Syntheses, structures, and magnetic properties of tetranuclear Ni ₄^II and Ni₂^IIMn₂ ^III complexes with ONO tridentate ligands

Tetranuclear Ni₄^II and Ni₂ ^IIMn₂^III complexes of N-(2-hydroxymethylphenyl) salicylideneimine (H₂L1), [Ni₄Cl₂(L1) ₂(HL1)₂] (1), [Mn₂Ni₂Cl ₂(L1)₄(H₂O)₂] (2), and Ni(II) ₄ complex of N-(2-hydroxymethylphenyl)salicylamine (H₂L2), [Ni₄(L2)₄(CH₃OH)₂] (3) have been characterized by X-ray crystal structure analyses and magnetic measurements. The structure analyses revealed that complexes 1 and 2 have a defective double-cubane metal core connected by μ₃-alkoxo bridges. Complex 1 contains two types of tridentate ligands coordinating as dianionic (L1 ^2-) and monoanionic (HL1^-). The double-cubane core of 1 is significantly distorted due to an effect of chloride anions as bridging atoms. Complex 2 consists of two μ-phenoxo Ni^II-Mn^III heteronuclear units making a dimer-of-dimers structure. Complex 3 contains dianionic (L2)^2- ligands and forms Ni4II cubane core. Magnetic measurements of complex 2 indicate that a weak ferromagnetic interactions (J_NiMn = 1.5 cm^-1, J_NiNi = 20 cm^-1) are dominant in this hetero-metal core.