K2(TcSe2)3 crystallizes in the monoclinic C2/c space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent Se(3), two equivalent Se(4), and two equivalent Se(6) atoms. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. In the third K site, K(3) is bonded in a 7-coordinate geometry to one Se(3), one Se(4), one Se(6), two equivalent Se(2), and two equivalent Se(5) atoms. There are three inequivalent Tc sites. In the first Tc site, Tc(1) is bonded to one Se(1), one Se(2), one Se(3), one Se(4), and one Se(5) atom to form distorted edge-sharing TcSe5 square pyramids. In the second Tc site, Tc(2) is bonded to one Se(1), one Se(2), one Se(3), one Se(4), and one Se(6) atom to form a mixture of edge and corner-sharing TcSe5 square pyramids. In the third Tc site, Tc(3) is bonded to one Se(1), one Se(2), one Se(3), one Se(4), and one Se(6) atom to form a mixture of distorted edge and corner-sharing TcSe5 square pyramids. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to one K(2), one Tc(1), one Tc(2), and one Tc(3) atom. In the second Se site, Se(2) is bonded to two equivalent K(3), one Tc(1), one Tc(2), and one Tc(3) atom to form distorted SeK2Tc3 trigonal bipyramids that share corners with two equivalent Se(6)K3Tc2 trigonal bipyramids,  an edgeedge with one Se(2)K2Tc3 trigonal bipyramid, and  an edgeedge with one Se(6)K3Tc2 trigonal bipyramid. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to one K(1), one K(3), one Tc(1), one Tc(2), and one Tc(3) atom. In the fourth Se site, Se(4) is bonded in a 6-coordinate geometry to one K(1), one K(2), one K(3), one Tc(1), one Tc(2), and one Tc(3) atom. In the fifth Se site, Se(5) is bonded in a 5-coordinate geometry to one K(2), two equivalent K(3), one Tc(1), and one Se(5) atom. In the sixth Se site, Se(6) is bonded to one K(1), one K(2), one K(3), one Tc(2), and one Tc(3) atom to form distorted SeK3Tc2 trigonal bipyramids that share corners with two equivalent Se(2)K2Tc3 trigonal bipyramids,  an edgeedge with one Se(2)K2Tc3 trigonal bipyramid, and  an edgeedge with one Se(6)K3Tc2 trigonal bipyramid.
K2(TcSe2)3 crystallizes in the monoclinic C2/c space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent Se(3), two equivalent Se(4), and two equivalent Se(6) atoms. Both K(1)-Se(3) bond lengths are 3.35 Å. Both K(1)-Se(4) bond lengths are 3.61 Å. Both K(1)-Se(6) bond lengths are 3.27 Å. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. Both K(2)-Se(1) bond lengths are 3.29 Å. Both K(2)-Se(4) bond lengths are 3.57 Å. Both K(2)-Se(5) bond lengths are 3.33 Å. Both K(2)-Se(6) bond lengths are 3.29 Å. In the third K site, K(3) is bonded in a 7-coordinate geometry to one Se(3), one Se(4), one Se(6), two equivalent Se(2), and two equivalent Se(5) atoms. The K(3)-Se(3) bond length is 3.33 Å. The K(3)-Se(4) bond length is 3.68 Å. The K(3)-Se(6) bond length is 3.25 Å. There is one shorter (3.20 Å) and one longer (3.37 Å) K(3)-Se(2) bond length. There is one shorter (3.33 Å) and one longer (3.37 Å) K(3)-Se(5) bond length. There are three inequivalent Tc sites. In the first Tc site, Tc(1) is bonded to one Se(1), one Se(2), one Se(3), one Se(4), and one Se(5) atom to form distorted edge-sharing TcSe5 square pyramids. The Tc(1)-Se(1) bond length is 2.49 Å. The Tc(1)-Se(2) bond length is 2.53 Å. The Tc(1)-Se(3) bond length is 2.51 Å. The Tc(1)-Se(4) bond length is 2.54 Å. The Tc(1)-Se(5) bond length is 2.62 Å. In the second Tc site, Tc(2) is bonded to one Se(1), one Se(2), one Se(3), one Se(4), and one Se(6) atom to form a mixture of edge and corner-sharing TcSe5 square pyramids. The Tc(2)-Se(1) bond length is 2.52 Å. The Tc(2)-Se(2) bond length is 2.49 Å. The Tc(2)-Se(3) bond length is 2.49 Å. The Tc(2)-Se(4) bond length is 2.53 Å. The Tc(2)-Se(6) bond length is 2.66 Å. In the third Tc site, Tc(3) is bonded to one Se(1), one Se(2), one Se(3), one Se(4), and one Se(6) atom to form a mixture of distorted edge and corner-sharing TcSe5 square pyramids. The Tc(3)-Se(1) bond length is 2.48 Å. The Tc(3)-Se(2) bond length is 2.52 Å. The Tc(3)-Se(3) bond length is 2.51 Å. The Tc(3)-Se(4) bond length is 2.54 Å. The Tc(3)-Se(6) bond length is 2.66 Å. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to one K(2), one Tc(1), one Tc(2), and one Tc(3) atom. In the second Se site, Se(2) is bonded to two equivalent K(3), one Tc(1), one Tc(2), and one Tc(3) atom to form distorted SeK2Tc3 trigonal bipyramids that share corners with two equivalent Se(6)K3Tc2 trigonal bipyramids,  an edgeedge with one Se(2)K2Tc3 trigonal bipyramid, and  an edgeedge with one Se(6)K3Tc2 trigonal bipyramid. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to one K(1), one K(3), one Tc(1), one Tc(2), and one Tc(3) atom. In the fourth Se site, Se(4) is bonded in a 6-coordinate geometry to one K(1), one K(2), one K(3), one Tc(1), one Tc(2), and one Tc(3) atom. In the fifth Se site, Se(5) is bonded in a 5-coordinate geometry to one K(2), two equivalent K(3), one Tc(1), and one Se(5) atom. The Se(5)-Se(5) bond length is 2.42 Å. In the sixth Se site, Se(6) is bonded to one K(1), one K(2), one K(3), one Tc(2), and one Tc(3) atom to form distorted SeK3Tc2 trigonal bipyramids that share corners with two equivalent Se(2)K2Tc3 trigonal bipyramids,  an edgeedge with one Se(2)K2Tc3 trigonal bipyramid, and  an edgeedge with one Se(6)K3Tc2 trigonal bipyramid.