Coordination geometries of bis(4-amino-3-alkyl-1,2,4-triazole-5-thione) complexes of first row transition metals: Crystal structures of the cobalt and nickel complexes of 4-amino-3-trifluoromethyl-1,2,4-triazole-5-thione

Bis bidentate complexes of 4-amino-3-trifluoromethyl-1,2,4-triazole-5-thione, SN₄C₃H₃F₃ (afmt, 1) of the divalent ions Co and Ni, have been crystallized by direct combination of the ligand and metal nitrate hydrate salt in ethanol. The structures of the free ligand 1 as well as the complexes were determined by single-crystal X-ray diffraction techniques. The triazole bonds to the metal ion through the amine and thione substituents on the five-membered ring. Two water molecules complete the octahedral coordination sphere. [Co(afmt)₂(H₂O)₂] (NO₃)₂ (2) and [Ni(afmt)₂(H₂O)₂] (NO₃)₂ (3) are essentially isostructural with a trans arrangement of all ligands. These structures are compared with those of four recently reported series of 4-amino-3-alkyl-1,2,4-triazole-5-thione complexes (alkyl = H, CH₃, C₂H₅, and C₃H₇) and it is found that the behavior of the CF₃-substituted ligand is most like that of the ethyl analog. Attempts to make complexes with other metals yielded crystals of the acid salt of the thiocarbohydrazide starting material. The crystal structure of thiocarbohydrazidium nitrate, [SN₄CH₇]NO₃ (4) has also been determined. The structure consists of layers of cations and anions in which the ammonium protons are hydrogen-bonded to the nitrate ions.