2,5,8-Trihydrazino-s-heptazine: A Precursor for Heptazine-based Iminophosphoranes

The title compound C6N7(NHNH2)(3) (1) was obtained from melem C6N7(NH2)(3) or melon [C6N7(NH2)NH](n) and hydrazine by an autoclave synthesis. Upon treatment with a 10 % HCl solution it is transformed into the trihydrochloride [C6N7(NHNH3)(3)]Cl-3 (2). Compounds 1 and 2 were analysed with C-13 NMR, N-15 NMR, FTIR and Raman spectroscopy. Furthermore, the single-crystal X-ray structure of the pentahydrate of 2 is reported (P (l) over bar($) over bar, a = 674.96(3), b = 1214.17(6), c = 1272.15(6) pm, alpha = 66.288(2)degrees,beta = 75.153(2)degrees, gamma = 80.420(2)degrees V = 920.30(8).10(6) pm(3), Z = 2, T = 90(2) K). The thermal decomposition of 1 and 2 was investigated with TG/DTA. Reaction of 1 with NaNO2/HCl yields triazido-s-heptazine, C6N7(N-3)(3) (3). Tris(tri-n-butylphosphinimino)-s-heptazine (4) was synthesised from 3 and characterised by means of C-13, P-31. H-1 NMR, FTIR and MALDI-TOF spectroscopy. Similar to s-heptazine derivative 3, compounds 1 and 4 are precursors for graphitic carbon nitrides, which have attracted considerable attention recently, and to various potential applications, Such as flame retardants and (photo) catalysis.