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

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