Three nickel(II) complexes derived from a tridentate NNO donor Schiff base ligand: Syntheses, crystal structures and magnetic properties

Abstract

Three new Ni(II) complexes, [NiL(NO₂)(H₂O)] (1), [Ni₂L₂(PhCH₂COO)₂(H₂O)] (2) and [Ni₂L₂(N(CN)₂)₂(H₂O)] (3), have been synthesized using a tridentate Schiff base ligand, 1-[(3-dimethylamino-propylimino)-methyl]-naphthalen-2-ol (HL) and the polyatomic monoanions NO₂⁻, PhCH₂COO⁻ or N(CN)₂⁻. All three complexes (1–3) have been characterized by spectral analysis and X-ray crystallography. Structural analyses reveal that complex 1 is mononuclear, in which the Ni(II) ion is in a distorted octahedral environment, coordinated by the deprotonated tridentate Schiff base (L), a chelating nitrite and one water molecule. The structures of both 2 and 3 consist of dinuclear octahedral Ni(II) units with crystallographic C₂ symmetry. In complex 2, two μ₂-phenoxido and a water molecule bridge the two Ni(II) centers to make the complex a face sharing bioctahedron, whereas in 3 the Ni(II) atoms are bridged by two μ_1,5-dicyanamide ligands. Variable temperature magnetic susceptibility measurements show the presence of ferromagnetic coupling in complex 2 with J = +26.20 cm⁻¹ and antiferromagnetic coupling in complex 3 with J = −1.90 cm⁻¹.