Formation of a dinuclear and a trinuclear Ni(II) complex on slight variation of experimental conditions: Structural analysis and magnetic properties

Abstract

A diphenoxido bridged dinuclear Ni(II) complex [Ni₂L₂ (NO₂)₂] (1) and a μ₂ and μ₃-phenoxido, μ₃-hydroxido and μ₂-nitrito (1kO:2kN) bridged trinuclear Ni(II) complex [Ni₃L₃(OH)(NO₂)]•ClO₄ (2), have been synthesized using a tridentate reduced Schiff base ligand HL (HL = 2-[(2-dimethylamino-ethylamino)-methyl]-phenol). Both complexes were characterized by X-ray structure determination and variable-temperature magnetic susceptibility measurements. In both complexes the nickel atoms are six-coordinated with a distorted octahedral environment. The interesting feature of the trimeric complex 2 is that the three mononuclear units are assembled around a μ₃-hydroxido ion in such a way that the three phenoxido groups and one nitrito group form a cyclic bridge that markedly modify the magnetic properties. Complex 1 presents a moderate antiferromagnetic Ni–Ni coupling (J = −39 cm⁻¹) through the phenoxido bridges with a wide Ni–O–Ni bond angle of 101.77(6)° whereas the lower Ni–O–Ni bond angles, in the range 86.66(6)–96.07(7)°, lead to a moderate ferromagnetic coupling (J = +18.2 cm⁻¹) in the trimeric complex 2 with a weak antiferromagnetic contribution (J′ = −0.51 cm⁻¹) via the 1kO:2kN nitrito bridge.