The Synthesis and Thermal Decomposition of Calcium Phosphoramidate

Abstract

Abstract Calcium phosphoramidate monohydrate was made by adding an aqueous calcium chloride solution to an aqueous potassium hydrogenphosphoramidate solution at pH 9.0–9.5 below 5 °C. The product was stable at room temperature, but it was decomposed by heating. When the product was heated at 150 °C in air, the phosphoramidate decomposed to produce anhydrous calcium phosphoramide and also ortho- and diphosphates. The elimination of ammonia from amino groups to form a P–N(H)–P linkage was not observed at this temperature. The phosphoramidate decomposed in air to form ortho-, imidodi-, di-, and a small amount of higher polyphosphates at a temperature higher than 150 °C. Imidodiphosphate was decomposed to diphosphate by moisture in air. β-Calcium diphosphate was formed by heating the phosphoramidate at a temperature higher than 750 °C in air. When the phosphoramidate was heated in dried N2, it showed the same thermal reaction as that in air below 250 °C, while the amount of imidodiphosphate in the thermal product was larger than that in air at a temperature higher than 400 °C.