The Crystal Structures of Two No–Metal Tricyanomelaminates: Diammonium Tricyanomelaminate Dihydrate [NH 4 ] 2 [C 6 N 9 H] · 2 H 2 O and Dimelaminium Tricyanomelaminate Melamine Dihydrate [C 3 N 6 H 7 ] 2 [C 6 N 9 H] · C 3 N 6 H 6 · 2 H 2 O

Diammonium tricyanomelaminate dihydrate [NH 4 ] 2 [C 6 N 9 H] · 2 H 2 O ( 1 ) and dimelaminium tricyanomelaminate melamine dihydrate [C 3 N 6 H 7 ] 2 [C 6 N 9 H] · C 3 N 6 H 6 · 2 H 2 O ( 2 ) were obtained by metathesis reactions from Na 3 [C 6 N 9 ] in aqueous solution and characterized by single‐crystal X‐ray diffraction and 15 N solid‐state NMR spectroscopy ( 1 ). Both salts contain mono‐protonated tricyanomelaminate (TCM) anions and crystallize as dihydrates. Considering charge balance requirements, the crystal structure of 1 ( C 2/ c , a = 3181.8(6) pm, b = 360.01(7) pm, c = 2190.4(4) pm, β = 112.39(3)°, V = 2319.9(8) 10 6 · pm 3 ) can best be described by assuming a random distribution of an ammonium ion – crystal water pair over two energetically similar sites. Apart from two melaminium cations, 2 ( P 2 1 / c , a = 674.7(5) pm, b = 1123.6(5) pm, c = 3400.2(5) pm, β = 95.398(5), V = 2566(2) 10 6 · pm 3 ) contains one neutral melamine per formula unit acting as an additional “solvent” molecule and yielding a donor‐acceptor type of π–stacking interaction.