K3TmCl6 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one Cl(1), one Cl(3), one Cl(5), one Cl(6), two equivalent Cl(2), and two equivalent Cl(4) atoms. In the second K site, K(2) is bonded in a 7-coordinate geometry to one Cl(2), one Cl(3), one Cl(5), two equivalent Cl(1), and two equivalent Cl(6) atoms. In the third K site, K(3) is bonded in a 8-coordinate geometry to one Cl(1), one Cl(2), one Cl(5), one Cl(6), two equivalent Cl(3), and two equivalent Cl(4) atoms. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in an octahedral geometry to two equivalent Cl(2), two equivalent Cl(3), and two equivalent Cl(4) atoms. In the second Tm site, Tm(2) is bonded in an octahedral geometry to two equivalent Cl(1), two equivalent Cl(5), and two equivalent Cl(6) atoms. There are six inequivalent Cl sites. In the first Cl site, Cl(5) is bonded to one K(1), one K(2), one K(3), and one Tm(2) atom to form distorted ClK3Tm trigonal pyramids that share corners with two equivalent Cl(3)K4Tm trigonal bipyramids, corners with two equivalent Cl(4)K4Tm trigonal bipyramids,  a cornercorner with one Cl(5)K3Tm trigonal pyramid,  an edgeedge with one Cl(3)K4Tm trigonal bipyramid, and  an edgeedge with one Cl(4)K4Tm trigonal bipyramid. In the second Cl site, Cl(6) is bonded in a 5-coordinate geometry to one K(1), one K(3), two equivalent K(2), and one Tm(2) atom. In the third Cl site, Cl(1) is bonded in a 5-coordinate geometry to one K(1), one K(3), two equivalent K(2), and one Tm(2) atom. In the fourth Cl site, Cl(2) is bonded in a 5-coordinate geometry to one K(2), one K(3), two equivalent K(1), and one Tm(1) atom. In the fifth Cl site, Cl(3) is bonded to one K(1), one K(2), two equivalent K(3), and one Tm(1) atom to form distorted ClK4Tm trigonal bipyramids that share corners with two equivalent Cl(4)K4Tm trigonal bipyramids, corners with three equivalent Cl(3)K4Tm trigonal bipyramids, corners with two equivalent Cl(5)K3Tm trigonal pyramids, edges with three equivalent Cl(4)K4Tm trigonal bipyramids, and  an edgeedge with one Cl(5)K3Tm trigonal pyramid. In the sixth Cl site, Cl(4) is bonded to two equivalent K(1), two equivalent K(3), and one Tm(1) atom to form distorted ClK4Tm trigonal bipyramids that share  a cornercorner with one Cl(4)K4Tm trigonal bipyramid, corners with two equivalent Cl(3)K4Tm trigonal bipyramids, corners with two equivalent Cl(5)K3Tm trigonal pyramids, edges with two equivalent Cl(4)K4Tm trigonal bipyramids, edges with three equivalent Cl(3)K4Tm trigonal bipyramids, and  an edgeedge with one Cl(5)K3Tm trigonal pyramid.
