Ca[Ag2(SCN)4]·2H2O contains eight-membered Ag4S4 rings bonded together through shared atoms to form layers parallel to (100). The thiocyanate groups link the layers to Ca–O chains running parallel to the c axis.
The title compound crystallizes with the cyano groups forming a regular octahedral arrangement around the Fe atom. The Pr atom is eight-coordinated by six N atoms and two symmetry-related water molecules. The second (uncoordinated, symmetry independent) water molecule forms a hydrogen-bonded network with N atoms.
The ambient-temperature form of Tl2SO4, β-Tl2SO4, is isostructural with β-K2SO4 and consists of isolated SO4 tetrahedra linked by two non-equivalent Tl atoms, which present a low stereochemical activity of their 6s2 pairs.
The crystal structures of two new quaternary compounds, viz. dicerium orthosilicate selenide and dicerium orthosilicate telluride, Ce2(SiO4)Q (Q = Se or Te), have been determined from single-crystal X-ray diffraction data. Each structure comprises infinite chains of SiO4 tetrahedra separated by Ce and Q atoms. The site symmetries are Ce m and 2, Si 2 and Qm. The O atoms are in general positions.