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New oximate-bridged tetranuclear nickel() complexes of compositions {Ni(Dien)} 2 (µ 3 -OH) 2 {Ni 2 (Moda) 5) and the dinuclear complex (Ni{Odien}) 2 -(Moda) 2 (ClO 4 ) 2 (6) have been prepared (Dien = 1,5-diamino-3-azapentane, Odien = 1,5-diamino-3-oxapentane, Sdien = 1,5-diamino-3-thiapentane, ModaH = butane-2,3-dione monooxime, InafH = phenylglyoxaldoxime). X-ray examination revealed similar structures for 1a, 1b, 1c, 2 and 3, with a rhombic "chair" (out-of-phase "butterfly") arrangement of the four nickel() atoms and two hydroxo-bridges. The complexes were examined by magnetochemistry, UV-VIS spectroscopy and voltammetry. 1-3 display antiferromagnetic coupling of the central with the terminal nickel() atoms and ferromagnetic spin alignment between the central nickel() atoms. In contrast, all the spin exchanges in 4 and 5 were found to be antiferromagnetic, as is the coupling in dinuclear 6.

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