INTERACTION IN CRYSTALS .98. PROTONATED H EXAMETHYLMELAMIN SALTS WITHDIFFERENT ANIONS - MONOMERIC TETRAPHENYLBORATE, DIMERIC TRIFLUORACETATE AND POLYMERIC CHLORIDE-DIHYDRATE

Hexamethylmelamin (2,4,6-tris(dimethylamino)-1,3,5-triazine), on monop rotonation at one of the triazine nitrogens keeps its close to planar skeleton. Its salts with different anions reflect biochemically intere sting hydrogen-bridge networks: Crystallization of the hydrochloride f rom isopropanol solution containing Li+ [B-(C6H5)(4)], yields ''naked' ' molecular cations, packed in herringbone fashion in between the latt ice-dominating bulky, phenyl-shielded and non-protonable tetraphenylbo rate anions. From trifluoroacetic acid, crystals with sandwich-like su bunits connected by hydrogen-bridged anions [F3CCOO-... HOOCCF3] are o btained. The hydrochloride salt, prepared by adding aqueous HCl to a d iethylether solution, crystallizes in stacks of triazinium cation dime rs with an intermolecular bridge N+-H ... Cl-... H+N in between chlori de-hydrate strands (... Cl-HOH ... O(H)H ... Cl-...). Together, the st ructures of the three different hexamethyl-melaminium salts further il lustrate the influence of anions on the crystallization of protonated nitrogen heterocycles and complement that of counter cation solvation in molecular anion salts.