A mixed-valent high spin (μ-hydroxo)dicobalt(II/III) complex and its end-on type dioxygen adduct: synthesis, geometric and electronic structure studies

A mixed-valent high spin (mu-hydroxo)dicobalt(II/III) complex bearing N, N '-bis(5-tertbutylsalicylidene)-1,2-diaminobenzene (Salophen(tBu)) ligand was synthesized by reacting (Salophen(tBu))Co(II)(Py) with O-2 at low temperature. This complex was isolated and structurally characterized by single crystal X-ray diffraction and infrared spectrum. Magnetic measurement showed a quartet ground state for this complex at room temperature, which was also supported by electron paramagnetic resonance (EPR) characterization. Computational investigations indicated the deviation of the equatorial N2O2 coordination geometry around the Co(II) center from plane stabilized the quartet state. The end-on type O-2 adduct of this (mu-hydroxo)dicobalt(II/III) complex was isolated as dark-brown crystals and structurally and spectroscopically characterized. EPR measurement of this compound in solid state at room temperature presented an isotropic singlet at g similar to 2, revealing the superoxide-like electronic feature of the coordinated O-2 and was in line with the calculation results. The reactivity of the Co(III)-O-2 complex with N-hydroxyphthalimide, which can act as hydrogen atom donor, was also examined.