issue contents
October 2010 issue

Cover illustration: A projection of the structure of catena-poly[thorium(IV)-tetrakis(2-3-carboxyadamantane-1-carboxylato)] on the ab plane, showing the packing of the coordination chains. C-H
O hydrogen bonds have been omitted for clarity. See Nazarenko, Rusanova, Krautscheid & Domasevitch [Acta Cryst. (2010), C66, m276-m279].
inorganic compounds
The crystal structure of K2[Hg(SO3)2]·2.25H2O contains two S-bonded sulfitomercurate anions, [Hg(SO3)2]2−, which are arranged pairwise and are surrounded by two K+ cations to give an anionic {K2[Hg(SO3)2]2}2− layer. The interlayer space is filled with the remaining cations and the water molecules.
Mg5TiO4(BO3)2 crystallizes in an orthorhombic cell with the space group Pbam. It is isostructural with the mineral ludwigite (Mg2FeO2BO3).
The title mixed hexaarsenate, Na4Co5.63Al0.91(AsO4)6, features a centrosymmetric three-dimensional framework composed of Co- and (Co,Al)-centred polyhedra and As-centred tetrahedra with tunnels running along [100] occupied by Na+ cations. Charge-distribution and bond-valence-sum calculations were used to support the structural model, and the experimental and validation results are discussed.