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

[Cu-2(mu(4)-O)Cu-2] and [Cu-2(mu(1,1)-N-3)(4)Cu-2] geometrical arrangements are found in a new family of tetranuclear copper(II) complexes: [Cu-4(mu(4)-O)(mu-cip)(2)Cl-4] (1), [Cu-4(mu(4)-O)(mu-cip)(2)(mu 1,3O2CPh)(4)]center dot 2CH(3)OH (2 center dot 2CH(3)OH), and [Cu-4(mu(1,1)-N-3)(4)(mu-cip)(2)(N-3)(2)] center dot DMF (3 center dot 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 [Cu-4(mu(4)-O)] complexes, and 3 is the first example of a rhomboidal [Cu-4(mu(1,1)-N-3)] compound. Formation of the [Cu-4] compounds is achieved via ligand-exchange reactions. The relative binding strength of the three ancillary ligands as N-3(-) > 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{S-Cu,S-1 center dot S-Cu,S-2) with J/k(B) = -513, -340, and -315 K for 1-3, respectively (where J is the exchange constant through the oxido-phenoxido and azido-phenoxido bridges, respectively).