Cover illustration: The cation of hexakis(pyrazole-N2)copper(II) bis(hexafluoroarsenate). Displacement ellipsoids are plotted at the 50% probability level and H atoms have been omitted for clarity. See Otieno, Blanton, Hatfield, Asher & Parkin [Acta Cryst. (2002), C58, m182-m185].
Rubidium manganese hexathiodiphosphate, Rb2MnP2S6, crystallizes in a structure typical of compounds of the type A2MP2Q6 (A = K, Rb, Cs; M = Mn, Fe; Q = S, Se). Its structure can be viewed as columns of [MnP2S6]2− polyhedra parallel to the a axis, interconnected by Rb+.
The tetragonal polymorph of caesium hydroxide monohydrate, CsOH·H2O (or CsH3O2), a clathrate hydrate, contains an infinite three-dimensional hydrogen-bonded oxygen framework that is locally identical to layers found in the hexagonal modification.
The crystal structure of Hg3AlF6O2H has been determined at room temperature. It comprises [HgO2F6] polyhedra and [AlF6] octahedra. Assumed hydrogen bonding between two O atoms, with O⋯O = 2.562 (9) Å, provides additional bonds in the framework.