NiII formate complexes with bi- and tridentate nitrogen-donor ligands: synthesis, characterization, and magnetic and thermal properties

The synthesis of four NiII formate complexes of the type [Ni(N∩N)n][O2CH]2 (2, adduct with 3/4 EtOH, N∩N = en, thyleediamine, n = 3; 4, N∩N = dien, N,N′,N′′-thyleetriamine, n = 2), [Ni2(O2CH)4(H2O)(tmeda)2] (3, tmeda = N,N,N′,N′-etraethylthyleneimine) and [{Ni(O2CH)2(pmdta)}2·H2O] (5, pmdta = N,N′,N′,N′′,N′′-entaethyliethylenerimine) by a reaction of [{Ni(O2CH)2}·2H2O] (1) with the respective N-donor bases is reported. The structures of 2–5 in the solid state were determined by single X-ray structure analysis, revealing a discrete dinuclear structure of 3 and the formation of polymeric networks in the case of 2, 4 and 5 due to intermolecular hydrogen bonding. SQUID and ESR measurements of 3 evidenced a weak antiferromagnetic coupling between the NiII ions and an easy plane magnetic anisotropy. Accompanying quantum chemical studies of the magnetic properties and IR characteristics of 3 were performed to strengthen the conclusions drawn from experimentally obtained data. The thermal decomposition temperatures of 2–5 were determined by TG (thermogravimetry) and obtained residues were analyzed by PXRD (powder X-ray diffraction) measurements. The decomposition processes were completed at 207 (3), 215 (5), 250 (2) and 273 °C (4) and are shown to result in the formation of pure metallic nickel.