A new redox-active 4,5-bisguanidino-substituted o-benzoquinone ligand L is synthesized, which allows rational access to heterobinuclear complexes through the sequential coordination of two metals. In the examples discussed in this work, mononuclear Cu and Pd complexes are prepared in a first coordination step, and these complexes are then used as precursors to homobinuclear [Cu^II -L⁰ -Cu^II ] and heterobinuclear [Pd^II -L⁰ -Cu^II ] complexes. In the heterobinuclear complex, the Pd^II is coordinated by the softer bisguanidine side of L and the Cu^II by the harder dioxolene side (in line with the HSAB concept). The heterobinuclear complex is in a temperature-dependent equilibrium with its dimer, with two unsymmetrical Cu-Cl-Cu bridges. The redox-chemistry of the [Cu^II -L-Cu^II ] and [Pd^II -L-Cu^II ] complexes is studied. One-electron oxidation of both complexes was found to be quasi-reversible in CV experiments, and chemical one-electron oxidation was achieved with NO⁺ (SbF₆^- ). In the case of the homobinuclear complex [L(CuCl₂ )₂ ]⁺ , intramolecular ligand-metal electron-transfer, triggered by coordination of a CH₃ CN solvent molecule, leads to a temperature-dependent equilibrium between the form [Cu^II -L⁰ -Cu^III ] at low temperatures (with CH₃ CN coordinated to the Cu^III atom) and [Cu^II -L^⋅+ -Cu^II ] at higher temperatures (without CH₃ CN).

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