K4Zn2Sn21 crystallizes in the orthorhombic Ama2 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent Sn(5), two equivalent Sn(8), and two equivalent Sn(9) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to two equivalent Sn(10), two equivalent Sn(11), and two equivalent Sn(12) atoms. In the third K site, K(3) is bonded in a 6-coordinate geometry to two equivalent Sn(5), two equivalent Sn(8), and two equivalent Sn(9) atoms. In the fourth K site, K(4) is bonded in a 12-coordinate geometry to one Sn(12), one Sn(7), two equivalent Sn(1), two equivalent Sn(2), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(6) atoms. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to two equivalent Sn(5) and two equivalent Sn(8) atoms to form ZnSn4 tetrahedra that share corners with two equivalent Sn(1)KSn4 trigonal bipyramids, corners with two equivalent Sn(2)KSn4 trigonal bipyramids, corners with two equivalent Sn(3)KSn4 trigonal bipyramids, and corners with two equivalent Sn(4)KSn4 trigonal bipyramids. In the second Zn site, Zn(2) is bonded to one Sn(10), one Sn(11), and two equivalent Sn(9) atoms to form ZnSn4 tetrahedra that share corners with two equivalent Sn(3)KSn4 trigonal bipyramids, corners with two equivalent Sn(4)KSn4 trigonal bipyramids, and corners with four equivalent Sn(2)KSn4 trigonal bipyramids. There are thirteen inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one K(4), one Sn(1), one Sn(5), one Sn(6), and one Sn(7) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra, corners with two equivalent Sn(13)Sn4 tetrahedra,  a cornercorner with one Sn(3)KSn4 trigonal bipyramid,  a cornercorner with one Sn(4)KSn4 trigonal bipyramid, corners with two equivalent Sn(2)KSn4 trigonal bipyramids,  an edgeedge with one Sn(1)KSn4 trigonal bipyramid,  an edgeedge with one Sn(3)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(4)KSn4 trigonal bipyramid. In the second Sn site, Sn(2) is bonded to one K(4), one Sn(10), one Sn(2), one Sn(8), and one Sn(9) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra, corners with two equivalent Zn(2)Sn4 tetrahedra,  a cornercorner with one Sn(3)KSn4 trigonal bipyramid,  a cornercorner with one Sn(4)KSn4 trigonal bipyramid, corners with two equivalent Sn(1)KSn4 trigonal bipyramids,  an edgeedge with one Sn(2)KSn4 trigonal bipyramid,  an edgeedge with one Sn(3)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(4)KSn4 trigonal bipyramid. In the third Sn site, Sn(3) is bonded to one K(4), one Sn(11), one Sn(4), one Sn(6), and one Sn(8) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra,  a cornercorner with one Zn(2)Sn4 tetrahedra,  a cornercorner with one Sn(13)Sn4 tetrahedra,  a cornercorner with one Sn(1)KSn4 trigonal bipyramid,  a cornercorner with one Sn(2)KSn4 trigonal bipyramid, corners with two equivalent Sn(4)KSn4 trigonal bipyramids,  an edgeedge with one Sn(1)KSn4 trigonal bipyramid,  an edgeedge with one Sn(2)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(3)KSn4 trigonal bipyramid. In the fourth Sn site, Sn(4) is bonded to one K(4), one Sn(12), one Sn(3), one Sn(5), and one Sn(9) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra,  a cornercorner with one Zn(2)Sn4 tetrahedra,  a cornercorner with one Sn(13)Sn4 tetrahedra,  a cornercorner with one Sn(1)KSn4 trigonal bipyramid,  a cornercorner with one Sn(2)KSn4 trigonal bipyramid, corners with two equivalent Sn(3)KSn4 trigonal bipyramids,  an edgeedge with one Sn(1)KSn4 trigonal bipyramid,  an edgeedge with one Sn(2)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(4)KSn4 trigonal bipyramid. In the fifth Sn site, Sn(5) is bonded in a distorted single-bond geometry to one K(1), one K(3), one Zn(1), one Sn(1), and one Sn(4) atom. In the sixth Sn site, Sn(6) is bonded in a 5-coordinate geometry to one K(4), one Sn(1), one Sn(13), one Sn(3), and one