Abstract

The title compound has been hydrothermally synthesized from elemental cobalt, phosphoric acid, and hydrazine, and characterized by single crystal X-ray diffraction [crystal data: triclinic, P, a = 5.1393(6), b = 6.363(1), c = 11.293(1) Å, α = 95.65(1), β = 96.874(9), γ = 92.79(1)°], IR, TGA, and magnetic measurement. The structure is made of neutral layers of corner-sharing PO₄ tetrahedra and dimers of edge-sharing 5- and 6-coordinate cobalt polyhedra. The hydrazinium cations, N₂H₅⁺, are coordinated as ligands on both sides of the layers and complete the octahedral coordination of the six-coordinate cobalt. The so-grafted layers are held together by strong and extensive hydrogen bonding. Thermally the compound is stable up to 360 °C, above which it decomposes in a single step to yield cobalt pyrophosphate. Magnetic measurements show paramagnetic Curie–Weiss behavior over the temperature range 5–300 K.