1976 Volume 49 Issue 12 Pages 3524-3529
The method for synthesis of N4P4(NH2)8 by the reaction between (NPCl2)4 and ammonia and its hydrolysis behavior were investigated. The reaction of (NPCl2)4 with liquid ammonia took place violently at first, and the resulting product contained more than several percents of an insoluble material. The extract from this product had a rather low yield, about 20–25%. However, such a drastic reaction could be avoided by the addition of a small amount of dioxane to the reaction system; then the insoluble material did not form, and the yield increased to 55–66%. The final product contained P 37–38% and N 50–51%; thus the mole ratio of N to P was exactly 3 : 1 and the composition agreed with that of N4P4(NH2)8·H2O. When an aqueous solution of N4P4(NH2)8 was refluxed at 100 °C, the compound was initially hydrolyzed to PO(NH2)3 and P2O2NH(NH3)4, these being converted into PO(ONa)(NH2)2. At room temperature, the rate of hydrolysis was quite slow, but the composition of the hydrolysis products was similar to that at 100 °C. In a sodium hydroxide solution, N4P4(NH2)8 was converted directly into PO(ONa)(NH2)2 at an elevated temperature. The rate of the alkali hydrolysis obeyed a first-order equation, with the rate constants of 1.0×10−3, 2.5×10−3, 1.9×10−2, and 4.2×10−2 at 50, 60, 80, and 90 °C, respectively. These values were about 2.7 times that of N3P3(NH2)6. The activation energy of the reaction was 20.8 kcal/mol. The acid hydrolysis behavior resembled that in the neutral hydrolysis, but the reaction was accelerated with acid strength. The formation of tetrametaphosphimate by the hydrolysis of N4P4(NH2)8, that had previously been claimed, could not be reproduced in this study.
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