New Phenoxido-Bridged Quasi-Tetrahedral and Rhomboidal [Cu4] Compounds Bearing μ4-Oxido or μ1,1-Azido Ligands: Synthesis, Chemical Reactivity, and Magnetic Studies

[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]·2CH3OH (2·2CH3OH), and [Cu4(μ1,1-N3)4(μ-cip)2(N3)2]·DMF (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 Hamiltonian H = −2J{SCu,1·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).