K2Mn(SnSe3)2 crystallizes in the tetragonal P4/ncc space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. In the second K site, K(2) is bonded in a 8-coordinate geometry to eight equivalent Se(2) atoms. Mn(1) is bonded to four equivalent Se(2) atoms to form MnSe4 tetrahedra that share edges with two equivalent Sn(1)Se4 tetrahedra. Sn(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form distorted SnSe4 tetrahedra that share  an edgeedge with one Mn(1)Se4 tetrahedra and  an edgeedge with one Sn(1)Se4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1) and two equivalent Sn(1) atoms to form a mixture of distorted corner and edge-sharing SeK2Sn2 trigonal pyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one K(1), two equivalent K(2), one Mn(1), and one Sn(1) atom.
K2Mn(SnSe3)2 crystallizes in the tetragonal P4/ncc space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. All K(1)-Se(1) bond lengths are 3.46 Å. All K(1)-Se(2) bond lengths are 3.58 Å. In the second K site, K(2) is bonded in a 8-coordinate geometry to eight equivalent Se(2) atoms. There are four shorter (3.46 Å) and four longer (3.71 Å) K(2)-Se(2) bond lengths. Mn(1) is bonded to four equivalent Se(2) atoms to form MnSe4 tetrahedra that share edges with two equivalent Sn(1)Se4 tetrahedra. All Mn(1)-Se(2) bond lengths are 2.58 Å. Sn(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form distorted SnSe4 tetrahedra that share  an edgeedge with one Mn(1)Se4 tetrahedra and  an edgeedge with one Sn(1)Se4 tetrahedra. Both Sn(1)-Se(1) bond lengths are 2.62 Å. Both Sn(1)-Se(2) bond lengths are 2.54 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1) and two equivalent Sn(1) atoms to form a mixture of distorted corner and edge-sharing SeK2Sn2 trigonal pyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one K(1), two equivalent K(2), one Mn(1), and one Sn(1) atom.