Rb4Hg2Sn21 crystallizes in the orthorhombic Ama2 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 20-coordinate geometry to one Sn(2), one Sn(5), one Sn(7), one Sn(8), two equivalent Sn(1), two equivalent Sn(10), two equivalent Sn(11), two equivalent Sn(12), two equivalent Sn(3), two equivalent Sn(4), two equivalent Sn(6), and two equivalent Sn(9) atoms. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to two equivalent Sn(2), two equivalent Sn(5), two equivalent Sn(7), and two equivalent Sn(8) atoms. In the third Rb site, Rb(3) is bonded in a 6-coordinate geometry to two equivalent Sn(1), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(6) atoms. In the fourth Rb site, Rb(4) is bonded in a 6-coordinate geometry to two equivalent Sn(1), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(6) atoms. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to two equivalent Sn(3) and two equivalent Sn(6) atoms to form HgSn4 tetrahedra that share corners with two equivalent Sn(11)RbSn4 trigonal bipyramids. In the second Hg site, Hg(2) is bonded to one Sn(5), one Sn(8), and two equivalent Sn(4) atoms to form HgSn4 tetrahedra that share corners with two equivalent Sn(11)RbSn4 trigonal bipyramids. There are thirteen inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Sn(12), one Sn(13), one Sn(4), and one Sn(9) atom. In the second Sn site, Sn(2) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Sn(13), one Sn(8), and two equivalent Sn(9) atoms. In the third Sn site, Sn(3) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Hg(1), one Sn(11), one Sn(3), and one Sn(9) atom. In the fourth Sn site, Sn(4) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Hg(2), one Sn(1), one Sn(10), and one Sn(11) atom. In the fifth Sn site, Sn(5) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Hg(2), one Sn(7), and two equivalent Sn(10) atoms. In the sixth Sn site, Sn(6) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Hg(1), one Sn(10), one Sn(12), and one Sn(6) atom. In the seventh Sn site, Sn(7) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Sn(13), one Sn(5), and two equivalent Sn(11) atoms. In the eighth Sn site, Sn(8) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Hg(2), one Sn(2), and two equivalent Sn(12) atoms. In the ninth Sn site, Sn(9) is bonded in a 5-coordinate geometry to one Rb(1), one Sn(1), one Sn(2), one Sn(3), and one Sn(9) atom. In the tenth Sn site, Sn(10) is bonded in a 5-coordinate geometry to one Rb(1), one Sn(10), one Sn(4), one Sn(5), and one Sn(6) atom. In the eleventh Sn site, Sn(11) is bonded to one Rb(1), one Sn(12), one Sn(3), one Sn(4), and one Sn(7) atom to form distorted SnRbSn4 trigonal bipyramids that share  a cornercorner with one Hg(1)Sn4 tetrahedra,  a cornercorner with one Hg(2)Sn4 tetrahedra,  a cornercorner with one Sn(13)Sn4 tetrahedra, and  an edgeedge with one Sn(11)RbSn4 trigonal bipyramid. In the twelfth Sn site, Sn(12) is bonded in a 5-coordinate geometry to one Rb(1), one Sn(1), one Sn(11), one Sn(6), and one Sn(8) atom. In the thirteenth Sn site, Sn(13) is bonded to one Sn(2), one Sn(7), and two equivalent Sn(1) atoms to form corner-sharing SnSn4 tetrahedra.
Rb4Hg2Sn21 crystallizes in the orthorhombic Ama2 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 20-coordinate geometry to one Sn(2), one Sn(5), one Sn(7), one Sn(8), two equivalent Sn(1), two equivalent Sn(10), two equivalent Sn(11), two equivalent Sn(12), two equivalent Sn(3), two equivalent Sn(4), two equivalent Sn(6), and two equivalent Sn(9) atoms. The Rb(1)-Sn(2) bond length is 4.06 Å. The Rb(1)-Sn(5) bond length is 4.11 Å. The Rb(1)-Sn(7) bond length is 4.03 Å. The Rb(1)-Sn(8) bond length is 4.16 Å. Both Rb(1)-Sn(1) bond lengths are 4.04 Å. Both Rb(1)-Sn(10) bond lengths are 3.88 Å. Both Rb(1)-Sn(11) bond lengths are 3.91 Å. Both Rb(1)-Sn(12) bond lengths are 3.91 Å. Both Rb(1)-Sn(3) bond lengths are 4.15 Å. Both Rb(1)-Sn(4) bond lengths are 4.14 Å. Both Rb(1)-Sn(6) bond lengths are 4.09 Å. Both Rb(1)-Sn(9) bond lengths are 3.93 Å. