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/AsO4 layers linked by Me atoms with large ionic radii like alkali, alkaline earth, Pb(II), or Ag(I), and partly by hydrogen bonds. The layers are formed by Cu3O12 units: one square-planar coordinated Cu atom with (1) over bar symmetry is corner connected to two Cu atoms in a [4 + 1] or [5] coordination. Distinct patterns and links of the Cu3O12 groups by PO4 tetrahedra were observed, AA and AB stacking variants of the layers occur. Ba2Cu(PO4)(2) . H2O features isolated CuO4 squares interconnected by PO4 tetrahedra to chains which represent a component of the layers found in the Other compounds. (C) 1999 Academic Press.