New Phenoxido-Bridged Quasi-Tetrahedral and Rhomboidal [Cu4] Compounds Bearing μ4-Oxido or μ1,1-Azido Ligands: Synthesis, Chemical Reactivity, and Magnetic Studies
Résumé
[Cu2(μ4-O)Cu2] and [Cu2(μ1,1-N3)4Cu2] geometrical arrangements are found in a new family of tetranuclear copper(II) complexes: [Cu4(μ4-O)(μ-cip)2Cl4] (1), [Cu4(μ4-O)- (μ-cip)2(μ1,3-O2CPh)4] 3 2CH3OH (2 3 2CH3OH), and [Cu4(μ1,1-N3)4(μ-cip)2(N3)2] 3DMF (3 3 DMF) [Hcip = 2,6- bis(cyclohexyliminomethylene)-4-methylphenol; CH3OH = methanol;DMF = dimethylformamide]. These complexes have been characterized by X-ray crystallography, and their magnetic properties have been studied. 1 and 2 form quasi-tetrahedral [Cu4(μ4-O)] complexes, and 3 is the first example of a rhomboidal [Cu4(μ1,1-N3)] compound. Formation of the [Cu4] compounds is achieved via ligand-exchange reactions. The relative binding strength of the three ancillary ligands as N3- > PhCO2- > Cl- has been demonstrated from the core-conversion and peripheral ligand-exchange reactions. For the three complexes, the magnetic susceptibility measurements in the range of 1.8-300 K have been performed and modeled using two isolated S = 1/2 dimers based on the spin HamiltonianH =-2J{SCu,1 3 SCu,2} with J/kB =-513,-340, and -315 K for 1-3, respectively (where J is the exchange constant through the oxido-phenoxido and azido-phenoxido bridges, respectively).