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-thio ne, SN4C3H3F3 (afmt, 1) of the divalent ions Co and Ni, have been crystalli zed by direct combination of the ligand and metal nitrate hydrate salt in e thanol. The structures of the free ligand 1 as well as the complexes were d etermined by single-crystal X-ray diffraction techniques. The triazole bond s to the metal ion through the amine and thione substituents on the five-me mbered ring. Two water molecules complete the octahedral coordination spher e. [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. Thes e 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 mo st like that of the ethyl analog. Attempts to make complexes with other met als yielded crystals of the acid salt of the thiocarbohydrazide starting ma terial. The crystal structure of thiocarbohydrazidium nitrate, [SN4CH7]NO3 (4) has also been determined. The structure consists of layers of cations a nd anions in which the ammonium protons are hydrogen-bonded to the nitrate ions. (C) 2001 Elsevier Science B.V. All rights reserved.