Reaction of 2,4,6-Triazido-1,3,5-triazine with Triphenylphosphane. Syntheses and Characterization of the Novel 2-Triphenylphosphanimino-4-azidotetrazolo[5,1-a]-[1,3,5]triazine and 2,4,6-Tris(triphenylphosphanimino)-1,3,5-triazine

Abstract

2-Triphenylphosphanimino-4-azidotetrazolo[5,1-a]-[1,3,5]triazine (6) was obtained by reaction of 2,4,6-triazido-1,3,5-triazine (1) with 1 equiv of triphenylphosphane. Raman and X-ray data revealed that only one azide group formed a tetrazole ring system whereas the second azide group did not undergo ring closure. To investigate the equilibrium between the tetrazole isomer and the open-chain azide structure for these and related species, (31)P NMR studies were carried out. The obtained spectra displayed an equilibrium between the tetrazole and the open-chain azide isomers. 2,4,6-Tris(triphenylphosphanimino)-1,3,5-triazine (4) was prepared by treatment of 1 with 3 equiv of triphenylphosphane, and its X-ray structure is discussed. On the basis of PM3 semiempirical and density functional calculations, the reaction of 1 with triphenylphosphane was studied. The thermodynamics of different isomerization reactions and the activation barriers to cyclization were estimated.

Azide–Tetrazole Ring‐Chain Isomerism in Polyazido‐1,3,5‐triazines, Triazido‐s‐heptazine, and Diazidotetrazines

“…[25] Due to computational cost all other compounds were optimized on the B3LYP level of theory with the same basis set. Comparison of the B3LYP energies from reference [20] for cyanuric azide and of values obtained for the diazidotetrazine isomers at the B3LYP/aug-cc-pVTZ level of theory shows good agreement with the energies obtained at the CCSD(T) level. The vibrational frequencies, which were computed at the optimized structures, show true minima on the potential energy surface with no imaginary frequencies for all azides and tetrazoles.…”

“…[20] The MP2 energy differences are higher than the CCSD(T) values and increase for isomers with more tetrazole rings. The energy differences between the MP2 and CCSD(T) values are bigger for the transition states than for the ground states.…”

“…While solvation in water favors the tritetrazole 8 to a great extent, it is still 22.7 kcal mol -1 higher in energy than 1 and has not yet been detected experimentally. [20,21] Thus cyanuric azide is not a suitable starting material for the synthesis of its tetrazole isomers.…”

“…Earlier investigations of the azide-tetrazole isomerism of cyanuric azide showed that the azide groups of cyanuric azide do not cyclize to form tetrazoles, but that the reaction of cyanuric acid with PPh 3 leads to triphenylphosphanimino compounds where an azide group is in equilibrium with the ring-closed tetrazole in solution and a tetrazole is formed upon precipitation. [19,20] While no tetrazole formed from a polyazido-1,3,5-triazine has yet been detected, the mono-and ditetrazoles of diazido-1,2,4,5-tetrazine were synthesized only very recently. [21] In order to better understand the effects of electron-donating and electron-withdrawing groups on the azide-tetrazole equilibrium of cyanuric azide, we replaced one azide group with an amino and a nitro group, respectively.…”

Condensed Tetrazolo-1,3,5-triazines. 1. Synthesis of 5-Polynitromethyltetrazolo[1,5-a]-1,3,5-triazin-7-one Salts

“…For azido-1,3,5-triazines which contain electron-donor substitutents this question has been considered in [12,13].…”