Interaction in crystals .98. Protonated hexamethylmelamin salts with different anions: Monomeric tetraphenylborate, dimeric trifluoracetate and polymeric chloride-dihydrate

Hexamethylmelamin (2,4,6-tris(dimethylamino)-1,3,5-triazine), on monoprotonation at one of the triazine nitrogens keeps its close to planar skeleton. Its salts with different anions reflect biochemically interesting hydrogen-bridge networks: Crystallization of the hydrochloride from isopropanol solution containing Li+ [B-(C6H5)(4)], yields ''naked'' molecular cations, packed in herringbone fashion in between the lattice-dominating bulky, phenyl-shielded and non-protonable tetraphenylborate anions. From trifluoroacetic acid, crystals with sandwich-like subunits connected by hydrogen-bridged anions [F3CCOO-... HOOCCF3] are obtained. The hydrochloride salt, prepared by adding aqueous HCl to a diethylether solution, crystallizes in stacks of triazinium cation dimers with an intermolecular bridge N+-H ... Cl-... H+N in between chloride-hydrate strands (... Cl-HOH ... O(H)H ... Cl-...). Together, the structures of the three different hexamethyl-melaminium salts further illustrate the influence of anions on the crystallization of protonated nitrogen heterocycles and complement that of counter cation solvation in molecular anion salts.