K3TmCl6 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one Cl(1), one Cl(3), one Cl(5), one Cl(6), two equivalent Cl(2), and two equivalent Cl(4) atoms. The K(1)-Cl(1) bond length is 3.24 Å. The K(1)-Cl(3) bond length is 3.09 Å. The K(1)-Cl(5) bond length is 3.00 Å. The K(1)-Cl(6) bond length is 3.60 Å. There is one shorter (3.36 Å) and one longer (3.56 Å) K(1)-Cl(2) bond length. There is one shorter (3.23 Å) and one longer (3.24 Å) K(1)-Cl(4) bond length. In the second K site, K(2) is bonded in a 7-coordinate geometry to one Cl(2), one Cl(3), one Cl(5), two equivalent Cl(1), and two equivalent Cl(6) atoms. The K(2)-Cl(2) bond length is 3.66 Å. The K(2)-Cl(3) bond length is 3.37 Å. The K(2)-Cl(5) bond length is 3.18 Å. There is one shorter (3.27 Å) and one longer (3.60 Å) K(2)-Cl(1) bond length. There is one shorter (3.19 Å) and one longer (3.43 Å) K(2)-Cl(6) bond length. In the third K site, K(3) is bonded in a 8-coordinate geometry to one Cl(1), one Cl(2), one Cl(5), one Cl(6), two equivalent Cl(3), and two equivalent Cl(4) atoms. The K(3)-Cl(1) bond length is 3.35 Å. The K(3)-Cl(2) bond length is 3.15 Å. The K(3)-Cl(5) bond length is 3.16 Å. The K(3)-Cl(6) bond length is 3.24 Å. There is one shorter (3.32 Å) and one longer (3.54 Å) K(3)-Cl(3) bond length. There is one shorter (3.16 Å) and one longer (3.20 Å) K(3)-Cl(4) bond length. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in an octahedral geometry to two equivalent Cl(2), two equivalent Cl(3), and two equivalent Cl(4) atoms. Both Tm(1)-Cl(2) bond lengths are 2.59 Å. Both Tm(1)-Cl(3) bond lengths are 2.60 Å. Both Tm(1)-Cl(4) bond lengths are 2.61 Å. In the second Tm site, Tm(2) is bonded in an octahedral geometry to two equivalent Cl(1), two equivalent Cl(5), and two equivalent Cl(6) atoms. Both Tm(2)-Cl(1) bond lengths are 2.56 Å. Both Tm(2)-Cl(5) bond lengths are 2.57 Å. Both Tm(2)-Cl(6) bond lengths are 2.63 Å. There are six inequivalent Cl sites. In the first Cl site, Cl(5) is bonded to one K(1), one K(2), one K(3), and one Tm(2) atom to form distorted ClK3Tm trigonal pyramids that share corners with two equivalent Cl(3)K4Tm trigonal bipyramids, corners with two equivalent Cl(4)K4Tm trigonal bipyramids,  a cornercorner with one Cl(5)K3Tm trigonal pyramid,  an edgeedge with one Cl(3)K4Tm trigonal bipyramid, and  an edgeedge with one Cl(4)K4Tm trigonal bipyramid. In the second Cl site, Cl(6) is bonded in a 5-coordinate geometry to one K(1), one K(3), two equivalent K(2), and one Tm(2) atom. In the third Cl site, Cl(1) is bonded in a 5-coordinate geometry to one K(1), one K(3), two equivalent K(2), and one Tm(2) atom. In the fourth Cl site, Cl(2) is bonded in a 5-coordinate geometry to one K(2), one K(3), two equivalent K(1), and one Tm(1) atom. In the fifth Cl site, Cl(3) is bonded to one K(1), one K(2), two equivalent K(3), and one Tm(1) atom to form distorted ClK4Tm trigonal bipyramids that share corners with two equivalent Cl(4)K4Tm trigonal bipyramids, corners with three equivalent Cl(3)K4Tm trigonal bipyramids, corners with two equivalent Cl(5)K3Tm trigonal pyramids, edges with three equivalent Cl(4)K4Tm trigonal bipyramids, and  an edgeedge with one Cl(5)K3Tm trigonal pyramid. In the sixth Cl site, Cl(4) is bonded to two equivalent K(1), two equivalent K(3), and one Tm(1) atom to form distorted ClK4Tm trigonal bipyramids that share  a cornercorner with one Cl(4)K4Tm trigonal bipyramid, corners with two equivalent Cl(3)K4Tm trigonal bipyramids, corners with two equivalent Cl(5)K3Tm trigonal pyramids, edges with two equivalent Cl(4)K4Tm trigonal bipyramids, edges with three equivalent Cl(3)K4Tm trigonal bipyramids, and  an edgeedge with one Cl(5)K3Tm trigonal pyramid.