Synthesis and Magnetic Properties of Cobalt(II)-Palladium(II)-Cobalt(II) Trinuclear Complexes Bridged by an Extended α-Benzyldioximato Group

Abstract

Three new hetero-trinuclear complexes with an extended bridging dioximate group of the formula [CoL₂-Pd(α-BD)₂-CoL₂](ClO₄)₂ (L = 1,10-phenanthroline (phen), 5-NO₂-1,10-phenanthroline (NO-phen), 2,2′-bipyridyl (bpy) and (α-BD)^2- = α-benzyldioximato) have been synthesized and characterized. Based on IR, elemental analyses, conductivety measurements and electronic spectra, these complexes are proposed to have a dioximate bridgedstructure consisting of two terminal cobalt(II) ions and a center palladium(II) ion in which the two terminal cobalt(II) ions have a distorted octahedral environment and the center palladium(II) ion has a square-planar environment. The temperature dependence of the magnetic susceptibility of [CoL₂-Pd(α-BD)₂-CoL₂](ClO₄)₂ (L = phen) (1) has been studied in the 4.2–300 K range, resulting in the exchange integral J = −1.91 cm⁻¹. This result reveals the operation of antiferromagnetic spin-exchange interaction between the two terminal cobalt(II) ions through the dioximate bridges, it correspond to what is expected for antiferromagnetic Co^II-Co^II pairs with S_Co = 3/2, S_Pd = 0 (Pd²⁺ is a diamagnetic with a square-planar environment) local spins.