one Rb(4), and one U(3) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Rb(2), one Mg(1), and one U(2) atom. In the sixteenth O site, O(16) is bonded in a distorted single-bond geometry to one Rb(1), one Rb(2), and one U(1) atom. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to one Rb(3), one U(3), one Cr(2), and one Cr(4) atom. In the eighteenth O site, O(18) is bonded in a 3-coordinate geometry to one Rb(4), one U(4), one Cr(1), and one Cr(3) atom. In the nineteenth O site, O(19) is bonded in a 3-coordinate geometry to one U(1), one U(3), and one Cr(1) atom. In the twentieth O site, O(20) is bonded in a 3-coordinate geometry to one U(2), one Cr(1), and one Cr(3) atom. In the twenty-first O site, O(21) is bonded in a 3-coordinate geometry to one Rb(2), one U(2), one U(4), and one Cr(4) atom. In the twenty-second O site, O(22) is bonded in a 3-coordinate geometry to one U(1), one U(3), and one Cr(3) atom. In the twenty-third O site, O(23) is bonded in a 3-coordinate geometry to one Rb(3), one U(2), one U(4), and one Cr(2) atom. In the twenty-fourth O site, O(24) is bonded in a distorted trigonal pyramidal geometry to one Rb(2), one U(1), one Cr(2), and one Cr(4) atom.