Bridging ability of a novel polydentate ligand (H2L) comprising an oxime function. Structures of a mononuclear precursor [NiL] and a dinuclear CuII2 complex. Magnetic properties of mononuclear (NiII and CuII), dinuclear (CuII2, NiII2, NiIICuII and CuIICrIII) and trinuclear (CuII3, CuIIMnIICuII and CuIIZnIICuII) complexes ‡

A novel non-symmetrical polydentate Schiff base ligand 3-({2-[(1-methyl-3-oxobut-1-enyl)amino]ethyl}imino)butan-2-one oxime (H2L) comprising an oxime function among various donor sites yields neutral [NiIIL] and [CuIIL] complexes. The structural determination of [NiL] confirms the deprotonation of the oxime function. The deprotonated oxime oxygen atom can react with auxiliary complexes to give homo- and hetero-di- and tri-nuclear entities. The structural determination of a homodinuclear copper complex clearly shows the presence of the expected oxime bridge, along with an unexpected ketonic bridge between the two copper centres leading to a Cu[O,NO]Cu core. A moderate antiferromagnetic interaction is present in the di- and tri-nuclear copper complexes. A similar interaction is also observed in the heteronuclear complexes (CuIINiII and CuIIMnII) and, more surprisingly, in the heterodinuclear CuIICrIII entity. A generalization of the Cu[O,NO]Cu structure leads to a justification of these magnetic properties.