Crystal structure of new hexahydrate dicobalt pyrophosphate Co2P2O7·6H2O: comparison with Co2P2O72H2O, α-, β- and γ-Co2P2O7

Abstract

Abstract A new dicobalt pyrophosphate, Co2P2O7·6H2O, has been synthesized and characterized by single crystal X-ray diffraction. The compound belongs to the mono clinic space group P21/n, and its unit cell dimensions are: a = 7.2077(2), b = 18.3373(5), c = 7.6762(2) Å, β = 92.4356(15)°, V = 1013.64(5) Å3, Z = 4. The structural parameters were refined to an R index of 0.0570 for 1937 reflections with I>2σ(I o). The framework of this pyro phosphate is made by the packing of layers of discrete CoO6 octahedra connected by double tetrahedra P2O7 groups. The (P2O7)4– anion group shows bent eclipsed conformation. A comparative study among anhydrous (α-, β- and γ-Co2P2O7) and hydrated forms (Co2P2O7·2H2O) of dicobalt pyrophosphates known in literature is presented.