K2HgCl4 crystallizes in the orthorhombic Pbam space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to three equivalent Cl(1) and four equivalent Cl(3) atoms to form distorted KCl7 pentagonal bipyramids that share corners with two equivalent Hg(1)Cl6 octahedra, corners with two equivalent K(1)Cl7 pentagonal bipyramids, corners with four equivalent K(2)Cl7 pentagonal bipyramids, edges with four equivalent Hg(1)Cl6 octahedra,  an edgeedge with one K(1)Cl7 pentagonal bipyramid, edges with two equivalent K(2)Cl7 pentagonal bipyramids, and faces with two equivalent K(1)Cl7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 50°. In the second K site, K(2) is bonded to three equivalent Cl(2) and four equivalent Cl(3) atoms to form distorted KCl7 pentagonal bipyramids that share corners with two equivalent Hg(1)Cl6 octahedra, corners with two equivalent K(2)Cl7 pentagonal bipyramids, corners with four equivalent K(1)Cl7 pentagonal bipyramids, edges with four equivalent Hg(1)Cl6 octahedra,  an edgeedge with one K(2)Cl7 pentagonal bipyramid, edges with two equivalent K(1)Cl7 pentagonal bipyramids, and faces with two equivalent K(2)Cl7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 50°. Hg(1) is bonded to two equivalent Cl(1), two equivalent Cl(2), and two equivalent Cl(3) atoms to form HgCl6 octahedra that share corners with two equivalent K(1)Cl7 pentagonal bipyramids, corners with two equivalent K(2)Cl7 pentagonal bipyramids, edges with two equivalent Hg(1)Cl6 octahedra, edges with four equivalent K(1)Cl7 pentagonal bipyramids, and edges with four equivalent K(2)Cl7 pentagonal bipyramids. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded to three equivalent K(1) and two equivalent Hg(1) atoms to form ClK3Hg2 trigonal bipyramids that share corners with four equivalent Cl(1)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(2)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(3)K4Hg trigonal bipyramids, edges with two equivalent Cl(1)K3Hg2 trigonal bipyramids, and edges with six equivalent Cl(3)K4Hg trigonal bipyramids. In the second Cl site, Cl(2) is bonded to three equivalent K(2) and two equivalent Hg(1) atoms to form ClK3Hg2 trigonal bipyramids that share corners with four equivalent Cl(1)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(2)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(3)K4Hg trigonal bipyramids, edges with two equivalent Cl(2)K3Hg2 trigonal bipyramids, and edges with six equivalent Cl(3)K4Hg trigonal bipyramids. In the third Cl site, Cl(3) is bonded to two equivalent K(1), two equivalent K(2), and one Hg(1) atom to form distorted ClK4Hg trigonal bipyramids that share corners with two equivalent Cl(1)K3Hg2 trigonal bipyramids, corners with two equivalent Cl(2)K3Hg2 trigonal bipyramids, corners with five equivalent Cl(3)K4Hg trigonal bipyramids, edges with three equivalent Cl(1)K3Hg2 trigonal bipyramids, edges with three equivalent Cl(2)K3Hg2 trigonal bipyramids, and edges with four equivalent Cl(3)K4Hg trigonal bipyramids.
K2HgCl4 crystallizes in the orthorhombic Pbam space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to three equivalent Cl(1) and four equivalent Cl(3) atoms to form distorted KCl7 pentagonal bipyramids that share corners with two equivalent Hg(1)Cl6 octahedra, corners with two equivalent K(1)Cl7 pentagonal bipyramids, corners with four equivalent K(2)Cl7 pentagonal bipyramids, edges with four equivalent Hg(1)Cl6 octahedra,  an edgeedge with one K(1)Cl7 pentagonal bipyramid, edges with two equivalent K(2)Cl7 pentagonal bipyramids, and faces with two equivalent K(1)Cl7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 50°. There are two shorter (3.16 Å) and one longer (3.27 Å) K(1)-Cl(1) bond length. There are two shorter (3.15 Å) and two longer (3.16 Å) K(1)-Cl(3) bond lengths. In the second K site, K(2) is bonded to three equivalent Cl(2) and four equivalent Cl(3) atoms to form distorted KCl7 pentagonal bipyramids that share corners with two equivalent Hg(1)Cl6 octahedra, corners with two equivalent K(2)Cl7 pentagonal bipyramids, corners with four equivalent K(1)Cl7 pentagonal bipyramids, edges with four equivalent Hg(1)Cl6 octahedra,  an edgeedge with one K(2)Cl7 pentagonal bipyramid, edges with two equivalent K(1)Cl7 pentagonal bipyramids, and faces with two equivalent K(2)Cl7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 50°. There are a spread of K(2)-Cl(2) bond distances ranging from 3.16-3.26 Å. All K(2)-Cl(3) bond lengths are 3.15 Å. Hg(1) is bonded to two equivalent Cl(1), two equivalent Cl(2), and two equivalent Cl(3) atoms to form HgCl6 octahedra that share corners with two equivalent K(1)Cl7 pentagonal bipyramids, corners with two equivalent K(2)Cl7 pentagonal bipyramids, edges with two equivalent Hg(1)Cl6 octahedra, edges with four equivalent K(1)Cl7 pentagonal bipyramids, and edges with four equivalent K(2)Cl7 pentagonal bipyramids. Both Hg(1)-Cl(1) bond lengths are 2.93 Å. Both Hg(1)-Cl(2) bond lengths are 2.93 Å. Both Hg(1)-Cl(3) bond lengths are 2.47 Å. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded to three equivalent K(1) and two equivalent Hg(1) atoms to form ClK3Hg2 trigonal bipyramids that share corners with four equivalent Cl(1)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(2)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(3)K4Hg trigonal bipyramids, edges with two equivalent Cl(1)K3Hg2 trigonal bipyramids, and edges with six equivalent Cl(3)K4Hg trigonal bipyramids. In the second Cl site, Cl(2) is bonded to three equivalent K(2) and two equivalent Hg(1) atoms to form ClK3Hg2 trigonal bipyramids that share corners with four equivalent Cl(1)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(2)K3Hg2 trigonal bipyramids, corners with four equivalent Cl(3)K4Hg trigonal bipyramids, edges with two equivalent Cl(2)K3Hg2 trigonal bipyramids, and edges with six equivalent Cl(3)K4Hg trigonal bipyramids. In the third Cl site, Cl(3) is bonded to two equivalent K(1), two equivalent K(2), and one Hg(1) atom to form distorted ClK4Hg trigonal bipyramids that share corners with two equivalent Cl(1)K3Hg2 trigonal bipyramids, corners with two equivalent Cl(2)K3Hg2 trigonal bipyramids, corners with five equivalent Cl(3)K4Hg trigonal bipyramids, edges with three equivalent Cl(1)K3Hg2 trigonal bipyramids, edges with three equivalent Cl(2)K3Hg2 trigonal bipyramids, and edges with four equivalent Cl(3)K4Hg trigonal bipyramids.