Sr3Cu3(PO4)4, Pb3Cu3(PO4)4, BaCu2(PO4)2·H2O, and Ba2Cu(PO4)2·H2O: Crystal Structures and Topological Relationships

The four Cu(II)-phosphates(V) Sr3Cu3(PO4)4, Pb3Cu3(PO4)4, BaCu2(PO4)2·H2O, and Ba2Cu(PO4)2·H2O were synthesized under hydrothermal conditions. Their structures were determined from single-crystal X-ray diffraction data. They are related to a group of compounds formed by Cu(II)–PO4/AsO4layers linked byMeatoms with large ionic radii like alkali, alkaline earth, Pb (II), or Ag(I), and partly by hydrogen bonds. The layers are formed by Cu3O12units: one square-planar coordinated Cu atom with symmetry is corner connected to two Cu atoms in a [4+1] or [5] coordination. Distinct patterns and links of the Cu3O12groups by PO4tetrahedra were observed,AAandABstacking variants of the layers occur. Ba2Cu(PO4)2·H2O features isolated CuO4squares interconnected by PO4tetrahedra to chains which represent a component of the layers found in the other compounds.