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

The title compound  C 6 N 7 (NHNH 2 ) 3 ( 1 ) was obtained from melem C 6 N 7 (NH 2 ) 3 or melon [C 6 N 7 (NH 2 )NH] n and hydrazine by an autoclave synthesis. Upon treatment with a 10 % HCl solution it is transformed into the trihydrochloride  [C 6 N 7 (NHNH 3 ) 3 ]Cl 3 ( 2 ). Compounds 1 and 2 were analysed with 13 C NMR, 15 N NMR, FTIR and Raman spectroscopy. Furthermore, the single‐crystal X‐ray structure of the pentahydrate of 2 is reported ( P \bar{1} , a = 674.96(3), b = 1214.17(6), c = 1272.15(6) pm, α = 66.288(2)°, β = 75.153(2)°, γ = 80.420(2)°, 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 NaNO 2 /HCl yields triazido‐ s ‐heptazine, C 6 N 7 (N 3 ) 3 ( 3 ). Tris(tri‐ n ‐butylphosphinimino)‐ s ‐heptazine ( 4 ) was synthesised from 3 and characterised by means of 13 C, 31 P, 1 H 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.