Synthesis, Crystal Structure and Thermal Properties of N,N'-Bis(5,5-dimethyl-2-phospha-2-thlo-1

The title compound N,N'-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxan-2-yl) ethyle-ne diamine (DPTDEDA, C12H26N2O4P2S2) was synthesized by the reaction of neopentyl glycol,phosphorus thio-chloride and 1,2-ethylenediarnine, and characterized by elemental analysis, IR and 1H NMR spectra. Its crystal structure was determined by single-crystal X-ray diffraction analysis and the thermal property was analyzed by TG analysis. The crystal structure belongs to monoclinie,space group P21/c, with a = 14.557(16), b = 11.299(12), c = 12.163(13) A, β= 98.707(19)°,Dc=1.305 g/cm3, Z=4,λ = 0.71073 A,μ(MoKa) = 0.447 mm-1, Mr = 388.41, V = 1977(4) A3, F(000) =824, S=1.107, the final R = 0.0478 and wR = 0.0810 for 1738 observed reflections (Ⅰ 2σ(Ⅰ)).X-ray analysis reveals that the crystal structure is eentrosymmetrically distributed through 1,2-ethylenediamine to join two distorted six-membered rings. The weak N-H…S interactions are observed and link the molecules into sheets. TG analysis shows that the title compound has good thermal stability and char-forming capability, which are required for an excellent intumescent fire retardant.