Reaction of a dicopper(I) acetonitrile complex (1) with elemental sulfur resulted in a formally 2CuI:2CuII tetracopper mixed-valent μ-disulfide complex (2). Stoichiometric reduction (with cobaltocene) or oxidation (with AgNTf2, NTf2 = bis(trifluoromethane)sulfonimide) result in reversible interconversions between complex 2, a formally 3CuI:CuII species (3), and a 4CuI species (4). Given the isostructural nature of these complexes, the electronic communication between the metal centers of 2, 3, and 4 were spectroscopically investigated with UV-vis and EPR techniques, revealing the relative delocalization of electron holes on all four copper centers of 2 and 3. Variable temperature magnetometry of 2, 3, and 4 also reveal antiferromagnetic, ferromagnetic, and temperature-independent paramagnetic behavior, respectively. The formally spin-paired (d10)4 complex 4 displays unusual magnetic behavior, exhibiting field-induced paramagnetism.
See et al. (Tue,) studied this question.