Structural trends in a series of divalent transition metal triazole complexes

A series of bis bidentate complexes of 4-amino-3-methyl-1,2,4-triazole-5-th ione SN4C3H6 (amt), with the divalent ions Mn, Fe, Co, Cu, and Zn have been crystallized by direct combination of the ligand and metal nitrate or perc hlorate hydrate salt in ethanol. The structures were determined by single c rystal X-ray diffraction techniques. In all cases, the triazole coordinates through the amine and thione substituents on the five-membered ring. The i sostructural compounds [Mn(amt)(2)(H2O)(2)](ClO4)(2) (1) and [Fe(amt)(2)(H2 O)(2)](ClO4)(2) (2) have the triazole and water ligands in a trans arrangem ent. The octahedral coordination shows a tetragonal distortion as the M-N b onds are 0.15 Angstrom longer than the M-O bonds. The nitrate salts [Mn(amt )(2)(H2O)(2)](NO3)(2) (3), [Co(amt)(2)(H2O)(2)](NO3)(2) (4), and [Zn(amt)(2 )(H2O)(2)](NO3)(2) (5), are also isostructural, but have the water molecule s cis to each other and the triazoles arranged so that the amine groups are cis while the thiones are trans. The nitrate salt of the copper(II) comple x, [Cu(amt)(2)(H2O)(2)](NO3)(2) (6), is similar in structure to 1 and 2; ho wever, it is the water molecules which are more distant in the Jahn-Teller distorted coordination sphere; When sulfate is used in place of nitrate, a square pyramidal complex [Cu(amt)(2)(SO4)]. 2H(2)O (7) is obtained in which two pseudo-inverted triazole ligands form the base while the apex is a mon odentate sulfate ligand. Neither water molecule is coordinated to the metal in this compound. These results are discussed in terms of the coordination behavior of the triazole ligand in these and similar systems. (C) 1999 Els evier Science S.A. All rights reserved.