Evers, J; Krumm, B; Axthammer, QJ; Martens, J; Blaha, P; Steemann, FX; Reith, T; Mayer, P; Klapötke, TM
Isocyanic acid, HNCO, the imide of carbon dioxide, was prepared by reaction of stearic acid and potassium cyanate (KOCN) at 60 °C in a sealed, thoroughly dried reactor. Interestingly, its crystal structure, solved by X-ray single crystal diffraction at 123(2) K, shows a group-subgroup relation for the NCO- anion to carbon dioxide: (for CO2, cP12, Pa3̅, a = 5.624(2) Å, 150 K, C-O 1.151(2) Å; for HNCO, oP16, Pca21, a = 5.6176(9), b = 5.6236(8), c = 5.6231(7) Å, 123(2) K). Precise positions of H, N, C, and O were determined by DFT calculations with WIEN2k leading to interatomic distances C-O 1.17, C-N 1.22, N-H 1.03, and -N-H···N 2.14 Å, and the interatomic angle N-C-O 171°.