Sn(9) atom. In the seventh Sn site, Sn(7) is bonded in a 5-coordinate geometry to one K(4), one Sn(11), one Sn(13), and two equivalent Sn(1) atoms. In the eighth Sn site, Sn(8) is bonded in a distorted single-bond geometry to one K(1), one K(3), one Zn(1), one Sn(2), and one Sn(3) atom. In the ninth Sn site, Sn(9) is bonded in a distorted single-bond geometry to one K(1), one K(3), one Zn(2), one Sn(2), one Sn(4), and one Sn(6) atom. In the tenth Sn site, Sn(10) is bonded in a distorted single-bond geometry to two equivalent K(2), one Zn(2), one Sn(12), and two equivalent Sn(2) atoms. In the eleventh Sn site, Sn(11) is bonded in a distorted single-bond geometry to two equivalent K(2), one Zn(2), one Sn(7), and two equivalent Sn(3) atoms. In the twelfth Sn site, Sn(12) is bonded in a 7-coordinate geometry to one K(4), two equivalent K(2), one Sn(10), one Sn(13), and two equivalent Sn(4) atoms. In the thirteenth Sn site, Sn(13) is bonded to one Sn(12), one Sn(7), and two equivalent Sn(6) atoms to form corner-sharing SnSn4 tetrahedra.
K4Zn2Sn21 crystallizes in the orthorhombic Ama2 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent Sn(5), two equivalent Sn(8), and two equivalent Sn(9) atoms. Both K(1)-Sn(5) bond lengths are 4.02 Å. Both K(1)-Sn(8) bond lengths are 3.85 Å. Both K(1)-Sn(9) bond lengths are 4.06 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to two equivalent Sn(10), two equivalent Sn(11), and two equivalent Sn(12) atoms. Both K(2)-Sn(10) bond lengths are 3.85 Å. Both K(2)-Sn(11) bond lengths are 4.07 Å. Both K(2)-Sn(12) bond lengths are 4.04 Å. In the third K site, K(3) is bonded in a 6-coordinate geometry to two equivalent Sn(5), two equivalent Sn(8), and two equivalent Sn(9) atoms. Both K(3)-Sn(5) bond lengths are 4.02 Å. Both K(3)-Sn(8) bond lengths are 3.84 Å. Both K(3)-Sn(9) bond lengths are 4.05 Å. In the fourth K site, K(4) is bonded in a 12-coordinate geometry to one Sn(12), one Sn(7), two equivalent Sn(1), two equivalent Sn(2), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(6) atoms. The K(4)-Sn(12) bond length is 3.96 Å. The K(4)-Sn(7) bond length is 4.03 Å. Both K(4)-Sn(1) bond lengths are 3.89 Å. Both K(4)-Sn(2) bond lengths are 3.80 Å. Both K(4)-Sn(3) bond lengths are 3.84 Å. Both K(4)-Sn(4) bond lengths are 3.86 Å. Both K(4)-Sn(6) bond lengths are 3.99 Å. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to two equivalent Sn(5) and two equivalent Sn(8) atoms to form ZnSn4 tetrahedra that share corners with two equivalent Sn(1)KSn4 trigonal bipyramids, corners with two equivalent Sn(2)KSn4 trigonal bipyramids, corners with two equivalent Sn(3)KSn4 trigonal bipyramids, and corners with two equivalent Sn(4)KSn4 trigonal bipyramids. Both Zn(1)-Sn(5) bond lengths are 2.68 Å. Both Zn(1)-Sn(8) bond lengths are 2.69 Å. In the second Zn site, Zn(2) is bonded to one Sn(10), one Sn(11), and two equivalent Sn(9) atoms to form ZnSn4 tetrahedra that share corners with two equivalent Sn(3)KSn4 trigonal bipyramids, corners with two equivalent Sn(4)KSn4 trigonal bipyramids, and corners with four equivalent Sn(2)KSn4 trigonal bipyramids. The Zn(2)-Sn(10) bond length is 2.66 Å. The Zn(2)-Sn(11) bond length is 2.66 Å. Both Zn(2)-Sn(9) bond lengths are 2.66 Å. There are thirteen inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one K(4), one Sn(1), one Sn(5), one Sn(6), and one Sn(7) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra, corners with two equivalent Sn(13)Sn4 tetrahedra,  a cornercorner with one Sn(3)KSn4 trigonal bipyramid,  a cornercorner with one Sn(4)KSn4 trigonal bipyramid, corners with two equivalent Sn(2)KSn4 trigonal bipyramids,  an edgeedge with one Sn(1)KSn4 trigonal bipyramid,  an edgeedge with one Sn(3)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(4)KSn4 trigonal bipyramid. The Sn(1)-Sn(1) bond length is 