Syntheses and Magnetic Properties of Ni(II) Dimers

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Dimeric Ni(II) carboxylates complexes, [Ni(RCOO)_8.L)]_2 (R=Me_3,Et_2CH,Me_2Phc, or MePh_2C; L=pyridine derivatives or tri-phenylphosphine), have been prepared and characterized by magnetic susceptibilities and X-ray structure analyses. All these complexes have subnormal magnetic moments (1.64-2.34 B.M.) at the room temperature. The complexes have the dimeric structure with four carboxylate bridges found in numerous copper(II) acetate adducts. The Ni atom has a slightly distorted square-pyramidal environment with four O atoms of the bridging carboxylates in the basal plane and an N or P atom in the axial position.Magnetic susceptibilities were determined in the temperature range 80-300 K by the Faraday method. The cryomagnetic data of the complexes were analyzed with Eq. (1), which is a modified expression of a channel model developed by Rakitin et al.,where Pi is mole fraction of each component, and other symbols have their usual meanings. The new parameter n is the number of unpaired electrons on a metal. Magnetic susceptibility data observed for the present complexes are well represented by Eq. (1) rather than by the Heisenberg model.