Melem- and melamine-derived iminophosphoranes

Iminophosphorane derivatives of s-triazine and tri-s-triazine, C3N3(N=PCl3)(3) (1), [H2C3N3NH2(N=PPh3)(2)]Br-2 (2), [HC3N3NH2(N=PPh3)(2)]Br (3), C6N7(N=PCl3)(3) (5), [HC6N7(N=PCl3)(3)]Cl (6) were obtained by the Kirsanov reaction of melamine (1-3) and melem (5 and 6) with halogenated phosphorus compounds. The products were characterized by FTIR and solution NMR spectroscopy as well as by single-crystal X-ray diffraction. Additionally, in order to investigate the electron density distribution in the s-triazine or s-heptazine systems combined with the phosphinimine group, and to understand the influence of protonation on the triazine and heptazine moieties, quantum chemical analyses of compounds 2, 3, 5 and 6 were performed. Furthermore, by reaction of 5 with phenol the compound C6N7(N=P(OPh)(3))(3) (7) was obtained. Its potential application as a flame retardant was examined by the UL 94 flammability test.