K2[Hg(SO3)2]·2.25H2O

• Published in: Acta crystallographica. Section C, Crystal structure communications Crystal structure communications, 2010-10, Vol.66 (10), p.i89-i91
• Main Authors: Weil, Matthias, Baumann, Stefan O., Breitinger, Dietrich K.
• Format: Article
• Language: English
• Subjects: Anions; Atoms & subatomic particles; Bonding; Cations; Chemical bonds; Chemical compounds; Consolidation; Crystal structure; Crystallography; Distortion; Hydrogen bonds; Polyhedrons
• ISSN: 0108-2701; 1600-5759
• DOI: 10.1107/S0108270110032373

The characteristic feature of the structure of the title compound, dipotassium bis(sulfito‐κS)mercurate(II) 2.25‐hydrate, is a layered arrangement parallel to (001) where each of the two independent [Hg(SO3)2]2− anions are grouped into centrosymmetric pairs and are surrounded by two K+ cations to give the overall layer composition {K2[Hg(SO3)2]2}2−. The remaining cations and the uncoordinated water molecules are situated between these layers. Within the [Hg(SO3)2]2− anions, the central Hg atoms are twofold coordinated by S atoms, with a mean Hg—S bond length of 2.384 (2) Å. The anions are slightly bent [174.26 (3) and 176.99 (3)°] due to intermolecular O...Hg interactions greater than 2.8 Å. All coordination polyhedra around the K+ cations are considerably distorted, with coordination numbers ranging from six to nine. Although the H atoms of the five water molecules (one with symmetry 2) could not be located, O...O separations between 2.80 and 2.95 Å suggest a system of medium to weak O—H...O hydrogen bonds which help to consolidate the structural set‐up. Differences and similarities between the bis(sulfito‐κS)mercurate(II) anions in the title compound and those in the related salts (NH4)2[Hg(SO3)2] and Na2[Hg(SO3)2]·H2O are discussed.