Thiosemicarbazide is the chemical compound with the formula H2NC(S)NHNH2. A white, odorless solid, it is related to thiourea (H2NC(S)NH2) by the insertion of an NH center. They are commonly used as ligands for transition metals.[2] Many thiosemicarbazides are known. These feature an organic substituent in place of one or more H's of the parent molecule. 4-Methyl-3-thiosemicarbazide is a simple example. According to X-ray crystallography, the CSN3 core of the molecule is planar as are the three H's nearest the thiocarbonyl group.[3] Reactions Thiosemicarbazides are precursors to thiosemicarbazones. They are precursors to heterocycles.[4] Formylation of thiosemicarbazide provides access to triazole.[5] References International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 1003. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4. Campbell, Michel J.M. (1975). "Transition metal complexes of thiosemicarbazide and thiosemicarbazones". Coordination Chemistry Reviews. 15 (2–3): 279–319. doi:10.1016/S0010-8545(00)80276-3. Andreetti, G. D.; Domiano, P.; Gasparri, G. F.; Nardelli, M.; Sgarabotto, P. (1970). "Hydrogen bonding in thiosemicarbazide". Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry. 26 (7): 1005–1009. Bibcode:1970AcCrB..26.1005A. doi:10.1107/S0567740870003497. Gazieva, Galina A.; Kravchenko, Angelina N. (2012). "Thiosemicarbazides in the synthesis of five- and six-membered heterocyclic compounds". Russian Chemical Reviews. 81 (6): 494–523. Bibcode:2012RuCRv..81..494G. doi:10.1070/RC2012v081n06ABEH004235. S2CID 96691115. C. Ainsworth (1960). "1, 2, 4-Triazole". Organic Syntheses. 40: 99. doi:10.15227/orgsyn.040.0099.