K2[O(HgSO3)3], a new sulfitomercurate with an [OHg3] core

The structure of dipotassium μ₃‐oxido‐trissulfitomercurate(II)], K₂O(HgSO₃)₃], is characterized by segregation of the K⁺ cations and complex O(HgSO₃)₃]²⁻ anions into layers parallel to (010). The anion has m symmetry and is a new example of a μ₃‐oxido‐trimercurate complex with a central OHg₃] core. This unit adopts the shape of a flat, almost trigonal, pyramid (mean O—Hg = 2.072 Å and mean Hg—O—Hg = 110.8°). The two independent Hg—S bonds have nearly the same length (mean Hg—S = 2.335 Å). Due to intermolecular O...Hg donor–acceptor interactions greater than 2.65 Å, the O—Hg—S fragments are slightly bent. The KO₉] coordination polyhedron of the K⁺ cation approaches a distorted tricapped trigonal prism with a 6+1+2] coordination.