Synthesis, crystal structure and magnetic properties of bis[μ-bis(3-(pyridin-2-yl)-1,2,4-triazole- N′, N1, N2)] bis[triaqua nickel(II)] tetranitrate

• Published in: Inorganica Chimica Acta 1998-05, Vol.273 (1), p.54-61
• Main Authors: van Koningsbruggen, Petra J., Gluth, Matthias W., Ksenofontov, Vadim, Walcher, Dorothee, Schollmeyer, Dieter, Levchenko, Georg, Gütlich, Philipp
• Format: Article
• Language: English
• Subjects: Crystal structures; Dinuclear complexes; Magnetic properties; Nickel complexes; Triazole-bridged complexes
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(97)05914-8

A new dinuclear nickel(II) coordination compound of formula Ni 2(Hpt) 2(H 2O) 6(NO 3) 4 (Hpt=3-(pyridin-2-yl)-1,2,4-triazole) was synthesized. The structure was solved at 298 K by single-crystal X-ray analysis. Bisμ-bis(3-(pyridin-2-yl)-1,2,4-triazole- N′, N1, N2) bistriaqua nickel(II) tetranitrate (C 14H 24N 12O 18Ni 2) crystallizes in the triclinic space group P-1, a=7.2266(1), b=9.9144(1), c=11.2647(1) Å, α=66.854(1)°, β=74.000(1)°, γ=86.400(2)°, V=712.42(1) Å 3, Z=1 (dinuclear units), 2823 reflections ( 1 > 2 σ( I)), R1=0.0442, wR2=0.1197. The Ni(II) ions are bridged by two neutral Hpt ligands coordinating via N1 and N2 in the equatorial plane, Ni(1)-Ni(1)′=4.098(1) Å. The Hpt bridging mode is asymmetric (Ni(1)-N(1)′=2.074(2) Å, Ni(1)-N(2)=2.052(2) Å, N(1)-N(2)-Ni(1)=138.8(1)°, N(2)-N(1)-Ni(1)′=124.3(1)°). The octahedral environment around nickel(II) is completed by the coordinating pyridyl group (Ni(1)-N(31)=2.123(2) Å) and three coordinating water molecules (Ni(1)-O(1)=2.083(2) Å, Ni(1)-O(2)=2.053(2) Å, Ni(1)-O(3)=2.049(2) Å). The Ni(II) pairs are antiferromagnetically coupled, with J = −4.65 cm −1 (based on the spin Hamiltonian: H = −2 JS Ni1 · S Ni2). The J value was rationalized on the basis of the geometry around Ni(II). The superexchange pathway involves the σ orbitals of the N1, N2-diazine moiety of the bridging 1,2,4-triazole network. The nature and the magnitude of the antiferromagnetic exchange is discussed on the basis of the structural features.