Synthese, Struktur und thermisches Verhalten von Thiophosphorsäuretriamid SP(NH2)3 [1] / Synthesis, Structure, and Thermal Behaviour of Phosphorothionic Triamide SP(ΝΗ2)3 [1]
2014
Schnick, Wolfgang
Phosphorothionic triamide SP(NH₂)₃ is obtained by slow addition of SPCl₃ dissolved in dry CH₂Cl₂ to a satured solution of NH₃ in CH₂Cl₂ at —50°C. Ammonium chloride is removed from the resulting precipitate by treatment with HNEt₂ followed by extraction with CH₂Cl₂. Coarse crystalline SP(NH₂)₃ is obtained after recrystallization from dry methanol. The crystal structure of SP(NH₂)₃ has been determined by single crystal X-ray methods (Pbca; a = 922.3(1), b = 953.8(1), c = 1058.4(2) pm, Z = 8). In the crystals the molecules show non-crystallographic point symmetry C₈. The P—S bond (195.4(1) pm) is slightly longer than in SPCl₃. From P—N bond lengths of about 166 pm a significant electrostatic strengthening of the P—N single bonds is assumed. Weak intermolecular hydrogen bonding interactions (N —H · · · N ≥ 329.5 pm; N — H · · · S ≥ 348.3 pm) are observed.Investigation of thermal properties shows a melting temperature of 115°C for SP(NH₂)₃. According to combined DTA/TG and MS investigations above this temperature the compound decomposes by evolution of H₂S and NH₃ to yield amorphous phosphorus(V)nitride.
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