Heptanuclearity in nickel(II) chemistry: preparation, characterization, crystal structure and magnetic properties of [Ni 7(OH) 2(acac) 8(btaO) 4(H 2O) 2] (btaO −=the 1-hydroxybenzotriazolate ion)

Abstract

The use of the substituted benzotriazole ligand btaOH (1-hydroxybenzotriazole) in nickel(II) chemistry has yielded a structurally and magnetically interesting polynuclear complex. The [Ni(acac) 2(H 2O) 2]–btaOH·H 2O (4:1, 3:1, 7:4) reaction system in refluxing MeCN gives light green–blue [Ni 7(OH) 2(acac) 8(btaO) 4(H 2O) 2] ( 4) in good yield (∼75%). The structure of 4·MeCN·0.9H 2O was determined by single-crystal X-ray crystallography. The heptanuclear assembly is held together by two μ 3 hydroxo ligands, two terminal H 2O molecules, four chelating acac − groups, two μ 2 acac − groups, two μ 3 acac − groups, two μ 4 btaO − ligands and two μ 2 btaO − ligands. The Ni(II) atoms have distorted octahedral geometries. The IR and UV–Vis data of 4 are discussed in terms of the nature of bonding and the known structure. Variable-temperature magnetic susceptibility data (3–300 K), fitted with a 3- J model, show ferromagnetic and antiferromagnetic interactions. Magnetization data at 4 K are in line with an S=1 ground state for 4. The versatility of the 1-hydroxybenzotriazolate ligand is also discussed.