Preparation
Melem can be prepared by thermal decomposition of various C−N−H compounds, such as melamine C3N3(NH2)3, dicyandiamide H4C2N4, ammonium dicyanamide NH4 (CN)2 cyanamide H2CN2, at 400 to 450 °C.Structure and properties
Crystal structure
Melem crystallizes in the group P21/c (No. 14), with parameters a = 739.92(1) pm, b = 865.28(3) pm, c = 1338.16(4) pm, β = 99.912(2)°, and Z = 4. The almost-planar molecules are arranged in parallel layers spaced 327 pm apart. The molecule is in the triamino form, rather than one of the possible tautomers.Thermal decomposition
When heated above 560°, melem transforms into a graphite-like C−N material.Melemium cations
Melem accepts up to three protons yielding cations called melemium . Some salts described in the literature are melemium sulfate, • 2, melemium perchlorate, • , melemium hydrogensulfate and two melemium methylsulfonates • and • . The protons can be inserted in any of the six outer nitrogen atoms of the heptazine core, yielding many tautomers of apparently similar energies.See also
* Triazine , with a single C-N ring * Melamine , triamino triazine * Melaminium , a cation derived from melamine * Melam , a condensation dimer of melamine * Melamium , a cation derived from melam * Melon , a condensation oligomer of melemReferences