Thiosemicarbazide
Thiosemicarbazide is the chemical compound with the formula H2NCNHNH2. A white, odorless solid, it is related to thiourea by the insertion of an NH center. They are commonly used as ligands for transition metals. 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 almost planar as are the three H atoms nearest the thiocarbonyl group. This can be explained by models of electron delocalisation.