HgCu(SeO3)2 crystallizes in the monoclinic P2_1/c space group. Cu(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(4) atoms to form distorted edge-sharing CuO5 trigonal bipyramids. Hg(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), and two equivalent O(6) atoms. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. There are six inequivalent O sites. In the first O site, O(5) is bonded in a bent 120 degrees geometry to one Cu(1) and one Se(2) atom. In the second O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Hg(1) and one Se(2) atom. In the third O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cu(1), one Hg(1), and one Se(1) atom. In the fourth O site, O(2) is bonded in a water-like geometry to one Hg(1) and one Se(1) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to one Cu(1), one Hg(1), and one Se(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one Se(2) atom.
HgCu(SeO3)2 crystallizes in the monoclinic P2_1/c space group. Cu(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(4) atoms to form distorted edge-sharing CuO5 trigonal bipyramids. The Cu(1)-O(1) bond length is 1.97 Å. The Cu(1)-O(3) bond length is 1.99 Å. The Cu(1)-O(5) bond length is 2.00 Å. There is one shorter (1.96 Å) and one longer (2.42 Å) Cu(1)-O(4) bond length. Hg(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), and two equivalent O(6) atoms. The Hg(1)-O(1) bond length is 2.64 Å. The Hg(1)-O(2) bond length is 2.28 Å. The Hg(1)-O(3) bond length is 2.41 Å. There is one shorter (2.35 Å) and one longer (2.38 Å) Hg(1)-O(6) bond length. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.75 Å. The Se(1)-O(2) bond length is 1.73 Å. The Se(1)-O(3) bond length is 1.76 Å. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. The Se(2)-O(4) bond length is 1.73 Å. The Se(2)-O(5) bond length is 1.74 Å. The Se(2)-O(6) bond length is 1.75 Å. There are six inequivalent O sites. In the first O site, O(5) is bonded in a bent 120 degrees geometry to one Cu(1) and one Se(2) atom. In the second O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Hg(1) and one Se(2) atom. In the third O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cu(1), one Hg(1), and one Se(1) atom. In the fourth O site, O(2) is bonded in a water-like geometry to one Hg(1) and one Se(1) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to one Cu(1), one Hg(1), and one Se(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one Se(2) atom.