Attempts to crystallize salts of thiocyameluric acid C₆N₇S₃H₃ and the crystal structure of the first hydrogen thiocyamelurate [Sr(H₂O)₆][HC₆N₇S₃].

Thiocyameluric acid C6N7S3H3 was reacted with various aqueous solutions of metal hydroxides and other metal salts, as well as ammonia. Crystalline products were obtained from reaction mixtures containing main group metal hydroxides. Only in the case of strontium hydroxide single crystals of Sr[HC6N7S3]·6H2O suitable for an X-ray structure analysis were formed. Similar to other cyamelurates containing anions like [C6N7O3]3–, [HC6N7O3]2– or [H2C6N7O3]–, or analogous melonates [C6N7(NCN)3]3–, the anion [HC6N7S3]2– in the title salt is completely planar. The hydrogen atom is located at a terminal N atom, which indicates that mono- and di-hydrogen thiocyamelurates and thiocyameluric acid preferably occur as thioketone tautomeric isomers, and are not encountered in the thiol form, at least in the solid state. Since all water molecules coordinate the strontium atoms and the anions do not act as ligands the salt may be described as [Sr(H2O)6][HC6N7S3]. [ABSTRACT FROM AUTHOR]