Hg(3)Se(3)O(10), a mercury(II) compound with mixed-valence oxoselenium(IV/VI) anions.

The title compound, trimercury(II) bis[selenite(IV)] selenate(VI), contains three crystallographically inequivalent HgII cations with coordination numbers of eight (denoted Hg1 and Hg2) and five (denoted Hg3). The corresponding coordination polyhedra around the metal atoms might be described as intermediates between a square antiprism and a triangulated dodecahedron for both Hg1 and Hg2, and a strongly distorted truncated octahedron for Hg3. (infinity)2[HgO(8/2)] layers of edge-sharing [HgO(8)] polyhedra propagate parallel to the bc plane, and are connected via SeVIO(4) tetrahedra and [Hg3O(5)] polyhedra along the a axis, forming an arrangement with channels propagating parallel to the b axis. The two independent SeIVO(3) pyramids bridge the Hg atoms, and the non-bonding orbitals of the SeIV ions protrude into the channels from opposite sides.