Structures of new Cu(II) and Co(II) 4-amino-1,2,4-triazole coordination compounds

Abstract

The coordination chemistry of NH2trz (4-amino-1,2,4-triazole) has rapidly expanded due to the ability of this ligand to propagate elastic andmagnetic interactions between transitionmetal ions, which are of great appeal in molecular magnetism. New coordination compounds with NH2trz and dicyanamide (dca) bridging ligands, [Cu(NH2trz)4(H2O)](AsF6)2 1, [Cu(NH2trz)3] (ZrF6)cH2O 2, and [Co3(NH2trz)8(dca)4](dca)2c2H2O 3, have been prepared and structurally characterized. In the mononuclear complex 1, NH2trz is monodentate and is coordinated through a nitrogen atom of the triazole ring with bond lengths Cu-N = 1.997(6) 2.004(6) A. Complex 1 has a square-pyramidal geometry. The coordination sphere is supplemented by a water molecule in apical position, at 2.276(9) A from Cu(II). Themetal centers in 2 are connected by three bidentateN1,N21,2,4-triazole ligands. It is an infinite 1D chain with CucccCu = 3.8850(3) A. The second coordination sphere is occupied by one non-coordinated water molecule and a hexafluoro-zirconate anion, which is situated between the linear chains. The interchain distance is 10.997(4) A. The chains are connected by hydrogen bonds. There are two intermolecular interactions between fluorine and the non coordinated water molecule of the 1D chain. In 3, the octahedral surrounding around one of the two Co ions is formed by three bidentate N1,N2-1,2,4-triazole ligands, with distances 2.130(4) 2.142(4) A. The cobalt ions located in the extremity of this trinuclear unit have an octahedral environment with two μ1-dca molecules and monodentate NH2trz coordinated through a nitrogen atom of the ring. The temperature dependence of the magnetic susceptibility of the linear trimer 3 indicates the presence of antiferromagnetic interactions between the cobalt ions. m41.p08