Melem- and melamine-derived iminophosphoranes

Iminophosphorane derivatives of s-triazine and tri-s-triazine, C3N3(NPCl3)3 (1), [H2C3N3NH2(NPPh3)2]Br2 (2), [HC3N3NH2(NPPh3)2]Br (3), C6N7(NPCl3)3 (5), [HC6N7(NPCl3)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(NP(OPh)3)3 (7) was obtained. Its potential application as a flame retardant was examined by the UL 94 flammability test.