2.82 Å. The Sn(1)-Sn(5) bond length is 2.86 Å. The Sn(1)-Sn(6) bond length is 2.85 Å. The Sn(1)-Sn(7) bond length is 2.85 Å. In the second Sn site, Sn(2) is bonded to one K(4), one Sn(10), one Sn(2), one Sn(8), and one Sn(9) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra, corners with two equivalent Zn(2)Sn4 tetrahedra,  a cornercorner with one Sn(3)KSn4 trigonal bipyramid,  a cornercorner with one Sn(4)KSn4 trigonal bipyramid, corners with two equivalent Sn(1)KSn4 trigonal bipyramids,  an edgeedge with one Sn(2)KSn4 trigonal bipyramid,  an edgeedge with one Sn(3)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(4)KSn4 trigonal bipyramid. The Sn(2)-Sn(10) bond length is 2.87 Å. The Sn(2)-Sn(2) bond length is 2.85 Å. The Sn(2)-Sn(8) bond length is 2.87 Å. The Sn(2)-Sn(9) bond length is 2.87 Å. In the third Sn site, Sn(3) is bonded to one K(4), one Sn(11), one Sn(4), one Sn(6), and one Sn(8) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra,  a cornercorner with one Zn(2)Sn4 tetrahedra,  a cornercorner with one Sn(13)Sn4 tetrahedra,  a cornercorner with one Sn(1)KSn4 trigonal bipyramid,  a cornercorner with one Sn(2)KSn4 trigonal bipyramid, corners with two equivalent Sn(4)KSn4 trigonal bipyramids,  an edgeedge with one Sn(1)KSn4 trigonal bipyramid,  an edgeedge with one Sn(2)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(3)KSn4 trigonal bipyramid. The Sn(3)-Sn(11) bond length is 2.86 Å. The Sn(3)-Sn(4) bond length is 2.84 Å. The Sn(3)-Sn(6) bond length is 2.85 Å. The Sn(3)-Sn(8) bond length is 2.87 Å. In the fourth Sn site, Sn(4) is bonded to one K(4), one Sn(12), one Sn(3), one Sn(5), and one Sn(9) atom to form distorted SnKSn4 trigonal bipyramids that share  a cornercorner with one Zn(1)Sn4 tetrahedra,  a cornercorner with one Zn(2)Sn4 tetrahedra,  a cornercorner with one Sn(13)Sn4 tetrahedra,  a cornercorner with one Sn(1)KSn4 trigonal bipyramid,  a cornercorner with one Sn(2)KSn4 trigonal bipyramid, corners with two equivalent Sn(3)KSn4 trigonal bipyramids,  an edgeedge with one Sn(1)KSn4 trigonal bipyramid,  an edgeedge with one Sn(2)KSn4 trigonal bipyramid, and  an edgeedge with one Sn(4)KSn4 trigonal bipyramid. The Sn(4)-Sn(12) bond length is 2.86 Å. The Sn(4)-Sn(5) bond length is 2.86 Å. The Sn(4)-Sn(9) bond length is 2.87 Å. In the fifth Sn site, Sn(5) is bonded in a distorted single-bond geometry to one K(1), one K(3), one Zn(1), one Sn(1), and one Sn(4) atom. In the sixth Sn site, Sn(6) is bonded in a 5-coordinate geometry to one K(4), one Sn(1), one Sn(13), one Sn(3), and one Sn(9) atom. The Sn(6)-Sn(13) bond length is 2.88 Å. The Sn(6)-Sn(9) bond length is 2.89 Å. In the seventh Sn site, Sn(7) is bonded in a 5-coordinate geometry to one K(4), one Sn(11), one Sn(13), and two equivalent Sn(1) atoms. The Sn(7)-Sn(11) bond length is 2.88 Å. The Sn(7)-Sn(13) bond length is 2.87 Å. In the eighth Sn site, Sn(8) is bonded in a distorted single-bond geometry to one K(1), one K(3), one Zn(1), one Sn(2), and one Sn(3) atom. In the ninth Sn site, Sn(9) is bonded in a distorted single-bond geometry to one K(1), one K(3), one Zn(2), one Sn(2), one Sn(4), and one Sn(6) atom. In the tenth Sn site, Sn(10) is bonded in a distorted single-bond geometry to two equivalent K(2), one Zn(2), one Sn(12), and two equivalent Sn(2) atoms. The Sn(10)-Sn(12) bond length is 2.90 Å. In the eleventh Sn site, Sn(11) is bonded in a distorted single-bond geometry to two equivalent K(2), one Zn(2), one Sn(7), and two equivalent Sn(3) atoms. In the twelfth Sn site, Sn(12) is bonded in a 7-coordinate geometry to one K(4), two equivalent K(2), one Sn(10), one Sn(13), and two equivalent Sn(4) atoms. The Sn(12)-Sn(13) bond length is 2.88 Å. In the thirteenth Sn site, Sn(13) is bonded to one Sn(12), one Sn(7), and two equivalent Sn(6) atoms to form corner-sharing SnSn4 tetrahedra.