Abstract
The title compound, CuHPO(4), has been synthesized from a mixture of phospho-ric acid and copper oxide. It has the same composition as MHPO(4) (M = Ca, Ba, Pb, Sr or Sn), but adopts a rhombohedral structure with all atoms on general positions. The structure features distorted PO(4) tetra-hedra linked by copper, forming 12-membered rings. The Cu(II) atom is coordinated by five O atoms in a distorted square-pyramidal manner. O-H⋯O hydrogen bonding leads to an additional stabilization of the structure.