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Poly(triazine imide), a 2D extended carbon nitride network compound that is obtained from ionothermal synthesis in LiCl/KCl or LiBr/KBr salt melt has been known for over a decade. We now have investigated the formation process of this material starting from various triazine‐ and heptazine‐based precursors as well as the differences between ionothermal and conventional synthesis via thermal condensation. Independent of chosen starting material, melem (triamino‐s‐heptazine) is initially formed from the starting material as the imminent precursor to poly(triazine imide). We elucidate the impact of various different carbon nitride precursor compounds on the formation process, propose a mechanism for the back reaction of heptazines to triazines, and rationalize the occurring processes.

Melamium bromide and melamium iodide were synthesized from dicyandiamide in the presence of ammonium halides in evacuated Duran glass ampoules at temperatures of 450 °C. The crystal structures of both compounds were obtained from single‐crystal X‐ray diffraction. Melamium bromide C6N11H10Br crystallizes in space group P21/n [no. 14, a = 7.0500(5), b = 28.7096(18), c = 10.8783(8) Å, β = 96.060(2)°, Z = 8, wR2 = 0.2231] and exhibits a layer‐like arrangement of melamium ions, wherein both planar as well as twisted molecular structures of the cations occur. Melamium iodide C6N11H10I crystallizes in space group P21/c [no. 14, a = 6.8569(3), b = 11.9949(6), c = 14.0932(6) Å, β = 97.613(2)°, Z = 4, wR2 = 0.0654], however in a structure completely different from the one of melamium bromide. The melamium iodide structure is comprised of stacks of planar melamium ions that form complex, hydrogen‐bonded network layers with iodide ions within the layers. Both compounds were further characterized by FTIR spectroscopy, mass spectrometry, and elemental analyses. Melamium bromide and melamium iodide could be obtained as air stable and colorless crystals. Samples are crystallographically phase pure as shown by Rietveld refinement.

, an adduct compound that can be obtained from dicyandiamide in autoclave reactions at 450 8Ca nd elevateda mmonia pressure, had previously been describedbased on mass spectrometry and NMR spectroscopy,b ut only incompletelyc haracterized. The crystal structure of this compound has now been elucidated by means of synchrotron microfocus diffraction and subsequent quantum-chemical structure optimization applying DFT methods. The structure was refinedi nt riclinic space group P1 based on X-ray data. Cell parameters of a = 4.56(2), b = 19.34(8), c = 21.58(11) , a = 73.34(11)8, b = 89.1(2)8,a nd g = 88.4(2)8 were experimentally obtained. The resulting cell volumes agree with the DFT optimized value to within 7%.M olecular units in the structure form stacks that are interconnectedb yavastarray of hydrogen bridge interactions. Remarkably large melam dihedral angles of 48.48 were found that allow melam to interact with melem molecules from differents tack layers,t hus forming a3 Dn etwork. p-stacking interactions appear to play no major role in this structure.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.

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