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to two equivalent Sn(2), two equivalent Sn(5), two equivalent Sn(7), and two equivalent Sn(8) atoms. Both Rb(2)-Sn(2) bond lengths are 4.29 Å. Both Rb(2)-Sn(5) bond lengths are 3.98 Å. Both Rb(2)-Sn(7) bond lengths are 4.12 Å. Both Rb(2)-Sn(8) bond lengths are 4.14 Å. In the third Rb site, Rb(3) is bonded in a 6-coordinate geometry to two equivalent Sn(1), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(6) atoms. Both Rb(3)-Sn(1) bond lengths are 4.29 Å. Both Rb(3)-Sn(3) bond lengths are 4.10 Å. Both Rb(3)-Sn(4) bond lengths are 4.15 Å. Both Rb(3)-Sn(6) bond lengths are 3.96 Å. In the fourth Rb site, Rb(4) is bonded in a 6-coordinate geometry to two equivalent Sn(1), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(6) atoms. Both Rb(4)-Sn(1) bond lengths are 4.28 Å. Both Rb(4)-Sn(3) bond lengths are 4.11 Å. Both Rb(4)-Sn(4) bond lengths are 4.15 Å. Both Rb(4)-Sn(6) bond lengths are 3.96 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to two equivalent Sn(3) and two equivalent Sn(6) atoms to form HgSn4 tetrahedra that share corners with two equivalent Sn(11)RbSn4 trigonal bipyramids. Both Hg(1)-Sn(3) bond lengths are 2.82 Å. Both Hg(1)-Sn(6) bond lengths are 2.82 Å. In the second Hg site, Hg(2) is bonded to one Sn(5), one Sn(8), and two equivalent Sn(4) atoms to form HgSn4 tetrahedra that share corners with two equivalent Sn(11)RbSn4 trigonal bipyramids. The Hg(2)-Sn(5) bond length is 2.80 Å. The Hg(2)-Sn(8) bond length is 2.79 Å. Both Hg(2)-Sn(4) bond lengths are 2.79 Å. There are thirteen inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Sn(12), one Sn(13), one Sn(4), and one Sn(9) atom. The Sn(1)-Sn(12) bond length is 2.86 Å. The Sn(1)-Sn(13) bond length is 2.90 Å. The Sn(1)-Sn(4) bond length is 2.91 Å. The Sn(1)-Sn(9) bond length is 2.87 Å. In the second Sn site, Sn(2) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Sn(13), one Sn(8), and two equivalent Sn(9) atoms. The Sn(2)-Sn(13) bond length is 2.89 Å. The Sn(2)-Sn(8) bond length is 2.90 Å. Both Sn(2)-Sn(9) bond lengths are 2.86 Å. In the third Sn site, Sn(3) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Hg(1), one Sn(11), one Sn(3), and one Sn(9) atom. The Sn(3)-Sn(11) bond length is 2.87 Å. The Sn(3)-Sn(3) bond length is 2.90 Å. The Sn(3)-Sn(9) bond length is 2.87 Å. In the fourth Sn site, Sn(4) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Hg(2), one Sn(1), one Sn(10), and one Sn(11) atom. The Sn(4)-Sn(10) bond length is 2.87 Å. The Sn(4)-Sn(11) bond length is 2.87 Å. In the fifth Sn site, Sn(5) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Hg(2), one Sn(7), and two equivalent Sn(10) atoms. The Sn(5)-Sn(7) bond length is 2.92 Å. Both Sn(5)-Sn(10) bond lengths are 2.87 Å. In the sixth Sn site, Sn(6) is bonded in a 7-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), one Hg(1), one Sn(10), one Sn(12), and one Sn(6) atom. The Sn(6)-Sn(10) bond length is 2.87 Å. The Sn(6)-Sn(12) bond length is 2.87 Å. The Sn(6)-Sn(6) bond length is 2.91 Å. In the seventh Sn site, Sn(7) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Sn(13), one Sn(5), and two equivalent Sn(11) atoms. The Sn(7)-Sn(13) bond length is 2.90 Å. Both Sn(7)-Sn(11) bond lengths are 2.87 Å. In the eighth Sn site, Sn(8) is bonded in a 7-coordinate geometry to one Rb(1), two equivalent Rb(2), one Hg(2), one Sn(2), and two equivalent Sn(12) atoms. Both Sn(8)-Sn(12) bond lengths are 2.87 Å. In the ninth Sn site, Sn(9) is bonded in a 5-coordinate geometry to one Rb(1), one Sn(1), one Sn(2), one Sn(3), and one Sn(9) atom. The Sn(9)-Sn(9) bond length is 2.83 Å. In the tenth Sn site, Sn(10) is bonded in a 5-coordinate geometry to one Rb(1), one Sn(10), one Sn(4), one Sn(5), and one Sn(6) atom. The Sn(10)-Sn(10) bond length is 2.88 Å. In the eleventh Sn site, Sn(11) is bonded to one Rb(1), one Sn(12), one Sn(3), one Sn(4), and one Sn(7) atom to form distorted SnRbSn4 trigonal bipyramids that share  a cornercorner with one Hg(1)Sn4 tetrahedra,  a cornercorner with one Hg(2)Sn4 tetrahedra,  a cornercorner with one Sn(13)Sn4 tetrahedra, and  an edgeedge with one Sn(11)RbSn4 trigonal bipyramid. The Sn(11)-Sn(12) bond length is 2.85 Å. In the twelfth Sn site, Sn(12) is bonded in a 5-coordinate geometry to one Rb(1), one Sn(1), one Sn(11), one Sn(6), and one Sn(8) atom. In the thirteenth Sn site, Sn(13) is bonded to one Sn(2), one Sn(7), and two equivalent Sn(1) atoms to form corner-sharing SnSn4 tetrahedra.