C~IHa0N40, Mr=21423, crystallizes in two different forms: (I) monoclinic, P2t/n, a = 14.815 (1), b = 9.477 (1), c = 7.869 (3) A, /3 = 98-85 (1) °, V = 1091.7 (4)/~3, Z = 4, Dx = 1.303 Mg m -3, A(Cu Kth) = 1.54050/~, # = 0.692 mm-1, F(000) = 448, T = 295 K, final R = 0.048 for 1512 reflections; (II) orthorhombic, P2~212a, a = 9.299 (1), b = 14.874 (1), c = 7.557 (4) A, V = 1045.2 (5) A. 3, Z = 4, Dx = 1.361 Mg m -3, A(Cu Kay) = 1.54050 A_, /~ = 0.723 m m 1, F(000) = 448, T = 295 K, final R = 0.050 for 760 reflections. Bond distances and angles are quite similar in the two structures. Experimental. The title compound was prepared by the radical substitution reaction of 1,2,3-triazinium dicyanomethylide (III) with ammonium persulfate and formamide at 353 K (Minisci, Fontana & Vismara, 1990). The crystals, colorless prism (0.45 × 0.25 x 0.50 mm) (I) and clear needle (0.10 x 0.03 x 0.50mm) (II) were recrystallized from methanol. Details of data collection and refinement are listed in Table 1. Intensity data were collected with a Rigaku AFC-5 four-circle diffractometer used in the to-20 scan mode, a~ scan width (1.3 + 0.41tan0) ° and scan N, ~q¢.r~ in HCONH, 353 K N,