Exploring the Route to 1,3,5‐Triazine‐2,4,6‐triisocyanate (C 6 N 6 O 3 ), a Hydrogen‐Free Molecular Precursor for Polymeric C–N–(O) Materials

We report on the synthesis of 1,3,5‐triazine‐2,4,6‐triisocyanate [C 3 N 3 (NCO) 3 ]. The hydrogen‐free compound, a new molecular precursor for the realisation of C–N–(O) networks (e.g., C 2 N 2 O, C 3 N 4 ), has been obtained in a five‐step reaction sequence with well‐defined intermediates. Starting from cyanoformiate, triethyl 1,3,5‐triazine‐2,4,6‐tricarboxylate (C 12 O 6 N 3 H 15 ) was prepared and identified by means of spectroscopic and thermal methods. In addition, the crystal structures of two modifications were solved [high temperature (HT): P 6 3 / m (no. 176), a = 11.07(2) Å, c = 6.83(4) Å, γ = 120°, V = 725.80(2) Å 3 , Z = 2; low temperature (LT): P 2 1 / n (no. 14), a = 21.75(2) Å, b = 6.54(5) Å, c = 21.81(0) Å, β = 119.81(0)°, V = 2693.98(6) Å 3 , Z = 8]. Hydrolysis of the ester under alkaline conditions (KOH) yielded the corresponding salt of 1,3,5‐triazine‐2,4,6‐tricarboxylic acid, C 3 N 3 (COO) 3 K 3 · 2H 2 O [ P $\bar {1}$ (no. 2), a = 6.95(0) Å, b = 17.45(8) Å, c = 17.54(1) Å, α = 119.76(0)°, β = 92.04(0)°, γ = 93.92(0) °Å; V = 1837.63(0) Å 3 , Z = 6]. The dried salt was converted into 1,3,5‐triazine‐2,4,6‐tricarbonyl trichloride [C 3 N 3 (COCl) 3 ] by reaction with POCl 3 . The trichloride was also studied by means of single‐crystal structure analysis [ P 2 1 / c (no. 14), a = 9.73(6) Å, b = 11.21(1) Å, c = 17.03(1) Å, β = 91.91(1)°, V = 1857.87(23) Å 3 , Z = 8]. Further reaction of the molecular acid chloride with AgN 3 gave the acyl azide, which was converted in situ into the product 1,3,5‐triazine‐2,4,6‐triisocyanate by means of a thermally induced Curtius rearrangement. The final product was studied by thermal and spectroscopic methods. Owing to the high chemical reactivity of the isocyanate groups, oligomerisation/polymerisation of the molecular compound occurred immediately at room temperature, thus forming amorphous uretdione‐type coordination compounds. The uretdione‐based network has been converted into the corresponding molecular carbamates (R–NH–CO–OR) by reaction with ethanol [ P 6 3 / m (no. 176), a = 14.873(12) Å, c = 6.605(7) Å, γ = 120°, Z = 2, V = 1265(2) Å 3 ] and 2‐propanol [ P 4 3 (no. 78), a = 13.526(8) Å, c = 12.956(2) Å, Z = 4, V = 2370.5(3) Å 3 ]. The potential of this new precursor in the field of carbon nitrides as well as carbon oxynitrides is discussed briefly.