About 200 years ago, ammonium cyanate, [NH4][OCN], was obtained by Liebig and Wöhler as a fluffy, white powder from the reaction of dry ammonia with cyanic acid. They also noticed its rearrangement at room temperature into urea, [NH2]2CO, a compound which has the same sum formula as ammonium cyanate.[1,2] From this the concept of isomerism was deduced and remains unchanged until today. In contrast, the heavier homologue, ammonium thiocyanate, [NH4][SCN], showed higher thermal stability: it only isomerizes into thiourea, [NH2]2CS, when held at ~120 °C for some time.[4–6]Until now, the heavier congener of this series, ammonium selenocyanate, [NH4][SeCN], has scarcely been studied. The first crystallographic data were reported 1913, however, experimental procedures were omitted. In 1982, a detailed synthetical procedure was published, albeit without meaningful further analysis.[7,8] Due to its highly sensitive nature, detailed crystallographic studies and isomerization behavior are a striking gap in this field.We revisit studies of the thermal behavior of [NH4][OCN] and [NH4][SeCN], and report on the hitherto unknown crystal structure of [NH4][SeCN], its behavior towards thermal stress, and reactivity toward Ag[SeCN].
 J. D. Dunitz, K. D. M. Harris, R. L. Johnston, B. M. Kariuki, E. J. MacLean, K. Psallidas, W. B. Schweizer, R. R. Tykwinski, J. Am. Chem. Soc. 1998, 120, 13274–13275.
 F. Wöhler, Ann. Phys. Chem. 1828, 88, 253–256.
 J. J. Berzelius, Jahresbericht Über Die Fortschritte Der Physischen Wissenschaften, Heinrich Laupp, Tübingen, 1832.
 J. Waddell, J. Phys. Chem. 1898, 2, 525–535.
 G. Peyronel, R. Battistuzzi, G. Marcotrigiano, J. Chem. Soc. 1974, 896.
 S. T. Talreja, P. M. Oza, P. S. Rao, Bull. Chem. Soc. Jpn. 1967, 40, 2427–2428.
 K. Geisler, E. Nobst, C. Müller, E. Bulka, Z. Chem. 1982, 22, 113–114.
 E. von Fedorow, Z. Krist. 1913, 52, 97–136.
 A. Shlyaykher, F. Tambornino, Inorg. Chem. 2023, 62, 30, 11943–11953.
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