A dicopper(II) complex with an unsymmetrical dicompartmental ligand containing bridging phenolic oxygen atoms was synthesized by stepwise condensation, in the presence of copper(II) ions, of 2,6-diformyl-4-methylphenol and diaminopropane, followed by hydroxylamine. The complex was isolated and characterized as Cl-, [Cu2Cl4](2-), and ClO4- derivatives. A byproduct of the reaction, a copper(II) complex with a substituted salycilaldoxime, was also structurally characterized. The structure of the binuclear cation of major interest is nearly planar, with the copper(II) ions slightly displaced to opposite sides of the plane of the donor atoms (<0.20 Angstrom). [Cu2Cl4](2-) is an unusual anion, having been characterized previously in only five other compounds. It is flat, with both copper(I) ions in trigonal planar environments and two chlorides bridging the two copper(I) centers. X-ray structure determinations of the [Cu2Cl4](2-) and ClO4- derivatives of the dicopper complex reveal a strong tendency for the formation of coordination dimers and tetramers. These aggregates arise because an oxime oxygen from one binuclear cationic complex coordinates axially to the copper atom of another such complex. In the case of the [CU2Cl4](2-) salt, the anion forms additional bridges between binuclear complexes,resulting in polymeric chains. In the ClO4- salt, however, aggregation is limited to the tetramer because of terminal axially coordinated methanol molecules. Temperature-dependent magnetic susceptibility measurements show strong antiferromagnetic interaction (ca. -700 cm(-1)) between the two copper(II) ions within one binuclear cationic complex. No magnetic interactions have been observed between binuclear units. Cyclic voltammograms were measured in dimethylformamide (DMF) solution and show two separate reduction waves at -1.47 and -1.04 V, as well as an oxidation wave at +0.04V (vs Fc(+)/Fc). The mixed-valent Cu-II/Cu-I complex is thermodynamically stable toward disproportionation.