Synthesis, Structure and Thermal Property of Tri(1-oxo-2,6,7-trioxa-l-phosphabicyclo[2. 2. 2]octane-methyl)phosphate

A novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-l-phosphabicyclo[2. 2. 2]octane-methyl)phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2, 6, 7-trioxal-phosphabicyclo[2. 2. 2]octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis, FTIR, ¹H NMR, ³¹P NMR and X-ray diffraction analysis. The crystals are monoclinic, space group C_c with unit cell dimensions a=1. 275 4(3) nm, b=1. 858 2(4) nm, c=1. 126 9(2) nm, V=2. 324 2(8) nm³, four molecules per unit cell. The final R=0. 032 2, R_w=0. 090 7 for 2 177 unique reflections. The crystal data reveal that the three cages in Trimer are structurally equivalent, and that the corresponding average bond lengths and bond angles are appropriate. The results of TG-DTA and DSC have convincingly demonstrated that Trimer has an excellent thermal stability and char forming characteristics, which is expected to be a promising intumescent flame retardant.